LAUSR

ABSTRACT With data from in vitro and in situ investigations, we developed a mathematical model to describe cellular uptake of uranium and arsenic in solution by living Lemna gibba under homeostatic regulation. The model considers the ability of healthy cells to resist accumulation of toxic metal species by regulating physicochemical properties of the cell membrane. In the bulk solution, the ratio of the total amounts of bioavailable metal ions to the metal ions uptake by the cells is very high. Consequently, the main rate-limiting processes of uptake are the biosorption kinetics on both external and internal surfaces at the biological interface, and the transport of the metal ions across the cell membrane. The model prediction correlates well with uptake results from field and microcosm experiments for uranium and arsenic by L. gibba, a model ecotoxicological test organism.