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Chapter 18

Chapter 18. Air Pollution. Lichens. alga/fungus some are sensitive to specific pollutants (e.g. SO2). Atmosphere. 1. troposphere (surface - 11mi): 78% N2, 21% O2, <1% Ar, .036% CO2, .01 - 5% H2O a) tropopause: temperature abruptly rises

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Chapter 18

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  1. Chapter 18 Air Pollution

  2. Lichens alga/fungus • some are sensitive to specific pollutants (e.g. SO2)

  3. Atmosphere 1. troposphere (surface - 11mi): 78% N2, 21% O2, <1% Ar, .036% CO2, .01 - 5% H2O a) tropopause: temperature abruptly rises b) each layer ends when temp gradient reverses) 2. stratosphere (11-30 mi) 1000x less water, 1000x more O3

  4. 3. mesosphere (30 - 50 mi) 4. thermosphere (50 - 75 mi) 5. human impact on nutrient cycle a) we add 1/4 as much CO2 to atm as nature does b) we add 3x as much NOx (from fossil fuels, fertilizer) c) SO2 from fossil fuels

  5. Air pollutants (wrong chemical in the wrong place at the wrong concentration) 1. primary pollutants: formed at surface of the earth 2. secondary pollutants: formed from reactions in troposphere 3. motor vehicles produce more pollution than any other activity

  6. Photochemical smog • a) mix of primary and secondary pollutants influenced by sunlight • NOx + VOC’s + light -----> O3 + aldehydes + PAN’s + HNO3 Note: formaldehyde: H - C = O I H • PAN’s: peroxyacyl nitrates

  7. Mechanism • surface: N2 + O2 ---> 2NO (primary) • (at high temp: auto engines, boilers) 2 NO + O2 ---> 2 NO2 3 NO2 + H2O ---> 2 HNO3 + NO NO2 + UV ----> NO + O O + O2 ----> O3 O + O3 + CxHy ----> aldehydes O2 + hydrocarbons + NO2 ----> PAN’s

  8. Animation Acid deposition animation. Click to view animation.

  9. Photochemical oxidants • NO2, O3, PAN’s - b/c they are strong oxidizers (take electrons away) 1. common in warm, sunny climate with lots of cars - NO,NO2 concentrations increase as traffic builds and unburned hydrocarbons rise and react , in sunlight, to produce photochemical smog (peaks in afternoon)

  10. Animation Formation of photochemical smog. Click to view animation.

  11. Industrial Smog • 1. Combo of SO2, H2SO4 droplets, suspended particles • 2. Burning coal, oil • S+O2--->SO2 • SO2+O2--->SO3 • SO3+H2O--->H2SO4 • NH3+H2SO4--->(NH4)2SO4, a particulate solid

  12. Figure 17-16Page 433 Prevention Cleanup Reduce air pollution by improving energy efficiency Add lime to neutralize acidified lakes Add phosphate fertilizer to neutralize acidified lakes Reduce coal use Increase natural gas use Increase use of renewable resources Burn low-sulfur coal Remove SO2 particulates, and NOx from smokestack gases Remove Nox from motor vehicular exhaust Tax emissions of SO2

  13. Temperature Inversion • Warm air mass gets trapped above cooler air mass (acts as a lid), so surface air can’t rise and dilute pollutants • Early morning surface air is cool, clouds block sun so ground stays cool, upper air is warmer so there is no convection current • Tends to happen in cities located in a valley (like Los Angeles)

  14. Figure 17-9 (1)Page 427 Increasing altitude Decreasing temperature Warmer air Inversion layer Cool layer Mountain Mountain Valley

  15. Figure 17-10Page 428 Wind Transformation 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 deposition (droplets of H2SO4 and HNO3 dissolved in rain and snow) Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Sulfur dioxide (SO2) and NO Nitric oxide (NO) Acid fog Farm Ocean Lakes in shallow soil low in limestone become acidic Lakes in deep soil high in limestone are buffered

  16. Figure 17-12Page 429 Potential problem areas because of sensitive soils Potential problem areas because of air pollution: emissions leading to acid deposition Current problem areas (including lakes and rivers)

  17. Indoor air pollution 1. sick building syndrome- def: 20% of occupants get better when they go outside 2. most dangerous indoor pollutants: smoke, formaldehyde, asbestos, radon

  18. Asbestos 1) best to wrap it 2) 1998, foam invented that binds fibers together, nontoxic, still fireproof

  19. radon - 222 1) produced by radioactive decay of U - 238 2) outside diperses, indoors collects 3) radon is 55% of radiation dose in US 4) acceptable dose? 4 - 20 picocuries/L • NOTE: 1 Ci = 3.7 x 1010 disintegrations/s • a 1g sample of radium has this activity 1 rad is the absorption of 10-5 joule per gram of tissue

  20. Effects of air pollution on living organisms • humans 1. CO takes up receptor site in hemoglobin so molecule cannot transport O2 2. 1997 study by World Bank and WHO says 2.7 million people die each year from air pollution (2.2 million from indoor pollution) • plants 3. air pollution (esp O3) can break down waxy coating on leaves a) water loss, loss of protection from pests and frost, etc

  21. aquatic life 4. acid shock = sudden runoff of highly acidic water and consequently, aluminum ions a) can kill fish and inhibit reproduction, stimulates excessive mucus clogging fish gills b) mildly eutrophic lake can turn into a clear blue oligotrophic lake c) 16,00 lakes in Norway and Sweden have no fish due to xs acidity

  22. materials • 5. soot and grit ---> cleaning costs • a) paint, roofs • b) marble statues, historic buildings • c) damage to buildings = $5 billion in US

  23. Natural Defense • Soil containing Ca2+, Mg2+ salts (buffering ions) can neutralize acid rain to a certain extent • Limestone, CaCO3 deposits

  24. Solutions 1. laws: clean air acts of 1970, 1977, 1990 have led to federal regulations a) clean air act requires EPA to set national emission standards for toxic air pollutants (302) compounds) standards not met b) stricter car emission standards by 2002 c) required cleaner burning fuel (oxygenated) in 9 cities, including Philadelphia

  25. d) Clean Air Act is successful b/w 1970 and 1997 air pollutants levels have dropped 31% e) problems with Clean Air Act of 1990 1) relies on cleanup not prevention 2) no tightening of emission standards for cars and light trucks 3) no restriction of fine particles 4) municipal trash incinerators get 30 year leases 5) weak incinerator emission standards

  26. market place a) power plants in 20 states may buy and sell SO2 emission rights b) SO2 credits may be solod and ised in the future c) b/w 1994-1997 SO2 emissions dropped by 30% d) emission credits are also proposed for NOx

  27. Particulate reduction a) electrostatic precipitator, baghouse filter, cyclone seperator and wet scrubber are technologies b) catalytic converter: 2 NO + 2 CO ----> N2 + CO2 c) 50% of emission control systems have been disabled (estimate) d) controls are needed for outboard motors, lawn mowers, etc e) b/w 1982 and 1993, US smog levels dropped by 8%

  28. Figure 17-23 (4)Page 442 Cleaned gas Dirty gas Wet gas Clean water Dirty water Wet Scrubber

  29. Figure 17-23 (1)Page 442 Cleaned gas Electrodes Dust discharge Dirty gas Electrostatic Precipitator

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