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UNIT - I

LESSON 1 – IMPORTANCE OF ATMOSPHERE Contents 1.0 Aims and objectives

1.1. Introduction 1.1.1. Importance of atmosphere

1.2. Composition of atmosphere 1.2.1. Importance of atmospheric gases and other constituents 1.2.2. Role of carbon dioxide in atmosphere 1.2.3. Role of other constituents

1.3. Structure of atmosphere 1.3.1. Layers of atmosphere based on composition of constituents 1.3.2. Layers of atmosphere based on temperature variation

1.4. Let us sum up 1.5. Lesson-end Activities 1.6. Points for Discussion 1.7. Check your Progress 1.8. References

LESSON 1 – IMPORTANCE OF ATMOSPHERE

1. 0 AIMS AND OBJECTIVES

The aim of this lesson is to know the importance of atmosphere it, its properties and structures:

· What is atmosphere? · What is it made of? · What is its composition? · To what height atmosphere does extend? · Is atmosphere uniform throughout? Or does it have different layers?

1.1 INTRODUCTION

The earth is the only known planet, on which life exists. The present condition and properties of earth’s atmosphere are one of the main reasons for earth to support life. First of all, we should know, what is atmosphere? Atmosphere is a gaseous layer surrounding the earth. In other words, we can say that our earth is surrounded by a thin layer of gases, called atmosphere. Yes, it is thin when compared to the size of the earth. Yet, this thin layer has its own influences on various processes that take place on earth. It contains a mixture of gases with some impurities.

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The atmosphere is special because it contains life-sustaining oxygen in large quantities (about 21% by volume). In fact, it took millions of years to reach the present condition by various processes. Along with its development, life came into existence and evolved.

The aim of this material is that at the end, you will be amazed to know how perfectly, all the natural processes on earth are functioning harmoniously. In fact, the processes of the atmosphere do not take place in isolation. Atmosphere constantly exchange energy and matter with other components of the earth – lithosphere, hydrosphere and biosphere.

Hereafter, the term, atmosphere is used for earth’s atmosphere. Atmosphere extends from a few meters below the earth’s surfaces or water’s surface to a height of about 60,000 km. However, about 90% of the atmosphere is within few km from the ground. Most of the mass of the atmosphere is near planetary surface, as the gravity pulls them towards the earth’s center.

1.1.1 IMPORTANCE OF ATMOSPHERE

Atmosphere is very important to sustain life on earth. It contains life-supporting oxygen in sufficiently large quantities. Constant concentration of oxygen is maintained through oxygen cycle. The oxygen cycle does not take place in isolation but It takes place along with other bio-geo chemical cycles. These cycles connect the atmosphere with hydrosphere, lithosphere and biosphere. It is send that the atmosphere does not function by itself, but it functions in conformity with other spheres on earth.

Atmosphere is the transparent layer through which, life-sustaining solar radiation passes and reaches the earth’s surface or into the water. It is awonder, why solar radiation is mentioned as “life-sustaining” one. It is mentioned so, because, solar radiation is the only source to supply energy for photosynthesis to take place on earth, which thereby supports all other life.

When solar radiation passes through the atmosphere, happen. Harmful ultra violet radiation was “absorbed” by ozone layer, which is a part of our atmosphere. Ozone layer prevents about 95% of harmful ultra-violet radiation from reaching the earth’s surface. Solar radiation when it passes through the troposphere, the lowest layer of the a atmosphere, part of the radiation, may be reflected back by the clouds, scattered by atmospheric constituents, thereby reducing visibility, absorbed by atmospheric constituents and the remainder reach the earth’s surface (land or water).

Heated earth emits the energy in the form of infra red radiation during nighttime and this radiation is absorbed by carbon dioxide, water and few other gases. This process results in “green house effect”. Thus, the atmosphere is kept warm during night, it will become so cool and intolerable for living organisms.

Earth is not heated by solar radiation uniformly due to its inclination. As a result, different weather patterns exist over the earth. In order to compensate these differences, air sets in motion resulting in winds and circulation of air. These wind currents are of global



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scale as well as of local scale. They are responsible for disastrous storms like cyclones, dust storms, tornadoes etc. These wind currents also influence water currents in the oceans; they in turn affect the wind currents. Consequently, understanding the atmosphere and its functions and behavior is quite complex. However, with available knowledge, scientists try to comprehend to the extent possible.

Thus, understanding of the atmosphere has become very essential and important. All the above processes make the atmosphere, a dynamic atmosphere. In forthcoming sections, we shall learn more about this life-sustaining sphere, atmosphere. In fact, you will be fascinated to know about the atmosphere. Self-check Exercise 1

State two reasons why we should know about our atmosphere?

Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

1.2. COMPOSITION OF ATMOSPHERE

The comportion of the atmosphere are gases present in large amounts, water vapor and solid particles in considerably less amounts. Gases that in the atmosphere are divided into two kinds, based on their concentration, viz., constant gases and variable gases.

Constant gases are the ones, whose concentrations do not change over time, and their concentrations almost remain same. But, variable gases are present in different concentrations at different places and times.

Nitrogen and oxygen are the two major constant gases that make up 99 percent of the air. Both are important to sustain life on earth. Nitrogen constitutes 78.09% and oxygen 20.94 percent by volume thus, making the bulk of the atmosphere. The remaining 0.97% is constituted by nitrous oxide and inert gases such as, argon, helium, krypton, xenon and also by variable gases – carbon dioxide, water vapor and ozone. Self-check Exercise 2

1. What are the two major constituents of the atmosphere? Name them with their

average proportions. 2. Distinguish between constant gases and variable gases.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………



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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 1.2.1 IMPORTANCE OF ATMOSPHERIC GASES AND OTHER

CONSTITUENTS As such, nitrogen in its gaseous form in the atmosphere is not that important. It is

non-poisonous. But, indirectly, it is very important, as it is converted into useful forms for life by certain micro organisms. Nitrogen is very important in the formation of amino acids, which are building blocks of proteins, and also in the formation of nucleotides, which are part of the genetic materials, viz., DNA and RNA. This is one of the best examples that the natural processes are in perfect harmony with each other.

It is needless to stress the importance of oxygen. Every living organism, including humans, need oxygen for respiration. Respiration is the process through which the chemical energy (food) is converted into usable form of energy by the living cells.

Inert gases, as such do not play any role in the environment. However, they are used for commercial purposes such as in neon lights.

1.2.2 ROLE OF CARBON DIOXIDE IN ATMOSPHERE

Carbon dioxide is emitted by all living organisms as an end product of respiration. This carbon dioxide, in turn is used by producer organisms (green plants and certain micro organisms) for the synthesis of food. This process is called, photosynthesis. This is another example how natural processes are inter-related and inter-dependant. As a large amount of carbon dioxide is utilized by plants, on average, it comprises only 0.04 percent of dry air. Nevertheless, it plays significant role in keeping the atmosphere at temperatures that permit life.

The concentration of carbon dioxide, nowadays, is increasing due to human activities. Today, man burns large quantities of fossil fuels for various purposes. As a result, huge amounts of carbon dioxide are emitted into the atmosphere. Its ever increasing concentration has already resulted in global warming and in some places, melting of ice.

Water vapor, though present in small quantities, plays a crucial role. It i s responsible for cloud formation in the atmosphere and precipitation. Its concentration varies over time at a given place and at different places. It is an important component of the atmosphere in determining the weather of a place at a given time. It is responsible for fog formation during early morning hours in winter, for feeling sultry near coastal regions, during summer.

Water vapor also absorbs outgoing radiation from earth as CO2 does and it has a crucial role in green house effect. Thus, both CO2 and H2O along with ozone (in troposphere), methane and N2O are called, green house gases.



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1.2.3 ROLE OF OTHER CONSTITUENTS

In addition, water present in clouds, can reflect and absorb the part of the incoming solar radiation. It also determines the weather of a place at a given time to a large extent. Water vapor is also transported along with the wind and its circulation. As a result, it is distributed to the parts away from sea. Nevertheless, the places that are far away from sea will have less moisture content than the places near the sea.

Other variable gases are also present in the atmosphere but in minute quantities. They are hydrogen, helium, sulfur dioxide, methane, carbon monoxide and oxides of nitrogen. Some of them are air pollutants, emitted by human activities.

Solid particles are present in minute quantities in the atmosphere. They might have originated either naturally or by human activities or both. In acceptable quantities, they are beneficial as they initiate and take part in cloud formation. The solid particles absorb and scatter the solar radiation. When their concentration goes high, they reduce the visibility of the atmosphere and are deleterious to human health. They also affect other living organisms in many ways.

Table 1.1 – Constituents of atmosphere

Gas Average percentage

(by volume in dry air)

Nitrogen 78.09

Oxygen 20.94

Argon 0.9

Carbon dioxide 0.03

Neon 0.002

Helium 0.0005

Methane 0.0002

Krypton 0.0001

Hydrogen 0.00005

Nitrous oxide (N2O) 0.00005



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1.3 STRUCTURE OF ATMOSPHERE

The earth is surrounded by a thin layer of air, called, atmosphere. The atmosphere, from the surface of earth extends up to 60,000 km. You may wonder how such a thickness would be called a thin layer. Where, most of the mass of the atmosphere is found near the planetary surface. It is near the earths surface from surface to about 80 to 100 km. This is due to the earth’s gravity, which pulls the atmospheric constituents, towards its center. As a result, the most of the atmosphere are within this thickness.

1.3.1 LAYERS OF ATMOSPHERE BASED ON COMPOSITON OF CONSTITUENTS

It is the thin layer, in which most of the atmospheric processes take place. According

to the concentration of the gases, atmosphere is divided into: 1. Homosphere: the lower region, extending from the surface of the earth to a height

of 80 to 100 km above the earth. In this layer, gases are more or less uniform in their chemical composition.

2. Heterosphere: it starts from the upper portion of homosphere and extends to height of 60,000 km above the earth. In this layer, chemical composition changes with height. Concentration of gases keep decreasing as one goes up. Inter molecular distance increases with height and hence, concentration decreases.

Self-check Exercise 3

Distinguish between homosphere and Heterosphere. Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 1.3.2 LAYERS OF ATMOSPHERE BASED ON TEMPERATURE

VARIATION Atmosphere again can be divided into four distinct layers according to their temperature characteristics:

1. Troposphere: it is the bottom layer of the atmosphere. It contains 70% mass of the atmosphere. It extends to an average height of 12 km. However, its thickness varies with latitude: over the poles, only about 8 km; above the equator, it is about 16 km. A very important feature of this layer is that temperature decreases with height in this layer. The rate of decrease of temperature with altitude is called, lapse rate. Average lapse rate in troposphere is -6.4 °C / km. Troposphere ends at tropopause. Tropopause is just like a lid over the troposphere, where temperature stops decreasing with height.



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2. Stratosphere: it lies just above the tropopause. It extends to a height of 50 km from earth’s surface. Ozonosphere, a very important layer is found within this stratosphere. Ozone present in the ozonosphere prevents the harmful ultra-violet rays from reaching the earth, thereby protecting the life. Thus, ozonosphere acts as a protective umbrella.

Stratosphere is a calm layer consisting of relatively clean air. Water vapor in this layer is almost absent, and hence clouds will not form in this layer. In this layer, temperature increases with height; just opposite to that in troposphere. This temperature increase with height prevents the vertical winds. Only horizontal winds are seen. These horizontal winds flow almost always parallel to the earth’s surface. Absence of vertical winds and the existence of horizontal winds parallel to earth’s surface result in relatively calm atmosphere (absence of turbulence). This ensures smooth travel for fights. Absence of clouds also provide with good visibility for pilots. All the above features led to the operation of jet air planes in this layer. The flying of jet air planes was partly responsible for the destruction of ozone. The detail account on ozone layer depletion will be discussed in the forthcoming sections. Above the stratosphere, temperature neither decreases nor increases with height up to some level. This small layer is called, stratopause.

3. Mesosphere: it starts from the edge of the stratopause, just at an approximate height of 52 km from earth’s surface. It extends to height of 80 km from the ground. In this layer, temperature decreases with height as in troposphere. This layer, as such does not have any impact on life. But, it gains importance as it plays crucial role in radio communication. How does it exhibit its influence? Sunlight passing through this layer, converts the individual molecules to individual charged ions i.e. ionization. Ionized particles are concentrated as a zone called the D-layer. This D-layer reflects radio waves sent from earth. But this D-layer blocks the communications between earth and astronauts. In this layer, during summer, at night times, a spectacular display of wispy clouds can be seen sometimes over high latitudes. It is presumed that meteoric dust particles coated with ice crystals reflect the sunlight resulting in wispy clouds. Just above the mesosphere lies, mesopause, in which temperature neither decreases nor increases.

4. Thermosphere: it is found approximately above 80 km from earth’s surface. It extends to the edge of space at about 60,000 km from earth’s surface. Temperature keeps rising with altitude in this layer. It is likely to reach 900 °C at an altitude of 350 km. However, these high temperatures are not felt as in lower layers. The air molecules are so far apart in this layer. As a result, these temperatures really apply to individual molecules only. In this layer too, ionization of molecules take place. It results in individual charged ions. This process produces two ionized belts, viz., E- and F-layers. These layers also reflect radio waves and have influence over radio communications. In the upper thermosphere, further concentration of ions are seen that comprise the Van Allen radiation belts. This layer is sometimes called, magnetosphere. It is thus called as earth’s magnetic field has more influence over the movement of particles rather than earth’s gravitational field. Thermosphere as such has no definable upper boundary and gradually blends with space.



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What is the significant of troposphere? Explain briefly. Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Figure 1.1 – Vertical temperature variation of the atmosphere and its layers 1.4 LET US SUM UP In this lesson, the following concepts are

· the importance of atmosphere · what makes it important



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· why it is important · the composition of atmosphere · the structure of atmosphere – layers based on its composition and layers based

on temperature variation By now, the importance of the atmosphere in sustaining life was understood atmosphere plays many significant roles in maintaining the temperature of a particular place. Atmosphere, as it exists, provide suitable conditions for life of a place. It determines the life forms available at a particular place. 1.5 LESSON-END ACTIVITIES

· Take a sheet of paper and write down points that come to your mind about the importance of our atmosphere

· Write what will happen if carbon dioxide constituted 21% of atmosphere · Write down how the temperature varies with increasing altitude

1.6 POINTS FOR DISCUSSION Now you are well aware that our atmosphere sustains the life. The composition of atmosphere makes it possible to support life. Carbon dioxide plays a vital role in keeing the earth warm. The temperature variation vertically, also we learned. 1.7 CHECK YOUR PROGRESS

· Can you state the major constituent of the atmosphere and its percentage? · Can you divide the atmosphere into layers according to temperature variation with

approximate height of each layer? · Will you be able to describe the properties of troposphere?

1.8 REFERENCES

1. De Blij, H.J. and Muller, P.O. Physical geography of the global environment, John Wiley & Sons, Inc., New York

2. Miller, Jr., G.T. Environmental Science, Thomson Brroks/Cole, CA, USA, 2004 3. De, A.K. Environmental Chemistry, New Age International Ltd, Publishers, New

Delhi, 1994 4. Rao, M.N. and Rao, H.V.N. Air pollution, Tata McGraw-Hill Publishing Co. Ltd.,

New Delhi 5. Stern, A.C. Air pollution, Academic Press, Inc., New York, 1976 6. Wark, K. and Warner, C.F. Air pollution – its origin and control, IEP A Dun-

Donnelly Publisher, New York, 1976 7. W.H.O. Glossary of air pollution, World Health Organization, Copenhagen, 1980 8. www.en.wikipedia.com 9. Critchfield, H.J. General climatology, Prentice Hall of India Pvt. Ltd., New Delhi,

1987



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LESSON 2 – ELEMENTAL PROPERTIES OF ATMOSPHERE Contents 1.0 Aims and objectives

1.1. Elemental properties of atmosphere 1.2. Chemical and photochemical reactions

1.2.1. Photochemical reactions n ozone layer 1.3. Ozone layer depletion

1.3.1. Ozone layer depletion by CFCs 1.3.2. Ozone layer depletion by nitric oxide


2.0 AIMS AND OBJECTIVES In the previous lesson, we have learnt the atmosphere, its importance, its composition and its structure. In this lesson, we will be learning about the properties of atmosphere. In fact, the atmosphere is not a static gaseous medium; it is rather a dynamic fluid in which many physical and chemical processes take place throughout.

· About chemical properties of the atmosphere · Reactions taking place in the atmosphere. · How ozone layer is depleted by some of the chemical reactions

2.1 ELEMENTAL PROPERTIES OF ATMOSPHERE In the preceding section, importance of atmosphere, its temperature profile with increasing altitude and its constituents. In this lesson, we will learn the chemical properties of atmosphere and various chemical reactions taking place in it. 2.2 . CHEMICAL AND PHOTOCHEMICAL REACTIONS As it is mentioned earlier, atmosphere is dynamic. Many chemical and physical processes are taking place in the atmosphere. Some of them occur naturally while others occur due to man’s interventions. Atmosphere is a gaseous medium and is very large in size when compared to any man-made reaction chamber for the reactions to take place. Now let us see something about chemical and photochemical reactions that occur in atmosphere. First, we shall learn the reactions occurring in ozonosphere. These reactions help in maintaining the concentration of ozone at this altitude. Then we shall move on to learn some of the reactions occurring in troposphere and the chemical reactions taking place in troposphere and stratosphere.



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2.2.1. PHOTOCHEMICAL REACTIONS IN OZONE LAYER The existence of ozone layer was discovered by the French Physicists, Charles Fabry and Henri Buisson in 1913. It is located in the lower part of the stratosphere approximately between the altitudes of 15 and 35 km. Concentration of ozone at its maximum is 10 ppm at an altitude of 25-30 km. Between the altitudes of 15 and 40 km, its concentration ranges from 2 to 8 ppm. Concentration of ozone is maintained at their levels in the above altitudes by “ozone-oxygen” cycle. Photochemical mechanisms in ozone-oxygen cycle were studied by the British Physicist, Sidney Chapman in 1930.

When ultra-violet radiation strikes the oxygen molecule, O2, it splits the molecule into two individual oxygen atoms (O and O). The reactions and wavelengths of the ultra violet radiation in which the reactions take place are described below: The atomic oxygen thus produced will combine with un-split oxygen molecule (O2) to produce ozone molecule (O3) once again. In this reaction a third body, M plays a crucial role in absorbing the excess energy liberated. This M may be a N2 or another O2. Thus formed ozone will be split by striking ultra-violet radiation at the wavelength around 308 nm into a molecule of O2 and an atom of oxygen.

By this ozone-oxygen cycle, the concentration of ozone is maintained. The actual concentration of ozone is determined by the rate of its formation and its destruction.

Due to photochemical dissociation by ultra-violet radiation, other forms of oxygen are also present in stratosphere: O+, O• and O •

2 – ionic form and excited form. These reactions are as shown below:

They are also part of the ozone-oxygen cycle. This entire cycle is presented in figure 2.1. The amount of ozone present in the stratosphere is measured by simple spectrophotometer from the ground. This instrument was developed by the British meteorologist, G.M.B. Dobson who explored the properties of ozone layer in detail. Total amount of ozone in a column overhead is measured and expressed in “Dobson units” named in honor of G.M.B. Dobson.

308 nm

– 260 nm

O3 + hν O• + O2

– 260 nm

O + hν O+ + e

– 260 nm

O2 + hν O2+ + e

– 260 nm

O2 + hν 242 nm O + O

– 260 nm

O + O2 + M (N2 or O2) O3 + M

240 – 260 nm O2 + hν O + O

O2 + hν O + O 135 – 176 nm



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Self-check Exercise 5 1. In what layer does ozone layer exist? 2. Between what altitudes is the ozone layer present? 3. What is the significant role of ozone layer? State briefly.

Note: Please do not proceed unless you write answers for the above two in the space given below: …………………………………………………………………………………………………………………………………………………………………………………………………..………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………………………… 2.3. OZONE LAYER DEPLETION

Today, due to human activities, this ozone layer is becoming thin. This thinning is called, ozone depletion. At the zones, where thinning is too severe, they are termed as “Ozone holes”. The ozone hole is defined as the area having less than 220 Dobson units (DU) of ozone in the overhead column (i.e., between the ground and space). Ozone hole, observed over Antarctic region is shown in figure 2.2.

Mechanism of ozone depletion is not well understood. Chloro-fluoro carbons (CFC) used in refrigerators, air conditioners, propellants etc. and oxides of nitrogen emitted by air crafts flying near stratosphere are found to be the causes for ozone layer depletion. Ozone layer is depleted by free radical catalysts – nitric oxide (NO), hydroxyl (OH),

Figure 2.1 - Ozone-oxygen cycle (Source:Wikipedia)



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atomic chlorine (Cl), and atomic bromine (Br). Halogens have the ability to catalyze ozone breakdown.

A catalyst is a compound which can alter the rate of a reaction without permanently

being altered by that reaction and so can react over and over again. Chlorine atom or any other halogen atom released from CFC or BFC by striking ultraviolet radiation is now available for catalyzing ozone breakdown. Although these species occur naturally, large amounts are released by human activities through the use of CFCs and bromofluoro carbons. 2.3.1 OZONE LAYER DEPLETION BY CFCs

CFCs and BFCs are stable compounds and live long in the atmosphere. As the live longer they are able to rise to the stratosphere. Cl and Br radicals are liberated from these compounds by the action of ultraviolet radiation. These radicals initiate and catalyze breaking the ozone molecules. One single radical is capable of breaking down over 100,000 ozone molecules. Ozone concentration is decreasing at the rate of 4% per decade over northern hemisphere. CFCs have long life time – 50 to 100 years. As they remain for such a long duration, they deplete ozone layer continuously. Moreover, this depletion rate keep increasing as more and more CFCs are released.

Figure 2.2 – Ozone hole over Antarctic region (Source: www.research.noaa.gov/climate/t_ozonelayer.html)



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Ozone depletion is by chlorine atom is illustrated in figure 2.3. The chemical reactions that lead to destruction of O3 by CFCl3 are shown below. Similar reactions take place with other CFCs and BFCs.

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CFCl3 + hn CFCl2 + Cl•

Cl• + O3 ClO• + O2

ClO• + O Cl• + O2

In a cyclic reaction, each ClO• can initiate a series of chemical reactions which lead to destruction of about 100,000 molecules of ozone!!

200 nm

After realizing the seriousness of this problem, countries have come forward to ban completely or phase out and the ban the use of CFCs. Sweden was the first nation to ban CFC-containing aerosol sprays. The ban was brought to force on January 23, 1978 in Sweden. Few other countries followed Sweden later that year. Ozone hole was discovered in the year 1985. After this, countries came forward for an international treaty, the Montreal Protocol for complete phase-out of CFCs by 1996. This effort has yielded positive result. Scientists announced on August 2, 2003 that depletion of ozone layer had slowed down due to the ban on CFCs.

Scientists have developed HCFC to replace CFC for the same purpose. These HCFCs are short-lived in the atmosphere to reach the stratosphere and damage ozone layer.

Figure 2.3 – Chemistry of ozone depletion



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2.3.2 OZONE LAYER DEPLTION BY NITRIC OXIDE

Chemistry of ozone depletion by nitric oxide is shown below:


O3 + NO NO2 + O2

NO2 + O3 NO3 + O2

NO3 + NO2 N2O5

O + NO2 NO3

NO + NO3 2 NO2

O + NO NO2

M

M

When a nitric oxide (NO) molecule combines with O3, it is oxidized to nitrogen dioxide (NO2). This NO2 now combines with another O3 molecule to become NO3 and O2. Both NO2 and NO3 may combine to form N2O5. Even if atomic oxygen is available, it readily combines with NO2 to yield NO3. Thus, O3 is completely utilized for the above reactions and thereby depleted. International community, after realizing its seriousness, has agreed to withdraw the operation of jet airplanes that emit NO in stratosphere. Self-check Exercise 6

Write the chemical reactions involved in ozone layer depletion by a) CFCs b) NO


2.4 LET US SUM UP In this lesson we have learnt the elemental properties of atmosphere. We studied, in depth, the photochemical reactions taking place in ozone layer and learnt how these reactions protect the earth from harmful ultraviolet radiation. We also learnt how these reactions are interrupted by CFCs and other chemicals which lead to depletion of ozone layer. We shall learn more in Unit 2 about this.



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2.5 LESSON-END ACTIVITIES

· Take a sheet of paper, and write the sequence of photochemical reactions taking place in the upper atmosphere

· Write the wavelength regions of ultra-violet radiation absorption by O3 and O2

2.6 POINTS FOR DISCUSSION You are now aware that the natural protection available in the stratosphere. It protects us from harmful ultraviolet radiation. Man, by his activities releases CFCs into the atmosphere and other gases that deplete the ozone layer. 2.7 CHECK YOUR PROGRESS

· Can you write ozone-oxygen cycle on a sheet of paper? · Can you write down the reactions of ozone depletion by CFCs and NO?

2.8 REFERENCES

1. de Blij, H.J. and Muller, P.O. Physical geography of the global environment, John Wiley & Sons, Inc., New York

2. Miller, Jr., G.T. Environmental Science, Thomson Brroks/Cole, CA, USA, 2004

3. De, A.K. Environmental Chemistry, New Age International Ltd, Publishers, New Delhi, 1994

4. Rao, M.N. and Rao, H.V.N. Air pollution, Tata McGraw-Hill Publishing Co. Ltd., New Delhi

5. Stern, A.C. Air pollution, Academic Press, Inc., New York, 1976 6. Wark, K. and Warner, C.F. Air pollution – its origin and control, IEP A

Dun-Donnelly Publisher, New York, 1976 7. W.H.O. Glossary of air pollution, World Health Organization, Copenhagen,

1980 8. www.en.wikipedia.com 9. Critchfield, H.J. General climatology, Prentice Hall of India Pvt. Ltd., New

Delhi, 1987



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LESSON 3 – METEOROLOGY Contents 3.0 Aims and objectives

3.1. What is meteorology? 3.2. Incoming solar radiation – insolation

3.2.1. Radiation balance 3.2.2. Earth’s outgoing radiation 3.2.3. Green house effect

3.3. Weather 3.3.1. Temperature 3.3.2. Altitudinal temperature distribution 3.3.3. Horizontal temperature distribution 3.3.4. Atmospheric temperature measurements 3.3.5. Humidity 3.3.6. Measurement of humidity 3.3.7. Phases of water in atmosphere 3.3.8. Precipitation 3.3.9. Pressure 3.3.10. Measurement of atmospheric pressure


3.0 AIMS AND OBJECTIVES In the preceding lessons we have learnt the importance of atmosphere, its composition, its structure, its properties and reactions taking place in it. We also learnt how the protective ozone layer is depleted by some chemicals. In this lesson various physical processes and phenomena occurring in the atmosphere. It will be interesting to note the influence of incoming solar radiation in driving various processes in atmosphere. The study of temperature, its variation spatially and temporally. Other parameters like pressure, humidity, wind, and precipitation will also be discussed. By the end of the lesson, the learner will know all the above in details to a greater extent.

3.1 WHAT IS METEOROLOGY? In this lesson, you will be learning about physical processes taking place in the atmosphere, especially in troposphere. These physical processes are responsible for



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weather and climate of a place. All the processes are studied as a branch of science called, meteorology. Meteorology is the science of atmosphere and deals with basic physical principles as they apply to atmospheric phenomena. When it is said atmosphere, it may represent atmosphere of not only earth but also of other planets. The study of “science of earth’s atmosphere” is called metrology. The atmosphere behaves like a mega heat engine, in which many interesting processes like movement of air, storms, cyclones, formation of clouds and precipitation etc. take place. Major driving force for this “engine” is solar radiation. Incoming solar radiation (called, insolation) supply all the energy for all these processes. When radiation strikes the earth, earth is heated up. This heat energy then transferred to the overlying air through conduction and convection. Now air starts moving horizontally as well as vertically. This causes all the weather and insolation is the only force for all these, weathers. 3.2 INCOMING SOLAR RADIATION – INSOLATION What is insolation? It is sun’s radiant energy that strikes the earth. Not clear? Radiant energy from sun that strikes the earth is called insolation. It is short form of “incoming solar radiation”. Radiation emanating from the sun consists of a range of wave lengths, known as solar spectrum. Each wavelength contains its own energy. Solar spectrum includes X-rays, gamma rays, ultraviolet rays, visible light, infrared rays, microwaves, and radio waves. Of these, ultraviolet, visible and infrared portions constitute more than 95% of the energy received by earth. Most of the ultraviolet radiation is prevented by existing ozone layer in the upper atmosphere. Part of the long waves is absorbed in the troposphere. The radiation which ultimately reaches the earth mainly comprises visible light. This visible light is composed of seven colors that make the rainbow after the rainfall at some times. As you know these seven colors are: violet, indigo, blue, green, yellow, orange and red. It is interesting to note that out of the total energy emitted by sun, only two-billionth of it is intercepted by the earth. Only this small amount of energy is responsible for all the physical processes taking place in the atmosphere and all the biological processes on earth. Do you know how much energy reaches the earth? It is difficult to say how much energy reaches the earth’s surface. But, scientists have estimated the amount of energy reaching the edge of the atmosphere (top of the atmosphere). The average amount of energy striking the outer atmosphere per unit area is known as the solar constant. It is estimated that a mean value of 1.940 langleys per minute of energy strikes the outer atmosphere. One langley equals to one gram-calorie per centimeter. In other words, 1.940 g cal per of energy reaches one centimeter area of outer atmosphere per minute (i.e. solar constant = 1.940 g cal / cm / min). In addition to the radiation, sun emits energy as “solar wind”. What is solar wind? It is a stream of charged particles (i.e., plasma) ejected from upper atmosphere of the sun. It also consists of magnetic fields. The effects of solar wind are not well understood.



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However, it is known that it interferes with radio communication, knock out power grids on earth, and disturbs earth’s magnetic field. 3.2.1 RADIATION BALANCE Now let us turn to know more about solar radiation and its effects on earth and its atmosphere. As far as earth is concerned, radiation means both incoming solar radiation and outgoing radiation emitted by earth’s surface. Before radiation reaching the earth’s surface, it travels through the atmosphere. When it passes the atmosphere, some of the radiation energy is reflected by clouds, and some are scattered and absorbed by gases and particles in the atmosphere. The remaining radiation finally reaches the earth; even some of the radiation reaching the earth’s surface or water surface is reflected back. The amount of radiation reflected depends upon the surface characteristics. The reflected solar radiation is called, albedo. Albedo of a water body is different from that of a land surface; albedo of a forest is different from that of a desert and so on. That is, albedo values vary with the type of the surfaces on which the radiation strikes. The scattered radiation by atmospheric constituents, may reach the earth and this is called diffuse radiation. On a cloudy day, the light we receive is not direct radiation but diffused radiation passing through the clouds. Now let us turn our attention towards the amount of radiation received and the amount of radiation emitted by the earth. Let us assume that total energy received by outer atmosphere at a given location is 100 units (say 100%). Of these, some are reflected, absorbed, and/or scattered. Some units finally reach the earth’s surface directly or through diffuse radiation. The earth re-emits either all or part of the received radiation. All the above details constitute radiation balance. On average, out of all the energy received at the edge of the outer atmosphere, only 31% directly reaches the earth’s surface (or water surface; hereafter, the term earth’s surface includes water surface too). This energy is called direct radiation. Almost 30% is reflected by the atmosphere to the outer space. Clouds reflect approximately 25% and the dust particles, about 5%. 17% of the energy is absorbed by clouds and other atmospheric constituents (dust particles and gaseous molecules). Some of the particles and gases scatter the radiation in the atmosphere. Some of the scattered radiation eventually reaches the earth’ surface. It is called diffuse radiation. Diffuse radiation reaching the earth’s surface accounts for about 22%. Thus, earth receives on average, 53% of the solar energy both directly and through diffuse radiation. 3.2.2 EARTH’S OUTGOING RADIATION Now, if all the energy received by the earth’s surface is retained, then earth will become very hot and inhabitable place. Surface of the earth also reflect some amount of energy. The earth’s surface is heated up by the energy received by it. Of course, the remaining energy available after reflection heats up the surface. Some of this heat energy



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is transmitted to overlying air through conduction and this in turn will initiate the convection in the air above the earth’s surface. As the earth’s surface is heated up, it will become hot and hold the thermal energy. The earth at this point, earth starts emitting energy in the form of long wave radiation. This is called outgoing radiation.

3.2.3 GREEN HOUSE EFFECT Part of the outgoing radiation is absorbed by the atmosphere and retained as heat energy. The remaining energy escapes into outer space. Carbon dioxide, water vapor, and few other gases in the atmosphere are capable of absorbing the outgoing radiation. (called, green house gases) the concentration of these gases, more the amount of long wave radiation is absorbed. It is a natural phenomenon occurring in the atmosphere. It helps preventing the earth from drastic cooling of the earth and its atmosphere. If all the heat energy from the earth’s surface is lost to the space, then earth will become too cold. These gases act like a blanket and provide the earth with “blanketing effect”. This process is called Green house effect. However, the intensity of this effect may vary from place to place depending upon the concentration of these gases in the atmosphere. For example, over desert atmosphere, the amount of water vapor is far less as it is a dry place. Carbon dioxide concentration is also very less as life is sparsely distributed and less number of living organisms exist here. Hence, more radiation will escape into the space and very little amount of radiation is retained. Consequently, the desert atmosphere will be cool during night. Self-check Exercise 7

Define the following:

a) Albedo b) Diffuse radiation c) Direct radiation

Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

3.3 WEATHER Now let us turn our attention towards understanding the weather: what causes it and how it is caused. First, we should know what weather is. Weather is the conditions of



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the atmosphere experienced by humans at any given moment. Weather is used to refer to the atmospheric conditions that exist for a short duration (hours or days). These conditions fluctuate and vary temporally over a given place. Often people confuse this with the term, climate. Climate refers to the average atmospheric conditions over a long period of time (month or season) of a place. What are those conditions? At times, we feel our atmosphere is very hot / cold, sultry and humid / dry, rainy, stormy etc. All these experiences are due to atmospheric conditions such as, temperature, humidity, wind speed and its direction, rainfall, etc. These conditions vary both spatially and temporally. 3.3.1 TEMPERATURE Temperature is an index of sensible heat. Bear in mind that it does not measure the amount of heat energy. It indicates the degree of molecular activity or kinetic energy of molecules. As it describes the kinetic energy, it specifies the speed of the movement of molecules. In case of gas (air), molecules move and change their location; but in case of solid, the molecules do not change their location but only vibrate it their place. The speed of this vibration is described by temperature. When a body has higher temperature, heat will flow from it to another body which has lower temperature. That is heat flows from a body with high temperature to a body with low temperature. Temperature is measured using thermometers. Temperature is reported in any of the three scales, viz. Celsius scale, Fahrenheit scale, and Absolute (Kelvin) scale. Of all the above, Celsius scale is used throughout the world to report the atmospheric temperature. It is named after the Swedish Astronomer Andres Celsius. 0 °C is the triple point temperature at which the gaseous, liquid and sold states of water are at equilibrium under standard pressure. The boiling point of water under standard conditions is at 100 °C. Kelvin scale is based on absolute zero. At absolute zero molecular activity ceases theoretically. Absolute zero in Kelvin scale is equal to -273.16 °C. Each degree on Kelvin scale is equal to that of Celsius scale. Accordingly, the value of 273 is added to Celsius value for converting it into Kelvin.

Fahrenheit scale is an old scale used formerly. However, it is still used in United States of America. It is also used in medical field to mention human body temperature. In this scale, boiling point of water is 212 °F and freezing point of water is 32 °F. Fahrenheit can be converted into Celsius by the following formula:

Air temperature is mostly measured using simple glass thermometers filled either with mercury or alcohol. Other advanced thermometers are also available. Celsius scale is widely used internationally to report air temperatures.

3.3.2 ALTITUDINAL TEMPERATURE DISTRIBUTION

5

9 C = (F-32)



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All the weather phenomena occur in lower atmosphere – troposphere. Yes, our weather is seldom affected by conditions exist above the troposphere. Therefore, we limit our discussion with troposphere when we learn about weather. Troposphere is the layer in which we all live; movement of air occurs both vertically and horizontally. As mentioned earlier, temperature decreases with height in troposphere. Rate of decrease of temperature with height is called lapse rate. As already mentioned, average lapse rate in troposphere is -6.4 °C / km. However, it may vary at different conditions. We shall learn more about vertical temperature distribution when we study about atmospheric dispersion of pollutants. Self-check Exercise 8

1. Distinguish between weather and climate 2. What is lapse rate? 3. What is the average lapse rate of the troposphere?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 3.3.3 HORIZONTAL TEMPERATURE DISTRIBUTION Temperature differs horizontally at different locations. Temperature of a place also varies at different times of a day and at different months and seasons of a year. These variations are due to several factors. Incoming solar radiation is the major factor which determines the temperature of a place. The angle of the sun’s rays and length of daylight determine the amount of insolation received in a certain place. The angle of sun’s rays and length of daylight are determined by latitudinal location of a place and time of the day. As the earth revolves around the sun, one half of the globe is exposed to sun’s rays and other half remains dark at any given time. The illuminated surface of the earth keeps changing as the earth rotates itself on its own axis. This results in occurrence of day and night time alternately over a given place. However, the entire half of the globe does not receive equal amount of sun’s radiation. In addition, as the earth keeps rotating, the amount of radiation received at a given location varies over time during daytime.

The sun’s rays strike almost perpendicular near the equator and at angles over high latitudes. This means farther away from equator more will be the angle of striking of sun’s rays over a place. Moreover, the earth’s axis is tilted at angle of 66½ degrees to the plane of the ecliptic. This tilt is always in the same direction throughout its orbit around the sun. The tilting of the earth in the same direction is called parallelism. This parallelism is the key responsible factor for seasonal variation over the earth during a year.



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Northern hemisphere is tilted to a maximum extent towards the sun around June 22. Months closer to June are summer months in northern hemisphere. During this period, northern hemisphere receives greater amount of sun’s energy than southern hemisphere does. Around December 22, the southern hemisphere is tilted to the maximum extent towards the sun. As a result, just opposite occurs during this period. That is southern hemisphere will receive greater amounts of solar energy than the northern hemisphere does. This variation determines the length of the daytime over a place. That is the length of the daytime is a function of latitude and month of the year. In general, the places near equator (lower latitudes) receive more amounts of sun’s energy than the places over higher latitudes. In addition to this variation, morning hours and evening hours receive less amounts of sun’s energy when compared to the sun’s energy received during noon hours. During noon, the sun’s rays strike vertically overhead. But during morning and evening hours, the sun’s rays strike at angles. These variations cause the same amount of radiation fall over a small area during noon and over a relatively larger area during morning and afternoon hours. As the earth’s surface receives the energy from the sun, it gets heated up. But this heating up also differs as the type of the surface differs. Different surfaces get heated up differently. For example, rocky surfaces are heated up rapidly while water surfaces take long time to get heated up. Similarly the rocky surfaces loose the energy rapidly while water surfaces loose the energy slowly. Other surfaces too behave differently depending on their thermal properties. Over a certain place many different types of surfaces may exist. All the anomalies discussed above, determine the weather of a given place at a given time. Heat energy received by a surface is transferred both downward and upward. The overlying air molecules are heated up due to conduction. Thus heated air become less dense and they tend to move upward. As the heated air moves upward, the air above this air (relatively cool air) tend to sink downward. In this way air starts moving up and down and thereby, heat energy is transferred by air currents. This process is called, convection. Through the processes of conduction and convection, air either is heated up or cooled down. All these determine the temperature of overlying air - atmosphere. The heating up of air is different as the underlying surfaces are different. For example, air over water surfaces will be cooler than the air over land surfaces of a given place. Consequently, air over the water will be denser than the air over the land surface. This will result in movement of air from over water surface towards over the land surfaces. During night time, opposite will occur – air from over the land move towards water. This movement of air is called sea-land breeze. As the different surfaces of the earth are heated up differently due to variations in surface characteristics, the air above these places will have different temperatures accordingly. This variation will tend to move horizontally. Horizontal movement of air is termed as wind. Thus winds are generated. In the same way, the differences in air temperature over different latitudes cause the movement of air in large scale. This large scale movement of air is called global circulation.



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Temperature of the atmosphere over a place changes during day and this is called the diurnal cycle. It also changes during a year and this change is called annual cycle. Temperature reaches at its maximum at around 3 p.m. of the day. Earth receives the sun’s energy from dawn till dusk. Maximum energy is received at noon and as a result earth is heated up to a maximum extent. Then this heat energy is transferred to overlying air. There is a time gap between these two events: heating up of the earth’s surface and transfer of the heat to the overlying air. Thus the maximum temperature is attained around 3 p.m.

After sunset, earth starts loosing its heat energy through outgoing infrared radiation. As it looses gradually, the minimum temperature is attained around 4 a.m.


Briefly describe the reason for temperature variations

a) Diurnally b) Seasonally c) At different Latitudes


3.3.4 ATMOSPHERIC TEMPERATURE MEASUREMENTS

Atmospheric temperature is measured by thermometers. Various kinds of thermometers are available. Mercury- in-glass and alcohol- in-glass thermometers are very simple and inexpensive thermometers available. Accuracy of the measurements depends on the way they are manufactured and calibrated. Usually, for measurement of surface air temperatures, the thermometers are mounted in a louvered instrument shelter.

Other types of thermometers are also available. Thermometers are made with bimetallic elements so that temperature differences affect their shape and this difference in shape is translated to record temperature. Electrical / electronic thermometers l ike thermocouples and thermistors are also available to record temperatures automatically.

Specially made thermometers are available to record maximum and minimum temperatures of a day. The simplest maximum thermometer is a mercury thermometer with a constriction in the bore near the bulb. The minimum thermometer is made with large bore and filled with colorless alcohol. A tiny, dark and dumbbell shaped index is placed in the bore below the top of the alcohol column. Both these thermometers are mounted horizontally and placed inside a specially designed shelter, Stevenson screen.



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The constriction in the maximum thermometer allows the expanding mercury to pass as the temperature rises. The column of mercury breaks at the constriction as the atmosphere cools down. It leaves a part of the mercury in the bore at the same position when maximum temperature was attained. Thus the maximum temperature is recorded.

Alcohol in the minimum thermometer contracts as the temperature decreases. During its contraction, lower meniscus of the alcohol pulls the index along and leaves it at the point where minimum temperature was attained.

After, noting down the readings of maximum and minimum temperatures, these thermometers are reset for the next cycle of measurements.

For continuous recording of temperature, thermograph is used. It consists of an element responsive to temperature change, a system of levers to translate these changes to a pen arm and a cylindrical clock drum around which a calibrated chart is mounted. However, the recordings are not as accurate as with the thermometers. Hence, frequent checking and adjustments are made.

3.3.5 HUMIDITY

Humidity is the term used to represent the amount of water vapor in the air. Water vapor present in the atmosphere plays important roles in determining weather of a place. When high amount of water vapor is present in the atmosphere, we will feed discomfort. This discomfort is called sultry. Atmosphere will be dry when water vapor is so less. This also causes discomfort. The atmosphere of the places near the water bodies will have high moisture content while that near the dry areas like deserts will have low or almost nil moisture content. Water vapor enters the atmosphere from water bodies through evaporation. Subsoil water enters the atmosphere b o t h through evaporation and evapotranspiration by plants.

Water vapor present in the atmosphere may form clouds as they are lifted to higher altitudes. Clouds get saturated as they gain more and more water vapor. At certain point of time after saturation, the water may fall from the atmosphere through the process called precipitation. The falling of water either in liquid form or in solid form from the atmosphere is called precipitation. Thus atmosphere becomes part of the hydrological cycle.

At any given point of time, atmosphere holds water vapor. The amount of water vapor held by atmosphere varies over time during a day and over a year. Air is a mixture of gases present in the atmosphere. As such air does not hold the moisture; but the space available among the gaseous molecules hold moisture. The water vapor holding capacity of air varies according to the temperature and pressure of air. Therefore, the amount of water vapor present in the atmosphere is expressed in various ways. Specific humidity: it is the ratio of the mass of water vapor actually in the air to a unit mass of air, including the water vapor. For example, specific humidity is 10 g per kg when a kilogram of air contains 10 g of water vapor.



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Mixing ratio: it represents the amount of water vapor in one unit mass of dry air (dry air is the air without moisture content). When 10 g of water vapor is present in 1 kg of dry air then mixing ratio is 10 g per kg. However, the total amount of air and water vapor would be 1010 g (1.01 kg). Vapor pressure: it is the partial pressure exerted by water vapor in the air. Vapor pressure is expressed in the same units used for barometric pressure – mm of Hg or millibars. Saturation vapor pressure: when air space contains the maximum possible amount of water vapor at a given temperature and pressure, it is said to be saturated. The partial pressure exerted by water vapor at this condition is called saturation vapor pressure. The temperature at which air is saturated with water vapor is called dew point. Below dew point, condensation of water vapor occurs. Relative humidity: it is the ratio of the amount of water vapor present in a parcel of air to the maximum amount of water vapor that air could hold at the same temperature. Thus if a kg of air contains 9 g of water vapor when its maximum holding capacity is 12 g at a given temperature under constant pressure, the relative humidity is 75%.

When temperature increases the saturation vapor pressure also increases resulting in increase in holding capacity of water vapor. For example, at the increased temperature, let us assume, the vapor-holding capacity of air is 15 g and only 9 g is present then the relative humidity is 60%.

Relative humidity reaches its diurnal maximum in the early morning hours when temperatures are low and then decreases to a minimum in the early afternoon. In the same way, it is greater in winter than in summer over land. However, during monsoon months in summer, moist air pass over the land and thereby high relative humidity values are attained. Over oceans, relative humidity reaches maximum due to evaporation of sea water. Mid latitude mountains also tend to have high relative humidity values during summer due to stronger convective flow of moist air. Self-check Exercise 10

Define the following: a) Humidity b) Specific humidity c) Relative humidity d) Vapor pressure e) Saturation vapor pressure f) Precipitation




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3.3.6 MEASUREMENTS OF HUMIDITY

Direct measurements of humidity and water vapor content are not possible with ordinary instruments. Hence, they are measured indirectly using psychrometer. It consists of two thermometers, both mounted on the same frame. One thermometer is wet-bulb thermometer and other one is dry-bulb thermometer. Wet-bulb thermometer is mounted little lower than the other and its bulb is covered with a cloth wick that can be wetted with water during observation. The psychrometer is either swung in the air or aerated by a fan to provide passage of air over the bulbs of the two thermometers. While air passes over the wet-bulb thermometer, evaporative cooling lowers the wet-bulb reading. The difference between the two readings is called wet-bulb depression. The dry-bulb temperature, wet-bulb depression and atmospheric pressure are used to determine the humidity values from psychrometric tables derived already from mathematical relations. If there is no difference between wet-bulb reading and dry-bulb reading, then the wet-bulb depression is zero. The zero value is attained when relative humidity is 100 percent.

Hair hygrometer is a device available for measurement of relative humidity directly, though this instrument does not provide accurate values at low temperatures. It is operated on the principle that human hair lengthens as relative humidity increases and contracts with decreasing relative humidity. Its principle is utilized in the hygrograph, which is a recording hygrometer with a clock drum and pen arrangement.

Yet another device, infrared hygrometer is available for measurement of humidity. It employs a beam of infrared radiation projected through the air to a detector. Two separate wavelengths are used; one is absorbed by water vapor and other passes through undiminished. The ratio of the radiation transmitted by the different wavelengths gives the indication of the amount of water vapor in the path of radiation.

Other devices like hygristor and dew point hygrometers are also available for measurement of humidity. Hygristor is a device through which electrical current is passed across a chemically coated strip of plastic. The passage of electricity is proportional to the amount of moisture absorbed on its surface. This hygristor is commonly used in radiosondes used for upper air observations and other instruments operated remotely to measure the water vapor content. 3.3.7 PHASES OF WATER IN ATMOSPHERE

As already mentioned water vapor present in the atmosphere plays significant roles in determining weather and climate. Water vapor in the atmosphere is also a part of water cycle. In order to understand its influence on weather, we should know the properties of water. Water is a chemical consisting of two hydrogen atoms and one oxygen atom. Its chemical form is H2O. Water may be present in the atmosphere in all of its three physical forms: solid, liquid and gas. It may change its form at any point of time in the atmosphere by exchanging latent heat.

The change of state from liquid to vapor is called evaporation. It results when molecules escape from any water surface. Evaporation takes place by utilizing vast



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amounts of energy. In this way, a large amount of energy in the form of latent heat is transferred from earth’s surface to the atmosphere.

The rate of evaporation is determined by three factors: vapor pressure, temperature and air movement. Evaporation increases as the saturation vapor pressure at the water surface becomes greater than the actual vapor pressure of the adjacent air. Hence, evaporation takes place at faster rate into dry air than into air with high relative humidity. When temperature of water increases with other factors being equal, the rate of evaporation also increases. That means, whenever temperature of water is greater than that of air, evaporation always takes place. Wind movement over the surface of water replaces moist air by relatively dry air. This also increases evaporation. Latent heat of vaporization: this is the heat energy utilized for the transformation liquid into vapor and/or evolved during transformation of vapor into liquid without change in temperature. The heat used for evaporation is retained by the water vapor without rising temperature. The latent heat of vaporization ranges in value from nearly 600 calories (2,510 joules) per gram of water at 0 °C to about 540 calories (2,259 joules) at 100 °C. This variation is due to decrease in the difference between kinetic energy of the escaping molecules and the average kinetic energy of all the water molecules as temperature increases. Evaportranspiration: loss of water vapor by terrestrial plants through their leaves and stems is called transpiration. The combined losses of water vapor by evaporation and transpiration from a given area are called evapotranspiration. Thus the atmosphere over thick vegetation like forest will always have greater humidity values than that over non- vegetated or less vegetated atmospheres.

The amount of solar energy received by a place is an important factor for evapotranspiration. The intensity of solar radiation is determined by the latitude of a place. Mean annual rates of evapotranspiration are greatest between 20° N and 20° S where the highest amount of net radiation is received. Greater evapotrnspiration is accounted over southern hemisphere than that over northern hemisphere as southern hemisphere consists of larger proportion of oceanic surface.

When water changes its state from vapor to liquid, it is called condensation. Condensation is a very important process for the formation of clouds. As the moist air comes into contact with cool surfaces, it gets cooled to the dew point temperature and a part of the vapor condenses into liquid form on that cool surface. Condensed water over the surface is called dew.

During the condensation process, the heat is released as the heat is assimilated during vaporization. This released heat is called latent heat of condensation. Liberation of the latent heat of condensation may slow down the cooling process. This latent heat released during condensation is one of the energy sources for atmospheric processes.

Condensation also occurs from cooling in the free air. However, it requires the presence of very small particles called condensation nuclei. Some of these particles are hygroscopic and hence have greater affinity towards water. As a result condensation will



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occur on the surface of these hygroscopic particles even above the dew point. On the surface of other particles, water vapor may condense upon cooling i.e. at dew point.

After sufficient amount of vapor is thus condensed they become visible as haze. When more amount of vapor condenses, condensed water droplets increase in number and become dense to form fog or cloud. Since the particles play vital role in the process of condensation and the formation of clouds, they are called cloud condensation nuclei (CCN). When water changes from liquid to solid, it is called freezing and when ice melts into liquid, it is called melting. While melting takes place at 0 °C, freezing does not occur at 0 °C but below 0 °C.

Water may contain foreign materials in dissolved form and/or in suspended form. It may also be covered by foreign substances. Presence of foreign substances in water will lower the freezing point below 0 °C. Amount of water involved and electrical charges also lower the freezing point.

Water may bypass liquid state and become vapor from ice and vice versa. This process is called sublimation. Sublimation is the process of becoming vapor from solid phase or becoming solid from vapor phase. When dry air with a temperature well below the freezing point comes in contact with ice, some molecules of water from ice will become vapor. When water vapor comes in contact with cold surface well below the freezing point vapor may immediately become ice.

Self-check Exercise 11 1. Describe the role of particles in the atmosphere in formation of clouds. 2. Define the following:

i. Latent heat of vaporization ii. Latent heat of condensation

iii. Sublimation iv. Evapotranspiration

Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

3.3.8 PRECIPITATION

Precipitation is water falling on earth in either liquid or solid form. Precipitation occurs in the form of rain, drizzle, snow, hail and/or their modifications. Precipitation is an important part of the hydrological cycle which brings water over the continental regions. The precipitated water either runs as stream or infiltrate into the ground to become ground water. Some part of the precipitated water is stored in natural and/or artificial reservoirs such as dams, lakes, ponds and tanks.



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Water vapor condensed over condensation nuclei form clouds in the atmosphere and these clouds give out the water as precipitation. Of course, the formation of clouds and the process of precipitation are quite complex.

Rain: it is precipitation with large liquid water droplets. Rain drops range from less than 1 mm to 5 mm in diameter.

Drizzle: it is precipitation consisting of uniformly minute droplets of water (less than 0.5 mm in diameter).

Snow: it is precipitation consisting of large ice crystals called snow-flakes. It is formed by the ice-crystal process. These crystals do not have time to melt before they reach the ground.

Hail: it is precipitation in the form of ice pellets called hail stones. The process of formation of hailstone is complex one.

The process of precipitation (in any form) is quite complex. Details of precipitation are not required for this course and hence not explained.


Define the following: a) Rain b) Drizzle c) Snow d) Hail

Note: Please do not proceed unless you write answers for the above two in the space given below: …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….. 3.3.9 PRESSURE

You might have come across the news of cyclone and depressions in news bulletin. What are they and how are they formed? To know the answers for these questions, we should know about pressure. What is pressure? The definition for the word pressure is “the force per unit area acting on a surface”. The SI unit for pressure is the pascal. One pascal is equivalent to 1 N m-2. The atmospheric pressure is expressed in millibars. 1 millibar is equivalent to 100 N m-2 (=100 pascal).

What is atmospheric pressure? Atmosphere is held by earth by its gravitational pull. The combined mass of all air molecules lying above the earth exert a force on earth. So, atmospheric pressure is the force exerted by the column of air per unit area above the earth’s surface. The amount of air in a column over a unit area will differ from place to place as there is variation in its altitude. Yes, over top of a hill, the amount of air in a column will be less than the amount of air in a column over a sea surface. Hence, the atmospheric pressure will be less over the hill than over sea surface or a land surface at low lying areas. As the height of a place increases from the mean sea level, the pressure decreases. Of course, as you go deep under the earth, the pressure will be more than that



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over land. Under the sea, the water column along with overlying air will exert pressure which will be unbearable.

The atmospheric pressure over mean sea level under normal conditions is 1013 mb. The atmospheric pressure over the top of the Mount Everest is 320 mb.

In addition, cold air will generally be denser than warm air. As a result a column of warm air will exert less pressure than that by a column of cold air. The differential heating of surfaces (due to differences in surface characteristics), the air lying over these surfaces will be heated differently and hence will exert pressure differently. This will cause anomalies of pressure values in horizontal atmospheres. Consequently, air from high pressure region tends to move towards the low pressure region. Thus, winds are generated. The strength of the winds is determined by the difference in pressure values. Greater the difference in pressure values, stronger will be the speed of the wind. Let us discuss about winds and their pattern in detail in the next lesson. We shall now turn our attention to the measurement of atmospheric pressure. Self-check Exercise 13

What is atmospheric pressure? Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

3.3.10 MEASUREMENT OF ATMOSPHERIC PRESSURE

Atmospheric pressure measurements are essential in analyzing charts of winds, storms, etc. A simple measuring device is mercurial barometer. It was first developed by the Italian scientist Evangelista Torricelli in 1643. He filled a glass tube with mercury and then placed the tube upside down in a dish of mercury. In his experiment he found that instead of mercury running down into the dish, the atmospheric pressure pushing the mercury in the dish down and thereby the mercury in the dish supported the mercury in the tube from moving down. As a result of this experiment, Torricelli invented the world’s first pressure measuring instrument, barometer.

At sea level, under standard conditions, mercury remained at the height of 76 cm (=760 mm) in the column. This unit, mm of Hg became the expression for atmospheric pressure. 760 mm of Hg is equivalent to 1 atmospheric pressure. However, the pressure measured in units of height is not satisfactory. Pressure can be expressed in different units and these units are inter-convertible. It is convention among meteorologists to express the atmospheric pressure in millibars.



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Aneroid barometer is an instrument used for measurement of atmospheric pressure. It consists of a partially evacuated metal wafer called sylphon cell. This cell expands or contracts in response to changing pressure. The fluctuation is linked mechanically to an indicator on a calibrated dial. Barograph is the aneroid barometer designed to record the pressure continuously on a chart. It consists of a pen arm attached to sylphon cells whose expansion or contraction activates the pen to record the pressure on chart.

3.4 LET US SUM UP In lesson 3, we have learnt about meteorology. We could distinguish between the term weather and climate. We learnt that the insolation (incoming solar radiation is almost responsible for all the atmospheric processes occur. Now, you have become familiar with:

· Incoming solar radiation · Radiation balance · Outgoing radiation and green house effect · Temperature, its variation vertically and horizontally · Humidity – what is humidity, and various expressions of humidity · Role of water vapor in the atmosphere – formation of clouds and precipitation · Atmospheric pressure and its measurements Now, you must be able to explain all the above concepts clearly.


· Go through weather bulletin of news paper daily and record each of the temperature, pressure and rainfall values on a graph sheet separately for a period of three months.

· Do you infer any change in your records? If so write down. 3.6 POINTS FOR DISCUSSION

· By now, you know that solar radiation strikes the earth’s atmosphere and pass through it

· During its passage, some of the radiation is reflected, scattered, and absorbed · Earth in turn emits its heat energy in the form of infrared radiation which is again

absorbed by certain gases of atmosphere causing green house effect. · Water plays important role in the atmosphere.

3.7 CHECK YOUR PROGRESS

· Can you distinguish between incoming solar radiation and outgoing radiation · Can you explain the horizontal temperature variation? · Can you describe the roles of water in atmosphere? · Did you understand the concept of pressure?



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3.8 REFERENCES








Delhi, 1987



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LESSON 4 - FORMATION OF WINDS AND GLOBAL CIRCULATION

Contents

4.0 Aims and objectives 4.1. Winds and their formation 4.2. Geostrophic wind 4.3. Gradient wind 4.4. Turbulence 4.5. Local winds

4.5.1. Sea-Land breeze 4.5.2. Mountain-valley winds 4.5.3. Other local winds

4.6. Atmospheric circulation 4.6.1. Atmospheric circulation – hypothetical model 4.6.2. Atmospheric circulation – idealized model 4.6.3. Actual atmospheric circulation pattern

4.7. Secondary surface circulation and Indian Monsoon 4.7.1. South West Monsoon 4.7.2. North East monsoon


4.0 AIMS AND OBJECTIVES In this lesson we are going to learn about the formation of winds and their patterns. In fact, the study of winds is also a part of Meteorology. But for our convenience, we will be studying about it in a separate lesson. Winds are very important as they play a vital role in distributing the energy over a large area – even at global scale. The earth is heated up differently at different latitudes. The places near equator receive surplus energy while places near poles and high latitudes receive less energy; places near poles and at high latitudes become energy-deficient. The surplus energy over equator and low latitudes is converted into kinetic energy for the formation of winds. Thus the surplus energy in transferred from equator and low latitudes to the high latitudes by winds. In this lesson we will be learning all these in detail.

4.1 WINDS AND THEIR FORMATION

The movement of air is called wind. Where from do they originate and where do they end at? Are there any pattern exist in the flow of winds? Yes winds follow same pattern globally. This pattern is called global atmospheric circulation. In the past the sailors took the advantage of the wind for the movement of ships and boats. The sea routes



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were chosen according to the winds blown and their direction. Now let us learn how these winds are formed and how they flow across.

Earth receives unequal amount of radiation and hence heated differently at different latitudes. Earth also rotates on its axis. These two factors cause the formation of winds and result in global circulation. Through this the surplus energy received over low latitudes are transported as kinetic energy in the form of winds towards high latitudues.

Different types of surfaces of the earth are heated up differently as their thermal properties differ. Even if places are close to each other in their latitudinal position, differences in their surface characteristics make them have different thermal properties. Consequently, the pressures over these different places also differ. This will create horizontal pressure variation over an area of few meters to several kilometers. This variation result in a gradient of pressure anomalies over the entire area. This horizontal pressure gradient is responsible for the movement of air, wind. This pressure gradient drives the air to move, and hence this force is called pressure gradient force.

Winds may blow gently or violently or with moderate speeds. Gentle winds bring

relief and comfort from heat of the day. Violent winds may sometimes bring devastating effects. Storms, cyclones, tornado etc. are such violent winds that bring devastating effects. In addition, winds carry moisture, heat, pollutants etc. from one place to other. Self-check Exercise 14

What is pressure gradient force? Explain briefly. Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

4.2 GEOSTROPHIC WIND

Due to pressure gradient force, air moves from high pressure region to low pressure region. When a surface is heated up the overlying air is heated up and become light. The light air tends to ascend. As the air rises, the pressure over that surface becomes low. To compensate this low pressure air will start moving from a high pressure region towards this low pressure region. When air moves from high pressure region, the overlying air at that point will tend to sink. The air ascended will move towards the region where from air is sinking. This completes the circulation of air between two different places vertically.

Consider a large area, and the pressure keeps varying over this area as you move away from one place farther and farther. That means pressure keeps changing as you move away from a place to another little by little. The line connecting areas with equal pressure is called isobar. When pressure changes over a large area, that area may be occupied by



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several isobars, each isobar denoting a particular pressure value. Sometimes, these isobars may be parallel or circular over a large area of consideration.

Once the air start moving, other forces come into action: Coriolis force and frictional force. Coriolis force: First we shall learn what the Coriolis force is? It is a deflective force. Any moving object, stream of water or air over the surface of spinning planet, will be deflected due to the rotation of earth. This is called Coriolis force. Coriolis force will deflect moving bodies towards their right in northern hemisphere and towards their left in southern hemisphere. Due to this Coriolis force, the moving air over the earth’s surface will be deflected accordingly. The existence of this force was discovered and demonstrated by Gaspard de Coriolis in 1844. However, the effect of Coriolis force is nil over equator and its effect increases toward the poles. It acts at an angle of 90° to the horizontal direction of the wind and is directly proportional to horizontal wind speed. When pressure gradient initiates the air to flow, the Coriolis force deflects it to flow parallel to the isobars. Remember, the winds must flow from an isobar with low pressure value towards the isobar with high pressure value. Instead of this perpendicular flow, the wind flows parallel to the isobars as a result of Coriolis force. The wind thus flowing is called geostrophic wind. Self-check Exercise 15

· What is Coriolis force? Explain briefly · How is geostrophic wind formed?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 4.3 GRADIENT WIND

If the air moves along curved isobars, a net centripetal acceleration tends to pull it toward the center of curvature. This will result a rotating motion of air relative to earth’s surface. Such wind is called gradient wind. If this gradient wind circulates in counter-clock direction, then it is termed as cyclone in northern hemisphere while it is called anticyclone in southern hemisphere. Similarly, the clockwise motion of air is called cyclone in southern hemisphere while it is called anticyclone in northern hemisphere.

At the place under the low pressure region, air flowing toward this region tends to converge and ascend and hence, this place is called area of convergence. Likewise, under the high pressure region, air flows away from it as the air sinks from above and hence, this region is called area of divergence.



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In cyclonic circulation, surface air moves towards the centre, the low pressure cell,

and converges. Thus converged air ascends vertically in the center of the low pressure cell. The reverse happens in the center of an anticyclone – as the surface air diverges from the center of the anticyclone (high pressure cell), the air sinks from high in the center of the anticyclone (high pressure cell). In these ways, the cyclones are associated with rising air at their centers while, anticyclones are associated with descending air in their centers. 4.4 TURBULENCE

A third force may come into force when air starts moving due to friction exhibited by surface. The earth’s surface may consist smooth surfaces like water, or highly rough surfaces like rocky terrain, urban buildings etc. When air flows over the smooth water surface, the friction encountered is almost zero. But when wind flows over a rough terrain like a land with rocks or a land with urban buildings of various heights, it encounters friction. The magnitude of friction differs as the surface features differ.

The friction lowers the speed as well changes the direction of the wind. It creates

turbulence in winds. Turbulence is associated with lulls, gusts and eddies. Turbulence also increases with the increase of the wind speed. However, the surface relief does not pose any friction at the height of about 500 m. At the height of about 1000 m, the winds are no more under the influence of friction. As a result, the winds flowing at this height will be approximately equal to the theoretical geostrophic wind and/or gradient wind.

4.5. LOCAL WINDS

Before we turn our attention towards the atmospheric circulation at global level, let us see the local winds generated by differences in surface characteristics: sea-land breeze, mountain-valley winds, and other local winds.

4.5.1 SEA-LAND BREEZE

Some land areas are very close to large water bodies. Lands near sea, large reservoir, lakes and wide rivers are the best examples. During daytime the incoming solar radiation heats both the land surface and water surface. However, the land surfaces are heated up rapidly while water surfaces are not. The rapidly heated land surface in turn, heats up the overlying air in relatively short duration. Heated air becomes light and ascends high creating a low pressure region over the land surface. At the same time, the air above the water remains relatively cooler and denser to create a high pressure region over the water. This anomaly results in pressure gradient between the land and water surfaces. Now this pressure gradient force will start driving the air lying above water to move towards the land, this wind is called sea breeze.

During night, the earth looses it heat energy rapidly and gets cooled down. The water does not cool down so fast but remain relatively warmer during night. Relatively warmer water surface transfer its heat energy to the overlying air and thereby air becomes warmer and light to ascend high. This will create a low pressure over the water. At the



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same time, the overlying air at the land will be relatively cooler and denser creating a high pressure region. This anomaly results in pressure gradient (just opposite of what exists during daytime) between the land and water. Now the air from land will tend to move towards the water and this wind is called land breeze. 4.5.2 MOUNTAIN-VALLEY WINDS

On mountain sides, under a clear night sky the lands situated at high radiate heat and get cooled down. This in turn cools the air lying over those lands. Now the cool and dense air tends to slide down the mountain slopes into valleys and low lands. This air flow is called mountain breeze.

In the morning hours, temperature inversions may occur over the low lying areas.

As a result, the valley bottoms are colder than the hillsides. In general, inversions over a land area prevent the vertical motion of air. But the mountain breeze reached the valley, may gain considerable velocity and generate enough turbulent mixing to break the inversion. On warm sunny days, the slopes of mountain will be heated up and thereby the overlying air. This will generate an upslope flow of air towards the top of the mountain. The flow of air from slope of the mountains to the top is called valley breeze. When warm air moves up, it is replaced by cooler air from above the valley. This results in moderation of surface temperature. 4.5.3 OTHER LOCAL WINDS

Under the influence of gravity, the cold and dense air moves downward along the steep slopes. These winds are called gravity winds or katabatic winds. These winds are prominent under calm, clear conditions where the edges of highlands plunge sharply toward low lying terrain. These winds are fed by large quantities of extremely cold air that collect over the high land.

Katabatic winds sometimes may reach destructive intensities as of a waterfall from a high land. This kind of winds is experienced in the Rhône River valley of southern France during winter. Icy, high velocity winds drain from the snowy mountains to the valleys in this area. These winds are called mistral winds.

Another type of local wind is generated when the air is forced to pass across the mountainous terrain. As the air move upward, the moisture present originally is almost wrings out. After reaching the top, the winds cross over the mountain and slide down on the other side of the hill along its slopes. As the air has already exhausted its moisture, only dry and relatively warm air flows down with high speeds. Sometimes the speeds reach to 120 km per hour. These winds are yet to be named by the scientists.



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4.6 ATMOSPHERIC CIRCULATION

Now let us turn our attention towards the atmospheric circulation at global level. This circulation is called global atmospheric circulation. In real world, this global circulation is a complex one. Due to differences in the presence of landmasses and water bodies over the globe, the circulation becomes complex. However, we shall try to understand from a hypothetical model and an idealized model. Later, we shall learn the real existing atmospheric circulation.

4.6.1 ATMOSPHERIC CIRCULATION - HYPOTHETICAL MODEL

Let us assume that earth is not rotating. As the places near the equator receive the maximum insolation, the air above these places tend to rise and create a single cell of low pressure around the equator. Polar Regions receive the minimum amount of radiation and the air above these regions will be cold with maximum density creating a high pressure cell at each pole. The air would subside at these poles. Due to the above processes, (ascension of air over equator and subsidence of air over poles), the air will tend to move from poles towards equator at surface level. The air reaching the equator converges, ascends high and moves towards poles. This completes a full circulation. Thus two circulations of air are created: one over northern hemisphere and another over southern hemisphere.

4.6.2 ATMOSPHERIC CIRCULATION - IDEALIZED MODEL

Earth rotates on its axis. This rotation causes the deflection in the wind flow due to Coriolis force. As the equatorial region is heated up throughout the year, a low-pressure belt is formed over the tropical region. This belt is called inter tropical convergent zone (ITCZ). ITCZ is also known as doldrums. But in real world, it fluctuates in its position and intensity and is at times a weak, discontinuous belt. In this belt air rises as it is a belt of low pressure region.

The risen air starts flowing towards the pole but for reasons not clearly understood,

the air descends at around latitudes of 30° N and 30 ° S. The descending air produce a belt of high pressure each at the surfaces at these latitudes. These two high-pressure belts are called Subtropical Highs.

The descended air diverges and part of the air flows towards ITCZ and another part towards the poles. The descended air which flow towards equator is deflected to its right in northern hemisphere and to its left in southern hemisphere. Thus northeast trade winds and southeast trade winds are generated.

The surface air flowing toward poles from subtropical highs is also deflected by Coriolis force and become Westerlies (west to east blowing winds) . These winds form broad midlatitude belts between 30° and 60° in both hemispheres.

Over Polar Regions the air is dense and cool and hence exist high pressure cells centering over these regions. They are called Polar Highs. The air from polar highs tends to move towards the equator and as it flows is deflected by Coriolis force to become Polar Easterlies (easterlies are winds that flow from east to west).



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Polar easterlies flowing from poles will meet the westerlies near 60° in both the

hemispheres. As the two winds meet they converge and ascend, creating a belt of low pressure region at the surface, called Upper-Midlatitude Low. The sharp boundary along which these winds converge is called Polar Front. Self-check Exercise 16

· Explain ITCZ briefly. · Explain trade winds · Explain westerlies · What is polar front?


4.6.3 ACTUAL ATMOSPHERIC CIRCULATION PATTERN

The actual circulation pattern is quite complex. Northern hemisphere is occupied by two large land masses while southern hemisphere is mostly covered by water. Location of maximum solar heating shifts as the latitude of the vertical sun changes from 23½° N at summer solstice and to 23½° S at winter solstice. Continents exposed to maximum solar radiation will be heated up more rapidly than oceans at the same latitudes. This will result in producing individual pressure cells rather than uniform, globe-circling belts of low and high pressure. The individual pressure cells are called semipermanent highs and lows.

The ITCZ also does not exist as a continuous belt. It shifts its position along with shift in vertical sun. However, this shift is not prominent over the oceans as the water bodies respond slowly for variations in solar heating. ITCZ is located near 25° N in July over the continent (near south Asia). But it does not shift to that extent over oceans in the same month.

ITCZ migrates to southern hemisphere in January. This migration is far less pronounced in southern hemisphere as it is occupied mostly by water. However, ITCZ migrates to a maximum extent over Africa and Australia and to less extent over South America. But the migration is not that much over the oceans of southern hemisphere.

Likewise, the subtropical highs do not exist as a continuous belt encircling the earth. They are broken into five individual cells as semipermenant highs. There are five such cells exist over the oceans – one over each subtropical ocean. In northern hemisphere, there are two semipermenant highs: Bermuda High over North Atlantic Ocean and Hawaiian High over the Pacific oceans. In southern hemisphere, three semipermenant highs exist: one over each of South Pacific Ocean, South Atlantic Ocean and Indian Ocean.



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These semipermenant highs also shift their position with the sun but with a lesser extent when compared to that of ITCZ. This is again due to the delayed response of water to the seasonal changes in solar heating.

Arctic region is an ocean covered with ice. Large land masses of Eurasia and Northern America are located near the arctic region. As the water responds slowly to solar heating, the land masses close to arctic region cool down faster than the North Pole. This results in the existence of two highs over the land masses rather than exactly over arctic region. They are, the Canadian High, centered over northwestern Canada and the Siberian High over northern Asia. However, these Highs are existent only during winter.

In South Pole, the Antarctic region is dominated by land mass. Hence the polar high exists exactly over the Antarctic region as demonstrated in the idealized model.

The Upper-Midlatitude Low exists as two cells in Northern Hemisphere in January. They are Aleutian Low over the northeastern Pacific off Alaska and the Icelandic Low over North Atlantic, just west of Iceland. Convergence and ascent of air are quite complex in these cells. These two cells weaken and even disintegrate during summer. These midlatitude lows are fed by air from polar easterlies flowing from diverged air of the two polar highs. As these polar highs become non-existent in summer, there is no air flow to feed the Upper-Midlatitude Lows. Consequently, these Upper-Midlatitidue Lows become weak and even disintegrate.

In southern hemisphere, however, the Upper-Mid latitude Lows exist both in winter and in summer. All the circulation patterns at global scale mentioned above can be called primary circulation system of the atmosphere.


· What are the reasons for differences in existence of lows and highs over northern and southern hemispheres? Explain briefly.

· Why do the two highs exist over Canada and Siberia instead of over north pole during winter? Explain briefly.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 4.7 SECONDARY SURFACE CIRCULATION AND INDIAN

MONSOON

The wind patterns of primary circulatory system mentioned above are deviated at several parts of the globe due to various reasons. There is many such deviations take place at local level creating pronounced summer/winter contrasts in weather patterns. One such deviation is monsoon.



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Our Indian economy is dependant upon the successful monsoon rainfall. The word, monsoon is derived from mawsim, the Arabic word which denotes the change of season. Monsoon is a regional wind blowing towards land masses at a certain season and blowing off the landmasses during other season.

They blow approximately opposite direction in summer and winter. Though they

blow over several parts of the world, they are well developed over India and neighboring Southeast Asian countries. During summer months, in the northern hemisphere, the land surfaces are heated up more rapidly than the oceans. As a result, low pressure region is created over the continents. Now, relatively denser maritime air (from high pressure region) will flow towards the continental atmosphere. This phenomenon is similar to that of Sea- land breeze system but in large scale. 4.7.1 SOUTH WEST MONSOON

The ITCZ also shifts its position and stay approximately over the latitude of 25 - 30° N. Since, ITCZ is a convergent zone, the air flows towards it. Naturally the air over Indian Ocean is attracted by the ITCZ. When air moves from Indian Ocean they are originally southeast trade winds as they originate from Indian Ocean over southern hemisphere. When these southeast trade winds cross over the equator they are deflected by Coriolis force to their right and become southwest trade winds. As these trade winds pass over the large surfaces of Indian Ocean, they absorb and carry huge quantities of water vapor with them. Hence, the SW – Monsoon is also called wet summer monsoon.

When these southwest monsoon winds, come near Indian Peninsula, they are diverted into two main branches viz. Arabian Sea branch and Bay of Bengal branch. When Arabian Sea branch reaches the southern part of west coast of India, they encounter with the mountain range, Western Ghats. As this mountain range is a barrier for horizontal flow fort this moisture- laden southwest monsoon wind, the wind starts rising along the slope of the mountain range. This kind of ascending of air is called orographic lifting. When air ascends high it gets cool down to form clouds and then results in precipitation. Southwest monsoon winds touch the Kerala coast on 1st of June every year. There may be variation in the date of onset of monsoon.

The Bay of Bengal branch when encounters with the Himalayan Mountains they take a turn to west and flow over the northern parts of India. This moisture-rich air brings forth rain in these months. Monsoon winds from Arabian Sea branch advance from the southern most part of the country to northwards and reach up to Maharashtra and Gujrat coastal regions gradually. Similarly winds from Bay of Bengal branch advance and spread over many parts of North India. Roughly, monsoon winds reach over Delhi in the first week of July. This monsoon rainfall lasts roughly till the end of September or the first half of October.

4.7.2 NORTH EAST MONSOON As the sun’s position is gradually shifted from northern hemisphere towards southern hemisphere, the position of ITCZ also is shifted to the south of equator.



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Consequently, reversal of winds occurs. Now, the winds start blowing from northeastern direction towards the ITCZ. The winds are called North East monsoon winds – North East Trade winds. But these winds blow mainly from, landmasses located in the Northeast region of India. Consequently, they are relatively dry and do not bring rainfall over North India. Hence, North East monsoon is also called dry winter monsoon. However, when they pass over the Bay of Bengal, they absorb moisture and bring rainfall over the parts of Orissa, and almost all over Andhra Pradesh and Tamil Nadu. During the North East monsoon season, formation of cyclones over the Bay of Bengal is quite common. The cyclones formed, bring copious rainfall over the lands of Tamil Nadu, Andhra Pradesh and Orissa.

Both the Arabian Sea branch and the Bay of Bengal branches advance gradually and spread across the Indian subcontinent. However, the monsoon wind does not bring continuous rainfall throughout the season. There are some days with rainfall and some days without rainfall. Occurrences of rainfall depend on other factors too. Let us limit our learning with this. 4.8 LET US SUM UP

In this lesson, we have learnt the winds and their formation. We understood how winds are formed, how they are manipulated by Coriolis force and frictional force. We also learnt concept of sea- land breeze, mountain-valley winds and other winds.

We clearly understood the global circulation pattern. The locations of highs and

lows are understood. We studied the monsoon winds and accompanying rainfall considerably.

4.9 LESSON-END ACTIVITITES

· Take a sheet of paper and draw isobars and pattern of geostrophic wind · Take a sheet of paper and illustrate sea- land breeze · Take the world map and draw the circulation pattern (idealized) · On the world map, draw the actual circulation pattern · On the map of India, draw monsoon winds

4.10 POINTS FOR DISCUSSION

You know the causes of winds and their formation. You also know the cyclones and anticyclones; convergence and divergence. You are aware how sea-land breeze and mountain-valley winds are formed. The differences in thermal properties cause the winds blow from one place to other even in large scale. 4.11 CHECK YOUR PROGRESS

· Can you distinguish between geostrophic and gradient wind?



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· Can you state the reason for the differences in atmospheric circulation between northern hemisphere and southern hemisphere?

· Can you distinguish between SW monsoon and NE monsoon?

4.12 REFERENCES








Delhi, 1987



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LESSON 5 - ATMOSPHERIC DISPERSION Contents 5.0 Aims and objectives

5.1. Atmospheric dispersion 5.2. Atmospheric stability 5.3. Role of atmospheric stability in dispersion 5.4. Plume behavior 5.5. Mixing height 5.6. Stack height 5.7. Gaussian plume dispersion model 5.8. Wind rose 5.9. Let us sum up 5.10. Lesson-end Activities 5.11. Points for Discussion 5.12. Check your Progress 5.13. References

5.0 AIMS AND OBJECTIVES

In the preceding lessons, we have learnt the composition, structure and properties of atmosphere. We learnt the governing factors of the atmospheric processes. We learnt both chemical and physical processes in detail.

In this lesson, how the atmosphere plays a vital role in diluting the pollutants. The

pollutants released by various sources are transported horizontally by the prevailing winds. While they are transported, they are also dispersed vertically as well as laterally. The atmospheric stability governs the dispersion of the pollutants. We will be learning the dispersion process in details.

5.1 ATMOSPHERIC DISPERSION

The title of this paper is “Air pollution and Management”. We must learn atmospheric processes that determine the concentration of air pollutants emitted into it. Atmospheric dispersion is the ability of the atmosphere to disperse the air pollutants and dilute them over a given period of time at a given geographical area.

Why should the pollutants be dispersed? Pollutants are released by various sources either continuously or irregularly and either in large quantities or in small quantities. When they are present in atmosphere in such concentrations and for such durations, may cause adverse effects on humans, plants, animals and materials. Hence, the dispersion of these pollutants is essential and desirable.

How are they dispersed? Prevailing winds carry and transport the pollutants horizontally away from the source and its vicinity. While they are transported they may diffuse laterally as well as vertically. This makes the concentration to become less and



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less. That is the pollutants are diluted to such level not to cause adverse effects. The diluted pollutants may be removed from atmosphere by natural atmospheric cleansing mechanisms.

Now, in this section, we shall learn how these pollutants are dispersed. Two factors play important roles in dispersion: one is wind speed and its direction, another is the atmospheric stability.

We have already learned how winds are generated. The prevailing winds will transport the pollutants horizontally. Greater the wind speed, greater the distance the pollutants are transported. Speed of the wind is determined by the strength of the pressure gradient force. As the pressure gradient force varies temporally and seasonally as well as spatially, the speed of the wind also varies.

As the location of high pressure and low pressure regions change over time, the direction of the wind also changes. In meteorology, the direction of wind is the direction from which the wind blows. Presence of physical barriers will change the direction of the flow of the winds.

Over a geographical area, the surface winds may blow at any speed and from any direction in a given time. When we consider a long period of time, say, a month or a season, over that place, you will get the information about the wind speed and direction that prevailed during that time period. This information can be presented in a diagram called wind rose. This information will be helpful in locating new industries at a location so as to avoid or minimize the effects of pollutants on residents of a densely populated area. We shall see in detail the method of drawing a wind rose later in this chapter.

5.2 ATMOSPHERIC STABILITY

The stability is an important factor determining the diffusion of the pollutants. What is stability? It is the tendency of the atmosphere to resist or enhance vertical motion. It is determined by vertical temperature change in the atmosphere and the speed of the wind. There are basically three types of stability viz. unstable condition, stable condition and neutral condition. Lapse rate: before understanding the stability conditions of the atmosphere, one should be familiar with lapse rate. Lapse rate is defined as rate of decrease of an atmospheric variable with height. Temperature is a variable decreasing wi th t h e height of the atmosphere. It is an important property of troposphere. However, this rate may change diurnally, monthly and seasonally at a given location. Environmental lapse rate / Ambient lapse rate (ELR): it is the actual temperature at each level vertically. It is the rate of decrease of temperature in the actual atmosphere vertically.

Adiabatic lapse rate: when a parcel of air moves vertically, its temperature will decrease without exchange of heat (adiabatically) to its surrounding air as it rises up. The rate of decrease of temperature of a rising parcel of air vertically is called adiabatic lapse rate.



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Dry adiabatic lapse rate (DALR): when a dry parcel of air (without moisture content) moves upward, its temperature decreases without exchange of heat to the surrounding atmosphere (adiabatic). The rate of decrease of temperature of a rising dry parcel of air is called dry adiabatic lapse rate. The rate of decrease of temperature of a rising dry parcel of air is calculated and determined as -0.98 °C per 100 m (= -9.8 °C per km). For practical purposes, it can be approximated to be -1 °C per 100 m (= -10 °C per km). Saturated adiabatic lapse rate / wet adiabatic lapse rate (SALR): when a rising parcel of air is saturated with water vapor, the temperature will decrease and at the same time water vapor will condense. The condensation of water vapor will release latent heat and this will heat the air parcel. Consequently the lapse rate of the rising parcel air will be different from that of DALR. The saturation lapse rate is determined as -0.44 °C per 100 m (= -4.4 °C per km) at 20 °C of atmospheric temperature. The rising parcel of air may not be saturated with water vapor all the time, but some amount of water vapor will be present in it. This will alter the lapse rate accordingly. Self-check Exercise 18

1. Define the following: a) Dry adiabatic lapse rate b) Environmental lapse rate c) Wet adiabatic lapse rate

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Stable condition in the atmosphere: stability of the atmosphere is its resistance to the vertical movement of air parcel. It does not allow the air parcel to move either upward or downward but to allow the parcel to remain at the same position. Even though a parcel of receives some upward force, it will return to its original position from where it was released.

When the environmental lapse rate is less than the dry adiabatic lapse rate (DALR) the condition is said to be “subadiabatic” or “stable atmosphere”. Under this condition, when a parcel of air rises up, it will cool down adiabatically but the surrounding atmosphere at this level will be relatively warmer than the air parcel. As a result, the risen parcel of air will tend to sink until it reaches its original level where from it was released.

DALR

ELR

Figure 5.1 a. Stable Atmosphere



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Unstable atmosphere: when environmental lapse rate is greater than the dry adiabatic lapse rate, the environmental temperature decreases faster with height and this condition is called “super adiabatic” or unstable condition. Under this condition, when the parcel of air moves up it will cool down adiabatically but the surrounding atmosphere will be relatively cooler. This will cause the risen parcel of air to further move up. This condition favors the pollutant dispersion.

Neutral atmosphere: when environmental lapse rate and dry adiabatic lapse rate are equal, then the atmosphere is said to be neutral. When a parcel rises up, it will cool down adiabatically. If the temperature attained after cooling by the air parcel is higher than the surrounding air, it will rise up further. If the temperature of the rising parcel of air is same as the surrounding air, then the parcel will not rise. However, if the parcel is forced to move up, it will rise. Inversion: when temperature increases with height, the environmental lapse rate becomes just opposite. This condition is extremely subadiabatic. Under this condition, vertical movement of air parcel is prohibited as the rising air parcel will become cooler than surrounding warmer atmosphere.

· Inversions occur during night or early morning hours · Inversions are more frequent during the fall than during other seasons · When inversions accompany low wind speeds (7 mi/hr) – limited horizontal and

vertical dispersion Sometimes, vertical temperature gradients are grouped to result in combination of different stability conditions. Ground based inversion with elevated neutral or unstable condition aloft: at times, inversion layer exists near the ground and either neutral or unstable condition exists above

Figure 5.1 b unstable atmosphere

DALR

ELR

DALR

ELR

Figure 5.1 c Neutral atmosphere



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it. Under these circumstances, if the air parcel is released within the inversion layer it will tend to sink and if it is released above the inversion layer, it will behave accordingly (rise further). Neutral or unstable near the ground with inversion aloft: sometimes, the neutral or unstable condition exists near the ground and inversion above it. Under these circumstances, if the air parcel is released within the neutral or unstable layer, the parcel will tend to move upward until it reaches the bottom of the elevated inversion layer. If the air parcel is released above the inversion layer it will remain at the same level.

5.3 ROLE OF ATMOSPHERIC STABILITY IN DISPERSION

The stability of the atmosphere determines the strength of dispersion of the pollutants vertically. Stable atmosphere and inversion inhibit the vertical dispersion of the pollutants while unstable and neutral conditions favor the vertical dispersion. The reasons are already mentioned above.

Figure 5.1 d Ground based inversion and neutral aloft

DALR

ELR

DALR

ELR

Figure 5.1 e Elevated inversion and neutral/unstable near ground



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The wind speeds and existing stability determine the overall dispersion both vertically and horizontally. Greater the wind speed, farther the pollutants will be transported horizontally. If low wind speed accompanies stable atmosphere or inversion, less or no dispersion of pollutants will occur. Under these circumstances, the concentration of the pollutants will build up if they are released continuously. It will result in high pollution potential. Self-check Exercise 19

Briefly describe the stability conditions of the atmosphere. Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 5.4 PLUME BEHAVIOR

The plume of the released pollutants will be dispersed differently. Various types of plume behavior are illustrated in the figure 5.2.

Fanning: The plume has a large spread horizontally and very little vertically. This typically occurs at night in a very stable boundary layer with strong surface inversion and weak variable winds. The inversion does not permit the vertical movement of the plume (air parcel) and hence, no dispersion or little dispersion vertically.

Fumigation: When the plume material gets rapidly brought down to the ground level due to downward mixing, it is called fumigation. This situation occurs shortly after sunrise due to surface heating and is slowly replaced by an unstable layer that grows up to the top of the plume. This condition is usually short- lived but results in the highest ground level concentrations.

Looping occurs in very unstable and convective conditions during midday and afternoon. Large convection eddies take the plume material in successively upward and downward motions. The atmosphere is unstable which permits and encourages the vertical movement of plume to a greater extent. During this atmospheric condition, the large convective eddies are formed. These eddies take the plume up and down vertically as it disperses vertically.

DALR

ELR



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Figure 5.2 Atmospheric stability and plume behavior

Coning This is when the plume looks like a cone in both the horizontal and vertical scale. This usually occurs under cloudy and windy conditions.

Lofting The plume stays above the surface inversion. This occurs shortly after transition from unstable to stable conditions near sunset. The plume can be thin or become quite thick. Depending on the height of the stake and the rate of deepening of the inversion layer the lofting condition may be very transitory or it may persist for several hours.

Trapping (Not shown in diagrams) Plumes released in unstable atmosphere disperse their material uniformly throughout the air (the Planetary Boundary Layer PBL). Trapping can lead to very high ground level concentrations when the inversion layer is low and there are weak winds.

DALR

ELR



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State the reasons for 1. Fanning plume 2. Looping plume 3. Lofting 4. Trapping

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 5.5 MIXING HEIGHT

Mixing height is the vertical distance above the earth’s surface at a given location and at a given time for the mixing of pollutants. In other words, mixing height is the thickness of atmospherc layer measured from the surface upward, through which pollutants are presumed to mix by virtue of convection caused by daytime heating at the surface. Mixing height vary diurnally, daily, monthly and seasonally. They also vary depending upon the topographic features.

The extent of mixing height determines the strength of dispersion of pollutants vertically. However, low mixing heights with strong winds have the same effect on pollution transport as light winds with larger mixing heights. In air pollution potential forecasting, the ventilation index (the product of mixing height and average wind speed) is generally employed. Ventilation coefficient determines the air pollution potential of a given place. High air pollution potential is the occurrence of high concentration of pollutants due to low dispersion of the pollutants.

Mixing heights are not measured directly but are determined from the vertical

temperature distribution with assumption that in thoroughly mixed unsaturated atmosphere the temperature lapse rate is “dry adiabatic”. The morning mixing height is the height above ground level where dry adiabatic extension of the morning minimum surface temperature plus 5 °C (this addition is done for urban areas) intersects the vertical temperature profile near sunrise that morning (00 Z). 5 °C is added to incorporate urban heat island effects.

Afternoon mixing height is computed in the same way from the afternoon maximum surface temperature. While calculating the afternoon mixing height, there is no need for adding any extra value with the maximum temperature value. Self-check Exercise 21

Briefly describe the concept of mixing height. Note: Please do not proceed unless you write answers for the above two in the space given below:



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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5.6 STACK HEIGHT Stack height: stack height is the height of the stack of a source. The source is usually an industry or industrial complex. The stack is the physical provision through which the air pollutants are emitted / released into the atmosphere. It is also called chimney.

Earlier, people thought greater the height of the stack, the farther the pollutants will be transported and diluted before reaching the ground level. However, in Western Europe and North America, the tall stacks created yet another problem – acid rain over the downwind localities. The taller stacks transported the pollutants to farther distances but during transportation, they underwent chemical transformation to form acid rain in the places/countries located in the downwind.

Stack height is an important parameter in calculating the downwind concentration of the pollutants emitted. No doubt, tall stacks will transport the pollutants to longer distances than the short stacks. While stack height is considered, we should bear in mind that there are two stack heights of the same stack. One is “physical stack height” and another is “effective stack height”. Physical stack height: it is the height of the stack measured from the surface of the ground till the top edge of the stack. It is denoted by h. Effective stack height: it is the physical height plus plume rise. What is plume rise? When pollutants are emitted from the stack they (hereafter, we shall call them “plume”) go upward to a certain height due to forced ejection and being warmer than the atmosphere. The height up to which plume rises above the top edge of the stack is called plume rise. After rising to this level, the plume will take a bend due to prevailing wind and transported horizontally in the downwind direction. The plume rise is symbolized by h. Now, h + h will yield H, the effective stack height.

H = h + h

For calculating plume rise several equations are available. If you are interested you may go through the text books dealing with this subject.

Figure 5.3 a Effective stack height



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Figure 5.3 b Plume rise and Effective stack height Self-check Exercise 22 Briefly describe the Effective stack height. Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5.7 GAUSSIAN PLUME DISPERSION MODEL

It is a model used to determine the concentration of the pollutant(s) at any point in the downwind direction. It is based on normal distribution (Gaussian distribution) of the observations in a data set. Here concentration values are the observations of the normal distribution. It is assumed that the centerline of the distribution will have the maximum



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Figure 5.4 Gaussian plume dispersion model

concentration while areas away from centerline will have minimum concentration. Concentration will decrease as one goes away from the centerline.

Where,

C = ground level concentration at some distance x downwind (g/m3) Q = Average emission rate (g/sec) u = mean wind speed (m/sec) H = Effective stack height (m) σy = standard deviation of wind direction in the lateral (m) σy = standard deviation of wind direction in the vertical (m) y = off-centerline distance (m) e = natural log equal to 2.71828

This equation is the general equation. It can be modified to suit local conditions. Further this equation can be modified according to the requirement. For example, to compute ground level concentration alone, the equation will become simpler than this.

In this model, the dispersion coefficients, σy and σz are used. These are the standard deviation values in lateral and vertical directions respectively. These values cannot be



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determined directly. Pasquill and Gifford have developed the curves called P-G curves for determining these σy and σz values.

Distance, x m

σσyy

Figure 5.5 a P-G curves for y-coordinate



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Write the equation of Gaussian dispersion model. Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 5.8 WIND ROSE

Wind rose is a diagrammatic representation of wind data over a period of time in a given place. It represents the speed and direction of the wind blown. A typical wind rose is presented in the following diagram.

Distance, x m

σσzz

Figure 5.5 b P-G curves for z-coordinate



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It is a frequency distribution of the wind classes grouped based on wind speed and direction. Here wind direction is the direction from which the wind is blowing. Wind rose diagrams are useful in knowing the predominant wind direction and the strength of the wind over a place. Wind roses will differ monthly and seasonally. They may also vary between day time and night time. It represents climatology of a location with reference to wind speed and wind direction. Using the wind data of a place over a period of time, we can prepare the following wind roses:

· Daytime wind roses · Nighttime wind roses · Monthly wind roses · Seasonal wind roses · Wind roses under different stability conditions

From the wind rose, we may infer the downwind locations that will be affected by the

air pollutants. We can also decide the location of any proposed industry in such a way that the highly populated area is not affected.

Figure 5.6 Wind rose

In the above wind rose diagram, the predominant wind direction was west. The

maximum wind speed attained was 20-25 km/h.



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Wind rose diagrams will be useful while predicting the pollutant concentrations using Gaussian plume dispersion equations. Wind roses are used to determine the average wind speed for the winds blowing from a given direction. This average value is used in Gaussian plume dispersion model. The downwind direction is also determined from wind rose diagram; for each direction, corresponding downwind direction will be chosen and pollutant concentration will be predicted in that downwind direction. In this way, pollution concentrations can be determined for all the wind directions and corresponding downwind directions. The predicted values can be plotted on the map to prepare pollution isopleths. Self-check Exercise 24

Explain the concept of wind rose diagram. Describe the importance of wind rose diagram. Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… 5.9 LET US SUM UP

In this unit we have learned atmosphere, its composition, it chemical and elemental properties. Now you must be familiar with vertical layers of the atmosphere and vertical temperature variations. We learned important atmospheric parameters like temperature, humidity, pressure, rainfall, winds etc. We have also learned the general circulation of atmosphere existing over the globe and their deviations at regional and local levels. The brief details of monsoon are also discussed.

We understood the role of atmosphere in dispersing the pollutants released. Atmospheric pollutants, once emitted into the atmosphere, will be under the influence of atmospheric processes either to dilute and bring them to a level that is harmless or less harmful or to build up the concentration under worse conditions, to make them harmful.

We came to know how the stability conditions of the atmosphere determine the

extent of dispersion. We learnt the behavior of plume under different stability conditions. We learnt the dilution potential of the atmosphere and how the pollutants are dispersed.

We learned the concept of the mixing height. We are able to learn the plume rise

and effective stack height. We also learnt how to predict the resultant concentration of the emitted pollutant using Gaussian dispersion model. We are introduced to the Gaussian plume dispersion model.

The model we studied in this lesson is the basic model. This model is modified

accordingly to suit the particular place as the atmospheric conditions, terrain conditions vary from place to place. The model also can be simplified to compute plume centerline concentration and ground level concentration only.

We learned the concept of wind rose diagram and its usefulness in pollution dispersion studies. Wind roses are used to determine the average wind speed for the winds



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blowing from a given direction. This average value is used in Gaussian plume dispersion model. The downwind direction is also determined from wind rose diagram; for each direction, corresponding downwind direction will be chosen and pollutant concentration will be predicted in that downwind direction. In this way, pollution concentrations can be determined for all the wind directions and corresponding downwind directions. The predicted values can be plotted on the map to prepare pollution isopleths.


· Take a sheet of paper and draw the various stability conditions · Draw plume behavior under various stability conditions · Draw the stack and label the physical stack height and effective stack height · Draw the plume dispersion diagram

5.11 POINTS FOR DISCUSSION You have learnt so many things in this lesson. You know how the atmospheric stability influences the dispersion of pollutants in the atmosphere. Stability of the atmosphere determines the plume behavior. Mixing height limits the vertical dispersion of pollutants. Wind rose diagram is helpful in locating the industries and planning. Wind rose is also helpful in atmospheric dispersion calculations using Gaussian dispersion model. 5.12 CHECK YOUR PROGRESS

· Can you describe the dispersion of pollutants under different stability conditions?

· Can you draw the wind rose? · Can you explain the Gaussian plume dispersion model?

5.13 REFERENCES


2. Miller, Jr., G.T. Environmental Science, Thomson Brroks/Cole, CA, USA, 2004 3. De, A.K. Environmental Chemistry, New Age International Ltd, Publishers, New

Delhi, 1994 4. Rao, M.N. and Rao, H.V.N. Air pollution, Tata McGraw-Hill Publishing Co. Ltd.,

New Delhi 5. Stern, A.C. Air pollution, Academic Press, Inc., New York, 1976 6. Wark, K. and Warner, C.F. Air pollution – its origin and control, IEP A Dun-

Donnelly Publisher, New York, 1976 7. W.H.O. Glossary of air pollution, World Health Organization, Copenhagen, 1980 8. www.en.wikipedia.com 9. Critchfield, H.J. General climatology, Prentice Hall of India Pvt. Ltd., New Delhi,

1987 10. Peavy, H.S., Rowe, D.R. and Tchobanoglous, G. Environmental Engineering,

McGraw Hill Book Company, New York, 1985.



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UNIT – II LESSON 6 – HISTORY OF AIR POLLUTION Contents 6.0 Aims and objectives

6.1. Introduction – Brief history of atmosphere 6.2. What is air pollution 6.3. History of air pollution

6.3.1. History of air pollution around the world 6.3.2. History of air pollution in India

6.4. Sources of air pollutants 6.5. Let us Sum Up 6.6. Lesson-End Activities 6.7. Points for Discussion 6.8. Check your Progress 6.9. References

6.0 AIMS AND OBJECTIVES In the last unit we have learnt about atmosphere, its characteristics, its properties and processes that take place in atmosphere. Now, we are ready to learn about pollution in the atmosphere. Atmosphere contains its own natural constituents and any deviation from its natural composition results in pollution – air pollution. Mostly this deviation occurs in the form of contaminants released into it. When the contaminants cause any harmful effects, then it is called air pollution and the contaminants are called air pollutants. In this lesson we are going to learn, what is air pollution? How did this problem become popular? How did people become so concerned about it? What are the places get affected? How many people were affected in the past? You will get answers for all the above questions in this lesson. 6.1 INTRODUCTION – BRIEF HISTORY OF ATMOSPHERE

In the last unit, we have learned that our earth is surrounded by a thin layer called, atmosphere. We have also learned the natural constituents of the atmosphere – the names of constituents and their average volume in the atmosphere. However, the present composition of atmosphere is the result of processes occurred during the span of geological eras. The atmospheric composition was different from what is today than in the geological past. Today’s atmospheric composition has resulted from the changes occurred in the past two billion years or more. It was the time when first aerobic organisms came into existence. These aerobic organisms modified the atmosphere into its present state – that is present composition.



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The primeval gaseous atmosphere did not contain oxygen. Oxygen started accumulating due to photosynthesis by non-oxygen dependant species lived in those times. In addition to this, earth’s atmosphere has undergone other changes too. A notable change is the concentration of carbon dioxide which has undergone considerable changes.

In general, air pollution can be defined as any change in the atmospheric constituents and/or its composition. You may wonder when atmosphere has undergone changes in the past then why should we be concerned about the change in its constituents taking place at present. The reason is that those changes took place over the span of few billions years; while the changes that we refer to as air pollution take place in a very short time i.e. within a decade or century. A century is a very short period of time when compared to a million year or a billion year. Such drastic changes in a short time pose great challenges to all of the living organisms and in particular to the human beings. That is the reason we are more concerned about air pollution and its effects.

6.2 WHAT IS AIR POLLUTION What is air pollution? Before understanding air pollution, let us learn what

pollution is. Pollution is to make unclean. A comprehensive definition was given by Odum (1971): “Pollution is an undesirable change in the physical, chemical, or biological characteristics of our land, air or water that may or will harmfully affect human life or that of desirable species”. This definition includes all kinds of pollution.

Now let us turn our attention towards air pollution. Air pollution is defined as “the presence in the outdoor atmosphere of one or more contaminants such as dust, fume, gas, mist, mist, odor, smoke or vapour in quantities, of characteristics, and of duration such as to be injurious to human, plant or animal life or to property, or which unreasonably interferes with the comfortable enjoyment of life and property” (Bishop, 1957). Self-check Exercise 1

Define air pollution Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

6.3 HISTORY OF AIR POLLUTION



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Air pollution has gained importance recently in India, especially after “Bhopal tragedy”. In the world, it has become important after the events of acid rain in Nordic countries, London smog and Los Angeles smog episodes.

Wood was the prime source of energy in the past. After the discovery of coal, it gradually replaced wood and became the dominant source of energy. However, initially people were reluctant in using coal. Air pollution by coal has become a major issue since the beginning of 14th century. It continues to be a major problem till today as coal is the dominant fuel for energy production in many parts of the world.

6.3.1 HISTORY OF AIR POLLUTION AROUND THE WORLD

In Great Britain, there were recorded oppositions for the use of coal due to its smoke and related problems during the reigns of Edward I (1272-1307) and Edward II (1307-1327). In England Richard III (1377-1399) levied tax on the use of coal and Henry V (1413-1422) appointed a Commission to oversee the movement of coal into the city of London. Sporadically, there were oppositions for the use of coal due to smoke.

In 1661, as per Royal Command of Charles II a pamphlet was published on usage of coal and its impact. Some remedial measures also were suggested in that publication. In 1819, a Select Committee of the British Parliament was appointed to study and report the control of smoke from burning of coal.

Acid rain was first found in Manchester, England. In 1852, Robert Angus Smith found the relationship between acid rain and atmospheric pollution.

In Great Britain, the term smog was coined as a derivative of “smoke-fog”. This term was first used by H.A. Des Voeux in 1911 in his report to the Manchester Conference of the Smoke Abatement League of Great Britain on the deaths caused by smoke-fog in Glasgow, Scotland in 1909. About 1063 deaths were reported to have occurred in 1909 due to the noxious conditions created by smoke and fog.

Large number of people died due to smoke in December, 1952. This led the Government to take steps for control of smoke. In 1952, about 4,000 deaths were reported in London due to existence of yellow fog lasted 5 days. It prompted the Parliament to pass the “Clean Air Act of 1956. Similar disasters were reported killing 2,500 people during 1956, 1957 and 1962. Due to enactment of stringent pollution laws in U.K., the air in London is much cleaner at present.

Although similar large scale deaths due to coal burning were not reported in other parts of the world, discomfort, respiratory illness, and even deaths in small numbers were reported. Sulfur dioxide, sulfur trioxide, tar, soot and ash particles emitted by burning of coal are attributed to the illness and deaths.

Large industrial cities such as Pittsburgh, Pennsylvania, and St. Louis, Missouri were known for their smoky air. By the year 1940s, the atmosphere of some cities in USA



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was so polluted that people had to use their headlights of their automobiles during daytime.

The first documented air pollution disaster in the United States occurred during October 1948, at the town of Donora in Pennsylvania’s Monongahela River Valley south of Pittsburgh. Pollutants became trapped in a dense fog that stagnated over the valley for 5 days. Due to this, about 14,000 people became sick and 22 people died in that town. The killer fog resulted from a combination of mountainous terrain surrounding the valley and weather conditions that trapped and concentrated deadly pollutants emitted by steel mill, zinc smelter and sulfuric acid plant.

In 1950s, the occurrence of photochemical smog in Los Angeles raised concern for the control of air pollution. This smog is different from the smog occurred in London. The details we shall learn later in this unit.

In 1963, high concentrations of air pollutants killed about 300 people in New York City. Episodes of such magnitude in other cities of United States led to strong air pollution control programs in the 1970s.

Coal has been the chief source for smoke and gases in all the industrialized countries for the past 400 years. Still it continues to be a major cause for atmospheric pollution despite the addition of petroleum based fuels and natural gas. As the demand increases, large quantities of all these fuels are being burnt. Coal is being used in India in large quantities for power generation. It is the dominant fuel used in our country for power generation. Self-check Exercise 2

· Who did coin the term “smog”? · What did the term “smog” refer to? · List the major disasters occurred due to air pollution in England with details

of deaths. · When and where did the first air pollution occur in USA?


6.3.2 HISTORY OF AIR POLLUTION IN INDIA

In India, a major disaster occurred in the year 1984, in Bhopal which killed more than 10,000 people within a week. In fact, it was an accident, which released poisonous methyl isocynate (MIC) into the Bhopal atmosphere. The incidence created awareness



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among people about environmental pollution. However, the air monitoring work was started in India in 1978 itself.

WHO / UNEP initiated the air monitoring program in 1973 on global scale to observe trends and to examine the relationship between pollution and human health. Between 1973 and 1975 the project was run on a pilot scale in 15 countries only. Suspended Particulate Matter (SPM) and SO2 were the two air pollutants estimated in selected cities in those countries. In 1976, the project was expanded and merged with the Global Environmental Monitoring Systems (GEMS) and since then, the project has been extended to the developing countries. By this time, the World Meteorological Organization (WMO) also became a partner of this program.

WHO chose India in 1978 as the nodal point in South-East Asia for air monitoring program. The main purpose of the program is to alert the public and authorities about any abnormal increase in pollution levels and to ultimately encourage local agencies to take the program into their hands. Four parameters viz. SPM, SO2, sulfation rate and dustfall were chosen for assessment and monitoring. National Environmental Engineering Research Institute (NEERI) was entrusted under this program. It created the air quality monitoring network covering Madras (Chennai), Bombay (Mumbai), Delhi, Hyderabad, Calcutta (Kolkatta), Kanpur, Nagpur, Ahmedabad, Jaipur and Cochin. Thus, the air quality monitoring program was commenced on a regular basis by NEERI since 1978.

The results obtained from the study led to organizing a “Conference on Air Pollution” in 1982 at Bombay. It revealed the following facts:

1. Lung capacity of children in the age group of 8-10 years was reduced by 20% in Nagpur due to pollution from manganese and power plants.

2. Due to effective pollution control measures undertaken in Bombay, the pollution had been brought down. Chembur which was once considered as “gas chamber” became relatively clean. Emission of SO2 had come down drastically due to measures taken – use of low sulfur fuel, dust control and use of new technology.

Delhi has been the most polluted city with reference to Suspended Particulate Matter

(SPM) concentration. Average concentration in 1990s was reported to be more than 400 µg m-3. Calcutta was ranked second in terms of SPM with the concentration greater than 350 µg m -3. Data published by NEERI in 2002 revealed that Delhi continues to have poor air quality with the highest SPM concentration of about 480 µg m-3.

The recent data collected by UN revealed that India stands at 138th place in terms of

air quality. It is published in Reader’s Digest October 2007 issue. 6.4 SOURCES OF AIR POLLUTANTS

Air pollutants are released by both natural and anthropogenic sources. Natural sources include volcanoes, sea spray, forest fires, dust storms, etc. Major anthropogenic sources are transportation, power generation by combustion of fossil fuels, refuse burning, industrial and domestic fuel burning and industrial processes.



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Though the amounts of pollutants released by natural sources are greater than that by anthropogenic sources, pollution by anthropogenic sources is of great concern. Anthropogenic sources emit pollutants in large quantities within a confined location, for example, an urban area, an industrial town, which result in high concentrations to cause deleterious effects. In addition, anthropogenic sources emit the substances which were not originally present in natural atmosphere. These substances are called “foreign substances”.

The sources can also be categorized as “Stationary sources” and “Mobile sources”. As the name implies, the stationary sources are the ones that stay permanently in their places and emit the air pollutants regularly and/or continuously. Examples of stationary sources include: industries and power plants. Mobile sources are the ones that keep moving from one place to other and during their movement they emit air pollutants into the atmosphere. All the vehicles ply on roads – two-wheelers, three wheelers, cars, buses, lorries, trucks etc., diesel powered trains, air planes, ships and boats etc. are the mobile sources that emit large quantities of air pollutants. Self-check Exercise 3

· Define stationary sources? · Define mobile sources?


6.5 LET US SUM UP In this lesson we have learnt what air pollution is and how it was realized as a serious problem. We also came to know some of the disasters occurred in England and US due to air pollution. We learnt when India started to monitor the air quality and the results of monitoring. 6.6 LESSON-END ACTIVITIES

· Prepare the events on air pollution in chronological order · Compare air pollution disaster in Europe and in US




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· The seriousness of air pollution was realized only after the major disasters in which thousands people lost their lives.

· State which disaster led the Government to pass the legislation in England.

6.8 CHECK YOUR PROGRESS You might have learnt that single disaster occurred in London did not move the Government to act. After occurrence of many such disasters only the Government came forward to pass the legislation and raised the concern over the problem. Clean Air Act , 1956 was enacted after the event of occurrence of smog for 5 days which killed 4000 people in London. The magnitude of air pollution problem was not that acute in United States. The reason is not known. In India, the Bhopal disaster led to the awareness of the whole nation. It also drew the attention of the whole globe.

6.9 REFERENCES



3. Stern, A.C. Air pollution, Academic Press, Inc., New York, 1976 4. Wark, K. and Warner, C.F. Air pollution – its origin and control, IEP A Dun-

Donnelly Publisher, New York, 1976 5. W.H.O. Glossary of air pollution, World Health Organization, Copenhagen,

1980



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LESSON 7 – CLASSIFICATION OF AIR POLLUTANTS

Contents 7.0 Aims and objectives

7.1. Purpose of classification 7.2. Classification of air pollutants

7.2.1. Classification based on physical state 7.2.2. Classification based on chemical properties 7.2.3. Classification based on origin

7.3. Sources of particulates 7.4. Sources of gaseous contaminants 7.5. Let us sum up 7.6. Lesson-end Activities 7.7. Points for Discussion 7.8. Check your Progress 7.9. References

7.0 AIMS AND OBJECTIVES This lesson deals with types of air pollutants and their classification. You are going to learn how the air pollutants are classified. You will be amazed to know at the end of this lesson, the number and types of pollutants released into the atmosphere. You will be able to classify a pollutant under the category it suits. 7.1 PURPOSE OF CLASSIFICATION

First, we should be clear why we should classify the air pollutants. In fact, the air

pollutants are classified for our convenience. Classification will help us to:

· Know the various types of pollutants available · Develop control strategies · Choose appropriate control device · Identify the sources of these pollutants · Understand and anticipate the resultant atmospheric interactions · To relate them with health effects borne by the exposed population

It will give clear idea about each type of pollutant, its chemical and physical

properties and its effects. Each pollutant type / class can be studied separately and we can check whether any similar effects are posed. We can also conclude whether similar control mechanism can be adopted. 7.2 CLASSIFICATION OF AIR POLLUTANTS

Air pollutants are classified in many ways:



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a) based on their physical state, b) based on their chemical properties and c) based on their origin

7.2.1 CLASSIFICATION BASED ON PHYSICAL STATE Based on physical state, the air pollutants are classified as:

1. Particulates: they include both solid and liquid particles. Small solid particles and liquid droplets are collectively known as particlulates. They are present in atmosphere i n fairly large amounts and pose a serious air pollution problem. Particulate pollutants are classified according to their particle size and nature into fumes, dust, ash, carbon smoke, lead asbestos, mist, spray, oil, grease etc.

a. Suspended Particulate Matter: Suspended Particulate Matter (SPM) may

be defined as “all solid and liquid particles in the air that are small enough not to settle out on to the earth’s surface under the influence of gravity”.

b. Respirable Particulate Matter (RPM) or PM10: particles of size less than 10 µm can enter into the lungs. Particulates of this size and below cannot be prevented by the filtering mechanism available in our respiratory tract and hence their entry into the lungs. Special attention is given to RPM due to its potential harm to human respiratory system. It requires highly advanced / expensive method to control these particulates.

c. Dust: dust is made up of solid particles predominantly larger than those found in colloids and capable of temporary suspension in air or other gases. They do not tend to flocculate except under electrostatic forces. They do not diffuse but settle under influence of gravity. (Though the dust can also be included under particulates, it is distinguished from the particulates based on its ability to settle down by gravity).

d. Aerosol: it is a suspension of solid and/or liquid particles having a negligible falling velocity. The size of the particle in an aerosol frequently exceeds the normal colloidal limits (approximately 1 nm to 1 µm).

e. Smoke: fine, solid particles resulting from the incomplete combustion of organic substances such as wood, coal, tobacco. It consists mainly of carbon and other combustible materials. Smoke particles range from 0.5 to 1 µm in diameter.

f. Fume: fumes are fine, solid particles (often metallic oxides such as zinc and lead oxides) formed by condensation of vapors of solid materials. Fumes may be from sublimation, distillation, calcinations, or molten metal processes and they range in size from 0.03 to 0.3 µm. Fumes flocculate and coalesce, then settle out.

g. Fly ash: it consists of finely divided, non-combustible particles contained in the gases arising from combustion of coal. Inherent in coal, these mineral or metallic substances are releases when the organic portion of coal is burned. Fly ash shares characteristics dust, smoke and fumes. Like dust, fly ash particles in size, range from 1.0 to 1000 µm; like smoke, it results from burning; and like fumes, it consists of inorganic metallic or mineral substances.



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h. Mist: it consists of liquid particles or droplets formed by the condensation of a vapor, the dispersion of a liquid, or the enactment of a chemical reaction. Mists are usually less than 10 µm in diameter. If mist concentration is high enough to obscure visibility, then it is called a fog.

i. Spray: it consists of liquid particles formed by the atomization of parent liquids, such as pesticides and herbicides. Spray particles range in size from 10 to 1000 µm.

2. Gaseous contaminants: pollutants that occur in gaseous state are called gaseous

contaminants. These pollutants are gaseous in nature at normal temperature and pressure. Gaseous pollutants are formless fluids that occupy the space into which they are released. They behave like air and do not settle out of the atmosphere. They include a variety of organic and inorganic gaseous materials.

a. Inorganic gases: these include noxious gaseous pollutants like oxides of

nitrogen (NOx), oxides of sulfur (SOx), hydrogen sulfide (H2S), ammonia, chlorine, hydrogen fluoride, hydrogen chloride, oxides of phosphorous, hydrogen cyanide, bromine and mercaptans etc.

b. Organic gases: These pollutants include hydrocarbons (CxHy) such as CH4, C3H8, C2H2, C2H4, C6H6, C8H18 and other compounds such as formaldehyde, acetone vapours, alcohols, organic acids, methyl isocyanate, chlorinated hydrocarbons etc.


· What are the criteria for classifying the air pollutants? · Define particulates · Define smoke · Define fumes · Define fly ash · Define spray · Define mist


7.2.2 CLASSIFICATION BASED ON CHEMICAL PROPERTIES

Based on their chemical properties, the air pollutants are classified as follows.

These may include both particulates and gases.



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1. Sulfur-containing compounds: all air pollutants that contain sulfur atom in their molecular structure are called “sulfur-containing compounds”. Examples are: SO2, SO3, H2S, mercaptans etc.

2. Nitrogen-containing compounds: all the air pollutants that contain nitrogen atom in their molecular structure are called “nitrogen-containing compounds”. Examples are: NO, NO2, NH3 etc.

3. Carbon-containing compounds: all the air pollutants that contain carbon atom in their molecular structure are called “carbon-containing compounds”. Examples are: CO, CO2 etc.

4. Halogen compounds: they include, HF, HCl etc. 5. Radioactive compounds: the substances that are radioactive and airborne are

called radioactive compounds. 7.2.3 CLASSIFICATION BASED ON ORIGIN Based on their origin, the air pollutants are classified as:

1. Primary air pollutant – A pollutant emitted into the atmosphere from an identifiable source. (e.g., CO, SO2, H2S, CO2 etc.)

2. Secondary air pollutant – A pollutant formed by chemical reaction in the atmosphere (e.g., photochemical smog, NO2, O3 etc.)

The source and types of pollutants are illustrated in the figure 7.1.

7.3 SOURCES OF PARTICULATES Several natural processes such as volcanic eruptions, dust storms, wind-driven dust from soil, sea spray etc. release huge quantities of particulates (800-2000 million tons each year) into the atmosphere. The anthropogenic sources include power plants, smelters,

Air Pollutants

Gaseous

pollutants

Particulate

pollutants

Aerosol

pollutants Pesticides Metallic

contaminants Carcinogens Radioactive

pollutants

Biological

contaminants

Organic Gases

Inorganic

Gases

Natural sources

Manmade sources

Figure 7.1 – Classification of air pollutants



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mining operations, industrial processes, etc. The anthropogenic sources of particulates are described in table 7.1. It has been estimated that combustion, industrial processes and miscellaneous sources contribute almost about 600-1350 million tons per year. Metal oxides comprise a major class of inorganic particulates in the atmosphere. They are produced when metal-containing fuels are burnt. Formation of H2SO4 droplets generates aerosol mists in the atmosphere. If basic substances such as NH3 or CaO are present in the atmosphere, the H2SO4 will react to form salt particles such as (NH4)2SO4

and CaSO4. These salts may present in dissolved form (mist) or they may get dried by sunlight to appear as solid salt particles. Atmospheric particulates may comprise a variety of organic and inorganic chemical compounds and radionuclide. The sources of particulates are presented in table 7.1. Table 7.1 – Sources of particulate emissions

Sources Examples

Combustion Fuel burning (coal, wood, fuel oil) Incineration Others – open fires, etc.

Materials handling & processing Loading & unloading Crushing & grinding Cutting & forming

Earth moving operations

Construction (road, buildings, dams, etc.) Mining Agriculture

Miscellaneous House cleaning Mud road cleaning Engine exhaust, etc.

7.4 SOURCES OF GASEOUS CONTAMINANTS Gaseous contaminants are released by a wide variety of sources. They include both natural and man-made sources. Volcanic eruptions, biological processes, lightning, forest fires and oceans are major natural sources. Major man-made sources are combustion of fossil fuels, chemical processes in industries, incineration and sewage treatment processes. The sources and their contributions are presented in table 7.2 Table 7.2 Summary of sources and their contributions of gaseous contaminants



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Estimated annual emissions (tons) Gases

Man-made sources

Natural sources

Man-made Natural

SO2 Combustion of coal and oil

Volcanoes 1.46 × 106 1.5 × 106

H2S Chemical processes and sewage treatment

Volcanoes, biological action in swamps

3 × 106 1.0 × 104

CO Incomplete combustion

Forest fires 2.75 × 108 7.5 × 107

NO & NO2 Combustion Lightning, bacterial action in soil

5.3 × 107 10.9 × 108

NH3 Sewage treatment Biological decay

4.0 × 105 1.16 × 109

N2O ---- Biological action

---- 5.9 × 108

Hydrocarbons

Incomplete combustion, chemical processes

Biological processes

8.8 × 107 4.8 × 108

CO2 Combustion Biological processes, oceans

1.4 × 1010 1012

7.5 LET US SUM UP In this lesson we have learnt the types of pollutants and their classification. We learnt that classification is done based on physical, and chemical properties and their origin. We also learnt the sources of each type of pollutant. Self-check Exercise 5

· What are the criteria for classifying the air pollutants? · Define primary pollutant · Define secondary pollutant




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· Take a sheet of paper and write down the names of air pollutants you know. · Categorize them based their physical state · Categorize them based their chemical properties · Categorize them according to the way they are released

7.7 POINTS FOR DISCUSSION You might have understood that a wide variety of substances in various forms are released into the atmosphere. You might have been amazed to note that huge amounts of contaminants are released by man-made sources. List out the sources and their estimated emissions. 7.8 CHECK YOUR PROGRESS

· Are you able to point out the class / category of a contaminant the moment you hear the name of the contaminant?

· Can you guess the possible source of a pollutant when you hear the name of the pollutant?

7.9 REFERENCES




Donnelly Publisher, New York, 1976 5. W.H.O. Glossary of air pollution, World Health Organization, Copenhagen,

1980



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LESSON 8 - EFFECTS OF AIR POLLUTION ON HUMAN HEALTH Contents 8.0 Aims and objectives

8.1. Introduction 8.1.1. Routes of entry

8.2. Health effects 8.2.1. Health effects of particulates 8.2.2. Defense mechanism of human respiratory system and entry mechanism of

the particulates 8.2.3. Health effects of gaseous contaminants

8.2.3.1.Health effects of carbon monoxide 8.2.3.2. Health effects of Sulfur dioxide 8.2.3.3. Health effects of oxides of nitrogen 8.2.3.4. Health effects of ozone and PAN 8.2.3.5.Health effects of other air pollutants

8.3. Let us sum up 8.4. Lesson-End Activities 8.5. Points for Discussion 8.6. Check your Progress 8.7. References


Human beings breathe air continuously throughout our life. While breathing, we inhale the surrounding air and its constituents. The air may contain both particulates and gaseous contaminants. The definition of air pollution clearly states that the presence of contaminant(s) causing harmful effects is air pollution.

In this lesson we are going to learn how these effects are caused and manifested.

We will also be learning the chemical substances causing the adverse effects. 8.1 INTRODUCTION

We, human beings depend on atmosphere for our metabolic requirements and for our comfort. We inhale and exhale air almost ceaselessly throughout our life until our death. This process is called breathing; biologically, called respiration. An average man breathes 22,000 times a day and takes in about 16 kg of air daily. We use oxygen for metabolism and exhale carbon dioxide into the atmosphere.

During inhalation, we also take other impurities present in air along with. The impurities may be of natural origin like pollens, natural allergens, dust particles etc. or may be introduced by pollution. The impurities entering into the human lungs may affect in various ways. All the impurities entering do not necessarily cause harm however. The effects caused by the inhaled impurities (pollutants) depend upon various factors:

1. Nature of the pollutants 2. Concentration of the pollutants



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3. Duration and frequency of exposure 4. State of health of the receptor and 5. Age group of the receptor

The chemical nature of the pollutants determines the type and extent of the health

problem posed. The physical property such as size and shape of the particle also is important factor in causing the effect.

Concentration of the pollutants determines the magnitude of the harm. Generally, concentrations that are low may produce little or no effect. Duration and frequency of exposure by the individual and concentration are important factors that determine the effect. The effects may be of acute in nature of chronic one.

It is well known that the young children, old persons, people already with certain illness / sickness and infirmity are highly susceptible to the effects of air pollution. 8.1.1 ROUTES OF ENTRY Air pollutants may enter man through:

1. Exposed skin 2. Eyes 3. Nose (also orally while opening the mouth) 4. Skin (this route is not important except in case fumes and vapors)

Of the above three routes, air pollutants enter predominantly in large quantities

through nose and reach the throat, larynx, tracheo-branchial tree and finally lungs. From lungs they may enter the blood stream and reach other tissues. Some irritants may even reach the mucosa of the digestive tract. Self-check Exercise 6

· How do the air pollutants enter into human beings? Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

8.2 HEALTH EFFECTS

Air pollutants pose a variety of problems and cause a number of effects. The list of the effects is given below:



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1. Eye irritation 2. Nose and throat irritation 3. Irritation of the respiratory tract 4. Nuisance by odor from gases like H2S, NH3 and mercaptans even at low

concentrations. 5. Increase in mortality and morbidity rates 6. A variety of particulates particularly pollens are known to initiate asthmatic

attack 7. Chronic diseases such as bronchitis and asthma may get aggravated by high

concentration of SO2, NOx, photochemical smog and particulates 8. Carbon monoxide readily combines with hemoglobin. It has 200 times greater

affinity to Hb than that of oxygen. It causes anoxic conditions, and may result in death when an exposure to > 750 ppm is encountered. At lower concentrations, it increases stress, headache, drowsiness, fatigue etc.

9. Hydrogen fluoride will cause fluorosis 10. Certain pollutants are carcinogenic in nature. Exposure to such pollutants will

result in cancer. 11. Dust particles may cause respiratory diseases (silicosis, asbestosis, etc.) 12. Heavy metals in the form of particles or vapor entering the lungs will be

poisonous.

It is difficult to explain each effect by different pollutants and out of the scope of this paper. Therefore, we shall limit our discussion to few of the effects.

8.2.1 HEALTH EFFECTS OF PARTICULATES

The table 8.1 lists the effects of particulate matter on human health

Table 8.1 – Health effects caused by particulate matter Concentration, µg m -3

Accompanied by Time Effects

750 715 µg m -3 SO2 24 h average Considerable increase in illness

300 630 µg m -3 SO2 24 h average Acute worsening of chronic bronchitis patients

200 250 µg m -3 SO2 24 h average Increased absence of industrial workers

100-130 120 µg m -3 SO2 Annual mean

Children likely to e x p e r i e n c e i n c r e a s e d incidence of respiratory diseases

100 Sulfation rate above 30 mg/cm2/mo

Annual geometric mean

Increased death rate for those over 50 likely

80-100 Sulfation rate above 30 mg/cm2/mo

2-yr geometric mean

Increased death rate for those 50 to 69 years



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The fine particles with size less than 3 µm can penetrate into the deep air passages

of lungs and cause damage to lungs. Once, they reach the lungs, they are not removed. Hence they remain lodged in lungs. They cause severe breathing trouble by physical blockage and irritation of the lung capillaries. Black-lung disease, pulmonary fibrosis and emphysema are examples of lung damage.

Fortunately the human beings possess certain defense mechanisms to prevent the

entry of foreign particles into their respiratory tract. They are described in table 8.2. Coarse particles are trapped in the nose and throat and eliminated. When fine particles enter the defense mechanism fails to prevent them. Consequently, the entered particles cause adverse effects.

The effects become multiplied when other harmful gases like SO2 are also present

with particles in the atmosphere.

Table 8.2 – Respiratory defense mechanisms in human beings Particle size Description Defense mechanism Over 10 µm Coarse dust, fly ash

(visible to naked eye) Hairs at the front of the nose remove all particles over 10 µm

2-10 µm Fumes, dust, smoke Movement of cilia sweeps mucus upward, carrying particles from windpipe to mouth, where they can be swallowed

Less than 2 µm Aerosols, fumes L y m p h o c y t e s a n d phagocytes in the lung attack some submicron particles


· What are the effects of particulates on human health? Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 8.2.2 DEFENSE MECHANISM OF HUMAN RESPIRATORY SYSTEM

AND ENTRY MECHANISM OF THE PARTICULATES



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a) Particulates, in general, range in size from 0.0002 µm to 500 µm b) Larger particulates (> 3 µm) are trapped in nose and throat from which they are

easily eliminated c) Fine particulates (< 3 µm) can penetrate into deep air passages and cause lung

damages d) The lodged particles in the lungs cause severe breathing trouble by physical

blockage and irritation to the lung capillaries.

The success of the respiratory defense mechanism depends largely on the size of the particles entering into the system and the depth of their penetration. Approximately, 40% of the particles between 1 and 2 µm in size are retained in the bronchioles and alveoli. Particles ranging in size from 0.25 to 1 µm show a decrease retention, because many particles in this range are breathed in and out again. However, particles below 0.25 µm show another increase in retention due to Brownian motion, which results in impingement.


· Relate the particle size and effects on human health Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

8.2.3 HEALTH EFFECTS OF GASEOUS CONTAMINANTS It will be overwhelming to describe the effects of each gaseous pollutant. Hence, we will be limiting the effects to a certain pollutants only. 8.2.3.1 HEALTH EFFECTS OF CARBON MONOXIDE

As mentioned above, CO combines with hemoglobin to form COHb. Due to its stronger affinity (> 200 times than that of oxygen) towards Hb, it readily combines with Hb even at very low concentrations. As a result, hemoglobin to combine with oxygen is less available or not available leading to anoxic conditions. The effects due to the formation COHb are presented in table 8.3.

Table 8.3 – Health effects of CO Hb COHb level in % Effects < 1.0 No apparent effect 1.0 – 2.0 Some evidence of effect on behavioral response



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2.0 – 5.0 Effects on Central nervous system; impairment of time interval discrimination, visual acuity, brightness discrimination and certain other psychomotor functions

> 5.0 Cardiac and pulmonary functional changes 10.0 – 80.0 Headaches, fatigue, drowsiness, coma, respiratory failure, death CO poisoning will have initial effect of loss awareness and judgment. It is responsible for many automobile accidents as the drivers are exposed to CO while driving. Traffic policemen are severely affected as they are exposed to CO for long duration. Self-check Exercise 9

· What is the mechanism of CO poisoning? Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

8.2.3.2 HEALTH EFFECTS OF SULFUR DIOXIDE Sulfur dioxide is an irritant gas. It affects the mucous membrane when inhaled. Under certain conditions, some of the SO2 is oxidized to SO3 in the atmosphere. Each of these gases, in the presence of water vapor forms surfurous and sulfuric acid respectively. These acid vapors, when inhaled cause corrosive action on mucous membranes. SO3 is a strong irritant and causes severe branchopasms even at relatively low concentrations. SO2 may cause severe problem when it is accompanied by smoke. In 1952, a major disaster occurred with a death toll of 4000 in London, when SO2 accompanied with smoke – a condition is called smog. The combination resulted due to temperature inversion existed in atmosphere. 8.2.3.3 HEALTH EFFECTS OF OXIDES OF NITROGEN Of the seven oxides of nitrogen, only two are known to harm human health. They are nitric oxide (NO) and nitrogen dioxide (NO2). Nitric oxide is less toxic than nitrogen dioxide. NO2 causes eye and nasal irritation at the concentration of about 15 ppm and pulmonary discomfort at the concentration of about 25 ppm after brief exposure. Like CO, NO2 combines with hemoglobin and thereby causes anoxic condition. Mostly, NO2 present in the atmosphere is always less than CO concentration and hence the effects on hemoglobin are not that severe. However, NO2 pose other serious problems and they are presented in table 8.4.



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Table 8.4 Effects of NO2 on human health

NO2 concentration,

ppm Duration of exposure Effects

50-100 Up to 1 hour Inflammation of lung tissue for 6-8 weeks

150-200 ---- Bronchiolitis fibrosa obligerans – fatal result within 3-5 weeks of exposure

500 or more 2-10 days Death Self-check Exercise 10

· Briefly describe the effects of SO2 and NOx Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

8.2.3.4 HEALTH EFFECTS OF OZONE AND PAN Ozone has an irritation effect in the respiratory tract and in lungs. It reaches much deeper into the lungs than SOx. Both ozone and PAN are formed in the atmosphere through photochemical reactions. Both of them cause irritation to eyes and to respiratory tract. Exposure to 50 ppm of ozone for several hours will cause mortality due to pulmonary edema, a condition characterized by accumulation of fluid in lungs. At lower levels, ozone brings about non- lethal accumulation of fluid in the lungs and damage to lung capillaries. Young children are more susceptible to ozone exposure than adults. Both ozone and PAN generate free radicals. The free radicals attack the sulfhydril groups (-SH) on enzymes. The –SH groups are oxidized by these free radicals and are acetylated by PAN. Consequently, the enzymes are inactivated. The enzymes thus affected include isocitric dehydrogenase, malic dehydrogenase and glucose-6-phosphate dehydrogenase. These enzymes catalyze some reactions of citric acid cycle and glycolysis. Thus the energy yielding biochemical reactions are affected which will deprive energy in cells. Self-check Exercise 11



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· Briefly describe the effects of ozone and PAN


8.2.3.5 HEALTH EFFECTS OF OTHER AIR POLLUTANTS

Health effects posed by few pollutants are described briefly in the following

passages. Health effects from H2S and Mercaptans exposure: H2S is known for its foul odor – rotten egg like odor. Exposures to H2S for short periods can result in fatigue in the sense of smell. Methyl mercaptans and ethyl mercaptans are known for their strong odors. Other than odor nuisance, they do not pose any health problems. In fact, mercaptans are added in LPG to detect any leakage of the gas. Health effects from Fluorides exposure: some fluorides are irritants. Hydrogen fluoride in the air has corrosive effect. Prolonged exposure to fluorides may cause flourosis. Health effects from Hydrocarbon vapors exposure: hydrocarbon vapors are known to cause eye irritation and respiratory tract irritation. Health effects from exposure to carcinogens: carcinogenic substances like poly cyclic hydrocarbons, lead etc. are known to cause cancer. PAHs are released mainly from diesel driven vehicles. At present, in India, we use lead-free petrol; hence there is no possibility of lead from automobiles. However, lead can be emitted by other sources like industrial operation. Self-check Exercise 12

· Briefly describe the effects of H2S and mercaptans




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8.3 LET US SUM UP In this lesson we have learnt the effects of air pollution on human health. We learnt the effects caused by particulates and gases. We learnt how these pollutants enter into human system. The most affected parts are lungs, respiratory tract and eyes. We understood the effects caused by particulates, sulfur dioxide, carbon monoxide, oxides of nitrogen, ozone and PAN.


· Take few sheets of paper and write down the effects caused by particulates and gases separately.

· Check whether there are similarities in effects caused by different pollutants. · Find out the major differences in effects caused by different pollutants.


· You might have been amazed to note the defense mechanism available in human respiratory tract to eliminate the particles.

· However, the human defense mechanism cannot prevent the entry of fine particles. Therefore, it is essential to turn our attention in controlling these fine particles.

· Carbon monoxide is responsible for many effects; when exposed it affects our psychomotor functions leading to many other problems.


· Are you able to name the specific effects caused by each pollutant? · Are you able to find the similarities and differences in air pollution effects?

8.7 REFERENCES




Donnelly Publisher, New York, 1976 5. Peavy, H.S., Rowe, D.R., and Tchobanogous, G. Environmental Engineering,

McGraw Hill Book Co., New York, 1985



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LESSON 9 - EFFECTS OF AIR POLLUTION ON PLANTS AND ANIMALS AND ECONOMIC EFFECTS


9.1. Effects of air pollution on plants 9.1.1. Damage to leaves

9.2. Effects of air pollutants on animals 9.3. Effects of air pollution on materials 9.4. Economic losses due to air pollution 9.5. Let us sum up 9.6. Lesson-End Activities 9.7. Points for Discussion 9.8. Check your Progress 9.9. References

9.0 AIMS AND OBJECTIVES In this lesson we are going to learn the effects of air pollution on plants and animals. We will also be learning the economic effects of air pollution. This lesson will help us:

· Identifying the pollutants that cause adverse effects on plants and animals · Understanding the type of effects and magnitude of effects on plants and animals. · Learning the economic effects

At the end of the lesson you will be well aware of the various effects on plants and

animals by air pollution. 9.1 EFFECTS OF AIR POLLUTION ON PLANTS

The following pollutants are known to cause adverse effects on plants:

1. sulfur dioxide 2. fluoride compounds 3. ozone 4. chlorine 5. hydrogen chloride 6. oxides of nitrogen 7. ammonia 8. hydrogen sulfide 9. hydrogen cyanide 10. mercury



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11. ethylene 12. PAN 13. herbicides 14. smog

The above pollutants interfere with plant growth and the process of photosynthesis.

Smog and particulates settle on the leaves and coat and clog the stomata. Coating of leaves reduces the amount of light reaching the leaves while clogging of stomata reduces the intake of CO2. Thus, the particles by coating and clogging will interfere the photosynthesis. 9.1.1 DAMAGE TO LEAVES

Leaves may be damaged in several ways and they are described below. These damages may occur due to infection, nutrition deficiency, weather or exposure to some chemicals:

1. Necrosis: death or collapse of the tissue is called necrosis 2. Chlorosis: it is the loss of green pigment (chlorophyll). The leaf becomes either

pale green or yellow in color due to loss of chlorophyll. 3. Abscission: dropping of leaves is called abscission 4. Epinasty: it is a downward curvature of the leaf due to high growth on the upper

surface.

Sometimes, external factors described above may retard the growth of the plant or reduce the yield of the plant. The effect caused by air pollutants may be of acute or chronic in nature. The effects of air pollutants are summarized in table 2.4.

Table 9.1 – Effects of air pollutants on plants Pollutant Dose Effects

Mild Interveinal chlorotic bleaching of leaves SO2

Severe Necrosis in interveinal areas and skeletonized leaves

Mild Flecks on upper surfaces, premature aging and suppressed growth Ozone

Severe Collapse of leaf, necrosis and bleaching Fluorides Cumulative effect Necrosis at leaf tip NO2 Mild Suppressed growth, leaf bleaching Ethylene Mild Epinasty, leaf abscission

PAN Mild Bronzing of lower leaf surface (upper surface normal), suppressed growth. Young leaves are more susceptible

1. Sulfur dioxide: it produces two types of injury on leaves: acute and chronic,

depending on the concentration and period of exposure. The acute injury is characterized by the killing of marginal or interveinal areas of the leaf. Chronic



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injury is caused by the slow, long-continued absorption of sublethal amounts of gas or by absortption of an amount of gas less than that necessary to cause acute injury. SO2 is toxic to the plants in concentrations above 0.1 to 0.2 ppm. Below 0.4 ppm, it tends to be oxidized in the cells and slightly interfere with photosynthesis. Chronic effects are exhibited in such small concentrations. Above 0.4 ppm acute injury occurs. However, the mechanism by which the effects occur is not fully understood yet.

2. Hydrogen fluoride: it behaves somewhat similar to SO2 in many plants. It causes lesions and interferes with photosynthesis. Plants will recover slower from effects of fluorides than that of SO2. Forage may be rendered unsafe for animal consumption if the plant has absorbed more than 50 ppm of fluoride.

3. Ozone: lesions occur and these lesions are confined to the upper surface. The

effects are noticed in exposures for few hours at about 0.2 ppm. 4. Oxides of nitrogen: they cause the appearance of brown margins and brownish-

black spots on the leaves at the concentrations of about 25 ppm. 5. Photochemical smog: injury occurs from two sources: one due to gases of smog

and second due to deposition of fog droplets on leaves. The smog causes leaf lesions which are quite different from those produced by other pollutants. It is also believed to cause some “invisible injury”.

Plants respond to the pollutants differently as their sensitivity differs due to several

factors:

1. Genetic factors: the genetic make-up of the plant is different in different species. Some plants are more susceptible while others are capable of withstanding to a certain extent.

2. Climatic factors: climatic factors such as duration of light, wavelength of the light, light intensity, temperature and humidity cause the plants to respond differently to the air pollutants.

3. Miscellaneous factors: soil, water and fertility also affect the sensitivity of the plants.


· What is necrosis? · What is epinasty? · Describe the effects of SO2 on plants

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………



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……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

9.2 EFFECTS OF AIR POLLUTANTS ON ANIMALS

Information on effects of air pollution on animals comes mainly from two sources: from the animals affected during major air pollution episodes and from the laboratory research conducted with test animals. Mice, rabbits, rats, guinea pigs and monkeys were the test animals used for such studies.

The effects due to air pollutants are not mainly through the inhalation as with human beings but are by ingestion of contaminated vegetation. Air borne pollutants both settle on the parts of the plants and form a coating over them. Some pollutants enter and interfere with metabolic processes of the plants. Either way, the plants are contaminated with the pollutants. When this contaminated forage is ingested by animals they enter into animals to cause deleterious effects.

1. Fluorides: cattle and sheep are the most susceptible animals to fluorine. Horses and

poultry are the most resistant to fluorine poisoning. Large concentration causes acute effects while low concentration causes chronic effects due to prolonged exposure.

a. Acute fluoride poisoning: symptoms include lack of appetite, rapid loss of weight, decline in health and vigor, lameness, periodic diarrhea, muscular weakness and death. Skeletal fluorosis will also result.

b. Chronic fluoride poisoning: fluoride is accumulated if the animals are exposed continuously in sub-acute doses. It also poisons protoplasm. It has high affinity with calcium and hence, interferes with normal calcification. Though animals are reported to have more resistance than humans to dental mottling, cattle and sheep are affected mostly. Teeth in the process of formation are easily affected. Hence, tooth symptoms are noted to indicate chronic fluorosis. Bone lesions also result due to chronic fluorine poisoning. Overgrowth of bones is observed in legs, jaws and ribs which will result in lameness. Advanced stages of fluorosis exhibit the symptoms such as lack of appetite, general ill-health, lowered fertility, reduced milk production and growth retardation. Other symptoms include mottling, staining and wearing of the teeth, stiffness and lethargy.

2. Arsenic: it occurs as an impurity in many ores and coal. Livestock near various industrial processes are reported to be poisoned by arsenic. Arsenic in dusts spreading over the plants cause adverse effects on animals when ingested.

a. Acute poisoning by arsenic: the symptoms include severe salivation, thirst, vomiting, uneasiness, feeble and irregular pulse and respiration. The animal stamps, lies and gets up. Occurrence of diarrhea with garlic odor and sometimes with blood. The ears will become cold and body will tremble. This will lead to abnormal temperature and convulsion. Finally animal will die within few hours or days.

b. Chronic poisoning by arsenic: it causes depressing effects on the central nervous system. Animal will become dull and exhibit lack of appetite. This



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will result in weight loss. Chronic diarrhea may occur continuously. Skin may become thick. Animal will become anemic. Abortion may also occur. Animals may become sterile in course of time. Chronic poisoning will eventually lead to paralysis and death.

3. Lead: industrial processes such as smelters, coke ovens and coal combustion processes emit lead into the atmosphere. The emitted lead settles over the plants and lead poisoning of animal results through ingestion of forage.

a. Acute poisoning by lead: the symptoms include prostration, staggering and inability to rise. Pulse becomes fast but weak. Some animals may fall suddenly. Stiffness may occur in legs and the animal may develop convulsions. Complete loss of appetite will result. Digestive tract will be paralyzed and there will be diarrhea. Grinding of the teeth and rapid chewing of cud are other symptoms. Eventually, the animal may die.

b. Chronic poisoning by lead: muscles of larynx will be paralyzed and there will be difficulty in breathing. Convulsions may start occurring due to paralysis.


· How do the air pollutants enter into animals? · How does fluoride affect the animals?

Note: Please do not proceed unless you write answers for the above two in the

space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

9.3 EFFECTS OF AIR POLLUTION ON MATERIALS

A wide variety of effects of air pollution on materials is reported. They include corrosion of metals, soiling and eroding of building surfaces, fading of dyed material, rubber cracking, etc. Air pollutants damage the materials by the following five mechanisms:

1. Abrasion: when sufficiently large solid particles travel at high speeds with wind abrade the surfaces they come into contact with. Large sharp edged particles may get embedded on fabrics to accelerate wear.

2. Deposition and removal: as such the solid liquid particles deposited on surface do not damage materials except spoiling its appearance. But when these particles are removed from the surface by cleaning or washing, they may cause some deterioration. The deterioration may be unnoticed initially, but repeated removal of the particles after deposition will deteriorate the materials to a considerable extent.



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3. Direct chemical attack: some air pollutants react chemically with the exposed materials. Sulfur dioxide will react with marble and deteriorate. Hydrogen sulfide will tarnish the surface of silver. Acid mists etch metallic surfaces.

4. Indirect chemical attack: some chemicals may not attack as such. But they may get adsorbed / absorbed by material. Thus lodged chemicals will undergo changes chemically. The new compound may damage the material. For example, SO2 does not damage leather but when it is absorbed by leather, it becomes sulfuric acid which damages the leather.

5. Corrosion: the metals exposed to atmosphere are corroded by existing atmospheric conditions. The corrosion may be facilitated or enhanced by the presence of some air pollutants.

6. Damage by acid rain: acid rain causes extensive damage to building and sculptural materials of marble, limestone, slate, mortar etc. These materials become pitted and weakened mechanically as the soluble sulfates are leached out by the rainwater.


· What are the mechanisms by which the air pollutants affect the materials?


9.4 ECONOMIC LOSSES DUE TO AIR POLLUTION All the effects mentioned above result in economic loss of a region, state and / or country:

1. Economic loss due to effects on human health: when air pollution cause effects on human health, the victims spend money on medical care. Many people are affected and end up with cancer of various types. Apart from the mental agony they undergo, they spend huge amounts of money for the treatment. People may be aware or unaware that the illness was caused by exposure to air pollution. People with chronic illness due to exposure to air pollutants will be spending throughout their lifetime on medical care. If we calculate this expenditure for the entire exposed community, we will realize that this expenditure affects the GDP of a nation.

2. Economic loss due to effects on plants: when crops and other vegetation are affected by air pollution, yield is reduced substantially. It will cause huge loss for the farm owners. This will reflect in country’s economy. In addition, the contaminated plants, when consumed by humans and/or animals they cause deleterious effects on humans/animals. This will further add to the economic loss.



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3. Economic loss due to effects on animals: when animals are affected, especially farm animals, the productivity goes down. The affected animals are also provided with some medical care. All these will lead to heavy expenses and thereby economic loss.

4. Economic loss due to effects on materials: when the materials are affected, we will have to incur the replacement cost, repair cost, cleaning cost etc.

9.5 LET US SUM UP In this lesson and in preceding lesson we have learnt the effects of air pollution on human health, plants, animals and materials. All these effects cause economic losses as they involve loss of bio-resources and material resources. Health effects will lead to high medical expenses. Now, you are aware of the harmful effects of air pollution.


· List out the effects caused by different air pollutants on plants · List out the effects caused by different air pollutants on plants · List out the effects of air pollution on materials · Try to describe the economic effects of air pollution

9.7 POINTS FOR DISCUSSION By now, you might have understood the effects of air pollution on plants, animals and materials. However, the types of effects and their magnitude are different in plants and animals. Animals are affected mainly through food chain by consuming contaminated plants. 9.8 CHECK YOUR PROGRESS

· Are you able to relate the similar effects by different substances? · Can you infer the causative pollutant by observing an ill effect on animal? Or

plant? · Can you realize the magnitude of economic loss incurred by exposure to air

pollution?

9.9 REFERENCES 1. De, A.K. Environmental Chemistry, New Age International Ltd, Publishers,

New Delhi, 1994 2. Rao, M.N. and Rao, H.V.N. Air pollution, Tata McGraw-Hill Publishing Co.

Ltd., New Delhi 3. Stern, A.C. Air pollution, Academic Press, Inc., New York, 1976 4. Wark, K. and Warner, C.F. Air pollution – its origin and control, IEP A Dun-

Donnelly Publisher, New York, 1976



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LESSON 10 – GLOBAL EFFECTS OF AIR POLLUTION Contents 10.0 Aims and objectives

10.1. Introduction 10.2. Green house effect and global warming

10.2.1. Green house gases 10.2.2. Global warming

10.3. Acid rain 10.3.1. History of acid rain 10.3.2. Formation of acid rain 10.3.3. Formation of nitric acid in atmosphere 10.3.4. Formation of sulfuric acid in atmosphere 10.3.5. Impact of acid rain

10.4. Photochemical smog 10.4.1. Effect of photochemical smog on man 10.4.2. Effects of smog on plants

10.5. Chlorfluorocarbons (CFCs) 10.5.1. History of chlloroalkanes 10.5.2. Origin of CFCs 10.5.3. Applications of CFCs 10.5.4. Discovery of ozone layer by CFCs 10.5.5. Chemistry of ozone layer depletion 10.5.6. Ozone layer depletion over polar regions and upper atmosphere 10.5.7. Measures to protect ozone layer 10.5.8. India’s commitment to protect ozone layer 10.5.9. Alternatives to CFCs 10.5.10. Green house effect by CFCs


10.0 AIMS AND OBJECTIVES In the preceding lessons of the Unit 2, we have learnt the effects of air pollution on humans, plants and animals and on materials. So far we learnt the air pollution problem at local level. In this lesson, we are going to learn the effects at regional level and global level. We will be learning about global warming, acid rain photochemical smog and ozone layer depletion by CFCs. 10.1 INTRODUCTION

The air pollution effects are felt locally due to noticeable effects on human health, animals, plants, materials and on visibility. When these pollutants are transported and



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dispersed in the atmosphere, their effects may be felt regionally and even globally. Some of the dispersed pollutants may not be harmful locally but may create problems globally. For example, the CFCs emitted do not cause any health effects but when it reaches the lower atmosphere it is a green house gas; when it reaches the stratosphere, it depletes the ozone. At global level, “global warming”, “acid rain” and “ozone layer depletion” are the environmental problems we face today.

10.2 GREEN HOUSE EFFECT AND GLOBAL WARMING

Greenhouse means a building made mainly of glass, with heat and humidity regulated for growing plants. Solar radiation passes through the glass and the inside environment is heated up. The heat inside the house is contained within as the heated air does not leave the house. Consequently, the glass house will be warmer than the outside atmosphere.

In real atmosphere, the heat energy is contained by certain gases and hence, called Green house effect. During daytime, solar energy passes through the atmosphere and reaches the surface of the earth. During its passage, parts of the incoming solar radiation are scattered, reflected, or absorbed. The remaining radiation reaches the earth’s surface and thereby the earth’s surface is heated up. The energy received by the earth’s surface throughout the daytime heats up the earth’s surface continuously. As the earth’s surface is heated up, it will become hot and hold the thermal energy. The earth at this point, earth starts emitting energy in the form of long wave radiation. This is called outgoing radiation.

Part of this outgoing radiation is absorbed by the atmosphere and retained as heat energy. The remaining energy escapes into the outer spaces. Carbon dioxide, water vapor, and few other gases in the atmosphere are capable of absorbing this outgoing radiation. By now, you might have understood that the concentration of these gases (called, green house gases) determine the amount of radiation absorbed. Yes, more the concentration of these gases, more the amount of long wave radiation absorbed. It is a natural phenomenon occurring in the atmosphere. It helps preventing the earth from drastic cooling of the earth and its atmosphere. If all the heat energy from the earth’s surface is lost to the space, then earth will become too cold. These gases act like a blanket and provide the earth with “blanketing effect”. This process is called Green house effect. In nutshell, atmosphere, like glass absorbs some of the long wave radiation emitted by earth and radiates the energy back to the earth. In this way temperature of the earth is maintained. Note: Actually, the atmosphere does not behave like a real green house. The primary reason is that enclosed structure by glass keeps the air from being carried away by convection to the outside air. This retains the warmth inside the real green house. In contrast, the heated molecules of green house gases by absorbing the long wave radiation spread the heat to its surrounding by convection. Hence, scientifically speaking, the term “Green house effect” is not a right one. However, this term has come to use by convention and has been accepted and used widely. Self-check Exercise 16



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· Why are certain gases called green house gases?


10.2.1 GREEN HOUSE GASES

Actually for the Earth, water vapour is the most important of all greenhouse gases. Water vapor absorbs IR in the region 2.5 to 3.5 µ m, 5 to 7 µm as well as over a broad range above 13 µm. The mixing ratio of water vapor is highly variable in time and space, but the global relative humidity is constant at about 1% and there are no anthropogenic activities that directly cause it to increase. Nevertheless gaseous water is involved in feedback processes: positive in that increased global warming means increased evaporation from ocean and land surfaces leading to higher ratios of atmospheric water, thereby enhancing warming: negative in that the troposphere becomes more cloudy leading to increased reflection and absorption in the atmosphere so that the solar flux at the solid/liquid surface of the Earth is reduced. In 1995, greenhouse warming associated with water vapor was estimated to be 110 Wm-2.

It is now well established that carbon dioxide is a major contributor to greenhouse effect. Carbon dioxide absorbs in the range of 14 to 19 µm, and completely blocks the radiative flux between 15 and 16 µm. It also absorbs at wavelengths between 4 and 4.5 µm. Water and carbon dioxide are the two most important greenhouse gases. Together, they absorb much of the radiation in the thermal infrared region below 7.5 µm and above 13 µm. Between these two wave lengths, very little IR radiation is absorbed by these gases, and this part of the spectrum is regarded as window, transparent to the radiation of interest. Other gases which absorb in that region, however, partially close the window and can have a major effect on heat retention in the region of the earth.

Methane, another greenhouse gas, absorbs radiation in the wavelength ranges from 3 to 4 µm and 7 to 8.4 µm. According to 1995 estimates, methane contributed 1.7 Wm-2 to greenhouse warming. Ozone absorbs between 9 to 10 µm in the IR region and it therefore acts as a highly efficient greenhouse gas. In the troposphere, ozone concentrations are highly variable, partially because it has a short lifetime. Greater production of NOx by fossil fuels burning and a forest and grassland fire has resulted in net lower tropospheric concentration of ozone by about 1.6% in the northern hemisphere. The overall contribution of ozone to warming has been estimated to be 1.3 Wm-2 in 1995.

Nitrous oxide absorbs IR radiation in the ranges of 3 to 5 µm and 7.5 to 9 µm. According to 1995 estimates its concentration was about 312 ppbv and it is increasing at a rate of 0.3% per year. It has approximately the same effect on warming as by ozone. There are no important troposphere sinks for nitrous oxide gas. So it is lost only by slow leakage



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into the stratosphere where it undergoes photolytic degradation. It, therefore, has a substantial troposphere residence time estimated to be about 120 years.

In addition to their role as agents for the catalytic decomposition of stratospheric ozone, chlorofluorocarbons (CFCs) are also important greenhouse gases. They absorb in the range 8 to 12 µm with each CFC having specific absorption bands in this region. Thus CFC-11 absorbs at 9.5µm and 11.5µm, and CFC-12 at 9.5µm and 11.0µm.

The Hydrochloroflurocarbons (HCFCs) also attenuate radiation within the same range, but their residence time in the troposphere is much shorter than that of the CFCs. The rate of increase of the CFCs has declined by a factor greater than two in the past decade, but HCFC concentrations are increasing at a much higher rate.

Three fully fluorinated gases of industrial origin have recently been recognized as potential contributors to global warming. They are present in trace amounts, but have lifetime of thousands or ten of thousands of years. Tetrafluromethane (CF4) and hexachloroethane (C2F6) both are produced during electrolysis of alumina (Al2O3) in cryolite (Na3AlF6) at carbon electrodes. The release of the gases has been estimated to be at about 0.77 and 0.1 kg respectively per ton of aluminum produced. Yet another gas, sulfur hexafluoride (SF6) is formed during magnesium production.

Clouds are the most important atmospheric aerosol in terms of reflecting and absorbing incoming radiation and emitted radiation from the earth. We know the cooling effects of clouds on warm days, and warming effect on cooling nights. Self-check Exercise 17

· What is the window for outgoing radiation? Explain.


10.2.2 GLOBAL WARMING

The four major greenhouse gases, which cause adverse effects, are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs). Among these CO2 is the most common and important greenhouse gas. Here it should be noted that ozone and SO2 also act as serious pollutants in causing global warming. The other greenhouse gases such as methane and chlorofluorocarbons contribute about 18% and 14% respectively to the global warming.



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Since the beginning of the industrial revolution, three human activities have contributed to significant rise of concentration of green house gases. The activities are:

1. Use of fossil fuels: it releases huge amounts of carbon dioxide into the atmosphere. 2. Deforestation and burning of forests and grasslands to convert into cropland: forests

and grasslands are cleared and/or burned for converting them into cropland. Burning of biomass produces large quantities of CO 2. Clearance of forests also deprives available vegetation for absorption of CO2 through photosynthesis.

3. Cultivation of rice in paddies and use of inorganic fertilizers: cultivation of rice in paddies generates methane and use of fertilizers release N2O into the atmosphere.

Since, 1860, the concentration of green house gases, CO2, CH4 and N2O have risen

sharply especially since, 1950. Burning of coal for power generation and for industrial purposes and burning of petroleum products by millions of vehicles are the two major contributors of CO2 emissions.

As the green house gases increase dramatically, by human activities, the green house effect is enhanced. That is more amount of outgoing long wave radiation is retained than required amount. It results in greater warming of the atmosphere than normal. It is called “enhanced green house effect”. Due to this enhancement, the earth’s atmosphere is warming up gradually more and more. This phenomenon is called global warming.

Since 1960 total atmospheric carbon dioxide has increased from about 320 to over 350 ppm. Over the same period, the average global temperature has increased very slightly, 0.6 ± 0.2 °C. Nine warmest years have occurred since 1990. The hottest year was 1998, followed in order by 2002 and 2001. There is an apparent correlation between increases in fossil fuel use, atmospheric concentration of CO2 and global temperature between 1970 and 2002.

At earth’s poles and in Greenland, the temperature rise has been noticed, so also some melting of land-based ice caps and floating ice. Some glaciers on the top of mountains in Alps, Andes, Himalayas, northern Cascades of Washington, and Mount Kilimanjaro in Africa have begun shrinking due to melting of ice.

In addition, some warm-climate fish and other species have migrated northward. The season, spring arrives earlier and autumn arrives later than normal in many parts of the globe.

All the above suggest that the global warming is real and happening. If the warming continues, the ice from polar region and from mountain glacier will melt (not all the ice, but some) which will cause coastal flooding. Coastal flooding will result in rise of the sea level and consequently inundation of coastal areas (villages, towns, cities). It is estimated that sea level will rise by 1.5 m by 2050.


· Distinguish between green house effect and global warming.



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10.3 ACID RAIN

Acid rain means literally, the presence of excessive acids in rain waters. Acid rain is in fact, a mixture of mainly H2SO4 and HNO3 where the ratio of these two acids may vary depending upon the relative quantities of oxides of sulfur and nitrogen emitted. H2SO4 is the major contributor (60 – 70%) to acid precipitation, HNO3 ranks second (30-40%) and HCl third. These acids tend to lower the pH of the precipitation.

When the pH of rain water or snow is less than 5.6, it is called acid rain. Chemically speaking, neutral pH is 7.0. In chemistry of precipitation (rain, snow etc.), the pH value below 5.6 is considered acidic. It is because of lowering pH by dissolution of atmospheric carbon dioxide in rain water thereby formation of carbonic acid. Hence, pH value at 5.6 and above is considered as the acidity by CO2. Below 5.6, it is considered to be man-made acidity.

Although the oxides of sulfur as well as that of nitrogen have been recognized as the main components responsible for acid rain, the relative contributions to acid rain is still not very clear because of highly complex nature of their transport and complexity involved in their removal from rain water. Once these oxides have fallen, along with rain water, it is difficult to remove them from the environment. These oxides may travel long distances in the atmosphere and during this journey, they may undergo several physical and chemical transformations to produce more hazardous products which may also fall with rain. Hence, acid rain is not simply a man made problem but is a global ecological problem.

10.3.1 HISTORY OF ACID RAIN

Most acids come from human activities. However, there has always been some acid in rain, coming from volcanoes, swamps and the plankton in the oceans, but scientists know that it has increased very sharply over the past 200 years. The acidity is mainly associated with the transport and subsequent deposition of oxides of sulfur, nitrogen and their oxidative products. These oxides are produced by combustion of fossil fuels, smelter, power plants, automobile exhausts and domestic fires etc. The accumulation of these oxides was first reported to be responsible for increasing the acidity in Swedish lakes and rivers. The acid rain problem has drastically increased due to industrialization. Burning of fossil fuels for power generations contributes to 60 – 70% of total SO2 emitted globally. Emission of NOx from anthropogenic sources ranges between 20 – 90 million tons annually over the globe.



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Acid rain was first found in Manchester, England. In 1852, Robert Angus Smith found the relationship between acid rain and atmospheric pollution. Though acid rain was discovered in 1852, it wasn't until the late 1960s that scientists began widely observing and studying the phenomenon. Canadian Harold Harvey was among the first to research a "dead" lake due to acid rain.

In developed countries, tall stacks are used with the intention of releasing the

pollutants above the inversion layer to solve the air pollution problem locally. But, the primary air pollutants, SO2 and nitrogen oxides emitted above the inversion layer are transported as much as 1,000 km by prevailing winds. During their transportation, they are converted into acid vapor, droplets of acid and particles of sulfate and nitrate salts by chemical transformations.

Acid deposition is a regional problem in the eastern United States and in other parts

of the world. Most of these regions are downwind from coal-burning power plants, smelters, or factories or are major urban areas with large number of vehicles. The pH of rain water in eastern United States was reported to be in the range of 4.2-4.7. In some parts of eastern United States and east of Los Angeles the pH of precipitation was reported as close to 2.3. This pH value is equivalent to that of lemon juice. U.S. Environmental Protection Agency (USEPA) has estimated that coal-burning power plants release about 66% of the SO2 and 25% of the NOx of the total SO2 and NOx responsible for acid deposition.

Acidic emissions from industrialized areas of Western Europe and Eastern Europe

are transported into Norway, Switzerland, Austria, Sweden, the Netherlands and Finland. During transportation these gases are converted into acids resulting in acid deposition.

10.3.2 FORMATION OF ACID RAIN

The acidic substances formed in the atmosphere remain in the atmosphere for 2-14 days, depending mainly on prevailing winds, precipitation, and other weather patterns. During this period, they descend to earth’s surface either as wet deposition or as dry deposition. The resulting mixture is called acid deposition

Precipitation is water falling on earth in either liquid or solid form. Precipitation

occurs in the form of rain, drizzle, snow, hail and/or their modifications. The term, “Acid deposition” is used to refer to the process of bringing down the acidic substances along with precipitation or with particles coming down. The first one is called “wet deposition” and the latter “dry deposition”. In dry deposition, the acidic particles are brought either by gravitational settling or by adsorption of the particles on the surfaces they encounter with.

In other words, precipitation by wet deposition refers to deposition of water based particles in liquid or solid form on the earth’s surface. Precipitation of dry species including gases, such as SO2 and solid acidic particles such as sulfates and nitrates is known as precipitation by dry deposition. However, the wet deposition is much more common. Self-check Exercise 19



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· Distinguish between wet deposition and dry deposition.


10.3.3 FORMATION OF NITRIC ACID IN ATMOSPHERE

Formation of the nitric acid in the atmosphere starts with the emissions of oxides of nitrogen mainly from combustion processes. At high temperatures, the atmospheric oxygen and nitrogen combine to form nitric oxide (NO). Nitric oxide is also released as a result of microbial nitrification in the soil. Lightning is the other important source of nitric oxide.

In day time, nitric oxide is oxidized by O2, O3 and ROO•. For example, NO+O3 NO2 + O2

The NO2 so formed, subsequently contributes to ozone and •OH radical formation and partially responsible for the initiation of a photochemical smog sequence. In the process, nitric oxide is generated and is, therefore, available once again to contribute to additional ozone and smog formation. NO2 + hν NO + O O + O2 + M O3 + M O3 + hν O2* + O* O* + H2O 2 •OH The main mechanism for the removal of nitrogen oxides from the atmosphere is by conversion to nitric acid, through oxidation of NO2 by •OH radial. • NO2 + • OH + M HNO3 + M After sunset, the mechanism becomes different. The •NO3 is formed during both day and night, but accumulates only at night time, because it is destroyed by photochemical reaction or photolysis in daytime. • NO2 + O3 NO3 + O2



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The radical can take part in a number of reactions. Generally, it is destroyed to some extent by reactions with the NOx compounds. NO2 + NO3 NO + NO2 + O2

NO3 + NO 2NO2 Similar to •OH radical, the nitrate radical is also capable of adding to the double bond of olefins. NO3 + CnH2n •CnH2nNO3 Generally, addition of nitrate radical is followed by rapid addition of O2. Like •OH radical, the •NO3 radical is also capable of initiating reaction sequences by first abstracting hydrogen. Nitric acid is thus formed. •NO3 + RCHO •RCO + HNO3

•NO3 + RH •R + HNO3

The radicals •R and RCO so formed, can take part in further reactions such as addition of O2. According to another sequence of reactions, the nitrate radical can also react in the following way.

NO3 + NO2 N2O5

N2O5 + H2O 2HNO3

Under the humid conditions of air, N2O5 invariably reacts with water vapor to form droplets of HNO3. Some HNO2 is also formed. N2O5 + H2O 2HNO2 HNO3 and HNO2 then return to the earth surface. However, HNO3 can be removed as particulate nitrates after reaction with bases such as NH3. 10.3.4 FORMATION OF SULFURIC ACID IN ATMOSPHERE The formation of sulfuric acid in the atmosphere can take place with a wide range of reduced as well as partially oxidized sulfur compounds. In the atmosphere, H2S, CS2 and COS are oxidized via •OH radical producing thionyl radical (•SH). In the stratosphere, it can undergo photochemical oxidation to produce SO2 and ultimately S2- ion, which is an important component of stratospheric aerosol. Volcanic eruptions release SO2 directly into the atmosphere, increasing the density of the aerosol leading to significant depression in the global temperature by blocking solar radiation. Further oxidation of thionyl radical gives rise to the production of SO2.

•SH + O2 SO + •OH



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•SH + O3 •SHO + O2

•SHO + O2 SO + HOO• O2 SO + O3 SO2 + other products NO2 The production of H2SO4 from SO2 may take place homogeneously in the gas phase, as

SO2 + •OH + M HOSO2 + M

Where, M is O2 or N2 in the troposphere. The HOSO2 radical so formed can undergo a number of reactions, some of which produce sulfuric acid. •HSO2 + O2 + M HOO• +SO3 + M

SO3 + H2O H2SO4

Due to SO2 emissions, and subsequent reactions, the pH of rain can drop to as low as 2.0. This increases the acidity of water bodies, particularly rivers and lakes. 10.3.5 IMPACT OF ACID RAIN

1. Impact on Animals Most aquatic animals cannot survive a drop in pH, especially when it is lower than 4. Some species of fish, such as salmon, die even when the pH drops to 5.5. Generally, at pH < 6, several susceptible species of algae and zooplankton are eliminated but the resistant once become more dominant. A reduction in the zooplankton and bottom fauna will ultimately affect the food availability for the fish population.

2. Impact on Plants

Corrosive nature of the acidic water itself is dangerous to plants. It decolorizes the leaf pigments, thus rendering them chlorophyll–less; such an yellowing would result in a decreasing agricultural productivity. Alphalpha, barley, cotton, lettuce and spinache are the non–woody plants most susceptible to acid-rain damage. Similarly apple, pear and pine trees figure among the most vulnerable trees species.

3. Chemical Imbalance

The normal growths and development of plant and animal organisms are favored in balanced ecosystems, where an equilibrium exists between available and non available forms of an element; this balance occurs among the various chemical forms of an element and among the various elements present in different compartments of the ecosystem. Acidic rainfall may upset a chemical balance. Since the acid rain water flushing through the atmosphere may dissolve some metallic air pollutants, it can enhance their toxic action more directly, immediately and drastically, thus posing a serious threat to plant and/or animal life. The integrity of nutrient forms in various environmental compartments is altered.



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4. Impact on Material

Metallic surfaces exposed to acid rain are susceptible to corrosion damage. Thus the metals, with which H2SO4 reacts, form their respective sulfates. For eg., blue FeSO4 results from iron, green CuSO4 from Copper and white Al2(SO4)3 from aluminum. Surfaces made of steal and zinc are also susceptible. On contact with acid rain with water, textile fabrics, paper and leather products may lose their material strength, get discolored are simply disintegrate depending on the degree of acidity.

Building materials (limestone, marble, dolomite, mortar and slate) are especially weakened on reaction with acidic water. Water, whose pH is acidic, can react with these water- insoluble carbonates to yield water-soluble sulfates which can easily be removed from the building structures:


· What is the pH value under which the rain is considered acidic? Why?


10.4 PHOTOCHEMICAL SMOG

Nitrogen oxides in combination with unsaturated hydrocarbons, CO, O3, hydrogen

peroxides as well as hydroperoxides and organic peroxides in presence of sunlight lead to the formation of photochemical smog. When oxides of nitrogen, VOCs and sunlight come together, they can initiate a complex set of reactions that produce a number of secondary pollutants known as photochemical oxidants. Ozone (O3) is the most abundant of the photochemical oxidants. Photochemical reactions are initiated by ultraviolet light in air. Peroxybenzoyl nitrate (PBxN) is also produced in photochemical smog in presence of NO2

and olefins. The smog may have a 50 ppb of PAN also. PBxN is 100 times more toxic than PAN and ~200 times as powerful as formaldehyde.

Cities like Los Angeles, London, Tokyo, Sydney, Athens, Madrid, Delhi, Calcutta, Madras and Bombay are suffering from this smog because of abundant sunshine, atmospheric temperature inversion and growing vehicular emissions. In the very simplest of terms, we can express the formation of photochemical smog as VOCs + NOx + Sunlight Photochemical smog



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The NO – NO2 – O3 Photochemical reaction sequence: Consider some of the important reactions involving NOx without the complications associated with the added hydrocarbons. We can begin with the formation of NO during combustion N2 + O2 2NO The nitric oxide thus emitted can be oxidized to NO2: 2NO + O2 2NO2 If sunlight is available, a photon with the right amount of energy can decompose NO2 in a process called photolysis. NO2 + hν NO + O Where, hν represents a photon (with wavelength λ < 0.39 ΅m). The freed atomic oxygen (O) can then combine with diatomic oxygen (O2) to form ozone (O3): O + O2 +M O3 + M Where, M represents a molecule whose presence is necessary to absorb excess energy from the reaction. Without M, the ozone would have too much energy to be stable, and it would dissociate back to O and O2. Ozone can then convert NO back to NO2:

O3 + NO NO2 + O2

The diagram suggests that we might expect NO concentrations to rise as early morning traffic emits its load of NO. As the morning progresses, we would expect to see a drop in NO and rise in NO2 as NO gets converted to NO2. As the sun’s intensity increases toward noon, the rate of photolysis of NO2 increases; thus NO2 begins to drop while O3

rises. Ozone is so effective in its reaction with NO. NO concentrations do not rise as long as O3 is present in the atmosphere throughout the afternoon even if NO are emitted by the available sources.


· What is the role of sunlight in the formation of ozone and PAN?

O2

O

NO

NO emissions Nitric

oxide (NO) Nitrogen dioxide

Ozone (O3)

O3

NO2

O2

Figure 10.1 Simplified atmospheric nitrogen photolytic cycle

Sun light



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Hydrocarbons and NOx: A multitude of organic chemicals are introduced to the atmosphere by burning of fuels, evaporation of volatiles and production by chemical reactions.

Atoms or molecules with an odd number of electrons, are called free radicals. Having an odd number of electrons means that one electron is not being used as a bonding electron to other atoms. Free radicals tend to be very reactive, and they are very important in the study of air pollution.

The alkanes are hydrocarbons in which each carbon forms single bonds with other atoms. The alkane series is the familiar sequence: methane (CH4), ethane (C2H6), propane (C3H8)… (CnH2n+2). If one of the hydrogen is removed from an alkane, the result in free radical is called an alkyl. The alkyls then form a series beginning with methyl (CH3

•), ethyl (C2H5

•) and so on. We could represent an alkyl with the generation expression CnH2n+1•, but

it is more convenient to call it simply R•.

Another important key to understanding atmospheric organic chemistry is the hydroxyl radical OH•, which is formed when atomic oxygen reacts with water. O + H2O 2OH•

The OH radical is extremely reactive, and its atmospheric concentration is so low to be detected. Nevertheless, it plays a key role in many reactions, including the oxidations of NO2 to nitric acid and CO to CO2.

OH• + NO2 HNO3

OH• + CO CO2 + H•

10.4.1 EFFECT OF PHOTOCHEMICAL SMOG ON MAN

Photochemical smog is characterized by yellowish grey haze in the atmosphere. This smog along with ozone may irritate the eyes and nose change lung function, degrade human physical performance and exacerbate asthma. Symptoms like nasal-block, discharge of sneezing, hacking cough, reduction or changes of air way by obstruction may persist in highly vehicular areas. Studies also revealed prevalence of chest problems and upper air way morbidity in areas with higher levels of oxidants in Bombay and Delhi. Occurrence of



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cold, cough and sputum and breathlessness are closely related to peaking of vehicular pollution. Photochemical smog prompts respiratory problems, reduces visibility, alters various blood parameters and aggravates diseases like headache and bronchitis.

10.4.2 EFFECTS OF SMOG ON PLANTS

Photochemical smog at a very low concentration of 0.01 ppm is reported to cause injuries to petunia, lettuce, pinto bean, citrus, salad crops and coniferous trees. PAN causes injury in beets, celery, pepper, aster. It causes silvering of leaves and death to forest trees. PAN inhibits important Hill reaction of photosynthesis. Smog is regarded to produce early maturity or senescence in plants. Exposure of 4 ppb of PAN for four hours is known to create visible damage in plants. Vegetation damage may occur in several forms such as chlorosis, leaf abscission and curling etc. Photochemical smog in conjunction with O3, PAN and NOx cause damage to forests, agriculture and other materials-rubber, paint, fibers and polymers.



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· Describe the effects of smog on humans?


NO reacts with O3 to

produce NO2

Absorption of solar energy by NO2 produces

NO and atomic oxygen

Atomic oxygen, HO• and O3 react with hydrocarbons to produce highly

reactive hydrocarbon free radicals O reacts with O2,

yielding ozone, O3

Hydrocarbon free radicals react further with species such as NO2 to produce PAN, aldehydes and other smog

components

NO2

Figure 10.2 - Generalised scheme for the formation of photochemical smog

Solar energy

input

hv

Hydrocarbon free

radicals

O

O2

O3

O NO

NO2

O3

NO2

Reactive hydrocarbon

Hydrocarbon free radicals



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……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

10.5 CHLOROFLUOROCARBON (CFCs) Chlorofluorocarbons are popularly known for their role in ozone depletion and in green house effect. When they are present in troposphere, they absorb the outgoing radiation and cause green house effect; when present in stratosphere, they deplete ozone layer. Chlorofluorocarbons are abbreviated as CFCs. They are members of the group of chemicals, haloalkanes (also known as halogenoalkanes or alkyl halides). A haloalkane also known as alkyl halogenide, halogenalkane or halogenoalkane, and alkyl halide is a chemical compound derived from an alkane by substituting one or more hydrogen atoms with halogen atoms. Substitution with fluorine, chlorine, bromine and iodine results in fluoroalkanes, chloroalkanes, bromoalkanes a n d iodoalkanes, respectively. Mixed compounds are also possible, the best-known examples being the chlorofluorocarbons (CFCs) which are mainly responsible for ozone depletion. Haloalkanes are used in semiconductor device fabrication, as refrigerants, foam blowing agents, solvents, aerosol spray propellants, fire extinguishing agents, and chemical reagents. Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. The word Freon is a registered trademark belonging to DuPont.

An overview of the available haloalkanes are presented in table 10.1 The table gives an overview of most haloalkanes in general use or commonly known. Listing includes bulk commodity products as well as laboratory chemicals.

Table 10.1 Overview of available haloalkanes

Systematic name Common/Trivial

name(s) Code

Chem. formula

Halomethanes Chloromethane Methyl chloride CH3Cl Dichloromethane Methylene chloride CH2Cl2 Trichloromethane Chloroform CHCl3

Tetrachloromethane Carbon tetrachloride, Freon 10

CFC-10 CCl4

Tetrafluoromethane Carbon tetrafluoride, Freon 14 CFC-14 CF4 Trichlorofluoromethane Freon-11, R-11 CFC-11 CCl3F Dichlorodifluoromethane Freon-12, R-12 CFC-12 CCl2F2 Chlorotrifluoromethane CFC-13 CClF3 Chlorodifluoromethane R-22 HCFC-22 CHClF2 Trifluoromethane Fluoroform HFC-23 CHF3 Chlorofluoromethane Freon 31 CH2ClF



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Difluoromethane HFC-32 CH2F2 Fluoromethane Methyl fluoride HFC-41 CH3F Dibromomethane Methylene bromide CH2Br2 Tribromomethane Bromoform CHBr3 Bromochloromethane Halon 1011 CH2BrCl

Bromochlorodifluoromethane BCF, Halon 1211 BCF, or Freon 12B1

Halon 1211 CBrClF2

Bromotrifluoromethane BTM, Halon 1301 BTM, or Freon 13BI

Halon 1301 CBrF3

Trifluoroiodomethane Trifluoromethyl iodide Freon 13T1 CF3I Haloethanes 1,1,1-Trichloroethane Methyl chloroform, tri Cl3C-CH3 Hexachloroethane CFC-110 C2Cl6 1,1,2-Trichloro-1,2,2-trifluoroethane

Trichlorotrifluoroethane CFC-113 Cl2FC-CClF2

1,1,1-trichloro-2,2,2-trifluoroethane

CFC-113a Cl3C-CF3

1,2-Dichloro-1,1,2,2-tetrafluoroethane

Dichlorotetrafluoroethane CFC-114 ClF2C-CClF2

1-Chloro-1,1,2,2,2-pentafluoroethane

Chloropentafluoroethane CFC-115 ClF2C-CF3

2-Chloro-1,1,1,2-tetrafluoroethane

HFC-124 CHF2CF3

1,1,2,2,2-pentafluoroethane Pentafluoroethane HFC-125 CHF2CF3 1,1,2,2-Tetrafluoroethane HFC-134 F2HC-CHF2

1,1,1,2-Tetrafluoroethane R-134a HFC-134a, Suva-134a

F3C-CH2F

1,1-Dichloro-1-fluoroethane HCFC-141b Cl2FC-CH3 1-Chloro-1,1-difluoroethane HCFC-142b ClF2C-CH3

1,2-Dichloroethane Ethylene dichloride Freon 150 ClH2C-CH2Cl

1,1-Dichloroethane Ethylidene dichloride Freon 150a Cl2HC-CH3 1,1-Difluoroethane HFC-152a F2HC-CH3 Longer haloalkanes, polymers

1,1,1,2,3,3,3-Heptafluoropropane

HFC-227ea, FE-227, FM-200

F3C-CHF-CF3

Decafluorobutane perfluorobutane R610, PFB, CEA-410

F3C-CF2-CF2-CF3

Polychloroethene polyvinyl chloride, PVC -[CHCl-CH2]x-

Polytetrafluoroethene Polytetrafluoroethylene, PTFE, Teflon

-[CF2-CF2]x-

Source: Wikipedia, the free encyclopedia



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In fact, you need not remember all the haloalkanes mentioned in the above table. But, it is good to know the available haloalkanes. Self-check Exercise 23

· What is a haloalkane? · What is CFC?

Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 10.5.1 HISTORY OF CHLOROALKANES

During World War II, various early chloroalkanes were in standard use in military aircraft by some combatants, but these early halons suffered from excessive toxicity. Nevertheless, after the war they slowly became more common in civil aviation as well.

In the 1960s, fluoroalkanes and bromofluoroalkanes became available and were quickly recognized as being among the most effective fire-fighting materials discovered. Much early research with Halon 1301 was conducted under the auspices of the US Armed Forces, while Halon 1211 was, initially, mainly developed in the UK. By the late 1960s they were standard in many applications where water and dry-powder extinguishers posed a threat of damage to the protected property, including computer rooms, telecommunications switches, laboratories, museums and art collections. Beginning with warships, in the 1970s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel. 10.5.2 ORIGIN OF CFCs

Chlorofluorocarbons (CFC) are compounds containing chlorine, fluorine and carbon only, that is they contain no hydrogen. They were formerly used widely in industry, for example as refrigerants, propellants, and cleaning solvents.

American engineer Thomas Midgley developed chlorofluorocarbons (CFC) in 1928

as a replacement for ammonia (NH3), chloromethane (CH3Cl), and sulfur dioxide (SO2), which are toxic but were in common use at the time as refrigerants. The new compound developed had to have a low boiling point and be non-toxic and generally non-reactive. In a demonstration for the American Chemical Society, Midgley flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle.



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Figure 10.3 Chemical structure of selected chlorofluorocarbons

Midgley specifically developed CCl2F2. However, one of the attractive features is that there exists a whole family of the compounds, each having a unique boiling point which can suit different applications. In addition to their original application asrefrigerants, chlorofluoroalkanes have been used as propellants in aerosol cans, cleaning solvents for circuit boards, and blowing agents for making expanded plastics (such as the expanded polystyrene used in packaging materials and disposable coffee cups).


· Who did develop CFC? · Write the structure of CFC-12


space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 10.5.3 APPLICATIONS OF CFCs The CFCs have many applications. They are used as propellants, fire extinguishers, and refrigerants. Propellant: One major use of CFCs has been as propellants in aerosol inhalers for drugs used to treat asthma. Fire extinguisher: At high temperatures, halons decompose to release halogen atoms that combine readily with active hydrogen atoms, quenching the flame propagation reaction even when adequate fuel, oxygen and heat remains. The chemical reaction in a flame proceeds as a free radical chain reaction; by sequestering the radicals which propagate the reaction, halons are able to "poison" the fire at much lower concentrations than are required



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by fire suppressants using the more traditional methods of cooling, oxygen deprivation, or fuel dilution.

For example, Halon 1301 total flooding systems are typically used at concentrations no higher than 7% v/v in air, and can suppress many fires at 2.9% v/v. By contrast, carbon dioxide fire suppression flood systems are operated from 34% concentration by volume (surface-only combustion of liquid fuels) up to 75% (dust traps). Carbon dioxide can cause severe distress at concentrations of 3 to 6%, and has caused death by respiratory paralysis in a few minutes at 10% concentration. Halon 1301 causes only slight giddiness at its effective concentration of 5%, and even at 15% persons remain conscious but impaired and suffer no long term effects. (Experimental animals have also been exposed to 2% concentrations of Halon 1301 for 30 hours per week for 4 months, with no discernible health effects at all.) Halon 1211 also has low toxicity, although it is more toxic than Halon 1301, and thus considered unsuitable for flooding systems.

However, Halon 1301 fire suppression is not completely non-toxic; very high temperature flame, or contact with red-hot metal, can cause decomposition of Halon 1301 to toxic byproducts. The presence of such byproducts is readily detected because they include hydrobromic acid and hydrofluoric acid, which are intensely irritating. Halons are very effective on Class A (organic solids), B (flammable liquids and gases) and C (electrical) fires, but they are totally unsuitable for Class D (metal) fires, as they will not only produce toxic gas and fail to halt the fire, but in some cases pose a risk of explosion. Halons can be used on Class K (kitchen oils and greases) fires, but offer no advantages over specialised foams.

Halon 1211 is typically used in hand-held extinguishers, in which a stream of liquid

halon is directed at a smaller fire by a user. The stream evaporates under reduced pressure, producing strong local cooling, as well as a high concentration of halon in the immediate vicinity of the fire. In this mode, extinguishment is achieved by cooling and oxygen deprivation at the core of the fire, as well as radical quenching over a larger area. After fire suppression, the halon moves away with the surrounding air, leaving no residue. Let us limit our discussion with this about the use of CFCs as fire extinguishers. Refrigerants: CFCs have been used as refrigerants in cooling systems. The commonly used refrigerants are:

· CFC—list of chlorofluorocarbons · HCFC—list of hydrochlorofluorocarbons · HFC—list of hydrofluorocarbons · FC—list of fluorocarbons · PFC—list of perfluorocarbons (completely fluorinated)


· What are the applications of CFC? Explain briefly



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Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 10.5.4 DISCOVERY OF OZONE LAYER DEPLETION BY CFCs After the development of his electron capture detector, James Lovelock was the first to detect the widespread presence of CFCs in the air, finding a concentration of 60 parts per trillion of CFC-11 over Ireland. In a self- funded research expedition ending in 1973, Lovelock went on to measure the concentration of CFC-11 in both the Arctic and Antarctic, finding the presence of the gas in each of 50 air samples collected. But he incorrectly concluded that CFC's are not hazardous to the environment.

The experiment did however provide the first useful data on the presence of CFC's in the atmosphere. The damage caused by CFC's discovered by Sherry Rowland and Mario Molina who, after hearing a lecture on the subject of Lovelocks work, embarked on research resulting in the first published paper suggesting the connection in 1974. It turns out that one of CFCs' most attractive features—their unreactivity—has been instrumental in making them one of the most significant pollutants. CFCs' lack of reactivity gives them a lifespan which can exceed 100 years in some cases. This gives them time to diffuse into the upper stratosphere. Here, the sun's ultraviolet radiation is strong enough to break off the chlorine atom, which on its own is a highly reactive free radical. This catalyzes the break up of ozone into oxygen by means of a variety of mechanisms, of which the simplest is:

Cl· + O3 › ClO· + O2 ClO· + O3 › Cl· + 2 O2 Since the chlorine is regenerated at the end of these reactions, a single Cl atom can

destroy many thousands of ozone molecules. Reaction schemes similar to this one (but more complicated) are believed to be the cause of the ozone hole observed over the poles and upper latitudes of the Earth. Decreases in stratospheric ozone may lead to increases in skin cancer. We can sum up the history of discovery of ozone layer is as follows:

· In 1974, chemists Sherwood Roland and Mario Molina suggested that CFCs were depleting the ozone in stratosphere.

· In 1985, scientists discovered the annual seasonal thinning of ozone layer over Antarctica.

· In 1987, 24 countries agreed to halve their CFC emissions in Montreal Protocol.



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· In 1995, Paul Cruzen, Mario Molina and Sherwood Rowland won Nobel Prize for their work on ozone layer depletion by CFCs.

10.5.5 CHEMISTRY OF OZONE LAYER DEPLETION We have already seen the chemistry of ozone layer depletion in Lesson 2 of Unit 1. Rowland and Molina undertook the research and concluded the following:

1. CFCs remain in the troposphere because they are insoluble in water and are chemically unreactive.

2. Within 11 to 20 years of their release they rise to stratosphere mostly through convection, random drift and the turbulent mixing of air in the troposphere.

3. Once they reach the stratosphere, the CFCs break down under the influence of high energy UV radiation. This releases highly reactive chlorine atoms, which seed up the breakdown of very reactive ozone into O2 and O in a cyclic chain of chemical reactions. This causes ozone in various parts of the atmosphere to be destroyed faster than it is formed.

4. Each CFC molecule can last in the stratosphere for 65 to 385 years, depending on its type. During that time, each chlorine atom released can convert about 100,000 molecules of O3 into O2.

The details of chemistry of ozone layer are already presented in Lesson 2 of Unit 1.

However, the details are reproduced below:

Ozone depletion by chlorine atom is illustrated in figure 10.4. The chemical reactions that lead to destruction of O3 by CFCl3 are shown below. Similar reactions take place with other CFCs and BFCs.



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CFCl3 + hn CFCl2 + Cl•

Cl• + O3 ClO• + O2

ClO• + O Cl• + O2

In a cyclic reaction, each ClO• can initiate a series of chemical reactions which lead to destruction of about 100,000 molecules of ozone!!

200 nm


· How many years do a CFC molecule remain in atmosphere? · How many molecules of ozone does a chlorine atom destroy? Explain.



10.5.6 OZONE LAYER DEPLETION OVER POLAR REGIONS AND UPPER LATITUDES

Figure 10.4 – Chemistry of ozone depletion



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In 1984, after analyzing the satellite data, scientists discovered that 40-50% of the ozone in the upper stratosphere over Antarctica was destroyed during the Antarctic spring and early summer (September to December) especially since 1974. The observed seasonal loss has been incorrectly called an ozone hole. A more accurate term is ozone thinning because the ozone depletion varies with altitude and location.

The total area of the atmosphere above Antarctica that suffers from ozone thinning

during the peak season varies from year to year. In 2000, seasonal ozone thinning above Antarctica was the largest ever and covered an area three times the size of the continental United States. However, in 2001 and 2002 its size decreased somewhat. CFCs are attributed for this ozone depletion.

After a dark winter, sunlight returns to Antarctica. This sets into motion reactions

that release large numbers of Cl atoms that initiate the catalytic chlorine cycle. Within weeks, this typically destroys 40-50% of the ozone above Antarctica (and 100% in some places). Huge mass of ozone-depleted air above Antarctica then flow northward and linger for few weeks over parts of Australia, New Zealand, South America, and South Afrcia. This raises biologically damaging UV-B levels in these areas by 3-10% and in some years by as much as 20%. In 1988, it was discovered that similar but usually less severe ozone thinning occurs over the Arctic during the arctic spring and early summer (February-June) with a seasonal ozone loss of 11-38%. When this mass of air above the Arctic breaks up each spring, large mass of ozone-depleted air flow south to linger over parts of Europe, North America and Asia. However, scientists believe that the Arctic is unlikely to develop the large-scale ozone thinning found over Antarctic. According to a 1988 model developed by scientists of NASA, ozone depletion over Antarctic and Arctic will be at its worst between 2010 and 2019. Self-check Exercise 27

· When does the ozone thinning occur in Antarctica? Why? · Is ozone layer depletion over Arctic as similar as in Antarctic? · How do the effects of ozone layer depletion felt over upper latitudes?

Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 10.5.7 MEASURES TO PROTECT OZONE LAYER



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In 1975, the US state of Oregon enacted the world's first ban of CFCs (legislation

introduced by Walter F. Brown). The United States and several European countries banned the use of CFCs in aerosol spray cans in 1978, but continued to use them in refrigeration, foam blowing, and as solvents for cleaning electronic equipment.

Scientists concluded that even with immediate action, it will take 50 years for recovery of ozone layer to pre-1950 levels. By 1985, scientists observed a dramatic seasonal depletion of the ozone layer over Antarctica. International attention to CFCs resulted in a meeting of world diplomats in Montreal in 1987. Representatives of 36 nations met in Montreal, Canada and developed a treaty, called Montreal Protocol. It set the goal of cutting emissions of CFCs into the atmosphere by about 35% between 1989 and 2000. On March 2, 1989, 12 European Community nations agreed to ban the production of all CFCs by the end of the century. Representatives of 93 courtiers met in London in 1990 and in Copenhagen, Denmark in 1992 and adopted the Copenhagen Protocol to accelerate the measures of phasing out of key ozone-depleting chemicals. They decided that by the year 2010, CFCs should be completely eliminated all over the globe including developing countries.

Use of certain chloroalkanes as solvents for large scale application, such as dry cleaning, have been phased out, for example, by the IPPC directive on greenhouse gases in 1994 and by the Volatile Organic Compounds (VOC) directive of the EU in 1997. Permitted chlorofluoroalkane uses are medicinal only.

Finally, bromofluoroalkanes have been largely phased out and the possession of

such equipment is prohibited in some countries like the Netherlands and Belgium, from 1 January 2004, based on the Montreal Protocol and guidelines of the European Union.

Production of new stocks ceased in most (probably all) countries as of 1994. However many countries still require aircraft to be fitted with halon fire suppression systems because no safe and completely satisfactory alternative has been discovered for this application. There are also a few other, highly specialised, uses. These programs recycle halon through "halon banks" coordinated by the Halon Recycling Corporation to ensure that discharge to the atmosphere occurs only in a genuine emergency and to conserve remaining stocks.

On September 21, 2007, approximately 200 countries agreed to accelerate the

elimination of hydrochlorofluorocarbons entirely by 2020 in a United Nations-sponsored Montreal summit. Developing nations were given until 2030. Many nations, such as the United States and China, who had previously resisted such efforts, signed the treaty. 10.5.8 INDIA’S COMMITMENT TO PROTECT OZONE LAYER India became party to the Montreal Protocol in 1992 and also ratified the Copenhagen, Montreal and Beijing Amendments on 3rd March 2003. India’s percapita



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consumption of ODSs (Ozone Depleting Substances) is at present less than 3 g and did not cross 20 g during 1995-97 as against 300 g permitted under the Protocol. India prepared a detailed Country Program (CP) to phase out ODS in accordance with its national industrial development strategy in 1993. The objectives of the CP were to phase out ODS without undue economic burden to both consumers and industry manufacturing equipment using ODSs and provided India with an opportunity to access the Protocol’s Financial Mechanism. The Government of India has entrusted the work relating to ozone layer protection and implementation of the Montreal Protocol to the Ministry of Environment and Forests (MOEF). The MOEF has set up an Ozone Cell as a national unit to look after and to render necessary services to implement the Protocol and its ODS phase out program in India. Further details of India’s commitment can be obtained if interested. 10.5.9 ALTERNATIVES TO CFCs

Work on alternatives for chlorofluorocarbons in refrigerants began in the late 1970s after the first warnings of damage to stratospheric ozone were published in the journal Nature in 1974 by Molina and Rowland (who shared the 1995 Nobel Prize for Chemistry for their work).

Adding hydrogen and thus creating hydrochlorofluorocarbons (HCFC), chemists

made the compounds less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer. Later alternatives dispense with the chlorine, creating hydrofluorocarbons (HFC) with even shorter lifetimes in the lower atmosphere.

By the early 1980s, bromofluoroalkanes were in common use on aircraft, ships and

large vehicles as well as in computer facilities and galleries. However, concern was beginning to be felt about the impact of chloroalkanes and bromoalkanes on the ozone layer. The Vienna Convention on Ozone Layer Protection did not cover bromofluoroalkanes as it was thought, at the time, that emergency discharge of extinguishing systems was too small in volume to produce a significant impact, and too important to human safety for restriction.

However, by the time of the Montreal Protocol it was realized that deliberate and accidental discharges during system tests and maintenance accounted for substantially larger volumes than emergency discharges, and consequently halons were brought into the treaty, albeit with many exceptions.

10.5.10 GREEN HOUSE EFFECT BY CFCs

According to an estimate, the green house effect caused by CFCs would have a far reaching disastrous effect, since CFCs are the major component of green house gases and are responsible for global warming.



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In addition to their role as agents for the catalytic decomposition of stratospheric ozone, chlorofluorocarbons (CFCs) are also important greenhouse gases. They absorb in the range 8 to 12 µm with each CFC having specific absorption bands in this region. Thus CFC-11 absorbs at 9.5µm and 11.5µm, and CFC-12 at 9.5µm and 11.0µm.

The Hydrochloroflurocarbons (HCFCs) also attenuate radiation within the same range, but their residence time in the troposphere is much shorter than that of the CFCs. The rate of increase of the CFCs has declined by a factor greater than two in the past decade, but HCFC concentrations are increasing at a much higher rate.

Three fully fluorinated gases of industrial origin have recently been recognized as potential contributors to global warming. They are present in trace amounts, but have lifetime of thousands or ten of thousands of years. Tetrafluromethane (CF4) and hexachloroethane (C2F6) both are produced during electrolysis of alumina (Al2O3) in cryolite (Na3AlF6) at carbon electrodes. The release of the gases has been estimated to be at about 0.77 and 0.1 kg respectively per ton of aluminum produced. Yet another gas, sulfur hexafluoride (SF6) is formed during magnesium production.


· How do the CFCs cause green house effect? Explain.


10.6 LET US SUM UP In this lesson we have learnt the effects of air pollution on global scale. We understood the green house effect and global warming. We learnt the gases responsible for green house effect. We learnt the acid rain in detail; cause, formation of acid rain and its effects. We also understood the photochemical reactions taking place in the troposphere that lead to the formation of ozone and smog. We studied the effects of ozone and smog on human health. We studied in detail about CFCs and their contribution to the ozone layer depletion and global warming. We also learnt the international efforts undertaken to reduce/eliminate the CFCs and other ozone-depleting substances. 10.7 LESSON-END ACTIVITIES

· Take a sheet of paper and list out the green house gases · Draw a line of spectrum of Infrared radiation and locate the wavelength

regions, that are absorbed by GHGs; also locate the region which is not absorbed by any gas – window region.



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· If you have a refrigerator in you home, find out what refrigerant it is filled with.

· List out the substances that deplete ozone layer.

10.8 POINTS FOR DISCUSSION By now, you are aware of the air pollution problems at global level. Though these are considered to be global problem, their effects will be felt at all levels – local level, regional level and global level. For example, the global warming will melt the polar ice and raise the sea level. This will result in inundation of many coastal villages, towns, and cities. The CFCs and other ozone depleting substances have already thinned the ozone layer over Antarctic and Arctic regions. As a result, the regions near the polar regions are also affected. If the same trend continued, will it cause ozone layer depletion over the entire globe? Answer is not available. However, we can speculate that the effects may be extended all over the globe. Thanks to the Montreal Protocol and its follow-up. The serious steps have been taken to save the ozone layer by the International efforts. Scientists are developing the substances to replace the CFCs. 10.9 CHECK YOUR PROGRESS

· Have you understood the difference between green house effect and global warming?

· Can you distinguish between wet deposition and dry deposition? · Have you realized the importance of replacement of CFCs by alternatives?

10.10 REFERENCES




Dun-Donnelly Publisher, New York, 1976 5. Miller,Jr., G.T. Environmental Science, Working with the earth, Thomson –

Brooks/Cole, 2004 6. www.en.wikipedia.com 7. www.epa.gov


http://www.en.wikipedia.com/


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UNIT - III LESSION 11 AIR POLLUTION MONITORING 11.0 Aims and objectives

11.1. Air pollution monitoring – Introduction 11.2. Objectives 11.3. Methods of air quality monitoring

11.3.1. Ambient air monitoring design - Site selection and selection of sampling equipments

11.3.2. Field survey and planning 11.3.3. General guidelines for site selection 11.3.4. Distance from near by emitters 11.3.5. Spatial scale 11.3.6. Temporal scale 11.3.7. Obstructions and interfering sources 11.3.8. Sampler height 11.3.9. Collocated samplers 11.3.10. Safety 11.3.11. Electrical requirements 11.3.12. Security

11.4. Precautions for sampling, analysis and data reporting 11.4.1. Sampling 11.4.2. Analysis 11.4.3. Data reporting 11.4.4. Abbreviations in the data 11.4.5. Calculation of 24-hourly averages and monthly average

11.5. Let us sum up 11.6. Lesson – End Activities 11.7. Points for Discussion 11.8. Check your Progress 11.9. References

11.0 AIMS AND OBJECTIVES In this lesson 1 we are going to learn about air pollution monitoring. The purpose of monitoring, the methods of monitoring, sampling etc. are discussed and explained. You will become familiar with the monitoring program and learn the designing and planning of monitoring program at the end of the lesson. 11.1 AIR POLLUTION MONITORING - INTRODUCTION Monitoring is a term referring to an act of watching or keeping track of something or some event for a special purpose. Air pollution monitoring is an act of keeping track of air pollution levels in a place for taking necessary action to bring them into safe levels. It is a part of the air quality surveillance program.



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Air quality surveillance is the procedure for assessing the concentrations of atmospheric contaminants and other properties of the air so that air quality management requirements can be met. 11.2 OBJECTIVES The ultimate aim and objective of air quality monitoring is to protect man and his environment from harmful effects of air pollution. The objectives can be spelt as follows: 1. To know the extent of pollution - monitoring will give this information and 2. To know the trends in air quality From these results, control efforts can be regulated accordingly. While undertaking the air quality monitoring program the following factors are to be considered: 1. the needs of the data users (quantity, quality, location, time) 2. available resources (funds, manpower, and facilities available) 3. legal requirements (local, regional, state, national, international) 4. available technology (equipments, techniques) 5. operational criteria (economic, social, legal, cost effectiveness) and 6. operational responsibility There may be different data users with different needs. They will be using the air quality data for the following purposes: 1. to assess the pollution effects on man and his environment 2. to study and to evaluate pollutant interactions and patterns 3. to establish air quality standards 4. to develop control strategies and regulations 5. to evaluate the effectiveness of control measures undertaken 6. to activate emergency procedures to prevent air pollution episodes or reduce their

severity 7. to guide the efforts for minimizing the air pollution impact by applying land use and

other planning system Apart from site location, the quality of air quality monitoring data will depend on the sampling and analytical procedures selected. The following three aspects are to be considered: 1. sampling procedures 2. sampling frequency and 3. analytical techniques Self-check Exercise 1

What are the basic objectives of air quality monitoring?



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Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Basic considerations of sampling: In order to minimize the errors and to optimize the efficiency the following four factors are to be considered: 1. Sample collected must be representative in terms of time, location and the conditions of

study 2. Sufficiently large samples of air must be collected to get accurate results. The volume

of air to be sampled will depend on the expected concentration of the pollutant as well as on the sensitivity of the analytical method

3. The sampling rate must be chosen to provide maximum collection efficiency. 4. The duration and frequency of sampling should accurately reflect the occurrence of

fluctuations in pollution levels. 11.3 METHODS OF AIR QUALITY MONITORING Air quality monitoring can be carried out depending on requirements and the availability of resources. We can choose manual methods or automated methods or combination of both in collecting the data under air quality monitoring program. The choice of the method depends on certain factors such as availability of funds, manpower, facilities, space etc. Thorough planning and designing must be done prior to implementation of the monitoring program. 11.3.1 AMBIENT AIR MONITORING DESIGN - SITE SELECTION AND SELECTION OF SAMPLING EQUIPMENTS

Designing monitoring plan and its implementation involve the following six steps:

1. Field Planning. 2. Spelling out the specific monitoring objectives. For example, whether the

monitoring program should address the particulates with their chemical properties or mere concentrations of RSPM / SPM alone.

3. Determination of matrix of pollutants that need to be measured and at what level they are expected. (In source apportionment study, the objective is to prepare chemical mass balance between the pollution potential of surrounding sources and heir suspected contribution to PM10 /PM2.5 at the receptor end. The potential contributors may first be determined from initial/broad field survey and emissions inventory in the study area. Particle size and their signature chemical constituents



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help in identifying/segregating one source from another. Particle size fractions, chemical analysis, sampling frequencies, and sample durations need to address it. The desired types of analysis and size fractions affect the number of sampling ports and different filter media needed).

4. Calculating the amount of deposit on each filter for each of the chemical species and compare it to typical detection limits for the types of analysis expected.

5. Choice of the sampling system, which provides the most cost-effective and reliable means of meeting the monitoring needs.

6. Creating a plan including adequate Standard Operating Procedures (SOP) on sampling locations, analysis methods, filter-media, sampling systems, sampling frequencies and durations, nominal flow rates, methods and schedules for internal cleaning, calibration and performance tests, filter transport and handling procedures, database management system, data analysis methods, and record keeping protocols.


Briefly describe the ambient air monitoring design.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 11.3.2 FIELD SURVEY AND PLANNING Before site/equipment selection, there is a need to prepare “Field Plan” (FP) and SOP as a first step for field studies. The field planning specifies the details of how the field measurements will be carried out. Key elements include:

· The experimental approach and technical objectives of the network design plan. · Information requirement of new sampling site. · Evaluation of measurement methods with respect to needed averaging time,

detection limits, accuracy, precision, and cost-effectiveness. Continuously versus integrated samples Off-site laboratory analysis

· Specifications for accuracy, precision, validity and completeness of field measurements.

· Time and locations for each category of measurements.

Schedule of milestones and a criteria path diagram showing which operational tasks must be completed prior to undertaking other operational tasks and identify the groups responsible for each task. Filed planning specifies the details of how the field study will be carried out. It identifies measurement locations, observable, monitoring methods, averaging times, and calibration



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methods, specifies data management and reporting conventions, and outline the activities needed to ensure data quality. 11.3.3 GENERAL GUIDELINES FOR SITE SELECTION Guidelines for Site selection refer to the environs surrounding a measurement location, and these differ depending on the zone representation intended for a specific monitoring site. Large nearby buildings and trees extending above the height of the monitor may present barriers or deposition surfaces. Certain trees may also be sources of particulate matter (PM) in the form of detritus, pollen, or insect parts. For example, these can be avoided by locating samplers by placing them>20 m from nearby trees, and twice the difference in elevation difference from nearby major buildings or other obstacles. Another example is for background monitoring sites, which should be located>10 km from large population centers, and >100 m from roads and wood burning (burning is common, though often intermittent, in camping, forested, and agricultural areas). But, here the objective of study is not compliance monitoring but to select “Hot Spots” representing maximum impact zone of different source categories. Compliance PM 2.5/10 monitoring networks do not provide samples amenable to all chemical analyses because of the limitations of single-filter media. Source apportionment and control strategy evaluation require chemical speciation, so different criteria must be considered when these are to be addressed. As such, recommended guidelines are as follow: 11.3.4 DISTANCE FROM NEAR BY EMITTERS The monitor should be located within the zone of influence of sources it represents. It should be located within the designated zone of representation for the monitoring site. Neighborhood and urban zones of representation are needed for community-oriented compliance monitoring. These can generally be at least 1 km from very large, visibly identifiable point source areas occupied by major industries such as cement and steel production or ore processing. Regarding vehicular exhaust and road dust emissions from paved roads, earlier studies provide guidance on the recommended monitoring distances from paved roads with different levels of average daily traffic for neighborhood and urban-scale sites. A minimum distance of ~50 m from busy paved highways is usually out side the road's immediate zone of influence for a roof top monitor. These siting criteria were established for PM10 compliance monitoring siting by U.S.EPA, (1987), and they have their validity in PM10 network design. For larger than middle-scale monitoring requirements, no unpaved roads with significant traffic or residential wood-burning appliances should be located within 100m of the monitoring location. A PM monitor siting evaluation is to ensure simultaneous assessment of local meteorology and also survey of, geology, land use, and PM sources within the defined impact zone. Any local or regional parameters that may affect the ability of the PM monitor data to meet the objectives of the monitoring programme should be considered. Micro inventories aid in



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determining the location of contributing sources and identifying the species that may be present at a location. Micro inventories include detailed surveys and locations of various area sources, storage piles, major highways, construction sites and industrial operations etc. Written descriptions and notes regarding each potential PM source are normally included with the in-situ surveys sheets. 11.3.5 SPATIAL SCALE The spatial scale for the monitoring program depends on its objectives and estimated size of the area of impact of sources of interest. Area of impact of sources, in this study, is taken as 1-1.5 kms around each sampling location.

11.3.6 TEMPORAL SCALE For Canadian and U.S. national survey networks and regional monitoring networks, the temporal scales of greatest interest are annual geometric mean concentration or 24-hour average concentration. Since meteorological conditions change with time, in order to collect representative samples and for considering temporal scale impacts at any siting location, these meteorological changes are taken into account during location siting. The temporal scale selected in this program is 8 hrs to catch diurnal source variations as well as impact of diurnal changes in meteorological settings. 11.3.7 OBSTRUCTIONS AND INTERFERING SOURCES The airflow radius within 2 meters around the sampler should remain unobstructed. Distance from the sampler to obstacle such as buildings must be at least twice the height of the obstacle protruding above the sampler. Distance from trees must be greater than 20 meters. A distance of 5 meters upwind in the most common wind direction must be maintained from building exhausts and intakes. Spacing from roads varies with the height of monitor. Here, the objective of sampling is to cover different “Hot Spots” representing dominance of different sources. 11.3.8 SAMPLER HEIGHT The sampler inlet is proposed to be kept at about 3 m above ground level so that emissions of low height local sources is captured but undue influence of larger size air borne local dust is avoided. 11.3.9 COLLOCATED SAMPLERS If a collocated sampler is required, sufficient clearance for the additional sampler should be provided at the sample location. The spacing between sampler inlets must be =1 m for other PM10 /PM2.5 samplers (sampler with a flow rate less than 16.67 L/min) and =2 m for a HVS sampler (sampler with a flow rate greater than 16.67 L/min). 11.3.10 SAFETY



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An operator must be able to safely reach the sampler location regardless of weather conditions. The operator may often be carrying supplies to the sampling locations. 11.3.11 ELECTRICAL REQUIREMENTS A stable electrical supply must be provided for the primary sampler and any additional samplers to be located at the monitoring site. The sampler is required to operate at 240 volts alternating current (AC) and a frequency of 59-61 hertz (Hz)

11.3.12 SECURITY The security of the monitoring equipment and personnel should be considered in sampler placement. Samplers are often placed on roofs with restricted access. Fenced in sampler locations are also utilized but the fence should be a non-obstructing variety such a chain-link and the sampler inlet must extend above the top of the fence. Central Pollution Control Board of India has also prescribed the precautions to be followed while sampling, analysis and data reporting. They are described below: Self-check Exercise 3

1. What should be the height of the sampler? 2. How will you avoid the effects from obstruction?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 11.4 PRECAUTIONS FOR SAMPLING, ANALYSIS AND DATA REPORTING

11.4.1 SAMPLING The following precautions must be followed in sampling of air pollutants:

1. The high volume sampler (HVS)/respirable dust sampler (RDS) must be properly

calibrated to get the correct flow rate. 2. Corrective and preventive maintenance of the HVS/RDS must be done. 3. The filter used for sampling should be of good quality (having better mechanical

stability, chemical stability, particle sampling efficiency, flow resistance, cost and availability etc.).



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4. Filter should be mounted properly on the support screen with the rough side of the filter facing upwards.

5. The wing nuts should be tightened properly to avoid any leakage. 6. Weighing of filter paper must be done after conditioning in desiccators having

active moisture absorbent. 7. Weighing of filter paper must be done in balance having accuracy of 0.01 mg and

silica gel bottle must be kept in weighing chamber to avoid error while weighing. 8. Distilled water must be used in manometer tube and water must be changed every

fortnightly and zero level must be checked every time. 9. Shelter should be provided at the sampling site for protection of instruments during

rainy season. 10. Ice should be kept in the sampling tray during sampling to avoid evaporation loss

and better absorption. 11. Evaporation loss if any must be made up with distilled water. 12. Proper preservation of samples must be done after sampling. Gaseous samples must

be preserved properly in an icebox or refrigerator (below 5 ° C) prior to analysis.

11.4.2 ANALYSIS The following precautions must be followed in analysis of air pollutants:

1. Properly clean glassware must be used. 2. One set of glassware must be calibrated as per requirement. 3. All critical chemicals used must be of analytical grade. 4. Double distilled or nano-pure water must be used for preparation of reagents and

analysis. 5. Glassware and storage bottles must be rinsed with distilled water and chemicals,

respectively. 6. Reagent bottles must be properly marked by name, strength and date of preparation,

expiry date and initial of chemist who has prepared the reagent. 7. Desiccant in the desiccators must be changed as per requirements. 8. The chemicals whose strength changes with time must be standardized before use. 9. Calibration graphs must be made every time a new stock solution is prepared. 10. Reagent bottles must be made air tight before storage. 11. Key reagents must be prepared fresh on the date of analysis. 12. Storage of chemicals must be done as per recommendations like away from

sunlight, etc. 13. Active silica gel bottles with holes must be placed inside the weighing chamber. 14. The analytical balance must have a sensitivity of 0.1 mg or better.


Explain the precautions followed in sampling and analysis.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………



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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 11.4.3 DATA REPORTING Data must be reported in the prescribed format. The following must be followed for reporting data:

1. SPM/RSPM values, which are very high, should be reported in round figures

(without decimal place). 2. Any outlier values found should be checked for contamination of sample, sudden

change of environmental conditions in the vicinity of the monitoring site, etc. and discarded, if necessary.

3. SPM values must always be greater than corresponding RSPM values. In case Respirable Dust Sampler is used for measuring SPM and RSPM, then, Particulate matter collected on filter paper represents RSPM (size < 10µm). Particulate matter collected in cup below cyclone represents Nonrespirable suspended particulate matter (NRSPM, size > 10µm). Sum of particulate matter collected in cup below cyclone and filter paper gives an indication of SPM.

4. In case SPM is less than corresponding RSPM, then data may be rechecked. 5. The values should not be reported below the detection limit as per the method:

Parameter Lower Detection Limit

Method

SO2 4 µg/m3 Modified West and Gaeke method

NO2 9 µg/m3 Sodium Arsenite method

RSPM and SPM 5 µg/m3 High volume sampling/ Respirable Dust Sampling

For calculating 24 hourly average of various parameters, BDL is considered as half the lower detection limit, i.e.

· For calculating 24 hourly average of SO2, if any 4-hourly average is BDL then for calculation purpose its value is taken as 2µg/m3

· For calculating 24 hourly average of NO2, if any 4-hourly average is BDL then for calculation purpose its value is taken as 4.5µg/m3

· For calculating 24 hourly average of SPM and RSPM, if any 8-hourly average is BDL then for calculation purpose its value is taken as 3µg/m3

11.4.4 ABBREVIATIONS IN THE DATA Abbreviations such as N.D., V.D., I.F., P.F., M/F, P/F, Nil, 0, etc. should not be mentioned in the data sheets.



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Data Values Abbreviations

Values less than Lower Detection Limit B.D.L.

No Monitoring carried out ‘ – ‘

For no monitoring carried out for specific reason, an asterisk ‘*' may be mentioned in the respective place in datasheet and reason maybe mentioned at the bottom of data sheet. Self-check Exercise 5

1. What are the standard methods prescribed for SPM, RPM, SO2 and NOx? 2. What are the lower detection limits for the above pollutants?


11.4.5 CALCULATION OF 24-HOURLY AVERAGE AND MONTHLY AVERAGE Values monitored for 16 hours and more in a day are considered for calculation of 24-hour average. Average of 24-hourly averages (calculated as mentioned above) is taken as monthly average. 11.5 LET US SUM UP In this lesson, we have learned the air quality monitoring in detail.

· We learnt the objectives of monitoring – why should the monitoring be undertaken? · We learnt how to design an air quality monitoring program. · We learnt how to undertake filed survey for planning the monitoring program · We learnt how to select the site for monitoring program · We learnt the spatial scale and temporal scale of the program · We also learnt the precautions to be undertaken while sampling, analysis and data

reporting · We learnt the abbreviations used in the monitoring · We learnt the calculation of the data and reporting of the data.

11.6 LESSON END ACTIVITIES

· Go through the daily news in news paper or in the internet to know the air pollution concentration of your city / town / nearby city

· Find out if there is any monitoring program is carried out in your place; if so by whom



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11.7 POINTS FOR DISCUSSION · Significance of monitoring program · Guidelines for monitoring program

11.8 CHECK YOUR PROGRESS · Can you spell out the need and importance of a monitoring program? · Can you state the precautions to be followed in monitoring program?

11.9 REFERENCES

1. Rao, M.N. and Rao, H.V.N. Air pollution, Tata McGraw Hill Publishing Co. Ltd., New Delhi, 1996

2. WHO, Manual on Urban air quality management, World Health Organization, Copenhagen, 1976

3. www.cpcb.nic.in 4. www.envfor.nic.in 5. www.en.wikipedia.com 6. www.epa.gov


http://www.cpcb.nic.in/

http://www.envfor.nic.in/


http://www.epa.gov/


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LESSION 12 – AIR QUALITY STANDARDS Contents 12.0 Aims and objectives

12.1. Introduction 12.1.1. Development of air quality standards 12.1.2. Whether common single standard or multiple standards?

12.2. Kinds of air quality standards 12.2.1. Ambient air quality standards 12.2.2. Other air quality standards 12.2.3. Emission standards 12.2.4. Ambient air quality standards in selected countries


12.0 AIMS AND OBJECTIVES This lesson will teach us the need for standards. The standards are the values set scientifically by the concerned authorities of a country (in India, CPCB is the authority) for each pollutant deemed to be safe below this value. In this lesson you will learn the types of standards and standards followed in selected countries.

12.1 INTRODUCTION Before we proceed, we must know, what are air quality standards? Air quality standards are the legal limits placed on levels of air pollutants in the ambient air during a given period of time. They characterize the allowable level of a pollutant or a class of pollutants in the atmosphere and thus define the amount of exposure permitted to the population and/or to ecological systems.

They are expressions of public policy and thereby requirements for action. Thus, they are not based solely on air quality criteria but also are based on a broad range of economic, social, technical and political considerations. Air quality standards have evolved differently in different countries depending on exposure conditions, the socio-economic situation, and the importance of other health related problems. 12.1.1 DEVELOPMENT OF AIR QUALITY STANDARDS How are air quality standards developed? Air quality standards are developed in the following sequence:



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1. Preparation of air quality criteria: analyses of the relationship between pollutant concentrations in the air and the adverse effects associated therewith. The WHO calls these “guides”.

2. Development of air quality goals: from air quality criteria air quality goals are developed. They are the concentration of pollutants believed that people can live without adverse effects on health and welfare.

3. Development of air quality standards: from air quality criteria, air quality standards are developed. Air quality standards are the concentration of air pollutants intended to achieve in the immediate future. However, these concentrations may fall short of air quality goals as consideration to feasibility of achievement within the immediate future must be given.

4. Development of standard methods of measurement and testing of the ambient air and the air pollution effects: In order to develop the standards, there must be standards for measurement and testing of the ambient air and air pollution effects; standard methods of measurement of ambient air quality are available – prescribed by USEPA, and WHO internationally and by CPCB in our country.


Describe the steps in development of air quality standards


12.1.2 WHETHER COMMON SINGLE STANDARD OR MULTIPLE STANDARDS?

A major decision must be taken in the adoption of air quality standards; whether there should be one common standard for an entire jurisdiction or different standards for different areas within the jurisdiction. All political jurisdictions within an air quality region would have the same air quality standard. In general, air quality regions would not be contiguous but would be separated by non-urban hinterland. If two separated regions were to expand in area in future until they become contiguous, they would presumably then be merged into one larger air quality region. Since, each air quality region would adopt its own air quality standards; they could differ among the several regions. However, there should be a datum below which no region’s air quality standards should drop.

12.2 KINDS OF AIR QUALITY STNDARDS 12.2.1 AMBIENT AIR QUALITY STANDARDS



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These are the legal limits placed on the concentrations of air pollutants in a community where people and their materials are exposed. Air quality standards are permissible exposure of all living and non-living things for 24 hours per day, 7 days per week. To know if the actual concentrations are in compliance requires an air monitoring program. 12.2.2 OTHER AIR QUALITY STANDARDS

1. Quasi-emission standards: they are also called, “point or impingement standards”. They are the limits on specific pollutants of the ambient air at ground level required by national, state, or local regulations to be used in diffusion computations to determine limits of emission from specific sources.

2. Soiling index: it is the measurement of transmitted or reflected light through or from a spot of particulate matter collected on a filter for a prescribed period of time.

3. Odor standards 4. Visibility standards 5. Standards for particulate matter deposited, etc.

12.2.3 EMISSION STANDARDS They are permitted emission levels for specific groups of emitters. All members of these groups are expected to emit no more than these permitted emission levels. These standards can be applicable to any selected group of emitters and can be national, regional or local in application. They can be based on some air quality standards or can be entirely independent of any such air quality standards, serving as an entirely separate and different type of strategy from air quality management. Emission standards prescribe limits of contaminants discharged into the atmosphere, so that when the standards are met, adverse effects from air pollution will be minimized or eliminated. Once air quality standards are established such standards can be used as the basis for formulating emission standards. The emission standards therefore represent emission levels not to be exceeded if air quality goals are to be achieved. Emission standards can be prescribed for stationary sources as well as for mobile sources. Self-check Exercise 7

1. Define emission standards 2. Define ambient air quality standards

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 12.2.4 AMBIENT AIR QUALITY STANDARDS IN SELECTED

COUNTRIES



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Once again, we shall turn our attention to ambient air quality standards. They are permissible levels of air pollutants in the atmosphere. They imply that the values prescribed in the standards are acceptable pollutant concentrations. Several countries have developed air quality standards which they strive to attain by adopting suitable control measures. The standards developed by certain countries are presented in the following tables: Table 12.1 Air quality standards adopted by EPA in (U.S.EPA)

Standard concentration No. Parameter

µg m -3 ppm Remarks

75 Annual geometric mean 1.

Suspended Particulate Matter (SPM)

260 24 h 80 0.83 Annual mean

2. Sulfur dioxide 365 0.14 24 h

3. Carbon monoxide 10000 9 8 h. Not more than once per year

4. Nitrogen oxides 100 0.05 Annual mean

5. Ozone 235 0.12

1 h daily maximum. Not more than once per year

6. Non-methane hydrocarbons 160 0.24 6-9 h. Annual mean not more than once per year

7. Lead 1.5 3-month average Table 12.2 Air quality standards for SPM and SO2 adopted by different countries

SPM SO2 Country

µg m -3 Averaging time µg m -3 Averaging time Belgium 150 24 hours Bulgaria 150 24 hours 50 24 hours

150

290

Canada Alberta Newfoundland Ontario 290

24 hours

Ontario – residential – rural

60 1 year 50 1 year

Ontario – industrial – cum - commercial

110 1 year 130 1 year

Czechoslovakia 150 24 hours 150 24 hours East Germany 150 24 hours 150 24 hours



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Finland 150 24 hours 250 24 hours France 60 1 year 75 24 hours Israel 150 24 hours Italy 125 24 hours Netherlands 125 24 hours Poland 200 24 hours 75 24 hours Sweden 250 24 hours Switzerland 75 24 hours

USA Colorado

260 24 hours

Delaware- rural 60 24 hours 50 24 hours

Delaware-residential 75 24 hours 80 24 hours Delaware- commercial

95 24 hours 100 24 hours

Delaware- industrial 125 24 hours 160 24 hours

Missouri 120 24 hours

In India, on the basis of land use and other factors, the various areas of a state are classified into three categories by the Central Pollution Control Board (CPCB), which are adopted by State Pollution Control Boards of our country. The classified areas are:

A. Industrial and mixed-use areas B. Residential and rural areas and C. Sensitive areas


Compare air quality standard for SPM in different coutnries Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

Table 12.3 National Ambient Air Quality Standards set by CPCB



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Annual Arithmetic mean: minimum 104 measurements in a year taken twice a week 24

hourly at uniform interval. 24 hourly/8 hourly values should be met 98% of the time in a year. However, 2% of the time, it may exceed but not on two consecutive days. 12.3 LET US SUM UP In this lesson we have learnt the need and significance of air quality standards. We also learnt the air quality standards prescribed by EPA and other agencies in other countries. We have learnt the standards prescribed by CPCB in our country. 12.4 LESSON-END ACTIVITIES

· Take a sheet of paper and write down the standards prescribed by CPCB · Compare the CPCB standards with EPA standards · Go through the News paper and find out the air pollutant concentration of your

place or nearby place and check whether the value is below the standard or exceeding the standard


· By now you are aware of importance of standard · Development of air quality standards

12.6 CHECK YOUR PROGRESS · Can you describe the development of air quality standards?

Concentration in ambient air (µg m-3)

Pollutant Time weighed average

Sensitive areas

Industrial areas

Residential, rural and other areas

Annual 15 80 60 Sulfur dioxide

24 hours 30 120 80 Annual 15 80 60

Nitrogen oxide 24 hours 30 120 80 Annual 70 360 140

Suspended particulate matter 24 hours 100 500 200

Annual 50 120 60 Respirable particulate matter 24 hours 75 150 100

Annual 0.50 1.0 0.75 Lead

24 hours 0.75 1.5 1.00 8 hours 1.0 (mg m-3) 5.0 (mg m-3) 2.0 (mg m-3)

Carbon monooxide 1 hour 2.0 (mg m-3) 10.0 (mg m-3) 4.0 (mg m-3)



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· How many areas / zones are categorized in the National Ambient Air Quality Standards Set by CPCB?

12.7 REFERENCES


2. WHO, Manual on Urban air quality management, World Health Organization, Copenhagen, 1976

3. www.cpcb.nic.in 4. www.envfor.nic.in 5. www.en.wikipedia.com 6. www.epa.gov





http://www.epa.gov/


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LESSON 13 – SAMPLING METHODS FOR ATMOSPHERIC

POLLUTANTS Contents 13.0 Aims and objectives

13.1. Introduction 13.2. Estimation of Particulates

13.2.1. Estimation of Suspended Particulate Matter using High Volume Sampler 13.2.2. Estimation of Respirable Particulate Matter using Respirable Dust

Sampler 13.2.3. Estimation of Sulfur dioxide 13.2.4. Estimation of NOx as NO2 – Jacob & Hochheiser method 13.2.5. Estimation of total oxidants 13.2.6. Methylene blue method for H2S analysis 13.2.7. Estimation of carbon monoxide 13.2.8. Estimation of Carbon dioxide 13.2.9. Estimation of hydrogen fluoride


13.0 AIMS AND OBJECTIVES In this lesson we are going to learn the sampling and analytical methods of particulates and gaseous contaminants. In order to compare the pollutant concentration of different places and at different times there must be consistency and accuracy of the sampling and analytical methods. The standard methods are prescribed by the international agencies like USEPA and UNEP and WHO. In our country, the CPCB is the agency which set the standards for sampling and analysis. 13.1 INTRODUCTION In general, a sampling system for atmospheric pollutants consists of four component subsystems:

1. intake and transfer component 2. collection component 3. flow measuring component and 4. air moving component

Malfunction in any one component will affect the successful performance of the whole system.



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Intake and transfer component: intake component is the portion of the device through which the pollutants enter into the sampling equipment. It may vary from a thin-walled probe to a relatively large area used for collection of dust samples. Transfer component is the portion of the device that transports the pollutants from intake component to the collection component. It includes the tubes, roof housing arrangements etc. Collection component: collection component is a part of the device, on / in which the samples are collected. It may be a filter on which particulates are sampled or a glass impinger in which gases are sampled. Flow measuring component: in air sampling, the total volume of air sampled is to be measured for computing concentration. For this purpose, the flow meters are used that measure the flow of the air sampled per unit of time. From this, the volume of air sampled can be calculated and then concentration. Air moving component: it is the part of the equipment which drives the air from outside atmosphere into the collection component of the equipment through the intake and transfer component. It may be a blower or small pump. Self-check Exercise 9

What are the 4 sub-systems of the sampling system?


13.2 ESTIMATION OF PARTICULATES Particulates are either solid or liquid discrete particles present in the atmosphere. All solid and liquid particles in the air that are small enough not to settle out on to earth’s surface under the influence of gravity. Suspended particulates are a composite group of substances, liquids or solids dispersed in the atmosphere, which range in diameter from a fraction of a micron to several hundred microns. The most significant fraction of suspended particulate matter is the respirable size, i.e. larger than about 0.1 µm and smaller than about 5-10 µm. Particles of this size range persist in the atmosphere longer than other sizes. Particles of this size range reduce visibility of atmosphere and enter into various atmospheric reactions. There are many methods available for estimating the particulates in the atmosphere. Gravimetric High-Volume method is widely used.



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Particulates can be collected using High Volume air Sampler (HVS) or Respirable Dust Sampler (RDS). High Volume Sampler gives the total suspended particulate matter present in the atmosphere while, Respirable Dust Sampler, the particulates of repirable size (10 µm and below). They are designated as PM10. 13.2.1 ESTIMATION OF SUSPENDED PARTICULATE MATTER

USING HIGH VOLUME SAMPLER Principle: ambient air is drawn under a fixed area gable roof and through a filter by means of heavy duty turbine blower at a constant flow rate ranging between 1.1 and 1.7 m3 per minute. Suspended particles having diameters between 0.1 and 100 µm are removed from this air stream by filtration on a glass fiber filter. The mass concentration (in µg m-3) of suspended particulates is determined by measuring the mass of the collected particulates and dividing by the volume of air sampled. Procedure:

1. Filter preparation: Whatman GF-A glass fiber filter is widely used. The filter is exposed to a light source and inspected for pinholes, particles or other imperfections (if there is any such imperfection, the filter should be discarded and the presence of small particles can be removed with a small brush). The filter is handled with care not to fold or to crease. The filter is conditioned before and after sampling to remove the moisture content of the filter. The filter is weighed to the nearest mg with care to avoid the formation of sharp creases.

2. Sample collection: the pre-weighed filter is placed in position with rough side up on the filter holder. The filter is firmly placed by tightening the wing nuts. It was closed with the roof and the sampler is now ready for operation. The sampler is switched on. The initial and final flow rates are noted down. The exposed filter is then removed and folded with the exposed surface facing each other and put in a polythene bag and transported to the laboratory. After conditioning, the final weight is determined. From the difference between final weight and initial weight, the amount of suspended particles is determined and their concentration is calculated.


What is the purpose of conditioning the filter before and after sampling? Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 13.2.2 ESTIMATION OF RESPIRABLE PARTICULATE MATTER

USING RESPIRABLE DUST SAMPLER



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Principle: ambient air is drawn through the inlet pipe and passed through the cyclone and then to filter placed on the filter holder. The filter holder is closed from direct exposure to the atmosphere. When air is passed through the cyclone, coarse particles will be separated from the air stream and collected in a conical hopper. The fine dust forming repirable fraction of the total suspended particulates are collected on the filter. The mass of the particulates collected on the filter is the amount f respirable particles while the mass of the particulates collected in the hopper provides the amount of non-respirable particulates. Procedure: the filter is prepared and conditioned as done for high volume sampler. The conical hopper also is conditioned and weighed before and after sampling. Mass difference of the hopper before and after sampling gives the amount of coarse (non-respirable) particulate matter. All other steps are same as that done with high volume sampler. 13.2.3 ESTIMATION OF SULFUR DIOXIDE (West and Gaeke method) Sulfur dioxide is generated by combustion of sulfur-containing fossil fuels and certain industrial processes like smelting, sulfuric acid plant and petroleum refining. Principle: SO2 present in the air is absorbed by passing the air through a solution of potassium tetra chloro mercurate (TCM). SO2 reacts with TCM to form a stable, non-volatile dichloro sulphitomercurate ion. When purified and acid-bleached para rosaniline and formaldehyde are added to it, intensely colored para rosaniline methyl sulphonic acid is formed. The concentration of SO2 is determined from the intensity of the color formed. Reagents:

1. Absorbing reagent: 10.86 g mercuric chloride, 5.96 g potassium chlorkde and 0.066 g EDTA (disodium salt) are dissolved in distilled water and made up to 1 liter with distilled water. It is stable for 6 months.

2. Sulphamic acid: 0.6 g sulphamic acid is dissolved in 100 ml distilled water. It is stable for few days.

3. formaldehyde (0.2%): 1.0 ml 40% formaldehyde is dissolved in 200 ml distilled water. It should be prepared daily.

4. Sodium acetate-acetic acid buffer (1 M): in a 100 ml volumetric flask , 13.61 g sodium acetate trihydride is taken and dissolved with distilled water. To this, 5.7 ml glacial acetic acid is added and then diluted up to the mark with distilled water.

5. Phosphoric acid (3 M): 205 ml H3PO4 (85%) is diluted to 1 liter with distilled water.

6. Pararosaniline stock solution: in a large separatory funnel, 100 ml each of 1-butanol and 1 N HCl are equilibrated. 0.200 g pararosaniline hydrochloride is dissolved completely in 100 ml equilibrated 1 N HCl. It is allowed to stand for several hours and then purified as follows: Purification of pararosaniline: the contents are transferred into a separatory funnel and 20 ml equilibrated 1-butanol is added to it. After shaking well for about 10 minutes, the funnel is kept undisturbed for about 30 minutes. The violet impurity is separated into organic phase (upper layer). The lower layer is then transferred into a third separatory funnel and the process is repeated several times until all the



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impurities are completely removed. After final extraction, it is filtered through a cotton plug into a 100 ml volumetric flask and made up to the mark with 1 N HCl.

7. Stock sulfite solution (approximately 0.4 µg SO2 ml1: 0.400 g sodium sulfite or 0.300 g sodium metabisulfite is dissolved in 500 ml previously boiled and cooled distilled water. It must be standardized.

8. Standard sulfite solution: required volume of freshly standardized stock sulfite solution is accurately pipetted out and diluted with absorbing solution to get a set of standards.

Procedure: air is passed through a glass impinger containing 30 ml absorbing solution. Sampling is done for a required period of time. Any water loss is compensated by adding distilled water. 10 ml sample (from bubbler) is pipetted out into a 25 ml volumetric flask. 5 ml distilled water, 1 ml sulphamic acid are added to it and allowed to stand for 10 minutes. 2 ml formaldehyde and 5 ml pararosaniline are added in sucession to it and diluted with distilled water. The absorbance is determined at 548 nm. SO2 is determined from calibration curve prepared using standards. Self-check Exercise 11

Describe the principle of SO2 estimation using West-Gaeke method


13.2.4 ESTIMATION OF NOX AS NO2 - Jacob & Hochheiser (Modified

Na-Arsenite Method) Nitric oxide (NO) and nitrogen dioxide (NO2) are the two major oxides of nitrogen present in the polluted atmosphere. Fossil fuel combustion is the main source for emission of NO. In fact, the combustion sources emit mostly in the form of NO. But NO in the atmosphere readily gets oxidized to form NO2. Almost all the NO emitted will become NO2. Since, NO and NO2 form greater fraction of oxides of nitrogen, the term oxides of nitrogen (NOx) is widely used to refer to these two oxides of nitrogen. The method prescribed measures only NO2 not NO. However, this method is called method for NOx based on assumption that all NO emitted is converted readily into NO2. Principle: NO2 is collected by bubbling air through the sodium hydroxide-sodium arsenite solution to form stable sodium nitrite. The nitrite ion produced is reacted with phosphoric acid, sulphanilamide and N-1-(naphthyl) ethylene diamine dihydrochloride to form an azo dye and then determined spectrophotometrically at 540 nm. Reagents:



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1. Sodium hydroxide-sodium arsenite solution (absorbing solution): 4.0 g NaOH is dissolved in distilled water. 1.0 g sodium arsenite is added to it and diluted to 1 liter with distilled water.

2. Sulphanilamide solution: 20 g sulphanilamide is dissolved in 700 ml distilled water. 50 ml conc. Phosphoric acid is added to it with mixing and diluted to 1 liter with distilled water.

3. NEDA solution: 0.5 g N-1-(naphthyl)-ethylene diamine dihydrochloride (NEDA) is dissolved in distilled water and dilute to 500 ml. It should be stored in a brown color bottle.

4. Hydrogen peroxide solution: 0.2 ml of 30% H2O2 is diluted to 250 ml with distilled water.

5. Stock sodium nitrite solution: sufficient desiccated sodium nitrite is diluted to 1 liter with distilled water to yield a solution containing 1000 µg NO2

- ml-1. The amount of NaNO2 dissolved is calculated as follows:

Where, G = amount of NaNO2 in grams 1.500 is gravimetric factor in converting NO2 into NaNO2

6. Standard sodium nitrite solution: dilutions are made from the stock solution to yield

a set of standard solution. Procedure: known volume (usually 35 ml) of absorbing solution is taken in the bubbler and the air is passed through it at flow rates in the range of 1 to 2 liters min-1. After sampling, evaporative loss is compensated with distilled water. 10 ml sample is pipetted out into a 25 ml volumetric flask. 1 ml H2O2, 10 ml sulphanilamide and 1.4 ml NEDA are added in succession to it. It is allowed to stand for 10 minutes. The absorbance is measured at 540 nm and the concentration is determined from calibration curve (standard graph) prepared from the set of standards. Self-check Exercise 12

Describe the principle of NOx analysis

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 13.2.5 ESTIMATION OF TOTAL OXIDANTS

G = 1.500 × 100

A



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Total oxidants: total oxidants are compounds present in the atmosphere capable of oxidizing a chemical reagent which is not oxidized by molecular oxygen. Total oxidants in atmosphere include, O3, H 2O2, organic hydroperoxides and peroxides, peracids, peroxyacylnitrates, NO2 and Cl2. The oxidants present in the atmosphere can only be determined by chemical methods. They may be determined by either colorimetric or coulometric method. Neutral KI method: this method determines the oxidants in the range of 0.01 to 10 ppm. O3, Cl2, H2O2 and organic peroxides when absorbed in a neutral buffered (pH = 6.8 ± 0.2) solution of KI, liberate I2. The liberated I2 is measured spectrophotometrically by determination of the absorption of the tri- iodide ion at 352 nm. Apparatus Absorber: all glass midget impingers with a graduation mark at 10 ml can be used. Other bubblers with nozzle or open-ended inlet tubes may also be employed. Flow rate: air can be sampled at the rate of 1 to 2 liters min-1. A glass rotameter can be used for measuring the flow rate. Reagents: Absorbing reagent: it is prepared by dissolving 13.61 g of potassium dihydrogen phosphate, 14.20 g of anhydrous disodium hydrogen phosphate and 10.00 g of KI successively and diluting to exactly to 1 liter with double distilled water. The solution can be stored for several weeks in a glass stoppered brown bottle in a refrigerator. Standard I2 solution (0.05 M): it is prepared by dissolving successively 16.0 g of KI and 3.173 g I2 in double distilled water and making up to 500 ml. It can be stored for one day at room temperature before using. It may be standardized by titration with sodium thiosulfate solution using starch indicator. SO2 absorber: it is optional. It is mainly used to avoid the interference from SO2. Flash-fired glass fiber filter is impregnated with chromium trioxide as follows: 15 ml of aqueous solution containing 2.5 g chromium trioxide and 0.7 ml conc. H2SO4 were dropped uniformly over 400 cm3 filter and dried in an oven at 80 to 90 °C for 1 hour. It is stored in a tightly capped jar. Half of this paper is sufficient to pack one absorber. The filter is cut into 6 × 12 mm strips each folded into a V shape. The strips are packed into an 8.5 ml U tube and conditioned by drawing dry air through it overnight. Procedure: the sampling train is arranged in order of the SO2 absorber, impinger, rotometer and air pump. The sample probe should preferably be of PTFE but glass or stainless steem may be used for short probes. PVC should be avoided. Exactly 10 ml of absorbing solution is pipetted out into the impinger. The air is drawn through the sampler for up to 30 min. The reagent should not be exposed to direct sunlight.



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After sampling, the distilled water is added to compensate evaporative loss. The absorbance of the sample is measured at 352 nm by transferring the portion of the sample into the cuvette. From the standard graph prepared from the standard solutions of I2 the concentration of total oxidants can be obtained and expressed in terms of O3. Ozone: it is the most abundant and important oxidant present in the atmosphere. O3 is highly reactive gas and reacts with a variety of chemical reagents. However, so far, specific chemical analytical method has not been developed. Theoretically three physical methods are available, viz. chemiluminescence method, ultraviolet absorption method and infrared absorption method. But chemiluminescence method is employed for measurement of tropospheric ozone. In this section, we shall learn the chemiluminescence method. Ozone by C2H4 – chemiluminescence method: ozone reacts rapidly with C2H4. This reaction accompanies with chemiluminescence emission in the wavelength region of 350 to 600 nm. This light emission is monitored with a sensitive photomultiplier. The signal obtained is directly proportional to the O3 concentration. The method is suitable for measurement of ozone in the range 0.001 to 100 ppm. Using “chemiluminescence ozone analyzer”, atmospheric ozone concentrations can be determined. Self-check Exercise 13

Describe the principle of measurement of total oxidants


13.2.6 METHYLENE BLUE METHOD FOR H2S ANALYSIS H2S is collected by aspirating air through an alkaline suspension of cadmium hydroxide Cd(OH)2. The sulfide is precipitated as cadmium sulfide. The sulfide is reacted with a strong acid solution of N, N-dimethyl-p-phenylenediamine and ferric chloride. Apparatus: A midget impinger is used to aspirate air through it. Reagents:

1. Amine-H2SO4 (stock): 50 ml conc. H2SO4 was added to 30 ml distilled water. After cooling, 12 g N, N-dimethyl-p-phenylenediamine dihydrochloride is to be added and mixed well for complete dissolution.



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2. Amine-H2SO4 (working): 25 ml of the above (stock) solution is diluted to 1 liter with 1:1 H2SO4.

3. Ferric chloride solution: 100 g ferric chloride hexahydrate is dissolved in water and made up to 100 ml.

4. Ammonium phosphate solution: 400 g diammonium phosphate is dissolved in water and diluted to 1 liter.

5. Absorbing solution: 4.3 g cadmium sulfate octahydrate and 0.3 g NaOH are dissolved separately and then mixed together. 10 g of STRaction 10 (arabinogalactan) is added to it and diluted to 1 liter. It is stable for 3 to 5 days only and hence should be prepared freshly. It should be shaken vigorously before use.

6. Standard sulfide solution (stock): a stock solution containing approximately 400 µg sulfide ion ml-1 is made by dissolving in 1 liter 0.1 M NaOH, either gaseous H2S or sodium sulfide monohydrate crystals. The solution should be standardized with standard iodine and thiosulfate solutions.

7. Standard sulfide solution (diluted standards): a set of standard solutions are prepared by appropriately diluting the stock solution in the range of 1 to 5 µg sulfide ion ml-1.

Procedure: air samples are aspirated through 10 ml absorbing solution taken in a midget impinger. Excessive foaming during aspiration can be controlled by the addition of 5 ml ethanol just prior to sampling. After sampling, 1.5 ml of amine working solution is added to the absorbing solution in the impinger. 1 drop of FeCl3 solution is added to it and the contents are transferred to a 25 ml volumetric flask. 1 drop of ammonium phosphate solution is added and the solution is made up to the mark with distilled water. Ammonium phosphate solution is added to discharge the yellow color of ferric ion. It is allowed to stand for 30 min. and the color developed is measured at 670 nm against a reagent blank. The concentration of H2S is determined using the calibration curve (standard graph) prepared using standard solutions.


Describe the principle of H2S estimation Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

13.2.7 ESTIMATION OF CARBON MONOXIDE



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Several instrumental methods are available for the measurement of CO. They include electrochemical, non-dispersive infrared (Ndir) and gas chromatographic methods. In this section we shall limit our learning to non-dispersive infrared method only since it is highly reliable one. Principle: the technique involves determining the difference in infrared energy absorption over all wavelengths passed by the optical system between gas sample containing the compound of interest and a sealed reference sample consisting of an infrared transparent gas. The assumption is made that this difference in energy absorption is directly proportional to the concentration of the subject compound in the sample gas. Detection of the energy is accomplished through absorption of the residual infrared energy by a mixture of the subject compound with an inert gas in a sealed detector cell. Only that energy absorbed is defined as the absorption spectrum of the compound. This absorbed energy is converted into heat producing a change in pressure or volume of the gases in the detector. The unequal volume change between the sample and reference cell is converted into an electrical signal directly related to the CO concentration. CO concentration is measured following the procedures supplied by the manufacturer of the instrument. Self-check Exercise 15

Describe the principle of CO estimation

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 13.2.8 ESTIMATION OF CARBON DIOXIDE Principle: a dual column/dual thermal conductivity detector gas chromatograph is used to separate and measure the quantities of O2, N2, CO, CO2 and CH4 in gas samples. The sample is introduced as a plug into the carrier gas, and after drying in a desiccant tube it passes successively through two carefully matched gas chromatography columns. The first column contains a very polar stationary liquid phase while the second is packed with molecular sieve 13-X. Detectors are placed at each end of the column. The first column retains only CO2, which is eluted after passage of the rest of the mixture (the composite peak). The first detector thus records two peaks, one corresponding to the unresolved O2, N2, CH4 and CO and another to CO2. The gases are swept into the molecular sieve column. This column separates all the components. The second detector records the elution of O2, N2, CO and CH4. The CO2 is



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irreversibly absorbed on molecular sieve 13-X and does not elute. Peak heights are used in conjunction with calibration plots for quantitative measurements of these gases. Any commercially available gas chromatograph equipped with necessary accessories can be used for analysis of CO2. Carbon monoxide can also be determined by this method. Self-check Exercise 16

Describe the principle of CO2 estimation

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 13.2.9 ESTIMATION OF HYDROGEN FLUORIDE Major sources of fluorides include primary aluminium manufacture, open hearth steel production, coal burning for power, the fertilizer industry and cement , brick, tile and ceramic industries. Less significant sources of emission include glass manufacture, hydrogen fluoride production and high octane fuel production. Principle: atmospheric samples are taken using midget impingers containing 10 ml of 0.1 N NaOH. Samples are diluted 1:1 with Total Ionic Strength Activity Buffer (TISAB). The diluted samples are analyzed using fluoride ion selective electrode. Apparatus:

1. The midget impingers are used for passing the air through NaOH solution. By connecting the impinger a air sampling device air sample can be collected.

2. Fluoride selective electrode 3. Expanded scale millivolt pH meter

Reagents:

1. Absorbing solution (0.1 N NaOH): 4 g sodium hydroxide pellets are dissolved in double distilled water and diluted to 1 liter.

2. Sodium hydroxide (5 M): 20 g sodium hydroxide is dissolved in distilled water and diluted to 100 ml.

3. Total Ionic Strength Activity Buffer (TISAB): 500 ml double distilled water is taken in a 1- liter beaker. 57 ml glacial acetic acid, 58 g sodium chloride 0.30 g sodium citrate are added to it and stirred well. The beaker is placed in a water bath and 5 M NaOH is added slowly until reaching the pH between 5.0 and 5.5. After cooling, the contents are transferred into a 1 liter volumetric flask and diluted with double distilled water.

4. Standard fluoride solutions: 4.2 g of sodium fluoride is dissolved in double distilled water and diluted to 1 liter in a volumetric flask. The solution gives



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0.1 M F-. From this dilutions can be made and a set of standards can be prepared.

Procedure: the sample is carefully transferred to a 50 ml plastic beaker. 10 TISAB is added to it and diluted to 25 ml with double distilled water and stirred well. The fluoride selective electrode and reference electrode are lowered into the stirred solution and the resulting mV reading is recorded. The concentration is determined from the calibration curve prepared from standards. Self-check Exercise 17

Describe the principle of HF estimation


13.3 LET US SUM UP In this lesson we have learnt the sampling and analytical methods of both particulates and gaseous contaminants. We learnt the basic principles of the available methods and procedures. 13.4 LESSON-END ACTIVITIES

Take a sheet of paper and write down the principle in estimation of a) SPM b) RPM c) SO2 d) NOx

13.5 POINTS FOR DISCUSSION · Differences in estimation methods of SPM and RPM · Challenges faced in sampling and analysis

13.6 CHECK YOUR PROGRESS · Can you describe the principle and procedure for estimation of SPM and RPM? · Can you describe the methods for gaseous contaminants?

13.7 REFERENCES 1. Rao, M.N. and Rao, H.V.N. Air pollution, Tata McGraw Hill Publishing Co.

Ltd., New Delhi, 1996 2. Harrison, R.M. and Perry, R. Handbook of air pollution analysis, Chapman and

Hall, London, 1986 3. www.cpcb.nic.in 4. www.envfor.nic.in





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5. Katz, M. Methods of air sampling and analysis, American Public Health Association, 1977



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LESSON 14 – CONTROL OF GASEOUS CONTAMINANTS Contents

14.0 Aims and objectives

14.1. Control of gaseous contaminants by adsorption 14.2. Control of gaseous contaminants by absorption 14.3. Control of gaseous contaminants by condensation 14.4. Control of gaseous contaminants by combustion 14.5. Let us sum up 14.6. Lesson-end Activities 14.7. Points for Discussion 14.8. Check your Progress 14.9. References

14.0 AIMS AND OBJECTIVES We are going to learn the control methods available for gaseous contaminants. Gaseous pollutants can be controlled by a wide variety of devices. A suitable device is chosen considering cost-effective, and collection efficiency factors. Even after selecting the best technique, monitoring should be carried out to ensure the emissions meet the emission standards. 14.1 CONTROL OF GASEOUS CONTAMINANTS BY ADSORPTION It involves passing a stream of effluent gas through a porous solid material (adsorbent) contained in an adsorption bed. The surfaces of the solid material attract and hold the gas (the adsorbate) by either physical or chemical adsorption. Physical adsorption: gases and vapors condense on solids at temperatures above dew point, depends upon van der Waals force. Van der Waals force is an attractive force existing between atoms or molecules of all substances. The force arises as a result of electrons in neighboring atoms or molecules moving in sympathy (affinity) with one another. The amount of gas adsorbed relates to the case of condensation of the gas – the higher the boiling point, the greater the amount adsorbed. Physical adsorption is directly proportional to the amount of solid surface available. The total surface area can be increased by building up a number of molecular layers on the surface. For example, use of the activated carbon provide increased surface area by creating large internal pore structure. Physical adsorption is accompanied by capillary condensation within the pores, which substantially increases the amount of gas that can be adsorbed. Physical adsorption liberates small amount of heat during adsorption of gases. By lowering pressure or raising temperature, the adsorbed gas can be desorbed without any chemical change. Self-check Exercise 18



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Define physical adsorption Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

Chemical adsorption: it is also called chemisorption. In this process, the contaminant gas reacts chemically with the adsorbent to form a chemical bond. However, chemisorption is much slower than physical adsorption. It results in the formation of a single layer of molecules on the solid surface, and the process is usually irreversible due to occurrence of chemical change. The amount of gas adsorbed depends upon pressure and temperature. Types of adsorbents: a number of materials possess adsorptive properties. Some of the adsorbents used in air pollution control are listed in table 14.1. Table 14.1 Types of available adsorbents and their use

Adsorbent type Major uses Activated carbon To eliminate odors, to purify gases and to recover solvents Alumina To dry air, gases and liquids Bauxite In treating petroleum fractions, drying gases and liquids Magnesia To treat gasoline and solvents, to remove metallic impurities

from caustic solutions Molecular sieves To control and recover Hg, SO2 and NOx

Silica gel To dry and purify gases In general, there are two types of adsorbents: having affinity towards polar and non-polar vapors/gases. For example, water vapor, a polar vapor is attracted by alumina, bauxite and silica gel. Hence, these adsorbents are used as drying agents. Conversely, the organic vapors are attracted by activated charcoal. Molecular sieves such as synthetic silicates or zeolites can be used and they can be tailored in such a way to adsorb only certain vapors/gases. Molecular sieves made from crystalline metal aluminosilicates are capable of recovering SO2 even up to 99%. Certain other molecular sieves are proven to remove NOx to an extent of 50%. However, use of molecular sieves will be highly expensive. In adsorption, preferential affinity between the adsorbent and adsorbate is crucial for achieving maximum efficiency. The surface-volume ratio is another important parameter in determining the adsorption capacity. Large surface-volume ratios provide increased adsorption. Surface-to-volume ratios can be increased by activating the adsorbent. Activated carbon, the most common adsorbent, is prepared by carbonizing wood, fruit pits, or coconut shells at very high temperatures and treating them with steam to burn away the



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carbon material. As a result, a large internal pore structure is created providing exponentially large surface area. Adsorption equipments: three types of adsorbing equipments are available, viz. fixed bed adsorbers, moving bed adsorber and fluidized bed adsorber.

1. Fixed bed adsorber: it is simple; either vertical or horizontal cylindrical shell in structure. The adsorbent is arranged on beds or trays in layers 1.3 cm thick in thin-bed adsorbers and greater in deep-bed adsorbers.

2. Moving bed adsorber: in this unit, the adsorption bed is contained in a rotating drum. The filtered air containing gaseous pollutant is forced by the fan into the rotating drum section. The air enters into the adsorption bed and passes through it then leaves at the ends of the drum.

3. Fluidized adsorber: it contains a shallow, floating bed of adsorbent. When the air flows upward, the bed expands and fluidized providing intimate contact between the contaminant gas and the adsorbent.

Adsorption units are highly efficient until a breakpoint occurs when the adsorbent becomes saturated. When saturation occurs, it can be detected by increased concentration of the pollutant gas. At this point, the adsorber must be regenerated or renewed. Adsorbers can be classified as regenerative and non-regenerative. The adsorbed gas can be resorbed either for recovery or for disposal in regenerative adsorber and the adsorber is regenerated. In non-regenerative adsorber, the gas cannot be resorbed and hence, adorber is not regenerated. Due to this, adsorbent of the non-regenerative adsorber must be discarded after saturation and it must be replaced with new material. Self-check Exercise 19

What are the three adsorbers?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 14.2 CONTROL OF GASEOUS CONTAMINANTS BY ABSORPTION In this method, the contaminated effluent gas (adsorbate or solute) is brought into contact with a liquid absorbent (solvent). During this contact, the effluent gas is removed, treated or modified by the liquid absorbent. Liquid absorbent may either react chemically with the gas or simply dissolve the gas thereby remove the contaminant gas.



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For example, water and limestone can be used to remove SO2 from flue gases. Water reacts with the limestone to form calcium hydroxide [Ca(OH)2] which then reacts with SO2 to form calcium sulfate salt. It is scrubbed by the addition of more water. In this way water and limestone serve as reactive absorbent. The non-reactive absorbent does not react with the gas but dissolve the gas and thereby removes from the gas stream. Absorption is used primarily in the control of gases such as sulfur dioxide, oxides of nitrogen, hydrogen sulfide, hydrogen chloride, chlorine, ammonia and some light hydrocarbons. Absorption is being employed in many industries for removal of hydrocarbons. This technique is also useful in recovering the hydrocarbons thereby increasing the profit of the industry. Self-check Exercise 20

Describe the principle of absroption

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Absorbent: gas solubility differs from solvent to solvent. Solvents that are chemically similar to the solute generally provide good solubility. Viscosity of the solvent also determines the solubility of the gas. Lower the viscosity; the greater will be the solubility. Other factors to be considered are as follows:

1. ideally a solvent should have low freezing point 2. it should be relatively non-volatile 3. it should be nonflammable 4. it should be chemically stable 5. it should be relatively inexpensive 6. it should be readily available 7. it should be non-corrosive

Removal of SO2 by absorption: by using absorption technique, SO2 is removed with the efficiency up to 80 to 90%. The main absorbents used in the various SO2 absorption processes are aqueous solutions of the alkalies (sodium and ammonia) and the alkaline earths (calcium and magnesium). Use of sodium is advantageous as it is non-volatile and does not produce any fume problems. Use ammonia has another advantage that the SO2 reacts with ammonia to form ammonium sulfate, a useful by-product.



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Magnesium oxide (MgO), calcium oxide (CaO) and calcium carbonate (CaCO3) are the alkaline earth compounds used as absorbents for removal of SO2. In magnesia process, use of MgO form Mg(OH)2 with water and this in turn reacts with SO2 to form MgSO3. Calcination will yield a stream of SO2 and regenerate MgO. The SO2 can be concentrated and used for manufacture of sulfuric acid while the MgO regenerated can be used once again as absorbent. Absorption devices: a number of gas absorption devices are available to provide intimate contact between the gas and the liquid. The available absorption units are: spray towers, plate or tray towers, packed towers, and venturi scrubbers. Spray towers: they are capable of handling large volumes of gas with relatively little pressure drop and reasonably with high efficiency. Spray towers can also remove particulates and serving the dual purpose. For efficient absorption of gas, two conditions are to be met:

1. smaller droplet size and 2. greater turbulence

For production of fine droplets, high pressure nozzles are to be used which consume more energy than do the low-pressure nozzles. In a typical spray tower, the absorbing liquid is sprayed from the top of the tower. As the absorbing liquid falls downward, the contaminant- laden gas is passed from the bottom – counter-current flow. During this counter-current flow, the gaseous contaminant comes into contact with the falling droplets of absorbing solution and is absorbed. Moisture eliminators placed near the outlet remove the moisture content of the cleaned gas. The absorbent with contaminant gas is collected at the bottom and disposed either with or without further treatment. Since spray towers provide much less gas- liquid interfacial area they are generally less effective when compared with that of other absorbing devices. However, they are less expensive.



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Figure 14.1 Spray tower (above and below)

Plate or tray towers: they contain horizontal trays or plates which provide large liquid-gas interfacial areas. The absorbent enters from the side of the column near the top and spills across the top sieve tray and then descends to other trays one after the other. The trays are spaced 0.3 to 0.9 m apart and arranged alternately inside the tower. This facilitates the liquid to flow in a zigzag manner to reach the bottom of the column. The contaminant-laden gas is passed from the bottom upward and as it moves upward, it comes into contact repeatedly with the falling liquid and the contaminant gas is absorbed. The plate towers can be designed with either sieve plates or bubble-cap trays. In bubble-cap trays, the contaminated gases rise upward until they strike the caps, at which point they are diverted



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downward and discharged as small bubbles from slots at the bottom of the caps. As the gas moves upward, the liquid-gas contact continues and the contaminant gas is absorbed. Packed towers: in a packed tower, packing is used to increase the contact time between contaminant gas and liquid. The material chosen for packing has a large surface-to-volume ratio and large void ratio that offers minimum resistance to gas flow. Light weight and virtually unbreakable, packing is used. The contaminant- laden gas and the liquid are passed in counter-current flow as done in other towers. The falling liquid from the top flows through the packing and spreads on the surface of the packing as thin film thus providing more contact area to the rising gas.

Figure 14.2 Packed tower Venturi scrubbers: the contaminant- laden gas is passed through the venturi throat and the liquid is introduced in the throat region and both the gas and liquid come into close contact as they move together. During this process, the contaminant gas is absorbed and removed. The clean gas stream moves to the exit.



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Figure 14.2 Venturi scrubber

14.3 CONTROL OF GASEOUS CONTAMINANTS BY CODENSATION

A substance will condense at a given temperature if its partial pressure is increased until it is equal to or greater than its vapor pressure at that temperature. If the temperature of a gas is reduced to its saturation temperature, its vapor pressure equals its partial pressure and condensation will occur. In air pollution control system, the temperature of the gaseous mixture is reduced so that it is equal to the saturation temperature of the contaminant gas. As temperature of the system comes equal to the saturation temperature, the contaminant gas starts condensing. There are two types of condensation equipment: surface condenser and contact condenser. Surface condenser: in surface condensers, contaminants are adsorbed onto a cool surface as the gaseous compound condenses. Air or water is used as a cooling medium and it is circulated through the tubes. The gaseous contaminant vapor condenses on the outer surface of the tubes. Thus condensed vapor forms as a film of liquid and the liquid drains off through the outlet for condensate. Contact condenser: the vapor and liquid are brought into direct contact. The cold water is sprayed from the top and as this cold water droplets fall downwards. The contaminant-laden gas is passed from the bottom of the condenser and it comes into contact with the falling droplets of cold water. During this contact the vapor is cooled down to the saturation temperature and condenses. Self-check Exercise 21

Describe the principle of condensation technique

Note: Please do not proceed unless you write answers for the above two in the space given below:



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……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

14.4 CONTROL OF GASEOUS CONTAMINANTS BY COMBUSTION We all know that combustion is a major source of air pollution. But combustion can also be used to control certain air pollutants. In this method, partially combusted products like CO and hydrocarbons are converted into innocuous carbon dioxide and water. Combustion equipments for control of these gases are designed to bring the oxidation process near completion to a maximum extent. Four important factors are essential for complete combustion to occur:

1. sufficient amount of oxygen 2. temperature of the system 3. turbulence of the system 4. adequate residence time for complete oxidation to occur

Soot, carbon monoxide and other hydrocarbons are produced by incomplete combustion due to insufficient amounts of oxygen available. Therefore, a sufficient amount of oxygen is essential for complete oxidation. Temperature of the system will determine the rate of oxidation. Hence, the temperature must be kept at ignition temperature. Turbulence keeps the oxygen well mixed in the combustion zone. By providing baffles or injection nozzles, the turbulence is created inside the system. Combustion chambers are designed to provide enough time for complete burning to occur; it can be accomplished by increasing the height of the chamber. There are three types of combustion methods are available. Based on the type of contaminant and its concentration, the combustion method can be chosen. They are:

1. direct flame combustion 2. thermal combustion and 3. catalytic combustion

Direct flame combustion: in this method, the flares are usually open ended combustion units located at the top of a stack and equipped with pilots to ensure continuous burning. Waste gases are burned directly in a combustor with or without supplementary fuel. Though flare burning is a relatively safe means of disposing of the large quantities of highly combustible waste gases, they may cause formation of oxides of nitrogen due to high temperatures at the flare. Thus new air pollutant is created. If the fuel-air ratios and other factors are not kept at desired levels, the flares may produce visible smoke or soot. The heat produced by the flares go waste in the atmosphere.



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Thermal combustion: the waste gas is preheated by use of a heat-exchanger utilizing heat produced by the thermal incinerator itself. The preheated gas is directed into the combustion zone, where the waste gas is burned and completely oxidized. The burner may be supplied with supplementary fuel for burning. The temperature of operation depends upon the nature of contaminant gases present. Thermal afterburners must be carefully designed to provide safe, efficient operation. Thermal afterburners are capable of burning the malodorous gases of visible plumes and converting them into odorless steam plumes. Hence, they are useful in controlling emissions from industries that produce malodorous gases. Catalytic combustion: when combustible materials in the waste gas are too low, this method is preferred. A catalyst is used in this method which accelerates the rate of oxidation without itself undergoing any chemical change. Use of catalyst reduces the residence time for complete oxidation to occur. Catalytic combustion brings down the residence time to the extent of 20 to 50 times. A catalytic incinerator consists of pre-heating section and catalytic section. A fan is used to mix the gases and distribute them evenly over the catalyst. As preheated gas is forwarded towards the catalyst, the oxidation is pushed forward. During this, the catalytic surface glows. Well designed catalytic incinerator can remove the waste gases with efficiency between 95 and 98 percent. Catalytic combustion process is used to control SO2, NOx, hydrocarbons and CO. Monsanto Corporation designed the catalytic incinerator for removal of SO2. The dust- free waste gas is passed through vanadium pentoxide (SO2-oxidation catalyst) at 454 °C. This process yields sulfuric acid mist which is collected as a useful product. A palladium(II)/copper(II) catalyst has been developed to oxidize CO to CO2 at ambient temperatures. We have so far discussed in general, the control methods available for gaseous contaminants. Now, we shall see the control methods available for certain gases. Self-check Exercise 22

Describe the principle of combustion technique


14.5 LET US SUM UP



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In this lesson, we have learnt the methods of control of gaseous pollutants. We have studied adsorption, absorption, combustion and condensation methods available. Choice of method depends on many factors such as type of contaminant, volume of contaminant to be removed, cost, etc. The principle of these methods are described in detail.

14.6 LESSON-END ACTIVITIES · Take a sheet of paper and write the principle of adsorption · Take a sheet of paper and write the principle of absorption · Draw the diagram of a absorption tower and practice it

14.7 POINTS FOR DISCUSSION · Compare the adsorption and absorption and discuss · Compare the combustion processes and discuss

14.8 CHECK YOUR PROGRESS · Can you explain the adsorption technique? · Can you explain the absorption technique? · Can you explain the combustion technique? · Can you explain the condensation technique?


Ltd., New Delhi, 1996 2. Peavy, H.S., Rowe, D.R. and Tchobanoglous, G. Environmental Engineering,

McGraw Hill Book Co., New York, 1985 3. Davis, M.L., and Cornwell, D.A. Introduction to Environmental Engineering,

McGraw Hill, Inc., New York, 1991



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LESSON 15 - CONTROL METHODS FOR SELECTED GASEOUS

CONTAMINANTS – SO2, NOX, CO AND HYDROCARBONS


2.1. Control of NOx pollution 2.2. Contorl of SOx pollution 2.3. Control of CO pollution 2.4. Control of Hydrocarbon pollution 2.5. Let us sum up 2.6. Lesson-end Activities 2.7. Points for Discussion 2.8. Check your Progress 2.9. References

15.0 AIMS AND OBJECTIVES In the previous lesson we have learnt the control methods for gaseous contaminants in general. In this lesson, we are going to learn the control methods specifically for SO2, NOx CO and Hydrocarbons.

15.1 CONTROL OF NOx POLLUTION The following steps can be undertaken to minimize NOx emissions:

1. To decrease the generation of NOx by decreasing the flame temperature by injecting re-circulated flux gases, water or steam.

2. Two-stage combustion process has been suggested to remove NOx. 3. To remove NOx formation by catalytic decomposition. To achieve this two

interesting proposals have been suggested: a. To decompose NO into N2 and O2 catalytically

2NO - N2 + O2 K=9 X 1010 at 500oC Where K is the equilibrium constant for the decomposition. However, the presence of catalyst such as CO3O4 > CuO > Cr2O3 > ZnO decelerate the reaction in this order. NO is unstable thermodynamically but kinetically it is stable.

b. the other important suggestion is to combine NO with CO catalytically, thus getting rid of both the noxious pollutants at the same time as:

NO + CO › ½ N2 + CO2



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4. NOx can be removed from stack gas by chemical sorption employing alkaline scrubbing solutions or sulfuric acid solutions. NO is converted into N2O3 which can be easily absorbed.

NO2 + NO › N2O3

Alkaline scrubbing process includes following steps:

a. Oxidizer – Here flue gas and NO2 are injected

NO2 + SO2 + H2O › H2SO4 + NO

b. Scrubber – NO and NO2 react to form N2O3 which is then scrubbed with H2SO4 in a scrubber.

NO2 + NO › N2O3

N2O3 + 2H2SO4 › 2NOHSO4 + H2O

c. Decomposer – The reaction product obtained from scrubber is then decomposed.

2NOHSO4 + ½O2 +H2O › 2H2SO4 + 2NO2

d. Nitric act reactor – NO2 with H2O produce nitric acid

3NO2 + H2O › 2HNO3 + NO

Excess NO and NO2 are circulated again through the oxidizer

5. NOx from the stack gas can be removed by catalytic reduction of NO with CH4 (methane), NH3 (ammonia), and CO (carbon monoxide)

4NO + CH4 › 2N2 + CO2 + 2H2O

6NO + 4NH3 › 5N2 + 6H2O

2NO + 2CO › N2+ 2CO2

Disadvantage – undesirable byproducts like SO2 so formed react with CO to form

highly toxic carbonyl sulphide (COS) 3CO + SO2 › 2CO2 + COS

6. Spark retard is an effective measure to control NOx and hydrocarbon emissions. NOx level from 5000 ppm can be lowered upto 1000 ppm by using this technique.

7. Catalytic exhaust reactions can be used to eliminate nitric oxide from vehicular exhaust.




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800 °C

Describe alkaline scrubbing process


15.2 CONTROL OF SOX POLLUTION SOx can be controlled by the following important methods:

1. Removal of sulfur from fuel before burning 2. Use of fuels with low sulfur content 3. Removal of SOx from fuel gases 4. Using other energy sources for fuel gases 5. Use of natural gas 6. Use of nuclear power to generate electricity from power plants

About 15% of SO2 emission is caused by oil combustion. Generally fuel oil distills over or left as residue in boiler during vaporization. While refining, the distillate gets separated from the residual mixture leaving behind low contents of sulfur. The sulfur contents in distillates merely accounts for 0.05 – 0.35 % by weight. Substitution of energy sources is a better technique which can solve SOx pollution problem. For example, hydroelectric plants need no fuel, so they are free of SOx pollution. The removal of three forms of sulfur (pyrites, sulfates and organic sulfides) from fuel before burning can be achieved by adopting physical techniques. However, coal can be converted to gas by gasification process. In this process, powdered coal reacts with steam and oxygen in a fluidized bed at a high pressure ranging from 600-1000 psi. The products formed constitute H2, CO2, CO, CH4 and H2S. CO and H2 react to form CH4 thereby reducing sulfur contents. Some refining processes are also operated in petroleum industries which lower the sulfur content by 2.5% to 3%. Huge investment and heavy recurring costs are involved in the current technology for removal of SOx from flue gases. However, double alkali process has been used commercially to some extent. SO2 is scrubbed off by two alkalies i.e. Ca(OH)2 and NaOH, in two steps. Foster Wheeler Energy Corporation, USA has developed a new process, in which SO2 is reduced to elemental sulfur, using coal as the reducing agent

C + SO2 › CO2 + S The process, called redox process, uses pre-concentrated flue gas. Not only does the process removed SO2 from the emission, but it yields high purity sulfur also.



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Removal of SO2 from flue gases can also be done by introducing limestone into combustion zone of the furnace. 2CaCO3 + 2SO2 + O2 › 2CaSO4 + 2CO2

Flue gases can be passed through slurry of milk of lime. CaCO3 absorbs SO2 very efficiently. However, CaSO4 in large amounts possess a waste disposal problem. SO2 has also been removed from the flue gases by the use of a reaction between bisulphate ions (from SO2 and citrate ions). About 99% SO2 from flue gas can be removed by this procedure. The flue gas is cooled to 50 oC or lower and made free from particulates and traces of H2SO4. It is then introduced into an absorption tower where it comes in contact with citrate ions, H2- Cit-.

SO2 + H2O - HSO3 + H+

HSO3- + H2 – Cit

- - [ HSO3.H2-Cit]2- The solution is then led into a closed vessel in which H2S gas is passed. As a result, sulphur is precipitated. It is melted and removed from the solution.

[ HSO3.H2-Cit]2- + H+ + H2S › 2S+H2 – Cit - + 3H2O A part of sulphur is converted into H2S and used in the process. The smelting industry is also adopting some catalytic oxidation methods to convert SO2 into H2SO4. The acid so produced can be used internally during smelting operations. Thus by applying any of these methods, SOx emission can be controlled to a great extent. Self-check Exercise 24

Describe the method developed by Foster Wheeler Energy Corporation, USA for

control of SO2 Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

15.3 CONTROL OF CO POLLUTION 1. The possible sinks which oxidize CO into CO2 in the atmosphere are atomic oxygen, hydroxyl radical, NO2, N2O, O3 and excited oxygen molecules. Hydroxyl free radical (OH•) oxidizes CO to CO2 as follows:



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Soil

Bacteria

Soil

Bacteria

•OH + CO › CO2 + H•

•H + O2 + M › HOO• + M

HOO• + CO › • OH +CO2 Where, M is the third body and HOO• hydroperoxy radical. 2. The major CO sinks are some soil microorganisms, e.g. a potting soil sample weighing 2.8 kg is capable of completely removing CO in three hours by microorganisms, i.e. 120 ppm CO from ambient air. The same soil when sterilized, failed to remove CO from air. About 16 fungi are playing an acting role in the conversion of CO to CO2 out of 200 microorganisms, isolated from soil. The reaction occur as: CO + ½ O2 CO2

CO + 3H2 CH4+ H2O CO + OH• CO2+ •H

Where •OH is hydroxyl free radical Today the annual input of CO in the air by man’s activities is expected to double its concentration in the ambient air every 5 years. But the actual rise in ambient (0.1 ppm) global CO content is much below due to the presence of soil bacteria. 3. Plants are world’s natural pollutant sink of CO and CO2. They fix and metabolize CO also with the help of chlorophyll in light and in dark photosynthetically and non-photosynthetically. It was reported in 1903 when some botanist reported that nasturtium leaves produce starch from CO in CO2- free air, when illuminated. However, not all CO is removed by this way. It is also converted into CO2 which then metabolized. Thus the fixation of CO by plants is of immense importance as the green plants are major global sink of CO. This CO absorption by plants increases linearly with the increase of CO concentrations. Therefore, in cities where CO concentration is higher, the rate of CO absorption by plant may be greater by a factor 10 to 100. Thus plants play a vital role in global CO sink. Thus planting of trees and green vegetation will solve the problem of CO to a considerable extent. The combustion technology can be adopted in industries to control the CO which will oxidize the CO into CO2. Supplementary fuels may be used in the combustion chamber. Self-check Exercise 25

Describe the role of microorganisms in controlling CO

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………



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……………………………………………………………………………………………………………………………………………………………….

15.4 CONTROL OF HYDROCARBON POLLUTION Hydrocarbons and NOx produce PAN and O3 etc. which are chronic secondary pollutants. So their control ultimately depends on the control of the primary precursors i.e. hydrocarbons and NOx which are the main culprit of air pollution. Hydrocarbons from auto exhaust emission can be controlled by applying the techniques like incineration, absorption, adsorption and condensation etc. By adopting these methods, all the three pollutants (hydrocarbons, NOx and CO) can be converted into less harmful end products. Hydrocarbons CO + H2O CO CO2 15.5 LET US SUM UP In this lesson we have seen in detail about the control of certain gaseous pollutants specifically. We have seen the scientific principle involved in these methods. Choice of the method again depends upon the feasibility and cost involved. 15.6 LESSON-END ACTIVITIES

· Write the chemical reactions in the control of NOx · Write the chemical reactions in the control of SOx


· Role of microorganisms in controlling CO. · Chemistry of control methods

15.8 CHECK YOUR PROGRESS · Can you describe the control method for NOx? · Can you describe the control method for SO2?


Ltd., New Delhi, 1996 2. Peavy, H.S., Rowe, D.R. and Tchobanoglous, G. Environmental Engineering,

McGraw Hill Book Co., New York, 1985 3. Davis, M.L., and Cornwell, D.A. Introduction to Environmental Engineering,

McGraw Hill, Inc., New York, 1991

Combustion

Combustion



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UNIT - IV LESSON 16 – RADIATION POLLUTION Contents 16.0 Aims and objectives

16.1. Introduction 16.2. Sources of radiation

16.2.1. Natural sources 16.2.1.1. Solar rays 16.2.1.2. Environmental Radiations 16.2.1.3. Radio nuclides in Earth’s crust 16.2.1.4. Internal radiation

16.2.2. Anthropogenic sources 16.2.2.1. Medical X-rays 16.2.2.2. Radio isotopes 16.2.2.3. Nuclear tests 16.2.2.4. Radioactive fallout 16.2.2.5. Nuclear reactors 16.2.2.6. Radiations from nuclear power plants 16.2.2.7. Nuclear installations 16.2.2.8. Radioactive ore-processing 16.2.2.9. Industrial, medical and research use 16.2.2.10. Electric fields 16.2.2.11. Miscellaneous sources

16.3. Types of radiation 16.4. Effects of radiation

16.4.1. Effects of ionizing radiation 16.4.2. Effects of non-ionizing radiation 16.4.3. Effects of fallout radiation 16.4.4. Biological effects of radiation 16.4.5. Effects of X-rays 16.4.6. Effects of Plutonium 16.4.7. Effects on plants 16.4.8. Effects on polymers


16.0 AIMS AND OBJECTIVES In this lesson we are going to learn the radiation, types of radiation and their effects. Any undesirable change in physical characteristics of the environment is also included in the definition of pollution. In fact, radiation is a form of energy emitted by radiating



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substances / radioactive substances. These substances emit radiation by being at their own place or they may be emitted as radionuclide particles into the environment and in turn they emit radiation into the environment. You will be learning all the above in this lesson. You will be able to identify the sources, types and magnitude of harmful effects in this lesson. You will be surprised or even shocked to know the undesirable and harmful effects caused by radiation. It is the worst form of pollution of the other pollutants. The damages caused by radiation are often irreversible.

16.1 INTRODUCTION

Radiation is the term used to refer to the emission of any rays, wave motion or particles (e.g., alpha particles, beta particles, neutrons) from a source. Our environment receives the radiation both naturally and from human activities. Radiation is applied to the emission of electromagnetic radiation.

Electromagnetic radiation is a form of energy radiated in the form of a wave as a result of the changing electric and magnetic fields. There are many different forms of electromagnetic radiation, each with a different wavelength and energy content. It is shown in figure 16.1. Figure 16.1 The spectrum of electromagnetic radiation

Such radiation travels through space at the speed of 300,000 km s-1. Cosmic rays, gamma rays, X-rays, and ultraviolet radiation are ionizing radiation as they have high energy to ionize the atoms by knocking out electrons from the atoms. The resulting electrons and positively charge ions are capable of causing damaging effects on living cells and thereby causing health problems such as cancer.

The other forms of energy are non-ionizing radiation and they do not possess as high energy as ionizing radiation hence, harmless. The visible light which we perceive through our eyes is non- ionizing radiation and does not cause any such adverse effects. Self-check Exercise 1

Wavelength in meters (not to scale)

10-14 10

-12 10-8 10

-7 10-6 10

-5 10

-3 10-2 10

-1 1

High energy, short wavelength

Low energy, long wavelength

Ionizing radiation Nonionizing radiation

Cosmic rays

Gamma rays

X rays Far ultraviolet

waves

Near ultraviolet

waves

Visiblewaves

Near infrared waves

Far infrared waves

Microwaves TV waves

Radio waves



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What are the two types of radiation?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.2 SOURCES OF RADIATION

Living organisms are continuously exposed to a variety of radiation sources which are categorized as follows.

· Natural sources and · Anthropogenic sources

16.2.1 NATURAL SOURCES

There are four types of sources include; 1. Solar rays 2. Environmental radiation 3. Radionuclide’s in earth crust 4. Internal radiation

16.2.1.1 SOLAR RAYS

Solar rays coming from the sun keep a steady drizzle of gamma rays, cosmic rays and heavy particles. Solar storms vastly intensify these showers, but the earth’s atmosphere shields us from most dangerous radiations. Solar radiations consisting of cosmic rays are highly energetic particles (109MeV) which reach the earth’s surface from different galaxies. 16.2.1.2 ENVIRONMENTAL RADIATIONS

Radioisotopes of naturally occurring radioelement release enormous amount of radiations in the form of alpha, beta and gamma rays. Besides, radioisotopes, additional radiations emanate from soil, rocks, air and ground water. Radioactive elements occurring mainly in lithosphere comprise uranium, thorium, radium, isotopes of potassium and carbon (C-14). These radiations mix and interact with natural particulate materials in the atmosphere enhancing the extent of radio-pollution. In marine water, sediments have higher concentration of radioactive isotopes.



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Uranium and thorium extensively occur in nature and are contained in ores, rocks, soils, and river and sea waters and in animal and plant organisms. From soils, the natural radioactive elements are passed to plants and from plants to animal organisms. In addition to uranium, thorium and their decay products, radio active isotopes of K, Ca, Rb, Sn etc are also found in nature. 16.2.1.3 RADIONUCLIDES IN EARTH’S CRUST

Radio active materials such as uranium (U -238), thorium (Th – 232), and potassium (K – 40) which are widely distributed in earth’s crust give rise to the phenomenon referred to as terrestrial activity. Radio active potassium (K -40) constitutes 0.012 % of natural potassium, while rubidium (Rb – 87) constitutes of 28% of natural rubidium. Thus K -40 is considered to be responsible for 20 to 80% radioactivity in the soil. Rubidium occurs less abundantly in the earth’s crust so it is relatively less distributed in the environment. Radon (Rn 222) and its immediate daughter nuclide radium – A through radium –C are the common radio active isotopes in radio active springs.

A gaseous emission of radio-radon is produced during mining of uranium which on

decay yields long lived polonium and radio- lead that enter into the soil and ground water. On an average, a man receives about one rad per year from terrestrial radiation and it may be as high as 2000 m rad per year in areas where uranium containing rocks exist.

16.2.1.4 INTERNAL RADIATION

Generally radiations originate within our bodies, particularly during the decay of potassium in our muscles. Besides potassium, radioactive elements such as uranium, thorium, strontium and carbon (C-14) exist in minute quantities in human’s body. Radioactive materials that emit alpha or beta particles are known as internal emitters because these rays severely affect the living tissues on absorption or ingestion. The radio active substances that emit gamma rays called external emitters because these are highly penetrating and can produce their effects without being absorbed inside the body. Some metabolic important radio nuclides which release radiations in the body include calcium, cobalt, iodine, phosphorus, carbon, iron, manganese and hydrogen etc. Self-check Exercise 2

How does internal radiation occur? Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.2.2 ANTHROPOGENIC SOURCES



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Recently man-made sources have begun to add large doses of radiation to the

existing natural radio active pollution to which our bodies have got accustomed with several ill effects. The major artificial sources include:

a. Medical X-rays b. Radio- isotopes c. Nuclear tests d. Radioactive fallout e. Nuclear reactors f. Nuclear power plants g. Nuclear installations h. radioactive ore processing i. Electric fields j. Industrial, medical and research use of radio active materials k. Miscellaneous sources

16.2.2.1 MEDICAL X-RAYS

Medical X-rays constitute about 18% of artificial radiations used in radiotherapy for diagnostic purposes. These rays are highly penetrating like the gamma rays. X-ray exposure is cumulative in the body and creates chronic defects in the internal organs. Recently a United Nations Committee had reported that radiation from medical sources accounts for diseases resulting from genetic damage. 16.2.2.2 RADIO ISOTOPES

Radioisotopes administered to patients during radiation therapy are now proving to be a hazardous source of nuclear pollution. The ability of radiations to kill deceased cells leaving mainly the normal ones unaffected had made them as indiscriminate tool in the diagnosis and cure of some lethal diseases like cancer. However the indiscriminate use of radio nuclides, their over doses to patients and improper handlings have resulted in dangerous nuclear pollution.

16.2.2.3 NUCLEAR TESTS

During atmospheric nuclear explosion tests, large quantities of long lived nucleotides are released to the atmosphere which gets distributed all over the world. Generally the test including nuclear fission and fusion processes uses uranium (235U) and plutonium (239Pu) as fission materials and lighter nuclei such as hydrogen, lithium or beryllium as fusion elements. Wagner (1971) have reported that when an atom bomb is detonated, about 50%, of the energy released goes into the blast, 35% is dissipated as heat and 15% is released as radioactive. The radioactive dust that falls to the earth after atomic explosion is known as radioactive fallout. It becomes suspended to a height of about 7-8 km above the earth’s surface that may disperse by air-currents around the world.

Actually during nuclear explosion, the radio active products are vaporized to hot gases due to greater force of explosion and very high temperature. These radioactive



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materials are ejected high into the air as extremely fine particles posing atmospheric pollution through radioactive fallout. The radioactive materials formed by nuclear explosions are absorbed by the atmospheric dust as well as rain water and gradually settle to the earth surface at distant places from the explosion site for a long time after the explosion or blast. 16.2.2.4 RADIOACTIVE FALLOUT

The atomic explosions not only produce the local ionizing radiations but also the radioactive isotopes, which enter the atmosphere and continue to fallout gradually over broad geographic areas for a very long time. This is known as nuclear fallout or radioactive fallout. This fall out is dangerous for life because it also produces ionizing radiations. Radioactive fallout mainly consists of radioactive particles discharged into the air during explosion test. It also includes their decay products along with radio activated dust that rises from the bomb crater.

Radio isotopes suspended in air may come down to soil and water in the form of radioactive rain. Radioactive fallout causing radiation pollution is two types:

1. Early fallout 2. Delayed fallout

Early fallout: If the nuclear explosion is at a very low altitude, it sucks up large quantities of soil and water affecting severely all the living organisms. The fire ball also condenses in heavy particles falling back to the earth in a short time. The radioactive pollutants are carried by wind in different directions posing several ill effects. It causes lot of damage even at places remote from the site of explosion. Delayed fallout: if the nuclear explosion occurs at a high altitude, it sucks little dirt and water. The delayed or world wide fallout may be polluting both troposphere and stratosphere with radio-materials. The fission products may be injected into the air and spread every where to several kilometers.

About 80% of the fallout from small and big atomic weapons is deposited on the ground, about 5% passes into the lower atmosphere and the debris settles on the land in few weeks. The remaining 15% which is made up of small particles, goes to the upper atmosphere, gets widely dispersed in the air and may comedown in rain at long distances and enter the food chain. This indicates that total amount of radioactivity decreases with distance from the site of the explosion. Self-check Exercise 3

Explain the following:

a) Nuclear fallout b) Early fallout c) Delayed fallout



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Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.2.2.5 NUCLEAR REACTORS

The leakage of nuclear reactions from nuclear reactors, nuclear research laboratories, medicines and industries is also on the increase with the increase in number of such facilities. In nuclear reactors, structural materials and components become radioactive when exposed to radiation and generate active corrosion products in the reactor effluents. Such activation products are formed by fast neutron (n,p) or thermal neutron (n,r). Operation of nuclear reactors: The processed nuclear fuel is introduced into the reactor, the operation of which is the major contribution of radiation pollution. The sequential processes include – (a) Fission process (b) Activation process (c) Thermal process

Some nuclear reactors use U-238 ore as the basic raw material. This has to be processed by purification, enrichment with U-235 and then manufactured into fuel elements. This fabrication results in the production of solid, liquid and gaseous wastes as radio pollutants. Even the wastes of nuclear reactors, called radio active wastes contain vast amounts of long lived radionuclides. Nuclear reactor wastes: Following types of wastes are generated by reactors;

a. Fission products remaining in both the primary and secondary fuels b. Extraneous activation products in the coolant c. Gaseous wastes of several nuclides comprising C-14, H-3, Xe-133, I-131, Kr-85,

Ar-41, Fe-54 and I-129 etc d. Liquid wastes containing H-3, Co-58, Fe-55, Co-59 and other corrosion products

are also produced e. During chemical treatment to separate the reusable components of U-235, U-238

and Pu-239 from waste fission products, highly active radioactive wastes are produced.

16.2.2.6 RADIATIONS FROM NUCLEAR POWER PLANTS

Nuclear power plants are more convenient to run. Once fuelled, they can operate for several months. These plants are different from conventional electricity generating plants. In the fuelled plants, fossil fuel is burnt to produce heat. The fuel used in nuclear plants, being radioactive is critically dangerous and the waste materials are equally so. No power plant is having perfectively contamination proof. Leakage may occur from several points which may be chronically radioactive.



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Radioactive waste generated by nuclear power plants

1. Low level radioactive liquid waste: Radioactive wastes in solution coming from

power plants contaminate with aquatic life. These radio elements are eventually conveyed to man from water supplies to food chain through soil, vegetation or live stock.

2. Gaseous and particulate radio wastes: Stack effluents from atomic power plants contain gaseous and particulate radio isotopes such as H-3, C-14, Kr-85 and I-129 etc. Some of these radionuclides have long half- lives and may be distributed in the environment for several years.

3. Fission fragments: The largest volume of radioactive wastes comes from reprocessing of irradiated fuel. These radionuclides include Sr-90, I-131, Cs-137 and Co-58 etc.

4. Release of tritium: the heavy water reactors contain high tritium (H-3) inventories because of its production through irradiation of deuterium (D2) in heavy water (D2O). Tritium is also released from primary coolants in which lithium hydroxide is added to slow down corrosion in PWR.

5. Heat release: In power plants, atomic pellets of uranium metal are used as fuel in nuclear reactors which contain three million times as much potential energy as fossil fuel. An estimate showed what one ton of uranium produces as much energy as 12 million barrels of oil.


What are the sources of radioactive wastes?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.2.2.7 NUCLEAR INSTALLATIONS

Dangers posed by power plant installations due to proliferations of plutonium and other isotopes are astounding. In many industries, e.g. those concerned with power generation, radio active isotopes are used as fuel. After the nuclear fuel has been burned up in the nuclear reactor, the spent fuel so formed is transferred to the processing plant and then to the burial ground or to some other form of container. In reprocessing plant, fission products are removed from the spent fuel

16.2.2.8 RADIOACTIVE ORE-PROCESSING

Radioactive ores of uranium like pitchblende and uranites as well as thorium are used in nuclear processes. U-235 undergoes natural fission and emits radiations such as



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alpha, beta and gamma. The half life periods of U – 235 is 4.5x109 years. The disintegrated products formed constitute 88

226Ra and 21082 Pb which are extremely dangerous emitting

radiations naturally a n d 23892 U and 232

90 Th are employed as artificial fissionable radioactive elements.

During milling for recovery of uranium, process effluents are released as slurry with other residues to a tailings pond from which the effluents drain away to join public waters. Of all the radionulides, radium-226 is considered to be the most dangerous due to its longer half life, its biochemical properties, its highly energetic radiations and its immediate fission to daughter radionuclides.

Besides radioactive elements, chemical contaminants such as chromium, manganese, sulfate and nitrate are also present as effluents in water. Chemical treatment of monazite also forms highly toxic effluents. All these processes, mining, washing, refining, separation and milling etc. cause nuclear pollution. All the treatments during ore processing result in the release of radioactive gases which subsequently adsorb on the particles present in the atmosphere. Uranium and thorium ores form dusts in air posing deleterious effects on living organisms.

16.2.2.9 INDUSTRIAL, MEDICAL AND RESEARCH USE

Thermal power plants, fertilizer firms and other industries involved in large scale coal combustion could be a major threat of radiological pollution. This finding is based on the investigation on the extent of radiological pollution caused by the burning of coal in the steam and power generation units at a fertilizer plant at Sindri in Bihar. However, the level of radioactivity released and its exposure to the population through the fly-ash produced daily was found to be well within the maximum permissible limits as recommended by the International Commission for Radiological Protection.

A scientific investigation has found that radioactive contamination from the productions of plutonium for the former Soviet Union’s nuclear weapons was far higher than was ever believed. Since 1948, the Mayak nuclear complex has leaked 8900 beta Becquerels of radioactive isotopes strontium – 90 and caesium-137 into the environment. Accidents and deliberate discharges from Mayak have polluted hundreds of lakes, over 200 km of county side. According to scientists, it is the most radioactive contaminated area of the world. The Russian scientists say that anyone gone near Lake Karachay for a few hours may suffer from radioactive sickness.

Radionuclides administrated to patients during medical diagnosis used in radiation therapy and scientific research laboratories have proved to be the main source of nuclear pollution. X-rays, light gamma rays (γ) are the most dangerous. They have extremely high penetrating power and can destroy the internal body tissues and inflict serious burns quite rapidly. X-rays are also a form of cosmic radiation and can ionize the atoms in the living tissues. Although certain radiations have proved as indispensable tool in curing lethal diseases and have the ability to kill diseased cells, but radiation effects are dangerous even at lowest levels. Even then radiations are frequently used to destroy the malignant cells of tumor, sterilizing medical products and foodstuff by killing bacteria, tracking progress of



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medicines through the body with radioisotopes and attacking cancer cells and stones from within the cells of body.

The nuclear pollution from research laboratories is also bound to increase in future with the increase in technology. The radiations coming from research work take the form of particle. Some come in the form of alpha, beta rays and others in the form of highly energetic electromagnetic waves i.e. X-rays and gamma rays. There are neutrons too, emitted by devices that humans make. Self-check Exercise 5

How are X-rays harmful? Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.2.2.10 ELECTRIC FIELDS

Electrical gadgets and power transmission lines generate electric fields causing environmental radiation hazard. Scientists believe that radiation from the electric fields might distort molecular aggregations by disturbing the ionic distribution. 16.2.2.11 MISCELLANEOUS SOURCES

A replaceable type of nuclear pollution also occurs in the environment. In this type of pollution some radioactive nuclides replace other nuclides that are present in the same group in periodic table. For instance, radium is present in second group of periodic table along with calcium and strontium. Radium can replace calcium to cause damage to the body tissues. Similarly Sr-90 gets deposited in bones, teeth and tissues in man in place of calcium. 16.3 TYPES OF RADIATION

Radiation is the emission of rays and particles from a source. The source of solar radiation is the sun, and that of ionizing radiation is the group of radioactive elements. There are two basic forms of radiation. They are ionizing radiation and non- ionizing radiation. Ionizing Radiation



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This type of radiation travels in waves (X- rays, Gamma rays) or as particles (alpha,

beta) and carries energy levels so high that it can alter atoms creating electrically charged particles or ions. These ionizing radiations can pass through the protoplasm. It is the chief cause of injury to the living organisms and the damage is proportional to the number of ion-pairs produced in the absorbing matter. Isotopes of elements that emit ionizing radiation are known as radio active isotopes or radionuclides. Non-ionizing radiation

Non – ionizing radiations (heat, light, radio waves, etc.) carry enough energy to excite atoms but not enough to produce ions. Various forms of electromagnetic radiation are non-ionizing in nature. The solar radiations do not have ionizing effect. Self-check Exercise 6

Distinguish between ionizing radiation and non-ionizing radiation


16.4 EFFECTS OF RADIATION

M. Curie discovered radium which is 25,000 times more lethal than arsenic. The potency of radiation toxicity was realized by the death of M. Curie when she died of Leukemia. Radiation poses a wide range of symptoms and syndromes causing several adverse effects which are classified as follows;

1. Effects of ionizing radiations on man 2. Effects of non-ionizing radiations 3. Effects of microwave radiations 4. Effects of radio frequency radiations 5. Effects of fallout radiations 6. Biological effects of radiations 7. Effects of X-rays 8. Effects of Plutonium as carcinogen 9. Radiation effects on plants 10. Effects of unclear radiation on polymers

16.4.1 EFFECTS OF IONIZING RADIATION



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When ionizing radiations penetrate the living tissue, it wrecks havoc on the atoms and molecules in its path. Actually when a water molecule in the cell is irradiated, an electron is knocked out of its orbit. The ejected electron may then attach to a normal water molecule creating instability. Such unstable water molecules (H2O) split into hydrogen ions (H+), hydroxide ions (OH-) and the free radicals – H• and OH•. Radiation also produces a host of several species like H2, H2O–, H2O+, HO2, H3O-, e-, e+ and H2O2. The free radicals are extremely reactive. They react with protein molecules in the cell, setting a chain of event, that can destroy living cells or make them to function abnormally.

Radiation exposure may damage the cell membranes by making it permeable, while the large doses of ionizing radiations can kill quickly or inflict severe damage. Even the lower doses can initiate cancer throughout the body. Radiation also results in abnormal interchange of materials through an imperfect cell membrane causing temporary or permanent injury in the body. Studies of survivors who have received significant doses such as atom bomb survivors, uranium miners and radium watch dial painters etc. showed that damage depends on how the victims were exposed. Experiments have shown that human organs can repair some radiation damage. The sensitivity to radiation damage appears to be directly proportional to the cell’s reproductive capacity and inversely proportional to its degree of differentiation.

The action of ultraviolet (UV) radiations has been extensively studied.

a. In body cells, the protein and nucleic acid are mainly responsible for the absorption of radiation. In the region of 240 nm to 280 nm wavelength, the absorption by nucleic acid is 10 to 20 times greater than that by proteins of the same weight.

b. UV radiations are thought to trigger to distinct immunological effects. One is confined to patches of skin that are actually irradiated, while the other damage is caused to the immune system as a whole.

c. UV radiations cause the blood vessels near the skin’s epidermis to carry more blood causing the skin hot, swollen or sun burns.

d. Serious skin cancers including the basal cell carcinoma, squamous cell carcinoma and melanoma are rapidly climbing the list of human diseases caused by UV radiations.

e. It has been observed that closer a fair-skinned person lives to the equator, the more likely he is to get non-melanoma cancer by UV rays.

f. Curiously enough, melanoma is caused by intermittently exposing the body; high doses of UV radiations often associated with burning sensation and skin aging.

g. UV radiations cause leukemia and breast cancer, although the reasons are obscure. According to an estimate nearly 7000 people die of such cancers in USA every year. Such causes have also increased by 10% in Australia and New Zealand.

h. UV rays can also be absorbed by lens and cornea in the eye leading to photo keratitis and cataracts. Since the radiation is not sensed by the visual receptors of eyes, the damage is done without the individual knowing about its hazards.



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i. These radiations are also associated with DNA breakage, inhibition and alterations of its replications and formation of DNA adduct which has been implicated in premature aging and finally death of the cells.

j. UV radiations also affect drastically the micro-phytoplanktons. Increased UV rays will increase the mortality rate of larvae of zooplanktons in water.

k. Plants absorb strongly the light near 280 nm. So plant proteins are more susceptible to UV injury. In plants 20 to 50% chlorophyll reduction and harmful mutations are seen.

l. It has been reported that UV-B radiations reduce the effectiveness of plant photosynthesis by 70%

m. Increased solar UV radiation cause green house effect by changing the global energy and radiation balance of the atmosphere at the planet-earth.


How does ionizing radiation cause hazards?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.4.2 EFFECTS OF NON IONIZING RADIATION The non- ionizing radiations include infrared, radio waves, microwaves, radar etc. Effects of microwave radiation: Microwaves shorter than 10 cm. are usually absorbed by the skin that can be felt by the heating of the surface tissue. Microwaves between 10 and 30 cm can penetrate the epidermis and fat layer of the skin, while the waves longer than 30 cm can penetrate deep tissues of dermis causing the skin hot. The eyes and other organs that cannot dissipate heat, hence they are most vulnerable to microwave radiations. Russians have set lower exposure limits claiming that microwaves cause skin-burns, fatigue, dizziness, headache, eye- injuries and cataracts. Effects of radio frequency radiations: Non-ionizing radiations of longer wave length cause a common thermal effect. These radiations induce thermal agitation in molecules of the matter to produce heat. A variety of non thermal effects are potentially more dangerous as they pose acute physiological effects. Non-thermal effects may be linked to the electric and magnetic fields associated with the electromagnetic radiation. Effects of electric fields of the radiations are more devastating. It has been observed that electrical potentials of nerve fibers of the central or peripheral nervous system get acutely affected by the electric field component of electromagnetic radiations.

16.4.3 EFFECTS OF FALLOUT RADIATIONS



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The cloud obtained during nuclear explosion contains a mixture of gases, molten

nuclear fuel and some partially melted radioisotopes. As the fireball cools, these materials condense to form the debris which drops down to the earth in the form of radioactive fallout.

The fallout radionuclides either fuse with iron, silica or dust, and from colloidal suspension or insoluble particles or combine with organic compounds to form complexes. The smaller particles of radionuclides form the colloids and adhere tightly to the leaves of plants and produce radiation damage to leaf tissues. These are often ingested by the grazing animals, where these are digested and as a result, enter into the food chain directly at the primary consumers level. The radionuclides which form complexes with organic substances enter the food chain through producer trophic level. In this way, radionuclides manage to enter the body of all living organisms. 16.4.4 BIOLOGICAL EFFECTS OF RADIATION

The extent of damage depends upon various factors such as amount of radiation exposed, its duration, age of the person exposed, and the part of the body affected etc. The hazards of the radiation on human beings may be acute, chronic or genetic damage. The acute radiation damage occurs from relatively large dose of radiation over a short period of time. The acute radiation damages include sudden death, death after some weeks, loss of hairs, widespread ulcers, bleeding from the mouth and gums etc.

The chronic radiation damage occurs from relatively small continuous dose of radiation over a long period of time. The chronic radiation damages include leukaemia, anaemia, cancers of skin and other organs, cataracts, reduction in life span and mutations etc. The genetic radiation damage represents long term effect of radiation and it indicates changes among future generations.

Exposure of the brain and central nervous system to high doses of ionizing radiation causes delirium, convulsions and death within hours or days. The lens of eye is vulnerable to radiation. As its cell die, it becomes opaque, forming cataracts that impair sight.

Internal bleeding and blood vessel damage may show up as red spots on the skin. Unborn children are vulnerable to brain damage or mental retardation, especially if irradiation occurs during formation of the central nervous system in early pregnancy. Damage to bone marrow, the body’s blood factory, is especially harmful; it retards the body’s ability to fight infections and hemorrhaging. Self-check Exercise 8

1. What are the acute effects of radiation? 2. What are the chronic effects of radiation? 3. How are the unborn children affected by radiation?




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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.4.5 EFFECTS OF X-RAYS

Expectant mothers if irradiated during pregnancy are known to give births of malformed babies. X-rays also cause carcinogenicity in women. Experts say that scatter was the biggest problem with X-ray machines. Scatter is the term for leaking and subsequent overdose of radiation. This could cause health problems ranging from impotency, dry eyes, low blood count and throat irritation. 16.4.6 EFFECTS OF PLUTONIUM

Plutonium, a deadly poisonous substance, is bone-seeker. Once deposited in the bone, it can cause serious bone cancer. Insoluble particles of plutonium, if inhaled, can get preferentially lodged in the deep lung, where they can deliver high doses of radiation to the surrounding tissues inducing chronic lung cancer. The damage occurs due to emission of the short range of alpha particles by plutonium. Self-check Exercise 9

What are the effects of plutonium?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 16.4.7 EFFECTS ON PLANTS

Small amounts of radionuclides may lead to an increase in the rate of mutation in the plants also. Trees and shrubs vary in their reactivity and sensitivity towards radioactive substances. This variation is mainly due to the difference in chromosome number and size. It has been reported that plants with less number of chromosomes offer larger ‘target’ of radiation hit than those with excess of small chromosomes. The small chromosomes possess more duplicate genetic information so that when one or two cells are damaged, a number of others can take up their function.



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16.4.8 EFFECTS ON POLYMERS

Polymerization of monomers can be brought about through irradiation. The effect radiation is of great biological and industrial significance and has led to outstanding development in science and technology. Polymers have also been found useful as radiation protecting materials.

16.5 LET US SUM UP In this lesson we have learnt the most challenging type of pollution, radiation. The most devastating effects are caused by ionizing radiation. Nuclear fission of radioactive substances is responsible for these hazards. Atomic bomb explosion, nuclear power reactor, discharge of nuclear wastes etc. are the sources of nuclear fission. We have learnt various types of radiation and their effects. 16.6 LESSON-END ACTIVITIES

· Write down the sources of radiation · List out the sources of ionizing radiation and non- ionizing radiation · Write down the uses of radiation in medical field

16.7 POINTS FOR DISCUSSION We have learnt the types of radiation, sources of radiation and the effects of radiation. You have known the natural sources of radiation and the environmental radiation. However, the man-made sources cause significant damages. Hence, it is imperative to consider the total elimination or minimization of radiation.


· Can you distinguish between ionizing and non- ionizing radiation? · Can you list out sources of radiation? · Can you explain the effects of radiation in detail?

16.9 REFERENCES


11. Miller, Jr., G.T. Environmental Science, Thomson Brroks/Cole, CA, USA, 2004 12. Shama, B.K. Environmental Chemistry



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LESSON 17 – NOISE POLLUTION – BASIC CONCEPTS Contents 17.0 Aims and objectives

17.1. Introduction 17.1.1. Definition

17.2. Sound and sound waves – Basic concepts 17.2.1. Generation of sound 17.2.2. Measurement of sound

17.3. Sources of sound and noise and their types 17.4. Let us sum up 17.5. Lesson-end Activities 17.6. Points for Discussion 17.7. Check your Progress 17.8. References

17.0 AIMS AND OBJECTIVES In this lesson, we are going to learn about noise pollution, of course basic concepts. Next three lessons also deals with the noise pollution – its effects, its measurement and assessment and its control. This lesson deals with the basic concepts of sound waves – wavelength and frequency, speed of the sound etc. In fact, people are generally oblivious of noise pollution and its effects. Therefore, it is essential to learn about noise pollution in detail. Knowledge of noise pollution will help us preventing noise exposure and thus protecting from adverse effects of noise pollution. 17.1 INTRODUCTION

Pollution is an undesirable change in the environment. There are two kinds of pollution in general. One is pollution by mass residuals and another is by energy residuals. Mass residuals are substances that are made of atoms and molecules emitted or discharged or discarded into the environment in the form of atmospheric pollutants or liquid wastes or solid wastes. Energy residuals are the forms of energy released into the environment which will cause undesirable effects to the humans, plants, animals or materials. Heat and noise are energy residuals emitted into the environment.

In fact, the total amount of energy dissipated as sound all over the world is very small when compared to other forms of energy. The ears are so sensitive to perceive such a small amount of energy and sound becomes so important in our lives. Man and other animals communicate using sound energy. When we play music, again we produce sound. Sound is an integral part of our life.

17.1.1 DEFINITION



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People are, in general, oblivious about noise pollution and its effects. What is noise? It is an undesirable sound. But when we say undesirable, sounds that are undesirable to some people may be desirable one to others. Therefore an exact definition is necessary.

Noise is any sound, independent of loudness, that can produce an undesired physiological or psychological effect in an individual, and that may interfere with the social ends of an individual or group. Social ends include all our activities – communication, work, rest, recreation, and sleep (Davis and Cornwell, 1991).

The word "noise" comes from the Latin word nausea meaning "seasickness", or from a derivative (perhaps Latin noxia) of Latin noceō = "I do harm", referring originally to nuisance noise Self-check Exercise 10

Define noise?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 17.2 SOUND AND SOUND WAVES – BASIC CONCEPTS

What is sound? It is a physiological sensation received by ear. It is caused by a vibrating source with a frequency in the range of 20-20000 hertz and is transmitted as a longitudinal pressure wave motion through a material medium such as air (A Dictionary of Science). Sound is a longitudinal wave, in which the particles oscillate to and fro in the same direction of wave propagation. Remember, sound cannot be transmitted through vacuum. The transmission of sound requires a medium – solid, liquid or gas.

Sound waves can result in two ways: 1. Vibration of solid objects – e.g., drums, strings in a musical instrument 2. Separation of fluids as they pass over, around or through holes in solid

objects.

Both vibration of solid objects and separation of fluids cause the surrounding air to undergo compression and rarefaction alternately. That means the molecules of the medium come closer and goes far off alternately just like a spring. Self-check Exercise 11



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1. What is sound? 2. How does sound result?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 17.2.1 GENERATION OF SOUND

Figure 17.1, illustrates two states: state of quiet atmosphere (no sound situation) – A; and a sound wave (compression and rarefaction) – B. When there is no sound the molecules of air are spaced as they are supposed to be under prevailing atmospheric conditions. When sound is generated, the molecules come closer (compressed). The compressed molecules then transfer this energy to the neighboring molecules in the direction of sound propagation and relax (rarefaction). Thus compressed adjacent molecules in turn transfer the energy to neighboring molecules in the direction of propagation and relax. In this way, sound is transmitted in the medium.

If we measured the pressure at the point compression, the pressure would be slightly higher and at the point of rarefaction, the pressure would be slightly lower. However, this increase and decrease are very small even negligible when compared to the atmospheric pressure. Only ears of humans and other animals are capable of perceiving this small change.



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Figure 17.1: Graphic representations of a sound wave. (A) Air at equilibrium, in the absence of a sound wave; (B) compressions and rarefactions that constitute a sound wave; (C) transverse representation of the wave, showing amplitude (A) and wavelength (l).

Suppose, we measured the pressure at any specific point over a period of time, we

may get alternately increased and decreased pressure values. If we plotted these values on a graph, we would get the picture of a wave (provided that the sound generated consisted of single frequency). The peak of the wave is called crest (where compression is noted) while the fall of the wave is called trough (where rarefaction occurs).

The distance between two successive peaks or two successive troughs are called

wavelength. The wavelength of the sound is denoted by the symbol, λ. The height of the peak or trough is determined by the strength (loudness) of the sound, amplitude which is denoted by “A”. Loud sound will exert more pressure than mild sound of the same frequency. Hence, loud sound will have greater amplitude. Self-check Exercise 12

1. What is wavelength?

Figure 1 a – Sinusoidal wave



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2. What are rarefaction and compression? Explain.


The wave pattern is called sinusoidal. The time between successive peaks or successive oscillation of a sound wave is called the period, denoted by the symbol, P. Inverse of period is called frequency. Frequency is the number of crests or troughs arrive at a selected point per unit of time. That is number of compressions or rarefactions arrive at a selected point per unit of time.

The speed of the sound is the speed at which the sound wave is propagated – the distance a compression or rarefaction is transmitted per unit of time. The speed of the sound is denoted by the symbol, c. Wavelength and the frequency can be related as follows:

17.2.2 MEASUREMENT OF SOUND

The pressure of the atmosphere without any sound will be taken as reference point as “zero” pressure level. Amplitude of a wave is measured from “zero” pressure line. Amplitude can be measured as the height of the crest or as the depth of the trough. When we draw a graph, from “zero” pressure line, at the height of amplitude will have positive pressure value while depth will have negative pressure value. As a result, when we take the average pressure of the wave over a time period, we will get zero. This is misleading! and not acceptable. Therefore, scientists have decided to calculate root mean square of pressure: calculating mean value of each pressure observation and then taking the square root. The equation for root mean square over the period of average time is as follows:

1 f P =

c

f λ =



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Where, p = individual pressure observations

T = time period of measurement t = instantaneous time in which a p value was observed

As already mentioned, the sound pressure values are so small when compared to the atmospheric pressure. Actually the sound pressure is the difference between total atmospheric pressure and the pressure exerted by atmosphere alone. The atmospheric pressure is usually around 100 kPa and above while; the sound pressure is in the order of micro pascals (µPa) - such a vast difference in the magnitude of pressure. Sound pressure = total atmospheric pressure – barometric pressure Self-check Exercise 13

Why do we express the sound pressure in terms of prms? Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Sound Power: “work” is the product of the magnitude of displacement of a body and the component of force in the direction of the displacement. The sound waves while traveling transmit energy in the direction of propagation. Here, energy is displaced. The rate at which this work is done id called sound power (W). Sound Intensity: it is the time-weighted average sound power per unit area normal to the direction of propagation of the sound wave. It is denoted by the symbol, I. Intensity and power are related as follows:

½

p rms = 1

T p2 =

T

0 p2 (t) dt

½

p = time weighted average pressure

I = W

A



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Where, I = sound intensity W = sound power A = area perpendicular to the direction of wave propagation The intensity of the sound and sound pressure are related as follows:

Where, I = sound intensity Prms = root means square of sound pressure ρ = density of the medium, kg m-3 c = speed of the sound in medium, m s-1

The speed of the sound depends on the medium through which the sound waves are propagated. The speed of the sound is proportional to the square root of the ratio of the elastic modulus of the medium and its density. In addition, the environmental conditions affect the physical properties of the medium as well as the speed of the sound. The temperature and humidity are the two important atmospheric conditions that affect the speed of the sound. The speed of the sound in air at 20 °C and at 1 atmospheric pressure approximately equals to 1,238.3 km/h. It is 5,335.1 km/h in water and 21,446 km/h in steel at the same temperature and pressure.

The speed of sound is also slightly sensitive (a second order effect) to the sound amplitude, which means that there are nonlinear propagation effects, such as the production of harmonics and mixed tones not present in the original sound. The speed of the sound in air is determined form the following equation: Where, c = speed of the sound, m s-1 T = absolute temperature in degrees Kelvin (K) Self-check Exercise 14

What is sound intensity?


(prms)2

ρc I =

c = 20.05 T



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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Levels and Decibles: the sound pressure is measured in is µ Pa (micropascal) or other units that are inter-convertible. The sound pressure that a normal healthy human ear can perceive is 0.00002 Pa (= 20 µ Pa). The sound pressure produced by a rocket during liftoff is about 200 Pa. The range of sound pressure perceived by human ear is from 20 µ Pa to 200 Pa which is exponentially large. It is something like the distance in km between two places and distance in light years between two stars. Such an exponentially wide range of sound pressures is difficult to express and for comparison studies. Therefore, scientists decided use a scale based on the logarithm of the ratios of the measured quantities. Measurements on this scale are called levels. The unit for these types of expression is the bel named after Alexander Graham Bell. The bel is expressed as follows: Where, L’ = level, bels Q = measured quantity Q0 = reference quantity log = logarithm to the base 10 The unit bel is again a larger unit; hence, it is divided into ten subunits called decibels (dB). However, the dB is not a unit as such, but it represents logarithmic ratios of two measured quantities. The level in decibel is computed as follows:

Sound Pressure Level: sound pressure level is computed similarly as follows:

The squaring can be extracted and the equation becomes:

Q L’ = log

Q0

Q0

Q 10 log L =

(prms)02

(prms)2

10 log Lp =

(prms)0

(prms)

20 log Lp =



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Where, Lp = sound pressure level (SPL), dB prms = observed pressure in µ Pa (prms)0 = reference pressure = 20 µ Pa Self-check Exercise 15

1. Define Sound Pressure Level 2. What is the reference sound pressure?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 17.3 SOURCES OF SOUND AND NOISE AND THEIR TYPES

Sound is generated by a wide variety of sources so also noise. The sources include child’s cry, human speech and song, chirping sounds from birds, sounds from animals like trumpeting sound of an elephant, sounds generated from man-made machines. Thus the sources of sound are of two kinds: natural and man-made. Here man-made does not include human speech and his song. However, his musical instruments and audio systems when played in high sound intensity they become noise. Sounds may be classified as: 1. Steady-state or continuous sound (or noise) 2. Intermittent sound (or noise) 3. Impulse or impact noise Steady-state or continuous noise: it is an uninterrupted sound level that varies les than 5 dB during the period of observation. Noise from household fan is an example of this type of sound. The fan produces sound continuously without noticeable variation. Engine noise by an automobile at the top gear is another example. Intermittent noise: it is a continuous noise persists for more than one second and then interrupted for more than one second. The drilling machine operated by an electrician is a best example for intermittent noise. Impulse noise: it is a noise which changes 40 dB or more within 0.5 second with duration of less than one second. The noise from a firing weapon is an example for this type of noise.



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What are the types of sound? Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 17.4 LET US SUM UP In this lesson, we have learnt some of the basic concepts of sound. We learnt about sound waves, and their characteristics. We have also learnt that sound pressure is the cause for the loudness. When we measure the pressure and get the average value, it becomes zero, hence, root mean square of pressure calculation is suggested. We also learnt the threshold sound pressure value and that this value is taken as the reference value in calculating the sound pressure level. 17.5 LESSON-END ACTIVITIES

· Take a sheet of paper and write down the sources of sound you come across in your daily life.

· Write the sounds that you feel as unwanted · List out the sounds you come across and categorize them (as steady-state,

intermittent, impulse)

17.6 POINTS FOR DISCUSSION In this lesson, you have been introduced to noise pollution. You have learnt the concepts of sound and its propagation. We learnt the sound pressure measurement and their expression. As the range of sound pressure is exponentially high, the sound is expressed as logarithmic ratios of observed value and the reference value. We have also learnt the types of sound.


· Can you relate sound intensity with sound pressure? · Have you understood the reason for sound being expressed in levels? · Can you identify the type of a sound?

17.8 REFERENCES



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1. Davis, M.L. and Cornwell, D.A. Introduction to Environmental Engineering, McGraw Hill, Inc., New York, 1991

2. Singal, S.P. Noise pollution and Control, Narosa Publishing House, New Delhi, 2000.

3. Pandey, V. Noise pollution 4. Kudesia, V.P. and Tiwari, T.N. Noise pollution and its control



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LESSON 18 – EFFECTS OF NOISE POLLUTION Contents 3.0 Aims and objectives

3.1. Effects of noise on people 3.2. Anatomy of ear and hearing mechanism 3.3. Hearing impairment

3.3.1. Normal hearing 3.3.2. Human response and loudness 3.3.3. Measurement of hearing ability


18.0 AIMS AND OBJECTIVES In this lesson we are going to learn the effects of noise pollution. Most of the people are unaware of the existence of noise pollution and its adverse effects. Once, hearing damage has occurred permanently, it is irreversible. Therefore, it is essential to know the harmful effects of noise. You will be learning the types of effects and the magnitude of the effects. 18.1 EFFECTS OF NOISE ON PEOPLE

Noise causes many problems to human beings when exposed for a considerably long periods of time, including effects on hearing, on health, on behavior, and on social ends such as communication, work, and sleep. The effects largely depend upon the magnitude of sound pressure level and duration of exposure. Examples of sound pressure and sound pressure levels and associated effects are presented in table 18.1. We can categorize these into two kinds:

1. Auditory effects 2. Psychological/sociological effects

Auditory effects: they include hearing loss and speech interference. Hearing loss may occur temporarily or permanently. In fact hearing loss may start as a temporary one but may end us as a permanent one when the victim is subjected to prolonged exposure. Psychological / sociological effects: they include annoyance, sleep interference, effects of performance and acoustic privacy. Table 18.1 - Examples of sound pressure and sound pressure levels Source: en.wikipedia.org



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Source of sound RMS sound

pressure sound pressure

level

Pa dB re 20 µPa

Immediate soft tissue damage 50000 approx. 185

Rocket launch equipment acoustic tests approx. 165

Threshold of pain 100 134

Hearing damage during short-term effect 20 approx. 120

Jet engine, 100 m distant 6–200 110–140

Jack hammer, 1 m distant / discotheque 2 approx. 100

Hearing damage from long-term exposure 0.6 approx. 85

Traffic noise on major road, 10 m distant 0.2–0.6 80–90

Moving passenger car, 10 m distant 0.02–0.2 60–80

TV set -- typical home level, 1 m distant 0.02 > 60

Normal talking, 1 m distant 0.002–0.02 40–60

Very calm room 0.0002–0.0006 20–30

Quiet rustling leaves, calm human breathing 0.00006 10

Auditory threshold at 2 kHz -- undamaged human ears

0.00002 0


What are the two kinds of effects of noise? Explain. What is the approximate noise level by a TV?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. For understanding the auditory effects, we should know hearing mechanism of human ear. Let us turn our attention towards the hearing mechanism: 18.2. ANOTOMY OF EAR AND HEARING MECHANISM

Ear is an organ having two functions: hearing and balancing of the body. In this section we shall limit our learning to the hearing function of the ear. Ear, nose and throat



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are structurally, functionally and neurologically interrelated. Ear consists of three parts. They are the outer ear, the middle ear and the inner ear. Both outer and middle ear convert the sound pressure into vibration. The outer ear funnels the sound waves into the ear drum. In addition, the outer and the middle ear protect the inner ear from debris and other objects. Anatomy of ear is presented in figure 18.1.

Middle ear is a small chamber consisting of three ossicular bones that amplify the sound. The sound is amplified approximately 22 times by the middle ear. The three bones, malleus (or hammer), incus (or anvil), and stapes (or stirrup) are linked as a chain one after the other. The malleus is located next to the tympanic membrane (ear drum). It is linked to incus and incus to stapes. When the sound waves reach the ear drum, the ear drum vibrates and this vibration is immediately transmitted to the ossicular chain of bones. The three bones in turn oscillate and transmit into the inner ear. Stapes is embedded in the oval window and it transmits the energy by its movement back and forth thorough the oval window into the inner ear.

Figure 18.1 Anatomy of ear

Amplification of the sound occurs by two mechanisms. First, the large surface area of the drum as compared to the small surface area of the base of the stapes results in a hydraulic effect. The ear drum has about 25 times as much surface area as the oval window. All of the sound pressure collected on the ear drum is transmitted through the ossicular chain and is concentrated on the much smaller area of the oval window. This produces a significant increase in pressure.

Secondly, the ossicular chain of bones is arranged in such a way that they act as a series of levers. The long arms are nearest the eardrum, and the shorter arms are toward the oval window. A small pressure on the long arm of the lever produces a much stronger pressure on the shorter arm. Thus, the ossicular chain amplifies the sound pressure.



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Both the auditory receptors and balance receptors are located in the inner ear. Cochlea houses the auditory receptors. Cochlea is a snail-shaped bone coiled two and a half times around its own axis. The cochlea consists of three compartments: the scala vestibule; the scala media; and the scala tympani.

The scala vestibule and the scala tynpani are connected at the apex of cochlea and they are filled with a fluid called perilymph. The scala media floats in the perilymph. The scala media contains a different fluid, endolymph. The hearing organ, organ of corti is located in the scala media and is surrounded by the endolymph. The scala media is triangular in shape and having the length of about 34 mm.

In organ of corti, cells are grown up from the basilar membrane. These cells have a tuft of hair at one end and are attached to the hearing nerve at the other end. A gelatinous membrane called tectoral membrane extends over the hair cells and is attached to the limbus spiralis. By this way the hair cells are embedded in the tectoral membrane.

Vibration reaches the oval window causes the fluids of the three scala to develop a wave- like motion. This causes the basilar membrane and the tectoral membrane to move in opposite direction. Movement of these membranes causes a shearing motion on hair cells. The dragging of hair cells sets up electrical impulses in the auditory nerves that are transmitted to the brain.

The nerve endings near the oval window are sensitive to high frequencies while those near the apex of cochlea are sensitive to low frequencies. Self-check Exercise 18

How much is the amplification of sound by ear? What are the names of three ossicular bones? Where is auditory reception mechanism located?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 18.3 HEARING IMPAIRMENT

The outer and middle ear are rarely damaged by noise. The eardrum may get ruptured from exposure to intense explosive noise. Injury to hair cells leads to neural damage which results in hearing loss. There are two theories explaining the injury of hair cells. The first theory states that the excessive shearing stress due to intense noise damages the hair cells mechanically. The second is that intense noise forces the hair cells to undergo



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increased metabolic activity which overdrives them. This will result in metabolic failure and then death of hair cells.

How can we assess the magnitude of hearing loss? There is no direct method to observe the damage in the organ of corti. Injury can be inferred from losses in hearing threshold limit (HTL).

Hearing loss also occurs due to ageing of a person, drugs and blows on head. The hearing loss occurring due to ageing is called presbycusis. We shall be discussing the noise- induced hearing loss and not presbycusis, which is out of the scope of this lesson. Noise- induced hearing loss may either be temporary or permanent. Before proceeding further, let us learn what hearing threshold limit and threshold shift are. Self-check Exercise 19

What is Presbycusis?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 18.3.1 NORMAL HEARING

In order to understand the hearing impairment, we should know the normal hearing with reference to frequency range and sensitivity. The ear of the young, audiometrically healthy adult male is capable of perceiving the sound waves in the frequency range of 20 to 16,000 Hz. The women and young children are capable of perceiving the sounds with frequencies up to 20,000 Hz. The speech zone lies between the frequency range of 500 and 2,000 Hz. Human ear is most sensitive to the frequencies in the range of 2,000 to 5,000 Hz. The smallest perceptible sound in this frequency range is 20 µ Pa. A sound pressure of 20 µ Pa at 1,000 Hz is corresponding to a1.0 nm displacement of air molecules. Self-check Exercise 20

1. What is the frequency range perceived by:

a) Young adult b) Women and young children

2. What is the frequency range to which human ear is most sensitive?




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……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

18.3.2 HUMAN RESPONSE AND LOUDNESS

Two pure tones of different frequencies will be heard as different loudness levels in spite of having the same sound pressure level. Hence, loudness level is a psychoacoustic quantity.

Fletcher and Munson carried out several experiments to determine the relationship between frequency and loudness in 1933. Their results were plotted as sound pressure level in dB versus the test tone frequency. The curves of their results are called the Fletcher-Munson or equal loudness contours. 1000 Hz was used as the reference frequency. The curves are labeled in phons, which are the sound pressure levels of the 1,000 Hz pure tone in dB. The lowest phon represents the threshold of hearing.



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Figure 18.2 Fletcher-Munson equal loudness contours

18.3.3 MEASUREMENT OF HEARING ABILITY Audiometry: hearing tests are conducted using a device called audiometer and the tests are called audiometry. It consists of pure tones with variable sound pressure level output into a pair of earphones. The test results are used to prepare a graph called audiogram. Hearing threshold level (HTL) scale is the adjusted loudness to “0” dB level for each pure tone. As mentioned above, the loudness will vary to different frequency and hence the threshold level. The threshold level for a particular frequency is considered as “0” dB for that tone. Hearing impairment: For a normal, young and audiometrically healthy person, the HTL should be “0” dB for all individual tones. When a person looses the hearing ability either due to ageing, other factors, or noise, there will be a shift in the HTL from “0” dB to higher values. This is called threshold shift. If this shift is a temporary one, then it is called temporary threshold shift (TTS); if it is a permanent one, then it is called permanent threshold shift (PTS). When this shift is due to noise then they are called noise induced temporary threshold shift (NITTS) and noise induced permanent threshold shift (NIPTS) respectively. Audiograms of a person with normal hearing and a person with hearing impairment are shown in figure 18.3. There are several factors result in threshold shift. They are:

1. Sound level: when sound level exceeds 60 to 80 dBA, the person may experience TTS

2. Frequency distribution of the sound: if the loud sounds are in the range of speech frequencies, then the TTS will be severe.

3. Duration of sound: the duration of the sound also determines the amount of threshold shift



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4. Temporal distribution of sound exposure: the number of times and duration in each time the person is exposed determine the extent of threshold shift.

5. Individual differences: individuals differ in their response and hence there will be variation in threshold shift among individuals.

6. Type of sound: type of sound such as steady state also determine the extent of threshold shift

Temporary threshold shift (TTS): it is mostly accompanied by a ringing in the ear, muffling of sound or discomfort of the ears. TTS occurs during first two hours of exposure and recovery to the baseline HTL begins within 1 or 2 hours after exposure. Complete recovery may be attained within 16 to 24 hours after exposure. Permanent threshold shift (PTS): if noise levels did not produce TTS after 2 to 8 hours of exposure they will not produce PTS when continued beyond this duration. If produced, that will lead to PTS when the person is exposed to such noise levels on a regular basis for considerable period of time. The audiogram of TTS resembles that of PTS.

There will be a sharp localized dip in the HTL curve at the frequencies between 3,000 and 6,000 Hz when a noise- induced hearing loss occurs. Initially this dip is observed at 4,000 Hz. It is called high frequency notch. Later, the high frequency notch will broaden and spread in both directions. The victim may not realize until the dip occurs more than 25 dB in the speech frequencies between 500 and 2,000 Hz. As the onset and progress of noise- induced hearing loss is slow and subtle, the victim will not sense and realize it until a considerable amount of loss has occurred. Acoustic trauma: explosive sounds can rupture the tympanic membrane and/or dislocated the ossicular chain that will result in permanent hearing loss and this hearing loss is called acoustic trauma. The person might have been exposed for a very short duration. Cardiovascular effects: noise is known to cause cardiovascular effects. The high noise levels are proven to increase the blood pressure levels and stress levels. High noise levels cause vasoconstriction which will lead to coronary artery diseases. Figure 18.3 Audiograms of a person with normal hearing and

a person with hearing impairment



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Speech interference: noise interferes with the communication. Even though some noises are not intense enough to cause auditory effects, they can interfere with speech communication. Noises interfere by masking our speech and the hearer may not get the complete message spoken by the speaker. This masking effect is a function of the distance between the speaker and the listener and the frequency components of the spoken words. Annoyance: some sounds are unpleasant and thereby they affect our activities. It is a psychological response to some sounds especially noisy sounds. When a sound resembles already disliked sound, it will be annoying. A visible sound source will be more annoying than that is invisible. A sound mindlessly inflicted for a long duration will be more annoying than that lasts for short duration. The degree of annoyance will vary from person to person. Sleep interference: people fail to fall into sleep when exposed to loud, strange, annoying and/or frightening sounds. But, a person who has been exposed to such sounds and accustomed will also find difficulty in sleeping when left in soundless environment. Effect on animals: noise and other loud sounds can have a detrimental effect on animals by causing stress, increasing risk of mortality by changing the delicate balance in predator/prey detection and avoidance, and by interfering with their use of sounds in communication especially in relation to reproduction and in navigation. Very significantly, acoustic overexposure can lead to temporary or permanent loss of hearing.

The most significant impact of noise to animal life is the systematic reduction of usable habitat, which in the case of endangered species may be an important part of the path to extinction. Perhaps the most sensational damage caused by noise pollution is the



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death of certain species of beached whales, brought on by the extremely loud (up to 200 decibels) sound of military sonar. Amazing fact about one’s own voice: A person hears his/her own voice while speaking differently than heard by others. Or the person hears his/her recorded voice he/she may be surprised to learn that it sounds differently what he/she perceives while speaking. When a person speaks the sound waves are transmitted to others via one route only – air. But they are transmitted via two routes to the speaker: one via air and another via the jaw bone. Jaw bone vibrates when the person speaks and this vibration is transmitted to the ear. The vibration transmitted via jaw bone sounds differently than transmitted through air. This makes the difference in perception of the speaker for his/her own voice. Self-check Exercise 21

1. What is HTL? 2. What is high frequency notch? 3. What is acoustic trauma? Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 18.4 LET US SUM UP In this lesson, we have learnt the effects of noise pollution. We have learnt the temporary hearing loss as well as permanent hearing loss. We also studied the other effects of noise on people. 18.5 LESSON-END ACTIVITIES

· Take a sheet of paper and write down what you have understood from Fletcher and Munson equal loudness contours

· Write down how you felt when you heard a loud noise (for example hearing the air horn sound when standing very close to a bus or lorry, cracker sound etc.)



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18.6 POINTS FOR DISCUSSION By now you are aware of the auditory and non-auditory effects of noise pollution. You must take a decision not to be part of any activity that generates high noise. You know that initially, the hearing loss is not realized by the victim. The victim will come to know only after hearing loss has occurred considerably. Noise also affect in many ways. It may cause cardiovascular effects. Other effects include, annoyance, speech interference, sleep interference etc. 18.7 CHECK YOUR PROGRESS

· Are you able to describe that loudness varies according to the frequency of the sound.

· Can you explain “high frequency notch”?

18.8 REFERENCES 1. Davis, M.L. and Cornwell, D.A. Introduction to Environmental Engineering,

McGraw Hill, Inc., New York, 1991 2. Singal, S.P. Noise pollution and Control, Narosa Publishing House, New Delhi,

2000 3. Pandey, V. Noise pollution 4. Kudesia, V.P. and Tiwari, T.N. Noise pollution and its control 5. www.en.wikipedia.com




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LESSON 19 - ASSESSMENT AND MEASUREMENT OF NOISE Contents


19.1. Measurement of sound and sound pressure level 19.1.1. Sound pressure levels 19.1.2. Characterization of noise 19.1.3. Sound Level Meter

19.2. Assessment of Noise 19.3. Ambient Noise Standards 19.4. Let us sum up 19.5. Lesson-end Activities 19.6. Points for Discussion 19.7. Check your Progress 19.8. References

19.0 AIMS AND OBJECTIVES In this lesson we are going to learn the methods of measuring the sound and assessing the extent of noise. There are devices available

19.1 MEASUREMENT OF SOUND AND SOUND PRESSURE LEVEL

As mentioned in section of 17.2.2 of lesson 17, root mean square of sound pressure is calculated to express the sound pressure of a source.

The equation for root mean square over the period of average time is as follows:

Where, p = individual pressure observations

T = time period of measurement t = instantaneous time in which a p value was observed Self-check Exercise 22

What is prms? Explain.


½

p rms = 1

T p2 =

T

0 p2 (t) dt

½

p = time weighted average pressure



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……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

19.1.1 SOUND PRESSURE LEVELS Sound pressure level is a logarithmic ratio of the observed sound pressure of a source and a refrence sound pressure (20 µPa). Zero deciblel refers to the threshold of hearing. When we take the ratio of 20 µPa to the reference sound pressure, 20 µPa, the ratio will be 1 and the logarithmic value of 1 is zero, hence, 0 dB. While measuring sound pressure level, the calibration is done for 1 pascal as equal to 94 dB.

When making measurements in air (and other gases), SPL is almost always expressed in decibels compared to a reference sound pressure of 20 µPa, which is usually considered the threshold of human hearing (roughly the sound of a mosquito flying 3 m away). Thus, most measurements of audio equipment will be made relative to this level. However, in other media, such as underwater, a reference level of 1 µPa is more often used. These references are defined in ANSI S1.1-1994. In general, it is necessary to know the reference level when comparing measurements of SPL. The unit dB (SPL) is often abbreviated to just "dB", which gives some the erroneous notion that a dB is an absolute unit by itself.

The reference pressure is set by International agreement to be 20 micropascals for

airborne sound. It follows that the decibel is in a sense not a unit, it is simply a dimensionless ratio—in this case the ratio of two pressures.

19.1.2 CHARACTERIZATION OF NOISE

We are interested in noise and its measurement due to its effect on people. Therefore we must take the human response to sound into account. Sound pressure level as such cannot be taken to indicate loudness of a sound since human ear has varied response for sounds with different frequencies in spite of having the same sound pressure level.

When weighted in this way the measurement is referred to as a sound level. The International Electrotechnical Commission (IEC) has defined several weighting schemes. A-weighting attempts to match the response of the human ear to pure tones, while C-weighting is used to measure peak sound levels.

The three weighting networks, A – Weighting network, B – weighting network and C – weighting network are electronic filtering mechanisms built into the measuring device to attenuate certain frequencies. They permit the sound level meter to respond more to some frequencies than to others in such a way mimicking human ear. Low frequencies are filtered quite severely by the A network, moderately by B network and hardly by C network. Due to this variation, the noise measured using C network will have much higher value than using the A network. However, the A network measure the sound pressure level



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more or less as perceived by human ear. The weighting networks are illustrated in figure 19.1.


1. State the reasons for development of weighting networks in measurement of

sound pressure level. 2. Define dBA

Note: Please do not proceed unless you write answers for the above two in the space given below1. ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

Figure 19.1 Weighting networks

As three weighting networks are available, it is necessary to mention the network with which the sound pressure level is measured. Thus, the sound pressure level values are labelled as dB(A) - or dBA, dB(B) - or dBB and dB(C) - or dBC to represent the network in which the measurements are made.

Sound Level Meters (SLM) measures the sound pressure levels in any one of the weighting network. For measurement of accompanying frequency, we should use a sound analyzer. 19.1.3 SOUND LEVEL METER



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Sound level meters measure sound pressure level and are commonly used for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise. However, the reading given by a sound level meter does not correlate well to human-perceived loudness; for this a loudness meter is needed. The current International standard for sound level meter performance is IEC 61672:2003 and this mandates the inclusion of an A-frequency-weighting filter and also describes other frequency weightings of C and Z (zero) frequency weightings. The older B and D frequency-weightings are now obsolete and are no longer described in the standard.

In almost all countries, the use of A-frequency-weighting is mandated to be used for

the protection of workers against noise- induced deafness. The A-frequency curve was based on the historical equal- loudness contours and while arguably A-frequency-weighting is no longer the ideal frequency weighting on purely scientific grounds, it is nonetheless the legally required standard for almost all such measurements and has the huge practical advantage that old data can be compared with new measurements. It is for these reasons that A-frequency-weighting is the only weighting mandated by the international standard, the frequency weightings 'C' and 'Z' being optional fitments.

Originally, the A-frequency-weighting was only meant for quiet sounds in the

region of 40 dB SPL, but is now mandated for all levels. C-frequency-weighting however is still used in the measurement of the peak value of a noise in some legislation, but B-frequency-weighting - a half way house between 'A' and 'C' has almost no practical use. D-frequency-weighting was designed for use in measuring aircraft noise, when non-bypass jets were being measured and after the demise of Concord, these are all military types. For all civil aircraft noise measurements A-frequency-weighting is used as is mandated by the ISO and ICOA standards.

The standard sound level meter is more correctly called an exponentially

averaging sound level meter as the AC signal from the microphone is converted to DC by a root-mean-square (RMS) circuit and thus it must have a time-constant of integration; today referred to as time-weighting. Three of these time-weightings have been standardised, 'S' (1s) originally called Slow, 'F' (125 ms) originally called Fast and 'I' (35 ms) originally called Impulse. Their names were changed in the 198's to be the same in any language. I-time-weighting is no longer in the body of the standard because it has little real correlation with the impulsive character of noise events.

The output of the RMS circuit is linear in voltage and is passed through a

logarithmic circuit to give readout linear in decibels (dB). This is 20 times the base 10 logarithm of the ratio of a given root-mean-square sound pressure to the reference sound pressure. Root-mean-square sound pressure being obtained with a standard frequency weighting and standard time weighting.

Note: in acoustics all 'levels' are in decibels.

When measuring the sound created by an object, it is important to measure the distance from the object as well, since the SPL decreases in distance from a point source with 1/r (and not with 1/r2, like sound intensity). It often varies in direction from the source, as well, so many measurements may be necessary, depending on the situation.



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The distance law for the sound pressure p is inverse-proportional to the distance r of a punctual sound source.

A sound level meter is shown in figure 19.2. (Source: www.en.wikipedia.com)

Figure 19.2 An integrating-averaging sound level meter complying with IEC 61672 :

2003 19.2 ASSESSMENT OF NOISE

Sound level measurement can be made using sound level meters. These meters give instantaneous sound pressure levels in decibels in all the three weighted networks (dBA, dBB and dBC). Since the individual values vary over time and reporting all the values being meaningless, equivalent noise level, Leq can be computed and reported as a single value. In addition, noise level that is exceeded certain percent of the time LN can also be calculated. The N may be 10% of time, 40% of the time, 50% of the time, and 90% and so on. They are reported as L10, L40, L50, and L90 respectively. Minimum and maximum noise levels can also be reported (Lmin and Lmax).

Both Lmin and Lmax are minimum and maximum noise levels of a set of observations. LN is a statistical measure indicating how frequently a particular sound level is exceeded. If for example, L50 = 74 dBA that means 74 dBA was exceeded 50 percent of the time during observation. LN can be easily calculated cumulative distribution curve (ogive).




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Leq is the equivalent noise level and it can be applied to any fluctuating noise level. It is equivalent to a noise level that releases the same amount of energy as the fluctuating level over the same period of the time. It is expressed as follows: Where, t = the time over which Leq is determined L(t) = the time varying noise level in dBA

Since, there is no well-defined relationship between L(t) and time, a series discrete observations of L(t) can be made and Leq can be calculated as follows:

Where, n = the total number of observations taken Li = the noise level in dBA of the i-th observation ti = fraction of total sample time Self-check Exercise 24

What is Leq? Explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Noise assessment: when any kind of project (industry, roadway, railway, dam construction etc.) is proposed, it is mandatory to prepare a detailed comprehensive environmental impact assessment report. Noise impact assessment is one of the components of the report. The impact is assessed for 2 phases:

1. construction phase and 2. operational phase

Leq = 10 log 10L(t)/10 dt t 0

1

t

Leq = 10 log 10Li(t)/10 ti

i=n i=1

1 t



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During construction phase, people near construction site though they are unrelated to construction activities will be affected. They are:

1. area residents 2. office workers 3. school children 4. hospital residents and staff 5. etc.

While determining the noise impact during construction phase, the following factors are

to be considered: 1. distance from the noise source 2. presence and size of barriers between the source and the impacted population; the

barriers include both natural and man-made 3. weather conditions that potentially absorb, reflect or focus sound; they are wind

speed and direction, and temperature inversions 4. scale and intensity of construction phase such as excavation, erection and finishing

During operational phase, various instruments and machines will generate noise in

industries while vehicles will generate noise in highways. Whatever being the phase, six steps are suggested to assess the noise impact:

1. Identification of levels of noise emissions and impact concerns related to the construction and operation phase

2. Description of the environmental setting in terms of existing noise levels and noise sources, along with land-use information and unique receptros in the project area

3. Procurement of relevant laws, regulations, or criteria related to noise levels, land-use compatibility and noise emission standards

4. Conduction of impact prediction activities including the use of a. Simple noise-attenuation models, b. Simple noise-source-specific models, c. Comprehensive mathematical models and/or d. Qualitative-prediction techniques based on examination of case

studies and exercise of professional judgment 5. Use of pertinent information from step 3, along with professional judgment

and public input, to assess the significance of anticipated beneficial and detrimental impacts and

6. Identification, development, and incorporation of appropriate mitigation measures for the adverse impacts

Of these, the impact prediction step will tell us the extent of noise that is likely to be

generated. The predicted levels will be compared with the standards and recommendations and suggestions are made. Details of models can be obtained from standard text books.

19.3 AMBIENT NOISE STANDARDS



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In India, the Noise Pollution (Regulation and Control) Rules, 2000 have been framed under the Environment (Protection) Act, 1986. These are a set of guidelines for regulation and control of noise. The Ambient levels of noise for different areas/zones specified in the rules are indicated in table 19.1.

Table 19.1 Ambient Noise Standards

Limits in dBA Area Code

Category of Area / Zone Daytime (6 am to 9 pm) Nighttime (9 pm to 6 am)

A Industrial Area 75 70 B Commercial Area 65 55 C Residential Area 55 45 D Silence zone 50 40

Source: Environment (Protection) Act, 1986 as amended in 2002. 19. 4 LET US SUM UP In this lesson we have learnt the weighting networks available and the A network is the standard network in noise measurement in relation to human response. We also learnt the instrument used in sound levels, Sound Level Meter and its function. We learnt the methods of expressing the observed. We studied the assessment of noise for any proposed project.

19. 5 LESSON-END ACTIVITIES

· Take a sheet of paper and write about weighting networks · Practice the equation for Leq computation · Practice the computation methods of Lmin, L10, L50, and Lmax

19. POINTS FOR DISCUSSION You have learnt different weighting networking available for expressing the noise levels. You also learnt the computation of Leq and Lmin, L10, L50, and Lmax. By now you have understood that the dB is not a unit of noise. You have also learnt the assessment methods of noise of any proposed project.

19. CHECK YOUR PROGRESS

1. Can you explain the differences among the weighting networks? 2. Can you compute Leq and Lmin, L10, L50, and Lmax? 3. Can you state the standard noise level for any given area without referring to the

table? 19. REFERENCES



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1. Davis, M.L. and Cornwell, D.A. Introduction to Environmental Engineering,

McGraw Hill, Inc., New York, 1991 2. Singal, S.P. Noise pollution and control, Narosa Publishing House, New Delhi,

2000. 3. Pandey, V. Noise pollution 4. Kudesia, V.P. and Tiwari, T.N. Noise pollution and its control 5. www.en.wikipedia.com




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LESSON 20 - NOISE CONTROL – BASIC PRINCIPLES Contents 20.0 Aims and objectives

20.1. Approaches to control of noise 20.1.1. Noise control at source 20.1.2. Noise control in transmission path 20.1.3. Noise control at receiver

20.2. Environmental Noise mitigation 20.2.1. Roadway noise control 20.2.2. Aircraft noise control 20.2.3. Noise control by architectural design


20.0 AIMS AND OBJECTIVES We have learnt so far, the noise, its sources, its effects and its measurement and assessment methods. We understood that noise can cause irreversible hearing loss to humans when exposed. Hence, it is imperative to control noise. In this lesson we are going to learn the control methods available and suggested. 20.1 APPROACHES TO CONTROL OF NOISE

Noise pollution control can be approached by any or all of the following three methods:

1. control at source 2. control along the path 3. control at receiver

Noise control at source: noise can be controlled at source by the following approaches:

1. reducing impact forces 2. reducing speed and pressures 3. reducing frictional resistance 4. reducing radiating area 5. reducing noise leakage 6. isolating and damping the vibration elements 7. providing silencers

Noise control along the path: along the path noise can be controlled in the following ways:



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1. absorption of sound along the path 2. deflection of sound to some other direction by placing reflecting barrier 3. containing the sound by placing the source inside a sound- insulating box or

enclosure Noise control at the receiver: when all the above fails, the receiver has to be protected by covering his/her ears:

1. using molded and pliable earplugs 2. using cup-type protectors 3. using helmets

Such devices are capable of reducing noise by 15 – 35 dB. Self-check Exercise 25

What are the three approaches to control noise pollution?


20.1.1 NOISE CONTROL AT SOURCE Noise can be controlled any of the one or the combination of the prescribed methods. Noise can be controlled by seven methods at sources. Again any one of the method or a suitable combination can be chosen. 1. Reduction of impact forces: many machines and items of equipment are designed

with parts that strike forcefully against other parts, producing noise. Several steps can be taken to reduce noise from impact forces. By suitably modifying the design of these parts / machines we can considerably reduce noise. The following methods are suggested:

i. Reduce the weight, size or height of fall of the impacting mass ii. Cushion the impact by inserting a layer of shock-absorbing material between the

impacting surfaces. iii. Whenever practical, one of the impact heads or surfaces should be made of non-

metallic material to reduce resonance (ringing) of the heads. iv. Substitute the application of a small impact force over a long time period for a

large force over a short period to achieve the same result. v. Smooth out acceleration of moving parts by applying accelerating forces

gradually. Avoid high, jerky acceleration of jerky motion.



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vi. Minimize overshoot, backlash, and loose play in cams, followers, gears, linkages and other parts. This can be achieved by reducing the operational speed of the machine, better adjustment, or by using spring- loaded restraints or guides.

2. Reduction of speed and pressures: reducing the speed of rotating and moving parts in machines and mechanical systems results in smoother operation and lower noise output. Similarly, reducing pressure and flow velocities in air, gas and liquid circulation systems lessens turbulence, resulting in decreased noise radiation. Some of the following suggestions can be adopted to achieve them:

i. Fans, impellers, rotors, turbines and blowers should be operated at the lowest blade tip speeds that will still meet the job needs. Use large-diameter low-speed fans rather than small-diameter, high speed units for quiet operation. In short, maximize diameter and minimize tip speed.

ii. All other factors being equal, centrifugal squirrel-cage type fans are less noisy than van axial or propeller type fans.

iii. In air ventilation systems, a 50% reduction in the speed of the air flow may lower the noise output by 10 to 20 dB. Air speeds less than 3 m/s measured at a supply or return grille produce a level of noise that usually is unnoticeable in residential or office areas.

3. Reduction of frictional resistance: reducing friction between rotating, sliding, or moving parts in mechanical systems frequently results in smoother operation and lower noise output. Similarly, reducing flow resistance in fluid distribution systems results in less noise radiation. This can be achieved by the following methods:

i. Alignment: proper alignment of all rotating, moving, or contacting parts results in less noise output. Good axial and directional alignment in pulley systems, gear trains, shaft coupling, power transmission systems, and bearing and axle alignment are fundamental requirements for low noise output.

ii. Polish: highly polished and smooth surfaces between sliding, meshing, or contacting parts are required for quiet operation, particularly where bearings, gears, cams, rails, and guides are concerned.

iii. Balance: static and dynamic balancing or rotating parts reduces frictional resistance and vibration, resulting in lower noise output.

iv. Eccentricity (out of roundedness): off-centering of rotating parts such as pulleys, gears, rotors, and shaft/bearing alignment causes vibration and noise. Likewise, out of roundedness of wheels, rollers and gears causes uneven wear, resulting in flat spots that generate vibration and noise.

The noise generated from passage of fluid can be controlled by: i. Low fluid speeds: low fluid speeds avoid turbulence, which is one of the main

causes of noise. ii. Smooth boundary surfaces: duct or pipe systems with smooth interior walls,

edges, and joints generate less turbulence and noie than systems with rough or jagged walls or joints.

iii. Simple layout: a well-designed duct or pipe system with minimum of branches, turns, fittings and connectors is substantially less noisy than a complicated layout.

iv. Long-radius turns: changes in flow direction should be made gradually and smoothly. It has been suggested that turns should be made with a curve radius



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equal to about 5 times the pipe diameter or major cross-sectional dimension of the duct.

v. Flared sections: flaring of intake and exhaust openings, particularly in a duct system, tends to reduce flow speeds at tehse locations, often with substantial reductions in noise output.

vi. Streamline transition in flow path: changes in flow path dimensions or cross sectional areas should be made gradually and smoothly with tapered or flared transition sections to avoid turbulence. By keeping the cross-sectional area of the flow path as large and as uniform will reduce the noise.

vii. Remove unnecessary obstacles: more number of obstacles in flow path will result in more tortuous, turbulent flow and hence, produce more noise. It is advisable to design all the devices in the path and structural supports etc. as small as possible and as streamlined as possible to smooth out the flow patterns.

4. Reduction of radiating area: when the vibrating part is larger, the noise will also be greater accordingly. Hence, it is recommended while designing to minimize the effective radiating surface areas of the parts without impairing their operation or structural strength. This can be done by making parts smaller, removing excess material, or by cutting openings, slots, or perforations in the parts.

5. Reduction of noise leakage: noise can be substantially reduced by preventing or blocking the noise leakage. The following measures are suggested:

i. All unnecessary holes or cracks, particularly at joints, should be caulked. ii. All electrical or plumbing penetrations of the housing or cabinet should be

sealed with rubber gaskets or a suitable non-setting caulk. iii. If practical, all other functional or required openings or ports that radiate noise

should be covered with lids or shields edged with soft rubber gaskets to effect an airtight seal.

iv. Other openings required for exhaust, cooling or ventilation purposes should be equipped with mufflers or acoustically lined ducts.

v. Openings should be directed away from the operator and other people. 6. Isolation and damping of vibrating parts: the vibrational energy from a specific

moving part is transmitted through the machine structure, forcing other component parts and surfaces to vibrate and radiate sound-often with greater intensity than that generated by the originating source itself. Therefore, we must prevent energy transmission between the source and surfaces that radiate the energy and dissipate or attenuate the energy somewhere in the structure. Energy transmission can be prevented by isolation and energy dissipation can be achieved by damping.

i. Isolation: it involves the resilient mounting of the vibrating component on the most massive and structurally rigid part of the machine. All attachments or connections to the vibrating part in the form of pipes, conduits, and shaft couplers must be made with flexible or resilient connectors or couplers.

ii. Damping: damping materials or structures are those that have some viscous properties. They tend to bend or distort slightly, thus consuming part of the noise energy in molecular motion.

7. Provision of mufflers/silencers: they are in effect acoustical filters and are used when fluid flow noise is to be reduced. The devices can be classified into two fundamental groups: absorptive mufflers and reactive mufflers. An absorptive muffler is one whose noise reduction is determined mainly by the presence of fibrous or porous materials which absorbs the sound. A reactive muffler is one whose noise reduction is determined



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mainly by geometry. It is shaped to reflect or expand the sound waves with resultant self-destruction.


List out the seven available methods to control noise at source. How will you prevent noise leakage?


20.1.2 NOISE CONTROL IN TRANSMISSION PATH Devices or other structures can be set up in the transmission path to block or reduce the flow of sound energy before it reaches the receiver. This can be achieved in the following ways:

a) Absorption along the path b) Deflection of sound in some other direction c) Containing the sound by placing the source inside a sound- insulating box or

enclosure. 1. Absorbing material: noise, like light will bounce from one hard surface to

another. It is called reverberation. If a soft, spongy material is placed on the walls, floors, and ceiling, the reflected sound will be diffused and soaked up. Sound-absorbing materials such as acoustical tile, carpets, and drapes are placed on ceiling, walls, or floor to reduce the noise. However, the noise will be reduced about 2 to 10 dB depending on the frequency of the sound.

2. Barriers and panels: barriers, panels, screens or deflectors along the path of transmission will reduce the noise. The effectiveness of barrier depends upon its location, its height, and its length.

3. Enclosures: noisy machine can be placed in a separate room or box. The walls of the enclosure should be massive and airtight to contain the sound. Absorbent lining on the interior surfaces of the enclosure will reduce the reverberant buildup of noise within it. Structural contact between the noise source and the enclosure must be avoided.


Explain briefly noise control by barriers.




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……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

20.1.3 NOISE CONTROL AT RECEIVER When exposure to intense noise fields is required and none of the measures suggested above is possible, then measures are to be taken to protect the receiver. The following techniques are commonly adopted: 1. After work schedule: it is advisable to schedule the working hours of the employee

near the noisy machine, equipment, and/or operation. The scheduling can be done that a person spends less hours in a day and he/she is replaced by another person for next duration. Or the person can be allowed for exposure for a day and he/she can be allotted a task in less noisy environment for the rest of the week. The same cycle can be adopted. This approach will minimize the exposure duration of the worker.

2. Ear protection: the workers may be provided with ear protectors such as ear plugs, cup-type protectors and helmets.


Explain after work schedule.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 20.2 ENVIRONMENTAL NOISE MITIGATION

It is a set of strategies to reduce unwanted environmental sound. The main topics of

noise mitigation (alternatively known as noise abatement) a r e : transportation noise control, architectural design, and occupational noise control. Roadway noise and aircraft noise are the most pervasive sources of environmental noise worldwide,

20.2.1 ROADWAY NOISE CONTROL

Source control in roadway noise has provided little reduction in vehicle noise, except for the development of the hybrid vehicle; nevertheless, hybrid use will need to attain a market share of roughly fifty percent to have a major impact on noise source reduction on city streets. Highway noise is little affected by automobile type, since those



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effects are aerodynamic and tire noise related. Improved tire tread design can reduce the noise considerably. Better shielding of diesel stacks can also reduce the noise to a certain extent.

Speed control is effective since the lowest sound emissions arise from vehicles

moving smoothly at 30 to 60 kilometres per hour. Above that range sound emissions double with each five miles per hour of speed. At the lowest speeds, braking and (engine) acceleration noise dominates.

Selection of surface pavement can make a difference of a factor of two in sound

levels, for the speed regime above 30 kilometres per hour. Quieter pavements are porous with a negative surface texture and use medium to small aggregates; the loudest pavements have a transversely tined/grooved surface, and/or a positive surface texture and use larger aggregates. Obviously surface friction and roadway safety are important considerations as well for pavement decisions.

When designing new urban roads and arterial roads, by using computer models,

appropriate alignment and roadway geometry can be chosen in such a way to minimize the noise levels to the sensitive receptors. Noise barriers can be placed to reduce the noise levels. They are capable of reducing noise by 10 decibels. However, placement noise barrier requires other considerations such as design of barrier, terrain features and micrometeorology of the place. 20.2.2 AIR CRAFT NOISE CONTROL

The most promising forms of aircraft noise abatement is through land planning, flight operations restrictions and residential soundproofing. Flight restrictions can take the form of preferred runway use; departure flight path and slope; and time of day restrictions. These tactics are sometimes controversial since they can impact aircraft safety, flying convenience and airline economics. 20.2.3 NOISE CONTROL BY ARCHITECTURAL DESIGN As the noise reaches the people, we can design the houses and other buildings in such a way to protect the people in them. The architect can work with the acoustical scientist to arrive at the best cost effective means of creating a quiet interior (normally 45 dBA). The most important elements of design of the building skin are usually: glazing (glass thickness, double pane design etc.), roof material, caulking standards, chimney baffles, exterior door design, mail slots, attic ventilation ports and mounting of through the wall air conditioners.

Regarding sound generated inside the building, there are two principal types of transmission. Firstly, airborne sound travels through walls or floor/ceiling assemblies and can emanate from either human activities in adjacent living spaces or from mechanical noise within the building systems. Human activities might include voice, amplified sound systems or animal noise. Mechanical systems are elevator systems, boilers, refrigeration or



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air conditioning systems, generators and trash compactors. Since many of these sounds are inherently loud, the principal design element is to require the wall or ceiling assembly to meet certain performance standards (typically Sound transmission class of 50), which allows considerable attenuation of the sound level reaching occupants.

The second type of interior sound is called Impact Insulation Class (IIC)

transmission. This effect arises not from airborne transmission, but rather from transmission of sound through the building itself. The most common perception of IIC noise is from footfall of occupants in living spaces above. This type of noise is more difficult to abate, but consideration must be given to isolating the floor assembly above or hanging the lower ceiling on resilient channel.

Both of the above transmission effects may emanate either from building occupants

or from building mechanical systems such as elevators, plumbing systems or heating, ventilating and air conditioning units. In some cases it is merely necessary to specify the best available quieting technology in selecting such building hardware. In other cases shock mounting of systems to control vibration may be in order. In the case of plumbing systems there are specific protocols developed, especially for water supply lines, to create isolation clamping of pipes within building walls. In the case of central air systems, it is important to baffle any ducts that could transmit sound between different building areas. Designing special purpose rooms has more exotic challenges, since these rooms may have requirements for unusual features such as concert performance, sound studio recording, lecture halls. In these cases reverberation and reflection must be analyzed in order to not only quiet the rooms but prevent echo effects from occurring. In these situations special sound baffles and sound absorptive lining materials may be specified to dampen unwanted effects.

20.3 LET US SUM UP In this lesson we have learnt the control methods of noise pollution. We have learnt the three approaches to control noise at working environment. These three approaches mostly deal with engineering design of equipment and devices and other provisions in working environment. We also learnt the environmental noise control. Conceptually, the approaches of noise control are same for both indoor and outdoor noise.


· Take a sheet of paper and write down all the seven methods of control at source (you write this without copying)

· Write your feelings of exposure to highway noise · If your place is near air port, go near the air port and experience the aircraft

noise while landing and take-off. · Visit a cinema theater or a lecture hall or auditorium and note the architectural

design to control noise by echo.




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You have learnt the noise control methods in this lesson. You might be wondering

to learn the amount of measures to be undertaken. You may be now aware how difficult it is to live without noise. At the same time, we need to control it and the control measures will be expensive. There can be a trade-off in control measures and noise-generating activities. 20. CHECK YOUR PROGRESS

· Are you able to explain the control of noise at source · Are you able to explain the control of noise at transmission path · Are you able to explain the control of noise at receiver.

20. REFERENCES

1. Davis, M.L. and Cornwell, D.A. Introduction to Environmental Engineering, McGraw Hill, Inc., New York, 1991

2. Singal, S.P. Noise pollution and control, Narosa Publishing House, New Delhi, 2000.

3. Pandey, V. Noise pollution 4. Kudesia, V.P. and Tiwari, T.N. Noise pollution and its control 5. www.en.wikipedia.com 6. www.epq.nsw.gov.au



http://www.epq.nsw.gov.au/


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UNIT – V LESSON 21 – ROLE OF LEGISLATION IN AIR POLLUTION CONTROL Contents 21.0 Aims and objectives

21.1. Introduction 21.2. Indian Constitution and Fundamental Rights and Fundamental Duties 21.3. Need for legislation 21.4. Laws and Rules related to Air pollution 21.5. Let us sum up 21.6. Lesson-End Activities 21.7. Points for Discussion 21.8. Check your Progress 21.9. References


By now you must be familiar with atmospheric pollution in various forms: pollution by various substances - gases and particulates, pollution by radiation and radioactive substances and noise pollution. You gained knowledge on the effects of various kinds of atmospheric pollution on man, plants and animals and materials. You have also learned how to control them. Of course, there is no method available to completely control them and bring the pollution to zero level. You have learned the control of atmospheric pollution to the possible extent. In this Unit 5, you will be learning the role of legislation in our country, the law available to control the air pollution. That is control of air pollution by law. The Lesson 21 deals with the role of legislation to control air pollution. 21.1 INTRODUCTION

Every citizen of India is expected to know the law. A fundamental principle in jurisprudence is that “ignorance of law is not excusable”. However, most people are unaware of the law and their legal rights. People are like mute spectators to many of the environmental problems they face. People face in their every day life, various forms of pollution and are even affected by them. Harmful substances are released from vehicles and industries and people are exposed to them. Legislation is the passage enactment of relevant law. A nation is governed by the Acts and Rules enacted and framed by the Government. Every citizen of the country should abide by the Law and Rules laid by the Government. 21.2 INDIAN CONSTITUTION AND FUNDAMENTAL RIGHTS

FUNDAMENTA DUTIES



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Clean environment is a right of every citizen although it is not mentioned explicitly in the constitution. Article 21 of the Constitution is a fundamental right which reads as follows:

“No person shall be deprived of his life or personal liberty except according to

procedure established by law”. The Supreme Court and the various High Courts have given a wider interpretation

to the word “life” stated in this Article. According the Courts, the right to life includes the right to a living environment congenial to human existence.

Environmental Protection is a fundamental duty of every citizen of India under

Article 51-A(g) of the Constitution. It reads as follows: “It shall be the duty of every citizen of India to protect and improve the natural

environment including forests, lakes, rivers and wildlife and to have compassion for living creatures”.

This Article again expresses the need for clean environment. Further, the Constitution describes the responsibility of the State. Article 47 of the

Constitution reads as follows: “The State shall regard the raising of the level of nutrition and the standard of living

of its people and the improvement of public health as among its primary duties and, in particular, the State shall endeavor to bring about prohibition of the consumption except for medicinal purposes of intoxicating drinks and of drugs which are injurious to health”.

The 42nd Amendment to the Constitution was brought about in the year 1976. Two

new Articles were inserted: Art. 48-A and Art. 51-A(g). Article 48-A, under Directive Principles of State Policy, makes it the responsibility of the State Government to protect and improve the environment and to safeguard the forests and wildlife of the country. Article 51-A(g) under Fundamental Duties, makes it the fundamental duty of every citizen to protect and improve the natural environment including forests, lakes, rivers and wildlife and to have compassion for living creatures. Self-check Exercise 1

Is clean environment a fundamental right as per the Constitution of India? If so

explain.

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………



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………………………………………………………………………………………………………………………………………………………………. 21.3 NEED FOR LEGISLATION

Air pollution is a problem faced by the citizens of a country. Hence, there is a need

for legislation and enactment of act to control the air pollution. Complete elimination of pollution is not practicable, but there could be improvement in air quality. Such improvement can be achieved by legislation more effectively.

Over the years, there has been a considerable growth in the field of environmental

law. Environmental Tribunals, Green Benches and a National Environmental Appellate Authority have been constituted. Public Hearing has become mandatory for approval of any new project. India has enacted laws to protect the environment. 21.4 LAWS AND RULES RELATED TO AIR POLLUTION The following laws and rules are enacted and framed by the Government of India for the protection of Air quality:

· The Air (Prevention and Control of Pollution) Act, 1981 · The Air (Prevention and Control of Pollution) Rules, 1982 · The Environment (Protection) Act, 1986 · The Environment (Protection) Rules, 1986 · The National Environmental Tribunal Act, 1995 · The National Environmental Appellate Authority Act, 1997

While the first two directly deals with air pollution, the others indirectly express the

concern towards air quality. The Environment (Protection) Act and The Environment (Protection) Rules include all kinds of pollution including the air pollution and thereby they support and strengthen the Air Act, 1981 and Air Rules, 1982.

21.5 LET US SUM UP Every country is governed by its legislation – laws and rules. Protection of environment has become important as the environmental problems are mounting in the recent years. Thus, it is imperative to the Government to enact rules and frame rules to protect and conserve the environment. With these objectives, the Government of India has enacted various legislations to protect the environment. The Air (Prevention and Control of Pollution) Act, 1981 and The Air (Prevention and Control of Pollution) Rules, 1982 are legislation regarding air pollution enacted by the Government of India. 21.6 LESSON-END ACTIVITIES

· Write down in a sheet of paper, the need for legislation · Take a sheet of paper and discuss and describe the fundamental rights and duties

regarding air pollution control



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· Legislation plays very important and crucial role in maintaining the order of a country.

· Fundamental rights and duties mentioned in the Constitution of India · Interpretations of fundamental rights and duties for the protection of air quality


· Can you explain the need for legislation for protecting air quality? · Can you list the laws and rules related to protection of air quality? · Can you substantiate the importance of environmental protection by

fundamental rights and duties mentioned in the Constitution.

21.9 REFERENCES

1. C.P.R. Environmental Education Centre, Environmental Laws of India, an introduction, C.P.R. Environmental Education Centre, Chennai




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LESSON 22 – THE AIR (PREVENTION AND CONTROL OF

POLLUTION) ACT, 1981 Contents 22.0 Aims and objectives

22.1. Introduction 22.2. The Air (Prevention and Control of Pollution) Act, 1981

22.2.1. Object of Air Act 22.2.2. Chapter I - Preliminary


22.0 AIMS AND OBJECTIVES This lesson deals with the Air (Prevention and Control of Pollution) Act, 1981 and the Amendments. You will learn in detail the provisions of this Act, its application, its power etc. This lesson will give you a comprehensive idea about the Act.

22.1 INTRODUCTION The Government of India has enacted The Air (Prevention and Control of Pollution)

Act, 1981. It came into force from May 16, 1981. The Act is applicable throughout the country. The Act provides for an integrated approach for tackling environmental problems relating to the pollution.

The State Governments have been authorized to declare, after consultation with the State Boards, any area or areas within the states as air pollution control area or areas. These areas may be extended, reduced or even merged together in course of time. Pollution by ships and aircraft is not covered by the provisions of the Act. The Act includes the following:

1. Definitions of terms used 2. Constitution of the Central Board and State Boards 3. Functions of Boards 4. Powers of Boards and 5. Penalties and procedure

22.2 THE AIR (PREVENTION AND CONTROL OF POLLUTION)

ACT, 1981 No 14 of 1981



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[29th March, 1981]

An Act to provide for the prevention, control and abatement of air pollution, for the establishment, with a view to carrying out the aforesaid purposes, of Boards, for conferring on and assigning to such Boards powers and functions relating thereto and for matters connected therewith.

WHEREAS decisions were taken at the United Nations conference on the Human Environment held in Stockholm in June, 1972, in which India participated, to take appropriate steps for the preservation for the natural resources of the earth which, among other things, include the preservation of the quality of air and control of air pollution.

AND WHEREAS it is considered necessary to implement the decisions aforesaid in so far as they relate to the preservation of the quality of air and control of air pollution;

BE it enacted by Parliament in the Thirty-second Year of the Republic of India as follows :-

The Air Acts framework is to enable integrated approach to environmental problems, the Air Act expanded the authority of the Central and State Boards established under the Water Act, to include air pollution. States not having air pollution boards were required to set up air pollution boards.

Under the Air Act all industries operating within designated air pollution control areas must obtain “consent” (permit) from the State Boards. These States are required to prescribe emission standards for industry and automobiles after consulting the Central Board.

22.2.1 OBJECT OF AIR ACT The objects of Air (Prevention and Control of Pollution) ACT, 1981 [Act No. 14 of 1981] are;

1. to provide for the prevention of air pollution 2. for control of air pollution 3. for abatement of air pollution 4. for the establishment of Pollution Control Boards 5. for conferring and assigning powers and functions on such Boards; and 6. to implement the decisions taken at the United Nations Conference on the

Human Environment held in Stockholm in June 1972, in which India participated, to take appropriate steps for the preservation of the natural resources of the earth which, among other things, include the preservation of the quality of air and control of air pollution.

22.2.2 CHAPTER I - PRELIMINARY



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1. Short title, extent and commencement

(1) This Act may be called the Air (Prevention and Control of Pollution) Act, 1981. (2) It extends to the whole of India (3) It shall come into force on such date as the Central Government may, by notification in the official Gazette, appoint.

Self-check Exercise 2 Write the short title of the Act. State whether this act is applicable to whole India or only in certain States. Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 2. Definitions In this Act, unless the context otherwise requires:- (a) ”air pollutant” means any solid, liquid or gaseous substance 2[(including noise)]

present in the atmosphere in such concentration as may be or tent to be injurious to human beings or other living creatures or plants or property or environment;

(b) “air pollution” means the presence in the atmosphere of any air pollutant; (c) “approved appliances” means any equipment or gadget used for the brining of any

combustible material or for generating or consuming any fume, gas of particulate matter and approved by the State Board for the purpose of this Act;

(d) “approved fuel” means any fuel approved by the State Board for the purposes of this Act;

(e) “automobile” means any vehicle powered either by internal combustion engine or by any method of generating power to drives such vehicle by burning fuel;

(f) “Board” means the Central Board or State Board; (g) “Central Board” means the 3[Central Board for the Prevention and Control of Water

Pollution] constituted under section 3 of the water (Prevention and Control of Pollution) Act 1974;

(h) “Chimney” includes any structure with an opening or outlet from or through which any air pollutant may be emitted;

(i) “control equipment” means any apparatus, device, equipment or system to control the quality and manner of emission of any air pollutant and includes any device used for securing the efficient operation of any industrial plant;

(j) “emission” means any solid or liquid or gaseous substance coming out of any chimney, duct or flow or any other outlet;

(k) “industrial plant” means any plant used for any industrial or trade purposes and emitting any air pollutant into the atmosphere



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(l) “Permissible” means prescribed by rules made under this Act by the Central Government or as the case may, the State Government; (l) "member" means a member of the Central Board or a State Board, as the case may

be, and includes the Chairman thereof,

(m) "occupier", in relation to any factory or premises, means the person who has control over the affairs of the factory or the premises, and includes, in relation to any substance, the person in posse ssion of the substance;]

(n) "prescribed" means prescribed by rules made under this Act by the Central Government or as the case may be, the State government;

(o) "State Board" means,- (i) in relation to a State in which the Water (Prevention and Control of Pollution) Act,

1974, is in force and the State Government has constituted for that State a 5[State Board for the Prevention and Control of Water Pollution] under section 4 of that Act, the said State Board; and

(ii) in relation to any other State, the State Board for the Prevention and Control of Air Pollution constituted by the State Government under section 5 of this Act.

Self-check Exercise 3 Define the following:

1. Emission 2. Air pollution 3. Chimney


……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

22.3 LET US SUM UP In this lesson the Air (Prevention and Control of Pollution) Act, 1981 is described. The title, and the object of the Act are described. The definitions of the terms used in the Act are presented.

22.4 LESSON-END ACTIVITIES Go through the definitions of the Act and try to reproduce them on a sheet of paper. 22.5 POINTS FOR DISCUSSION · The Act describes two kinds of Boards – one at Centre level and other at State level · The Act deals with almost all kinds of air pollution



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· Can you define air pollution as per the Act. · Can you describe the definitions given in the Act

22.7 REFERENCES



3. www.envfor.nic.in/legis


http://www.envfor.nic.in/legis


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LESSON 23 – CENTRAL AND STATE BOARDS – THEIR FUNCTIONS AND

POWERS Contents 23.0 Aims and objectives

23.1. Introduction 23.2. Constitution of the Central Board 23.3. Constitution of State Boards 23.4. Functions of the State Pollution Control Board

23.4.1 Powers of the State Pollution Control Board 23.5. Functions of the Central Pollution Control Board 23.5.1 Powers of the control pollution control board 23.6. Powers of the Central Government 23.7. Powers of the State Government 23.8. Penalties 23.9. Offences by companies and by Government Departments 23.10. Classification of pollution sources

23.10.1 Industries specified in the Schedules 23.11. Let us sum up 23.12. Lesson-end Activities 23.13. Points for Discussion 23.14. Check your Progress 23.15. References 23.16. Foot Note

23.0 AIMS AND OBJECTIVES In the preceding lessons, we have learnt the need for legislation and the Air Act. In this lesson we are going to learn the functions and powers of both the Central and the State Boards. You will be learning the organizational set up of these Boards.

23.1 INTRODUCTION Chapter II of the Act deals with the Central and State Boards. Central Board comes under the purview of the Central Government and it has the role of overall monitoring of the State Boards. The State Boards are come under the purview of the State Governments. In fact the State Boards have more responsibilities to look after the pollution and prevention issues of that State. 23.2 CONSTITUTION OF THE CENTRAL BOARD Originally, the Central Board for Prevention and Control of Water Pollution was constituted under the Water Act. After the enactment of the Air Act, the same Board has been assigned the task of exercising the powers and functions of the Air Act too. As a



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result, the Board is renamed as the Central Pollution Control Board. As this new name suggests, the Board has additional responsibilities in exercising almost all the laws and rules relevant to various aspects of environment. The exercising power is assigned to the Central Board as per Section 3 of the Act, which is as follows: Central Board for the Prevention and Control of Air Pollution. The Central Board for the Prevention and Control of Water Pollution constituted under section 3 of the Water (Prevention and Control of Pollution) Act, 1974 (6 of 1974), shall, without prejudice to the exercise and performance of its powers and functions under this Act, exercise the powers and perform the functions of the Central Board for the Prevention and Control of Air Pollution under this Act.

23.3 CONSTITUTION OF STATE BOARDS The constitution of State Boards in each State of the Country is specified in Sections 4 and 5. The Section 4 and 5 are described below:

7[4. State Boards for the Prevention and Control of Water Pollution to be, State Boards for the Prevention and Control of Air Pollution. In any State in which the Water (Prevention and Control of Pollution) Act, 1974 (6 of 1974), is in force and the State Government has constituted for that State a State Board for the Prevention and Control of Water Pollution under section 4 of that Act, such State Board shall be deemed to be the State Board for the Prevention and Control of air Pollution constituted under section 5 of this Act and accordingly that State Board for the Prevention and Control of Water Pollution shall, without prejudice to the exercise and performance of its powers and functions under that Act, exercise the powers and perform the functions of the State Board for the Prevention and Control of Air Pollution under this Act.] 5. Constitution of State Boards. (1) In any State in which the Water (Prevention and Control of Pollution) Act, 1974 (6 of 1974), is not in force, or that Act is in force but the State Government has not constituted a [State Board for the Prevention and Control of Water Pollution] under that Act, the State Government shall, with effect from such date as it may, by notification in the Official Gazette, appoint, constitute a State Board for the Prevention and Control of Air Pollution under such name as may be specified in the notification, to exercise the powers conferred on, and perform the functions assigned to, that Board under this Act. (2) A State Board constituted under this Act shall consist of the following members, namely:-

(a) a Chairman, being a person, having a person having special knowledge or practical experience in respect of matters relating to environmental protection, to be nominated by the State Government: Provided that the Chairman my be either whole-time or part-time as the State Government may think fit;



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(b) such number of officials, not exceeding five, as the State Government may think fit, to be nominated by the State Government to represent that government;

(c) such number of persons, not exceeding five, as the State Government may think fit, to be nominated by the State Government from amongst the members of the local authorities functioning within the State;

(d) such number of non-officials, not exceeding three, as the State Government may think fit, to be nominated by the State Government to represent the interest of agriculture, fishery or industry or trade or labour or any other interest, which in the opinion of that government, ought to be represented;

(e) two persons to represent the companies or corporations owned, controlled or managed by the State Government, to be nominated by that Government;

[(f) a full-time member-secretary having such qualifications knowledge and experience of scientific, engineering or management aspects of pollution control as may be prescribed, to be appointed by the State Governments

Provided that the State Government shall ensure that not less than two of the members are persons having special knowledge or practical experience in, respect of matters relating to the improvement of the quality of air or the prevention, control or abatement of air pollution.

(3) Every State Board constituted under this Act shall be a body corporate with the name specified by the State Government in the notification issued under sub-section (1), having perpetual succession and a common seal with power, subject to the provisions of this Act, to acquire and dispose of property and to contract, and may by the said name sue or be sued.

As the State Board shall not be constituted for a Union territory, the Central Pollution Control Board will execute all the powers and functions specified in the Act as per the Section 6 of the Act:

6. Central Board to exercise the powers and perform die functions of a State Board in the Union territories.

No State Board shall be constituted for a Union territory and in relation to -a Union territory, the Central Board shall exercise the powers and perform the functions of a State Board under this Act for that Union territory Provided that in relation to any Union territory the Central Board may delegate all or any of its powers and functions under this section to such person or body of persons as the Central Government may specify. Section 7 of the Act describes the terms and conditions of service members of the State Boards; Section 8 of the Act explains the conditions under which a member can be disqualified.



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In nutshell, it can be said that a Sate Board consists of 17 members all nominated by the State Government as follows:

1. A full time or part time Chairman 2. Five official members to represent the Government 3. Five persons representing the local authority 4. Three non-official members 5. Two persons representing companies/corporations owned or managed by the State

Government 6. A full time Member-Secretary

State Board’s officers have been authorized to enter and inspect any place to ensure

implementation of the Act. They can collect samples of air or emission for analysis from any chimney, flue, duct or any other outlet in the prescribed manner. Violation of the various provisions of the Act has been made punishable with imprisonment and a fine.


1. How many members does the State Board consist of? 2. Is the State Board constituted for a Union Territory? If not, who will exercise

the functions and powers of the Act? Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

23.4. FUNCTIONS OF THE STATE POLLUTION CONTROL BOARD

Section 17 of the Air Act enumerates the functions of the State Pollution Control Board. According to Section17, the functions of the State Pollution Control Board shall be:

1. To plan a comprehensive program for the prevention, control or abatement of air pollution and to secure the execution thereof;

2. To advise the State Government on any matter concerning the prevention, control or abatement of air pollution;

3. To collect and disseminate information relating to air pollution; 4. To collaborate with the Central Board in organizing the training of persons engaged

in programs relating to air pollution; 5. To organize mass-education program relating to prevention, control or abatement of

air pollution; 6. To inspect, at all reasonable times, any control equipment, industrial plant or

manufacturing process; 7. To give, by order, such directions to such persons as it may consider necessary to

take steps for the prevention, control or abatement of air pollution;



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8. To inspect air pollution control areas at such intervals as it may think necessary, assess the quality of air therein and take steps for the prevention, control or abatement of air pollution in such areas;

9. To lay down, standards for emission of air pollutants into the atmosphere from industrial plants and automobiles or for the discharge of any air pollutant into the atmosphere from any other source whatsoever not being a ship or an aircraft: PROVIDED that different standards for emission may be laid down under this clause for different industrial plants having regard to the quantity and composition of emission of air pollutants into the atmosphere from such industrial plants;

10. To advise the State Government with respect to the suitability of any premises or location for carrying on any industry which is likely to cause air pollution;

11. May establish or recognize a laboratory or laboratories to enable the State Board to perform its functions under this section efficiently.

12. To perform such other functions as may be prescribed or as may, from time to time, be entrusted to it by the Central Board or the State Government;

13. To do such other things and to perform such other acts as it may think necessary for the proper discharge of its functions and generally for the purpose of carrying into effect the purposes of this Act.

23.4.1 POWERS OF THE STATE POLLUTION CONTROL BOARD The State Pollution Control Board is conferred with certain very important power like;

1. Power to grant, refuse and cancel consent; 2. Power to make application to cope for retraining persons from causing pollution; 3. Power to take certain remedial measures to mitigate the emission of air pollutants; 4. Power to entry and inspection; 5. Power to obtain information; 6. Power to take samples of air or emission etc; 7. Power to issue directions

23.5 FUNCTIONS OF THE CENTRAL POLLUTION CONTROL

BOARD Section 16 of the Air Act has enumerated a list of functions to be discharged by the Central Pollution Control Board. The main functions of the Central Pollution Control board shall be;

1. To improve the quality of the air and 2. To prevent, control or abate air pollution in the country

Apart from improving the quality of air and preventing, controlling and abating air pollution in the country, the Central Board may discharge the following functions.

1. Advice the Central Government on any matter concerning the improvement of the quality of the air and the prevention, control or abatement of air pollution;



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2. Plan and cause to be executed a nation – wide program for the prevention, control or abatement of air pollution;

3. Co-ordinate the activities of the State Boards and resolve disputes among them; 4. Provide technical assistance and guidance to the State Board; 5. Carryout and sponsor investigations and research relating to problems of air

pollution and prevention, control or abatement of air pollution; 6. Plan and organize the training of persons engaged or to be engaged in programs for

the prevention, control or abatement of air pollution; 7. Organize through mass media a comprehensive program regarding the prevention,

control or abatement of air pollution; 8. collect, compile and publish technical and statistical data relating to air pollution

and the measures devised for its effective prevention, control or abatement; 9. Prepare manuals, codes or guides relating to prevention, control of abatement of ir

pollution; 10. Lay down standards of the quality of air; 11. Collect and disseminate information in respect of matters relating to air pollution 12. Perform such other functions as may be prescribed; 13. Established or recognized laboratories to enable the Central Board to perform its

functions under the section efficiently. 14. Delegates any of this function under this Act generally of specially to any of the

committees appointed by it 15. Do such other things and perform such other Act, as it may think necessary for the

proper discharge of its functions and generally for the purposes of carrying in to effecting purposes of this Act

23.5.1 POWERS OF THE CENTRAL POLLUTION CONTROL

BOARD

Under Section 31A, the Central Pollution Control Board may, in the exercise of its powers and performance of its functions under this Act, issue any direction in writing to any person, officer or authority, and such person, officer or authority shall be bound to comply with such directions. The power to issue any direction includes the power to direct –

(a) The closure, prohibition or regulation of any industry, operation or process; or (b) The stoppage or regulation of supply of electricity, water or any other service.

Self-check Exercise 5 What are the Sections that specify the functions of CPCB and State PCBs? Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….



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23.6 POWERS OF THE CENTRAL GOVERNMENT

Under Sec. 18 the Central Government is vested with the powers to give such directions to the Central Pollution Control Board, those are necessary for the performance of its functions.

23.7 POWERS OF THE STATE GOVERNMENT Under Section 19 the State Government has the Power to declare air pollution control areas and to prohibit the use of any fuel, appliance or burning of any material in any air pollution control area, as detailed below: (1) The State Government may, after consultation with the State Board, declare any

area or areas for the purposes of this Act. (2) The State Government may, after consultation with the State Board,

(a) Alter any air pollution control area where by way of extension or reduction; (b) Declare a new air pollution control area in which may be merged one or

more existing air pollution existing air pollution control areas or any part or part thereof.

(3) If the State Government, after consultation with the State Board, is of opinion that the use of any fuel, other than an approved fuel, in any air pollution control area or part thereof, may cause or is likely to cause air pollution, it may, prohibit the use of such fuel in such area or part thereof

(4) The State Government may, after consultation with the State Board, direct that, no appliance, other than an approved appliance, shall be used in the premises situated in an air pollution control area:

(5) The State Government may, after consultation with the State Board, prohibit the burning of any material in such area or part thereof. Under Section 20 the State Government has the power to give instructions to the concerned authority in charge of registration of motor vehicles under the Motor Vehicles Act, 1939, to comply with such instructions for ensuring standards for emission from automobiles, as laid down by the State Control Board.

23.8 PENALTIES

Under the Air Act, Sections 37, 38 and 39 prescribes penalties. Section 37 prescribes punishment for failure to comply with the provisions of section 21 or 22 or with the directions issued under Section 31 A. Hence,

1. if a person establishes or operates any industrial plant in an air pollution control area without the previous consent of the State Board(Sec. 21); or

2. If any person operating any industrial plant in any air pollution control area discharges or cause or permit to be discharged the emission of any air pollutant in excess of the standards laid down by the SPCB (Sec. 22); or

3. if any person fails to comply with the directions given by the Pollution Control Boards under section 31 A (directions to close, prohibit or regulate any industry,



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operation or process; or to stop or regulate supply of electricity, water or any other services);

He/She shall be punishable with imprisonment for a term not less than 1 year and six months, which may extend upto six years with fine. In case the failure continues, he/she shall punishable with an additional fine, which may extend to 5000 rupees for every day during which the failure continues. Section 37 further provides that if the failure continues beyond a period of one year after the date of conviction, the offender Shall be punishable with imprisonment for a term which shall not be less than 2 years but which may extend to 7 years and with fine.


Describe the penalties suggested for offenders and defaulters Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 23.9 OFFENCES BY COMPANIES AND BY GOVERNMENT

DEPARTMENTS

Where an offence under the Air Act has been committed by the Company, every person who at the time the offence was committed was in charge of, and was responsible to the company for the conduct of the business of the company, as well as the company shall be deemed to be guilty of the offence. However, if the person liable to be punished proves that the offence was committed without his knowledge or that he exercised all due diligence to prevent the commission of such offence, he will not be made liable for any punishment under the Act.

Where the Department of Government has committed an offence under the Air Act, the Head of the Department shall be deemed to be guilty of the offence. However, if the head of the Department proves that the offence was committed without his knowledge or that he exercised all due diligence to prevent the commission of such offence, he / she shall nit be made liable to punishment under the Act. Self-check Exercise 7

Describe the penalties suggested for offences by Government Departments Note: Please do not proceed unless you write answers for the above two in the space given below:



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………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 23.10 CLASSIFICATION OF POLLUTION SOURCES Section 19-26 of the Act is the operative section of the Act. On perusal of these sections, the sources of air pollution can be divided into three categories

1. Major air polluting industries (20 industries listed in Schedule attached to the Act)

2. Automobiles excluding ships and aircraft 3. Other sources including domestic sources

23.10.1 INDUSTRIES SPECIFIED IN THE SCHEDULE

1. Asbestos and asbestos products industries 2. Cement and cement products industries 3. Ceramic and ceramic products industries 4. Chemical and allied industries 5. Coal and lignite based chemical industries 6. Engineering industries 7. Ferrous metallaurgical industries 8. Fertilizer industries 9. Foundries 10. Food and Agriculture products industries 11. Mining industries 12. Non-ferrous metallurgical industries 13. Ores/mineral processing industries including beneficiation, pelletization etc. 14. Power (coal, petroleum and their products) generating plants and boiler plants 15. Paper and pulp (including paper products) industries 16. Textile processing industries 17. Petroleum refineries 18. Petroleum products and petrochemical industries 19. Plants for recovery from and disposal of wastes 20. Incinerators

23.11 LET US SUM UP In this lesson, we have learnt about the Government’s commitment in controlling the air pollution by establishing the Central and State Pollution Control Boards. We have learnt the powers and functions of the Boards. We came to know the list of industries specified in the schedule. We also learnt the penalties and actions against the defaulters.



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23.12 LESSON-END ACTIVITIES · Take a sheet of paper and write the functions and powers of the Central

Pollution Control Board · Write the functions and powers of the State Pollution Control Board\ · Learn yourself either by browsing the net or by going through the relevant

books / literature if there are any deviations within the State Pollution Control Boards

23.13 POINTS FOR DISCUSSSION

· Powers and functions of the CPCB and SPCBs · Powers of the Central Government and State Government


· Can you distinguish the CPCB and SPCB with reference to their functions and powers?

· Can you list out the industries specified in the schedule? · Can you describe the members of the Board and their designations and duties?

23.15 REFERENCES







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LESSON 24 – THE AIR (PREVENTION AND CONTROL OF POLLUTION) RULES, 1982

Contents


24.1. Introduction 24.2. Chapter 1 – Preliminary 24.3. Chapter 2 – Procedure for transaction of business of the Board and its

Committees 24.4. Chapter 3 24.5. Chapter 4 – Temporary Association of persons with the Central Board 24.6. Chapter 5 – Budget of the Central Board 24.7. Chapter 6 – Annual Report of the Central Board 24.8. Chapter 7 – Account of the Central Board 24.9. Let us sum up 24.10. Lesson-end Activities 24.11. Points for Discussion 24.12. Check your Progress 24.13. References

24.0 AIMS AND OBJECTIVES In preceding lessons we learnt the Air (Prevention and Control of Pollution) Act, 1981 in detail. In this lesson, we are going to learn the Rules of the Act. The Rules specify the ways by which the Act can be practiced and exercised. 24.1 INTRODUCTION As per the Notification of the Department of Environment dated 18 November, 1982, the rules come into effect. G.S.R. 712(E):-In exercise of the powers conferred by section 53 of Air Prevention and Control of Pollution) Act, 1981 (14 of 1981) the Central Government in consultation with the Central Board for the Prevention and Control of Water Pollution hereby makes the following rules, namely, the Air (Prevention and Control of Pollution) Rules, 1982. 24.2 CHAPTER 1 - PRELIMINARY 1. Short title and commencement. (1) These rules may be called the Air (Prevention and Control of Pollution) Rules, 1982. (2) They shall come into force on the date of their publication in the Official Gazette. 2. Definitions. In these rules unless the context otherwise requires.- (a) "Act" means the Air (Prevention and Control of Pollution) Act, 1981; (b) "Chairman" means the Chairman of the Central Board; (c) "form" means a form set out in the Schedules;



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(d) "meeting" means a meeting of the Central Board or a meeting of Committee constituted by the Central Board; (e) "member Secretary" means the member secretary of the Central Board; (f) "Schedule" means a Schedule appended to these rules; (g) "section" means a section of the Act; (h) "year" means the financial year commencing on the 1st day of April; (i) words and expressions not defined in these rules but defined in the Act shall have the meaning assigned to them in the Act. Self-check Exercise 8

· Define the term form · Define the term schedule · Define the term year


24.3 CHAPTER 2 - PROCEDURE FOR TRANSACTION OF BUSINESS OF THE BOARD AND ITS COMMITTEES

3. Notice of meetings. (1) Meeting of the Central Board shall be held on such dates as may be fixed by the Chairman. (2) The Chairman shall, upon a written request of not less than five members of the Central Board or upon a direction of the Central Government, call a special meeting of the Central Board. (3) Fifteen clear days' notice of an ordinary meeting and three days' notice of a special meeting specifying the time and the place at which such meeting is to be held and an agenda of business to be transacted thereat, shall be given by the member-secretary or Chairman to the members or any other officers of the Board. (4) Notice of the meeting may be given to the members by delivering the same by messenger or sending it by registered post to his last known place of S residence or business or in such other manner as-the Chairman may, in the circumstances of the case, think fit. (5) No member shall be entitled to bring forward for the consideration of a meeting any matter of which he has not given ten clear-day's notice to the member Secretary unless the Chairman, in his discretion, permits him to do so. (6) If the Chairman or presiding officer adjourns a meeting from day to day or any particular day he shall give reason thereof and no fresh notice shall be required for such an adjourned meeting; 4. Presiding Officer.



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Every meeting shall be presided over by the Chairman and in his absence, by a presiding officer to be of elected by the members present from amongst themselves. 5. All questions to be decided by majority. (1) All questions at a meeting shall be decided by-a majority of votes of members present and voting shall be by raising of hands in favour of the proposal. (2) In case of an equality of votes, the Chairman or presiding officer shall have a second or casting vote. 6. Quorum. (1) Five members shall form the quorum for any meeting. (2) If at any time fixed for any meeting or during the course of any meeting a quorum is not present, the Chairman or presiding member shall adjoin the meeting and if a quorum is not present after the expiration of fifteen minutes from such adjournment, the presiding officer shall adjourn the meeting to such time on the following or on such other future date as he may fix. (3) If the meeting is adjourned to some future date due to lack of quorum, fresh notice will be given to the absentee members as to the date and time on which the next meeting will be held. (4) No matter which had not been on the agenda of the original meeting shall be discussed at such adjourned meeting. 7. Minutes. (1) Record of the proceedings of every meeting along with the names of members who attended the meeting shall be kept by the member-secretary in a book maintained by him exclusively for the purpose. (2) The minutes of the previous meeting shall be read at the beginning of every succeeding meeting and shall be confirmed and signed by the Chairman or presiding officer at such meeting, (3) The proceedings shall be open to inspection by any member at the once of the Central Board during office hours.

8. Maintaining order at meetings.

The Chairman or presiding officer shall preserve order at a meeting.

9. Business to be transacted at a meeting.

(1) No business shall be transacted in the meeting without quorum.

(2) Except with the permission of the chairman or presiding officer, no business which is not entered in the agenda or of which notice has not been given by a member under sub-rule (5) of the rule 3, shall be transacted at any meeting.

10. Order of business.

(1) At any meeting business shall be transacted in the order in which it is entered in the agenda circulated to the members under sub-rule (3) of rule 3.

(2) Either at the beginning of the meeting or after the conclusion of the debate on a motion during the meting, the Chairman or presiding officer or a member may suggest a change in



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the order of business as entered in the agenda and if the majority of the members present agree, the Chairman or presiding officer shall agree to such a change.

11. Procedure for transaction of business of committees constituted by the Board under sub-section (1) of Section 11.

(1) The time and place of the meting of a committee constituted by the Central Board under sub-section (I) of section 11 shall be as specified by the Chairman of the committee.

(2) Provision of Chapter-2 of these rules shall as far as practicable, apply to the meeting of the committee constituted under section 11.


· Who is the presiding officer of the meeting? · What is the required quorum of the meeting?

Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. 24.4 CHAPTER 3 12. A member of a committee other than a member of the Board shall be paid an allowance of rupees fifty if he is a resident of Delhi and rupees seventy-five (inclusive of daily allowance3 and also travelling allowance at such rate as is admissible to a grade I officer of the Central Government in the case of non resident, for each day of the actual meeting of the committee which he attends. Provided that in case of a member of Parliament who is also a member of the Central Board, the said daily and travelling allowances will be admissible when the Parliament is not in session and on production of a certificate by the member that he has not drawn any such allowance for the same journey and halts from any other Government source. 24.5 CHAPTER 4 - TEMPORARY ASSOCIATION OF PERSONS

WITH THE CENTRAL BOARD 13. Manner and purpose of Association of persons with the Central Board under sub-section (1) of section 12. The Central Board may invite any person whose assistance or advise is considered useful in performing any of its functions, to participate in the deliberations of any of its meetings or the meetings of a committee formed by it



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14. Fees and allowances to be paid to such temporary association of persons under sub-section (3) of section 12. (1) If the person associated with the Board under rule 13 happens to be a non-official resident in Delhi, he shall be entitled to get an allowance of rupees fifty per day for each day of actual meeting of the Central Board in which he is so associated. (2) If such person is non-resident of Delhi, he shall be entitled to get an allowance of rupees seventy five per day (inclusive of daily allowance) for each day of actual meeting of the Central Board when he is so associated and also to travelling allowance at such rates as is admissible to a grade I officer of the Central Government. (3) Notwithstanding anything in sub-rules (I) and (2) if such person is a Government servant or an employee in a Government undertaking, he shall be entitled to travelling and daily allowances only at the rates admissible under the relevant rules applicable to him: Provided that in case of a member of Parliament who is also a member of the Central Board, the said daily and travelling allowances will be admissible when the Parliament is not in session and on production of a certificate by the member that he has not drawn any such allowance for the same journey and halts from any other Government source. 24.6 CHAPTER 5 - BUDGET OFTHE CENTRAL BOARD 15. Form of budget estimates under section 34. (1) The form in which and time within which the budget may be prepared and provided and forwarded to the government shall be as provided in forms I, II, III and IV of Schedule 1. (2) The estimated receipts and expenditure shall be accompanied by the revised budget estimates for the current year. (3) The budget shall, as far as may be, based on the account heads specified in Schedule 11.

24.7 CHAPTER 6 - ANNUAL REPORT OFTHE CENTRAL BOARD 16. Form of Annual Report under section 35. The annual report in respect of the year last ended giving a true and full account of the activities of the Central Board during the previous financial year shall contain the particulars specified in Schedule 111 and shall be submitted to the Central Government by 15th of May each year. 24.8 CHAPTER 7 - ACCOUNT OF THE CENTRALBOARD 17. Form of annual statement of accounts of the Central Board under section 36. The annual statement of accounts of the Central Board shall be in forms V to IX. 24.9 LET US SUM UP In this lesson we have learnt about the Rules of the Air (Prevention and Control of Pollution) Act, 1981. We have learnt the procedure for transaction of business and of the Board and committees. We also learnt that the CPCB will prepare annual report every year. 24.10 LESSON-END ACTIVITIES



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· Take a sheet of paper and write the definitions given · Practice writing the procedure of transacting the business of the Board

24.11 POINTS FOR DISCUSSSION · Conduct of meeting · Temporary association of persons with the Board


· Can you explain the procedure for transacting the business? · Can you explain the order of the meeting? · Can you describe the temporary association of persons with the Board?

24.13 REFERENCES







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LESSON 25 - THE MOTOR VEHICLES ACT, 1988 Contents 25.0 Aims and objectives

25.1. Introduction 25.2. Chapter I – Preliminary 25.3. Licensing of drivers of motor vehicles – necessity for driving license (Section 3)

25.3.1. Grant of Learner’s License 25.3.2. Grant of Driving License 25.3.3. Power of licensing authority to disqualify from holding a driving license or

revoke such license 25.4. Power of Central Government to make rules 25.5. Power of State Governments to make rules 25.6. Liability without fault in certain cases 25.7. Offences, penalties and procedure 25.8. Chapter VII – Construction, equipment and maintenance of motor vehicles 25.9. Let us sum up 25.10. Lesson-end Activities 25.11. Points for Discussion 25.12. Check your Progress 25.13. References

25.0 AIMS AND OBJECTIVES In this lesson we are going to learn the Motor Vehicle Act, 1988. You may wonder why we should learn this Act under air pollution. In fact, this Act deals with the issue of licence to the drivers and conductors, and issue of registration certificate to the owners of the vehicle. As the vehicles are major contributors of air pollution, the Government has laid conditions that all vehicles manufactured comply the environmental standards. 25.1 INTRODUCTION The motor vehicles are increasing in number year after year. As the population increases, the vehicles also increase in number. A phenomenal growth has occurred in recent decades in our country in the automobile industry. Every family likes to own at least a two-wheeler. The demand is increasing forever. This phenomenal growth has certain disadvantages too. It increases the demand for fossil fuels which leads to great burden in terms of foreign exchange resources. As well it depletes the non-renewable resource – fossil fuels and it spews unprecedented amounts of air pollutants into the atmosphere causing air pollution.



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The increase in vehicles also lead to more number of road accidents and many of them are fatal. Hence, it becomes essential to set norms while issuing the driving licence and registering the vehicles.

25.2 CHAPTER I - PRELIMINARY The motor vehicles act enacted by the Government of India is described as follows:

THE MOTOR VEHICLES ACT, 1988 NO. 59 OF 1988

[14th October, 1988.]

PRELIMINARY

Short title, extent and commencement (1) This Act may be called the Motor Vehicles Act, 1988.

(2) It extends to the whole of India.

(3) It shall come into force on such date as the Central Government may, by notification in the Official Gazette, appoint; and different dates may be appointed for different State and any reference in this Act to the commencement of this Act shall, in relation to a State, be construed as a reference to the coming into force of this Act in that State.

Self-check Exercise 10 Write the short title of the Act. State whether this act is applicable to whole India or only in certain States. Note: Please do not proceed unless you write answers for the above two in the space given below:

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Definitions In this Act, unless the context otherwise requires –

(1) "articulated vehicle" means a motor vehicle to which a semi trailer is attached;

(2) "certificate of registration" means the certificate issued by a competent authority to the effect that a motor vehicle has been duly registered in accordance with the provisions of Chapter IV;



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(3) "driver" includes, in relation to a motor vehicle which is drawn by another motor vehicle, the person who acts as a steersman of the drawn vehicle;

(4) "driving licence" means the licence issued by a competent authority under Chapter II authorising the person specified therein to drive, otherwise than as a learner, a motor vehicle or a motor vehicle of any specified class or description;

(5) "fares" includes sums payable for a season ticket or in respect of the hire of a contract carriage;

(6) "owner" means a person in whose name a motor vehicle stands registered, and where such person is a minor, the guardian of such minor, and in relation to a motor vehicle which is the subject of a hire-purchase, agreement, or an agreement of lease or an agreement of hypothecation, the person in possession of the vehicle under that agreement;

(7) "permit" means a permit issued by a State or Regional Transport Authority or an authority prescribed in this behalf under this Act authorising the use of a motor vehicle as a transport vehicle;

(8) "prescribed" means prescribed by rules made under this Act;

(9) "registering authority" means an authority empowered to register motor vehicles under Chapter IV;

(10) "route" means a line of travel which specifies the highway which may be traversed by a motor vehicle between one terminus and another

(11) "traffic signs" includes all signals, warning sign posts, direction posts, markings on the road or other devices for the information, guidance or direction of drivers of motor vehicles;

Self-check Exercise 11 Define the following:

1. Driving license 2. Certificate of registration 3. Traffic signs


……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

25.3 LICENSING OF DRIVERS OF MOTOR VEHICLES - NECESSITY FOR DRIVING LICENSE (SECTION 3)



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(1) No person shall drive a motor vehicle in any public place unless he holds an

effective driving license issued to him authorizing him to drive the vehicle; and no person shall so drive a transport vehicle [other than a motor cab hired for his own use or rented under any scheme made under sub-section (2) of section 75] unless his driving license specifically entitles him so to do.

(2) The conditions subject to which sub-section (1) shall not apply to a person receiving instructions in driving a motor vehicle shall be such as may be prescribed by the Central Government.

Age limit in connection with driving of motor vehicles (Section 4) (1) No person under the age of eighteen years shall drive a motor vehicle in any

public place:

Provided that a motor cycle without gear may be driven in a public place by a person after attaining the age of sixteen years.

(2) Subject to the provisions of section 18, no person under the age of twenty years shall drive a transport vehicle in any public place.

(3) No learner's license or driving license shall be issued to any person to drive a vehicle of the class to which he has made an application unless he is eligible to drive that class of vehicle under this section.

Section 5: Responsibility of owners of motor vehicles for contravention of sections 3 and 4. No owner or person in charge of a motor vehicle shall cause or permit any person who does not satisfy the provisions of section 3 or section 4 to drive the vehicle.

Self-check Exercise 12 Under what conditions can a person not be permitted to drive a motor vehicle? Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

25.3.1 GRANT OF LEARNER'S LICENSE (1) Any person who is not disqualified under section 4 for driving a motor

vehicle and who is not for the time being disqualified for holding or



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obtaining a driving license may, subject to the provisions of section 7, apply to the licensing authority having jurisdiction in the area –

(i) in which he ordinarily resides or carries on business, or (ii) in which the school or establishment referred to in section 12 from

where he intends to receive instruction in driving a motor vehicle is situate, for the issue to him of a learner's licence.

(2) Every application under sub-section (1) shall be in such form and shall be accompanied by such documents and with such fee as may be prescribed by the Central Government.

(3) Every application under sub-section (1) shall be accompanied by a medical certificate in such form as may be prescribed by the Central Government and signed by such registered medical practitioner, the State Government or any person authorized in this behalf by the State Government may, by notification in the Official Gazette, appoint for this purpose.

(4) If, from the application or from the medical certificate referred to in sub-section (3), it appears that the applicant is suffering from any disease or disability which is likely to cause the driving by him of a motor vehicle of the class which he would be authorized by the learner's license applied for to drive to be a source of danger to the public or to the passengers, the licensing authority shall refuse to issue the learner's license:

Provided that a learner's license limited to driving an invalid carriage may be issued to the applicant, if the licensing authority is satisfied that he is fit to drive such a carriage.

(5) No learner’s license shall be issued to any applicant unless he passes to the satisfaction of the licensing authority such test as may be prescribed by the Central Government.

(6) When an application has been duly made to the appropriate licensing authority and the applicant has satisfied such authority of his physical fitness under sub-section (3) and has passed to the satisfaction of the licensing authority the test referred to in sub-section (5), the licensing authority shall, subject to the provisions of section 7, issue the applicant a learner's license unless the applicant is disqualified under section 4 for driving a motor vehicle or is for the time being disqualified for holding or obtaining a license to drive a motor vehicle:

Provided that a licensing authority may issue a learner's licence to drive a motor cycle or a light motor vehicle notwithstanding that it is not the appropriate licensing authority, if such authority is satisfied that there is good reason for the applicant's inability to apply to the appropriate licensing authority.

(7) Where the Central Government is satisfied that it is necessary or expedient so to do, it may, by rules made in this behalf, generally, either absolutely or subject to such conditions as may be specified in the rules, any class of persons from the provisions of sub-section (3), or sub-section (5), or both.



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(8) Any learner's license for driving a motor cycle in force immediately before the commencement of this Act shall, after such commencement, be deemed to be effective for driving a motor cycle with or without gear

25.3.2 GRANT OF DRIVING LICENSE (9) Any person who is not for the time being disqualified for holding or

obtaining a driving license may apply to the licensing authority having jurisdiction in the area –

(i) in which he ordinarily resides or carries on business, or (ii) in which the school or establishment referred to in section 12 from

where he is receiving or has received instruction in driving a motor vehicle is situated, for the issue to him of a driving license.

(10) Every application under sub-section (1) shall be in such form and shall be accompanied by such fee and such documents as may be prescribed by the Central Government.

(11) No driving license shall be issued to any applicant unless he passes to the satisfaction of the licensing authority such test of competence to drive as may be prescribed by the Central Government:

Provided that, where the application is for a driving license to drive a motor cycle or a light motor vehicle, the licensing authority shall exempt the applicant from the test of competence prescribed under this sub-section, if the licensing authority is satisfied –

(a) (i) that the applicant has previously held a driving license and that the period between the date of expiry of that license and the date of such application does not exceed five years; or

(ii) that the applicant holds or has previously held a driving license issued under section 18; or

(iii) that the applicant holds a driving license issued by a competent authority of any country outside India; and

(b) that the applicant is not suffering from any disease or disability which is likely to cause the driving by him of a motor cycle or, as the case may be, a light motor vehicle to be a source of danger to the public; and the licensing authority may for that purpose require the applicant to produce a medical certificate in the same form and in the same manner as is referred to in sub-section (3) of section 8:

Provided further that where the application is for a driving license to drive a motor vehicle (not being a transport vehicle), the licensing authority may exempt the applicant from the test of competence to drive prescribed under this sub-section, if the applicant possesses a driving certificate issued by an automobile association recognized in this behalf by the State Government

(12) Where the application is for a license to drive a transport vehicle, no such authorization shall be granted to any applicant unless he possesses such minimum educational qualification as may be prescribed by the Central Government and a driving certificate issued by a school or establishment referred to in section 12.



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(13) Where the applicant does not pass to the satisfaction of the licensing authority the test of competence to drive under sub-section (3), he shall not be qualified to re-appear for such test –

(a) in the case of first three such tests, before a period of one month from the date of last such test; and

(b) in the case of such test after the first three tests, before a period of one year from the date of last such test.

(14) The test of competence to drive shall be carried out in a vehicle of the type to which the application refers:

Provided that a person who passed a test in driving a motor cycle with gear shall be deemed also to have passed a test in driving a motor cycle without gear.

(15) When any application has been duly made to the appropriate licensing authority and the applicant has satisfied such authority of his competence to drive, the licensing authority shall issue the applicant a driving licence unless the applicant is for the time being disqualified for holding or obtaining a driving licence:

Provided that a licensing authority may issue a driving licence to drive a motor cycle or a light motor vehicle notwithstanding that it is not the appropriate licensing authority, if the licensing authority is satisfied that there is good and sufficient reason for the applicant's inability to apply to the appropriate licensing authority:

Provided further that the licensing authority shall not issue a new driving license to the applicant, if he had previously held a driving licence, unless it is satisfied that there is good and sufficient reason for his inability to obtain a duplicate copy of his former licence.

(16) If the licensing authority is satisfied, after giving the applicant an opportunity of being heard, that he –

(a) is a habitual criminal or a habitual drunkard; or (b) is a habitual addict to any narcotic drug or psychotropic substance

within the meaning of the Narcotic Drugs and Psychotropic Substances Act, 1985; (61 of 1985.) or

(c) is a person whose license to drive any motor vehicle has, at any time earlier, been revoked, it may, for reasons to be recorded tin writing, make an order refusing to issue a driving licence to such person and any person aggrieved by an order made by a licensing authority under this sub-section may, within thirty days of the receipt of the order, appeal to the prescribed authority.

(17) Any driving license for driving a motor cycle in force immediately before the commencement of this Act shall, after such commencement, be deemed to be effective for driving a motor cycle with or without gear.

Self-check Exercise 13 Under what conditions can a person be exempted from the test of competence?



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25.3.3 POWER OF LICENSING AUTHORITY TO DISQUALIFY FROM HOLDING A DRIVING LICENSE OR REVOKE SUCH LICENSE

. (1) If a licensing authority is satisfied, after giving the holder of a driving

license an opportunity of being heard, that he – (a) is a habitual criminal or a habitual drunkard; or (b) is a habitual addict to any narcotic drug or psychotropic substance

within the meaning of the Narcotic Drugs and Psychotropic Substances Act, 1985; (61 of 1985.) or

(c) is using or has used a motor vehicle in the commission of a cognizable offence; or

(d) has by his previous conduct as driver of a motor vehicle shown that his driving is likely to be attended with danger to the public; or

(e) has obtained any driving license or a license to drive a particular class or description of motor vehicle by fraud or misrepresentation; or

(f) has committed any such act which is likely to cause nuisance or danger to the public, as may be prescribed by the Central Government, having regard to the objects of this Act; or

(g) has failed to submit to, or has not passed, the tests referred to in the proviso to sub-section (3) of section 22; or

(h) being a person under the age of eighteen years who has been granted a learner's license or a driving license with the consent in writing of the person having the care of the holder of the license and has ceased to be in such care, it may, for reasons to be recorded in writing, make an order –

(i) disqualifying that person for a specified period for holding or obtaining any driving license to drive all or any classes or descriptions of vehicles specified in the license; or

(ii) revoke any such license.

(2) Where an order under sub-section (1) is made, the holder of a driving licence shall forthwith surrender his driving license to the licensing authority making the order, if the driving license has not already been surrendered, and the licensing authority shall –

(a) if the driving license is a driving license issued under this Act, keep it until the disqualification has expired or has been removed; or



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(b) if it is not a driving license issued under this Act, endorse the disqualification upon it and send it to the licensing authority by which it was issued; or

(c) in the case of revocation of any license, endorse the revocation upon it and if it is not the authority which issued the same, intimate the fact of revocation to the authority which issued that license:

Provided that where the driving license of a person authorizes him to drive more than one class or description of motor vehicles and the order, made under sub-section (1), disqualifies him from driving any specified class or description of motor vehicles, the licensing authority shall endorse the disqualification upon the driving license and return the same to the holder.

(3) Any person aggrieved by an order made by a licensing authority under sub-section (1) may, within thirty days of the receipt of the order, appeal to the prescribed authority, and such appellate authority shall give notice to the licensing authority and hear either party if so required by that party and may pass such order as it thinks fit and an order passed by any such appellate authority shall be final.

Self-check Exercise 14 List out the reasons for disqualifying a driving license. Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

25.4 POWER OF CENTRAL GOVERNMENT TO MAKE RULES The Central Government may make rules – (a) regarding conditions referred to in sub-section (2) of section 3; (b) providing for the form in which the application for learner's licence may

be made, the information it shall contain and the documents to be submitted with the application referred to in sub-section (2) of section 8;

(c) providing for the form of medical certificate referred to in sub-section (3) of section 8;

(d) providing for the particulars for the test referred to in sub-section (5) of section 8;

(e) providing for the form in which the application for driving licence may be made, the information it shall contain and the documents to be submitted with the application referred to in sub-section (2) of section 9;

(f) providing for the particulars regarding test of competence to drive, referred to in sub-section (3) of section 9;



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(g) specifying the minimum educational qualifications of persons to whom licenses to drive transport vehicles may be issued under this Act and the time within which such qualifications are to be acquired by such persons;

(h) providing for the form and contents of the licences referred to in sub-section (1) of section 10;

(i) providing for the form and contents of the application referred to in sub-section (1) of section 11 and documents to be submitted with the application and the fee to be charged;

(j) providing for the conditions subject to which section 9 shall apply to an application made under section 11;

(k) providing for the form and contents of the application referred to in sub-section (1) of section 15 and the documents to accompany such application under sub-section (2) of section 15;

(l) providing for the authority to grant licenses under sub-section (1) of section 18;

(m) specifying the fees payable under sub-section (2) of section 8, sub-section (2) of section 9 and sub-sections (3) and (4) of section 15 for the grant of learner's licenses, and for the grant and renewal of driving licenses and licenses for the purpose of regulating the schools or establishment for imparting instructions in driving motor vehicles;

(n) specifying the acts for the purposes of clause (f) of sub-section (1) of section 19;

(o) specifying the offences under this Act for the purposes of sub-section (2) of section 24;

(p) to provide for all or any of the matters referred to in sub-section (1) of section 26;

(q) any other matter which is, or has to be, prescribed by the Central Government. 25.5 POWER OF STATE GOVERNMENT TO MAKE RULES (1) A State Government may make rules for the purpose of carrying into effect

the provisions of this Chapter other than the matters specified in section 27.

(2) Without prejudice to the generality of the foregoing power, rules may provide for –

(a) the appointment, jurisdiction, control and functions of licensing authorities and other prescribed authorities;

(b) the conduct and hearing of appeals that may be preferred under this Chapter, the fees to be paid in respect of such appeals and the refund of such fees: Provided that no fee so fixed shall exceed twenty-five rupees;

(c) the issue of duplicate licences to replace licences lost, destroyed or mutilated, the replacement of photographs which have become obsolete and the fees to be charged therefor;

(d) the badges and uniform to be worn by drivers of transport vehicles and the fees to be paid in respect of badges;



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(e) the fee payable for the issue of a medical certificate under sub-section (3) of section 8;

(f) the exemption of prescribed persons, or prescribed classes of persons, from payment of all or any portion of the fees payable under this Chapter;

(g) the communication of particulars of licences granted by one licensing authority to other licensing authorities;

(h) the duties, functions and conduct of such persons to whom licences to drive transport vehicles are issued;

(i) the exemption of drivers of road-rollers from all or any of the provisions of this Chapter or of the rules made thereunder;

(j) the manner in which the State Register of Driving Licences shall be maintained under section 26;

(k) any other matter which is to be, or may be, prescribed. 25.6 LIABILITY WITHOUT FAULT IN CERTAIN CASES Liability to pay compensation in certain cases on the principle of no fault: (1) Where death or permanent disablement of any person has resulted from an

accident arising out of the use of a motor vehicle or motor vehicles, the owner of the vehicle shall, or, as the case may be, the owners of the vehicles shall, jointly and severally, be liable to pay compensation in respect of such death or disablement in accordance with the provisions of this section.

(2) The amount of compensation which shall be payable under sub-section (1) in respect of the death of any person shall be a fixed sum of twenty-five thousand rupees and the amount of compensation payable under that sub-section in respect of the permanent disablement of any person shall be a fixed sum of twelve thousand rupees.

(3) In any claim for compensation under sub-section (1), the claimant shall not be required to plead and establish that the death or permanent disablement in respect of which the claim has been made was due to any wrongful act, neglect or default of the owner or owners of the vehicle or vehicles concerned or of any other person.

(4) A claim for compensation under sub-section (1) shall not be defeated by reason of any wrongful act, neglect or default of the person in respect of whose death or permanent disablement the claim has been made nor shall the quantum of compensation recoverable in respect of such death or permanent disablement be reduced on the basis of the share of such person in the responsibility for such death or permanent disablement.

25.7 OFFENCES, PENALTIES AND PROCEDURE General provision for punishment of offences:



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Whoever contravenes any provision of this Act or of any rule, regulation or notification made thereunder shall, if no penalty is provided for the offence be punishable for the first offence with fine which may extend to one hundred rupees, and for any second or subsequent offence with fine which may extend to three hundred rupees.

Penalty for traveling without pass or ticket and for dereliction of duty on the part of

conductor and refusal to ply contract carriage, etc. (1) Whoever travels in a stage carriage without having a proper pass or ticket

with him or being in or having alighted from a stage carriage fails or refuses to present for examination or to deliver up his pass or ticket immediately on a requisition being made therefore, shall be punishable with fine which may extend to five hundred rupees. Explanation.-- In this section, "pass" and "ticket" have the meanings respectively assigned to them in section 124.

(2) the functions of a conductor in such stage carriage, whose duty is – (a) to supply a ticket to a person travelling in a stage carriage on

payment of fare by such person, either wilfully or negligently – (i) fails or refuses to accept the fare when tendered, or (ii) fails or refuses to supply a ticket, or (iii) supplies an invalid ticket, or (iv) supplies a ticket of a lesser value, or

(b) to check any pass or ticket, either wilfully or negligently fails or refuses to do so, he shall be punishable with fine which may extend to five hundred rupees.

(3) If the holder of a permit or the driver of a contract carriage refuses, in contravention of the provisions of this Act or rules made thereunder, to ply the contract carriage or to carry the passengers, he shall –

(a) in the case of two-wheeled or three-wheeled motor vehicles, be punishable with fine which may extend to fifty rupees; and

(b) in any other case, be punishable with fine which may extend to two hundred rupees.

Self-check Exercise 15 What is the penalty for a person traveling in a stage carriage without pass or ticket? Note: Please do not proceed unless you write answers for the above two in the space given below: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Power to arrest without warrant:



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(1) A police officer in uniform may arrest without warrant any person who in

his presence commits an offence punishable under section 184 or section 185 or section 197:

Provided that any person so arrested in connection with an offence punishable under section 185 shall, within two hours of his arrest, be subjected to a medical examination referred to in sections 203 and 204 by a registered medical practitioner failing which he shall be released from custody.

(2) A police officer in uniform may arrest without warrant – (a) any person who being required under the provisions of this Act to

give his name and address refuses to do so, or gives a name or address which the police officer has reason to believe to be false, or

(b) any person concerned in an offence under this Act or reasonably suspected in have been so concerned if the police officer has reason to believe that he will abscond or otherwise avoid the service of a summons.

(3) A police officer arresting without warrant the driver of a motor vehicle shall if the circumstances so require take or cause to be taken any steps he may consider proper for the temporary disposal of the vehicle

Courts to send intimation about conviction: Every Court by which any person holding a driving licence is convicted of an

offence under this Act or of an offence in the commission of which a motor vehicle was used, shall send intimation to –

(a) the licensing authority which issued the driving licence, and (b) the licensing authority by whom the licence was last renewed, and every

such intimation shall state the name and address of the holder of the licence, the licence number, the date of issue and renewal of the same, the nature of the offence, punishment awarded for the same and such other particulars as may be prescribed.

(1) of section 112 and sub-section (4) of section 213 shall be laid, as soon as

may be after it is made, before each House of Parliament while it is in session for a total period of thirty days which may be comprised in one session or in two or more successive sessions, and if, before the expiry of the session immediately following the session or the successive sessions aforesaid, both Houses agree in making any modification in the rule, scheme or notification or both Houses agree that the rule or scheme should not be made or the notification should not be issued, the rule, scheme or notification shall thereafter have effect only in such modified form or be of no effect, as the case may be; so, however, that any such modification or annulment shall be without prejudice to the validity of anything previously done under that rule, scheme or notification



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25.8 CHAPTER VII – CONSTRUCTION, EQUIPMENT AND MAINTENANCE OF MOTOR VEHICLES

109. General provision regarding construction and maintenance of vehicles- (1) Every motor vehicle shall be so constructed and so maintained as to be at all times under the effective control of the person driving the vehicle. (2) Every motor vehicle shall be so constructed as to have right hand steering control unless it is equipped with a mechanical or electrical signaling device of a prescribed nature. +1[(3) If the Central Government is of the opinion that it is necessary or expedient so to do, in public interest, it may by order published in the Official Gazette, notify that any article or process used by a manufacturer shall confirm to such standard as may be specified in that order.] 110. Power of Central Government to make rules - (1) The Central Government may make rules regulating the construction, equipment and maintenance of motor vehicles and trailers with respect to all or any of the following matters, namely- (a) the width, height, length and overhand of vehicles and of the loads carried; (b) the size, nature, maximum retail price and condition of tyres, including embossing thereon of date and year of manufacture, and the maximum load carrying capacity.] (c) brakes and steering gear; (d) the use of safety glasses including prohibition of the use of tinted safety glasses; (e) signaling appliances, lamps and reflectors; (f) speed governors; (g) the emission of smoke, visible vapour, sparks, ashes, grit or oil; (h) the reduction of noise emitted by or caused by vehicles; (i) the embossment of chassis number and engine number and the date of manufacture; (j) safety belts, handle bars of motor cycles, auto-dippers and other equipment essential for safety of drivers, passengers and other road users; (k) standards of the components used in the vehicle as inbuilt safety devices; (l) provision for transportation of goods of dangerous of hazardous nature to human life; (m) standards for emission of air pollutants: 2[(n) installation of catalytic converters in the class of vehicles to be prescribed; (o) the placement of audio-visual or radio or tape recorder type of devices in public vehicles; (p) warranty after sale of vehicle and norms therefor.] Provided that any rules relating to the matters dealing with the protection of environment, so far as may be, shall be made after consultation with the Ministry of the Government of India dealing with environment.



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(2) Rules may be made under sub-section (1) government the matters mentioned therein, including the manner of ensuring the compliance with such matter and the maintenance of motor vehicles in respect if such matters, either generally in respect of motor vehicles or trailers or in respect of motor vehicles or trailers of a particular class or in particular circumstances. (3) Notwithstanding anything contained in this section,- (a) the Central Government may exempt any class of motor vehicles from the provisions of this Chapter; (b) a State Government may exempt any motor vehicle or any class or description of motor vehicles from the rules made under sub-section (1) subject to such conditions as may be prescribed by the Central Government. 111. Power of State Government to make rules- (1) A state Government may make rules regulating the construction, equipment and maintenance of motor vehicles and trailers with respect to all matters other than the matters specified in sub-section (1) of section 110. (2) Without prejudice to the generality of the forgoing power, rules may be made under this section government all or any the following matters either generally in respect of motor vehicles or trailers or in respect of motor vehicles or trailers of a particular class or in particular, namely- (a) seating arrangements in public service vehicles and the protection of passengers against the weather; (b) prohibiting or restricting the use of audible signals at certain times or in certain places; (c) prohibiting the carrying of appliances likely to cause annoyance or danger; (d) the periodical testing and inspection of vehicles by prescribed authorities 1[and fees to be charged for such test]; (e) the particulars other than registration marks to be exhibited by vehicles and the manner in which they shall be exhibited; (f) the use of trailers with motor vehicles; and (g) 2[* * * * *]

Self-check Exercise 16 What does Section 110 spell about environmental protection? Explain. Note: Please do not proceed unless you write answers for the above two in the space given below: ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….



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25.9 LET US SUM UP

In this lesson, we have learned the provisions of the Motor Vehicles Act, 1988. We understood the necessity for holding a driving licence and eligibility for obtaining the licence. We also learned the conditions under which the driving licence could be disqualified. We came to know the penalties and punishments prescribed for the offenders, and defaulters under this Act. We also learnt that the Act gives importance to environmental protection in terms of installing the catalytic converters and emission checking. 25.10 LESSON END ACTIVITIES

· If you are holding a driving license, go through the terms and conditions printed on the license

· If you are owning a vehicle go through the terms conditions printed on registration certificate book

· Take a sheet of paper and write down 25.11 POINTS FOR DISCUSSION

· Need for driving license · Need for registration of vehicle · Provision in the Act for environmental protection


· Can you describe the offences and penalties? · Can you describe the provisions of this Act for environmental protection?

25.13 REFERENCES



3. www.envfor.nic.in/legis 4. www.india.gov.in



http://www.india.gov.in/


msc_air.pdf

Documents

john wiley

narosa publishing

ethylene diamine

environmental

ammonium phosphate

respirable

real green

suspended