Mobility of Source Zone Heavy Metals and Radionuclides: The Mixed Roles of Fermentative Activity on Fate and Transport of U and Cr. Final Report

[摘要] Various U. S. Department of Energy (DOE) low and medium-level radioactive waste sites contain mixtures of heavy metals, radionuclides and assorted organic materials. In addition, there are numerous sites around the world that are contaminated with a mixture of organic and inorganic contaminants. In most sites, over time, water infiltrates the wastes, and releases metals, radionuclides and other contaminants causing transport into the surrounding environment. We investigated the role of fermentative microorganisms in such sites that may control metal, radionuclide and organics migration from source zones. The project was initiated based on the following overarching hypothesis: Metals, radionuclides and other contaminants can be mobilized by infiltration of water into waste storage sites. Microbial communities of lignocellulose degrading and fermenting microorganisms present in the subsurface of contaminated DOE sites can significantly impact migration by directly reducing and immobilizing metals and radionuclides while degrading complex organic matter to low molecular weight organic compounds. These low molecular weight organic acids and alcohols can increase metal and radionuclide mobility by chelation (i.e., certain organic acids) or decrease mobility by stimulating respiratory metal reducing microorganisms. We demonstrated that fermentative organisms capable of affecting the fate of Cr6+, U6+ and trinitrotoluene can be isolated from organic-rich low level waste sites as well as from less organic rich subsurface environments. The mechanisms, pathways and extent of contaminant transformation depend on a variety of factors related to the type of organisms present, the aqueous chemistry as well as the geochemistry and mineralogy. This work provides observations and quantitative data across multiple scales that identify and predict the coupled effects of fermentative carbon and electron flow on the transport of radionuclides, heavy metals and organic contaminants in the subsurface; a primary concern of the DOE Environmental Remediation Science Division (ERSD) and Subsurface Geochemical Research (SBR) Program.

[发布日期] 2014-01-29

[学科分类] 核能源与工程

[关键词] Low level waste;heavy metals;radionuclides;fermenting organisms;cellulose;Cellulomonas;Arthrobacter;Yarrowia;chromium;uranium;trinitrotoluene;TNT;toxicity;reduction;precipitation;iron reduction;electron shuttle;Ecology;Biobarriers