IMPACT OF WESTERN COAL MINING .2. MICROBIOLOGICAL STUDIES

The occurrence and activity of certain groups of sulfur cycle bacteria associated with waters, sediments, and the coal bearing strata of a coal strip mine at Decker, Montana, were studied. Mining areas in northeastern Wyoming were also examined. Thiobacillus ferooxidans, one of the major contributors to acid mine drainage, was consistently detected in the mining environment. Physiological studies of T. ferrooxidans isolates indicated that these acidophilic iron and sulfur oxidizing organisms were typical of the species in their preference for low pH and ability to oxidize pyrite. Since (i) acidic conditions were not observed at Decker, (ii) the organisms did not multiply in mine water environments and (iii) no acid could be formed from coal samples inoculated with a T. ferrooxidans isolate, it was thought that their activity was limited to microzones in the coal bearing strata where they oxidized sulfuritic material. Any acid formed was quickly neutralized by mineral carbonates associated with the groundwaters and overburden. Sulfate reducing bacteria also were common in the mine waters and sediments. These organisms were particularly active in the sedimentation pond sediments as was evidenced by the rapid rate of conversion of radio-labeled sulfate to sulfide. The hydrogen sulfide produced by these organisms contributed to heavy metal precipitation in the sedimentation pond. © 1979.