Air pollution: Tropospheric ozone, and wet deposition of sulfate and inorganic nitrogenThis article is part of a larger document. View the larger document here.
The influence of air pollutants on ecosystems in the United States is an important environmental issue. The term “air pollution” encompasses a wide range of topics, but acid deposition and ozone are primary concerns in the context of forest health. Acid deposition partially results from emissions of sulfur dioxide, nitrogen oxides, and ammonia that are deposited in wet form as sulfate (SO4 2-), nitrate (NO3 -), and ammonium (NH4 +) by rain, snow, and sleet. Inputs of sulfur and nitrogen can also come from dry deposition or from clouds and fog (Driscoll and others 2001). Tropospheric ozone develops during photochemical reactions between nitrogen oxides and volatile organic compounds. Acid deposition can affect soil and water acidity (Driscoll and others 2001), and ozone can cause foliar injury (Chappelka and Samuelson 1998, Cleveland and Graedel 1979, Lefohn and Pinkerton 1988). However, doseresponse relationships are complicated and depend heavily on species composition, edaphic factors, and climatic conditions.