Microbial and Geochemical Characterization of an Acid-Generating Hard Coal Tailings Dump in Saxonia/ Germany

An enhanced entry of heavy metals and metalloids into ground and surface water was observed in the historical hard coal mining areas of the districts of Zwickau and Lugau/ Oelsnitz in Saxonia, Germany. Heavy metals and metalloids like Mn, Co, Ni, Zn, As and Cd are enriched in the surface waters of the district. This environmental impact is observed even though a recultivation of some of the dumps occurred partially already 50 years ago. In this study, preliminary microbial and geochemical characterizations of samples from drilling cores in different depths of a dump site, of surface and ground water samples, and of sediments are described. Thiobacillus denitrificans appeared to be a dominating species in these moderately acidic environment especially where there is nitrate infiltration and inflow, respectively, due to agricultural use of the adjacent area. Some of the sediment samples also contained high counts of iron- and sulfate-reducing bacteria due to the organic detritus on the sediment surface.