The atmosphere is the key symbol of global interdependence. Margaret Meade.

The atmosphere is the key symbol of global interdependence.

Margaret Meade

Air Pollution

Chapter 18

Nature of the Atmosphere

• Thin layer of gases surrounding earth• Density (air mass/air volume) is greater at sea

level than in mountains• Atmospheric pressure (force/area) decreases

with altitude• 78% nitrogen, 21% oxygen (water vapor,

argon, CO₂)

Layers of Atmosphere

• Troposphere: layer closest to earth (extends 11 miles above surface)

-responsible for weather, climate, greenhouse effect

• Stratosphere: layer surrounding troposphere (extends 30 miles above troposphere) -ozone layer: protects earth from too much of

sun’s UV radiation

Fig. 19-2, p. 440

Atmospheric pressure (millibars)

Temperature

Thermosphere

Pressure

Mesopause

Heating via ozoneMesosphere

Stratopause

Altit

ude

(kilo

met

ers)

Stratosphere Altit

ude

(mile

s)

Tropopause

Ozone “layer”

Heating from the earthTroposphere

Temperature (˚C)

Pressure = 1,000 millibars at ground level

(Sea level)

Air Pollution

(all environmental problems involve the air)• Primary air pollutants: released directly from

a source into the atmosphere -natural sources: dust, wildfires, volcanoes -manmade sources: primarily burning of fossil

fuels, burning of biofuels -may be stationary or moving

Fig. 19-3, p. 442

CO CO2

SO2 NO NO2

Most hydrocarbons SO3

Most suspended particles HNO3H2O2 O3 PANs

Most NO3– and SO4

2– salts

Sources Natural Stationary

Mobile

H3SO4

Air Pollutants (cont’d)

• Secondary pollutants: product of reactions between primary pollutants and other chemicals in the atmosphere

-prevailing winds carry pollution from source to other areas

-responsible for hundreds of millions of lung problems (WHO)

FYI: Exam Tip

• Be specific in identifying types of pollution. Simply stating that an activity results in

“pollution” won’t earn you points. Exemplar: Burning wood for fuel produces CO

and is a major source of indoor air pollution in developing countries.

Major Air PollutantsCarbon oxides: colorless, odorless, toxic(prevents O₂ from binding with red blood cell)• Carbon monoxide (CO) -incomplete burning of carbon-based matter (tobacco, forest fires, vehicles, factories) -catalytic converters remove CO from vehicle exhaust• Carbon dioxide (CO2)

-93% results from carbon cycle -7% results from human activities (mostly burning fossil

fuels)Health issues: asthma, COPD, heart attacks, headache,death

Major Air Pollutants (cont’d)Nitrogen oxides: gas which form when N₂ combineswith O₂• Nitrogen dioxide: reddish brown gas -forms photochemical smog in cities• Nitric acid -”acid rain”/acid deposition• Nitrous oxide (N₂O) -greenhouse gas emitted from burning animal

waste, fossil fuel

Major Air Pollutants (cont’d)

(Human issues: discussed later)(Environmental issues: discussed later)


Sulfur dioxide; sulfuric acid • ⅓ comes from sulfur cycle• ⅔ comes from combustion of coal, oil refining• Scrubbers: remove SO₂ from coal smoke by

combining it with calcium carbonate (sludge deposited in landfills)

(Health issues: discussed later)(Environmental issues: discussed later)


Ground-level (tropospheric) Ozone (O₃)• Secondary pollutant• Major part of photochemical smog• Unstable, strong oxidant (sheds O to become O₂)Health issues: irritates eyes, lungs, heartEnvironmental issues: damages plants, fabrics, paints, rubber in tires(Remember: ozone in the stratosphere is good;ozone in the troposphere is harmful)

Major Air Pollutants (cont’d)Suspended Particulate Matter (SPM/PM-10)• Primary pollutant- solid, liquid “droplets” less than

10mm in diameter• Emitted from burning coal/dung, plowing, tobacco

smoke, vehicles• Includes mercury, cadmium (toxic heavy metals)• Electrostatic precipitator: removes particles from smoke

(negative charge on particle makes it stick to a positive plate; sludge is dumped in landfill)

Health issues: irritates eyes, lungs, can causemutations, cancers (mercury, heavy metals)Environmental issues: reduces visibility, corrodes metals


FYI: According to EPA, SMA is responsible for about 60,000 premature deaths/year in the US alone


Volatile organic compounds (VOCs):• Primary pollutant; most are hydrocarbons

emitted many plants, some are methane• ⅔ of global VOC methane emissions come from fossil fuel leaks, rice paddies, others include

solvents- trichlorethylene (TCE), benzene, and vinyl chloride (dry-cleaning, paints)

Health issues: cancer, blood disorders, immunesystem damage


Lead (Pb)• Primary pollutant; doesn’t break down in

environment• Released from lead additives in gas, peeling lead-

based paint (both banned in US in ‘70’s)Health issues: brain damage, mental retardation,partial paralysis, blindness, death(WHO estimates that 130-200 million children are atrisk of lead poisoning worldwide)

Core Case Study: When Is a Lichen Like a Canary?

• Lichens can warn us of bad air because they absorb it as a source of nourishment.

Figure 19-1

Core Case Study: When Is a Lichen Like a Canary?

• Some lichen species are sensitive to specific air-polluting chemicals.

• After Chernobyl, more than 70,000 reindeer had to be killed because they ate highly radioactive lichens

• Because lichens are widespread, long-lived, and anchored in place, they can help track pollution to its source.

Acid Deposition

(Remember, oxides of sulfur and nitrogen can befurther oxidized in the atmosphere to form acidprecipitation- snow, sleet, rain, fog- and dryfallout in the form of particulates)• Sulfuric acid-H₂SO₄/sulfate salts-SO₄²• Nitric acid-HNO₃/nitrate salts-NO₃²

Acid Deposition (cont’d)

• Source: coal-burning plants, ore smelters• Create regional air pollution downwind from

source (hundreds of miles away)• Wet deposition: acidic rain, fog, snow with

pH less than 5.6• Dry deposition: acidic particles• Buffers: some lime-containing soils that can

neutralize acids, minimize effects of acid rain

Fig. 19-6, p. 448

WindTransformation to sulfuric acid (H2SO4) and nitric acid (HNO3) Windborne ammonia gas and

particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts

Wet acid depostion (droplets of H2SO4 and HNO3 dissolved in rain and snow)Nitric oxide (NO)

Sulfur dioxide (SO2) and NO

Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts)

Acid fogFarm

OceanLakes in deep soil high in limestone

are buffered

Lakes in shallow soil low in limestone

become acidic

Acid Deposition

Figure 19-8

Effects of Acid Deposition

Health issues: damages respiratory system,irritates eyes, threatens food security(concentrates heavy metals in fish, dissolvesshells of mollusks, harms crops)Environmental issues: can leach aluminum,lead, cadmium from soil, which enters aquaticecosystems, can leach nutrients out of soil*thin mountain soils are most vulnerable to damage

Fig. 19-9, p. 451

Emissions

SO2 NOxAcid deposition

H2O2 O3

Others

Direct damage to leaves & bark

Reduced photo-synthesis and growth

Susceptibility to drought, extreme cold, insects, mosses, & disease organisms

Soil acidification Tree death

Leaching of soil nutrients

Release of toxic metal ions

Root damage

Reduced nutrient & water uptakeAcids

Lake

Groundwater

PANs

Results of Acid Deposition on Producers

• Soil acidification: root damage, reduced nutrient/uptake

• Direct damage to bark, leaves• Susceptibility to drought, cold, predation by

insects

Reducing Acid Rain

• Reduce coal use (increase alternate fuels)• Use of scrubbers to reduce emissions from

factories, vehicles• Add lime or phosphates to neutralize acidified

lakes (expensive)

Smog

• Industrialized/Gray-air smog: suspended droplets of salts, soot that hangs in urban air

-source: burning coal -major problem in China (16 of 20 most

polluted cities)• Photochemical/Brown-air smog: mix of

ozone, VOCs, NO, PANS (peroxyacyl nitrates) in urban air

Smog (cont’d)

• Photochemical/Brown-air smog: mix of ozone, VOCs, NO, PANS (peroxyacyl nitrates) in urban air

-UV from sun causes NO to react with plant VOCs

-increases with hotter, drier air

FYI: Sunlight plus Cars Equals Photochemical Smog

• Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog

• LA , Salt Lake City also has smog issues.

Figure 19-4

Factors Influencing Outdoor Pollution

Reducing pollution:1. Particles heavier than air settle out2. Rain, snow partially cleanse air3. Sea spray washes out air from ocean4. Winds mix polluted and unpolluted air5. Chemical reactions (sulfur, nitrates) form

acids which fall to earth


Increasing pollution:1. Heat island: urban buildings block air flow

(reduce dilution of pollutants)2. High temperatures promote photochemical

smog3. VOCs from thick urban forests promote p. s.4. Grasshopper effect- movement of pollutants

from tropics to poles


5. Temperature inversion: layer of warm air sits over cooler, polluted air; prevents cool air from rising and dispersing pollutants

- occurs in cities surrounded by mountains (think L A)

Fig. 19-5, p. 447

Warmer air Descending warm air mass

Inversion layer Inversion layer

Sea breezeIncreasing altitude

Decreasing temperature

Case Study: South Asia’s Massive Brown Cloud

• A huge dark brown cloud of industrial smog, caused by coal-burning in countries such as China and India, stretches over much of southeastern Asia.– In areas beneath cloud, photosynthesis is reduced,

interfering with crop development.– Fine particles and droplets in the cloud appear to be

changing regional climates (including rainfall).• May have contributed to floods in 2002 and 2005 which

killed thousands of people.

Indoor Air Pollution

• Usually a greater threat to health than outdoor air pollution

• May go undetected• Problem increases with poor ventilation

Major Indoor Pollutants

4 most dangerous indoor pollutants (accordingto EPA):• Tobacco smoke• Formaldehyde• Radioactive radon-222 gas• Very small fine and ultrafine particles

Tobacco Smoke

• Contains 70 carcinogens (including filter), 250 toxins• 2nd-hand smoke is considered to be a leading risk to

human health (from cigarettes)• Risk is magnified within enclosed spacesHealth issues: cancer, heart disease, birth defects,emphysemaRemediation: quit smoking, ban smoking inbuildings, improve building ventilationEconomic health cost in US: ≈$72 billion

Formaldehyde

• Found in common building materials (plywood, particleboard, wallpaper, carpet)

• Known carcinogenHealth issues: headaches, respiratory tract ,irritation, sore throats, dizziness, nausea, cancerRemediation: substitute formaldehyde-freematerials, increase building ventilation

Radon-222

• Colorless, odorless gas• Produced by natural radioactive decay of

uranium 238• Can seep from ground into cracks in

foundationsHealth issues: alpha particles damage lungs,leads to lung cancer (2nd leading cause of cancer)Remediation: Sealing cracks in foundations,increase ventilation

FYI: Radioactive Radon

• Radon-222, a radioactive gas found in some soils and rocks, can seep into some houses and increase the risk of lung cancer.

Sources and paths of entry for indoor radon-222 gas.

Figure 19-13

Fine Particles

Bacteria, viruses, pollen, dust, mildew, mold,yeast• Circulate in heating, cooling systems• Can create sick-building syndromeHealth issues: infectious disease, allergicreactions, headaches, irritated eyes and lungs,chronic fatigueRemediation: replace, disinfect air ducts orcondemn building(1 in 5 commercial buildings in US is considered“sick”)

FYI: Indoor Air Pollution

• Household dust mites feed on human skin and dust; live in materials such as bedding and furniture fabrics.– Can cause asthma attacks/

allergic reactions in sensitive people.

Figure 19-12

Other Pollutants

• Carbon monoxide -accumulates in enclosed spaces -results from inefficient combustion in gas

heaters, stovesHealth issues: headache, nausea, death• Asbestos -mineral once used in insulation, ceiling and

floor tilesHealth issues: skin and lung irritant, lung cancer

FYI

Remember: earth absorbs heat from sun andreleases heat back into the atmosphere whereits trapped by gases in the troposphere-greenhouse effect-effect is natural and necessary to maintain theright temp for life-human activities leading to an increase inthe greenhouse effect is the problem

Global Climate Change

4 major anthropogenic greenhouse gases:• CO₂• Nitrous oxide (N₂O)• Methane (CH₄)• Chlorofluorocarbons (CFCs)

Global Climate Change (cont’d)

CO₂Source: burning hydrocarbons -biggest contributor to greenhouse gases Remediation: -conservation of fossil fuels -switch to alternate fuels -sequester CO₂ in ground, plant trees, reduce

deforestation


N₂OSources: inorganic fertilizers, fossil fuels,

sewage treatment, decomp of biowaste -lingers long time in atmosphereRemediation: -conservation of fossil fuels -decrease use of fertilizers


CH₄Sources: cattle, fossil fuel mining, landfills, rice

cultivation -primary pollutant & VOC -more potent than CO₂Remediation: -capture for fuel -burning it


CFCs- molecules of chlorine & fluorine -Cl breaks off in stratosphere, breaks down an

ozone molecule (1 Cl ion may react with 1 x 10⁵ ozone molecules)Sources: once used in refrigerants, fumigants,

propellants in aerosol cans -deplete ozone -lingers in atmosphere, not water solubleRemediation: Montreal Protocol phased out CFCs

Effects of Climate Change

• Sea level rise: thermal expansion of water, melting of land-based glaciers

-degrades coastal wetlands, estuaries, reefs -saltwater intrusion -coastal flooding -positive feedback loop: exposed soil absorbs

more heat, melts more snow…

Effects of Climate Change (cont’d)

• Melting of permafrost: (ground under tundra is a sink for CO₂, CH₄)

-positive feedback loop: melting permafrost releases gases, increases heat in atmosphere…

(TransAlaska pipeline is already showing signs ofsustained damage due to permafrost melting)


• Extreme weather: severe drought, desertification, unusual snow events

-positive feedback loop: fewer plants means more CO₂ in atmosphere…

• Change in ocean currents: meltwater from Arctic circle may disrupt conveyor belt currents in N Atlantic (Gulfstream currents warm climate in Europe)


• Changing vegetative zone: temperature increases will move zones northward.

-threatens food security -increase in plant extinction rates• Biodiversity loss: -animals must find vegetation- migrate or die (arctic species are most vulnerable since there

is nowhere to migrate)

FYI: Atmosphere-Ocean Link

• CO₂ is dissolved in huge amounts in the oceans

• CO₂ forms carbonic acid in water so acidity in ocean increases

• Increased acidity inhibits production of mollusk shells, coral

• Warmer oceans will dissolve less CO₂, which means more in the atmosphere…

Stratospheric Ozone and UV Rays

• 3 types of UV radiation: A, B, C (A is least energetic, C is most energetic)

-UV B is of most concern to us• Ozone shields earth from UV radiation -O₂ is broken down by UV radiation -free O reacts with more O molecule to form O₃(back and forth exchange of O and O₃ shieldsearth from UV radiation)

Ozone Depletion

• First proposed by Rowland & Molina, 1970 (not widely accepted until the 80’s) -ozone is measured in Dobson units (DU): 1 DU = ozone column 0.01 mm thick at O⁰C• Ozone has shown a 30% decrease in

Antarctica since first measured• Polar stratospheric clouds: South pole winds

amplify “hole” in ozone in spring

Hazards of Depletion

Human issues: sunburns, cataracts, skin cancer,crop damage, reduction in fish populations Environmental issues: damage tophytoplankton, UV-sensitive trees

Legislation

• Clean Air Act (1970): est. national standards for allowable concentration of 6 outdoor pollutants & industrial standards for 189 pollutants

• Montreal Protocol (1987): international agreement to reduce CFCs, halons, methyl bromide (to reduce ozone depletion)

• Kyoto Protocol (2005): proposed that industrialized countries reduce greenhouse gases, by 2012, but disagreements over developed and developing countries’ responsibilities have quashed efforts to reach any agreement

FYI: Exam Tip

• Global warming and stratospheric ozone depletion are not the same environmental issue!

Be sure you know the similarities and differences

Exam Focus• Layers of atmosphere -which one traps heat radiated from earth

(greenhouse layer) -which one has ozone layer (not smog) -which one has photochemical smog -location of mesosphere• Primary pollutants- traits, sources, effects -CO, CO₂ -SO₂ -N₂, NO₂ -VOCs

Exam Focus

• Secondary pollutants- traits, sources, effects -ozone/photochemical smog *highest in morning -sulfuric, nitric acids -PANS -CFCs/Montreal Protocol• Indoor air pollutants- sources, effects -radon -asbestos -CO

Exam Focus• Reducing acid deposition• Prevention of pollutants -scrubber (function)• Heat island, temperature inversion (typical

location)• Anthropogenic greenhouse gases• Effects of increased UV radiation• Legislation: Clean Air, Kyoto Protocol

goal/failure

The atmosphere is the key symbol of global interdependence. Margaret Meade.

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