Acid Rain Public Policy Teaching Resources Further Reading Acid rain, or acid deposition, is not a new phenomenon. An acid is any chemical that releases hydrogen ions when dissolved in water. The higher the concentration of hydrogen ions, the more acidic a solution is. Rain that is mixed with sulfur and nitrogen in the air becomes more acidic than normal.
Sulfur dioxides comes from natural and human sources.
Natural sources include volcanoes, forest fires, and biological decay. Worldwide emissions from human sources are estimated at about 79 million tons of sulfur dioxide and 22 tons of nitrogen oxides. The primary sources of sulfur dioxide and nitrogen oxide from human activities are power plants, factories, and automobiles. Acid deposition occurs when acidic particles fall as dust or mix with rain droplets to form acid rain. Concern about the effects of acid deposition on forests and lakes began about thirty years ago when scientists in Sweden, the U.S., and other countries noted declines in fish populations in certain lakes.