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Lecture 7. outdoor air pollution


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Lecture 7. outdoor air pollution

  1. 1. Outdoor Air Pollution
  2. 2. Outdoor Air Pollution CO CO2Primary Pollutants Secondary Pollutants SO2 NO NO2 SO3 Most hydrocarbons HNO3 H2SO4 Most suspended particles H2O2 O3 PANs Most NO3 and SO42 –salts – Natural Stationary Mobile
  3. 3. Major Classes of Air PollutantsClass ExamplesCarbon oxides Carbon monoxide (CO) and carbon dioxide (CO2)Sulfur oxides Sulfur dioxide (SO2) and sulfur trioxide (SO3) Nitric oxide (NO), nitrogen dioxide (NO2), nitrousNitrogen oxides oxide (N2O) (NO and NO2 often are lumped together and labeled NOx)Volatile organic compounds (VOCs) Methane (CH4), propane (C3H8), chlorofluorocarbons (CFCs)Suspended particulate matter (SPM) Solid particles (dust, soot, asbestos, lead, nitrate, and sulfate salts), liquid droplets (sulfuric acid, PCBs, dioxins, and pesticides)Photochemical oxidants Ozone (O3), peroxyacyl nitrates (PANs), hydrogen peroxide (H2O2), aldehydesRadioactive substances Radon-222, iodine-131, strontium-90, plutonium-239 (Table 3-1, p. 49)Hazardous air pollutants (HAPs), Carbon tetrachloride (CCl4), methyl chloridewhich cause health effects such as (CH3Cl), chloroform (CHCl3), benzene (C6H6),cancer, birth defects, and nervous ethylene dibromide (C2H2Br2), formaldehydesystem problems (CH2O2)
  4. 4. Major Outdoor Air PollutantsCARBON MONOXIDE (CO)Description: Colorless, odorless gas that is poisonous to air-breathinganimals; forms during the incomplete combustion of carbon-containingfuels (2 C + O2 2 CO).Major human sources: Cigarette smoking (p. 409), incompleteburning of fossil fuels. About 77% (95% in cities)comes from motor vehicleexhaust.Health effects: Reacts with hemoglobin in red blood cells and reduces theability of blood to bring oxygen to body cells and tissues. This impairsperception and thinking; slows reflexes; causes headaches, drowsiness,dizziness, and nausea; can trigger heart attacks and angina; damages thedevelopment of fetuses and young children; and aggravates chronicbronchitis, emphysema, and anemia. At high levels it causes collapse,coma, irreversible brain cell damage, and death.
  5. 5. Major Outdoor Air PollutantsNITROGEN DIOXIDE (NO2) Table 20-2 Page 438 be converted to nitricDescription: Reddish-brown irritating gas that gives photochemicalsmog its brownish color; in the atmosphere canacid (HNO3), a major component of acid deposition.Major human sources: Fossil fuel burning in motor vehicles (49%) andpower and industrial plants (49%).Health effects: Lung irritation and damage; aggravates asthma andchronic bronchitis; increases susceptibility to respiratory infectionssuch as the flu and common colds (especially in young children andolder adults).Environmental effects: Reduces visibility; acid deposition of HNO3 candamage trees, soils, and aquatic life in lakes.Property damage: HNO3 can corrode metals and eat away stone onbuildings, statues, and monuments; NO2 can damage fabrics.
  6. 6. Major Outdoor Air PollutantsSULFUR DIOXIDE (SO2) Table 20-2 Page 438Description: Colorless, irritating; forms mostly from the combustion of sulfurcontaining fossil fuels such as coal and oil (S + O2 SO2); in the atmospherecan be converted to sulfuric acid (H2SO4), a major component of acid deposition.Major human sources: Coal burning in power plants (88%) and industrial processes(10%).Health effects: Breathing problems for healthy people; restriction of airways in peoplewith asthma; chronic exposure can cause a permanent condition similar to bronchitis.According to the WHO, at least 625 million people are exposed to unsafe levels ofsulfur dioxide from fossil fuel burning.Environmental effects: Reduces visibility; acid deposition of H 2SO4 can damage trees,soils, and aquatic life in lakes.Property damage: SO2 and H2SO4 can corrode metals and eat away stone onbuildings, statues, and monuments; SO2 can damage paint, paper, and leather.
  7. 7. Major Outdoor Air PollutantsSUSPENDED PARTICULATE MATTER (SPM)Description: Variety of particles and droplets (aerosols) small and light enough toremain suspended in atmosphere for short periods (large particles) to long periods(small particles; Figure 20-6, p. 441); cause smoke, dust, and haze.Major human sources: Burning coal in power and industrial plants (40%), burning dieseland other fuels in vehicles (17%), agriculture (plowing, burning off fields), unpavedroads, construction.Health effects: Nose and throat irritation, lung damage, and bronchitis; aggravatesbronchitis and asthma; shortens life; toxic particulates (such as lead, cadmium, PCBs,and dioxins) can cause mutations, reproductive problems, cancer.Environmental effects: Reduces visibility; acid deposition of H2SO4 droplets candamage trees, soils, and aquatic life in lakes.Property damage: Corrodes metal; soils and discolors buildings, clothes, fabrics, andpaints.
  8. 8. Major Outdoor Air PollutantsOZONE (O3) Table 20-2 Page with an unpleasant odor that forms in theDescription: Highly reactive, irritating gas 438troposphere as a major component of photochemical smog (Figures 20-3 and 20-5).Major human sources: Chemical reaction with volatile organic compounds (VOCs,emitted mostly by cars and industries) and nitrogen oxides to form photochemicalsmog (Figure 20-5).Health effects: Breathing problems; coughing; eye, nose, and throat irritation;aggravates chronic diseases such as asthma, bronchitis, emphysema, and heartdisease; reduces resistance to colds and pneumonia; may speed up lung tissueaging.Environmental effects: Ozone can damage plants and trees; smog can reducevisibility.Property damage: Damages rubber, fabrics, and paints.
  9. 9. Major Outdoor Air Pollutants Table 20-2LEAD Page 438Description: Solid toxic metal and its compounds, emitted into theatmosphere as particulate matter.Major human sources: Paint old houses), smelters (metal refineries), leadmanufacture, storage batteries, leaded gasoline (being phased out indeveloped countries).Health effects: Accumulates in the body; brain and other nervous systemdamage and mental retardation (especially in children); digestive and otherhealth problems; some lead-containing chemicals cause cancer in testanimals.Environmental effects: Can harm wildlife.
  10. 10. Carbon Dioxide as a Pollutant1. In high enough concentrations any chemical in the air can become a pollutant.2. We have been increasing the CO2 in the troposphere by burning fossil fuels and clearing CO2 absorbing trees faster than they can grow back.3. The troposphere is warming and the evidence points to the additional CO2 added as a result of human activities.
  11. 11. Photochemical Smog Photochemical smog is a mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbons when they are exposed to sunlight. More than 100 primary and secondary pollutants can be formed.
  12. 12. Photochemical Smog ground level ozone (O3) + other photochemicalVOC + NOx + heat + sunlight oxidants + aldehydes + other secondary air pollutants
  13. 13. Photochemical SmogBrown Air Smog FPhotochemical ReactionPhotochemical oxidents
  14. 14. Smog Disasters Meuse Valley, Belgium, 1930 6000 people ill, 63 deaths in a few days Donora, Pennsylvania, 1948 6000 people ill, 20 deaths in three days Poza Rica, Mexico, 1950 22 dead & 320 hospitalized in 25 minutes London, England, 1952 4,000 dead in three days London 1956, 56, 62 2500 deaths attributed to coal smoke (smog) New York, New York, 1953, In 1962, increased to 269 1962-1963, 1966 due to photochemical smog
  15. 15. Industrial SmogParticulatesSulfur DioxideSulfuric AcidGray Air Smog
  16. 16. Emission Reduction
  17. 17. Regional Outdoor Air Pollution from Acid Deposition Wet Acid Deposition Dry Acid Deposition
  18. 18.  In the United States, coal burning power and industrial plants in the Ohio Valley emit the largest quantities of sulfur dioxide and other pollutants that can cause acid deposition. The typical precipitation in the Eastern United States has a pH of 4 – 4.8. More than 10 times the natural precipitation with a pH of 5.6.
  19. 19. Acid Deposition in the US
  20. 20. Acid Deposition - Plants, and SoilNutrient LeachingHeavy Metal Release Weakens Trees Fig. 20-11 p. 447
  21. 21. Emission Acid Deposition Acid SO2 NOXdeposition H2O2 O3 PANs Others Increased Susceptibility to drought, Direct damage Reduced extreme cold, to leaves and bark photosyn insects, thesis mosses, and and disease growth organisms Soil acidification Tree death Release of Root Reduced nutrient Leaching Acid toxic damage and water uptake of Soil metal nutrients icons Groundwater
  22. 22. Acid Deposition and Aquatic SystemsFish Declines Aluminum Toxicity Acid Shock
  23. 23. Solutions Acid Deposition Prevention CleanupReduce air pollution by Add lime to neutralizeimproving energy efficiency acidified lakesReduce coal use Add phosphate fertilizer to neutralize acidified lakesIncrease natural gas useIncrease use ofrenewable resourcesBurn low-sulfur coalRemove SO2 particulates,and Nox from smokestack gasesRemove Nox from motorvehicular exhaustTax emissions of SO2
  24. 24. Acid Deposition and HumansRespiratory DiseasesToxic Metal LeachingDamage to structures especially containing calcium carbonateDecreased VisibilityDecreased Productivity and profitabilityof fisheries, forests and farms
  25. 25. Solutions Stationery Source Air Pollution Prevention Dispersion or CleanupBurn low-sulfur Dispersecoal emissions above thermal inversionRemove sulfur layer with tallfrom coal smokestacksConvert coalto a liquid or Remove gaseous fuel pollutants after combustionShift to less Tax each unitpolluting fuels of pollution produced
  26. 26. Cleaned gas ElectrodesDust discharge Dirty gasElectrostatic Precipitator
  27. 27. Bags Cleaned gas Dirty gasBaghouse Filter Dust discharge
  28. 28. Cleaned gas Dirty gasCyclone Separator Dust discharge
  29. 29. Cleaned gas Dirty gas Clean water Wet gas Dirty waterWet Scrubber - Remove 98% of SO2 and particulate matter
  30. 30. Solutions Motor Vehicle Pollutions Prevention Cleanup Mass transit Bicycles and walking Emission control devices Less polluting engines Improve fuel efficiency Less polluting fuels Car exhaustGet older, polluting Inspectionscars off the road twice a year Give buyers tax write- Stricter offs for buying low- emission polluting, energy- standards efficient vehicles Restrict driving in polluted areas
  31. 31. Solutions Air Pollution Prevention CleanupImprove energy efficiency Reduce povertyto reduce fossil fuel useRely more on lower- Distribute cheap and efficientpolluting natural gas cookstoves to poor families in developing countriesRely more on renewableenergy (especially solarcells, wind, and solar- Reduce or ban indoor smokingproduced hydrogen)Transfer technologies for Develop simple and cheaplatest energy efficiency, test for indoor pollutantsrenewable energy, andpollution prevention to such as particulates, radon,developing countries. and formaldehyde