ENV200 Chapter 10 Notes

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School of Environment
Romila Verma

CHAPTER 10 – AIR POLLUTION [10.2] AIR POLLUTION AND THE CLIMATE ­ Physical processes in the atmosphere transport, concentrate, and disperse air pollutants ­ Global warming demonstrates the interaction between anthropogenic pollutants and the atmosphere Air pollutants travel the globe ­ Dust and fine aerosols can be carried great distances by the wind o Dust can carry pathogens o Places usually considered among the cleanest in the all have heavy metals, pesticides, and radioactive elements in the air ­ Circulation of the atmosphere tends to transport contaminants toward the poles o Volatile compounds (VOCs) evaporate from warm areas, travel through the atmosphere, then condense and precipitate in cooler regions o Contaminants migrate to the coldest places at high latitudes and bioaccumulate in food chains  Top carnivores in polar regions have dangerously high levels of pesticides, metals, and other hazardous air pollutants in their bodies  Inuit people have higher levels of polychlorinated biphenyls (PCBs) in their blood Carbon dioxide and halogens are key greenhouse gases ­ Respiration emissions of CO2is balanced by an equal uptake by photosynthesis in green plants o Respiration = oxidation of organic compounds by plant and animal cells ­ CO 2s non-toxic and innocuous at normal concentrations ­ CO 2evels are increasing due to human activities and causing global climate change ­ Regulating CO2has been a subject of intense debate o On the one hand, policy makers have widely acknowledged that climate change is likely to have disastrous effects o On the other hand, CO 2s difficult to consider limiting because we produce abundant quantities, because reductions involve changes to both technology and behavior, and because CO production is closely tied to economic productivity 2  Congress argues that pollution monitoring and regulation is too costly  Energy companies have lobbied to prevent legal limits on greenhouse gases ­ EPA is responsible for regulating six greenhouse gases (e.g., carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride) o Greenhouse gases endanger public health and welfare within the meaning of the Clean Air Act o Three of the six gases contain halogens  Halogens = a group of lightweight, highly reactive elements (e.g., F, Cl, Br, I)  More potent than CO 2  Toxic in elemental forms  Commonly used in industrial and commercial products  Destroys the ozone layer that protects the earth from UV radiation ­ Ways to reduce emissions of greenhouse gases o Reducing fuel use through conservation and alternative energy o Changing subsidy systems that support coal burning o Cap-and-trade system = a market for trading in emission rights or “credits”  Most popular strategy CFCs destroy ozone in the stratosphere ­ Ozone hole = a thinning of ozone concentrations in the stratosphere o Produced by  Long-range pollution transport  Chemical reactions of atmospheric gases and pollution o Caused by  Chlorine-based aerosols  Chlorofluorocarbons (CFCs)  Hydrochlorofluorocarbons (HCFCs)  Non-toxic, non-flammable, chemically inert, long-lasting, and cheaply produced  Used as industrial gases, and in refrigerators, air conditioners, Styrofoam insulation, aerosol spray cans  Antarctica's cold winter temperatures  Circumpolar vortex = strong winds that circle the pole during the winter months o Isolate the Antarctic air o Allow stratospheric temperatures to drop low enough to create ice crystals at high altitudes, which absorb ozone and chlorine-containing molecules  During the spring months, the sun provides energy to liberate chlorine ions from chlorine-containing molecules, which readily binds with ozone, and ozone is broken down to molecular oxygen o Causes rapid ozone destruction o Chlorine ions are not consumed in reactions with ozone, so they continue to destroy ozone for years, until they precipitate or wash out of the air  During the summer months, temperatures warm slightly, circumpolar vortex weakens, and air from warmer latitudes mixes with Antarctic air o Replenishes ozone concentrations in the ozone hole ­ Ozone (O 3 o Pollutant near the ground because it irritates skin and plant tissues o Valuable in the stratosphere because it is effective at absorbing UV radiation  UV radiation damages plant and animal cells, potentially causing mutations that produce cancer  UV exposure reduces agricultural production and disrupts ecosystems (e.g., reducing populations of plankton) o Re-forms naturally, but not as fast as it is destroyed CFC control has had remarkable success ­ Montreal Protocol = the first of several major international agreements on phasing out most use of CFCs (e.g., halons, carbon tetrachloride, methyl chloroform) by 1996 o CFCs and related compounds are powerful and long-lasting greenhouse gases o Alternative to CFCs  HCFCs, which release much less chlorine per molecule  HFCs o Successful in eliminating CFC production  CFC production in most industrialized countries has sharply decreased  CFCs are being removed from the atmosphere more rapidly than they are being added ­ Scientists hope to eventually develop halogen-free molecules [10.4] AIR POLLUTION CONTROL ­ Dilution has long characterized the main approach to air pollution control, but is no longer an effective strategy The best strategy is reducing production ­ Most air pollution in the developed world is associated with transportation and energy production ­ Most effective strategy would be conservation (e.g., reducing electricity consumption, insulating homes and offices, better public transportation, more alternative energy) ­ Particulate removal = filter air emissions from power plants o Filters trap particulates in effluent gas in cotton cloth, spun gla
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