U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights


How Iron in Minerals Affects Subsurface Uranium
Published: August 01, 2012
Posted: October 18, 2012

Subsurface minerals help control the chemical form of contaminants such as uranium (U). The redox (reduction and oxidation) state of soils and sediments exists on a continuum from oxidized to reduced and can affect the mobility of uranium plumes. Under oxidized conditions, U is rather soluble as a uranyl ion in the U6+ valence state, whereas under reducing conditions U can become immobilized in the less-soluble U4+ valence state. Researchers at the University of Iowa and Argonne National Laboratory have found that a complex mixture of ferrous iron (Fe2+)-bearing minerals in a naturally reduced soil is capable of reducing and immobilizing uranium. Using Mössbauer spectroscopy at the University of Iowa and synchrotron x-ray absorption spectroscopy at the Advanced Photon Source at Argonne, the researchers found that uranium was reduced by Fe2+ in clay minerals and by a less-common, transient, and highly reactive Fe2+-mineral called green rust. The researchers also observed that the reduced U4+ atoms formed a product different from the uraninite mineral (UO2) commonly observed in laboratory studies, providing evidence for the diversity in chemical speciation of reduced U in natural systems. This study provides detailed information necessary for understanding toxic and radioactive contaminant mobility which will contribute to the long-term stewardship of U.S. Department of Energy legacy sites.

Reference: Latta, D. E., M. I. Boyanov, K. M. Kemner, E. J. O'Loughlin, and M. M. Scherer. 2012. "Abiotic Reduction of Uranium by Fe(II) in Soil," Applied Geochemistry 27, 1512–24. (Reference link)

Contact: Roland F. Hirsch, SC-23.2, (301) 903-9009
Topic Areas:

  • Research Area: Subsurface Biogeochemical Research
  • Research Area: Structural Biology, Biomolecular Characterization and Imaging
  • Research Area: Structural Biology Infrastructure

Division: SC-23.1 Climate and Environmental Sciences Division, BER

 

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