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Laboratory Seeks to Solve Uranium Migration Mysteries in Washington and Colorado

April 2007
DOE Commits $27.5M for Uranium Contaminant Transport Field Studies The U.S. Department of Energy recently granted Pacific Northwest National Laboratory $27.5 million dollars over 5 years to investigate the movement of contaminated groundwater at sites in Washington and Colorado. These two field research studies are funded by DOE's Office of Science and are intended to identify new approaches and strategies to help resolve questions about the movement of subsurface contaminants. PNNL will lead the field studies at the Hanford Site in Richland, Washington, and at a uranium mill tailings site in Rifle, Colorado. Hanford Field Study Complements DOE Office of Environmental Management Investments: The Hanford study involves characterization and instrumentation of field sites to investigate the groundwater and the vadose zone -- or the subsurface soil and rock just above the groundwater -- both of which are contaminated by uranium. The study area is adjacent to the Columbia River and located near the southern boundary of the Hanford Site, north of Richland. Pacific Northwest National Laboratory Project Manager John Zachara says the field study at Hanford is perfectly suited for closely examining the processes controlling uranium migration in a complex subsurface environment. "It brings to bear the best science available, and will help us resolve questions about the movement of subsurface contaminants at Hanford and other DOE sites." The five-year research project will help develop transport models that will be relevant and applicable to contaminant movement along the entire Columbia River corridor, according to Zachara. A team of scientists from PNNL and researchers from three other DOE laboratories, four universities and the U.S. Geological Survey are involved. DOE contractor Fluor Hanford is responsible for remediating the groundwater and deep vadose zone in this area. The Hanford field study complements investments by the DOE Office of Environmental Management to investigate an innovative cleanup approach for the uranium. "It's a collaborative effort that benefits both endeavors," Zachara said. "Merging both the cleanup and research activities will allow us to integrate new information and data, and apply it to design and implement a more effective and efficient remediation effort." Mike Thompson, a scientist with the DOE Richland Operations Soil and Groundwater Remediation Project, believes the field study will yield important data to support future decision making for environmental remediation. "Results from the study will be extremely useful to the regulators, stakeholder groups and DOE when conducting evaluations of the remedial action alternatives under consideration, and when we ultimately determine our desired course of action," he said. Rifle, Colorado, Field Study Studying Stimulation of Subsurface Microorganisms to Immobilize Uranium: The second of the two studies is located in Rifle, Colorado. Both the Hanford and Colorado studies are part of DOE's Integrated Field-Scale Subsurface Research Challenge, a new program that commits multi-investigator teams to performing large, benchmark-type experiments on formidable field-scale science issues. At the uranium mill tailings site in Colorado, PNNL geohydrologist Phil Long leads a diverse team of researchers examining the stimulation of subsurface microorganisms aimed at reducing and immobilizing uranium in the subsurface. Researchers have found that bioremediation of uranium is possible, but optimal control and manipulation of the process is still unknown. Understanding this process for controlling uranium mobility is critical in designing an effective bioremediation effort, according to Long. "We hope to understand the microbial factors and the associated geochemistry that is controlling uranium movement, so that DOE can confidently remediate the uranium plumes," he said. "Our approach should lead to new knowledge that can then be used to develop effective flow and reactive transport models." Researchers look forward to initial analysis of microbial protein expression during field-scale bioremediation. These data will make it possible to learn what nutrient factors are most important for achieving maximum rates of uranium reduction and removal from groundwater. Robert Baney, director of the Office of Legacy Management, Office of Site Operations for DOE, states, "Innovative tools are likely to emerge from this research including rapid proteogenomic analysis of complex microbial communities that can be used to assess the status of bioremediated sites. Clearly this research has the potential for positive benefit that extends far beyond the Rifle site." Funding Source: Funding for the field studies is provided by the DOE Office of Biological and Environmental Research's Environmental Remediation Sciences Division within the Office of Science. Portions of the research will be conducted in DOE's Environmental Molecular Sciences Laboratory, a national scientific user facility located at PNNL. Study Participants: Participants in the field studies include the United States Geological Survey, Oregon State University, Purdue University, the University of Alabama, the University of California-Berkley, and DOE's Pacific Northwest, Lawrence Berkley, Los Alamos and Idaho national laboratories.

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