MadSci Network: Environment & Ecology
Query:

Re: WHY IS THERE SO MUCH MERCURY IN COAL?

Date: Thu Jan 12 14:49:13 2006
Posted By: Alex Barron, Graduate Student, Ecology(Biogeochemistry)
Area of science: Environment & Ecology
ID: 1137048157.En
Message:

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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