The Effects of Mercury in the Environment
The Effects of Mercury in the Environment
Introduction
Mercury is a silvery, liquid metal at room temperature. It is sometimes referred to as one of the "heavy metals." Like water, mercury can evaporate and become airborne. Because it is an element, mercury does not break down into less toxic substances. Once mercury escapes to the environment, it circulates in and out of the atmosphere until it ends up in the bottoms of lakes and oceans. Depending on its chemical form, mercury may travel long distances before it falls to earth with precipitation or dust.
Mercury contamination on aquatic environment
Concentrations of mercury in fish and wildlife are high enough to be a risk to wildlife. Once mercury escapes to the environment, it circulates in and out of the atmosphere until it ends up in the bottoms of lakes and oceans. Depending on its chemical form mercury may travel long distances before it falls to earth with precipitation or dust. Mercury gets into lakes from the atmosphere, where it falls with rain or snow into the watersheds that feed the lakes. Approximately one gram of mercury enters a 20-acre lake each year.
When mercury is deposited in lakes or waterways, bacteria convert it to methyl mercury. Methyl mercury accumulates in algae and is eaten by smaller fish, which in turn are eaten by larger fish.
Unfortunately, the mercury in fish also concentrates in the tissue of any human or wildlife eating the fish. If contaminated fish are eaten on a regular basis, mercury concentrations can become high enough to become a serious health threat to humans. Several Great Lakes states issue advisories each year, cautioning people to limit the amount of fish they eat from area lakes.
As long as the fish continue to be exposed to mercury, mercury continually builds up in fish's bodies. Fish that eat other fish become even more highly contaminated. Thus, the fish most desirable for many additional bigger fishes become the most affected, and larger fish tend to be the most contaminated.
Bacteria and chemical reactions in lakes and wetlands change the mercury into a much more toxic form known as methylmercury. Fish become contaminated with methylmercury by eating food (plankton and smaller fish), which has absorbed methylmercury.
This type of mercury...