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Title: Influence of microorganisms on the oxidation state distribution of multivalent actinides under anoxic conditions

The fate and potential mobility of multivalent actinides in the subsurface is receiving increased attention as the DOE looks to cleanup the many legacy nuclear waste sites and associated subsurface contamination. Plutonium, uranium and neptunium are the near-surface multivalent contaminants of concern and are also key contaminants for the deep geologic disposal of nuclear waste. Their mobility is highly dependent on their redox distribution at their contamination source as well as along their potential migration pathways. This redox distribution is often controlled, especially in the near-surface where organic/inorganic contaminants often coexist, by the direct and indirect effects of microbial activity. Under anoxic conditions, indirect and direct bioreduction mechanisms exist that promote the prevalence of lower-valent species for multivalent actinides. Oxidation-state-specific biosorption is also an important consideration for long-term migration and can influence oxidation state distribution. Results of ongoing studies to explore and establish the oxidation-state specific interactions of soil bacteria (metal reducers and sulfate reducers) as well as halo-tolerant bacteria and Archaea for uranium, neptunium and plutonium will be presented. Enzymatic reduction is a key process in the bioreduction of plutonium and uranium, but co-enzymatic processes predominate in neptunium systems. Strong sorptive interactions can occur for most actinide oxidation statesmore » but are likely a factor in the stabilization of lower-valent species when more than one oxidation state can persist under anaerobic microbiologically-active conditions. These results for microbiologically active systems are interpreted in the context of their overall importance in defining the potential migration of multivalent actinides in the subsurface.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Los Alamos National Laboratory
Publication Date:
OSTI Identifier:
1044147
Report Number(s):
LA-UR-10-08243; LA-UR-10-8243
TRN: US1203344
DOE Contract Number:
AC52-06NA25396
Resource Type:
Conference
Resource Relation:
Conference: Pacifichem 2010 ; December 15, 2010 ; Honolulu, Hi
Research Org:
Los Alamos National Laboratory (LANL)
Sponsoring Org:
DOE
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 59 BASIC BIOLOGICAL SCIENCES; ACTINIDES; BACTERIA; CONTAMINATION; DISTRIBUTION; MICROORGANISMS; NEPTUNIUM; PLUTONIUM; RADIOACTIVE WASTES; SOILS; STABILIZATION; SULFATES; URANIUM; VALENCE