Composition of the Atmosphere Primary Pollutants methane ozone

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 (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). • 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 highcombustion temperatures in automobile engines and coal-burning plants. • NO can also form from lightening and certain soil bacteria. • NO reacts with air to form NO 2. • NO 2 reacts with water vapor in the air to form nitric acid (HNO 3) and nitrate salts (NO 3 -) which are components of acid deposition.

Major Air Pollutants Sulfur dioxide (SO 2) and sulfuric acid: About 1/3 of SO 2 in the troposphere occurs naturally through the sulfur cycle. 2/3 come from human sources, mostly combustion (S+ O 2 SO 2) of sulfur-containing coal and from 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 42 -) 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 (O 3): 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 Ø 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 Reaction • any chemical reaction activated by light Photochemical Smog – a mixture of primary and secondary pollutants formed under the influence of sunlight Brown Air Smog (N 2 + O 2 2 NO) high temps (2 NO + O 2 2 NO 2) NO 2 (yellowish brown gas)

Industrial Smog • Gray Smog – Comes from burning coal _Sulfur Dioxide _Sulfuric Acid + Particulates • Unburned Carbon Fig. 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 -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 -5

Descending warm air mass Warmer air Inversion layer Sea breeze Increasing altitude Decreasing temperature Fig. 19 -5, p. 447

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 p. H lower than 5. 6. Figure 19 -6

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

ACID DEPOSITION p. H measurements in relation to major coalburning and industrial plants. Figure 19 -7

Acid Deposition and Humans • • Respiratory diseases Toxic metal leaching into drinking water Decreased atmospheric visibility Damage to structures, especially containing limestone • Decreased productivity and profitability of fisheries, forests, and farms

Acid Deposition and Aquatic Systems • Fish declines – p. H <4. 5 • Undesirable species • Aluminum toxicity • Acid Shock – Sudden runoff

Acid Deposition, Plants, and Soil Ø Nutrient leaching Ø Heavy metal release Ø Weakens trees Fig. 17 -15 p. 432

ACID DEPOSITION Figure 19 -8

Emissions SO 2 Acid H O 2 2 deposition PANs NOx O 3 Others Reduced photosynthesis and growth Direct damage to leaves & bark Tree death Soil acidification Leaching of soil nutrients Acids Lake Groundwater Release of toxic metal ions Susceptibility to drought, extreme cold, insects, mosses, & disease organisms Root damage Reduced nutrient & water uptake

Solutions Acid Deposition Prevention Reduce air pollution by improving energy efficiency Cleanup Add lime to neutralize acidified lakes Reduce coal use Increase natural gas use Increase use of renewable energy resources Burn low-sulfur coal Remove SO 2 particulates & NOx from smokestack gases Remove NOx from motor vehicular exhaust Tax emissions of SO 2 Add phosphate fertilizer to neutralize acidified lakes

Air Quality is better in US; EPA estimates since 1970 Particulate Matter (PM)- down 78% Carbon Dioxide (CO 2)- down 23% Nitrogen Dioxide (Nox)- up 14% Lead (Pb)- down 98% Sulfur Dioxide (SO 2)- 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 Pollution Sick Building Syndrome Fig. 17 -17 p. 434

Chloroform Para-dichlorobenzene Tetrachloroethylene Formaldehyde 1, 1, 1 Trichloroethane Styrene Nitrogen Oxides Benzo-a-pyrene Particulates Tobacco Smoke Asbestos Carbon Monoxide Radon-222 Methylene Chloride 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-222 Associated with uranium (U-238) and organic material in rocks 2 nd 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 -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 -16

Solutions Motor Vehicle Air Pollution Prevention Mass transit Bicycles and walking Cleanup Emission control devices 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 Fig. 19 -19, p. 460

Using the Marketplace to Reduce Outdoor Air Pollution To help reduce SO 2 emissions, the Clean Air Act authorized an emission trading (capand-trade) program. Enables the 110 most polluting power plants to buy and sell SO 2 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 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 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.

Solutions Indoor Air Pollution Prevention Cover ceiling tiles & lining of AC ducts to prevent release of mineral fibers Ban smoking or limit it to well ventilated areas Set stricter formaldehyde emissions standards for carpet, furniture, and building materials Prevent radon infiltration Use office machines in well ventilated areas Use less polluting substitutes for harmful cleaning agents, paints, and other products Cleanup or Dilution Use adjustable fresh air vents for work spaces Increase intake of outside air Change air more frequently Circulate a building’s air through rooftop green houses Use exhaust hoods for stoves and appliances burning natural gas Install efficient chimneys for wood -burning stoves Fig. 19 -20, p. 461

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 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.