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From the Fall 2012 Conservationist for Kids

image of mercury cycle

The Mercury Cycle

By Gina Jack

Mercury occurs naturally in the environment from volcanic activity, forest fires, erosion of rocks and decomposition of soils. It also enters the environment from human activity.

Researchers study the amount of mercury in our environment. They test our air, water, and food (fish) to determine how much mercury is present and whether the level is harmful. They also investigate which kinds of wildlife are most affected by mercury and what those effects are. They study the effects of mercury on fish, loons, songbirds, river otters, bald eagles, bats, insects and spiders.

Most of the mercury in our air from human sources comes from electric power plants that burn coal to generate electricity. Other human sources include emissions from factory smokestacks and burning waste contaminated with mercury. Mercury is also used in mining to purify gold and silver.

Once it's in the air, mercury can travel wherever the wind blows. When rain or snow falls, it carries mercury from the atmosphere onto the land and into the water of rivers, wetlands, lakes and oceans. Mercury on the land is carried into water bodies by runoff and groundwater.

When mercury falls into a waterbody, bacteria in the sediment can convert it to methylmercury, a form of the metal that dissolves in water. Methylmercury can be taken up by aquatic plants and absorbed by insects, worms and other small creatures that live in the sediments. Fish can also absorb methylmercury directly from the water.

Methylmercury accumulates in the body; it doesn't pass through and go away. When plants and animals are eaten, methylmercury is carried through the food chain. Animals at the end of the food chain get all the methylmercury consumed by all of the animals before them.