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The atmosphere is the key symbol of global interdependence. Margaret Meade Air Pollution Unit 14 Nature of the Atmosphere • Thin layer of gases surrounding earth • Density (air mass/air volume) is greater at sea level than in mountains • Atmospheric pressure (force/area) decreases with altitude • 78% nitrogen, 21% oxygen (water vapor, argon, CO₂) Layers of Atmosphere • Troposphere: layer closest to earth (extends 11 miles above surface) -responsible for weather, climate, greenhouse effect • Stratosphere: layer surrounding troposphere (extends 30 miles above troposphere) -ozone layer: protects earth from too much of sun’s UV radiation Atmospheric pressure (millibars) Temperature Pressure Thermosphere Heating via ozone Mesosphere Stratopause Stratosphere Altitude (miles) Altitude (kilometers) Mesopause Tropopause Ozone “layer” Heating from the earth Troposphere (Sea level) Temperature (˚C) Pressure = 1,000 millibars at ground level Fig. 19-2, p. 440 Air Pollution (all environmental problems involve the air) • Primary air pollutants: released directly from a source into the atmosphere -natural sources: dust, wildfires, volcanoes -manmade sources: primarily burning of fossil fuels, burning of biofuels -may be stationary or moving CO CO2 SO2 NO NO2 Most hydrocarbons Most suspended particles Sources Natural SO3 HNO3 H3SO4 H2O2 O3 PANs Most NO3– and SO42– salts Stationary Mobile Fig. 19-3, p. 442 Air Pollutants (cont’d) • Secondary pollutants: product of reactions between primary pollutants and other chemicals in the atmosphere -prevailing winds carry pollution from source to other areas -responsible for hundreds of millions of lung problems (WHO) FYI: Exam Tip • Be specific in identifying types of pollution. Simply stating that an activity results in “pollution” won’t earn you points. Exemplar: Burning wood for fuel produces CO and is a major source of indoor air pollution in developing countries. Major Air Pollutants Carbon oxides: colorless, odorless, toxic (prevents O₂ from binding with red blood cell) • Carbon monoxide (CO) -incomplete burning of carbon-based matter (tobacco, forest fires, vehicles, factories) -catalytic converters remove CO from vehicle exhaust • Carbon dioxide (CO2) -93% results from carbon cycle -7% results from human activities (mostly burning fossil fuels) Health issues: asthma, COPD, heart attacks, headache, death Major Air Pollutants (cont’d) Nitrogen oxides: gas which forms when N₂ combines with O₂ • Nitrogen dioxide: reddish brown gas -forms photochemical smog in cities • Nitric acid -”acid rain”/acid deposition • Nitrous oxide (N₂O) -greenhouse gas emitted from burning animal waste, fossil fuel Major Air Pollutants (cont’d) (Human issues: discussed later) (Environmental issues: discussed later) Major Air Pollutants (cont’d) Sulfur dioxide; sulfuric acid • ⅓ comes from sulfur cycle • ⅔ comes from combustion of coal, oil refining • Scrubbers: remove SO₂ from coal smoke by combining it with calcium carbonate (sludge deposited in landfills) (Health issues: discussed later) (Environmental issues: discussed later) Major Air Pollutants (cont’d) Ground-level (tropospheric) Ozone (O₃) • Secondary pollutant • Major part of photochemical smog • Unstable, strong oxidant (sheds O to become O₂) Health issues: irritates eyes, lungs, heart Environmental issues: damages plants, fabrics, paints, rubber in tires (Remember: ozone in the stratosphere is good; ozone in the troposphere is harmful) Major Air Pollutants (cont’d) Suspended Particulate Matter (SPM/PM-10) • Primary pollutant- solid, liquid “droplets” less than 10mm in diameter • Emitted from burning coal/dung, plowing, tobacco smoke, vehicles • Includes mercury, cadmium (toxic heavy metals) • Electrostatic precipitator: removes particles from smoke (negative charge on particle makes it stick to a positive plate; sludge is dumped in landfill) Health issues: irritates eyes, lungs, can cause mutations, cancers (mercury, heavy metals) Environmental issues: reduces visibility, corrodes metals Major Air Pollutants (cont’d) FYI: According to EPA, SMA is responsible for about 60,000 premature deaths/year in the US alone Major Air Pollutants (cont’d) Volatile organic compounds (VOCs): • Primary pollutant; most are hydrocarbons emitted by natural and anthropogenic sources • ⅔ of global VOC methane emissions come from fossil fuel leaks, rice paddies • others sources include solvents- trichlorethylene (TCE), benzene, and vinyl chloride (dry-cleaning, paints) Health issues: cancer, blood disorders, immune system damage Major Air Pollutants (cont’d) Lead (Pb) • Primary pollutant; doesn’t break down in environment • Released from lead additives in gas, peeling leadbased paint (both banned in US in ‘70’s) Health issues: brain damage, mental retardation, partial paralysis, blindness, death (WHO estimates that 130-200 million children are at risk of lead poisoning worldwide) Core Case Study: When Is a Lichen Like a Canary? • Lichens can warn us of bad air because they absorb it as a source of nourishment. Figure 19-1 Core Case Study: When Is a Lichen Like a Canary? • Some lichen species are sensitive to specific airpolluting chemicals. • After Chernobyl, more than 70,000 reindeer had to be killed because they ate highly radioactive lichens • Because lichens are widespread, long-lived, and anchored in place, they can help track pollution to its source. Acid Deposition (Remember, oxides of sulfur and nitrogen can be further oxidized in the atmosphere to form acid precipitation- snow, sleet, rain, fog- and dry fallout in the form of particulates) • Sulfuric acid-H₂SO₄/sulfate salts-SO₄² • Nitric acid-HNO₃/nitrate salts-NO₃² Acid Deposition (cont’d) • Source: coal-burning plants, ore smelters • Create regional air pollution downwind from source (hundreds of miles away) • Wet deposition: acidic rain, fog, snow with pH less than 5.6 • Dry deposition: acidic particles • Buffers: some lime-containing soils that can neutralize acids, minimize effects of acid rain Wind Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3) Nitric oxide (NO) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Sulfur dioxide (SO2) and NO Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Wet acid depostion (droplets of H2SO4 and HNO3 dissolved in rain and snow) Acid fog Farm Ocean Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic Fig. 19-6, p. 448 Acid Deposition Figure 19-8 Effects of Acid Deposition Health issues: damages respiratory system, irritates eyes, threatens food security (concentrates heavy metals in fish, dissolves shells of mollusks, harms crops) Environmental issues: can leach aluminum, lead, cadmium from soil, which enters aquatic ecosystems, can leach nutrients out of soil *thin mountain soils are most vulnerable to damage Emissions SO2 Acid H O 2 2 deposition PANs NOx O3 Others Reduced photosynthesis and growth Direct damage to leaves & bark Tree death Soil acidification Leaching of soil nutrients Acids Susceptibility to drought, extreme cold, insects, mosses, & disease organisms Release of toxic metal ions Root damage Reduced nutrient & water uptake Lake Groundwater Fig. 19-9, p. 451 Results of Acid Deposition on Producers • Soil acidification: root damage, reduced nutrient/uptake • Direct damage to bark, leaves • Susceptibility to drought, cold, predation by insects Reducing Acid Rain • Reduce coal use (increase alternate fuels) • Use of scrubbers to reduce emissions from factories, vehicles • Add lime or phosphates to neutralize acidified lakes (expensive) Smog • Industrialized/Gray-air smog: suspended droplets of salts, soot that hangs in urban air -source: burning coal -major problem in China (16 of 20 most polluted cities) • Photochemical/Brown-air smog: mix of ozone, VOCs, NO, PANS (peroxyacyl nitrates) in urban air Smog (cont’d) • Photochemical/Brown-air smog: mix of ozone, VOCs, NO, PANS (peroxyacyl nitrates) in urban air -UV from sun causes NO to react with plant VOCs -increases with hotter, drier air FYI: Sunlight plus Cars Equals Photochemical Smog • Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog • LA , Salt Lake City also has smog issues. Figure 19-4 Factors Influencing Outdoor Pollution Reducing pollution: 1. Density of particles (settle out) 2. Rain, snow (partially cleanse air) 3. Sea spray (washes ocean air) 4. Winds (mix polluted and unpolluted air) 5. Chemical reactions (sulfur, nitrates form acids, which fall to earth) Factors Influencing Outdoor Pollution Increasing pollution: 1. Heat island: urban buildings block air flow (reduce dilution of pollutants) 2. High temperatures (pc smog) 3. VOCs from urban forests (pc smog) 4. Grasshopper effect- movement of pollutants from tropics to poles Factors Influencing Outdoor Pollution 5. Temperature inversion: layer of warm air sits over cooler, polluted air; prevents air from rising and dispersing pollutants - occurs in cities surrounded by mountains (think L A) Warmer air Inversion layer Descending warm air mass Inversion layer Case Study: South Asia’s Massive Brown Cloud • Huge cloud of industrial smog, caused by coalburning in countries such as China and India, • Covers much of southeastern Asia. – In areas beneath cloud, photosynthesis is reduced, interfering with crop development. – Fine particles and droplets in the cloud appear to be changing regional climates (including rainfall). • May have contributed to floods in 2002 and 2005 which killed thousands of people. Indoor Air Pollution • Usually a greater threat to health than outdoor air pollution • Increases with poor ventilation Major Indoor Pollutants 4 most dangerous indoor pollutants (according to EPA): • Tobacco smoke • Formaldehyde • Radioactive radon-222 gas • Very small fine and ultrafine particles FYI Tobacco Smoke • Contains 70 carcinogens (including filter), 250 toxins • 2nd-hand smoke is considered to be a leading risk to human health (from cigarettes) • Risk is magnified within enclosed spaces Health issues: cancer, heart disease, birth defects, emphysema Remediation: quit smoking, ban smoking in buildings, improve building ventilation Economic health cost in US: ≈$72 billion Formaldehyde • Found in common building materials (plywood, particleboard, wallpaper, carpet) • Known carcinogen Health issues: headaches, respiratory tract , irritation, sore throats, dizziness, nausea, cancer Remediation: use formaldehyde-free materials, increase building ventilation Radon-222 • Colorless, odorless gas • Radioactive decay of uranium 238 • Seeps from ground into foundations Health issues: alpha particles damage lungs, leads to lung cancer (2nd leading cause of cancer) Remediation: Sealing cracks in foundations, increase ventilation FYI: Radioactive Radon • Radon-222, a radioactive gas found in some soils and rocks, can seep into some houses and increase the risk of lung cancer. Sources and paths of entry for indoor radon-222 gas. Figure 19-13 Fine Particles Bacteria, viruses, pollen, dust, mildew, mold, • Circulate in heating, cooling systems • Can create sick-building syndrome Health issues: infectious disease, allergic reactions, headaches, irritated eyes and lungs, chronic fatigue Remediation: replace, disinfect air ducts or condemn building (1 in 5 commercial buildings in US is considered “sick”) FYI: Indoor Air Pollution • Household dust mites feed on human skin and dust; live in materials such as bedding and furniture fabrics. – Can cause asthma attacks/ allergic reactions in sensitive people. Figure 19-12 Other Pollutants • Carbon monoxide -results from inefficient combustion in gas appliances Health issues: headache, nausea, death • Asbestos -mineral once used in insulation, ceiling and floor tiles Health issues: skin and lung irritant, lung cancer Global Climate Change 4 major anthropogenic greenhouse gases: • CO₂ • Nitrous oxide (N₂O) • Methane (CH₄) • Chlorofluorocarbons (CFCs) ***global temperature increase 1°F*** Global Climate Change (cont’d) CO₂ Source: burning hydrocarbons -biggest contributor to greenhouse gases Remediation: -conservation of fossil fuels -switch to alternate fuels -sequester CO₂ in ground, plant trees, reduce deforestation Global Climate Change (cont’d) N₂O Sources: inorganic fertilizers, fossil fuels, sewage treatment, decomp of biowaste -lingers long time in atmosphere Remediation: -conservation of fossil fuels -decrease use of fertilizers Global Climate Change (cont’d) CH₄ Sources: cattle, fossil fuel mining, landfills, rice cultivation -primary pollutant & VOC -more potent than CO₂ Remediation: -capture for fuel -burning it Global Climate Change (cont’d) CFCs- molecules of chlorine & fluorine -Cl⁻ + O₃ → ClO + O₂ (1 Cl⁻ ion may react with 1 x 10⁵ ozone molecules) Sources: used in refrigerants, fumigants, propellants in aerosol cans -deplete ozone -not water soluble (stays in atmosphere) Remediation: Montreal Protocol phased out CFCs Effects of Climate Change • Sea level rise: thermal expansion of water, melting of land-based glaciers -degrades coastal wetlands, estuaries, reefs -saltwater intrusion -coastal flooding -positive feedback loop: exposed soil absorbs more heat, melts more snow… Effects of Climate Change (cont’d) • Melting of permafrost: (ground under tundra is a sink for CO₂, CH₄) -positive feedback loop: melting permafrost releases gases, increases heat in atmosphere… (TransAlaska pipeline is already showing signs of sustained damage due to permafrost melting) Effects of Climate Change (cont’d) • Extreme weather: severe drought, desertification, unusual snow events -positive feedback loop: fewer plants means more CO₂ in atmosphere… • Change in ocean currents: meltwater from Arctic circle may disrupt conveyor belt currents in N Atlantic (Gulfstream currents warm climate in Europe) Effects of Climate Change (cont’d) • Changing vegetative zone: temperature increases will move zones northward. -threatens food security -increase plant extinction rates • Biodiversity loss: -animals must find vegetation- migrate or die (arctic species are most vulnerable since there is nowhere to migrate) FYI: Atmosphere-Ocean Link • CO₂ is dissolved in huge amounts in the oceans • CO₂ forms carbonic acid in water so acidity in ocean increases • Increased acidity inhibits production of mollusk shells, coral • Warmer oceans will dissolve less CO₂, which means more in the atmosphere… Stratospheric Ozone and UV Rays • 3 types of UV radiation: A, B, C (A is least energetic, C is most energetic) -UV B/C is of most concern to us • Ozone shields earth from UV radiation -O₂ + UV → 2O (single oxygen) -O + O₂ → O₃ (back and forth exchange of O and O₃ shields earth from UV radiation) Ozone Depletion • First proposed by Rowland & Molina, 1970 -ozone measured in Dobson units (DU): 1 DU = ozone column 0.01 mm thick at O⁰C • Polar stratospheric clouds: South pole winds amplify “hole” in ozone in spring Hazards of Depletion Human issues: sunburns, cataracts, skin cancer, crop damage, reduction in fish populations Environmental issues: damage to phytoplankton, UV-sensitive trees Legislation • Clean Air Act (1970): est. national standards for allowable concentration of 6 outdoor/industrial pollutants • Montreal Protocol (1987): international agreement to reduce CFCs, halons, methyl bromide (to reduce ozone depletion) • Kyoto Protocol (2005): proposed a reduction in greenhouse gases, by 2012 (disagreements over developed and developing countries’ responsibilities have quashed efforts to reach an agreement) FYI: Exam Tip • Global warming and stratospheric ozone depletion are not the same environmental issue! Be sure you know the similarities and differences Exam Focus • Layers of atmosphere -which one traps heat radiated from earth (greenhouse layer) -which one has ozone layer (not smog) -which one has photochemical smog -location of mesosphere • Primary pollutants- traits, sources, effects -CO, CO₂ -SO₂ -N₂, NO₂ -VOCs Exam Focus • Secondary pollutants- traits, sources, effects -ozone/photochemical smog *highest in morning -sulfuric, nitric acids -PANS -CFCs/Montreal Protocol • Indoor air pollutants- sources, effects -radon -asbestos -CO Exam Focus • Reducing acid deposition • Prevention of pollutants -scrubber (function) • Heat island, temperature inversion (typical location) • Anthropogenic greenhouse gases • Effects of increased UV radiation • Legislation: Clean Air, Kyoto Protocol goal/failure