- 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
- 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
- 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.