1. Baxter State Park, Maine: the Knife Edge Trail at the north end of the Appalachian Trail

2. Acid Precipitation

3. Identifying the Problem First warnings –Adirondacks 1970s? –Brenner pass Early 1980s –Eastern Canada Early 1980s –Smoky Mountains Mid-1980s –Worldwide 1990s

4. Identifying the Cause Disease Weather Pests –Insects –Fungi Pollutants –Local vs distant

5. Chemistry of Acid Precipitation S + O 2 --> SO 2 SO 3 + H 2 O --> H 2 SO 4 N + O 2 --> NO 2 NO 2 + H 2 O --> HNO 3

6. Acid Precipitation http://www.physicalgeography.net/

7. Origins of the Problem 1950s effort to clean up local air –Lethal smogs Donora London Solution: higher chimneys –The solution to pollution is dilution Consequences: –Diffusion of pollutants high into the troposphere –Long-range transport of gases, vapors

8. Effects on Natural Environments Terrestrial –Soils Buffering capacity of soil Available nutrients –Leaching Type of plant –Perennial vs annual –Foliage cycle –Plant parts are affected differently Leaves Roots Aquatic effects –pH –Metals 1990s Nay Sayers UIUC crop scientist –Illinois soil pH has not changed –Crops are not suffering –No problem! Reagan administration Coal industry

9. Effects on Human Artifacts Metal Fabrics Stone –Limestone 19081968 http://www.whatischemistry.unina.it http://gardenofeaden.blogspot.com

10. Politics of Acid Precipitation Source –Example: NY Adirondack mountains 50% of air pollution is local –Cars –Manufacturing 50% is from distant sources –Midwestern power plants Arguments against Mitigation –too expensive –Industry: $1,000-$1,500 per Ton sulfur $2.4-5 billionannual cost –EPA: $6 billion/year? Legislation: –Clean Air Act, 1990 signed by GHW Bush reduce annual S deposition by 10,000,000 T from 1980 levels –2 phases 1995 mostly coal-fired power plants 2000 - stricter limits on all plants Use of “cap and trade” to achieve decreases without damaging productivity –Monitoring of acid deposition throughout Costs: –$100-200 / Ton sulfur dioxide –Total annual costs: 836,000,000 PS: there were also cuts in particulates –decreased risks for asthmatics, etc –decreased atmospheric haze

11. The actual cost of residential electricity in the US, 1991-2010, depended more on the economy than on acid rain mitigation

12. Deposition of sulfur as sulfate: kg/ha/yr

13. Hydrogen ion deposition in the US: 1995 (left) and 2010 (below) H + ion levels in kg/Ha

14. Summary Acid precipitation is a special case of air pollution Air pollution affects living and non-living systems adversely Controlling air pollution costs money –but not as much as opponents predict Not controlling air pollution is more expensive in the long run –and we haven’t even talked about incommensurables and intangibles One more example of the importance of societal decisions vs laboratory data

16. Absolutely doable, and very safe – IFF you stay on the trail, which is unmistakably marked.