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Acid Rain

Acid Rain

Acid rain is caused by extra amounts of sulphur dioxide and nitrogen oxides. Natural sources of sulphur oxides and nitrogen oxides do exist, but are balanced by nature. Normal rain reacts with alkaline chemicals from the region's bedrock that are in the air, soils, lakes, and streams. This neutralizes the rain. However, if rain is more highly acidic, then the natural neutralizing chemicals can eventually become depleted. This is what is happening with more than 90% of the sulphur and 95% of the nitrogen emissions coming from humans. Approximately 40% of the nitrogen oxides come from transportation, about 25% from thermoelectric generating stations, and the balance from other industrial, commercial, and residential combustion processes. These pollutants come from the use of coal in the production of electricity, from smelting, and from the internal combustion engines in most cars. Once released into the atmosphere, they are converted into such pollutants as nitric acid and sulfuric acid, both dissolving easily in water. This results in acidic water droplets that can be carried by prevailing winds, returning to Earth as acid rain, snow, or fog.

This effects the lakes by changing the pH balance. As the water pH approaches 6, crustaceans, insects, and plankton begin to disappear. When the pH is slightly above 5, major changes start to happen, less desirable species of mosses and plankton may begin to flourish, whereas others will lessen in numbers and die off. Below pH of 5, the water is to acidic for many fish, the bottom is covered with undecayed material, and the shores may be dominated by mosses.

Animals also are affected. Some ducks, for example, depend on fish and other organisms for nourishment and nutrients. As these food sources are reduced or eliminated, the population in that area declines and the reproductive success of the birds is affected.

Plants are effected too. The acids can alter the protective waxy surface of...