Part 2 Acid rains

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Gases polluting the air, Siberia

he emissions, which cause acid rain, come chiefly from power stations and road traffic. Acid rain damages buildings as well as plant and animal life. It comes from sulphur containing in coal and oil. When fussil fuel is burnt, sulphur dioxide (SO₂) is formed. Then it is oxidized by reaction with oxygen to produce SO₃ gas, which combines with water in the air to produce droplets of sulphuric acid (H₂SO₄), a major component of acid rain. Nitrogen monoxide from exhaust fumes and industrial emissioms is also oxidized in the air and mixes with water to form nitric acid. Sulphic and nitric acids are carried long distances with air currents and fall as acid rain. Acid rain can travel thousands of miles, so pollution in one country can become acid rain fir another country.

The effects of acid rain vary enormously according to the type of soil on which it falls. Alkaline soils based on limestone can neutralize large amounts of acid, whereas peat or granite soils have very little ability to do so. The ability of certain chemicals within the rock (such as calcium carbonate) to reduce the acidity of the water is called natural buffering. But if the lake lies on an insoluble of acid rock such as granite, no natural buffering will occur and the acidity of the water will remain high. The problem first came to light in Scandinavia because its geology makes it especially sensitive to the effect of acid rain. In those places where the soil does not contain enough alkalis, which are needed to neutralize the acid, the fish in many lakes and rivers are poisoned by high acid concentrations. Scientists have tried to reduce the acidity of lakes artificially by adding chemicals to the water, but this intended remedy sometimes upsets the ecological balance even further

Part 3 Harmful effects of pesticides

Excess fertilizers can run off yards

The Centers for Disease Control and prevention released findings showing measurable amounts of residual organophosphate pesticides in a group of people who were studied. The National Academies of Sciences indicated that one out of four developmental and behavioral problems in children may be linked to genetic and environmental factors, including exposure to lead, mercury and organophosphate pesticides. When you put these two studies together, the conclusions could be cause for concern.

Runoffs from the farms can introduce harmful pesticides, wastes and other pollutants into rivers and streams. Organic farming reduces the level of these contaminants from runoffs.

With increasing demands for food supplies during the last years, we saw the introduction of the use of harsh chemicals and synthetic fertilizers as a way for farmers to boost crop yields. This subsequently has been followed by the more recent adoption of planting genetically modified crops. Even today, toxic and persistent pesticides are still used in agriculture. Organophosphate pesticides account for approximately half of the insecticides used in the United States. An estimated 60 million pounds of organophosphate pesticides are applied to about 60 million acres of U.S. agricultural crops annually, and an additional 17 million pounds are used per year for nonagricultural uses, such as household pest control products and in lawn and garden sprays.

Perhaps the harvest and most damaging of the chemicals introduced as a pesticide was DDT (dichlorodiphenyl – trichloroethane) which caused so much harm to animals and humans, its use was banned in the US in 1973. In fact DDT directly attributed to the near-demise of the bald eagle (as well as other species), which taken off of the endangered species list nearly 25 years after DDT was banned. DDT is still used in some parts of the world.