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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 ....

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.... 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 ....