Microbial mobilization of hazardous metals and bioremediation of water and soils

The microbial influence on metal mobilization in freshwater sediment was investigated. Water-sediment columns of both in situ and in the laboratory demonstrated that when cadmium (Cd) was added to the water column. Cd disappeared gradually from the water and was sorbed by the surface sediment. Cd continued to mobilize down the sediment column over time to approximately 12 cm below the sediment surface. Studies using autoclaved soil resulting in reduced microbial population showed very little migration of the metal down the sediment column. Autoclaved soil reinoculated with a mixed culture of the sediment isolates demonstrated mobilization of the metal, similar to the natural, nonautoclaved counterpart.;Bioprocesses are being developed for concentration and removal of various heavy metals from water and soil. For bioremediation of metal-containing water, this report demonstrated that alginate beads crosslinked with polyethyleneimine effectively sorb lead and bismuth from solution and lesser amounts of cadmium, thorium, and uranium. Zoogloea ramigera strain 115, when immobilized in alginate beads, markedly increased the amount of cadmium, thorium, and uranium removal from mixed, single metal or single metal solutions exposed to the same beads sequentially.;Several microbial nutrients and biochemicals were used in conjunction with microorganisms to determine the influence of microorganisms on the release of Bi, Cd, Pb, Th, and U from soil. The overall results indicate that cysteine, a reducing as well as a metal chelating agent is the most effective. The highest amount of Bi and Pb release occurred within 1 day and the metals were "re-adsorbed" over time. Release of U increased over time. Only negligible amounts of Cd and Th were released. Release of metals from autoclaved soil with reduced microbial population was substantially lower than that from nonautoclaved soil with unaltered microbial population. The Eh and pH effect on metal release is inconclusive. Microbial metabolites may be solely responsible for metal release in all Eh and pH ranges.