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(M/EH013) Assessment of sediment ecotoxicity and genotoxicity prior to dredging operations on navigation channels in France. Clément, Bernard1, Devaux, Alain1, Perrodin, Yves1, Danjean, Marc1, Ghidini-Fatus, Martine1, 1 ABSTRACT- One possible fate of dredged sediments is disposal in a submerged gravel pit, but this practice may be a source of contamination of the aquatic environment. In an attempt to assess the risks for the aquatic ecosystem, we carried out a microcosm test in the laboratory on three sediments of channel sections to be dredged. The microcosms consisted of cylindrical beakers in which 300 g sediments and 2 liters of synthetic freshwater were introduced. After a short period of stabilization, pelagic organisms (microalgae, daphnids, duckweeds, pond snails) and benthic organisms (amphipods, chironomids) were introduced into microcosms. Survival and growth of organisms were monitored during 28 days. Genetic damage was measured weekly in pond snail hemocytes through the comet assay. The sediments, called B2, B13 and B22, contained high levels of metals, especially B13, but were moderately contaminated by PAHs and PCBs. Only slight effects on the biota were observed, except for genetic damage on pond snail hemocytes which was significant in all microcosms, and especially in B13. The absence of pronounced toxic effects on whole organisms is not surprising when comparing concentrations and threshold values of most toxicants of the sediments, except for Zn, Ni and Cu of B13 for which higher effects might have been expected. Speciation, influence of organic matter and presence of sulfides might explain these results. By contrast, assessment of DNA damage revealed to be more sensitive and provided a classification of sediments coherent with their toxic load. Key words: dredged sediment, microcosm, ecotoxicity, genotoxicity |
