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The atmosphere is the key symbol of global interdependence. Margaret Meade.

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Presentation on theme: "The atmosphere is the key symbol of global interdependence. Margaret Meade."— Presentation transcript:

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2 The atmosphere is the key symbol of global interdependence. Margaret Meade

3 Air Pollution Chapter 18

4 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)

5 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

6 Fig. 19-2, p. 440 Atmospheric pressure (millibars) Temperature Thermosphere Pressure Mesopause Heating via ozone Mesosphere Stratopause Altitude (kilometers) Stratosphere Altitude (miles) Tropopause Ozone “layer” Heating from the earth Troposphere Temperature (˚C) Pressure = 1,000 millibars at ground level (Sea level)

7 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

8 Fig. 19-3, p. 442 COCO 2 SO 2 NONO 2 Most hydrocarbons SO 3 Most suspended particles HNO 3 H2O2H2O2 O3O3 PANs Most NO 3 – and SO 4 2– salts Sources NaturalStationary Mobile H 3 SO 4

9 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)

10 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.

11 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 (CO 2 ) -93% results from carbon cycle -7% results from human activities (mostly burning fossil fuels) Health issues: asthma, COPD, heart attacks, headache, death

12 Major Air Pollutants (cont’d) Nitrogen oxides: gas which form 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

13 Major Air Pollutants (cont’d) (Human issues: discussed later) (Environmental issues: discussed later)

14 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)

15 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)

16 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

17 Major Air Pollutants (cont’d) FYI: According to EPA, SMA is responsible for about 60,000 premature deaths/year in the US alone

18 Major Air Pollutants (cont’d) Volatile organic compounds (VOCs): Primary pollutant; most are hydrocarbons emitted many plants, some are methane ⅔ of global VOC methane emissions come from fossil fuel leaks, rice paddies, others include solvents- trichlorethylene (TCE), benzene, and vinyl chloride (dry-cleaning, paints) Health issues: cancer, blood disorders, immune system damage

19 Major Air Pollutants (cont’d) Lead (Pb) Primary pollutant; doesn’t break down in environment Released from lead additives in gas, peeling lead- based paint (both banned in US in ‘70’s) Health issues: brain damage, mental retardation, partial paralysis, blindness, death (WHO estimates that million children are at risk of lead poisoning worldwide)

20 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

21 Core Case Study: When Is a Lichen Like a Canary? Some lichen species are sensitive to specific air- polluting 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.

22 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

23 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

24 Fig. 19-6, p. 448 Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Wet acid depostion (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) Nitric oxide (NO) Sulfur dioxide (SO 2 ) and NO Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Acid fog Farm Ocean Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic

25 Acid Deposition Figure 19-8

26 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

27 Fig. 19-9, p. 451 Emissions SO 2 NO x Acid deposition H2O2H2O2 O3O3 Others Direct damage to leaves & bark Reduced photo- synthesis and growth Susceptibility to drought, extreme cold, insects, mosses, & disease organisms Soil acidification Tree death Leaching of soil nutrients Release of toxic metal ions Root damage Reduced nutrient & water uptake Acids Lake Groundwater PANs

28 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

29 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)

30 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

31 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

32 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

33 Factors Influencing Outdoor Pollution Reducing pollution: 1.Particles heavier than air settle out 2.Rain, snow partially cleanse air 3.Sea spray washes out air from ocean 4.Winds mix polluted and unpolluted air 5.Chemical reactions (sulfur, nitrates) form acids which fall to earth

34 Factors Influencing Outdoor Pollution Increasing pollution: 1.Heat island: urban buildings block air flow (reduce dilution of pollutants) 2.High temperatures promote photochemical smog 3.VOCs from thick urban forests promote p. s. 4.Grasshopper effect- movement of pollutants from tropics to poles

35 Factors Influencing Outdoor Pollution 5.Temperature inversion: layer of warm air sits over cooler, polluted air; prevents cool air from rising and dispersing pollutants - occurs in cities surrounded by mountains (think L A)

36 Fig. 19-5, p. 447 Warmer air Descending warm air mass Inversion layer Sea breeze Increasing altitude Decreasing temperature

37 Case Study: South Asia’s Massive Brown Cloud A huge dark brown cloud of industrial smog, caused by coal-burning in countries such as China and India, stretches over 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.

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39 Indoor Air Pollution Usually a greater threat to health than outdoor air pollution May go undetected Problem increases with poor ventilation

40 Major Indoor Pollutants 4 most dangerous indoor pollutants (according to EPA): Tobacco smoke Formaldehyde Radioactive radon-222 gas Very small fine and ultrafine particles

41 Tobacco Smoke Contains 70 carcinogens (including filter), 250 toxins 2 nd -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

42 Formaldehyde Found in common building materials (plywood, particleboard, wallpaper, carpet) Known carcinogen Health issues: headaches, respiratory tract, irritation, sore throats, dizziness, nausea, cancer Remediation: substitute formaldehyde-free materials, increase building ventilation

43 Radon-222 Colorless, odorless gas Produced by natural radioactive decay of uranium 238 Can seep from ground into cracks in foundations Health issues: alpha particles damage lungs, leads to lung cancer (2 nd leading cause of cancer) Remediation: Sealing cracks in foundations, increase ventilation

44 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 Sources and paths of entry for indoor radon-222 gas. Figure 19-13

45 Fine Particles Bacteria, viruses, pollen, dust, mildew, mold, yeast 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”)

46 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

47 Other Pollutants Carbon monoxide -accumulates in enclosed spaces -results from inefficient combustion in gas heaters, stoves Health issues: headache, nausea, death Asbestos -mineral once used in insulation, ceiling and floor tiles Health issues: skin and lung irritant, lung cancer

48 FYI Remember: earth absorbs heat from sun and releases heat back into the atmosphere where its trapped by gases in the troposphere- greenhouse effect -effect is natural and necessary to maintain the right temp for life -human activities leading to an increase in the greenhouse effect is the problem

49 Global Climate Change 4 major anthropogenic greenhouse gases: CO₂ Nitrous oxide (N₂O) Methane (CH₄) Chlorofluorocarbons (CFCs)

50 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

51 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

52 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

53 Global Climate Change (cont’d) CFCs- molecules of chlorine & fluorine -Cl breaks off in stratosphere, breaks down an ozone molecule (1 Cl ion may react with 1 x 10⁵ ozone molecules) Sources: once used in refrigerants, fumigants, propellants in aerosol cans -deplete ozone -lingers in atmosphere, not water soluble Remediation: Montreal Protocol phased out CFCs

54 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…

55 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)

56 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)

57 Effects of Climate Change (cont’d) Changing vegetative zone: temperature increases will move zones northward. -threatens food security -increase in plant extinction rates Biodiversity loss: -animals must find vegetation- migrate or die (arctic species are most vulnerable since there is nowhere to migrate)

58 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…

59 Stratospheric Ozone and UV Rays 3 types of UV radiation: A, B, C (A is least energetic, C is most energetic) -UV B is of most concern to us Ozone shields earth from UV radiation -O₂ is broken down by UV radiation -free O reacts with more O molecule to form O₃ (back and forth exchange of O and O₃ shields earth from UV radiation)

60 Ozone Depletion First proposed by Rowland & Molina, 1970 (not widely accepted until the 80’s) -ozone is measured in Dobson units (DU): 1 DU = ozone column 0.01 mm thick at O⁰C Ozone has shown a 30% decrease in Antarctica since first measured Polar stratospheric clouds: South pole winds amplify “hole” in ozone in spring

61 Hazards of Depletion Human issues: sunburns, cataracts, skin cancer, crop damage, reduction in fish populations Environmental issues: damage to phytoplankton, UV-sensitive trees

62 Legislation Clean Air Act (1970): est. national standards for allowable concentration of 6 outdoor pollutants & industrial standards for 189 pollutants Montreal Protocol (1987): international agreement to reduce CFCs, halons, methyl bromide (to reduce ozone depletion) Kyoto Protocol (2005): proposed that industrialized countries reduce greenhouse gases, by 2012, but disagreements over developed and developing countries’ responsibilities have quashed efforts to reach any agreement

63 FYI: Exam Tip Global warming and stratospheric ozone depletion are not the same environmental issue! Be sure you know the similarities and differences

64 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

65 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

66 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


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