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Air Pollution

Air Pollution. Chapter 17. Atmospheric Chemistry Cycles and Residence Times. Atmosphere composition mostly Nitrogen (76.6 %), Oxygen (23.1 %), and other gases Chemical materials cycle through the atmosphere as they do in other reservoirs Residence Times (Table 17.1)

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Air Pollution

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  1. Air Pollution Chapter 17

  2. Atmospheric ChemistryCycles and Residence Times • Atmosphere composition mostly Nitrogen (76.6 %), Oxygen (23.1 %), and other gases • Chemical materials cycle through the atmosphere as they do in other reservoirs • Residence Times (Table 17.1) • Influenced by amounts present in a given reservoir • CO2 – 4 years • O2 - 7 million years • N2 – 44 million years

  3. Figure 17.1 The Global carbon cycle

  4. Cost of Air Pollution • Air pollution is costly • $40 billion – Worldwide annual expense of forest-product harvest reduction due to air pollution • $16 billion annual U.S. expense (direct costs) • Medical costs are enormous: • Illness • Medical treatment • Absenteeism • Loss of production

  5. Types of Air Pollution • Gaseous pollutants • CO and CO2 • SO2 • NO, NO2 • Ozone and CFCs • Particulates • Soot • Smoke • Ash (from burning coal) • Dust (released from industrial processes) • Other solids release by burning • From 35 million tons/year (mainly combustion) to 180 million tons/year (mostly industrial)

  6. Figure 17.2 Principal sources of U.S. air pollutants, 1998

  7. Figure 17.3 U.S. particulate emissions were controlled

  8. Carbon Gases • CO – carbon monoxide • Not very abundant in the atmosphere but deadly • Odorless, tasteless and invisible – toxic to animals • Very short residence time but easily added to the atmosphere by common anthropogenic sources (automobiles) • CO2 - carbon dioxide • Essential for life of plants (photosynthesis) • Product of plant respiration, combustion, and volcanic eruptions • Short residence time and easily fluxes between oceans and atmosphere

  9. Figure 17.1 The Global carbon cycle

  10. Figure 17.4 a Emissions of carbon monoxide

  11. Sulfur Gases • More than 50 million tons of sulfur dioxide (SO2) are emitted worldwide each year mainly from coal combustion • SO2 - sulfur dioxide forms acid rain • very short residence time (days or hours) • By product from combusting coal • SO2 + H2O + ½ O2 = H2SO4 (sulfuric acid) and will lower the pH scale for rain • Can contribute to acid rain causing lung and eye irritation • Becomes a contributor to water pollution

  12. Figure 17.4 b Emissions of sulfur dioxide

  13. Nitrogen Gases and “Smog Ozone” • Complex geochemistry • oxygen and nitrogen are very abundant in the atmosphere • high temperatures cause nitrogen and oxygen to form nitrogen oxide compounds • 2NO2 + H2O + ½ O2 = 2HNO2 (nitric acid) • NO2 + strong sun light will produce photochemical smog • NO2 can breakdown in sun light to NO and will react with common oxygen (O2) to form ozone (O3) • Ozone inhibits photosynthesis in plants and can cause severe medical problems to people in urban areas where abundant automobiles are in operation

  14. Figure 17.5 Nitrogen-gas emissions

  15. Fig. 17.06 substandard and near-ground ozone

  16. The Ozone Layer and Chlorofluorocarbons (CFCs) • Ozone (O3) is a ‘chemically out of place pollutant’ • In upper atmosphere (stratosphere) the ozone layer absorbs harmful ultraviolet radiation • Ozone forms as O2 + ½ O2 = O3 • At ground level it is very harmful to plants and animals • A thick ozone layer is beneficial to life on earth • Periodically, an ozone hole forms over either pole. This allows more ultra violet radiation to enter the lower atmosphere • CFCs attack ozone and can destroy, or thin, the ozone layer • CFCs build up their concentration in the upper atmosphere, have a residence time of about 100 years, and breakdown into various by-products including chlorine monoxide (ClO) • One ClO can destroy many ozone molecules

  17. Figure 17.7 Ozone layer

  18. Figure 17.8 a

  19. Figure 17.8 b

  20. Figure 17.9

  21. Figure 17.10

  22. Figure 17.11

  23. Figure 17.12

  24. Figure 17.13

  25. Figure 17.14

  26. Particulate Pollutants • Lead - once a serious pollutant • Used in gasoline as an antiknock additive, tons of lead were released into the atmosphere by internal combustion engines • Unleaded fuels have reduced lead in air pollution • High doses of lead can cause brain damage, depression, apathy, and other psychological disorders

  27. Figure 17.15 a

  28. Figure 17.15 b

  29. Acid Rain • Acidity is reported on the pH scale. • An acid solution has more Hydrogen-ions (H+) • A basic solution would have fewer • Acid rain has more acid than normal rain • Certain gases in the atmosphere will complex with atmospheric water plus oxygen to form acids • Acid rain is harmful to plants, health of rivers and lakes, and animals • Acid rain causes increases in the build up of heavy metals (lead, zinc, selenium, copper, and aluminum) leached from rocks and soils • Toxic levels are then found in our waterways, fish, and fish eaters

  30. Figure 17.16

  31. Figure 17.17

  32. Regional Variations in Rainfall Acidity and Impacts • Rain down wind of an industrial or populated areas have greater acidic conditions • Generally, industrial areas have notably higher sulfur dioxide emissions than non-industrial areas • Urban areas, with automobiles, generally have higher nitrogen oxide emissions than areas without autos • Local geology can reduce the acidity of waterways that receive acid rain. • Limestone can neutralize acidic water; granite can not

  33. Figure 17.18

  34. Air Pollution and Weather • Thermal Inversion • Pollutants released from ground sources generally are warmer than the surrounding air and tend to rise • As an air mass these plumes will rise and cool • In certain situations a cool air mass will have a warm air mass overlying it, it will trap the rising warm pollutant-bearing air mass; this condition is made worse by an air mass with stagnant conditions • As more pollutants are dumped into the cooler air mass they will become concentrated below the warm air mass • Eventually, the concentrations of pollutants may become very high and cause a health concern • Local topography – mountains, basins, valleys, and local wind patterns may amplify the situation also

  35. Figure 17.19 a

  36. Figure 17.19 b

  37. Figure 17.20

  38. Figure 17.21 a

  39. Figure 17.21 b

  40. Air Pollution and Weather • Air pollution can impact local weather • Reduce visibility • Reduce air quality • Modify air temperature • Produce acid rain • Produce abnormal rain

  41. Figure 17.22

  42. Air Pollution Control • Air Quality Standards – Clean Air Act (1970) • Designed to protect public health, clear the visible pollution in the air, and prevent damage to crops • Control Methods • Trapping or scrubbing emissions • conversion techniques that reduce the emission of harmful compounds to less harmful ones • Automobile Emissions – strong legislation creates the Environmental Protection Agency (EPA) • Goal to reduce automobile emissions • Limited success achieved by requiring the use of catalytic converters in new cars and increased fuel economy standards for all new cars • Cost and Effects – it has increased abatement and control cost while limited areas of success have occurred

  43. Fig. 17.23

  44. Figures 17.24 a and b

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