Occurrence, emissions and deposition of mercury during coal combustion in the province Guizhou, China

Abstract

Forty-eight coal samples from the major coal mines in Guizhou were collected by means of subterranean channel sampling. The average mercury content in coal from this Chinese province is 0.53 mg kg-1, which is substantially higher than coal produced in any other province of China. A strong link is proposed to exist between atmospheric mercury emissions and the combustion of coal. During the last two decades, the amount of mercury emitted from coal combustion in Guizhou has increased invariably to 8.3 tons in 1998. Being concentrated to the pyrite fraction in the coal, the implementation of physical coal cleaning is likely to be an effective way to reduce the mercury content. Total and fractionated mercury in air and precipitation was measured in the provincial capital. During a measurement campaign in October 1999, the reactive gaseous mercury (RGM) concentration averaged at 450 pg m-3, which is much higher than that in pristine area (less than 20 pg m-3). The average total mercury in rainwater of 1996 was estimated to be 33 ng L-1, and the total annual wet deposition of mercury in the area was 39 g km-2 in 1996.