Modes of occurrence of environmentally-sensitive trace elements in coal

The modes of occurrence of 25 elements of environmental concern are reviewed. For each element there is a brief description of the relevant research on its modes of occurrence in coal, an indication of the most likely modes of occurrence, and an estimation of the level of confidence in the assessment of its modes of occurrence. The estimated level of confidence will be a numeric value from 1 to 10, with 10 indicating the highest level of confidence and 1 indicating no confidence. This estimate is based, in large part, on whether the modes of occurrence were determined by direct or indirect methods. 110 refs., 1 fig., 1 tab