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Chapter 6 (CIC). Read in CTCS Problems in CTCS:. Acid Rain. Natural rain is at pH = 5.6 CO 2 + H 2 O H + + HCO 3 - Acid is clearly in Eastern 1 / 3 of US (Ohio River Valley) Must be due to more than just CO 2 SO 2 , SO 3 , NO, NO 2 (SO x and NO x )
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Chapter 6 (CIC) • Read in CTCS • Problems in CTCS:
Acid Rain • Natural rain is at pH = 5.6 • CO2 + H2O H+ + HCO3- • Acid is clearly in Eastern 1/3 of US (Ohio River Valley) • Must be due to more than just CO2 • SO2, SO3, NO, NO2 (SOx and NOx) • SOx is primarily from coal fired power plants, steel mills and heavy industry • NOx is found in large urban areas with heavy population densities – auto traffic
Where’s the H+? • Just like with CO2, SOx and NOx are acid anhydrides • But where did the S come from in coal? • C135H96O9NS • Ca, Si, Na, Al, Ni, Cu, Zn, As, Pb, Hg can also be found in ash • amino acid cysteine
Statistics • US is about 50:50 in NOx and SOx • 86% of SO2 is from coal fired electrical utilities • 46% of NOx is from coal fired electrical utilities • Twice as much SOx asNOx worldwide • Difficulties in getting global air treaty (Kyoto)
What does Acid Rain Do? • Marble statues (Parthenon-Greece; Taj Mahal-India; Mayan ruins-Mexico; US Capitol; Stalagtites in Lincoln Memorial) • Rusting of Steel (bridges, buildings, railroads) • Coat metal with Zn or Cr • Visibility • Illness in elderly, asthma, bronchitis, and emphysema • EPA estimates saving $12-40 billion in health care because of 90’ Clean Air Act • Solubility of toxic metals (Pb, Cd, Hg)
Visibility Great Smoky Mountain National Park… …on a hazy day
Damage to Lakes and Streams • Healthy lakes have a pH of no less than 6.5 • A pH below 5.0 has few species surviving • A pH below 4.0 is essentially dead • CaCO3 buffers a lake • H+ can release Al3+ - mess up gills • Add lime, Ca(OH)2, to lakes
Trees and Forests • 1993 – 25% of all European trees had lost 25% or more of their needles • Acid tends to make the trees more susceptible to: • Insects • Disease • Weather • drought
Costs • 1990 Clean Air Act • Phase I – Reduce power plant SO2 emissions by 10 million tons below 1980 levels for 110 of 2000 dirtiest plants (from 10lbs/106 BTU to 2.5 lbs/106 BTU) • 2 million ton reduction of NOx • Starts in 1995 • Phase II – Reduce SO2 to 1.2 lbs/106 BTU • Includes other power plants • Starts in 2000
Options 1. Move to clean coal (little S) • It’s nearly all gone in the east; transport from the west 2. Clean up coal to remove S • $750/ton SO2 3. Neutralize SO2 by scrubbing • $500/ton SO2 mostly for disposal of CaSO4 • SO2 + O2 + CaCO3 CaSO4 + CO2 • 59% have chosen option #1 (get less energy/g coal) • 28% have chosen option #3
Estimated Costs • Congressional Office of Technology Assessment: $3-4 billion per year • Electric Power Companies: $4-23 billion/yr Actual Costs • $836 million in 1995 - $3/person in the US • Utility bills have remained nearly constant over the last decade