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The influence of microbial redox cycling on radionuclide mobility in the subsurface at a low‐level radioactive waste storage site

The influence of microbial redox cycling on radionuclide mobility in the subsurface at a... ABSTRACT As anaerobic microbial metabolism can have a major impact on radionuclide speciation and mobility in the subsurface, the solubility of uranium, technetium and radium was determined in microcosms prepared from sediments adjacent to the Drigg low‐level radioactive waste storage site (UK). Both uranium (as U(VI); ) and Tc (as Tc(VII); ) were removed from groundwater concurrently with microbial Fe(III) reduction, presumably through reduction to insoluble U(IV) and Tc(IV), respectively, while Ra (Ra2+) that had rapidly sorbed onto mineral surfaces was not released following Fe(III) reduction. Biogenic Fe(II) minerals in reduced Drigg sediments were unable to reduce U(VI) abiotically but could reduce Tc(VII). Following addition of the oxidant nitrate to the reduced sediments, uranium was remobilized and released into solution, whereas technetium remained associated with an insoluble phase. A close relative of Pseudomonas stutzeri dominated the microbial communities under denitrifying conditions, reducing nitrate to nitrite in the microcosms, which was able to reoxidize Fe(II) and U(IV), with release of the latter into solution as U(VI). These data suggest that microbial Fe(III) reduction in the far‐field at Drigg has the potential to decrease the migration of some radionuclides in the subsurface, and the potential for reoxidation and remobilization by nitrate, a common contaminant in nuclear waste streams, is radionuclide‐specific. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Geobiology Wiley

The influence of microbial redox cycling on radionuclide mobility in the subsurface at a low‐level radioactive waste storage site

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References (42)

Publisher
Wiley
Copyright
Copyright © 2007 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1472-4677
eISSN
1472-4669
DOI
10.1111/j.1472-4669.2007.00101.x
Publisher site
See Article on Publisher Site

Abstract

ABSTRACT As anaerobic microbial metabolism can have a major impact on radionuclide speciation and mobility in the subsurface, the solubility of uranium, technetium and radium was determined in microcosms prepared from sediments adjacent to the Drigg low‐level radioactive waste storage site (UK). Both uranium (as U(VI); ) and Tc (as Tc(VII); ) were removed from groundwater concurrently with microbial Fe(III) reduction, presumably through reduction to insoluble U(IV) and Tc(IV), respectively, while Ra (Ra2+) that had rapidly sorbed onto mineral surfaces was not released following Fe(III) reduction. Biogenic Fe(II) minerals in reduced Drigg sediments were unable to reduce U(VI) abiotically but could reduce Tc(VII). Following addition of the oxidant nitrate to the reduced sediments, uranium was remobilized and released into solution, whereas technetium remained associated with an insoluble phase. A close relative of Pseudomonas stutzeri dominated the microbial communities under denitrifying conditions, reducing nitrate to nitrite in the microcosms, which was able to reoxidize Fe(II) and U(IV), with release of the latter into solution as U(VI). These data suggest that microbial Fe(III) reduction in the far‐field at Drigg has the potential to decrease the migration of some radionuclides in the subsurface, and the potential for reoxidation and remobilization by nitrate, a common contaminant in nuclear waste streams, is radionuclide‐specific.

Journal

Geobiology – Wiley

Published: Sep 1, 2007

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