Features of As content,occurrence in coal and its affect on environment in China

Based on the measurement of As content in 156 coal samples from different coal areas and the all sided and systematic collections of 2000 coal samples from the pubished papers,this article analyses the As content and occurrence in coal and the geological factors of As accumulation.Most of the As contents of coals in China are between 0.8×10^-6 and 20×10^-6,and the arithmetic mean is 4×10^-6.The types of As occurrence in coal can be divided to three types: a. isomorphic substituting for S in pyrite in coal; b. cohering with organic matter in low metamorphic coal; c. existing with the carriers,clay minerals or the rare minerals consisting of As.It is not sure that As exists in high metamorphic coal by cohering with organic matter.The geological factors of As accumulation are the followings:①being carried into coal beds by hydrothermal at the latter stages;②being carried into peat marshes by terrigenous sediment;③accumulating with sea water at the depositional stage.Although As is one of the most noxious elements in coal and burning high As coal is the general reason for environmental pollution,the types of burning coal are important.As content in most of coal is not so high that controlling of and preventing from As are not very difficult.