Geomicrobiological redox cycling of the transuranic element neptunium.
Microbial processes can affect the environmental behavior of redox sensitive radionuclides, and understanding these reactions is essential for the safe management of radioactive wastes. Neptunium, an alpha-emitting transuranic element, is of particular importance because of its long half-life, high radiotoxicity, and relatively high solubility as Np(V)O(2)(+) under oxic conditions. Here, we describe experiments to explore the biogeochemistry of Np where Np(V) was added to oxic sediment microcosms with indigenous microorganisms and anaerobically incubated. Enhanced Np removal to sediments occurred during microbially mediated metal reduction, and X-ray absorption spectroscopy showed this was due to reduction to poorly soluble Np(IV) on solids. In subsequent reoxidation experiments, sediment-associated Np(IV) was somewhat resistant to oxidative remobilization. These results demonstrate the influence of microbial processes on Np solubility and highlight the critical importance of radionuclide biogeochemistry in nuclear legacy management.
Research Centre for Radwaste and Decommissioning, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK.
Gareth T W
GT
Law
Andrea
A
Geissler
Jonathan R
JR
Lloyd
Francis R
FR
Livens
Christopher
C
Boothman
James D C
JD
Begg
Melissa A
MA
Denecke
Jörg
J
Rothe
Kathy
K
Dardenne
Ian T
IT
Burke
John M
JM
Charnock
Katherine
K
Morris
D001673:Biodegradation, Environmental; D001711:Biotransformation; D055598:Chemical Phenomena; D055669:Ecological and Environmental Phenomena; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology; D008827:Microbiological Phenomena; D009405:Neptunium / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D011848:Radioactive Pollutants / Q000737:chemistry / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy
D011848:Radioactive Pollutants; D009405:Neptunium