title: Kinetic analysis of uranium accumulation in the bivalve Corbicula fluminea: effect of pH and direct exposure levels.
abstract: The bioaccumulation of natural uranium in the freshwater bivalve Corbicula fluminea was investigated subsequent to the bivalve's experimental waterborne exposures. A first experiment determined the accumulation rate (transfer efficiency, tissular distribution) and subcellular distribution of uranium in organs after over 42 days of uranium exposure (100 microg l(-1); pH 7) and later following 60 days of depuration. Results showed that there was direct transfer of uranium to the bivalve organs ([U]organism/[U]water = 0.16, fresh weight, fw). The highest accumulation levels occurred in the visceral mass and remained constant throughout the exposure duration, although a linear increase in the U concentration in the gills was observed (2.98 +/- 1.3-10.9 +/- 3.7 microg g(-1) between days 2 and 42). A second set of experiments were performed in order to test the influence of the exposure levels (100; 500; 1500 microg l(-1)) and pH (7 and 8.1) on the bioaccumulation capacities. A marked difference of U distribution is observed as a function of exposure levels (gills were favoured in the case of high exposure levels-relative burden: 49.1 +/- 3% (1500 microg l(-1)), whereas the visceral mass presented higher accumulation levels at environmentally relevant U concentrations). Uranium concentration in the insoluble fraction (80%) in the whole body does not depend upon exposure levels in the water column or upon duration. These experiments did not allow any link to be established between the free-metal ion concentration and the bioaccumulation efficiency. Results showed a significant pH effect and indicated a link between the exposure conditions and the distribution of uranium in the bivalve organs.
authors.affiliation: Laboratoire de Radioécologie et Ecotoxicologie, Institut de Radioprotection et de Sûreté Nucléaire, Cadarache, Bat. 186 BP3, 13115 Saint Paul-Lez-Durance Cedex, France. olivier.simon@irsn.fr
authors.forename: Olivier
authors.initials: O
authors.lastname: Simon
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Garnier-Laplace
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D005602:France; D005618:Fresh Water / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D013997:Time Factors; D014018:Tissue Distribution; D014501:Uranium / Q000493:pharmacokinetics*
chemical_list: D014501:Uranium