ACID RAIN
Acid rain is a form of pollution caused by the emission of sulphur dioxide and nitrogen oxides to the atmosphere.
More than 90% of the sulphur and 95% of the nitrogen emanations are of human activities origin. These primary air pollutants gets up from the use of coal in the generation of electricity, from metal smelting, and from fuel combustion in motor vehicles. Once released into the atmosphere, they can be transformed chemically into such secondary pollutants as nitric acid and sulfuric acid, which dissolve easily in water. The resultant acid water droplets can be carried long distances by prevailing winds, returning to ground as acid rain, snow, or fog.
Scientists have discovered that air contamination from the burning of fossil fuels is the major source of acid rain. The main chemicals in air pollution that generate acid rain are sulfur dioxide and nitrogen oxides. Acid rain regularly starts high in the clouds where sulfur dioxide and nitrogen oxides react with water, oxygen, and oxidants. This combination forms a mild solution of sulfuric acid and nitric acid. Sunlight amplifies the speed of these reactions. Rainwater, snow, fogs, and other kinds of precipitation containing those mild solutions of sulfuric and nitric acids drop to earth as acid rain.
About 40% of nitrogen oxides generate from means of transport (cars, trucks, buses, and trains), about 25% from thermoelectric generating stations, and 35% from other industrial, commercial, and home-made combustion practices.
Natural vegetation and harvests are damaged by acid rain.
It inhibits plant germination and reproduction.
It hastens soil erosion and taking away of nutrients.
It makes toxic elements, such as aluminum, more soluble. High aluminum concentrations in soil can stop the uptake and metabolizing of nutrients by plants.
It destroys the protecting waxy surface of leaves, lowering the disease resistance.
Long-lasting statistics indicates that although changes in stream pH have been small, great amounts of calcium and magnesium have been lost from the soil and sent abroad by water because of acid rain and diminutions of base cations in atmosphere. As a result, the recovery of soil and stream water chemistry in response to any reduction in acid rain will be delayed.
Despite the United States has diminished the sulfur contamination that conducts to acid rain, forests, lakes, and streams haven't bounced back as rapidly as projected. A team of investigators wrote an article confirming the basis: Acid has produced severe alterations in the soil. Thirty years of statistics on rain and rivers chemistry in New Hampshire woodlands provide evidence that the acid has stripped away the soil's basic mineral ions, which shield, or deactivate acids and are vital to plant growth. Given the rate, at which these ions are still being depleted, it could be decades before the acid-ravaged ecosystems become healthy again.
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