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dc.contributor.authorCumberland, S.
dc.contributor.authorEtschmann, B.
dc.contributor.authorBrugger, J.
dc.contributor.authorDouglas, G.
dc.contributor.authorEvans, Katy
dc.contributor.authorFisher, L.
dc.contributor.authorKappen, P.
dc.contributor.authorMoreau, J.
dc.identifier.citationCumberland, S. and Etschmann, B. and Brugger, J. and Douglas, G. and Evans, K. and Fisher, L. and Kappen, P. et al. 2018. Characterization of uranium redox state in organic-rich Eocene sediments. Chemosphere. 194: pp. 602-613.

The presence of organic matter (OM) has a profound impact on uranium (U) redox cycling, either limiting or promoting the mobility of U via binding, reduction, or complexation. To understand the interactions between OM and U, we characterised U oxidation state and speciation in nine OM-rich sediment cores (18 samples), plus a lignite sample from the Mulga Rock polymetallic deposit in Western Australia. Uranium was unevenly dispersed within the analysed samples with 84% of the total U occurring in samples containing > 21 wt % OM. Analyses of U speciation, including x-ray absorption spectroscopy and bicarbonate extractions, revealed that U existed predominately (~71%) as U(VI), despite the low pH (4.5) and nominally reducing conditions within the sediments. Furthermore, low extractability by water, but high extractability by a bi-carbonate solution, indicated a strong association of U with particulate OM. The unexpectedly high proportion of U(VI) relative to U(IV) within the OM-rich sediments implies that OM itself does not readily reduce U, and the reduction of U is not a requirement for immobilizing uranium in OM-rich deposits. The fact that OM can play a significant role in limiting the mobility and reduction of U(VI) in sediments is important for both U-mining and remediation.

dc.titleCharacterization of uranium redox state in organic-rich Eocene sediments
dc.typeJournal Article
curtin.departmentSchool of Earth and Planetary Sciences (EPS)
curtin.accessStatusOpen access

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