8.5 Acid deposition

Acid deposition

  • Acid deposition: the process by which acid-forming pollutants are deposited on the earth’s surface.
  • Increased industrialization have led to rapidly increasing emission of nitrogen and sulfur dioxides which cause acid rain, most prevalent form of acid deposition

Acid rain

  • Pure water has pH of 7.0. Rainwater is acidic due to presence of dissolved carbon dioxide which forms weak carbonic acid. Typical pH is 5.6
  • Acid deposition is formed when nitrogen or sulfur oxides dissolve in water to form HNO3, HNO2, H2SO4 and H2SO3
    • NO2 + H2O
  • The sources of nitrogen and sulfur are:
    • Volcanic eruptions
    • Decomposition of vegetation
    • Combustion of fossil fuels
  • Go over nitrogen and sulfur cycles which form the acids

Pre- and post-combustion technologies

Pre-combustion methods: refer to techniques used on fuels before their combustion

Post-combustion methods: focus on several complementary technologies to remove sulfur dioxide, nitrogen oxides and other gases from combustion gases before they are released into the atmosphere.

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