Acid deposition, more commonly known as acid rain, occurs when emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) react in the atmosphere with water, oxygen, and oxidants to form acidic compounds. This mixture forms a mild solution of sulfuric and nitric acid which then falls to the earth in either wet (rain, snow, sleet or fog) or dry (gas and particles) form. Approximately one-half of the atmosphere's acidity falls back to earth through dry deposition in the form of particles and gases, and are then spread hundreds of miles by winds where they settle on surfaces of buildings, cars, homes, and trees.

As lakes and streams become more acidic, the amount of fish, aquatic plants and animals that live in these waters decrease. Although some plants and animals can survive acidic waters, others are acid-sensitive and will die as the pH declines. Plants and animals living within an ecosystem are highly interdependent. If acid rain causes the loss of acid-sensitive plants and animals, organisms at all trophic levels within the food chain may be affected which then causes a disruption to the entire ecosystem. In New York's Adirondack region, the diversity of life in these acidic waters has been greatly reduced. The fish population has disappeared and loons and otters have moved to other lakes where they can find food (Simonin, 1998, p4). In Canada, over 14,000 lakes have been acidified to the point where they have lost significant amounts of fish.

When acid rain falls, the dry deposited gases and particles are sometimes washed from buildings, trees and other surfaces making the runoff water combine with the acid rain more acidic than the falling acid rain alone. This new combination is referred to as acid deposition. Strong prevailing winds and public sewer systems into lakes and streams then transport the runoff water. Although some natural sources such as volcanic eruptions, fire and lightening contribute to the emissions of sulfur dioxide and nitrogen oxides in the atmosphere, more than 90% is the result of human activities such as coal burning, smelting of metals such as zinc, nickel and copper, and the burning of oil, coal and gas in power plants and automobiles.

Not all fish, shellfish or their foot insects can tolerate the same amount of acid.. For example, frogs seem to be the toughest survivor by being able to tolerate a pH up to 4.0, whereas clams and snails are the weakest only being able to tolerate a pH of 6.0 before it will become extinct. There are two patterns that contribute to the disappearance of fish from acidic bodies of water. The first pattern is known as "acid shock", which is a sudden drop in pH. These pH shocks usually occur in early spring when melting snow releases acidic elements accumulated during the winter into a lake or stream causing a rapid decrease in pH level, which in turn causes fish to die. A second pattern is the gradual decrease in pH level over a prolonged period of time interfering with fish reproduction; therefore, causing decrease in fish population, and a change in size and age of the population. Other animals are affected by acidic water as well. For example, low pH will often stunt the growth of frogs, toads and salamanders.

Acid rain is more common in the Eastern U

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Approximate Pages = 7 (250 words per page double spaced)