SUBSURFACE CONTAMINANT RESEARCH AT THE OAK RIDGE ENVIRONMENTAL REMEDIATION SCIENCES FIELD RESEARCH CENTER

Multidisciplinary teams of researchers from across the United States and overseas working at the Environmental Remediation Science Field Research Center (FRC) in Oak Ridge have shown that microorganisms found in subsurface environments can be used to reduce health risks at DOE waste sites by transforming radionuclides, such as uranium and technetium, and other contaminants into chemical forms that are less mobile or less toxic in groundwater. FRC researchers found that introducing naturally occurring humic substances (organic matter found in soil) can accelerate the chemical reduction and immobilization of these contaminants. At the same time, the researchers demonstrated that co-contaminants in the subsurface, such as nitrate, and elevated concentrations of other chemicals, like calcium, can inhibit the chemical reduction process and can reoxidize uranium, making it more mobile.

Extensive work has been conducted to identify the microorganisms present in the harsh FRC subsurface environment (an environment that is acidic and that contains high concentrations of nitrate and metals that tend to be toxic to most microorganisms). Work conducted to date has begun to determine which specific microorganisms can be used to promote the chemical reduction of radionuclides directly or indirectly. This research relies on genomic sequencing; cutting-edge techniques such as the use of functional gene arrays; and such novel devices as “bug traps,” coupons that trap microbes below the ground's surface.

In addition to investigating naturally occurring microbial communities in the FRC's subsurface, researchers have used novel geophysical, hydraulic, and tracer techniques for characterizing and monitoring subsurface processes and groundwater flow. For example, seismic and resistivity techniques are used to create three-dimensional images of the subsurface geology and of contaminated groundwater plumes. Taken together, FRC research findings have contributed to the DOE Office of Biological and Environmental Research goal of understanding the processes that influence the transport and fate of contaminants, the effectiveness and long-term consequences of extant remediation options, and the development of improved remediation strategies—especially for currently intractable contaminants or conditions.