Go Green! : Acid Rain

 The process of making acid rain

Certain pollutants such as NO, NO₂, and SO₂ form acids when mixed with water. NO and NO₂, primarily from vehicular emissions, combine with atmospheric oxygen and water to form Nitric acid, HNO₃(aq). SO₂ primarily from coal-powered electricity generation, combines with atmospheric oxygen and water to form Sulfuric acid,  H₂SO₄(aq). Both HNO₃(aq) and H₂SO₄(aq) cause rainwater to become acidic. The problem is greatest in the Northeastern United States where pollutants from Midwestern electrical power plants combine with rainwater to produce rain with acid levels that are up to 10 times normal.

Plants are also become a victim
of acid rain

When acid rain falls or flows into lakes and streams, it makes them even more acidic. Some species of aquatic animals such as trout, bass, snails, salamanders, and clams cannot tolerate the increased acidity and die. This then disturbs the ecosystem of the lake, resulting in imbalances that may lead to the death of other aquatic species. Acid rain also weakens trees by dissolving nutrients in the soil and washing them away and by damaging their leaves. Appalachian red spruce trees have been the hardest hit, with many forests showing significant acid rain damage.

A statue affected by acid rain

Acid rain also degrades building materials. Acids dissolve CaCO₃ (limestone), a main component of marble and concrete, and also iron, the main component of steel. Consequently, many statues, buildings, and bridges in the Northeastern United States have been harmed by acid rain. For example, some historical gravestones, made of limestone, are barely legible due to acid rain damage. Although acid rain has been a problem for many years, recent legislation has offered hope for change, in 1990, Congress passed several amendments to the Clean Air Act that included provisions requiring electrical utilities to lower SO₂ emissions.Since then, SO₂ emissions have decreased and rain in the Northeastern United States has become somewhat less acidic. With time, and with continued enforcement of the acid rain program, lakes, streams, and forests damaged by acid rain should recover.