The behaviour of technetium during microbial reduction in amended soils from Dounreay, UK.
Radioactive technetium-99 forms during nuclear fission and has been found as a contaminant at sites where nuclear wastes have been processed or stored. Here we describe results from microcosm experiments containing soil samples representative of the UKAEA site at Dounreay to examine the effect of varying solution chemistry on the fate of technetium during microbial reduction. Analysis of a suite of stable element redox indicators demonstrated that microbial activity occurred in a range of microcosm experiments including unamended Dounreay sediments, carbonate buffered sediments, and microcosms amended with ethylenediaminetetraacetic acid (EDTA) a complexing ligand used in nuclear fuel cycle operations. During the development of anoxia mediated by indigenous microbial populations, TcO4- was removed from solution in experiments. In all cases, the removal of TcO4- from solution occurred during active microbial Fe(III)-reduction when Fe(II) was growing into the microcosms. Tc removal was most likely via reduction of TcO4- to poorly soluble Tc(IV) which is retained on the sediments. The potential stability of Tc associated with the soil to remobilisation via complexation with EDTA was examined as reduced Tc-labelled sediments were contacted with a de-oxygenated EDTA solution. No remobilisation of Tc(IV) in the presence of EDTA was observed.
Begg
James D C
JD
Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.
Burke
Ian T
IT
Morris
Katherine
K
D001639:Bicarbonates / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry; D004492:Edetic Acid / Q000737:chemistry; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D012990:Soil Pollutants, Radioactive / Q000737:chemistry* / Q000378:metabolism*; D013667:Technetium / Q000737:chemistry* / Q000378:metabolism*; D006113:United Kingdom
D001639:Bicarbonates; D002614:Chelating Agents; D012990:Soil Pollutants, Radioactive; D013667:Technetium; D004492:Edetic Acid