Interaction of Desulfovibrio äspöensis with plutonium


Interaction of Desulfovibrio äspöensis with plutonium

Moll, H.; Merroun, M.; Hennig, C.; Rossberg, A.; Den Auwer, C.; Selenska-Pobell, S.; Bernhard, G.

Microbes are widely distributed in nature and they can strongly influence the migration of actinides in the environment. Microorganisms in concentrations of 1x103 to 5x106 cells ml-1 were estimated by Pedersen et al. in the aquifer system of the Äspö Hard Rock Laboratory (Äspö HRL) in Sweden. The number of sulfate-reducing bacteria (SRB) was between 101 to 2x104 cells ml-1. We investigated the interaction of the SRB Desulfovibrio äspöensis, DSM 10631T, with plutonium. The 242Pu was provided as a mixture of ca. 46% Pu(VI) and ca. 34% Pu(IV)-polymer. Interactions between bacteria and plutonium in mixed oxidation states were not yet intensively investigated.
In this study, accumulation experiments were performed in order to obtain information about the amount of the Pu bound by bacteria in dependence on the contact time and the [Pu]initial at pH 5. We used liquid-liquid-extractions and absorption spectroscopy to determine the Pu speciation. In agreement with the results obtained with U(VI) [2] and Np(V), we found a strong dependence of the amount of accumulated Pu with [Pu]initial. Based on our results and taking into consideration the findings of Panak et al. [3], we developed a model describing the interaction of Pu(VI) and Pu(IV)-polymers with D. äspöensis. In a first step, the Pu(VI) and Pu(IV)-polymers are bound to the biomass. The Pu(VI) is reduced to Pu(V) due to the activity of the cells within the first 24 h of contact time. Most of the formed Pu(V) dissolves due to the weak complexing properties. The dissolved Pu(V) disproportionates to Pu(IV) and Pu(VI) which are then interacting with functional groups of the cell surface structure. Indications were found also for a penetration of Pu species inside the bacterial cells.

[1] Pedersen, K.: Microbial processes in radioactive waste disposal. SKB Technical Report TR-00-04 (2000).
[2] Moll, H.; Merroun, M.; Stumpf, Th.; Geipel, G.; Selenska-Pobell, S.; Hennig, C.; Roßberg, A.; Bernhard, G.: Interaction of Desulfovibrio äspöensis with Actinides, presented at the MIGRATION’03, Gyeongju, Korea (2003).
[3] Panak, P. J.; Nitsche, H.: Radiochim. Acta 89, 499 (2001).

This work was funded by the BMWi under contract number: 02E9491.

Keywords: Plutonium; Bacteria; Desulfovibrio äspöensis

  • Lecture (Conference)
    Migration 2005, 10th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 18.-23.09.2005, Avignon, France
  • Contribution to proceedings
    Migration 2005, 10th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 18.-23.09.2005, Avignon, France

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