Study Of Hazardous Trace Elements As And Hg From The Donglin Mine In Chongqing, China

In order to investigate the contents and modes of occurrence of As and Hg in the Nos.4and6coals from the Donglin mine in Chongqing, and to provide scientific basis for rational exploitation and utilization of coal resources,29coal samples were collected (25coal samples and4rock samples), the contents and modes of occurrence of As and Hg were analyzed by various methods. Finally, the origins of carrier of As and Hg were discussed based on depositional environment of coal-bearing measure in this area.The concentrations of As and Hg were determined by the inductively coupled plasma mass spectrometry (ICP-MS) and AMA245mercury detector, respectively. The average As concentration in the Donglin coal is1.85μg/g, ranging from0.19to7.87μg/g, and average Hg concentration in Donglin coal is0.54μg/g, varing from0.11to3.3μg/g. The As concentration is at a low level compared to its Clarkes of world coals, while the Hg is at normal level. Arsenic and Hg are slightly enriched or enriched in major coal samples, which could be concluded from the enrichment factor related to their contents in the crust. It is obviously that the As content is low comparison with coal in Changhebian mine, Songzao, southwestern China (Chongqing, Guizhou, Yunnan, and Sichuan), China, America, Australia, and world coals. But the Hg content is only lower than Songzao, Chongqing, and Sicuan coals. In addition, the concent of As and Hg in No.4coalbed both slightly bigger than No.6coals. The As and Hg concentrate in the roof, upper, middle and lower coal seam in No.4coalbed, respectively. In No.6coalbed, As and Hg concentrate in the roof, floor and lower coal seam.The modes of occurrence of As and Hg in the coals from Donglin mine were studied by correlation analysis, factor analysis and hierarchical cluster analysis. Relations of As and Hg in coal to ash yields, total sulfur, forms of sulfur, and selected major elements are complicated. Finally, the main forming factors of syngenetic pyrite were analyzed combining the coal stratum sedimentary environment. Results indicated that As and Hg in coals are obviously chalcophile and they may be existed in sulfate and syngenetic pyrite mineral of coals.