Proceedings of the 9th Annual West Virginia Surface Mine Drainage Task Force Symposium, April 25-26, 1989. Morgantown,WV: West Virginia University, 1989 Apr; :1-18
Acid mine drainage (AMD) results from the oxidation of pyrite that has been exposed to air and water by surface mining activities. This study reports the results of column leaching tests of pyrite oxidation and their relationship to field abatement techniques. Research focused on determining the effect of oxygen, leaching frequency, and weathering on the biotic oxidation rate, as well as the effect of oxygen on the abiotic rate. Both small (40-cm-long by 2.54-Cm-id) and large (1.92-M-long by 0.29-M-id) columns were used. The small columns contained 5 g of pyrite mixed with 100 g of silica sand, the large columns 175 kg of unweathered pyritic shale analyzing 3.5 pct s. Biotic oxidation of pyrite at o2 levels of 0.5, 1.0, 5.0, and 10.0 pct were 12.9, 15.2, 13.2, and 16.0 Mg so4 2- /day respectively. Abiotic rates at o2 levels of 0.5, 5.0, 9.6, And 14.5 pct were 1.9, 8.3, 11.0, and 14.9 Mg so4 2-/day. This suggests that unless the bacteria are inhibited, pyrite oxidation proceeds at about the same rate for any o2 level above 0.5 pct. In the large column, for unsaturated leaching, the oxidation rate was 18.2 Mg so4 2-/day. In another test, comparison of leachates from fresh material to weathered (26 pct less s) showed no difference in release rates of so4 (14.4-13.1 G/day), fe (4.26-4.20 G/day), or al (0.29-0/27 G/day), but weathered values for mn, ca, mg, and na were reduced to 12.6, 23.2, 4.3, and 56.2 pct, respectively, of fresh values. Leaching frequency tests of 1 l every day, 7 l every 7 days, 14 l every 14 days, and 21 l every 21 days showed no differences.