the form of rain? No longer is it just water that falls from above; acid pollutants can be deposited from the atmosphere to the Earth's surface in wet and dry forms. The common term for this is called acid deposition. An acid can be defined as any substance that when dissolved in water dissolves to yield corrosive hydrogen ions (Carousel 34).
             Precipitation normally has a pH level between 5.0 to 5.6 because of natural atmospheric reactions involving carbon dioxide. Precipitation is considered to be acidic when its pH falls below 5.6, which is 25 times more acidic than pure water. Some sites in eastern North America have precipitation with pHs as low as 2.3 or about 1000 times more acidic than natural water (Carousel 34-35).
             Acid deposition influences the environment in several different ways. In aquatic systems, acid deposition can effect these ecosystems by lowering pH levels. One of the most obvious effects of aquatic acidification is the decline in fish numbers. Originally it was believed that the fish died because of the increasing acidity of the water, but it was later discovered that high acidified lakes also contained high concentrations of toxic heavy metals like mercury, aluminum, and cadmium. The source of these heavy metals was the soil and bedrock surrounding the water body. These to
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