The impact of the Äspö ground water bacterium Pseudomonas fluorescens on the speciation of plutonium

Bacteria are widely distributed in nature and they can strongly influence the behaviour of actinides in the environment. This presentation focuses on the unknown interaction between plutonium (Pu(VI) and Pu(IV)-polymers) and cells of the ground water bacterium Pseudomonas fluorescens isolated from the Äspö site, Sweden. Accumulation experiments were performed in order to obtain information about the amount of Pu bound by the cells in dependence on the contact time and the initial plutonium concentration. We used solvent extraction and UV-vis-NIR absorption spectroscopy to determine the speciation of Pu oxidation states. The Pu oxidation state distributions will be discussed in detail and a model which describes the ongoing processes in the system Pu–P. fluorescens will be presented.