No abstract

No abstract

The aim of this paper was to evaluate the potential sediment cumulative damage and toxicity due to metal contamination in a polluted zone of Deûle river (in northern France) from nearby two smelters. Metal-enrichment factors and geoaccumulation indices measured with sediment depth revealed that--compared to background levels either in local reference soils or in world rivers sediments/suspended particulate matter--Cd contributed to the highest pollution levels, followed by Zn, Pb and to a much lesser extent Cu and Ni. A comparison of the vertical distribution of AVS (acid volatile sulfides), SEM (simultaneously extracted metals), TMC (total metal concentrations), TOC (total organic carbon) and interstitial water-metal concentrations in the sediment allowed us to highlight the extent of toxicity caused by Cd, Pb, Zn, Ni and Cu and to raise the possibility of their association with certain geochemical phases. To assess the actual environmental impacts of these metals in Deûle river, numerical sediment quality guidelines were further used in the present work. Sedimentary Pb, Zn, and Cd contents largely exceeded PEC (probable effect concentration) values reported as consensus-based sediment quality guidelines for freshwater ecosystems. As for risks of toxicity from pore waters, metal concentrations reached their maxima at the surficial layers of the sediment (1-3 cm) and IWCTU (Interstitial Water Criteria Toxicity Unit) observed for Pb and to a lesser extent Cd, violated the corresponding water quality data recommended by USEPA.

Using ICP-AES and ICP-MS, several metals were analyzed in water and suspended particulate matter (SPM) samples collected under normal turbidity conditions at various stations from Deûle river (in northern France) to assess the impact of a former smelting plant on the fate of particulate elements and on the water quality in this aquatic environment. Compared to their regional background, particulate Pb, Zn and Cd were found to be most enriched, suggesting anthropogenic inputs from bed sediments into the water column mainly due to physical disturbances induced by barges traffics. Conversely, no significant enrichments of particulate metals such as Cu, Cr and Ni were observed in Deûle SPM. Characterization of SPM with analyses of mineralogical and chemical compositions-using environmental scanning electron microscopy equipped with an energy dispersive X-ray spectrometer (ESEM/ EDS)-indicated the presence of micro-specimens attributed to anthropogenic minerals, mostly PbS and ZnS. The calculated enrichment index (or the geoaccumulation index, I geo ), enrichment factor (EF) and the partition coefficient (K d ) confirmed that SPM was strongly polluted in cadmium, lead and zinc, moderately polluted in copper and unpolluted in chromium and nickel. Based on the analytical data obtained for SPM from the BCR (European Community Bureau of Reference) sequential extraction scheme, it was concluded that: (i) the reducible phases were largely more important for the binding of Pb and Cd than that of Zn and Ni and in a lesser extent Cu and Cr; (ii) copper was found to be mostly associated with the sulphides/ organics fraction; (iii) chromium with a lithogenic origin was extracted in the largest percentage in the residual phase; and (iv) zinc was bound to the exchangeablecarbonate phase in the largest percentage in the particles analysed, followed by nickel and cadmium, suggesting that these metals might be easily remobilized if changes in environmental conditions would occur.

Aims The ubiquitous and extensive natural chlorination of organic matter in soils, leading to levels of chlorinated soil organic matter that often exceed the levels of chloride, remains mysterious in terms of its causes and regulation. While the composition of plant species and the availability of labile organic matter was recently shown to be important, the physical localization of chlorination in soils remains unclear but is a key for understanding regulation and patterns observed. Here we assess the relative importance of organic matter chlorination in (a) bulk soil, (b) the plant roots plus the rhizosphere zone surrounding the roots, and (c) above-ground plant biomass, in an experimental plant-soil system.Methods A radiotracer, 36 Cl, was added to study translocation and transformations of Cl − and Cl org in agricultural soil with and without wheat (Triticum vulgare) over 50 days.Results The specific chlorination rates (the fraction of the added 36 Cl − converted to 36 Cl org per day) in soil with plants was much higher (0.02 d −1 ) than without plants (0.0007 d −1 ) at peak growth (day 25). The plant root and rhizosphere showed much higher formation of 36 Cl org than the bulk soil, suggesting that the rhizosphere is a hotspot for chlorination in the soil. In addition, the treatment with plants displayed a rapid and high plant uptake of Cl − . Conclusions Our results indicate that the rhizosphere harbour the most extensive in-situ chlorination process in soil and that root-soil interaction may be key for terrestrial chlorine cycling.

To evaluate adverse impacts of metal pollution originating from smelting activities on the aquatic ecosystem of Deûle river in northern France, water samples were collected from five selected stations along a contaminated region of this river (during two surveys: April-June 2005 and April-May 2007). All samples were analysed using inductively coupled plasma (ICP) atomic emission spectroscopy and/or ICP-mass spectrometry. Both the concentrations of dissolved and particulate elements were determined, and analytical data were compared with national and international water/particle quality guidelines as well as with some values reported in the literature for polluted rivers. For all the metals studied (i.e. Cd, Cr, Cu, Mn, Ni, Pb and Zn), our investigations showed that the effects of the dissolved phase on this aquatic medium were weak, according to water quality status established by US Environmental Protection Agency, USEPA (1994USEPA ( , 1999. Conversely, the levels of metals in suspended particulate matter were found to be much higher than local background contents and natural reference levels in French catchments. These levels were further quantified as "serious" contamination, i.e. above the "red" range that was previously elaborated by most existing metal-contamination scales in French basins of similar geology. The affinity of these metals for the particulate phase in Deûle waters follows the order: Cd >Cr > Pb > Zn = Mn > Cu > Ni. The trace metals released from anthropogenic activities were found to be partly bound to the reactive particulate phase, calcite, which is sensitive to physico-chemical variations occurring in the river ecosystem. To appraise the risk of ecotoxicity by metals, predictions on the ability to release metallic pollutants from calcite into waters were made successfully by testing three equilibrium geochemical speciation models (JCHESS, VISUAL MINTEQ and WINHUMIC) in which soluble organic matter was taken into account. Calculations showed that metal-water-calcite systems in Deûle River are close to thermodynamic equilibrium with generation of solid solutions, MeαCa 1-αCO 3 , by (co)precipitation Water Air Soil Pollut (and/or adsorption reactions. On the basis of results mentioned here, more measurements of river chemistry and assessments of predictive capabilities of chosen water-quality guidelines with time would be developed in aquatic and calcareous areas for controlled dredging operations or other treatment engineering works.

An automatic trace metal monitoring station (ATMS) system was implemented to study seasonal and short time changes in selected metal concentrations in two river courses influenced by mine drainage. High frequency monitoring over periods of months revealed daily variations of zinc, iron and copper, and also proved the use of ATMS as an early warning system in such polluted environments. Complementary measurements with ICP-MS (inductively coupled plasma-mass spectrometry), ionic chromatography, and thermodynamic equilibrium calculations also gave some new insights into the geochemical behaviour of the metals in these two rivers.

Environmental context Exchange processes at the water–sediment interface can release metals to riverine waters, having negative effects on organisms in the water column. We investigate the geochemical processes and metal exchange between the surface sediment and the overlying water under metal contamination conditions. Results suggest that the sediment can be a significant source of metal pollution in aquatic systems, particularly during anoxic events. Abstract Experiments 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.