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Instruments / Technical Area	Publication Details	Published	Actions
B18-Core EXAFS I18-Microfocus Spectroscopy	Organic complexation of U(VI) in reducing soils at a natural analogue site: Implications for uranium transport Adam J. Fuller , Peter Leary , Neil D. Gray , Helena S. Davies , J. Frederick W. Mosselmans , Filipa Cox , Clare H. Robinson , Jon K. Pittman , Clare M. Mccann , Michael Muir , Margaret C. Graham , Satoshi Utsunomiya , William R. Bower , Katherine Morris , Samuel Shaw , Pieter Bots , Francis R. Livens , Gareth T. W. Law Chemosphere DOI: 10.1016/j.chemosphere.2020.126859 Diamond Proposal Number(s): [10163, 12767, 12477] Open Access Show Abstract ▼ 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.	Apr 2020

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B18-Core EXAFS
I18-Microfocus Spectroscopy

Organic complexation of U(VI) in reducing soils at a natural analogue site: Implications for uranium transport