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

BER Research Highlights


Calcium and Phosphate Can Affect How Uranium Contamination Travels Through the Environment
Published: November 17, 2015
Posted: April 27, 2016

The molecular form and the oxidation of subsurface uranium are affected by common groundwater constituents.

The Science  
Calcium and phosphate are environmental components found in animal bone, various minerals, and groundwater. A recent study has demonstrated that these ions slow down the oxidation of subsurface-relevant uranium species and change the oxidized form of uranium into a more stable mineral.

The Impact
The effect of environmental factors like calcium and phosphate on transformations of some newly discovered forms of uranium found in groundwater are currently unknown. This study determined uranium valence and molecular structure using state-of-the-art spectroscopy techniques to provide information necessary for accurately predicting uranium transport.

Summary
The mobility of uranium in subsurface environments depends strongly on its oxidation state, with chemically reduced UIV phases being significantly less soluble than UIV minerals. A team of scientists from Argonne National Laboratory, Illinois Institute of Technology, and Bulgarian Academy of Sciences compared the oxidation kinetics and mechanisms of two potential products of UIV reduction in natural systems: a nanoparticulate UO2 phase and an amorphous UIV-Ca-PO4 phase. The valence and molecular structure of uranium was tracked by synchrotron x-ray absorption spectroscopy. Similar oxidation rates for the two phases were observed in solutions equilibrated with atmospheric O2 and CO2. Addition of up to 400 µM Ca and PO4 decreased the oxidation rate by an order of magnitude for both UO2 and UIV-phosphate. In the absence of Ca or PO4, the product of UO2 oxidation was Na-uranyl oxyhydroxide, whereas the product of UIV-Ca-PO4 oxidation was a UIV-phosphate phase (autunite). In the presence of Ca or PO4, the oxidation proceeded to UIV-phosphate for both pre-oxidation forms of UIV. Addition of Ca or PO4 changed the mechanism of oxidation by causing the formation of a passivation layer on the particle surfaces.

Contacts (BER PM)
Roland F. Hirsch, roland.hirsch@science.doe.gov, 301-903-9009

(PI Contact)
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 U.S. Department of Energy’s (DOE) Subsurface Biogeochemical Research Program, Office of Biological and Environmental Research, Office of Science. Use of the Electron Microscopy Center and Advanced Photon Source at ANL is supported by DOE’s Office of Science, Office of Basic Energy Sciences. MRCAT/EnviroCAT operations are supported by DOE and the MRCAT/EnviroCAT member institutions. All work at ANL was under Contract DE-AC02-06CH11357.

Publications
Latta, D. E., K. M. Kemner, B. Mishra, and M. I. Boyanov. 2016. “Effects of Calcium and Phosphate on Uranium(IV) Oxidation: Comparison Between Nanoparticulate Uraninite and Amorphous UIV–Phosphate,” Geochimica et Cosmochimica Acta 174, 122–42. DOI: 10.1016/j.gca.2015.11.010. (Reference link)  

Related Links
Subsurface Science Scientific Focus Area at Argonne National Laboratory.

Topic Areas:

  • Research Area: Subsurface Biogeochemical Research
  • Research Area: Structural Biology Infrastructure
  • Research Area: Research Technologies and Methodologies

Division: SC-23.1 Climate 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

May 10, 2019
Quantifying Decision Uncertainty in Water Management via a Coupled Agent-Based Model
Considering risk perception can improve the representation of human decision-making processes in age [more...]

May 09, 2019
Projecting Global Urban Area Growth Through 2100 Based on Historical Time Series Data and Future Scenarios
Study provides country-specific urban area growth models and the first dataset on country-level urba [more...]

May 05, 2019
Calibrating Building Energy Demand Models to Refine Long-Term Energy Planning
A new, flexible calibration approach improved model accuracy in capturing year-to-year changes in bu [more...]

May 03, 2019
Calibration and Uncertainty Analysis of Demeter for Better Downscaling of Global Land Use and Land Cover Projections
Researchers improved the Demeter model’s performance by calibrating key parameters and establi [more...]

Apr 22, 2019
Representation of U.S. Warm Temperature Extremes in Global Climate Model Ensembles
Representation of warm temperature events varies considerably among global climate models, which has [more...]

List all highlights (possible long download time)