Geologic Studies of Mercury by the U.S. Geological Survey

Mercury emissions from coal-fired electric generating utilities are a major uncontrolled source of mercury in the environment. This mercury may be contributing to serious health problems in segments of our society. The USGS is compiling information on mercury in coal that may be useful in developing strategies for reducing mercury emissions from coal use. The USGS coal-quality database contains information on mercury concentrations in more than 7,000 coal samples. Detailed geochemical analysis has helped to determine that mercury in coal is commonly associated with pyrite, but other modes of occurrence may be locally important. Physical coal cleaning removes, on average, 37 percent of the mercury. Characterization of feed coal and its combustion byproducts is helping to further understand the behavior of mercury in utility boilers.