Laboratory investigations on the interactions of soil, water and microorganisms with manganese

Column experiments were carried out using contaminated geosubstrates and previously isolated Streptomyces strains from the former uranium mining area Ronneburg (Germany) to study transfer processes of heavy metals including radionuclides. Preliminary tests with comparatively low heavy metal and radionuclide contaminated surface material showed strongly elevated Mn concentrations up to 1060 mu g/l after passage through inoculated columns. In contrast, the eluates of non inoculated columns showed, after a "first flush", low Mn concentrations around 30 mu g/l. Poisoned control columns showed decreasing concentrations after the "first flush" (maximum Mn release of 540 mu g/l). Highest manganese release from the inoculated, non poisoned columns corresponded with strongly decreasing redox potentials (+200 to -270 mV), which probably indicates microbially catalysed manganese release through reductive processes. One of the strains isolated from the column material was identified as a potentially heavy metal resistant strain of Cupriavidus metallidurans. It showed tolerance of up to 30 mM Mn (II), however no aerobic Mn (IV) reduction processes were indicated.