Containment of toxic metals and radionuclides in porous and fractured media: Optimizing biogeochemical reduction versus geochemical oxidation. 1998 annual progress report

'The purpose of this research is to provide an improved understanding and predictive capability of the mechanisms that allow metal-reducing bacteria to be effective in the bioremediation of subsurface environments contaminated with toxic metals and radionuclides. The study is motivated by the likelihood that subsurface microbial activity can effectively alter the redox state of toxic metals and radionuclides so that they are immobilized for long time periods. The objectives are to: (1) develop an improved understanding of the rates and mechanisms of competing geochemical oxidation and microbiological reduction reactions that govern the fate and transport of redox-sensitive metals and radionuclides in the subsurface, and (2) quantify the conditions that optimize the microbial reduction of toxic metals and radionuclides, for the purpose of contaminant containment and remediation in heterogeneous systems that have competing geochemical oxidation, sorption, and organic ligands. The overall goal of this project is to use basic research to develop a cost effective remediation strategy that employs in-situ contaminant immobilzation. Specifically, the authors will develop active biowall technologies to contain priority EM contaminant plumes in groundwater. This report summarizes work after 1.5 y of a 3 y project.