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Impacts of Repeated Redox Cycling on Technetium Mobility in the Environment

DOI: 10.1021/acs.est.7b02426 DOI Help

Authors: Nicholas Karl Masters-waage (The University of Manchester) , Katherine Morris (The University of Manchester) , Jonathan R. Lloyd (The University of Manchester) , Samuel Shaw (The University of Manchester) , J. Frederick W. Mosselmans (Diamond Light Source) , Christopher Boothman (The University of Manchester) , Pieter Bots (The University of Manchester) , Athanasios Rizoulis (The University of Manchester) , Francis R. Livens (The University of Manchester) , Gareth Law (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology

State: Published (Approved)
Published: November 2017
Diamond Proposal Number(s): 7593 , 10163 , 12767

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.

Subject Areas: Chemistry, Energy


Instruments: B18-Core EXAFS