Development and application of a HPIC-ICP-MS method for the redox arsenic speciation in river sediment pore waters

A new sensitive chromatographic method has been developed for As speciation determination in anoxic pore waters. Starting from aliquots of 25 μL, the different As species As(III), As(V), MMAAV and DMAAV were separated in less than 4 min by HPIC-ICP-MS using the IonPac® AG7-AS7 anion-exchange column set and dilute HNO3 as mobile phase. The detection limits were below or equal to 0.25 μg L−1 for each As species, which makes the method efficient to determine As speciation in poorly-contaminated sediments. In addition, no precipitation of iron and manganese (hydr)-oxides was observed since the anoxic samples were systematically carefully manipulated under nitrogen atmosphere. Chlorides were eliminated by the chromatographic separation, thus making possible speciation analysis in estuarine or seawater samples. The use of internal standard was not necessary due to good signal stability (m/z 75 over 4 h of analysis. An environmental application has also been successfully performed in the Marque River (Northern France). Inorganic As species were detected in pore waters at low concentrations [below 1 and 10 μg L−1, for As(V) and As(III) respectively]. Others As species, identified as thioarsenic species, were also detected

Benthic exchanges of sedimentary metals (Cd, Cu, Fe, Mn, Ni, Pb and Zn) in Deûle River (Northern France)

International audienceExperiments were performed on the Deûle River (Northern France), which is strongly polluted by smelting plants, in the aim to investigate the influence of diagenetic processes and benthic macro-faunal activity on trace metal (Cd, Cu, Ni and Zn) and major metal (Fe, Mn) exchanges occurring at the water-sediment interface. Diffusive metal fluxes were determined from pore water metal concentration gradients measured in sediment cores. Benthic metal fluxes were evaluated using incubation chambers under dark conditions, and by further examining key variables (O2, CO2, redox potential and pH) affecting metal release and sequestration processes. As a whole, it was demonstrated that benthic fluxes were strongly dependent upon medium oxygenation and generation of colloidal iron oxides and hydroxides at the overlying water-sediment interface, raising the possibility of trace-metal adsorption and (co)precipitation

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

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