Mrs. Sealy APES

1. Ch. 17 Notes Air Pollution Mrs. Sealy APES

2. VII. Acid Deposition • 1. “dilution solution” to air-pollution: to reduce local air pollution and meet government standards without having to add expensive pollution control devices, most coal-burning plants, ore smelters, etc. use taller smokestacks to emit sulfur dioxide high into atmosphere • 2.    increases pollution downwind

3. VII. Acid Deposition • 3. chemicals reach ground:  • a. Wet: acid rain, snow, fog, cloud vapor • b. Dry:acidic particles • c. mixture causes acid deposition (acid rain)

4. VII. Acid Deposition • 4. pH: a numerical measure of the concentration of hydrogen ions in a solution (1 digit change equals 10X change in acidity) • a. levels less than 7 - acid (natural precipitation) • b. levels greater than 7 - Base • c. typical rain in east US is now about 10 times more acidic (pH 4.3)

5. Wind Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Wet acid deposition (droplets of H2SO4 and HNO3 dissolved in rain and snow) Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Sulfur dioxide (SO2) and NO Nitric oxide (NO) Acid fog Farm Ocean Lakes in shallow soil low in limestone become acidic Lakes in deep soil high in limestone are buffered Fig. 17.9, p. 428

6. 5. What areas are most affected by acid deposition? • occurs on a local rather than global basis b/c acidic components only remain in the air for a few days • areas downwind from coal and oil burning power plants, industrial plants and urban areas • ecosystems containing acidic soils without natural buffering of bases • growing problem in China (40% of its land), former Soviet Union, India, Nigeria, Brazil, Venezuela, Columbia

7. Potential problem areas because of sensitive soils Potential problem areas because of air pollution: emissions leading to acid deposition Current problem areas (including lakes and rivers) Fig. 17.11, p. 429

8. 6. What are the effects of acid deposition? •  medium-risk ecological problem, high-risk to human health • human respiratory diseases (bronchitis, asthma), damages statues, buildings, metals, plastics and paints • damages tree foliage, makes trees more susceptible to cold temps, disease, insects, drought, fungi • harmful to aquatic species

9. Effects of Weather Emissions Dry weather Low precipitation SO2 NOX Acid deposition Increased susceptibility to frost, pests, fungi, mosses, and disease H2O2 O3 Increased evapotranspiration PANs Others Direct damage to leaves and needles Dead leaves or needles Increased transpiration Water deficit Reduced photosynthesis and growth Bark damage Nutrient deficiency Soil acidification Damage to tree crown Tree death Kills certain essential soil microorganisms Sulfate Acids Nitrate Calcium Aluminum Magnesium Potassium Release of toxic metal ions Leaching of soil nutrients Disturbance of nutrient uptake Damage to fine roots Acids and soil nutrients Disturbance of water uptake Lake Groundwater Fig. 17.14, p. 432

10. D. What can be done to reduce acid deposition? • prevention • 1) reducing energy use & thus air-pollution by improving energy efficiency • 2) switching from coal to cleaner-burning natural gas • 3) removing sulfur from coal before it is burned • 4) burning low-sulfur coal • 5) removing SO2 particles, particulates, and nitrogen oxides from smokestack gases • 6) removing nitrogen oxides from combustion engines

11. D. What can be done to reduce acid deposition? • reducing coal use is economically & politically difficult • clean-up approaches are expensive and mask symptoms w/ out treating causes • acidified lakes can be neutralized by treating them or the surrounding soil with large amounts of limestone or lime. This is an expensive and temporary remedy