MERCURY IN PEOPLE'S REPUBLIC OF CHINA COAL

The Peoples' Republic of China (China) produces and consumes the largest quantity of coal in the world; about 1.4 billion tons in 2002. Current projections, rough estimates at best, forecast coal consumption to be 3.3 billion tons by 2020. Although the nationwide percentage of electrical production from coal is falling due to increased power generation efficiency, China will burn more coal than any other country for the foreseeable future. China is also the largest producer of mercury emissions (Dastoor and Larocque, 2004, Atmos. Envirn. 38:147-161), with coal combustion as the greatest single source. Mercury emission into the atmosphere is an international problem as the upper atmosphere provides effective global transport of mercury (mostly Hg elemental). Although the estimates vary, China produces about three times more mercury per ton of coal burnt from a lack of modern pollution technology on most coal-fired electric utilities than the US. Knowledge of the mercury content, mode of occurrence, and regional distribution in Chinese coal is vital in order to assess the global atmospheric contribution from Chinese coal combustion. We have collected and analyzed 305 coal samples from mines with the highest production from 25 provinces, municipalities, or autonomous regions, which thus would reflect much of the coal currently supplied for power generation. The method of determination was routine cold-vapor atomic absorption spectroscopy using two methods of sample dissolution. The arithmetic mean, as-determined basis, of 305 samples is 0.15 ppm (1 sigma = 0.14), with a minimum of <0.02 ppm, and a maximum of 0.69 ppm. A small percentage (about 9 %) of the Hg data were below the detection limit of 0.02 ppm. Duplicate analysis and inter-laboratory comparisons suggest that significant analytical uncertainties can arise from imperfect sample splitting and that there are some problems associated with the analytical instrumentation. The mode of mercury occurrence is sufficiently heterogeneous as to generate significant analytical differences from preparation using a <60 mesh sample size.