Mechanisms of nanocrystalline uraninite oxidation by iron minerals under of sulfate-reducing bacteria
EMSL Project ID
30457
Abstract
Uranium (U) is the most common radionuclide in soils, sediments, and groundwater at many sites including U.S. DOE sites and is therefore of particular environmental concern. Subsurface bacteria such as sulfate-reducing bacteria (SRB) can reduce highly soluble U(VI) to less soluble U(IV) under anoxic conditions. Our results showed that cultures of Desulfovibrio desulfuricans G20 and Shewanella oneidensis MR-1 reduced U(VI) to nanometer-sized particles (3 - 5 nm) of uraninite (Sani et al. 2008, 2006, 2005, 2004; Beyenal et al., 2004). Our results also showed that under sulfate-reducing conditions, SRB-mediated uraninite nanocrystals (<5 nm diameter) can be reoxidized by Fe(III)-(hydr)oxides such as hematite, goethite, and ferrihydrite. These mechanisms of reoxidation of reduced U by Fe(III)-(hydr)oxides are still unknown and currently under investigation. We recently received funding from the U.S. DOE - Environmental Remediation Sciences Program to extend this research on the mechanisms of oxidation of uraninite nanocrystals.To understand these mechanisms, it is vital to elucidate electron transfer mechanisms and resulting mineral phases of reactions between uraninite and Fe-bearing mineral phases under sulfate-reducing conditions. Therefore we propose to use High-resolution transmission electron microscopy, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy to characterize U, Fe, and S mineral phases associated with oxidation of nanocrystalline uraninite under biotic and abiotic conditions. In addition, sub-samples will also be analyzed using Auger electron spectroscopy, X-ray diffraction, and Scanning confocal laser microscopy (available at the Montana State University and School of Mines and Technology). We will also write user proposal to perform Synchrotron X-ray absorption spectroscopy (XANES and EXAFS) for selected samples. Fe and U mineral phases identified before, during, and after oxidation of nanocrystalline uraninite by Fe(III)-(hydr)oxides using various analytical and spectroscopic techniques will reflect changes in redox-sensitive species necessary to define a unique biogeochemical model of interactions of Fe and U with SRB in natural subsurface environments.
This proposed research and combined with several lab experiments will support in elucidating a molecular and mechanistic understanding on the roles of Fe minerals in the reoxidation of microbially reduced U. Using well defined systems, and analytical and spectroscopic techniques, we will, for the first time, characterize secondary iron minerals and factors involved in electron-transfer between uraninite and iron minerals. This experimental data will be integrated with mathematical models developed to describe interactions among SRB, soil minerals, and U phases. The proposed research will significantly improve our overall understanding of fundamental geochemical and microbiological parameters that influence the reactivity of soil minerals toward reoxidation of nanocrystals of uraninite. The information gathered through this proposed research will results number of peer reviewed articles. In addition to the novel basic research described above, collaboration among scientists at the PNNL, LBNL, and three public universities in the three states is a key feature of this user proposal. In past, we have a good record of publishing peer-reviewed articles with PNNL scientists (Sani et al. 2008, 2006, 2005, 2004; Beyenal et al., 2004) and over fifteen conference abstracts; and plan to continue this.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2008-10-01
End Date
2011-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Rastogi G, S Osman, RK Kukkadapu, MH Engelhard, GL Vaishampayan, GL Anderson, and RK Sani. 2010. "Microbial and Mineralogical Characterizations of Soils Collected From the Deep Biosphere of the Former Homestake Gold Mine, South Dakota." Microbial Ecology. doi:10.1007/s00248-010-9657-y
Sengor SS, G Singh, A Dohnalkova, N Spycher, TR Ginn, B Peyton, and RK Sani. 2016. "Impact of different environmental conditions on the aggregation of biogenic U(IV) nanoparticles synthesized by Desulfovibrio alaskensis G20." Biometals 29(6):965-980. doi:10.1007/s10534-016-9969-6
Sivaswamy V, MI Boyanov, BM Peyton, S Viamajala, R Gerlach, W Apel, RK Sani, A Dohnalkova, KM Kemner, and T Borch. 2011. "Multiple Mechanisms of Uranium Immobilization by Cellulomonas sp. Strain ES6." Biotechnology and Bioengineering 108(2):264-276. doi:10.1002/bit.22956