2002 RESEARCH PROJECTS NABIR Environmental Management PROJECT: In-line Uranium Immunosensor PRINCIPAL INVESTIGATOR: Diane A. Blake   NABIR Environmental Management In this study, the Blake laboratory at Tulane, in conjunction with Sapidyne Instruments, Inc., will develop an in-line immunosensor with the ability to monitor the removal of hexavalent uranium (or other radionuclides) from a groundwater sample over a period of 4-7 days. This new sensor will have advantages over current methods of detection, which require periodic sampling and analysis off-site. This sensor will operate autonomously and provide data about in situ uranium immobilization in the absence of personnel at the site. The idea for this project was the result of discussions between the P.I. and other scientists performing in situ stabilization experiments at the NABIR Field Research Center (FRC), and this site is proposed for the testing and initial deployment of the sensor. During previous DOE funding, the Blake laboratory developed monoclonal antibodies that recognize hexavalent uranium and incorporated them into a prototype immunosensor that detects uranium at levels of 10 nM (~2.4 ppb). The present project has three major goals: 1) to construct an in-line immunosensor for hexavalent uranium after engineering discussions with the final users; 2) to incorporate the reagents already developed for a handheld immunosensor into this device and test its performance capabilities with hexavalent uranium spiked into buffer and groundwater samples; 3) to test the capabilities of the in-line sensor during the upcoming field tests at the FRC. This project bridges the gap between broad fundamental research and needs-driven applied technology development. Our previous funding allowed us to combine basic studies on antibody binding with instrument design and construction. The current project will allow us to extend this work and deliver an additional assessment technology that will fulfill a specific need of the Subsurface Contaminants Focus Area.   PROJECT: Field Investigations of Lactate-Stimulated Bioreduction of Cr(VI) to Cr(III) at Hanford 100H PRINCIPAL INVESTIGATOR: Terry Hazen   NABIR Environmental Management DOE faces challenging problems in cleaning up 18 major facilities, including those with sites contaminated with hexavalent chromium [Cr(VI)] associated with the production of weapons-grade nuclear materials, plating and boiler operations and equipment repair and fabrication. Cr(VI), which is a strong carcinogen, is highly mobile, whereas trivalent Cr(III) is less hazardous and practically immobile under reduced conditions. Cr(VI), which is widely distributed at one of the most contaminated DOE sites, Hanford, is migrating to the Columbia River. One of the most promising new remediation technologies for chromium-contaminated groundwater is in situ bioreduction. The proposed field project is a direct extension of a NABIR project that received 3 years of support and demonstrated the biogeochemical transport effects of carbon on stimulation of bioreduction of chromium in soil cores, and supports the SCFA Technical Targets, “Metals and radionuclide source zone stabilization and treatment, and Biogeochemical processes that determine contaminant fate.” The overall objective of the proposed project is to carry out field investigations to demonstrate a feasibility of a cost-effective, in-situ remediation technology, using lactate-stimulated bioreduction of dissolved Cr(VI) to form an insoluble mineral precipitation of Cr(III) at the Hanford 100-H area. Specific goals will include: (1) Design of a field test to develop criteria for full-scale deployment of in situ Cr(VI) bioreduction via lactate stimulation for the use at DOE sites, (2) Provide field testing and monitoring (including geophysical methods) the effects of lactate biostimulation on microbial community activity, redox gradients, transport limitations, and other reducing agents, and compare the field results with those of our previous NABIR laboratory work, (3) Assess the kinetic rates and conditions that may cause reoxidation of Cr(III) to Cr(VI) after biostimulation is terminated, (4) Assess the use of bioremediation in conjunction with other alternative remediation technologies, such as a pump-and-treat approach for the Hanford 100-H area. The results of this project will be used to develop a conceptual model of chromium bioreduction in groundwater on a field scale and to provide recommendations for field deployment of lactate-stimulated bioremediation. PROJECT: In Situ Immobilization of 99Tc at the Hanford Site by Stimulation of Subsurface Microbiota PRINCIPAL INVESTIGATOR: Phil Long   NABIR Environmental Management Microorganisms, either directly or indirectly, can alter the oxidation states of uranium and technetium resulting in their precipitation as sparingly soluble solid phases. This process, in concept, can render these contaminants immobile for long time periods. Previous and ongoing NABIR research has established the basic biogeochemical principles underlying the direct and/or Fe(II)-facilitated reduction of 99Tc by microbes. The objective of this project is to evaluate the applicability of these principles to the problem of groundwater contamination by 99Tc at the Hanford Site. 99Tc is a radionuclide that contributes significantly to estimates of future human health risk at Hanford because of its longevity and mobility in the subsurface environment. It exists at high concentrations (up to 30,000 pCi/L) in the central areas of the site where the groundwater table is deep, and is predicted to move to the Columbia River within the next decade. It also has been observed at lower concentrations (600 pCi/L) in shallow groundwater near the river in the 100 H area. This project focuses on laboratory studies to establish the existence and metabolic requirements of microorganisms native to Hanford sediments that are capable of directly or indirectly mediating Tc(VII)O42- reduction. If lab-scale experiments are successful, biostimulation tests using a single-well push-pull approach will be used to evaluate the viability of in situ reduction of 99Tc by native microorganisms (in collaboration with Jack Istok, Oregon State University), and a field-scale biostimulation experiment will be designed. This project will determine if bioremediation of 99Tc is feasible and ultimately may lead to low-cost reduction of risk from 99Tc at the Hanford Site. Currently, we are performing initial experiments on samples of the Ringold Formation recently collected from a saturated subsurface zone contaminated with U and Tc. Sediment samples have been used in microcosm experiments and microbial enrichments to probe for the presence of microorganisms capable of reducing TcO42- or Mn and Fe. Microcosms have been amended with various electron donors including acetate, lactate, formate, or glucose with and without nitrogen and phosphorous amendment. Metal reducing activity will be monitored in these microcosms over time and those exhibiting activity will be used to establish microbial enrichments for the specific type of metal reducing activity identified. Samples of the Hanford Formation from the subsurface of 100 H Area will be collected later this year for use in biostimulation experiments. 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