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Air Pollution

Air Pollution. Composition. Nitrogen: 78.1% Oxygen: 20.9% Other Gases: Argon : 0.9% CO 2 : ~ 370 ppm: Green House Gas Methane: Green House Gas Ozone: blocks UV radiation Dust: solid particles in the atmosphere Water Vapor: a major player in atmospheric circulations

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Air Pollution

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  1. Air Pollution

  2. Composition • Nitrogen: 78.1% • Oxygen: 20.9% • Other Gases: • Argon : 0.9% • CO2 : ~370 ppm: Green House Gas • Methane: Green House Gas • Ozone: blocks UV radiation • Dust: solid particles in the atmosphere • Water Vapor: a major player in atmospheric circulations • Since water vapor is lighter than the atmosphere. Introduction of water vapor causes vertical movement (convection) in the atmosphere

  3. Structure • Troposphere: 0-11 km elevation, the weather layer, temp. drops with elevation • Tropopause • Stratosphere 11-45 km, little vertical motion, contains ozone layer, Temp rises with elevation • Stratopause • Mesosphere: >45 km

  4. Ambient Air Pollution: • Ground level tropospheric air pollution. It is air pollution all around us. • Criteria Air Pollution: • Originated with the Clean Air Act of 1970 • EPA identified six most serious pollutant in the ambient air • CO, O3, SO2, NO, PM (particulate matter) and Pb (Lead) • VOC (Volatile Organic Pollutants):

  5. Criteria Air Pollutant • These are produced in large amounts – hence higher risk • Exhausts from motor vehicles account for about half of these emissions • In many major cities, criteria air pollutants cause eye and respiratory irritation, head ache and other ailments.

  6. Outdoor Pollution • Indoor Pollution • Primary Pollution • Secondary Pollution

  7. Carbon Monoxide (CO) • Product of incomplete combustion of carbon • Accounts for 50% of all air pollutants • Accounts for 11% of all hospital admission of elderly patients for congestive heart failure • Iron atom in hemoglobin in blood picks up oxygen from lungs and takes it to the cells. CO has 250 X more affinity for the iron atom compared to Oxygen • Organs get less oxygen: heart and brain gets affected first • Headache dizzinessfatigue, drowsiness  coma  death • US ambient air standard for CO is 9 ppm averaged over 8 hours. If it exceeds one time in a year , the area is violating standards.

  8. Ground level Ozone • Ozone O3 has three oxygen atoms • Major component of photochemical smog (which also contain nitrates and nitrogen oxides) • Nox + VOC  (Sunlight, High Temp, stagnant air O3 • Automobiles are the main producers of precursors, also power plants, aeroplanes • EPA considers Ozone as the “most … intractable air pollutant in urban areas”. • Effects on People: see the table • Effects on Plants and trees: causes more damage to plants than all other air pollutants combined • Crop loss in USA 5-10% • World wide 35% of the crops grow in areas with high O3 • More harmful when combined with other pollutants like acid rain • Trees and forests are also adversely affected

  9. Ozone is a major component of SMOG • Smog = unhealthy mixtures of air pollutants over urban areas 1. Industrial (gray air) smog = industries burn coal or oil 2. Photochemical (brown air) smog = Produced by light-driven reactions of primary pollutants & normal atmospheric compounds • Irritates eyes, noses, and throats • Vehicle inspection programs in the U.S. have decreased smog Nitrogen oxides (give it brown hazy color) + VOCs + heat + sunlight = O3 + other photochemical oxidants + aldehydes

  10. 17.16 Industrial smog Photochemical smog

  11. Ozone Levels

  12. How to reduce Ozone pollution? • Reduce NOx and VOC emissions from Automobiles • 1970 CAA – emissions fell 90% • But more autos and increased miles driven = high Nox and VOC • New Ozone standard • Low VOC and NOx does not necessarily reduce O3 • Between 1990 to 1992, # of cities in US exceeding old O3 standard (<.12 ppm) fell from 97 to 56 • Reduced emissions from power plants, vapor recovery nozzles in Gas stations, cleaner burning gasoline • Restricting Formaldehyde emissions because Formaldehyde causes more O3 formation than other VOCs • New EPA standard : 0.08 ppm – 1/3rd of US cities do not comply even with the old standard (0.12 ppm) – LA has > 0.20 ppm on 30 -40 days

  13. Sulfur Gases • >50 million tons of SO2 emitted worldwide • 2/3rd from combustion of coal in power plants • Rest mostly from Petroleum refining, smelting • Natural Sources: sea water, bacteria, planktons, plants • Volcanic eruption: Mt Pinatubo (1991) ejected 20 million tons – caused global cooling

  14. Sulfur dioxide (SO2) • SO2 gas reacts with moisture to form sulfuric acid which causes irritation and aggravates asthma, heart disease. Mucous membrane in eye, lungs affected • Forms aerosols (suspension of fine liquid or solid particles in air) of sulfuric acid (wet condition) or sulfates (dry condition) – can inflame lungs if inhaled • Environmental Effects: • Forms blue haze that blocks sunlight • Causes acid deposition (acid rain) • Harms stratospheric O3

  15. Nitrogen Oxides (NOx) • NO (nitric oxide), NO2 (nitrogen dioxide), N2O (nitrous oxide) • Sources: at high temp atmospheric N2 combines with O2 • Motor vehicles (50%), Electric utilities (25-30%), industrial furnaces (14%) • Natural sources: Lightning, soil microbes, volcanoes • Same as SO2: irritation, haze, acid rain, global cooling, ozone destruction • But also is precursor of Ozone formation – SO2 is not • Deposited on earth acts as a plant nutrient – can be very harmful in high concentrations

  16. Particulate Matter (PM) • Solids suspended in air • Accounts for 10% of US air pollution • Can vary in composition and size • Sulfates, nitrates, metals, dust, biological matters • Gaseous pollutants can condense into PMs • Caused silicosis, black lung diseases (coal miners), mesothelioma from asbestos • Coarser PM can be sneezed out, PM 10 is regulated by EPA, PM 2.5 even more dangerous--- can cause inflamation in Lungs. Very fine PM can cause cancer • Causes Haze , lowers visibility– can cause other problems

  17. Sources: • PM10 = dust from farms, mines, or roads, pollens • PM2.5 = mostly from combustions– diesel motor vehicles, electric power plants, industrial operations like steel mills, fly ash • Construction sites, agricultural activities, wood burning stoves • Chloride salts in coastal areas

  18. EPA standard : • PM10 < 50 μg/m3. PM2.5 <15 μg/m3 • PM2.5 contains different chemicals in east coast comapred to west coast • We don’t know which component is most harmful • Sulfates, nitrates, soot, metal oxides? • Controlling combustion sources

  19. Lead • Causes Brain damage, nervousness, apathy • Inner city children more at risk • Tetraethyl Lead was used as a octane booster in gasoline • Lead was used in paints • Now both use banned with dramatic reduction of lead in atmosphere and in average blood levels • Lead mobilized many years ago is still a problem: • Old paints, solder of old water pipes, roadside soil contaminated by leaded gasoline… • Other pollutants like Hg, Cd, Pb, Zn, As can be of concern near mines and smelters

  20. Volatile Organic Chemicals (VOC) • Combustion sources: Motor vehicles, aeroplanes, farm machineries, lawn mowers.. • Incomplete combustion, idling • Evaporation during filling of gas tanks • Non-combustion sources: • Petroleum refineries, chemical plants • Dry cleaners • Paint shops, garages, print shops • Bakeries – emit ethanol formed by action of yeast • Sewage treatment plants, composting • Natural Sources: Trees emit VOCs. 90% of VOCs in Maine is from Trees. • Terpene can contribute to Ozone formation • Reducing VOC emission: CAA – VOC dropped by 30% between 1970 and 1985

  21. Acid Rain • Any rain more acidic than normal rain (pH=5). Carbonic, Sulfuric and Nitric acids • SO2 dissolves in water to form Sulfuric acid: main ingredient of acid rain. NOx Nitric acid. CO2 Carbonic acid • Industrialized areas more affected. pH=4.2 in US Northeast • In the United States, roughly 2/3 of all SO2 and 1/4 of all NOx come from electric power generation that relies on burning fossil fuels, like coal.  • Granitic terrains more affected than limestone terrains • Affects plant growth, contaminates lakes and groundwater, man made structures, cause algal blooms, releases heavy and toxic metals from sediments

  22. Acid deposition • Originates from burning fossil fuels that release sulfur dioxide and nitrogen oxides • These compounds react with water to form sulfuric and nitric acids

  23. Acidic precipitation in the U.S.

  24. Acid Deposition: Effect of Life in Water

  25. US emission of criteria pollutants, 2006 • In 2006, the U.S. emitted 137 million tons of the 6 major pollutants

  26. Health Effects • Respiratory diseases = damage to tissue (asthma, bronchitis, emphysema) • ½ of all lungs examined in autopsies in US show damage • Lead to lung cancer • Heart disease, immune suppression, reduced mental function • 1 in 5 people live with dangerously polluted air • Reduced life expectancy • 5-10 yrs if you live in LA (150 days of hazardous breathing) • 24, 000 people/yr die in the US Los Angeles, CA

  27. Air pollution has decreased since 1970 • Total emissions of the 6 monitored pollutants have declined • Cap-and-trade program for SOx. • Enabled the 110 most polluting power plants to buy and sell SO2 pollution rights. • But CO2 emissions have been increasing

  28. Areas in the U.S. fail air quality standards

  29. Ozone Hole Ozone is harmful at Ground levelAt 15 km above surface UV ray reacts with Oxygen to produce Ozone. This Ozone absorbs UV ray and shields earth’s surface • 1% reduction in ozone causes 3% rise in skin cancer in light-skinned people plus increased cataract, melanoma, gene mutation, immune system damages UVA: longest wavelength: not damagingUVC: shortest wavelength: highly damaging, absorbed by oxygenUVB: intermediate wavelength: absorbed by Ozone

  30. Destruction of Ozone • Ozone in the upper atmosphere can be destroyed by the exhaust of hi-altitude aircrafts and more seriously by • CFCs(Chlorofluorocarbons) which were used as a refrigerant and in aerosol spray cans (e.g., Freon) • 40 billion lbs of CFC produced since 1931 and 90% of this released to the atmosphere • The released CFC either dissolves in seawater or go into Troposphere where they remain for many decades and are harmless • Some of the CFC escape to stratosphere, absorb UV ray and releases Chlorine which act as a catalyst to break Ozone molecule

  31. Destruction of Ozone • Chlorine + Ozone = ClO(Chlorine Monoxide) + O2 • A single chlorine atom can destroy 100,000 ozone molecules • ozone hole is more pronounced in polar regions • In polar stratosphere, extreme cold removes nitrogen compounds, which normally inactivate chlorine, from the stratosphere • Release of reactive chlorine is also catalyzed by fine ice crystals in stratosphere • At present both the Arctic and Antarctic are affected by ozone hole • Sulfate aerosols as from Mt Pinatubo also destroys Ozone layer

  32. Ozone Hole • UV rays reaching Antarctica each spring has increased from 20 to 200% every year since 1980s • Production of algae and bacteria in contact with seawater has decreased by 15% since the late 1980s • Marine Phytoplanktons are severely stressed • This in turn, will affect animals higher in the food chain.

  33. Ozone Hole

  34. Ozone Hole over Antarctica and N. America

  35. Present scenario • Montreal Protocol (1987, 1990) • Signed by more than 70 nations • Stipulates phasing out of CFCs and other ozone depleting compounds by 2000 • Hesitancy on part of China • Substitutes not totally safe • Latest data indicate that ozone hole is not expanding

  36. CO2 needs to be added to the list! In the US… • Not regulated as a pollutant under the U.S. Clean Air Act. • But most emissions are CO2 • A greenhouse gas • Contributes to global climate change

  37. Sources of C02 • US emissions • 40 % Petroleum products • 34 % coal • 20 % natural gas

  38. Greenhouse Effect • In a greenhouse, light enters but IR cannot escape • CO2 in atmosphere allows light rays to enter but traps IR • CO2 % in atmosphere has increased from 280 ppm in pre-Industrial time to present day value of 375.64 ppm (2003 data)

  39. Rise in atmospheric CO2 in the last two decades

  40. Greenhouse Effect: Is it Real? • How much CO2=How much rise of T? • More T = more evaporation = more cloud = Less Temp… • Real rise or natural fluctuation? • Data for the last 10ka indicate upto 6 °C fluctuation • Little ice age (1450 – 1850)

  41. Global Temperature Rise Methane (CH4) concentration ppb

  42. Other Greenhouse Gases • Methane, water vapor, nitrous oxide • Rice paddy, extraction of fossil fuel, raising of live stock (bovine flatulence) cause increase in methane • Cutting of forests kills CO2 sink • Some effects might be opposite of CO2: SO2 • Temperate regions more resilient • Colder climate will have longer growing season • Marginal areas to be hard hit • More flooding, heat waves…

  43. Greatest air pollution problem: Global Warming • www.nelson.wisc.edu/outreach/energy2006

  44. Evidence to Support Global Warming • Intergovernmental Panel on Climate Change (IPCC) • An international panel of scientists and government officials established in 1988 • Generated reports on the synthesis of scientific information concerning climate change • 4th Assessment report 2007 • Documents observed trends in surface temperature, precipitation patterns, snow and ice cover, sea levels, storm intensity • The IPCC concluded that it is more than 90% likely that most global warming is due to humans • The Debate over climate change is over • 84% of people surveyed think humans contribute to global warming • Predicts future changes

  45. Temperatures will rise 0.2 degree Celsius per decade

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