USGS research provides information on the amount and forms of mercury and other elements present in U.S. Coals (Tewalt et al., 2001).  Understanding the distribution of mercury in coal is especially important in light of recent U.S. EPA rulings, outlining plans to limit mercury emissions from U.S. coal-fired utilities.  Using selective chemical leaching (Figure 1), laser-ablation ICP-MS (Figure 2), and other approaches, USGS results show that pyrite is the primary host of mercury in bituminous coals, whereas the proportion of mercury present in organic parts of coal is generally greater in low-rank (lignite and sub-bituminous) coal. Many Eastern U.S. bituminous coals are “cleaned” prior to use in utility power stations, to reduce sulfur emissions.  This coal preparation reduces sulfur content, primarily by removing pyrite from coal.  In doing so, a portion of the mercury present may also be removed, as a co-benefit to sulfur reduction.  Currently about 35% of the mercury that goes into coal-fired utility power stations in the U.S. is captured by air pollution control devices, whose primary function is to trap particulates from coal combustion, or sulfur emitted from flue gasses.

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