"Acid rain" is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. Acidic rain is caused mainly by dissolution of sulfur dioxide, nitric acid and hydrochloric acid. These pollutants originate from human activity such as the combustion of burnable waste and fossil fuels within thermal power plants and automobiles (Kita et al., 2004).
Rain that presents a concentration of H+ ions greater than 2.5 μeq−1 and pH values lower than 5.6 is considered acid (Evans, 1984). Galloway et al. (1982) proposed a pH of 5.0 as a limit of natural contribution. Rain with a sufficiently low pH to cause damage to plants had been registered near industrial sources.
The principal natural phenomena that contribute acid-producing gases to the atmosphere are emissions from volcanoes and those from biological processes that occur on the land, in wetlands, and in the oceans. The major biological source of sulphur containing compounds is dimethyl sulphide.
Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing off insect and aquatic lifeforms as well as causing damage to buildings and having possible impacts on human health. Both the lower pH and higher aluminium concentrations in surface water that occur as a result of acid rain can cause damage to fish and other aquatic animals. At pHs lower than 5 most fish eggs will not hatch and lower pHs can kill adult fish. As lakes become more acidic biodiversity is reduced. Acid rain has eliminated insect life and some fish species, including the brook trout in some Appalachian streams and creeks.
Like many environmental problems, acid deposition is caused by the cumulative actions of millions of individual people. Individuals can contribute directly by conserving energy, since energy production causes the largest portion of the acid deposition problem.
References:
71–80.
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