|MadSci Network: Environment & Ecology|
Kim – Mercury in the environment is a big problem, but the problem is that there’s some mercury in coal _and_ that we burn a lot of coal. Coal forms from buried organic matter. Organic-rich wetland soils contain sulfur (which comes from organic material and is also a problem when you burn coal) as well as metals like iron and manganese. Various forms of mercury that move naturally through the environment at very low concentrations bond to the sulfur and iron and get stuck in the peat soils. Later, when the peat forms coal, you still have the mercury there. As you might guess, the details of this process can influence the amount of mercury trapped. As a result some coal (from northern Appalachia) has high amounts of mercury while coal from other areas (the Wind River mine in Wyoming) has half as much. The mercury is generally on the order of 10 to 20 parts per million. By contrast, fuel oil is about 10000 times lower in mercury (one part per billion) and natural gas is basically mercury free. The problem comes when we dig up that coal and burn it. Unlike most metals, mercury can be converted to a gas so it escapes the combustion process and ends up in the atmosphere. From there it can be deposited in natural systems where it can be converted into methylmercury – which is when it is especially toxic. We can all help with this problem by using less energy, encouraging renewable energy and encouraging technology to help keep mercury out of the environment. Sources USGS Fact Sheet: Mercury in U.S. Coal
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