Quantification of microorganisms involved In cemented layer formation in sulfidic mine waste tailings (Freiberg, Saxony, Germany)

摘要

Cemented layers predominantly consisting of gels/poorly crystalline mineral phases have been formed as a consequence of mineral weathering in sulfidic tailings near Freiberg, Saxony, Germany. These layers function as natural attenuation barrier for toxic compounds and reduce oxidation and erosion processes of tailings surfaces. Quantitative molecular biological and cultivation methods were applied to investigate the role of microorganisms for mineral weathering and cemented layer formation. High resolution depth profiles of numbers of microorganisms showed maximal cell numbers in the oxidation zone where cemented layers had been formed. Highest total cell numbers of >10~9 cells g~(-1) dry weight (dw) were detected by SybrGreen direct counting. Using quantitative real-time PCR (Q-PCR) between 10~7 and 10~9 Bacteria g~(-1) dw and up to 10~8 Archaea g~(-1) dw were determined. As well high numbers of cultivable and living Bacteria could be detected by MPN (most probable number) for Fe(II)- and S-oxidizers and CARD-FISH (catalyzed reporter deposition - fluorescence in situ hybridization). Overall, the high numbers of microorganisms determined with various quantification techniques argue for a significant role of microorganisms in cemented layer formation due to microbial mineral weathering. It is hypothesized that EPS (extracellular polymeric substances) mediate the formation of secondary mineral phases.