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Air Pollution • What controls the level? – Amount of pollutants entering the air. – Amount of space into which the pollutants are dispersed. – Mechanisms that remove pollutants from the air. • When is it a concern? – Exceed a threshold level – Threshold level depends on concentration and duration of exposure, i.e. dose. Dose = (concentration X exposure) Major Primary Pollutants 1. Suspended 5. Sulfur oxides particulate 6. Heavy metals matter 2. Volatile organic 7. Air toxics compounds (radon) 3. Carbon monoxide 4. Nitrogen oxides PANs = peroxyacetyl nitrates The Hydroxyl Radical: Nature’s Cleanser (?) Sources of These Emissions (Fig. 22-13)? 1) Sulfur dioxides A) Fuel combustion 2) Nitrogen oxides B) Transportation 3) VOC’s C) Industrial 4) Particulate matter processes 5) Carbon monoxide Emission Trends Air Pollution Effects • Adversely affects human health – Chronic – Acute – Carcinogenic • Damages crops and forests – Necrotic – Chlorotic – Disease and Pest Susceptibility • Damage to material & aesthetics – Corrosion – Oxidation – Smog Smog I Smog II Temperature Inversions Photochemical Oxidants (Troposphere Ozone and PANs Vehicles! Four Forms of Acid Deposition pH Scale pH = measurement of H ions in solution Acid precipitation = pH < 5.5 Acid Deposition in the U.S. 2/3 sulfuric 1/3 nitric Coal burning power plants Effects of Acid Deposition on Aquatic Ecosystems • Alteration of plant and animal reproduction • Leaching of other toxic elements, e.g., Al • Eutrophic to seemingly oligotrophic conditions • Total loss of biota from aquatic ecosystems • Alterations of food chains Effects of Acid Deposition on Forest Ecosystems • Leaching of nutrients • Release of aluminum into solution • Rapid changes in soil chemistry • Reduced growth and diebacks of plants and animals • Increased flooding • Increased plant vulnerability to natural enemies • Increased soil erosion • Increased sedimentation of waterways Ecosystems Impacts are Not Equal. Limestone Buffers Acid Deposition. Clean Air Act of 1970, 1977, 1990 • Identifies most widespread pollutants: e.g., particulates, SO, CO, NO, lead = criteria pollutants • Set ambient standards = levels that protect environmental and human health • Set national ambient air quality standards • Set national emission standards for hazardous air pollutants Title IV Clean Air Act 1990 • Reduce SO emission 50% below 1980 levels • Improve methods of reducing SO emissions • Allow emissions allowances and trading • Emissions purchases • Reduce NO emissions Future Responses to Air Pollution Control • Increase fuel efficiency • Emission-free vehicles • Improving mass transit systems • Reducing commuting distances What are some potential societal reactions to these control measures?
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