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Abstract
Understanding the long-term fate, stability, and bioavailability of uranium (U) in the environment is important for the management of nuclear legacy sites and radioactive wastes. Analysis of U behavior at natural analogue sites permits evaluation of U biogeochemistry under conditions more representative of long-term equilibrium. Here, we have used bulk geochemical and microbial community analysis of soils, coupled with X-ray absorption spectroscopy and µ-focus X-ray fluorescence mapping, to gain a mechanistic understanding of the fate of U transported into an organic-rich soil from a pitchblende vein at the UK Needle’s Eye Natural Analogue site. U is highly enriched in the Needle’s Eye soils (~1600 mg kg-1). We show that this enrichment is largely controlled by U(VI) complexation with soil organic matter and not U(VI) bioreduction. Instead, organic-associated U(VI) seems to remain stable under microbially-mediated Fe(III)-reducing conditions. U(IV) (as non-crystalline U(IV)) was only observed at greater depths at the site (>25 cm); the soil here was comparatively mineral-rich, organic-poor, and sulfate-reducing / methanogenic. Furthermore, nanocrystalline UO2, an alternative product of U(VI) reduction in soils, was not observed at the site, and U did not appear to be associated with Fe-bearing minerals. Organic-rich soils appear to have the potential to impede U groundwater transport, irrespective of ambient redox conditions.
Original language | English |
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Article number | 126859 |
Number of pages | 33 |
Journal | Chemosphere |
Volume | 254 |
Early online date | 28 Apr 2020 |
DOIs | |
Publication status | Published - 30 Sept 2020 |
Keywords
- uranium
- radionuclide
- biogeochemistry
- natural analogue
- Needle's Eye
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Dive into the research topics of 'Organic complexation of U(VI) in reducing soils at a natural analogue site: implications for uranium transport'. Together they form a unique fingerprint.Projects
- 1 Finished
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Formation and stability of U(V) during biological and abiotic reduction of uranium
Bots, P. (Principal Investigator), Shaw, S. (Co-investigator), Denecke, M. A. (Co-investigator), Law, G. (Co-investigator) & Morris, K. (Co-investigator)
20/04/16 → 25/04/16
Project: Research