The mean arsenic concentration on a whole-coal basis, for 613 complete channel samples representing 34 coal beds from the central Appalachian basin, is 14.0 ppm (standard deviation, s.d. = 14.9). An F-test for variance equality and the appropriate t-test on the means can separate stratigraphic units into three categories: (1) Kanawha Formation, which has a mean of 5.04 ppm; (2) New River, Pocahontas, and Monongahela Formations, which have means of 10.1, 10.9, and 12.4 ppm, respectively; and (3) Allegheny Formation, which has a mean of 18.1 ppm.

Data from 40 complete channel samples of the Upper Freeport coal bed (Allegheny Formation) were used for statistical evaluations (F- and t-tests as applied in the stratigraphic comparison) of the regional (western Pennsylvania) versus local (within mine) arsenic variation. The arsenic concentration and variation in whole-coal samples are greater on a regional scale (mean = 40.8 ppm, s.d. = 30.6, n = 21) than on a local scale (mean = 23.8 ppm, s.d. = 18.7, n = 19).

Nine channel samples of the Upper Freeport coal bed were subjected to a 21-part size-gravity washability study. A mean of 86 wt. % of the coal floated at a specific gravity of 1.6. The mean arsenic concentration (6.05 ppm) in this float recovery is 55% less than the mean arsenic concentration in the unprocessed samples (14.3 ppm). The mean arsenic concentration in the remaining 14 wt. % of the coal was 123 ppm. The float-sink analysis verified an inorganic affinity of arsenic and indicated that arsenic is associated with pyritic sulfur in the Upper Freeport coal bed. Three samples with a mean arsenic concentration of 4.20 ppm had a mean of 36.4% reduction of pyritic sulfur, while 6 samples with a mean arsenic concentration of 19.3 ppm had a mean of 63.8% reduction of pyritic sulfur. C ncentrations of arsenic in complete channel samples above some threshold, approximately 10 ppm for these samples, appears to be associated with removable pyrite.

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