Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 1/23

Unit 1: a. Introduction

The term environment is drawn from French language which means surroundings. As

such it is being defined as the surroundings in which an organism lives, including air, water, land,

natural resources, flora, fauna, humans, and their interrelations. This definition extends the viewfrom the focus of an organism to the global system.

The study of such environment (all systems of air, land, water and energy systems in

relation to life systems) is called environmental studies & the relevant branch is called

environmental science(s).

Through various studies related to environment (environmental studies) we couldunderstand & realize that our environment is getting degraded due to increasing population

coupled with unplanned technological revolutions, pollution, toxification, acidification,

desertification, deforestation, loss of biodiversity, global warming, depletion of ozone layer,resource depletion, etc. making life miserable. This necessitated a need to incorporate an

environmental concern in our technological inventions and innovations to eliminate or at leastminimize their adverse impact on the environment. Such part of the technology is called

‘environmental technology’ which can be defined as the development of technology to combatadverse effects on environment .

Basic Subdivisions of Environmental Science:

Basic subdivisions of environmental science includes

a. Environmental analysis – analysis of the environment into its basic four components viz, atmosphere,

hydrosphere, lithosphere and biosphere.

b. Ecosystem analysis – deals with the structure and function of ecosystems making the biosphere.

c. Population biology – deals with intra as well as interspecific interactions of populations.

d. Comunity studies – concerned with the composition, structure, distribution and dynamics of communities

of ecosystems.

e. Environmental degradations – study of various factors responsible for environmental degradation.

Studies include pollution, toxic agents, desertification, deforestation etc.

f. Conservation of biodiversity – study of natural resources and wildlife, and the scientific way of their 

conservation and management.

g. Environmental monitoring, impact assessment and development – studies are designed for repeated and

regular observations on status of chemical, physical and biological factors of the environment.

This includes chemical monitoring for various chemicals in the environment as well as

 biomonitoring for changes in the life forms in different ecosystems with a view to assess risk due

to pollution. There are also studies undertaken on risk assessment, safety evaluation andsustainable development.

h. Environmental legislation and education – this is concerned with creating awareness in general public for 

environmental problems around them through formal and informal education. Recommendations

may also be made to the State for any legislation in order to protect the deterioration of quality of 

life and the environment.

1

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 2/23

Atmosphere

Biosphere

Lithospher 

e

Hydrosphere

1.1 Components of environment:

There are two types of components of environment.

1. Non-living physical components of the environment which comprise the Atmosphere

(air), Hydrosphere (water) and Lithosphere (land).2. Living or biological component is biosphere which includes plants, animals and other 

organisms.

The environment of an organism therefore, includes (i) Atmosphere, (ii) Hydrosphere, (iii)

Lithosphere and (iv) Biosphere.

1.1.1 Atmosphere: An atmosphere is a layer of gases that may surround the earth.

Importance of atmosphere: The atmosphere protects life on Earth by absorbing ultraviolet solar  radiation, warming the surface through heat retention (greenhouse effect), and reducingtemperature extremes between day and night (the diurnal temperature variation). It contains

oxygen and carbon dioxide used in  breathing and photosynthesis – vital bioprocesses. The

Atmosphere is a prime mean for the spatial diffusion of pollutants and a temporary mean of their accumulation.

Composition of Earths atmosphere: Dry air contains roughly (by volume) 78.09% nitrogen,20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also

contains a variable amount of  water vapor , on average around 1%. Although the atmosphere is

approximately 1,100 km high, the stratosphere (10 to 50 km) and the Troposphere (less than 10

km) are the main Atmospheric interactors of the Biosphere.

Structure of Atmosphere: The atmosphere consists of almost concentric layers of air with

varying density and temperature. Density is highest on the earth’s surface and decreases rapidlyupwards. In the atmosphere, broadly five layers can be identified. They are,

• Troposphere: from the surface to 8km (near the poles) to 18 km (near the equator).

2

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 3/23

o Tropo means change or turning which refers to the action of the winds which keeps

the troposphere in constant motion. Almost all changes in our daily weather occur 

in this layer of atmosphere.o Air temperature in this sphere gradually decreases with height.

o Important zone for organisms and is composed of different gases.

•

Stratosphere: from that 18 km range to about 50 km,o Temperature raises with increase in height (from a minimum of about -550C to a

minimum of 50C).

o It has no clouds ,dust or water vapours

o It is rich in ozone, which absorbs harmful UV radiations from the sun.

• Mesosphere: from about 50 km to the range of 80 km to 85 km.

o Temperature decreases with height.

o It is characterized by low temperature with low pressure

o It has various gases like N2, O2+, NO+

• Thermosphere or Ionosphere: from 80–85 km to 640+ km.

o Temperature increasing with height

o Most of the gaseous components such as O2, O+, NO+ are ionized under theinfluence of radiant energy and so contains electrically charged particles.

o These particles reflect radio waves back to the earth surface and enable us to have

wireless communications.

• Exosphere: above the ionosphere, where the atmosphere thins out into space

The boundaries between these regions are named the Tropopause, Stratopause and Mesopause.

The structure of the atmosphere.

Ozone layer or ozonosphere is found in stratosphere, approximately at 10 - 50 km height.

The average temperature of the atmosphere at the surface of earth is 14 °C.

3

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 4/23

1.1.2 The lithosphere:

The Earth is made of Earth’s Crust, Mantle and the Core. In the centre of the earth is the core

which, is surrounded by the mantle. Lithosphere is the thin crust between the mantle and the

atmosphere. Together the crust and upper mantle are called the lithosphere and extends upto a

depth of about 80 -100 km.

Earths crust: The crust, the outermost layer, is rigid and very thin compared with the other two. Beneath

the oceans, the crust varies little in thickness, generally extending only to about 5 km. The thickness of the

crust beneath continents is much more variable but averages about 30 km.Earths mantle:Below the crust is the mantle, a dense, hot layer of semi-solid rock approximately 2,900 km

thick. The mantle, which contains more iron, magnesium, and calcium than the crust, is hotter and denser 

 because temperature and pressure inside the Earth increase with depth.Earths core:Is nearly twice as dense as the mantle because its composition is metallic (iron-nickel alloy)

rather than stony. It is actually made up of two distinct parts: a 2,200 km-thick liquid outer core and a 1,250

km-thick solid inner core. As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic

field.

Asthenosphere: At least 80 km in thickness over much of the Earth, the lithosphere has been broken up

into the moving plates that contain the world's continents and oceans. Below the lithosphere is a relatively

narrow, mobile zone in the mantle called the asthenosphere (from asthenes, Greek for weak). This zone iscomposed of hot, semi-solid material, which can soften and flow after being subjected to high temperature

and pressure over geologic time. The rigid lithosphere is thought to "float" or move about on the slowly

flowing asthenosphere.

Although the lithosphere is around 100 km thick, only 1 km of it can be considered in interaction

with the biosphere. Main constituents are oxygen (47%), silicon (28%), aluminum (8%), iron (5%),

4

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 5/23

calcium (4%), sodium (3%), potassium (3%) and magnesium (2%) in a crystalline state. The

lithosphere is the main source of pollutants and a permanent accumulator. Some are naturally

released through sources like volcanic eruptions, while others like fossil fuels are the result of artificial extraction and combustion.

1.1.3 Hydrosphere:

The planetary water supply is dominated by the oceans (see Table 8b-1). Approximately 97% of all

the water on the Earth is in the oceans. The other 3% is held as freshwater in glaciers and icecaps,groundwater, lakes, soil, the atmosphere, and within life.

Water moves from one reservoir to another by way of processes like evaporation, condensation,

precipitation, deposition, runoff , infiltration, sublimation, transpiration, melting, and groundwater flow. Theoceans supply most of the evaporated water found in the atmosphere. Of this evaporated water,only 91% of it is returned to the ocean basins by way of precipitation. The remaining 9% is

transported to areas over landmasses where climatological factors induce the formation of 

 precipitation. The resulting imbalance between rates of evaporation and precipitation over land andocean is corrected by runoff and groundwater flow to the oceans.

Reservoir Percent of Total

Oceans 97.25

Ice Caps and Glaciers 2.05

Groundwater 0.68

Lakes 0.01

Soil Moisture 0.005

Atmosphere 0.001

Streams and Rivers 0.0001

5

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 6/23

Biosphere 0.00004

1.1.4 The Biosphere: 

The term "Biosphere" was coined by geologist Eduard Suess in 1875, which he defined as The

 place on earth's surface where life dwells.

The biosphere is the part of the earth including air, land, surface rocks and water within which life

occur. From the broadest biophysiological point of view, the biosphere is the global ecological

system integrating all living beings and their relationships, including their interaction with the

elements of the lithosphere, hydrosphere, and atmosphere. This biosphere is postulated to have

evolved, beginning through a process of biogenesis or biopoesis, at least some 3.5 billion yearsago.

Biomass accounts for about 3.7 kg carbon per square metre of the earth's surface averaged over 

land and sea, making a total of about 1900 gigatonnes of carbon.

The biosphere is structured into a hierarchy known as the food chain whereby all life is dependent

upon the first tier (i.e. mainly the primary producers that are capable of photosynthesis). Energy

and mass is transferred from one level of the food chain to the next with an efficiency of about10%. The biosphere can be divided into distinct ecosystems that represent the interactions between

a group of organisms forming a trophic pyramid and the environment or habitat in which they live.

The Energy Pyramid

1.1.5 Anthroposystems:

6

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 7/23

Anthroposystems are all natural or artificial systems which are or have been subject to human

intervention either through exploitation or development. These systems, which are typically made

up of interacting physical, chemical, biological, ecological and human components that becomeapparent and evolve according to different time and space scales.

1.2 Energy flow and ecosystem:

Ecosystems: Ecosystems are functional units that result from the interactions of abiotic & biotic

components at a particular area with in the environment. Like all other  systems they are acombination of interacting processes within biotic components & between biotic & abiotic

components. Ecosystems may be micro-ecosystem (as small as a drop of water) or macro-

ecosystem (as large as ocean). It may be either temporary (eg: field of cultivated crops) or  permanent (eg: a forest or ocean). The boundaries are not fixed in any objective way, although

sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundariesof an ecosystem are chosen for practical reasons having to do with the goals of the

particular study.

The study of ecosystems (ecosystem ecology) mainly consists of the -

• Studies of certain processes that link the living, or biotic, components to the non-living, or abiotic,components & are Energy transformations and biogeochemical cycling .

• Studies of  individuals are concerned mostly about physiology, reproduction, development or

behavior,

• studies of  populations usually focus on the habitat and resource needs of individual species, their

group behaviors, population growth, and what limits their abundance or causes extinction.

• Studies of communities examine how populations of many species interact with one another, such

as predators and their prey, or competitors that share common needs or resources. Hence the study of ecosystems includes studying all of this putting together, sofar as we can, to

understand how the ecosystem operates as a whole (as a system). i.e. rather than worrying mainly about

 particular species, the focus will be on major functional aspects of the system. These  functional aspectsinclude such things as how energy or materials flow along the many steps in a food chain, the amount of 

energy that is produced by photosynthesis, or what controls the rate of decomposition of materials or the

rate at which nutrients are recycled in the system.

Components of an EcosystemIt is a basic understanding of the diversity of plants and animals, and how plants and animals and

microbes obtain water, nutrients, and food. We can clarify the parts of an ecosystem by listing them under 

the headings "abiotic" and "biotic".

Abiotic Components: Structurally abiotic components include:

• Physical factors such as light, temperature, precipitation, humidity, wind, soil, etc

• Inorganic substances include minerals and gases.

• Organic substances such as carbohydrates, proteins , lipids and humans

Biotic Components: They include the entire living organisms. They may be divided into two groups.

• Autotrophs or producers: They are self nourishing green plants and certain photosynthetic or 

chemosynthetic bacteria which conert the light energy into chemical energy in the form of organic

compounds needed by the plants for their growth and development.

7

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 8/23

• Heterotrophs or Consumers: Organisms which feed directly or indirectly on producers are called

consumers. An organism that feed upon the producers is called primary consumer or herbivores and

the organisms which feed on the primary consumer is called a secondary consumer or carnivore.Animals that feed both on plants and animals are known as omnivores.

Structure of an Ecosystem:

• The particular pattern of interrelationship that exists between the components in an ecosystem is the

structure of the ecosystem.

• The structure of the ecosystem may be determined by a single abiotic factor known as limiting factor.

For most of the land areas, the amount of rainfall is the limiting factor which is responsible for the

categorization of the ecosystem into forests, grasslands or deserts. Energy flow and nutrient cycling

can only occur as long as certain structure is maintained.

 Processes of Ecosystems

Ecosystems function through two important and interlinked processes & are energy flow &

material cycling. Energy flow is the movement of energy, starting with the sun, and passing from

one organism to another. Energy enters the biological system as light energy, or photons, istransformed into chemical energy in organic molecules by cellular processes including

 photosynthesis and respiration, and ultimately is converted to heat energy. This energy is

dissipated, meaning it is lost to the system as heat; once it is lost it cannot be recycled. Without thecontinued input of solar energy, biological systems would quickly shut down. Thus the earth is an

open system with respect to energy.

Elements such as carbon, nitrogen, or phosphorus enter living organisms in a variety of 

ways. Plants obtain elements from the surrounding atmosphere, water, or soils. Animals may alsoobtain elements directly from the physical environment, but usually they obtain these mainly as a

consequence of consuming other organisms. These materials are transformed biochemically within

the bodies of organisms, but sooner or later, due to excretion or decomposition, they are returnedto an inorganic state. Often bacteria complete this process, through the process called

decomposition or mineralization. During decomposition these materials are not destroyed or lost,

so the earth is a closed system with respect to elements (with the exception of a meteorite enteringthe system now and then). The elements are cycled endlessly between their biotic and abiotic states

within ecosystems.

8

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 9/23

The diagram above shows how both energy and inorganic nutrients flow through the ecosystem.

The simplest way to describe the flux of energy through ecosystems is as a food chain,

food web and ecological pyramids, in which energy passes from one trophic level to the next,

1.2.1. FOOD CHAIN: A food chain is the path of food from a given final consumer back 

to a producer. For instance, a typical food chain in a field ecosystem might be: Grass --->Grasshopper --> Mouse ---> Snake ---> Hawk. Such a path of food consumption is called a

food chain. Each level of consumption in a food chain is called a trophic level.

All energy available to organisms originates in plants. Because it is the first stepin the production of energy for living things, it is called  primary producers. Producers

convert energy from the environment into carbon bonds, such as those found in the sugar 

glucose.  Plants are the most obvious examples of producers; plants take energy fromsunlight and use it to convert carbon dioxide into glucose (or other sugars). Algae and

cyanobacteria are also  photosynthetic producers, like plants. Other producers include

 bacteria living around deep-sea vents. These bacteria take energy from chemicals comingfrom the Earth's interior and use it to make sugars. Another word for producers is

autotrophs.   Herbivores obtain their energy by consuming plants or plant products,

carnivores eat herbivores, and detritivores consume the droppings and carcasses. A simple

food chain is one, in which energy from the sun, captured by plant photosynthesis, flows

9

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 10/23

from one trophic level  to other trophic level via the  food chain. A trophic level is

composed of organisms that make a living in the same way i.e., they are all  primary

 producers (plants),  primary consumers (herbivores) or  secondary consumers

(carnivores). Dead tissue and waste products are produced at all levels. Scavengers,

detritivores, and decomposers collectively account for the use of all such "waste" --

consumers of carcasses and fallen leaves may be other animals, such as crows and beetles, but ultimately it is the microbes that finish the job of decomposition.

How many trophic levels can an ecosystem support? The answer depends on

several factors, including the amount of energy entering the ecosystem, energy loss

 between trophic levels, and the form, structure, and physiology of organisms at each level.At higher trophic levels, predators generally are physically larger and are able to utilize a

fraction of the energy that was produced at the level beneath them, so they have to forage

over increasingly large areas to meet their caloric needs.

Because of these energy losses, most terrestrial ecosystems have no more than

five trophic levels, and marine ecosystems generally have no more than seven. Thisdifference between terrestrial and marine ecosystems is likely due to differences in the

fundamental characteristics of land and marine primary organisms. In marine ecosystems,microscopic phytoplankton carry out most of the photosynthesis that occurs, while plants

do most of this work on land. Phytoplankton are small organisms with extremely simple

structures, so most of their primary production is consumed and used for energy by grazingorganisms that feed on them. In contrast, a large fraction of the biomass that land plants

 produce, such as roots, trunks, and branches, cannot be used by herbivores for food, so

 proportionately less of the energy fixed through primary production travels up the food

chain.

Growth rates may also be a factor. Phytoplankton are extremely small but growvery rapidly, so they support large populations of herbivores even though there may be

fewer algae than herbivores at any given moment. In contrast, land plants may take years toreach maturity, so an average carbon atom spends a longer residence time at the primary

 producer level on land than it does in a marine ecosystem. In addition, locomotion costs are

generally higher for terrestrial organisms compared to those in aquatic environments.

1.2.2. Food web: It is a complex pattern of feeding relationships among organisms.

There cannot be too many links in a single food chain because the animals at the end of the

chain would not get enough food (and hence energy) to stay alive. Most animals are part of 

more than one food chain and eat more than one kind of food in order to meet their food

and energy requirements. These interconnected food chains form a food web.

10

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 11/23

1.2.3. Ecological pyramids: According to Charles Elton (1927) relationship between

the biomass, energy content and the numbers of the producers, consumers and so on in an

ecosystem, is of first order and can be represented in the form of pyramid with producers at

the bottom and carnivores at the top. On an average, about 10% of the energy available inone trophic level will be passed on to the next; this is primarily due to the following three

reason.

1. not everything in the lower levels gets eaten2. not everything that is eaten is digested

3. energy is always being lost as heat

Therefore, it is reasonable to assume in terms of biomass, that each trophic level will weigh

only about 10% of the level below it, and 10% as much as the level above it which can berepresented in the form of a pyramid

1.2.4. Bioaccumilation, bioconcentration and Bio(logical) Magnification:Bioaccumulation refers to the degree to which an organism takes up and retains acontaminant from all applicable exposure routes. Bioaccumulation takes into account that

organisms may accumulate contaminants through multiple exposure routes and that the

total accumulation will depend upon the rate of intake versus the rate at which theorganism is capable of eliminating (through urine or feces) or breaking down the chemical

through metabolic processes.

11

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 12/23

Bioconcentration refers to the absorption or uptake of a chemical from the media to

concentrations in the organism's tissues that are greater than in surrounding environment.

The degree to which a contaminant will concentrate in an organisms is expressed as a bioconcentration factor (BCF), which is defined as the concentration of a chemical in an

organism's tissues divided by the exposure concentration. Thus, a BCF of 100 means that

the organism concentrates that chemical to a concentration 100 times greater than in thesurrounding media. Within a species, bioconcentration factors differ for different chemical

compounds.

 Biological magnification is the tendency of pollutants to become concentrated insuccessive trophic levels. A classic case of biomagnification is that of DDT.

We are concerned about these phenomena because together they mean that even small

concentrations of chemicals in the environment can find their way into organisms in high

enough dosages to cause problems. In order for biomagnification to occur, the pollutantmust be:

1. long-lived2. mobile

3. soluble in fats4. biologically active

If a pollutant is short-lived, it will be broken down before it can become dangerous. If it is

not mobile, it will stay in one place and is unlikely to be taken up by organisms. If the

 pollutant is soluble in water it will be excreted by the organism. Pollutants that dissolve infats, however, may be retained for a long time. It is traditional to measure the amount of 

 pollutants in fatty tissues of organisms such as fish. In mammals, we often test the  milk 

 produced by females, since the milk has a lot of fat in it and because the very young are

often more susceptible to damage from toxins (poisons). If a pollutant is not active biologically, it may biomagnify, but we really don't worry about it much, since it probably

won't cause any problems.

1.3 Natural resources:

 Natural resources are the materials that are needed to sustain life and livelihood on Earth. Theyinclude air, water land food, forest, paper, wood products, medicinal plants and minerals for metals, fuel, energy etc. The natural resources fall into three general categories based on their availability as:

1. Non-renewable resources that cannot be recycled

a. Eg. energy resources like fossil fuels, as the energy released from them is radiated back into outer space in the form of low-grade heat.

2. Perpetual Non-renewable resources: that can be recycled include all non-energy mineralresources that occur in the earth crust.

a. Eg. materials like copper, aluminum, iron etc. can be collected after use and

recycled.

12

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 13/23

3. Renewable resources: are those that are replenished through relatively rapid natural

cycles.

a. Eg. oxygen in the air, which is replenished through photosynthesis and

 b. water that is replenished through hydrologic cycle. \

c. Food Resources from plants & animals

1.3.1 N ON -  RENEWABLE   ENERGY   RESOURCES  

a) Fossil fuels:1. Coal: Coal is a hard, black coloured, rock like substance. It is made up of carbon,

hydrogen, oxygen, nitrogen and varying amounts of sulfur. There are three main types of coal – anthracite, bituminous and lignite. Anthracite coal is the hardest and has more carbon, which

gives higher energy content. Lignite is the softest and is low in carbon but high in hydrogen

and oxygen content. Bituminous is in between. The precursor to coal – peat is still found inmany countries and is also used as an energy source.

Coal is mined out of the ground using various methods. Some coal mines are dug by sinking vertical or horizontal shafts deep under ground and coal miners travel by elevators

or trains deep under ground to dig the coal. Other coal is mined in strip mines where hugesteam shovels strip away the top layers above the coal. The layers are then restored after the

coal is taken away. The coal is then shipped by train and boats and even in pipelines. In

 pipelines, the coal is ground up and mixed with water to make what is called slurry. This isthen pumped many miles through pipelines. At the other end, the coal is used to fuel power 

 plants and other factories.

2. Oil: Oil is another fossil fuel. It was also formed more than 300 million years age. Diatomsare sea creatures in the size of a pin head and the dead diatoms settle on the sea floor. Here

they were buried under sediment and other rock. The carbon from the dead organisms

eventually turned into oil under great pressure and heat. The demand for oil increased with theincreasing of the population. Oil and natural gas are found under ground between folds of rock and in areas of rock that are porous and contain the oils within the rock itself.

3. Natural gas: Natural gas is lighter than air. Natural gas is mostly made up of a gas called

methane. Methane is a simple chemical compound that is made up of carbon and hydrogenatoms. This gas is highly flammable. Natural gas is usually found near petroleum underground.

It is pumped from below the ground and distributed to larger areas. Natural gas usually has no

odour. Before it is sent to the pipelines and storage tanks, it is mixed with a chemical that givesa strong odour. The odour smells almost like rotten eggs. The odour makes it easy to smell if 

there is a leak.

4. Nuclear energy: Nuclear power plants provide about 17% of the world’s electricity. Some

countries depend more on nuclear power for electricity than other. In France, about 75% of theelectricity is generated from nuclear power. In the United States, nuclear power supplies about

16% of the electricity overall, but some states get more power from nuclear plants than others.

There are more than 400 nuclear power plants around the world, with more than 100 in theUnited States.

1.3.2 PERPETUAL NON-RENEWABLE RESOURCES

13

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 14/23

a) Mineral Resources

Mineral resources are broadly defined as elements, chemical compounds, minerals or rocks

that are concentrated in a form that can be extracted to obtain a usable commodity. The finite stock 

of minerals on earth is non-renewable. The oceans covering nearly 71% of the earth is another reservoir for many materials. Most of the elements in oceans have been weathered from crustal

rocks and transported to the oceans by rivers. Other elements are transported through wind or 

glaciers. The distribution of human population is intimately related to the distribution of theseresources.

Origin of Mineral Resources

 Nearly all aspects and processes of the geologic cycle are involved to some extent in

 producing local concentrations of useful materials. For example, it is now believed that plate

tectonics is responsible for the formation of some mineral deposits. According to the theory of 

plate tectonics, the continents 'float' on the material below them, called tectonic plates, and move

slowly across the earth surface. Metallic ores are thought to be deposited where the tectonic platesseparate and where they come together or converge. At divergent plate boundaries, cold ocean

water comes in contact with hot molten rock. The heated water is lighter and more activechemically. It rises through fractured rocks and leaches metals from them. The metals are carried

in solution and then deposited as metal sulphides on cooling of water. As molten rock cools,

heavier minerals that crystallize early may slowly sink or settle towards the bottom, while lighter minerals that crystallize later are left at the top. For example, when molten rocks containing carbon

under very high pressure cool slowly, diamonds may be produced.

Sedimentary processes are often significant in forming minerals. The best sand and graveldeposits are the finer material has been removed by water or wind.

Some mineral deposits are formed by biological processes and many minerals are formedunder conditions of biosphere that have been greatly altered by life. Organisms are able to form

many kinds of minerals, such as calcium minerals in shells and bones. They cannot be formed

inorganically in the biosphere. Thirty-one different biologically produced minerals have beenidentified.

Classification of Minerals

Metallic minerals: are those found in the form of ores & from which we get metals such as iron,

copper, gold and lead. These ores also contain several impurities. Therefore, metals have to be

separated from these compounds.

Non-metallic minerals: are those found in the form of deposits & from which we get non-metalssuch as nitrate, sulfur, potash, salts, coal and petroleum. Coal and petroleum are used as fuel;

hence they are also known as mineral fuel.

Environmental Effects of Extracting & Using Mineral Resources

A series of primary and secondary environmental impacts will result from the mining activities are

listed below.1. Scarring and disruption of land surface.

14

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 15/23

2. Underground coal mine fires are difficult to put off.

3. Subsidence of land over underground mines.

4. Wind or water caused erosion of spoils and tailings.

5. Acid mine drainage contamination of surface and ground water, leading loss of aquatic life.

6. Gangue-waste mineral material.

7. Tailing-waste following benefaction.8. The lands, water bodies, air and environment are polluted due to constant release of chemical

wastes, dust generated by blasting and excavation and the dumping of mine wastes and overburden

in the surrounding lands and rivers.9. Grade of ore determines the environmental impact of mining it. Effect on environment increases

over time.

10. Majority of the health problems in mining regions, namely, tuberculosis, cough and cold, malaria,

skin diseases, diarrhoea, staining of teeth, joints pain, arthritis, lethargy, etc. are caused due tounchecked pollution and high levels of toxicity, mine tailings and mine disasters.

11. Even women and children who are not working in the mines are constantly exposed to various

respiratory illnesses due to inhalation of dust particles and become victims of skin diseases,

experience malfunctioning of various sensory organs, which has a long-term impact on their reproductive health.

12. Noise and dust pollution affects women the most during pregnancy13. The depletion of groundwater due to over consumption for mining purposes, bringing serious

changes in the watertable, affects the irrigation and drinking water facilities of the communities

14. Communities surrounding mine sites are forced to consume the contaminated drinking water fromsources like rivers, streams, wells and bore pumps due to ill-treated or non-treated chemical wastes

and debris by the mining companies which seep into the groundwater and soil.

15. Communities living around the mine sites are constantly vulnerable to mining accidents. Mining

companies use explosives for blasting, which results in houses cracking and collapsing on womenand children or sometimes companies do not warn them of explosions while they are working in

the fields or walking in their villages, thereby either killing or deforming them.

16. Loss of eyesight is common, as women are not given any protective gear in any of the mine sites,whether involved in stone crushing, loading and transporting mineral ores like coal.

17. The forest cover degenerates gradually in all mining regions due to pressure from mining

operations and from new populations settling down in the fringes.

1.3.3  RENEWABLE   ENERGY   RESOURCES  

1.3.3.1 Food Resources: Food resources include plants and animals. There are about 270,000

different plant species of which slightly more than 100 provide about 90% of the food that humans

consume either directly or indirectly. Just around 12 species of crops provide the bulk of food for humans. Of these, just three – rice, wheat and corn provide about half of the calories that people

consume. If disease or any other factor wipe out one of the important crops, humans might by

threatened by severe famine. Therefore, identifying and study the cultivation requirements of other consumable plant species are of utmost importance.

Food particularly rich in protein is provided by animals. These foods include sea foods, poultry,cattle etc. There are about 80 species of livestock. Although nutritious, livestock is an expensive

15

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 16/23

source of food because animals are inefficient converters of plant food. Of every 100 calories of 

 plant material a cow consumes, it burns off approximately 86 calories in its normal metabolic

functioning and only 14 calories out of 100 are stored in the cow to be consumed by humans.Meat consumption is high in affluent societies. Therefore, large portions (almost half) of the crops

grown in highly developed countries are used to produce livestock animals for human

consumption.

World food problems: The UN Food and Agriculture Organization (FAO) in 1998 estimated

that 828 million people lacked access to the food needed to be healthy and to lead productive lives.Most of these people live in rural areas of the poorest developing counties. Currently, 86 countries

are considered food-deficient countries. South Asia and sub-Saharan Africa are the regions of the

world with the greatest food insecurity. 

In underdeveloped and developing countries, malnutrition is a big problem which results in

diseases such as merasmus, kwashiorkar, anaemia etc. Over nutrition is most common in highly

developed countries.

Agriculture

The practice through which specific plant species are cared and managed so as to obtainmaximum yield of consumable parts of the plants is called agriculture. The demand for food

 production, linked with "tremendous population growth, has been increasing fast world over. The

green revolution has resulted chiefly from the modernisation of agriculture, which involves highlydomestic plant species, sophisticated chemicals and large fuel energy subsidies. According to an

estimate, to double the crop yield through modern agriculture, a ten-fold increase in fertilisers,

 pesticides and horsepower is required.

The Environmental Impacts of Modern Agriculture:

The practices of modern agriculture have resulted in several environmental problems that

impair the ability of non-agricultural, terrestrial and aquatic ecosystems to provide essentialecosystem services.

1. The agricultural use of fossil fuels and pesticides produces air pollution.

2. Untreated animal wastes and agricultural chemicals such as fertilizers and pesticides causewater pollution that can reduce biological diversity, harm fisheries and lead to outbreaks of 

species such as algal bloom.

3. Some agricultural chemicals have been detected in water deep underground, as well as in

surface waters. Nitrates from animal wastes and commercial inorganic fertilizers are probablythe most widespread groundwater contaminants in agricultural areas.

4. In livestock factories, thousands of animals are confined to small pens in buildings the size

of football fields. Such large concentrations of animals create many environmental problems,including air and water pollution.

5. The quantity of manure produced by several hundred thousand cattle in one livestock 

factory causes .a severe waste disposal problem. At hog factories, the manure is often stored Indeep lagoons that have the potential to pollute the soil, surface water and groundwater, causing

major fish kills.

6. People living near livestock factories dislike the odour, which often exceeds federal and

state guidelines for emission and causes their property values to decline.

16

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 17/23

7. Many insects, weeds and disease-causing organisms have developed or are developing

resistance to pesticides. Pesticide resistance forces farmers to apply progressively larger 

quantities of pesticides.8. Residues of pesticides contaminate our food supply and reduce the number and diversity of 

 beneficial micro-organisms in the soil. Fishes and other aquatic organisms are sometimes killed

 by pesticide run-off into lakes, rivers and estuaries.9. Degradation is the natural or human-induced process that decreases the future ability of the

land to support crops or livestock animals. Soil erosion, which is exacerbated by large-scale

mechanised operations, causes a decline in soil -fertility, and the sediments lost because of erosion damage water quality.

10. Examples of other types of degradation are compaction of soil by heavy farm machinery

and waterlogging and salinisation of soil caused by improper irrigation methods.

11. Crop production requires enormous amounts of water.12. Some agricultural regions remove water from aquifers faster than it is recharged by

 precipitation, thereby lowering water tables.

13. As a result of mismanagement of water resources, vast areas of irrigated land have become

too waterlogged or too salty to grow.14. Clearing grasslands and forests and draining wetlands to grow crops have resulted in

habitat fragmentation and losses that reduce biological diversity.15. Many species have become endangered or threatened as a result of habitat loss caused by

agriculture.

 Problems Associated with Pesticide Use:

Although pesticides have their benefits, they are also accompanied by several problems.

1. Creation of New Pests: In some instances, the use of a pesticide has resulted in a pest

 problem that did not exist earlier. Creation of new pests implies, turning minor pest organismsinto major pests

2. Evolution of Genetic Resistance: The prolonged use of a particular pesticide can cause a

 pest population to develop genetic resistance to that pesticide. Genetic resistance is anyinherited characteristic that decreases the effect of a pesticide on a pest.

3. Imbalances in the Ecosystem: One of the worst problems associated with pesticide use is

that pesticides affect species other than the pests for which they are intended. Beneficial insectsare killed as effective~ as pests.

4. Persistence, Bioaccumulation and Biological Magnification: The effects of DDT on

many bird species first demonstrated certain problems of chlorinated hydrocarbon pesticide

use. The persistence of synthetic pesticides is a result of their novel (not found in nature)chemical structures. Natural decomposers such as bacteria have not yet evolved ways to

degrade synthetic pesticides, and hence they accumulate in the environment and in the food

web.

5. Mobility in the Environment: Another problem associated with pesticides is that they do

not stay where they are applied but tend to move through the soil, water and air, sometimes

long distances. Pesticides that are applied to agricultural lands and then get washed away intorivers and streams when it rains, can harm fishes.

 Problems associated with the use of Fertilizers

17

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 18/23

 Nutrients are lost from agricultural fields through run-off, drainage or attachment to eroded soil

 particles. The amounts lost depend on the soil type and organic matter content, climate, slope of 

the land and depth to groundwater, as well as on the amount and type of fertilizer and irrigationused.

The three major nutrients in fertilizers are nitrogen, phosphorus and potassium.1. Nitrogen is the most readily lost because of its high solubility in the nitrate form.

Leaching of nitrate from agricultural fields can elevate concentrations in underlying

groundwater to levels unacceptable for drinking water quality.

2. Phosphorus does not leach as readily as nitrate because it is more tightly bound to soil

 particles. However, it is carried with eroded soils into surface water bodies, where it may cause

excessive growth of aquatic plants. If this process proceeds far enough, lakes and reservoirs become choked with decaying mats of algae, which have offensive odours and can cause fish

kills from the resulting lack of dissolved oxygen.

3. Potassium, the third major nutrient in fertilizers, does not cause water .quality problems because it is not hazardous in drinking water and is not a limiting nutrient for growth

of aquatic plants. It is tightly held by soil particles and hence can be removed from fields byerosion, but generally not by leaching.

1.3.3.2 Forest ResourcesA forest is a natural ecosystem having diversified species of plants, shrubs, small and large trees indifferent stages of lifespan.

Uses of Forest Resources

1. Forest biomass satisfies the basic requirements of the tribal people in its immediate vicinity.

Forests contribute to the livelihood of 90% of the 1.2 billion people living in extreme poverty.2. Healthy forests play a key role in regulating water quality and quantity and can reduce the risksof landslides, floods and droughts.3. Forests also harbor medicinal plants that provide primary healthcare for an estimated-80% of the

 population in developing countries.

4. Wood, which has various applications in domestic and industrial processes, is the chief product

of forests.5. Wood when used as fuel has certain advantages over coal as its sulfur and ash contents are very

low.

6. Forests provide raw materials for various wood-based industries. viz., pulp and paper, compositewood, rayon and other man-made fibres, sport goods, furniture, boat building, matches, etc.

7. Miscellaneous  products like bamboos, resins, gums, oils, fibers, medicines, shellac, etc. are also

obtained from forests.8. Forests serve as a source of carbon dioxide sinks, by the process of photosynthesis, during

which it gives out oxygen that adds to the atmospheric oxygen concentration.9. It maintains the natural ecological balance by providing habitat for various species of plants andanimals.10. The forests prevent soil erosion and desertification.11. The humidity and temperature of the air and soil is maintained favorably by the forests as theyretain water in the soil and convert water into water vapors by transpiration.12. Forests serve as windbreaks. Along the Saurashtra coast in India, casuarinas that are bushy and

18

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 19/23

sturdy to withstand strong winds, both hot and cold, successfully check the degradation due to salt-laden coastal winds.13. Fodder from the forests forms an important source for cattle and other grazing animals in thehilly and the arid regions during a drought.14. Fences created with trees and shrubs are preferred in developing countries as they are cheap tomaintain and yet give protection.15. Some species of trees have the ability to return nitrogen to the soil through root decomposition

or fallen leaves. Such plants help in soil improvement.

Overexploitation:

1. Excessive cutting of trees for commercial and industrial purpose is referred to as overexploitation.This results in a number of ecological and economical losses.

2. Nutrients removed in harvested wood were potentially large enough to reduce subsequent forestgrowth at some places.

3. Excessive cutting of trees promotes erosion of soil. In this environment, nutrients in the soil areleached off' and the micro-organisms which can replenish these nutrients are disturbed.

4. Deforestation can cause the destruction of the habitats that support biological diversity.

Deforestation: The temporary or permanent clearance of large expanses of forest for agriculture or 

other uses.

1. Causes of forest destruction includea. Fires caused by droughts and land clearing practices. b. Expansion of agriculture, and construction of roads in forests.c. Tree harvests, when forests are converted to other land uses; they no longer makevaluable contributions to the environment or to the people who depend on them.2. Forest destruction, particularly in the tropics, threatens indigenous people whose culturaland physical survival depends on the forests.3. Deforestation results in decreased soil fertility through rapid leaching of the essentialmineral nutrients found in most forest soils.4. Uncontrolled soil erosion, particularly on steep deforested slopes, can affect the production of hydroelectric power as silt builds up behind dams.5. Increased sedimentation of waterways caused by soil erosion can also harm downstreamfisheries.6. In drier areas, deforestation contributes to the formation of deserts.7. When a forest is removed, the total amount of surface water that flows into rivers andstreams actually increases. However, because this water flow is no longer regulated by the forest,the affected region experiences alternating periods of flood and drought.8. Deforestation is thought to induce regional and global climate changes. Trees releasesubstantial amounts of moisture into the air; about 97% of the water that roots absorb from thesoil is evaporated directly into the atmosphere. This moisture falls back to the earth in thehydrologic cycle. When a large forest is decimated, rainfall is most likely to decline and droughtsmay become more common in that region.

Management of Forests

The science of managing forests for its many uses is called silviculture. Of various strategiesemployed in forest management, some special considerations are as follows:

•Restrained felling: Sustained yield in forestry can be obtained by the management of forests in such a way that a modest timber crop may be harvested indefinitely, year after 

year, without being depleted.

• Block and selective cutting: Block cutting method can effectively be applied in a forest

having almost even-aged trees of a fewer number of species. In this method, trees are

harvested not at random but in blocks.

• Reforestation: In any case, whether the forests are harvested by block or selective cutting,

the reforestation of that area is essential so as to ensure sustained yield.

19

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 20/23

• Control of disasters: Disease, pest and fire are the chief agents of forest destruction.

Forest diseases, resulting from viruses; parasitic fungi, rusts and nematodes, cause about45% of the total timber destruction. Efficient quarantine, use of pesticides, biological and

integrated pest control can be used to control pest.

• Recycling of forest products: Recycling of paper and other forest products plus stringent

conservation could reduce per capita pressure on the annual growth without reducingindividual use.

1.3.3.3. WATER SOURCES: 

Water is most essential for the existence of living organisms. It is required by them both

for their survival and development. Oceans cover around 70% of earth’s surface. Only 3% by

volume of water on earth is fresh-water and most of this is largely unavailable as three quarters of all fresh-water is locked away in the form of ice caps and glaciers located in polar areas far from

most human habitation. Only about 1% is easily accessible surface fresh-water in the form of 

lakes, rivers and available ground water.

Precipitation is the primary source of irrigation water; in the form of rainfall in hot regions

and as rainfall/snow in cold regions. These give rise to secondary sources of irrigation, broadlyclassified as:

1. Surface water resource: The surface water consists of direct run off from rain fall, snow meltand flow in streams regenerated from ground water.

2. Ground water resources: the ground water resource is dynamic in nature as it grows with the

expansion of irrigation. The alluvial plains, namely the Indus, the ganga and the Brahmaputra, Narmada are richest in ground water.

3. Auxiliary water resource: here the water after serving the primary purpose, which is of non-

consumptive or partial consumptive type, can be further utilized for irrigation, either with or without treatment.

Use of Water:1. Productive use: Water is primarily used for irrigation of food crops, fodder crops,

medicinal herbs, etc

2. Consumptive use: Water is consumed in exhaustive quantities for domestic purposes' such

as drinking, cooking, washing, etc. Water finds its application in almost all the processes inindustries, starting from the manufacturing processes to housekeeping activities

3. Commercial use: Water consumed for carrying out commercial activities.

DAMS-BENEFITS AND PROBLEMS:

Benefits: Dams have been built with the multi purpose uses of the waters they impound i.e.

1. irrigation,

2. power generation,3. flood control,

4. urban water supply,

5. fisheries,6. transportation and

7. recreation-are claimed to offer solution to diverse problems.

20

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 21/23

Problems: It has often been seen that big dams can create more problems than they solve. Some

negative aspects of high dams are outlined below.

1. Silting: Silt fails to reach the floodplains where it is needed to renew the soil, and it graduallyfills up the reservoir, reducing the dam's storage capacity for power generation.

2. Salting and water logging: High dams raise water tables until subsoils are perpetually sodden;

controlled irrigation made possible by the dams leads to a fatal build-up of salts; fields that nolonger have a chance to dry out become waterlogged.

3. Evaporation and seepage: In the tropics, wherever man-made reservoirs have been created,

evaporation and seepage have been seen.

4. Destruction or habitats: People have to be evicted from their homes in order to flood a great

river valley and have to be rehabilitated elsewhere. The destruction of habitats of wildlife and

the drowning of creatures isolated by rising waters also deserves consideration

5. Water borne diseases: Man-made reservoirs and the irrigation works they serve greatlyincrease the incidence of waterborne diseases.

6. Earthquakes: Seismologists believe that the almost incomprehensible weight of large man-

made reservoirs increases the risk of earthquakes.

7. Fisheries: The deep waters contained by most high dams tend to be sterile, with no food for fish. Dams can eliminate the catch of migratory fish by preventing them from reaching their 

spawning grounds.

8. Waterweeds: The damming of watercourses aggravates the proliferation of water hyacianth and

other aquatic weeds. Reducing the flow of water from a river changes the landscape it flows

through, which in turn can affect "the ecosystem's flora and fauna. A dam holds back,sediments, especially the heavy gravel and cobbles. The storage of water in dams delays and

reduces floods downstream. Thereby reducing the native plants and animals depend on its

variations for reproduction, hatching, migration and other important lifecycle stages.

Eutrofication of Lakes

Eutrophication is caused by the increase of chemical  nutrients, typically compoundscontaining nitrogen or phosphorus. It may occur on land or in water .

Eutrophication is frequently a result of nutrient pollution such as the release of sewage

effluent into natural waters (rivers or coasts) although it may also occur naturally in situations

where nutrients accumulate (e.g. depositional environments) or where they flow into systems on anephemeral basis (e.g. intermittent upwelling in coastal systems). Eutrophication generally promotes

excessive plant growth and decay, favors certain weedy species over others, and is likely to cause

severe reductions in water quality. In aquatic environments, enhanced growth of choking aquaticvegetation or phytoplankton (that is, an algal bloom) disrupts normal functioning of the ecosystem,

causing a variety of problems such as lack of oxygen in the water for fish and shellfish to survive.

The water then becomes cloudy, colored a shade of green, yellow, brown, or red. Human society isimpacted as well: eutrophication decreases the resource value of rivers, lakes, and estuaries such

that recreation, fishing, hunting, and aesthetic enjoyment are hindered. Health-related problems can

occur where eutrophic conditions interfere with drinking water treatment.

Eutrophication can be a natural process in lakes, as they fill in through geological time,though other lakes are known to demonstrate the reverse process, becoming less nutrient rich with

21

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 22/23

time. Estuaries also tend to be naturally eutrophic because land-derived nutrients are concentrated

where run-off enters the marine environment in a confined channel.

Human activities can accelerate the rate at which nutrients enter  ecosystems. Runoff fromagriculture and development, pollution from septic systems and sewers, and other human-related

activities increase the flux of both inorganic nutrients and organic substances into terrestrial,aquatic, and coastal marine ecosystems (including coral reefs). Elevated atmospheric compounds

of nitrogen can increase soil nitrogen availability.

Phosphorus is often regarded as the main culprit in cases of eutrophication in lakes

subjected to point source pollution from sewage. The concentration of algae and the trophic state

of lakes correspond well to phosphorus levels in water. Studies conducted in the ExperimentalLakes Area in Ontario have shown a relationship between the addition of phosphorus and the rate

of eutrophication. Humankind has increased the rate of phosphorus cycling on Earth by four times,

mainly due to agricultural fertilizer production and application. Between 1950 and 1995,

600,000,000 tonnes of phosphorus were applied to Earth's surface, primarily on croplands. Control

of point sources of phosphorus have resulted in rapid control of eutrophication, mainly due to policy changes.

A wide range of contaminants can reach the river either via groundwater or through

drainage ditches, including artificial fertilizer residues, insecticides, herbicides, pesticides andfarmyard waste, all of which are potentially very harmful. Accidental milk spillage from dairies is

a serious contaminant.

Undiluted animal manure (slurry) is one hundred times more concentrated than domesticsewage, and can carry a parasite, Cryptosporidium, which is difficult to detect. Silage liquor (from

fermented wet grass) is even stronger than slurry, with a low pH and very high BOD (Biological

Oxygen Demand). With a low pH, silage liquor can be highly corrosive; it can attack syntheticmaterials, causing damage to storage equipment, and leading to accidental spillage.

Milk spillage, silage liquor, cattle and pig slurry; these are all examples of point source

 pollution. Diffuse source pollution from agricultural fertilizers is more difficult to trace, monitor 

and control. High nitrate concentrations are found in groundwater and may reach 50mg/litre (the

EU Directive limit). In ditches and river courses, nutrient pollution from fertilizers causeseutrophication. This is worse in winter, after autumn ploughing has released a surge of nitrates;

winter rainfall is heavier increasing runoff and leaching, and there is lower plant uptake.Phytoplankton and algae thrive in the nutrient-rich water. Normally, blue-green algae are veryimportant in the river ecosystem, photosynthesising sunlight energy, and liberating oxygen into the

water. In large numbers, however, algae can become excessive, discolouring the water, giving an

unpleasant smell and robbing the water of valuable oxygen as bacteria work overtime feeding ondead algae remains. Blue-green algae can also produce toxins, which kill wildlife, cause skin

rashes, and cause pains and stomach upsets.

Eutrophication is thus depriving the river of oxygen (called "oxygen debt"). As algae

dominate and turn the water green, the growth of other water plants is suppressed; these die first,disrupting the food chain. Death of invertebrates and fish follow on, and their dead remains in turn

22

7/31/2019 Unit I. Part -A. Introduction, Components, Ecosystem and Natural Resources.

http://slidepdf.com/reader/full/unit-i-part-a-introduction-components-ecosystem-and-natural-resources 23/23

lead to excess bacterial activity during decomposition, reducing oxygen levels still further. Water 

with high BOD figures are badly polluted, lower figures are better.