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(70-39) Links between uranium aqueous speciation and uptake by an alga : Influence of inorganic ligands. Fortin, Claude*,1, Garnier-Laplace, Jacqueline1, 1 Laboratoire de radioécologie expérimentale, St-Paul-Lez-Durance, France ABSTRACT- The bioavailability and toxicity of dissolved metals are closely linked to the metals' chemical speciation in solution. Normally the complexation of a metal by a ligand would be expected to decrease its bioavailability. The aqueous speciation of uranium undergoes tremendous changes within a pH range of 4 to 8 and in the presence of ligands commonly found in natural waters (carbonate, phosphate, hydroxide and natural organic matter). In the present project, we intend to establish links between speciation, medium composition and bioavailability of uranium toward the unicellular green alga, Chlamydomonas reinhardtii. Short-term metal uptake rates at low uranium concentrations (0.02 − 2 Key words: uranium, bioavailability, uptake, speciation |
M) are determined in simple inorganic media with particular emphasis on the differentiation between adsorbed and intracellular metal. The Free-Ion Model (FIM) is tested to determine if U uptake is governed by the free uranyl species (UO22+) or if other species can be assimilated (i.e. passive or facilitated transport of intact metal complexes across the plasma membrane). Results of our experiments indicate that at environmentally relevant concentrations of phosphate (< 50