An Integrated Approach to Quantifying the Coupled Biotic and Abiotic Mechanism, Rates and Long-Term Performance of Phosphate Barriers for In Situ Immobilization of Uranium
EMSL Project ID
24812
Abstract
Operations related to nuclear energy and weapons production have resulted in numerous areas, worldwide, exhibiting surface and subsurface uranium contamination of geologic media. Within the United States Department of Energy (DOE) complex, uranium has been recognized as one of the most frequently occurring radionuclides in groundwater and soils/sediments For example, at the Hanford site, Washington State, at least seven distinct uranium-contaminated plumes have been identified. Conventional remediation strategies, such as excavation and pump-and-treat, are expensive and have not diminished the magnitude of the uranium plumes. Polyphosphate remediation technology has been identified as the most promising remedial technology to mitigate the uranium contamination in the 300 Area. This will reduce the inventory of available uranium that contributes to the groundwater plume through direct precipitation of the dominant uranium-phosphate mineral autunite, and secondary precipitation of apatite, which will act as a long-term sorbent for the sequestration of uranium. Widespread application of this technology at other DOE sites, that are less oligotrophic than the Hanford site, requires an understanding of the effect of microbial activity on the longevity of key phosphate minerals (i.e., autunite and apatite).Our overall hypothesis is that the durability of autunite and apatite minerals in the presence of microbes will decrease relative to baseline abiotic experiments; thereby, reducing the longevity of phosphate remediation technology for in situ remediation of uranium. In order to provide a scientifically defensible basis for phosphate remediation of uranium, the effect of microorganisms on the weathering stability of autunite and apatite must be quantified. Borehole activities within the 300 Area aquifer of the Hanford site will be utilized to obtain sedimentary material which has been subjected to phosphate remediation technology for the immobilization of uranium. An integrated experimental and computational approach will be used to determine the affect of dominant microbial metabolites on the long-term durability of autunite and apatite. Matrix assisted laser desorption /ionization-time of flight mass spectrometry (MALDI-TOF) will be utilized to identify microbial metabolites which effect the durability of autunite and apatite. Dynamic weathering tests will be conducted in the presence of the relevant microbial metabolites to quantify their affect on the durability of autunite and apatite. Interpretation of these experiments will be aided by nuclear magnetic resonance (NMR) and laser-induced photoacoustic spectroscopy (LI-PAS) to determine the speciation of uranium and phosphate in solution. The results obtained from these experiments will (1) provide the fundamental data needed to quantify the effect of microbial activity on the durability of dominant phosphate minerals, and (2) will be incorporated into a kinetic rate equation that will allow reactive transport codes to model the long-term fate of phosphate amendments for the in situ immobilization of uranium.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-06-07
End Date
2010-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Wellman DM, EM Pierce, DH Bacon, M Oostrom, KM Gunderson, SM Webb, CC Bovaird, EA Cordova, ET Clayton, KE Parker, RM Ermi, SR Baum, VR Vermeul, and JS Fruchter. 2008. 300 Area Treatability Test: Laboratory Development of Polyphosphate Remediation Technology for in Situ Treatment of Uranium Contamination in the Vadose Zone and Capillary Fringe, Pacific Northwest National Laboratory, Richland, WA
Wellman DM, LR Reed, and K Malatova. submitted. "Effect of Microbial Activity on the in Situ Immobilization of Uranium Via Phosphate Amendments." Chemosphere.