SELENIUM CONCENTRATIONS IN COAL AND ASSOCIATED STRATA IN MINE CORES FROM SOUTHERN WEST VIRGINIA

The concentration of total Se was measured in nearly 400 samples collected from five cores taken from a southern West Virginia coal mine. The cores span the Coalburg and Winifrede coal beds of the Middle Pennsylvanian upper Kanawha Formation. The dataset included coals, shales, mudstones, and sandstones. The coals and shales typically contained the highest concentrations of Se while the sandstones had the lowest concentrations. No statistically significant correlation was found between total Se and total sulfur for the entire dataset or any individual rock type. Nearly all of the samples with greater than 5 mg/kg Se were found in rocks with paste pH values between 7 and 9 and a net neutralization potential, although not all of the rocks with those characteristics contained high Se. The highest concentrations of Se in non-coal rocks were found in strata located within 0.5 meters of a coal bed. The maximum concentration of Se detected was 11.9 mg/kg in a shale located between two coal layers. Selective extractions were conducted on over 50 samples from one rock core to evaluate the mode of occurrence for Se. Based on those tests, Se is most likely present in either the organically-bound or sulfide-bound fraction. There was no clear distinction in the mode of occurrence from rocks proximate to or further from the coal layers.