Bioavailability of copper in contaminated sediments assessed by a DGT approach and the uptake of copper by the aquatic plant Myriophyllum aquaticum

International audienceThe assessment of the potentially harmful effects of metals on biota depends on the speciation and bioavailability of the metals. In this study, we investigated copper accumulation and toxicity in the aquatic plant Myriophyllum aquaticum after exposure to artificial sediments varying in peat and/or ferric hydroxide content and spiked with Cu (5 to 200 mg.kg-1). Modeling of the kinetic DGT (diffusive gradient in thin film) measurements revealed fast and slow copper resupply from the solid phase for sediment formulated with and without peat, respectively. M. aquaticum proved to be sensitive to copper, as the copper accumulation and growth differed depending on the sediment composition and copper concentration. Comparing the copper accumulation in M. aquaticum to total dissolved, free and CDGT (concentration in solution derived from DGT measurements) copper concentrations revealed that CDGT concentrations were a better predictor of the accumulation than the others. However, the relatively weak correlation observed (r2=0.6) and the fact that plant uptake does not increase proportionally to fluxes to DGT suggest that copper uptake in plants was not diffusion limited. Thus, the free copper concentrations near the root surface were sufficient to meet the plant's demand during the experiment. Furthermore, labile complexes that continuously resupply the Cu2+ pool may also contribute to the Environmental Toxicology and Chemistr