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57Fe-Mossbauer studies of sediment cores from Integrated Field-Scale Subsurface Research Challenge Site at Rifle, Colorado

EMSL Project ID


The U.S. DOE faces the challenge of cleaning up and/or monitoring large, dilute plumes contaminated by metals, such as U, Tc, Pu, Hg, Cr, etc, whose mobility and solubility change with aquifer redox status. At the Uranium Mill Tailings Site (UMTRA) in Rifle, CO, field-scale experiments with acetate as electron donor have stimulated metal reducing bacteria to remove soluble U(VI) from the groundwater. The shallow depth to groundwater (3-4 m), thin saturated zone (~2.5 m), and well-defined groundwater flow at the site facilitated the monitoring of microbial and geochemical processes which led to following important findings: a) initial loss of U(VI) from the groundwater is coincident with an enrichment in Geobacter species (a Fe-reducer), and b) rebound in soluble U(VI) on an apparent switch of the aquifer from Fe-reducing to sulfate reducing conditions with simultaneous precipitation of Fe-sulfide phases of unknown nature.

The purpose of the EMSL proposal is to take advantage of 57Fe-specific Mossbauer spectroscopy technique to primarily investigate Fe-mineralogy of sediment cores obtained from the field site under various biostimulated conditions to gain insights into Fe-mineral (bio)transformation and its implications on long-term U(VI) removal from the groundwater. Understanding this and behavior of site-specific, geochemical, and microbiological conditions is critical to the design of optimal biostimulation strategies for prolonging uranium bioremediation.

Project Details

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Principal Investigator

Ravi Kukkadapu
Environmental Molecular Sciences Laboratory

Team Members

Zihua Zhu
Environmental Molecular Sciences Laboratory

Chongmin Wang
Environmental Molecular Sciences Laboratory

Nikolla Qafoku
Pacific Northwest National Laboratory

Bruce Arey
Pacific Northwest National Laboratory

Related Publications

Yang J, RK Kukkadapu, H Dong, ES Shelobolina, J Zhang, and J Kim. 2012. "Effects of Redox Cycling of Iron in Nontronite on Reduction of Technetium." Chemical Geology 291:206-216. doi:10.1016/j.chemgeo.2011.10.013