BER launches Environmental System Science Program. Visit our new website under construction!

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

BER Research Highlights


Clay Minerals and Metal Oxides Can Change How Uranium Travels Through Sediments
Published: December 14, 2016
Posted: April 21, 2017

Redox transformations that affect the environmental mobility of metal or radionuclide contaminants typically occur in the presence of mineral or biological surfaces. [Image courtesy of Argonne National Laboratory]

The molecular form of reduced uranium in the subsurface is affected by common sediment constituents.

The Science
Clay minerals are ubiquitous native components of sediments and soils, as well as a material used in the engineered barriers of spent nuclear fuel storage facilities. A recent study examined the molecular form of uranium (IV) in the presence of montmorillonite clays and found that they can inhibit the predicted precipitation of the mineral uraninite.

The Impact
The effect of environmental surfaces on the form of reduced uranium is currently not accounted for in computational models. This study used state-of-the-art spectroscopy techniques to provide the molecular-level information needed for accurate prediction of uranium transport in subsurface environments.

Summary
The mobility of uranium in the subsurface depends strongly on its oxidation state, with U(IV) being significantly less soluble than U(VI). However, solubility also depends on the molecular form of the contaminant, which can be affected by adsorption to the surface of minerals, bacterial membranes and other constituents in the surrounding environment. A team of scientists led by Argonne National Laboratory examined the ability of montmorillonite clay minerals to adsorb U(IV) resulting from the reduction of U(VI), and compared it to that of iron and titanium oxide surfaces. The valence and molecular structure of uranium was tracked by synchrotron X-ray absorption spectroscopy. The team found that at low clay surface:U ratios the reduction of U(VI) in the presence of SYn-1 montmorillonite leads to the formation of the mineral uraninite (UO2). However, at high clay surface:U ratios (more typical of environmental conditions) a significant fraction of the resulting U(IV) is present as adsorbed U(IV) ions (up to 50% of total U). The threshold U(IV) surface coverage above which uraninite formation begins was determined to be significantly lower for montmorillonite than for iron or titanium oxides, suggesting that metal oxides may play a more important role than clay minerals in stabilizing the nonuraninite species observed in natural sediments.

Contacts
BER Program Manager
Amy Swain
Program Officer, U.S. DOE Office of Science
amy.swain@science.doe.gov; (301) 903-1828

Principal Investigator
Kenneth M. Kemner
Argonne National Laboratory
kemner@anl.gov/ (630) 252-1163

Funding
This research is part of the Subsurface Science Scientific Focus Area at Argonne National Laboratory (ANL), which is supported by the Subsurface Biogeochemical Research Program of the Office of Biological and Environmental Research, within the U.S. Department of Energy DOE) Office of Science. Use of the Electron Microscopy Center and the Advanced Photon Source at ANL is supported by the Office of Basic Energy Sciences within the DOE Office of Science. MRCAT/EnviroCAT operations are supported by DOE and the MRCAT/EnviroCAT member institutions. All work at ANL was under Contract DE-AC02-06CH11357.

Publications
Boyanov, M. I., D. E. Latta, M. M. Scherer, E. J. O’Loughlin, and K. M. Kemner. “Surface area effects on the reduction of UVI in the presence of synthetic montmorillonite.” Chemical Geology 464, 110–17 (2017). [DOI:10.1016/j.chemgeo.2016.12.016].

Related Links
Subsurface Science Scientific Focus Area at Argonne National Laboratory

Topic Areas:

  • Research Area: Subsurface Biogeochemical Research
  • Research Area: Microbes and Communities
  • Research Area: Research Technologies and Methodologies

Division: SC-33.1 Earth and Environmental Sciences Division, BER

 

BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER

Recent Highlights

Mar 23, 2021
Molecular Connections from Plants to Fungi to Ants
Lipids transfer energy and serve as an inter-kingdom communication tool in leaf-cutter ants&rsqu [more...]

Mar 19, 2021
Microbes Use Ancient Metabolism to Cycle Phosphorus
Microbial cycling of phosphorus through reduction-oxidation reactions is older and more widespre [more...]

Feb 22, 2021
Warming Soil Means Stronger Microbe Networks
Soil warming leads to more complex, larger, and more connected networks of microbes in those soi [more...]

Jan 27, 2021
Labeling the Thale Cress Metabolites
New data pipeline identifies metabolites following heavy isotope labeling.

Analysis [more...]

Aug 31, 2020
Novel Bacterial Clade Reveals Origin of Form I Rubisco
Objectives

  • All plant biomass is sourced from the carbon-fixing enzyme Rub [more...]

List all highlights (possible long download time)