|
(70-13) Quantification of the physicochemical and physiological factors involved in uranium uptake by freshwater bivalves. Denison, Frank*,1, Adam, Christelle1, Garnier-Laplace, Jacqueline1, 1 Laboratory of Experimental Radioecology, St-Paul-lez-Durance Cedex, France ABSTRACT- The bioavailability of uranium to a number of different organisms has been shown to be strongly influenced by the physicochemical conditions of the exposure medium. In the context of the development of a uranium transfer model for freshwater bivalves, a series of experiments have been performed to identify the most important uranium solution species responsible for uranium uptake by a model bivalve species (Corbicula fluminea). The exposure experiments were performed in regulated and well-characterised synthetic solutions, the compositions of which were varied in a systematic manner to investigate the influence of the main physicochemical parameters. The importance of the rate of water processing by the organisms, especially for short duration exposures, resulting in a high inter-individual variability of uranium uptake has been demonstrated. A novel non-invasive technique to permit quantification of the relative time-integrated rates of water processing at an individual level has been developed and applied as a means to normalize the kinetic data. The uptake kinetics of uranium have been measured for relatively short duration exposures (< 24h), permitting the precise regulation of the differing exposure conditions. The uptake has been interpreted in terms of the modelled solution speciation of uranium using the JChess computer program in conjunction with the OECD/NEA Thermochemical Data Base. This approach enables the development of a mechanistically based transfer model, avoiding some of the problems inherent in the more commonly applied approach of using empirical relationships between bioavailability and physicochemical parameters. Key words: uranium, bioavailability, speciation, bivalve |
