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Environmental Science: Toward a Sustainable Future Richard T. Wright Atmospheric Pollution PPT by Clark E. Adams Chapter 21
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Atmospheric Pollution Air-pollution essentials Major air pollutants and their sources Impacts of air pollutants: health and environment Bringing air pollution under control Unresolved issues
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Incorrect Assumptions about Air Pollutants There are threshold levels of tolerable air pollutants Dilution is the solution to air pollution Air pollutants can be assimilated by nature Air pollutants do not travel Air pollution accidents will not happen
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Pollutants and Atmospheric Cleansing Air pollutants: gases and aerosols in the atmosphere that have harmful effects Level of air pollution determined by: The amount of pollutants entering the air The amount of space into which the pollutants dispersed Mechanisms that remove pollutants from the air
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The Hydroxyl Radical: Nature’s Cleanser
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The Appearance of Smog
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Impacts of Smog: Temperature Inversion
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Air Pollution Effects Adversely affects human health Damages crops and forests Highly corrosive
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Major Air Pollutant Sources
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Major Air Pollutants: Primary (see next slide) Primary pollutants derived directly from burning fuels and wastes Particulates Hydrocarbons Carbon monoxide Nitrogen oxides Sulfur dioxides
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Major Pollutants: Secondary (see next slide) Secondary air pollutants derive from reactions that occur between primary pollutants and other atmospheric chemicals Ozone PANs Acids: sulfuric and nitric
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Comparison of Growth vs. Emissions
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Acid Deposition
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pH Scale Acid precipitation = pH <5.5 pH = measurement of H + ions in solution
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Major Sources of SO 2 Emitters
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Impacts of Air Pollutants on Human Health Chronic: gradual deterioration of a variety of physiological functions over a period of years Acute: life-threatening reactions within a period of hours or days Carcinogenic: cancer-causing
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The Respiratory System
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Impacts of Air Pollutants on the Environment Plants Necrotic: kills plant cells Chlorotic: destroys chlorophyll, reducing photosynthesis Increases susceptibility to disease and pests Ozone most serious pollutant
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Ozone Impact on Crop Yields
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Impacts of Air Pollutants on the Environment Forests Leaching of nutrients Release of aluminum into solution Rapid changes in soil chemistry Reduced growth and diebacks of plants and animals
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Impacts of Air Pollutants on the Environment Forests Increased plant vulnerability to natural enemies Increased soil erosion Increased flooding Increased sedimentation of waterways
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Impacts of Air Pollutants on the Environment Materials Loss of color Oxidation Corrosion Decreased real estate values
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Effects of Acid Deposition Alteration of plant and animal reproduction Leaching of other toxic elements, e.g., aluminum Eutrophic to oligotrophic conditions Total loss of biota from aquatic ecosystems Alterations of food chains
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Trends in Automobile Emissions
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Impact of Buffers on Acid Deposition
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Unresolved Issues Costs versus benefits of air pollution control Status of “new source” review and enforcement Improving fuel efficiency – hybrid cars Improving mass transit systems Reducing commuting distances
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Bringing Air Pollution under Control Clean Air Act identifies most widespread pollutants: e.g., particulates, SO, CO, NO, lead = criteria pollutants National Ambient Air Quality Standards (NAAQS) set levels that protect environmental and human health
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Bringing Air Pollution under Control NAAQS: also set national ambient air quality standards National Emission Standards for Hazardous Air Pollutants set national emission standards for hazardous air pollutants
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Control Strategies Command-and-control: regulate air pollution so criteria pollutants remain below primary standard level Lack of enforcement and compliance 37% reduction of air pollutants Forced compliance with state implementation plan (SIP)
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Title IV Clean Air Act 1990 Reduce SO emissions 50% below 1980 levels Improve methods of reducing SO emissions Allow emissions allowances and trading Emissions purchases Reduce NO emissions
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Industry’s Response to Title IV Fuel switching Scrubbers Emissions allowance trading Using low-sulfur coals
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End of Chapter 21
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