Impact of Technologies on the Atmosphere

1
Impact of Technologies on the Atmosphere

• Acid Rain

2
Acid Rain

• Natural rainwater has a pH 5.6 due to carbon
  dioxide reacting with water
• CO2 H2O ? H2CO3 ? H HCO3 -
• Acid rain is rain having pH
• In US, rain averages pH of 4.1 to 6.1

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pH of Rainfall
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
230
4
http//www.oceansonline.com/water_props.htm
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Sources of Acid Rain

• Natural source - volcanoes
• Anthropogenic (human activities) - burning of
  fuels containing S
• S O2 ? SO2
• 2 SO2 O2 ? 2 SO3
• SO3 H2O ? H2 SO4

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Sources of Acid Rain

• Anthropogenic - combustion at high temperature in
  the presence of air
• N2 O2 ? 2 NO (colorless gas)
• 2 NO O2 ? 2 NO2 (dark brown gas)
• 4 NO2 O2 2 H2O ? 4HNO3

7
Annual emissions of gases causing acid rain
Schwartz et al, Chemistry in Context, ACS, DC,
1994, 163
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Production of Acid Rain
Hill/Petrucci, General Chemistry, Prentice Hall,
NJ, 1996, 546
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Acid Rain
http//www.geog.ouc.bc.ca/physgeog/contents/table.
html
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Acid dissolves metals and stone, particularly
marble CaCO3 H ?
Ca2 HCO3 -
Effects of acid rain on a to
mbstone that was carved in 1817 in England
Raven et al, Environment, Saunders, NY, 1995, 450
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Dissolving of Soil Components by Acid Rain
http//www.geog.ouc.bc.ca/physgeog/contents/table.
html
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Effects of Acid Rain on Soil

• Minimal in regions having limestone
• CaCO3 H ? Ca2 HCO3 -
• Regions having granite rock, leaching of clay
  (Al2Si2O5(OH)4 ) occurs
• Al2Si2O5(OH)4 6 H ? 2 Al3 2 SiO2 5 H2O
• Al3 can kill trees and fish

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Granite
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
232
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Effect of Acid Rain on Trees
Raven et al, Environment, Saunders, NY, 1995, 449
15
Blue Ridge Mountains, NC
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
232
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Fish kills can arise from a variety of causes,
including acid rain. These dead fish are on the
shore of Lake Michigan.
Schwartz et al, Chemistry in Context, ACS, DC,
1994, 171
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Other Effects of Acid Rain

• Oxidation of sulfur dioxide can also produce
  aerosols of ammonium sulfate which reduce
  visibility
• Visibility in East US is 1-25 miles while in the
  West it is 50-70 miles

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Sulfate Aerosol Haze
Discover, Geology Issue Number 1, Disney
Magazines, 1993, 50
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Sulfate Aerosol Haze
Stanitski et al, Chemistry in Context, 3rd, ACS,
DC, 2000, 248
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Society's Response

• Clean Air Act of 1990 requires utilities to cut
  SO2 emissions to half the 1980 level (about 19
  million tons) by 2010
• Power plants have annual SO2 emission allowances
  which can be traded

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Industries' Source Reduction Responses

• Using old technologies described earlier (coal
  flotation or scrubbing)
• New technology S-eating bacteria to clean coal
• Burning higher grade coal which is expensive

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Joesten et al, Chemistry Impact on Society,
Saunders, NY, 1988, 172
23
Industries End-of-Pipe Responses

• End-of-pipe responses rely on the Arrhenius
  acid/base neutralization reaction
• For soils, limestone is added
• CaCO3 H ? Ca2 HCO3 -
• For lakes, lime is added
• CaO H ? Ca2 H2O

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Application of Agricultural Limestone to Soil
Chang, Chemistry, 5th, McGraw Hill, NY, 1994, 727
25
Liming an Acid Lake in Sweden
Stanitski et al, Chemistry in Context, 3rd, ACS,
DC, 2000, 251