Abstract
ABSTRACTMicrobially mediated reduction of Fe(III) in chlorite and biotite by Shewanella oneidensis MR-1 leads to a significant reduction in sorption of both Cs and Sr compared to the abiotic systems. As seen in previous studies, biotite is a more efficient sorbent than chlorite. Reduction of the mineral-associated Fe(III) causes increased dissolution of both minerals and reduces the sites available for Cs and Sr sorption. As this dissolution progresses it causes desorption of Cs and Sr from chlorite, but not biotite. Subsequent exposure to air increases sorption due to precipitation of secondary Fe(III) oxyhydroxide minerals derived from the Fe(II) released by bio-reduction. In contrast to successful bioremediation of redox active elements, this study suggests that microbial Fe(III) reduction could enhance the migration of Cs and Sr through phyllosilicate-dominated strata.
Highlights
IntroductionThe radioactive isotopes of caesium and strontium (caesium137 and strontium-90) are high-yield fission products that accumulate in nuclear fuel rods
The radioactive isotopes of caesium and strontium are high-yield fission products that accumulate in nuclear fuel rods
Mediated reduction of Fe(III) in chlorite and biotite by Shewanella oneidensis MR-1 leads to a significant reduction in sorption of both Cs and Sr compared to the abiotic systems
Summary
The radioactive isotopes of caesium and strontium (caesium137 and strontium-90) are high-yield fission products that accumulate in nuclear fuel rods They are a major component of the radioactivity in spent fuel and in waste from spent fuel storage ponds and fuel reprocessing plants, such as at Sellafield, UK (Thorpe et al 2012), and the Hanford Site, USA (McKinley et al 2007; Zachara et al 2002). Radioactive Cs and Sr will be present in high level nuclear wastes (HLW) intended for interim storage and geological disposal and their behavior in both near surface and natural environments needs to be understood to safely manage HLW In all these environments, nitrate (NO3¡) will be present as either a co-contaminant from the wastes or as a pre-existing component (e.g., derived from agricultural use)
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