Potential risks of metal toxicity in contaminated sediments of Deûle river in Northern France

International audienceThe 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

Elimination of turbidity and bacterial contamination in natural water sources (Ubangi river, Central Africa)

Having access to a natural source of water of sufficiently high quality for human consumption has become a strategic concern for the entire world. In fact, drinking water resources in developing countries are almost non-existent, as they are overused or polluted by intense human activity. Our study aims to develop a natural filter that reduces turbidity and eliminates human pathogens. The process developed should be inexpensive and minimize the use of chemical reagents, and should not be labor intensive. In this context, horizontal sand filtration that uses the natural process of water purification occurring in an aquifer can be regarded as the most suitable water treatment process for developing countries.Disposer d’une source d’eau naturelle de bonne qualité, pour la consommation humaine, est devenu maintenant une préoccupation stratégique pour le monde entier. En effet, les ressources en eaux potables dans les pays en voie de développement sont quasi-inexistantes, car surexploitées ou souillées par une activité humaine intense. L’étude que nous proposons a pour objectif : de mettre au point un filtre naturel qui diminue la turbidité et élimine les agents pathogènes pour l’homme. Le procédé développé peu onéreux devra réduire au maximum l’utilisation de réactifs chimiques, et minimiser toutes interventions humaines. La filtration horizontale sur sable qui utilise le processus naturel de purification de l’eau se produisant dans une nappe aquifère, peut être considéré comme le procédé de traitement de l’eau le plus approprié aux pays en voie de développement et répond aux objectifs fixés.Disponer de una fuente de agua natural de buena calidad, apta para el consumo humano, se ha convertido actualmente en una preocupación estratégica en todo el mundo. En efecto, los recursos de agua potable en los países en vías de desarrollo son prácticamente inexistentes, por exceso de explotación o por contaminación a causa de una actividad humana intensa.El estudio que proponemos tiene por objetivo: desarrollar un filtro natural que reduzca la turbidez y elimine los agentes patógenos perjudiciales para el hombre. El procedimiento desarrollado, de bajo coste, debería reducir al máximo el uso de sustancias químicas reactivas y minimizar cualquier intervención humana. Como la filtración horizontal sobre arena que utiliza el proceso natural de purificación del agua tiene lugar en una capa acuífera, se puede considerar como el procedimiento de tratamiento del agua más adecuado a los países en vías de desarrollo y responde a los objetivos fijados

Metal pollutants in Indian continental coastal marine sediment along a 3,700 km transect: An Electron Paramagnetic Resonance spectroscopic study

We report the analysis and geographical distribution of anthropogenically impacted marine surficial sediments along a 3700 km transect around the continental shelf of India. Sediments have been studied using a mixed analytical approach; high sensitivity electron paramagnetic resonance (EPR), chemical analysis and environmental magnetism. Indian coastal marine deposits are heavily influenced bymonsoon rains flushing sediment of geological and anthropogenic origin out of the subcontinental river systems. That is, climatic, hydro-, geo- and anthropogenic spheres couple strongly to determine the nature of Indian coastal sediments. Enrichment of Ni, Cu and Cr is observed in shelf sediments along both east and west coasts associated with industrialised activities in major urban areas. In the Gulf of Cambay and the Krishna and Visakhapatnam deltaic regions, levels of Ni and Cr pollutants (≥80 and ≥120 ppmrespectively) are observed, sufficient to cause at least mediumadverse biological effects in the marine ecosystem. In these areas sediment EPR spectra differ in characteristic from those of less impacted ones. Modelling enables deconvolution of EPR spectra. In conjunction with environmental magnetism techniques, EPR has been used to characterise species composition in coastal depositional environments. Paramagnetic species can be identified and their relative concentrations determined. EPR g-values provide information about the chemical and magnetic environment of metals. We observe g-values of up to 5.5 and large g-shifts indicative of the presences of a number of para and ferrimagnetic impurities in the sediments. EPR has enabled the characterisation of species composition in coastal depositional environments, yielding marine sediment environmental ‘fingerprints’. The approach demonstrates the potential of EPR spectroscopy in the mapping and evaluation of the concentration and chemical speciation in paramagnetic metals in sediments from marine shelf environments and their potential for source apportionment and environmental impact assessment