Understanding How Environmental Microbes Make Uranium Less Soluble

The Science

Uranium is one of the major contaminants at DOE cleanup sites. It was usually released into the environment as the highly soluble uranyl ion (uranium (VI)). This ion interacts with bacteria and minerals in the ground to form reduced uranium (IV), notably in the mineral uraninite, a form that is much less soluble than uranium (VI). Less soluble uranium (IV) species are less likely to be moved out of the initially contaminated zone and into nearby rivers or aquifers by groundwater. New research has shown that biologically produced uraninite in a natural underground environment dissolves much more slowly than uraninite prepared in the laboratory. Researchers have developed a model showing that the slower dissolution is due to the presence of biomass that limits the reoxidation rate of the uranium (IV) in uraninite and diffusion of oxidized uranium into the groundwater. This understanding will be used in developing improved models of uranium transport in contaminated environments. Field studies were carried out at the Old Rifle, Colorado, Integrated Field Research Challenge site, while experiments to determine the forms of uranium present were conducted at the Stanford Synchrotron Radiation Lightsource.

The Impact

The legacy of uranium (U) ore extraction and processing has left many sites with U-contaminated groundwater, even after extensive tailings removal and remediation projects. Reductive bioremedation is currently being explored as a possible strategy for sites with excess groundwater uranium concentrations. These results indicate that the prolonged stability of U(IV) species in aquifers is strongly influenced by permeability, the presence of bacterial cells and cell exudates, and groundwater geochemistry.

BER Program Manager

Amy Swain

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]


Campbell, K. M., H. Veeramani, K.-U. Ulrich, L. Y. Blue, D. E. Giammar, R. Bernier-Latmani, J. E. Stubbs, E. Suvorova, S. Yabusaki, J. S. Lezama-Pacheco, A. Mehta, P. E. Long, and J. R. Bargar. 2011. “Oxidative Dissolution of Biogenic Uraninite in Groundwater at Old Rifle, CO,” Environmental Science and Technology 45, 8748–54. DOI:10.1021/es200482f.