Acid Deposition. Acid Deposition. Early History of Acid Deposition

Transcription

1 Acid Deposition 1 Acid Deposition Brief History Acids and Bases Chemical Processes and Sources Deposition Processes Acid Deposition Distribution Environmental Effects Health Effects Lakes and Forests Abatement 2 Early History of Acid Deposition 1200s: Coal combustion produces SOx and NOx 1750s: Industrial Revolution expands use of coal-fired steam engines Early 1800s: Alkali factories producing compounds for soap release hydrochloric acid (HCl), some sulfuric acid (H2SO4) and NOx 1863 Alkali Act in the UK 3

2 ph ph: index of acidity or alkalinity of a solution Negative logarithm of the H+ ion concentration Ex. H2SO4 2H + + SO4 2 Difference of 1.0 in ph equivalent to 10x difference in acidity ph = 7.0: neutral ph < 7.0: acidic ph > 7.0: basic 4 Typical ph Values Neutral Battery acid Vinegar Cola beverage Distilled water Natural rain Acid rain Tomato juice Baking soda Ammonia Lye 5 Sulfur Chemistry Natural SO2 SOx SO2 SO3,g Dissolve in liquid water SO3,g + H2O,v Combustion (oxidizes C, S, N) Fossil fuel H2SO4,aq (C + S) Sulfuric acid H2SO4,g/p 6

3 Natural Sulfur Sources Volcanoes SO2 Organic Decay H2S SO2 7 Anthropogenic Sulfur Fossil Fuels (C + S) 60% Coal 1 6% S Oil 1 2% S Gas 0.5% S 7% Electricity Industrial Other 33% 8 Other Acids NO2 + OH Nitric acid (HNO3) Organic acids Hydrogen chloride (HCl) Anthropogenic: Incineration of PVC plastic Natural: Volcanic emission Methyl chloride (CH3Cl) from ocean 9

4 Acid Deposition Processes Wet deposition Water coating Acidic gases Washout Rain, snow scavenging Rainout Acidic gases Acidic gases Runoff Cloud or fog droplets 10 Dry deposition Acidic gases 11 ph of Rain CO2,g H2CO3,aq Unpolluted rain ph ~ from carbonic acid SOx H2SO4,aq Acid rain ph < 5 from sulfuric acid 12

5 Regional Transport of Acids Adirondack Mts. SO2 receptor region Local NOx in So. Cal. SO2 source regions SW to NE flow 13 Precipitation ph Precipitation ph Hydrogen ion concentration as ph from measurements made at the Central Analytical Laboratory, Sites not pictured: AK01 AK03 PR20 VI National Atmospheric Deposition Program/National Trends Network Lab ph <

6 SOx Health Effects Effect of SO2 gas on respiratory system (ch. 7) Taste Odor Slight bronchial constriction Inflammation of mucous membranes SO2 + aerosol particles is worse than SO2 alone 16 High-altitude Lakes Freshwater Acidification Low-altitude Lakes Water source = direct precip. and runoff Water source filters through soil buffered Little or no soil buffering East: acidic granite soil West: alkaline limestone soil 17 High-altitude Lakes Freshwater Acidification Low-altitude Lakes Water source = direct precip. and runoff Water source filters through soil buffered Little or no soil buffering East: acidic granite soil West: alkaline limestone soil 18

7 Effects 19 Effects 20 Effects 21

8 Effects Aquatic plants and fish are stunted, reproduction impaired Metallic ions (e.g., aluminum, copper, lead) mobilize and leach from soils into nearby lakes 22 Forest Decline Definition: suppression of growth/ reproduction rates and death of trees Susceptible regions: Downwind of sulfur sources Eastern regions of continents, due to west-to-east prevailing winds High elevation Long-term contact with acidified clouds and fog Thinner soils, less buffering Eastern Europe, Northeastern U.S., Southeastern Canada 23 24

9 Recent Regulatory Action Clean Air Act Amendments of 1970 (US) 1977: National Atmospheric Deposition Program (NADP, US) 1979: Geneva Convention ln Long-range Transboundary Air Pollution 1985: Sulfur Protocol 1988: Nitrogen Oxide Protocol 1994: Second Sulfur Protocol Clean Air Act Amendments of 1990 (US) 25 Abatement Locate acid sources downwind of sensitive areas 26 Abatement Taller stacks Dispersion 27

10 Abatement Use lowsulfur fuels Oil, gas Low-sulfur coal Coal gassification Solvent-refined coal Scrubbers Reduce emissions Modified combustion 28 Abatement Clean-up Lake and soil buffers 29