Distribution and mode of occurrence of As, Hg and Se and Sulfur in coal Seam 3 of the Shanxi Formation,Yanzhou Coalfield, China

The Yanzhou mining area in the west Shandong Province, China contains coals of Permian and Carboniferous age. A total of 21 bench coal samples were collected from coal seam 3 of the Permian Shanxi Formation, Xinglongzhuang coal mine, Yanzhou Coalfield, China. Pyritic and organic sulfur generally account for the bulk of the sulfur in coal. In this paper, the distribution and concentration of sulfur in the Yanzhou mining district are analyzed, and the forms of sulfur are studied. Organic sulfur content was determined by substraction and it is positively correlated to total and pyritic sulfur.The vertical variation of Hg, As and Se and sulfur contents in coal seam 3 of the Shanxi Formation in the Xinglongzhuang mine show that all these trace elements are enriched in the roof and floor rocks of the coal bed and that the concentrations are also relatively high in the clay partings within the coal bed. In the studied samples, Hg and Se have an even higher concentration than that in the world coals. The concentrations of Hg and Se in the seam studied are greater than the global mean of these elements in coals. Se content in the studied coal is 5 times as high as the world coal value and Hg is about one to two orders of magnitude above World Clarke value. Hg is also more enriched compared to the average concentration in Chinese coals.The pyritic sulfur is positively correlated with total sulfur, and both are enriched in the roof rock, floor rock and clay parting of the coal bed. The concentrations of the trace elements As, Hg and Se are closely related to sulfur. Hg correlates more with pyritic sulfur than organic sulfur. Se relates more to organic sulfur than to pyritic sulfur. As is almost equally related to organic sulfur and pyritic sulfur. Therefore three trace elements may be mainly associated with sulfides and other inorganic matter, also occur in organic forms, especially for Se, already sard this.