Acid Deposition (acid Rain)

Acid deposition comes in the form of either dry, airborne acidic particles or precipitation. Dry acid deposition can come in the form of either sulfur dioxide gas or sulfur and nitrogen salts. Acid precipitation occurs in forms such as rain, snow, mist, and fog. With industry steadily increasing throughout the world, the problem of acid deposition grows. Acid deposition has many negative effects - on the environment, on the economy, and on human health. Action must be taken immediately to reduce acid deposition.

There are 2 main causes of acid deposition; natural causes and man-made causes. Natural causes include volcano emissions, lightning, and microbial processes, while man-made causes refer to industrial emissions and other man-made polluters, including automobiles. The acid in acid rain comes from two kinds of air pollutants-- sulphur dioxide and nitrogen oxides. When sulphur dioxide and nitrogen oxides are released into the atmosphere by smokestacks, fuel combustion, or natural causes, they combine with gaseous water in clouds and change to acids--sulphuric acid and nitric acid. Although some acid deposition is caused naturally, which is normal and is not a problem, the majority is created by fuel combustion, etc. All of this extra acid deposition that is not natural cannot be dealt with by the environment; therefore, acid deposition causes many problems.

The effects of acid rain in have been recorded in parts of the United States, the late Federal Republic of Germany, Czechoslovakia, the Netherlands, Switzerland, Australia, Yugoslavia and elsewhere. It is also becoming a significant problem in Japan and China and in southeast Asia. Rain with a pH of 4.5 and below has been reported in Chinese cities ("Japan and China"). Sulphur dioxide emissions were reported in 1979 to have nearly tripled in India since the early 1960s, making them only slightly less than the then-current emissions from the Federal Republic of Germany.

Acid rain affects lakes, streams, rivers, bays, ponds and other bodies of water by increasing their acidity until fish and other aquatic creatures can no longer live. Aquatic plants grow best between pH 7.0 and 9.2 (Bourodemos). As acidity increases (pH numbers become lower), submerged aquatic plants decrease and deprive waterfowl of their basic food source. At pH 6, freshwater shrimp cannot survive. At pH 5.5, bottom-dwelling bacterial decomposers begin to die and leave undecomposed leaf litter and other organic debris to collect on the bottom. This deprives plankton--tiny creatures that form the base of the aquatic food chain--of food, so that they too disappear. Below a pH of about 4.5, all fish die.

As undecomposed organic leaf-litter increases, owing to the loss of bottom-dwelling bacteria, toxic metals such as aluminum, mercury and lead within the litter are released. Other metal flows into the water from the soils in the surrounding watershed.

These toxic metals are bad for human health; high lead levels may harm people who drink such water and people who ingest mercury in tainted fish suffer serious health problems. Most of the frogs and insects also die when the water reaches pH 4.5.

Acid rain harms more than aquatic life. It also harms vegetation. The forests of the Federal Republic of Germany and elsewhere in Western Europe, for example, are believed to be dying because of acid rain. Scientists believe