Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

The former uranium mine Königstein is currently in the process of remediation. The underground is flooded in a controlled way. Despite high uranium concentrations up to 13 mg/L and a low pH of 2.9, these waters contain a high microbial diversity [1]. Microorganisms are known to interact with metals and radionuclides in different ways [2]. For instance, anaerobic sulfate-reducing bacteria (SRB) reduce U(VI) to U(IV) and thus change the migration behavior from the more soluble U(VI) into the insoluble U(IV) [3]. By culture dependent methods it was possible to isolate anaerobic microorganisms from the flooding water. They were incubated with 10 mM glycerol using the flooding water as background solution. During an incubation time of six weeks the redox potential decreased from 660 mV to 300 mV. The cells were separated from the incubation medium by centrifugation and analyzed by U-LIII edge EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements. Iterative Target-Factor Analysis (ITFA) revealed that 100 % of U(VI) was reduced to U(IV). The results show that naturally occurring anaerobic microorganisms within the flooding water of the former uranium mine Königstein are able to reduce U(VI) to U(IV).

[1.] Zirnstein, I., Charakterisierung der mikrobiellen Biozönose im sauren Grubenwasser des ehemaligen Uranbergwerks Königstein, Institut für Ressourcenökologie, Dissertation, 2015, TU Dresden: Dresden.
[2.] Lloyd, J.R.M., L. E. , Interactions of microorganisms with radionuclides. Elsevier Science. 2002.
[3.] Lovley, D.R., et al., Enzymatic Iron and Uranium Reduction by Sulfate-Reducing Bacteria. Marine Geology, 1993. 113(1-2): p. 41-53.