Environmental impact after 30 to 60 years of remediation: microbial investigation of hard coal mining dumps in Germany

Important groups of microbes were investigated in three hard coal mining dumps in Saxonia/ Germany. In the particular dumps, different chemophysical and geochemical conditions are existing, depending on the kind of remediation tip to six decades ago. Thiobacillus denitrificans, iron and sulfate reducers, and general aerobic heterotrophs and fungi were counted by MPN and CFU methods. Samples were taken from drilling cores in different depths out of the dumps, from seepage-, surface- and ground waters and from sediments. Similarities and significant differences were found between the microbial populations of the three dumps, depending on the appropriate environmental conditions. As a result, enhanced counts of T. denitrificans were detected at all three sites, originating from fertilizers (agricul-ture, gardens) and atmospheric precipitations. Sulfate reducers and aerobic heterotrophic microorganisms are suited indicators for the ongoing biogeochemical processes in the dumps.