Assessment of the Contamination of Cultivated Soils by Eighteen Trace Elements Around Smelters in the North of France

Ag, As, Bi, Cd, Co, Cr, Cu, Hg, In, Ni, Pb, Sb, Se, Sn,Tl, Th, U and Zn contamination of cultivated surfacehorizons has been assessed around two lead and zincsmelters in the North of France. The verticaldistribution of Ag, As, Bi, Cu, Hg, Se, Sb and Tl inthe soils has also been examined. The soils around thelead and zinc smelter at Noyelles-Godault arecontaminated by Ag, As, Bi, Cd, Cu, Hg, In, Ni, Pb, Sb,Se, Sn, Tl and Zn. The original concentration in themost contaminated soils may be multiplied by a factorof around 2 to 100, according to the element. Cadmium,Pb and Zn are the most abundant contaminants. The Pband Zn concentrations are correlated to those of theother contaminants, with the exception of Se. Aroundthe Auby zinc smelter, there is a contamination by thesame elements, but in different proportions, inaddition to Cr contamination. Contamination by Se canreach a depth of around 1 m, whereas contamination byAg, As, Bi, Cu, Hg, Sb and Tl is confined to the top 30cm. Although the contaminant content in most soilsdepends on the distance from the plant, Secontamination would appear to vary to a greater extentaccording to the physico-chemical soil conditions.     

Trace element distributions in soils developed in loess deposits from northern France

A pedo‐geochemical survey was carried out in the Nord‐Pas de Calais region (France) on soils developed in loess deposits. Total concentrations of Al, Fe and 18 trace elements, as well as common soil characteristics, were determined in samples from 52 surface and 97 deep horizons developed in these loess deposits. The Pb isotopic composition was determined in two sola. The composition of deep horizons, compared with that of the upper continental crust, with that of horizons developed from 21 other sedimentary rocks from the region and with that of loess from various parts of the world, confirms that loess from the Nord‐Pas de Calais region derives from multi‐recycled and well‐mixed ancient sedimentary rocks. Correlation analysis shows that least mobile (i.e. ionic potential (Z/r) is between 3 and 7) geogenic elements (Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V, Zn) are associated with the fraction <2 µm (which we define as ‘lutum’). More mobile elements (As, Cd, Hg, Mn, Mo, Sb, Se) are less associated with this fraction. Cadmium is particularly linked to Mn. The distribution of [trace element]/([Al] or [Fe]) in the French loess gives the background content for soils developed from most sedimentary materials in northwestern Europe. Topsoils are enriched with all the trace elements examined, except Co, Cr and Ni. Enrichments with Cd, Cu, Mn and Zn are greater in cultivated soils than in forest soils. Enrichments with Pb and with Cu, Hg, Mo, Sb, Se and Sn are mainly due to human contamination through atmospheric fallout. Organic matter seems to act as a sink for all the exogenous trace elements.     

Contamination of Urban Soils in an Area of Northern France Polluted by Dust Emissions of Two Smelters

The contamination of 27 urban topsoils has been assessed around two lead and zinc smelters (Metaleurop Nord and Umicore) in the North of France. Eighteen trace elements have been analysed (Ag, As, Bi, Cd, Co, Cr, Cu, Hg, In, Ni, Pb, Sb, Se, Sn, Tl, Th, U and Zn). The investigation included the study of the vertical distribution of Cd, Pb and Zn as indicators of pollution. It was shown that Cd, In, Pb, Sb and Zn were major pollutants followed in lesser quantities by Ag, Bi, Cu and Hg. In addition, As, Ni, Se, Sn and Tl were present at levels slightly higher than regional agricultural values. The other elements (Co, Cr, Th and U) were at endogenous levels. The observations have highlighted the strong heterogeneity of the physico-chemical parameters of urban soils and the existence of heavy contamination of the under layers by Cd, Pb and Zn. A potential transfer of metals from the topsoil to the deeper layers and especially Cd and Zn, is not excluded. Indeed the soil rework is not the only factor explaining contamination level of the deeper layers of the studied soils. The comparison of the studied element concentrations in urban soils with nearby local agricultural values shows that the dust emission originating from the Metaleurop and Umicore smelters were not the only source of contamination. Thus a large contamination of the studied urban soils by Sb and In could be explained by domestic combustion of coal for heating.     

Water-Quality Diagnosis and Metal Distribution in a Strongly Polluted Zone of Deûle River (Northern France)

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 exchangeable-carbonate 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.     

Impacts of Metal Contamination in Calcareous Waters of Deûle River (France): Water Quality and Thermodynamic Studies on Metallic Mobility

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 (1994, 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-αCO₃, by (co)precipitation 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.     

Environmental Impacts of Heavy Metal Discharges from a Smelter in Deûle-canal Sediments (Northern France): Concentration Levels and Chemical Fractionation

Heavy metal pollution in sediments derived from the Deûle canal and sampled at different sites not far from a smelting plant has been examined in the present work in order to identify the sources of these metals and to assess the sediment environmental quality. The total concentrations of lead, zinc, cadmium, thallium, indium and tin in the samples were determined using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Our investigations have revealed that metal pollution is readily apparent in the studied sediments, with metals contents largely exceeding those measured in the background soils: maximum values are obtained for sediments collected near the industrial zone. The chemical forms of Pb, Zn, Cd, Tl, In and Sn in these sediments have also been studied using a sequential extraction method in order to evaluate their possible mobility, bioavailability and toxicity in this aquatic environment. Overall, the averaged fractionation of Pb and Zn is dominated, in a decreasing order, by the easily reducible, oxidizable and carbonate fractions. The importance of oxidizable phase (which is assumed to be composed mainly of organic matter and sulphides) in the Pb and Zn fractionations has been confirmed by the detection of X-ray diffraction peaks ascribed to galena (PbS) and wurtzite (ZnS) in contaminated sediment samples. Anthropogenic Tl, In, and Cd are mainly retained in Fe–Mn oxides/hydroxides, whereas anthropogenic Sn predominates in aluminosilicates/clays. We suspect that elevated percentage levels of Pb, Zn, Cd and In in the reducible fraction constitute a particular potential risk to this aquatic environment in case early diagenetic phenomena (that are observed in the sedimentary material) and physical disturbances (that occur in the water column) both take place strongly in the medium.