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Abstract: A procedure to determine lead and zinc by anodic stripping voltammetry and copper by cathodic stripping voltammetry in natural river samples was developed and validated. Cu determination involves the adsorption of Cu complexes with 8-hydroxyquinoline (oxine) onto a hanging mercury drop electrode. All samples were studied at natural pH and following optimal conditions were found: an accumulation step at −1.3V (all potential values in the paper are given versus the Ag/AgCl, [KCl]=3M reference electrode) during 30s for determination of Zn contents and at −0.7V during 60s for determination of Pb contents. Concerning Cu analysis, the optimal oxine concentration was found to be 10−5 M with a deposition potential of −1.1V during 30s followed by an adsorption step at −0.25V during 15s. This procedure was afterwards validated by using certified reference freshwater and performing an intercalibration exercise. Finally the method was successfully applied in the Deûle River, highly contaminated by dissolved Zn and to a lesser extent by Pb and Cu, due to past and present activities of metallurgical plants. Under these optimal conditions, metal concentrations measured by our voltammetric procedures in the Deûle River were found in the range 12.4–23.2nM for Zn, 1.7–3.2nM for Pb and 4.9–7.6nM for Cu. [Copyright &y& Elsevier]

Abstract: Sediments in the Deûle River (northern France) are severely polluted by metals in the vicinity of several metallurgical plants. The aim of this paper is to identify the role played by the recurrent resuspension of these polluted sediments by boat traffic on the dissolved Pb and Zn concentrations in the river. For that purpose, several high-frequency on-line monitoring campaigns were performed. Our results clearly suggest that the resuspension of sedimentary particles into the overlying water significantly increased the dissolved electrolabile Pb and Zn contents. This increase does not persist for a long time because at night and during weekends and holidays, when the boat traffic strongly slows down, Pb and Zn concentrations drop again quickly. Our data also indicate that the biological processes (such as photosynthetic and respiration activities), diffusive and benthic fluxes, as well as dilution of pore water into the overlying water during sediment remobilization do not contribute significantly to the sharp increase of dissolved Pb and Zn concentrations in the river during the day. The good correlation between turbidity and electrolabile metal concentration allows us to discard slow AVS (Acid Volatile Sulfides) oxidation as well. Desorption of metals from sediment particles was clearly the most relevant process, responsible for the increase of dissolved Pb and Zn concentrations in the water column. [Copyright &y& Elsevier]