Investigation of the long term influence of microbial activity on gas–phase ammonia based remediation of vadose zone uranium contamination using electrical geophysical methods.
EMSL Project ID
48791
Abstract
During years of activity at the Hanford site various locations were contaminated with uranium. At several disposal sites this contamination may be too deep and costly to dig up and may also increase workers risk of exposure. If left without treatment uranium can be somewhat mobile in the vadose zone and can potentially be carried downward to the water table by infiltrating water. A method using gas-phase ammonia has been developed at PNNL to reduce uranium mobility. This method uses the high pH conditions from gas-phase ammonia partitioning into the pore water to dissolve minerals on the grain surface. After these dissolved minerals precipitate, much of the uranium has been shown to shift from mobile mineral states to much less mobile mineral states. This study investigates the influence of microbial activity on the long term performance of gas-phase ammonia based remediation of vadose zone uranium contamination in support of the Hanford Site U8 crib field test. For this study, three columns will be packed with unsaturated (4% WC) clean Hanford sediment: One will be inoculated with typical soil microbes and doped with a carbon source, the second will just be inoculated with the same soil microbes, and the third will not have any added soil microbes (control). Gas-phase ammonia will be injected into one end of each column until 1/3 of the column pore water has reached equilibrium with gas-phase ammonia. Because of ammonia’s high affinity to water a sharp ammonia front is expected. These columns will be monitored with complex resistivity and by extracting soil samples at both the treated and untreated ends of the column. These samples will be extracted over a 4 month period and used for microbial analysis and aqueous chemistry analysis. The collected laboratory data from these experiments will enable geophysical monitoring data to be interpreted in terms of microbial functions that may influence long-term remediation performance. For this study to be successful, the flow cells and gas injection system in EMSL 1329 and powder XRD analysis of the porous media are greatly needed.
Project Details
Start Date
2015-03-09
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members