Impacts of repeated redox cycling on technetium mobility in the environment

Nicholas K. Masters-Waage, Katherine Morris, Jonathan R. Lloyd, Samuel Shaw, J. Frederick Willem Mosselmans, Christopher Boothman, Pieter Bots, Athanasios Rizoulis, Francis R. Livens, Gareth T.W. Law

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Abstract

Technetium is a problematic contaminant at nuclear sites and little is known about how repeated microbiologically-mediated redox cycling impacts its fate in the environment. We explore this question in sediments representative of the Sellafield Ltd. site, UK, over multiple reduction and oxidation cycles spanning ~ 1.5 years. We found the amount of Tc remobilised from the sediment into solution significantly decreased after repeated redox cycles. X-ray Absorption Spectroscopy (XAS) confirmed that sediment bound Tc was present as hydrous TcO2-like chains throughout experimentation and that Tc’s increased resistance to remobilisation (via reoxidation to soluble TcO4-) resulted from both shortening of TcO2 chains during redox cycling and association of Tc(IV) with Fe phases in the sediment. We also observed that Tc(IV) remaining in solution during bioreduction was likely associated with colloidal magnetite nanoparticles. These findings highlight crucial links between Tc and Fe biogeochemical cycles that have significant implications for Tc's long-term environmental mobility, especially under ephemeral redox conditions.
Original languageEnglish
Pages (from-to)14301–14310
Number of pages10
JournalEnvironmental Science and Technology
Volume51
Issue number24
Early online date16 Nov 2017
DOIs
Publication statusPublished - 16 Nov 2017

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Keywords

  • technetium
  • sediment
  • x-ray absorption spectroscopy

Cite this

Masters-Waage, N. K., Morris, K., Lloyd, J. R., Shaw, S., Mosselmans, J. F. W., Boothman, C., ... Law, G. T. W. (2017). Impacts of repeated redox cycling on technetium mobility in the environment. Environmental Science and Technology, 51(24), 14301–14310. https://doi.org/10.1021/acs.est.7b02426