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Acid Deposition

Acid Deposition. A form of Air Pollution Chapter 10. Acid Deposition. Acid Deposition is acid deposited on Earth as rain and snow, or as gases and particles that attach to the surfaces of plants, soils, and water. Acid Deposition  deposition with a pH < 5.6 All rain is naturally acidic.

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Acid Deposition

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  1. Acid Deposition A form of Air Pollution Chapter 10

  2. Acid Deposition • Acid Deposition is acid deposited on Earth as rain and snow, or as gases and particles that attach to the surfaces of plants, soils, and water. • Acid Deposition  deposition with a pH < 5.6 • All rain is naturally acidic. • Water and CO2 in the atmosphere react  Lowers the pH of precipitation from neutral to 5.6 • An acid is a substance that contributes hydrogen ions (H+) to a solution • Acid deposition is the result of human activity. Natural processes (i.e. volcanoes) may contribute.

  3. How does acid deposition form? • 1. Nitrogen oxides and sulfur dioxide are released into the atmosphere via combustion processes. • 2. These primary pollutants are transformed into the secondary pollutants – nitric acid and sulfuric acid (due to reactions between primary pollutants and atmospheric oxygen and water). • Transformations occur over a # of days • 3. Secondary Pollutants break down further into nitrate, sulfate, and hydrogen ions (H+) • Hydrogen ions generate the acidity in acid deposition. • Nitrates and sulfates are deposited on to vegetation, soil, and water.

  4. Acid Deposition in the U.S. • Has been reduced as a result of lower sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions • Improvements seen due to the amendments made in 1990 to the Clean Air Act

  5. Effects of Acid Deposition • Effects may be direct or indirect. • Direct Effects • Lower pH of lakes and streams (North America) • Caused decreased species diversity of aquatic organisms • Many species are able to survive and reproduce only within a narrow range of environmental conditions (Example on p.252). • Indirect Effects • Decreased pH can affect the food sources of aquatic organisms, creating indirect effects at several trophic levels.

  6. Effects of Acid Deposition • Human skin serves as a barrier to the irritant. Therefore, direct contact with acid deposition is not typically harmful to humans. • However, human health is affected by the precursors to acid deposition  SO2 and NOx • Acid deposition can harm human built structures. • Statues • Monuments • Buildings • Automobile finishes (painted surfaces)

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