ABUNDANCE OF IRON-OXIDIZING THIOBACILLI AND BIOLOGICAL SULFUR OXIDATION POTENTIAL FROM SOIL IMPACTED BY COAL AND COAL REFUSE PILES

This study was conducted to assess the abundance of iron-oxidizing bac teria and biological sulfur oxidation potential from soil impacted by coal and coal refuse from two coal-burning electric power facilities l ocated at the U.S. Department of Energy's Savannah River Site (Aiken, S.C.) and the South Carolina Electric and Gas Site at Beech Island, S. C. Significantly higher MPN counts of iron-oxidizing bacteria were ob tained from samples collected at the confluence of a coal storage runo ff containment basin, a coal reject (refuse) pile, and an adjacent wet land at the Savannah River Site. Significant differences in pH, sulfat e-S, ferrous- and ferric-iron were also obtained between sampling loca tions. No significant differences in ferric/ferrous ratios were determ ined. These ratios however, exceeded a value of 2.0 when sample pH val ues were less than 4.5. Under optimal conditions, biological thiosulfa te-S oxidation potentials (in vitro) showed a 4- to 7-day lag in the a ppearance of sulfate-S, and a final pH (after twenty-four days of perf usion) of 1.97 to 3.90. These results indicate that contamination of s ubsurface water by acidic leachate derived from thionic bacterial acti vity will occur if coal and coal refuse piles are not confined by an i mpermeable surface or containment facility.