Acid Rain

Acid rain is a popular term for the atmospheric deposition of acidified rain, snow, sleet, hail and particulates, as well as acidified fog and cloud water. The increased acidity of these depositions, primarily from sulfuric and nitric acids, is generated as a by-product of the combustion]] of fuels,^[1] especially in fossil fuel power plants. The heating of homes, electricity production, and driving vehicles all rely primarily on fossil fuel energy. When fossil fuels are burned, acid-forming nitrogen oxides and sulfur oxides are released to the atmosphere. These chemical compounds are transformed in the atmosphere, often traveling hundreds of kilometers from their original source, and then fall out on land and water surfaces as acid rain. As a result, air pollutants from power plants in the states of New Jersey or Michigan can impact pristine forests or lakes in undeveloped parts of the states of New Hampshire or Maine.^[2]

Acid rain in North America was discovered in 1963 in rain at the Hubbard Brook Experimental Forest (HBEF)^[3] that was some 100 times more acidic than unpolluted rain. Technology for reducing fossil fuel combustion emissions, such as scrubbers upstream of the tall flue gas stacks in power plants and other industrial facilities, catalytic converters on automobiles, and use of low-sulfur coal, have been employed to reduce emissions of sulfur dioxide (SO₂) and nitrogen oxides (NOx).

It should be noted that, although the examples in this article describe the North American situation, the nature and effects of acid rain are similar all over the world.