Chemical mobility of potentially toxic trace elements in coal at surface conditions
煤中部分潜在毒害微量元素在表生条件下的化学活动性

The mobility of 10 potentially toxic trace elements (PTTE) (As,Cd,Cr,Cu,Hg,Ni,Pb,Se,Tl and Zn) from 32 coal samples of Longtan Group formed in Permian Period in Guizhou Province, China was investigated using sequential extraction procedures. The results demonstrate taht Hg, As, Se, Cd, Cu and pb have the highest mobility at surface conditions, and the average extractable fractions of them are 83 8%,93.5%,80.3%,63.3% 71.1% and 86.8% of the total, respectively. The elements in cloal with the lowest leachability include Tl, Cr, and Ni, and the average extractable fractions of them are 22 9%,19.7% and 25.7%, respectively. Zinc has an intermediate behavior, and the average leachable fraction is 46.6%. The results demonstrated that mobility of PTTE in coal depends on the mode of occurrence of these elements. The elements associated with sulfates, carbonates, sulfides and some organic matter in coal show the highest extraction rates during weathering process, while elements with silicate affinities are inert at surface conditions.