Acid Rain

Acid rain is the term generally used for pollutants created by burning fossil fuels that then change chemically as they are transported through the atmosphere and fall back to earth as acidic rain, snow, fog, or dust. The pollutants are chiefly oxides of sulfur and nitrogen, and they come primarily from coal and oil-burning power plants and industries and from automotive exhausts. When sulfur dioxide is absorbed into water vapor in the atmosphere, it becomes sulfuric acid. Sulfur dioxide contributes about two-thirds of the acids in the rain; about one-third come from nitrogen oxides, transformed into nitric acid in the atmosphere.

When the acids are washed out of the air by rain, snow, or fog, they change the pH factor of the soil and water, setting off a chain of chemical and biological reactions. The pH factor measures the acidity/alkalinity of a substance on a scale of 0 to 14. The average pH of normal rainfall is 5.6, but acid rainfalls with a pH of 2.4 - approximately the acidity of vinegar or lemon juice - have been recorded. It is important to note that the pH scale is logarithmic, so that 4.0 is ten times more acidic than 5.0 and one hundred times more acidic than 6.0. Acid rain also coats the ground with particles of aluminum and toxic heavy metals such as cadmium and lead.

Once the pollutants are airborne, winds can carry them hundreds of miles depositing them far from their source. Approximately half of the acid rain that falls on eastern Canada originates in the US, chiefly from the coal-burning power plants in the Midwest. This issue has become a sore point in US-Canadian relations, because the effects of acid precipitation on water bodies, forests, and wildlife are deadly. The problem is that the acidity of a lake or stream need not increases much before it begins to disrupt the food chain.

Canada' Department of the Environment has reported that acid rain has already damaged some 14,000 lakes in that country, rendering them almost fishless; another 150,000 are in peril. Acid rains have also been linked to the disappearance or decline of fish populations in Scandinavia. Some 20% of Sweden's lakes are said to have been damaged by pollution, and much of Norway's fish population has been exterminated.

Acid rain harms soils and vegetation,. It leaches toxic constituents like aluminum salts from the soil and kills micoorganisms in the soil that break down organic matter and recycle nutrients through the ecosystem. Extensive forest damage has occurred in parts of North America, northern and western Europe, The USSR, and China. One can also see the corrosive effects of atmosphere acid on marble and limestone sculptures and buildings and on metals such as iron and bronze.

Much of the responsibility for solving the acid rain problem lies with industry and government, but individuals can help by reducing their demand for energy. Various ways of conserving energy are discussed in a subsequent section, which deals with the greenhouse effect and acid rain is to reduce the emission of pollutants into the atmosphere. We can do that by using less energy and by using it as efficiently as possible,