Using complex resistivity imaging to infer biogeochemical processes associated with bioremediation of a uranium-contaminated aquifer
Experiments at the Department of Energy’s Rifle Integrated Field Research Challenge (IFRC) site near Rifle, Colorado (USA) have demonstrated the ability to remove uranium from groundwater by stimulating the growth and activity of Geobacter species through acetate amendment. Prolonging the activity of these strains in order to optimize uranium bioremediation has prompted the development of minimally-invasive and spatially-extensive monitoring methods diagnostic of their in situ activity and the end products of their metabolism. Here we demonstrate the use of complex resistivity imaging for monitoring biogeochemical changes accompanying stimulation of indigenous aquifer microorganisms during and after a prolonged period (100+ days) of acetate injection. A thorough raw-data statistical analysis of discrepancies between normal and reciprocal measurements and incorporation of a new power-law phase-error model in the inversion were used to significantly improve the quality of the resistivity phase images over those obtained during previous monitoring experiments at the Rifle IRFC site. The imaging results reveal spatiotemporal changes in the phase response of aquifer sediments, which correlate with increases in Fe(II) and precipitation of metal sulfides (e.g., FeS) following the iterative stimulation of iron and sulfate reducing microorganism. Only modest changes in resistivity magnitude were observed over the monitoring period. The largest phase anomalies (>40 mrad) were observed hundreds of days after halting acetate injection, in conjunction with accumulation of Fe(II) in the presence of residual FeS minerals, reflecting preservation of geochemically reduced conditions in the aquifer – a prerequisite for ensuring the long-term stability of immobilized, redox-sensitive contaminants, such as uranium.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1021821
- Report Number(s):
- PNNL-SA-79133; 5397; KP1702030; TRN: US1104052
- Journal Information:
- Journal of Geophysical Research. Biogeosciences, 116:Article No. G03001, Vol. 116
- Country of Publication:
- United States
- Language:
- English
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Acetate availability and its influence on sustainable bioremediation of uranium-contaminated groundwater
Stimulating the In Situ Activity of Geobacter Species to Remove Uranium from the Groundwater of a Uranium-Contaminated Aquifer
Related Subjects
ACETATES
AQUIFERS
BIOREMEDIATION
COLORADO
IRON
METABOLISM
MICROORGANISMS
MONITORING
PRECIPITATION
PRESERVATION
SEDIMENTS
STABILITY
STIMULATION
STRAINS
SULFATES
SULFIDES
URANIUM
USA
subsurface imaging
complex resistivity
biogeochemistry
bioremediation
uranium-contaminated aquifer
Environmental Molecular Sciences Laboratory