Composition of the Atmosphere

Primary Pollutants – methane, ozone, dust particles, microorganisms, and chlorofluorocarbons (CFC’s)

Causes of Primary Pollutants – factories, cars, wind and soil, volcanoes, forest fires, pollen, decaying plants, salt particles from the sea, and refrigerants.

Major Air Pollutants

Carbon oxides: Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials.

93% of carbon dioxide (CO2) in the troposphere occurs as a result of the carbon cycle.

7% of CO2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels).

• It is not regulated as a pollutant under the U.S. Clean Air Act.

Major Air Pollutants

Nitrogen oxides and nitric acid: Nitrogen oxide (NO) forms

• Nitrogen and oxygen gas in air react at the high-combustion temperatures in automobile engines and coal-burning plants.

• NO can also form from lightening and certain soil bacteria.

• NO reacts with air to form NO2.

• NO2 reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3

-) which are components of acid deposition.

Major Air Pollutants

Sulfur dioxide (SO2) and sulfuric acid:

About 1/3 of SO2 in the troposphere occurs naturally through the sulfur cycle.

2/3 come from human sources, mostly combustion (S+ O2 SO2) of sulfur-containing coal and from oil refining and smelting of sulfide ores.

SO2 in the atmosphere can be converted to sulfuric acid (H2SO4) and sulfate salts (SO4

2-) that return to earth as a component of acid deposition.

Major Air Pollutants

Suspended particulate matter (SPM):Consists of a variety of solid particles and liquid droplets small and light enough to remain suspended in the air.

The most harmful forms of SPM are fine particles (PM-10, with an average diameter < 10 micrometers) and ultrafine particles (PM-2.5).

According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S.

Major Air Pollutants

Ozone (O3):

Is a highly reactive gas that is a major component of photochemical smog.

It can • Cause and aggravate respiratory illness.

• Can aggravate heart disease.

• Damage plants, rubber in tires, fabrics, and paints.

Major Air Pollutants

Volatile organic compounds (VOCs):Most are hydrocarbons emitted by the leaves of many plants and methane.

About two thirds of global methane emissions comes from human sources.

Other VOCs include industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride.

• Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.

Major Air Pollutants

Radon (Rn):Is a naturally occurring radioactive gas found in some types of soil and rock.

It can seep into homes and buildings sitting above such deposits.

Secondary Pollutants

Form when primary pollutants react

Outdoor Air Pollution Secondary pollutants

• Harmful chemical formed when primary pollutants react with one another or with the basic components of air.

Fig. 17-4 p. 421

URBAN OUTDOOR AIR POLLUTION

Industrial smog: mixture of sulfur dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted mostly by burning coal.

In most developed countries where coal and heavy oil is burned, industrial smog is not a problem due to reasonably good pollution control or with tall smokestacks that transfer the pollutant to rural areas.

Photochemical ReactionPhotochemical ReactionPhotochemical ReactionPhotochemical Reaction• any chemical reaction any chemical reaction activated by lightactivated by light

Photochemical SmogPhotochemical Smog– a mixture of primary and secondary a mixture of primary and secondary

pollutants formed under the influence of pollutants formed under the influence of sunlightsunlight

Brown Air SmogBrown Air Smog

((NN22 + O + O2 2 2NO) high temps 2NO) high temps

(2NO + O(2NO + O22 2NO 2NO22))

NONO2 2 (yellowish brown gas)(yellowish brown gas)

Industrial SmogIndustrial Smog

• Gray SmogGray Smog– Comes from Comes from

burning coalburning coal

Sulfur DioxideSulfur Dioxide Sulfuric AcidSulfuric Acid

+ ParticulatesParticulates• Unburned CarbonUnburned Carbon

Fig. 17-8 p. 426Fig. 17-8 p. 426

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.

Figure 19-4Figure 19-4

Factors Influencing Levels of Outdoor Air Pollution

Outdoor air pollution can be reduced by:settling out, precipitation, sea spray, winds, and chemical reactions.

Outdoor air pollution can be increased by:urban buildings (slow wind dispersal of pollutants)

mountains (promote temperature inversions)

high temperatures (promote photochemical reactions).

Temperature Inversions

Cold, cloudy weather in a valley surrounded by mountains can trap air pollutants (left).

Areas with sunny climate, light winds, mountains on three sides and an ocean on the other (right) are susceptible to inversions.

Figure 19-5Figure 19-5

Fig. 19-5, p. 447

Warmer air Descending warm air mass

Inversion layer Inversion layer

Sea breezeIncreasing altitude

Decreasing temperature

ACID DEPOSITION

Sulfur dioxides, nitrogen oxides, and particulates can react in the atmosphere to produce acidic chemicals

ACID DEPOSITION

Acid deposition consists of rain, snow, dust, or gas with a pH lower than 5.6.

Figure 19-6Figure 19-6

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 Lakes in deep

soil high in soil high in limestone are limestone are

bufferedbuffered

Lakes in shallow Lakes in shallow soil low in limestone soil low in limestone

become acidicbecome acidic

ACID DEPOSITION

pH measurements in relation to major coal-burning and industrial plants.

Figure 19-7Figure 19-7

Acid Deposition and HumansAcid Deposition and Humans

• Respiratory diseasesRespiratory diseases

• Toxic metal leaching into drinking waterToxic metal leaching into drinking water

• Decreased atmospheric visibilityDecreased atmospheric visibility

• Damage to structures, especially Damage to structures, especially containing limestonecontaining limestone

• Decreased productivity and profitability Decreased productivity and profitability of fisheries, forests, and farmsof fisheries, forests, and farms

Acid Deposition and Aquatic SystemsAcid Deposition and Aquatic Systems

• Fish declinesFish declines– pH <4.5pH <4.5

• Undesirable Undesirable speciesspecies

• Aluminum Aluminum toxicitytoxicity

• Acid ShockAcid Shock– Sudden runoffSudden runoff

Acid Deposition, Plants, and SoilAcid Deposition, Plants, and Soil

Nutrient leaching

Nutrient leaching

Heavy metal release

Heavy metal release

Weakens trees Weakens trees

Fig. 17-15 p. 432Fig. 17-15 p. 432

ACID DEPOSITION

Figure 19-8Figure 19-8

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

Solutions

Acid Deposition

Prevention Cleanup

Reduce air pollution by improving energy efficiency

Add lime to neutralize acidified lakes

Reduce coal use

Add phosphate fertilizer to neutralize acidified lakes

Increase natural gas use

Increase use of renewable energy resources

Burn low-sulfur coal

Remove SO2 particulates & NOx from smokestack gases

Remove NOx from motor vehicular exhaust

Tax emissions of SO2

Air Quality is better in US; EPA estimates since 1970

Particulate Matter (PM)- down 78%

Carbon Dioxide (CO2)- down 23%

Nitrogen Dioxide (Nox)- up 14%

Lead (Pb)- down 98%

Sulfur Dioxide (SO2)- down 32%

Air quality is worse in developing countries:

Mexico City & Beijing: air exceeds WHO standards 350 days/year

INDOOR AIR POLLUTION

Indoor air pollution usually is a greater threat to human health than outdoor air pollution.

According to the EPA, the four most dangerous indoor air pollutants in developed countries are:

Tobacco smoke.

Formaldehyde.

Radioactive radon-222 gas.

Very small fine and ultrafine particles.

Indoor Air PollutionSick Building Syndrome

Fig. 17-17

p. 434

Chloroform

Benzo--pyrene

Styrene

Radon-222

Methylene Chloride

Tobacco Smoke

Carbon Monoxide

Asbestos

Nitrogen Oxides

1, 1, 1-Trichloroethane

Particulates

FormaldehydeTetrachloroethylene

Para-dichlorobenzene

Fig. 19-11, p. 453

INDOOR AIR POLLUTION

Household dust mites that feed on human skin and dust, live in materials such as bedding and furniture fabrics.

Can cause asthma attacks and allergic reactions in some people.

Radon

Radon-222

Associated with uranium (U-238) and organic material in rocks

2nd leading cause of lung cancer

4 picocuries

EPA proposed standard

Fig. 17-18

p. 436

HEALTH EFFECTS OF AIR POLLUTION

Normal human lungs (left) and the lungs of a person who died of emphysema (right).

Figure 19-15Figure 19-15

Air Pollution is a Big Killer

Each year, air pollution prematurely kills about 3 million people, mostly from indoor air pollution in developing countries.

In the U.S., the EPA estimates that annual deaths related to indoor and outdoor air pollution range from 150,000 to 350,000.

According to the EPA, each year more than 125,000 Americans get cancer from breathing diesel fumes.

Air Pollution is a Big Killer

Spatial distribution of premature deaths from air pollution in the United States.

Figure 19-16Figure 19-16

Fig. 19-19, p. 460

Solutions

Motor Vehicle Air Pollution

Prevention Cleanup

Emission control devices

Mass transit

Bicycles and walking

Less polluting engines

Less polluting fuels

Improve fuel efficiency

Car exhaust inspections twice a year

Get older, polluting cars off the road

Give buyers large tax write-offs or rebates for buying low-polluting, energy efficient vehicles

Stricter emission standards

Using the Marketplace to Reduce Outdoor Air Pollution

To help reduce SO2 emissions, the Clean Air Act authorized an emission trading (cap-and-trade) program.

Enables the 110 most polluting power plants to buy and sell SO2 pollution rights.

Between 1990-2002, the emission trading system reduced emissions.

In 2002, the EPA reported the cap-and-trade system produced less emission reductions than were projected.

Solutions: Reducing Outdoor Air Pollution

There are a of ways to prevent and control air pollution from coal-burning facilities.

Electrostatic precipitator: are used to attract negatively charged particles in a smokestack into a collector.

Wet scrubber: fine mists of water vapor trap particulates and convert them to a sludge that is collected and disposed of usually in a landfill.

Solutions: Reducing Outdoor Air Pollution

There are a # of ways to prevent and control air pollution from motor vehicles.

Because of the Clean Air Act, a new car today in the U.S. emits 75% less pollution than did pre-1970 cars.

There is and increase in motor vehicle use in developing countries and many have no pollution control devices and burn leaded gasoline.

Indoor Air Pollution

Little effort has been devoted to reducing indoor air pollution even though it poses a much greater threat to human health than outdoor air pollution.

Environmental and health scientists call for us to focus on preventing air pollution (especially indoor) in developing countries.

Fig. 19-20, p. 461

Solutions

Indoor Air Pollution

Prevention

Cover ceiling tiles & lining of AC ducts to prevent release of mineral fibers

Use adjustable fresh air vents for work spaces

Increase intake of outside airBan smoking or limit it to well ventilated areas

Change air more frequently

Set stricter formaldehyde emissions standards for carpet, furniture, and building materials

Circulate a building’s air through rooftop green houses

Prevent radon infiltration Use exhaust hoods for stoves and appliances burning natural gasUse office machines in well

ventilated areas

Use less polluting substitutes for harmful cleaning agents, paints, and other products

Install efficient chimneys for wood-burning stoves

Cleanup or Dilution

Can US Air Pollution Laws Be Improved….hmmm?

Can US Air Pollution Laws Be Improved….hmmm?

• Continue to rely mostly on pollution cleanup rather than prevention.

• Fail to increase fuel-efficiency standards for cars and light trucks.

• Not adequately regulating emissions from inefficient two-cycle gasoline engines.

• Do little to reduce emissions of carbon dioxide and other greenhouse gases.

The Next StepsThe Next Steps

• Integrating government policies for energy and air pollution.

• Improving energy efficiency.• Relying more on lower-polluting and

more climate-benign natural gas.• Increasing use of renewable energy.• Regulating the air quality for an

entire region or airshed with primary emphasis on prevention.