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(67-04) Ability of DGT measurements for estimating trace metals bioavailability: comparison with bioassays and free-ion modelling. Gilbin, Rodolphe*,1, Bakkaus, Estelle1, Tusseau-Vuillemin, Marie-Hélène1, Garric, Jeanne2, 1 Cemagref (Unité de Recherches QHAN). Parc de Tourvoie., Antony, France2 Cemagref (Laboratoire d'Ecotoxicologie). 3 bis, quai Chauveau., Lyon, France ABSTRACT- In the aquatic environment, trace metals are distributed between dissolved, colloidal and particulate compartments and associated with different ligands, whereas only the free and labile forms are usually regarded as bioavailable. Available analytical techniques generally require a delicate calibration that limit their use for field studies. In addition the presence of heterogeneous and weakly characterised natural organic matter is a limitation to the use of these methods as well as to chemical modelling. Recently, a new technique for the measurement of free and labile metals ("DGT": Diffusion Gradients in Thin Films) was developed. It allows to avoid some of the difficulties related to the traditional techniques. But in order to validate field measurements, it is essential to specify the representativity of the DGT measurements compared to bioavailable metal in water with various ligands. The aim of this study was to compare the experimental measurement by the DGT method with the measurement of biological effects by bioassays (acute toxicity) and the evaluation of free ion by chemical modelling (MINEQL+). Bioavailability of trace metals (Cu, Cd) in water was studied in the presence of characterised ligands (inorganic ligands, citrate, EDTA, standard humic substances). The results obtained should allow to specify the representativity of the DGT method compared to free ion concentrations and the bioavailability of trace metals in the presence of various ligands. They will provide a basis for the calibration of the DGT method to characterise trace metals distribution in water with non-characterised organic matter. Results will also be discussed in terms of potential uses of the DGT method for field studies in natural and polluted waters. Key words: trace metals , Diffusion Gradient in Thin Films , bioassays, Natural Organic Matter |
