Mercury Emissions from China
Figure 1. Coal use for domestic heating and cooking is pervasive in most of China. Two push-cart coal sellers selling lump coal used particularly for cooking; in Guiyang the capital of Guizhou Province, P.R. China.
The Peoples' Republic of China produces and consumes the largest quantity of coal in the world; about 1.7 billion tons produced in 2003 (Figure 1). 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 also is estimated to be the largest producer of mercury emissions (Dastoor and Larocque, 2004). A recent comprehensive study of anthropogenic mercury emissions in China (Streets et al., 2005) yielded a figure of 536 t of mercury for the year 1999 with coal combustion (all types) accounting for 38% of the total. Atmospheric mercury emission is an international problem as the troposphere provides effective global transport of mercury. Although the estimates vary, China produces about three times more mercury per ton of coal burnt than the USA because of the lack of modern pollution technology and limited use of cleaned coal. 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.
Under the aegis of the USGS WoCQI Program, we have collected and analyzed 305 coal samples from mines with the highest production from 25 provinces, municipalities, or autonomous regions, which thus reflects much of the coal currently supplied for power generation and industrial use. The method of determination was routine cold-vapor atomic absorption spectroscopy using two methods of sample dissolution. The arithmetic mean, on an as-determined, whole-coal 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. All data averaged to a dry basis is 0.16 ppm. A small percentage (~ 9 %) of the mercury data were below the method detection limit of 0.02 ppm. Duplicate analyses and inter-laboratory comparisons suggest that analytical uncertainties can arise from imperfect sample splitting using a <60 mesh sample size in some samples.
Research continues to assess relationships between mercury content in coal and other measured chemical and physical parameters and topical studies related to mercury mineralization in coals of Guizhou Province.
References
Dastoor, A.P., Larocque, Y., 2004, Global circulation of atmospheric mercury: a modeling study: Atmospheric Environment, v. 38, p. 147-161.
Streets, D.G., Hao, J., Wu, Y., Jiang, J., Chan, M., Tian, H., Feng, X., 2005, Anthropogenic mercury emissions in China, v. 40, p. 7789-7806.
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