Pembaca Setia

11 February 2009

Acid Rain

Air pollution involves the release into the atmosphere of gases, finely divided solids, or finely dispersed liquid aerosols at rates that exceed the capacity of the atmosphere to dissipate them or to dispose of them through incorporation into solid or liquid layers of the biosphere. Air pollution results from a variety of causes, not all of which are within human control. Acid rain is one of the most dangerous and widespread forms of pollution. Technically, acid rain is rain that has larger amount of acid in it than what is normal. Acidity in rain is measured by collecting samples of rain and measuring its pH. For your information, “Acid rain can cause a lot of damage” (Mooney,1996,p.29). Many living and non-living systems become harmed and damaged as a result of acid rain.

According to Beckett (1996) in his book “Biology A Modern Introduction GCSE Edition”, life on earth is supported by a layer of air called the troposphere. This layer extends to a height of approximately ten kilometers. It is usual to explain pollution of the troposphere by stating the concentration of pollutants in parts per million (ppm), which means the number of cubic centimeters of pollutant in a cubic metre of air. The main cause of air pollution is the burning of fossil fuels such as coal and oil.

Sulfur dioxide and nitrogen oxide are produced especially when coal is burnt for fuel. When this fossil fuels are burned in factories, power stations, vehicles and aeroplane engine etc.,they produces smoke and fumes containing gases such as carbon dioxide and carbon monoxide.

At first , smoke and fumes are hot and rise into the air, especially if they come from high chimney stacks. Some of these substances remain in the air for long periods and may be carried hundreds of kilometres. While in the air they can enter clouds, dissolve in water vapour and form acid solutions which fall back to earth as acid rain. According to Smith (1992) in his book “Elements of Biology”,acid rain has been with us for years.

Many people said that “acid rain is causing serious damage to plants, soils and freshwater life around the world” (Beckett, 1996, p.11). Most farm crops are less affected by acid rain than are forests. The deep soils of many farm regions can absorb and neutralize large amounts of acid. Mountain farms are more at risk—the thin soils in these higher elevations cannot neutralize so much acid. Farmers can prevent acid rain damage by monitoring the condition of the soil and, when necessary, adding crushed limestone to the soil to neutralize acid. If excessive amounts of nutrients have been leached out of the soil, farmers can replace them by adding nutrient-rich fertilizer.

In soil, acid rain dissolves and washes away nutrients needed by plants. It can also dissolve toxic substances, such as aluminum and mercury, which are naturally present in some soils, freeing these toxins to pollute water or to poison plants that absorb them. Some soils are quite alkaline and can neutralize acid deposition indefinitely; others, especially thin mountain soils derived from granite or gneiss, buffer acid only briefly.

Acid rain also effects on aquatic ecosystems. Both the lower pH and higher aluminum concentrations in surface water that occur as a result of acid rain can cause damage to fish and other aquatic animals. At pHs lower than 5 most fish eggs will not hatch and lower pHs can kill adult fish. As lakes become more acidic biodiversity is reduced. Acid rain has eliminated insect life and some fish species, including the brook trout in some Appalachian streams and creeks. There has been some debate on the extent to which man-made causes of lake acidity have cause fish kills - for example Edward Krug.

Acid rain can best be curtailed by reducing the amount of sulfur dioxide and nitrogen oxides released by power plants, motorized vehicles, and factories. The simplest way to cut these emissions is to use less energy from fossil fuels. Individuals can help. Every time a consumer buys an energy-efficient appliance, adds insulation to a house, or takes a bus to work, he or she conserves energy and, as a result, fights acid rain.

As a conclusion, must work together to protect our environment. Everybody should be more responsible to our environment in order to minimize the pollution so that we can live on this earth peacefully.

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