Chapter 19 Air Pollution

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.  Some lichen species are sensitive to specific air-polluting chemicals.  Because lichens are widespread, long-lived, and anchored in place, they can help track pollution to its source. Figure 19-1

STRUCTURE AND SCIENCE OF THE ATMOSPHERE  The atmosphere consists of several layers  The troposphere is made up mostly of nitrogen and oxygen, with smaller amounts of water vapor and CO 2.  Ozone in the stratosphere filters out most of the sun’s harmful UV radiation. Figure 19-2

AIR POLLUTION  Some primary air pollutants may react with one another or with other chemicals in the air to form secondary air pollutants. Figure 19-3

Major Air Pollutants  Carbon oxides: Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials. Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials. 93% of carbon dioxide (CO 2 ) in the troposphere occurs as a result of the carbon cycle. 93% of carbon dioxide (CO 2 ) in the troposphere occurs as a result of the carbon cycle. 7% of CO 2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels). 7% of CO 2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels).

Major Air Pollutants  Nitrogen oxides and nitric acid: Nitrogen oxide (NO) forms when nitrogen and oxygen gas in air react at the high-combustion temperatures in automobile engines and coal- burning plants. Nitrogen oxide (NO) forms when 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 can also form from lightening and certain soil bacteria. NO reacts with air to form NO 2.NO reacts with air to form NO 2. NO 2 reacts with water vapor in the air to form components of acid deposition.NO 2 reacts with water vapor in the air to form components of acid deposition.

Major Air Pollutants  Sulfur dioxide (SO 2 ) and sulfuric acid: 1/3 of SO 2 in the troposphere occurs naturally through the sulfur cycle. 1/3 of SO 2 in the troposphere occurs naturally through the sulfur cycle. 2/3 of SO 2 comes from human sources, 2/3 of SO 2 comes from human sources, Coal,oil refining and smelting of sulfide ores.Coal,oil refining and smelting of sulfide ores. SO 2 in the atmosphere can be converted to sulfuric acid (H 2 SO 4 ) and sulfate salts (SO 4 2- ) that return to earth as acid rain SO 2 in the atmosphere can be converted to sulfuric acid (H 2 SO 4 ) and sulfate salts (SO 4 2- ) that return to earth as acid rain

Major Air Pollutants  Suspended particulate matter (SPM): Solid particles and liquid droplets small and light enough to remain suspended in the air. Solid particles and liquid droplets small and light enough to remain suspended in the air. According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S. According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S.

Major Air Pollutants  Ozone (O 3 ): Highly reactive gas that is a major component of photochemical smog. Highly reactive gas that is a major component of photochemical smog. It can It can Cause and aggravate respiratory illness.Cause and aggravate respiratory illness. Can aggravate heart disease.Can aggravate heart disease. Damage plants, rubber in tires, fabrics, and paints.Damage plants, rubber in tires, fabrics, and paints.

Major Air Pollutants  Volatile organic compounds (VOCs): Hydrocarbons emitted by the leaves of many plants and methane. Hydrocarbons emitted by the leaves of many plants and methane. About 2/3 of global methane emissions comes from human sources. About 2/3 of global methane emissions comes from human sources. Other VOCs include industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride. 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.Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.

Major Air Pollutants  Radon (Rn): Naturally occurring radioactive gas found in some types of soil and rock. Naturally occurring radioactive gas found in some types of soil and rock. It can seep into homes and buildings sitting above such deposits. It can seep into homes and buildings sitting above such deposits.

Sunlight plus Cars = Photochemical Smog  Photochemical smog-a mixture of air pollutants formed by the reaction of NOX and VOCs with sunlight  Mexico City has some of the worst air pollution in world Figure 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. 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), and high temperatures (promote photochemical reactions). urban buildings (slow wind dispersal of pollutants), mountains (promote temperature inversions), and 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 19-5

ACID DEPOSITION  Sulfur dioxides, nitrogen oxides, and particulates can react in the atmosphere to produce acidic chemicals that can travel long distances before returning to the earth’s surface. Tall smokestacks reduce local air pollution but can increase regional air pollution. Tall smokestacks reduce local air pollution but can increase regional air pollution.

ACID DEPOSITION  Acid deposition consists of rain, snow, dust, or gas with a pH lower than 5.6. Figure 19-6

Fig. 19-6, p. 448 Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Wet acid depostion (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) Nitric oxide (NO) Sulfur dioxide (SO 2 ) and NO Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Acid fog Farm Ocean Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic

ACID DEPOSITION  Acid deposition contributes to chronic respiratory disease and can leach toxic metals (such as lead and mercury) from soils and rocks into acidic lakes used as sources for drinking water.

ACID DEPOSITION Figure 19-8

ACID DEPOSITION  Air pollution is one of several interacting stresses that can damage, weaken, or kill trees and pollute surface and groundwater. Figure 19-9

Fig. 19-9, p. 451 Emissions SO 2 NO x Acid deposition H2O2H2O2 O3O3 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 uptake Acids Lake Groundwater PANs

Fig , p. 452 Solutions Acid Deposition PreventionCleanup 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 SO 2 particulates & NO x from smokestack gases Remove NO x from motor vehicular exhaust Tax emissions of SO 2

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. Tobacco smoke. Formaldehyde. Formaldehyde. Radioactive radon-222 gas. Radioactive radon-222 gas. Very small fine and ultrafine particles. Very small fine and ultrafine particles.

Chloroform Benzo-  -pyrene Styrene Radon-222 Methylene Chloride Tobacco Smoke Carbon Monoxide Asbestos Nitrogen Oxides 1, 1, 1- Trichloroethane Particulates FormaldehydeTetrachloroethylene Para-dichlorobenzene Fig , 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. Can cause asthma attacks and allergic reactions in some people. Figure 19-12

Air Pollution is a Big Killer  Each year, air pollution prematurely kills about 3 million people, mostly from indoor air pollution in developing countries.  Normal human lungs (left) and the lungs of a person who died of emphysema (right).

PREVENTING AND REDUCING AIR POLLUTION  The Clean Air Acts in the United States have greatly reduced outdoor air pollution from six major pollutants: Carbon monoxide Carbon monoxide Nitrogen oxides Nitrogen oxides Sulfur dioxides Sulfur dioxides Suspended particulate matter (less than PM-10) Suspended particulate matter (less than PM-10)

PREVENTING AND REDUCING AIR POLLUTION  Environmental scientists point out several deficiencies in the Clean Air Act: The U.S. continues to rely on cleanup rather than prevention. The U.S. continues to rely on cleanup rather than prevention. The U.S. Congress has failed to increase fuel- efficiency standards for automobiles. The U.S. Congress has failed to increase fuel- efficiency standards for automobiles. Regulation of emissions from motorcycles and two-cycle engines remains inadequate. Regulation of emissions from motorcycles and two-cycle engines remains inadequate. There is little or no regulation of air pollution from oceangoing ships in American ports. There is little or no regulation of air pollution from oceangoing ships in American ports.

PREVENTING AND REDUCING AIR POLLUTION Airports are exempt from many air pollution regulations. Airports are exempt from many air pollution regulations. The Act does not regulate the greenhouse gas CO 2. The Act does not regulate the greenhouse gas CO 2. The Act has failed to deal seriously with indoor air pollution. The Act has failed to deal seriously with indoor air pollution. There is a need for better enforcement of the Clean Air Act. There is a need for better enforcement of the Clean Air Act. Executives of companies claim that correcting these deficiencies would cost too much, harm economic growth, and cost jobs. Executives of companies claim that correcting these deficiencies would cost too much, harm economic growth, and cost jobs.

Using the Marketplace to Reduce Outdoor Air Pollution  To help reduce SO 2 emissions, the Clean Air Act authorized an emission trading (cap-and- trade) program. Enables the 110 most polluting power plants to buy and sell SO 2 pollution rights. Enables the 110 most polluting power plants to buy and sell SO 2 pollution rights. Between , the emission trading system reduced emissions. Between , the emission trading system reduced emissions. In 2002, the EPA reported the cap-and-trade system produced less emission reductions than were projected. 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. Electrostatic precipitator: are used to attract negatively charged particles in a smokestack into a collector.

Solutions: Reducing Outdoor Air Pollution  There are a of ways to prevent and control air pollution from coal- burning facilities. 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. 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.

Fig , p. 459 Solutions Stationary Source Air Pollution Prevention Burn low-sulfur coal Disperse emissions above thermal inversion layer with tall smokestacks Remove sulfur from coal Convert coal to a liquid or gaseous fuel Remove pollutants after combustion Shift to less polluting fuels Tax each unit of pollution produced Dispersion or Cleanup

Fig , p. 460 Solutions Motor Vehicle Air Pollution PreventionCleanup 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