Uranium(VI) complexation with pyoverdins secreted by a subsurface strain of Pseudomonas fluorescens and Complexation of curium(III) with pyoverdin model compounds – salicylhydroxamic (SHA) and benzohydroxamic acid (BHA)

The contributions of the Forschungszentrum Dresden-Rossendorf (FZD)/Institute of Radiochemistry (IRC) within the microbe project as part of the international co-operation of the Äspö HRL (Sweden) with the BMWi (Germany) are concentrated in a project addressing the indirect interaction mechanism of a mobilization of actinides by released bioligands in the aquifer system from relevant Äspö bacteria. The ongoing study is focused on: (i) isolation and characterization of microbial ligands produced from a subsurface strain of Pseudomonas fluorescens isolated at Äspö, (ii) interaction of U(VI), Np(V), and Cm(III) with the microbial ligands including compounds simulating the functionality of the microbial ligands and the surface of the bacteria and (iii) spectroscopic characterization of the formed actinide complexes/compounds. The formation constants determined will be used directly in speciation and transport models. This project should help to identify the dominating process of the interaction between actinides and microbes (direct or indirect ones). The research performed in our project improves the understanding of the behavior of colloids and microbes and their respective interaction with radionuclides.
The activities in 2007 were concentrated on (a) complexation studies of U(VI) with the secreted bioligand mixture of P. fluorescens found at Äspö HRL, (b) complexation studies of Cm(III) with relevant pyoverdin model compounds, and (c) complexation studies of U(VI) and Cm(III) with model molecules simulating the functionality of bacterial cell envelopes to explain the interactions of actinides in biologically systems on a molecular level. Selected results of the topics (a) and (b) will be reported here.