Nicolas Proix

Vertical distribution of Cd, Pb and Zn in soils near smelters in the North of France

The analysis of the horizons of 12 soil profiles confirm occasionally significant levels of Cd, Pb and Zn contamination in the areas surrounding two lead and zinc smelters in the North of France. A pedological approach enabled the original Cd, Pb and Zn content of the horizons to be estimated, based on physico-chemical characteristics of soil unaffected by contamination. The main contamination was found in the upper 20-30 cm. Traces of Cd and Zn contamination were found at a depth of around 2 m. The mobility of the metals may be classified in the following order: Cd>>Pb> or =Zn. The concentration profile of a metal seems insufficient to evaluate its movement as the metal could have been leached beyond the contaminated horizons. The depth reached by the metals increases with their concentration in the surface horizon; a decrease in pH and an increase in sand content seem to facilitate their movement. The depth reached by Zn increases with the organic carbon content in the surface horizon. Earthworm galleries act as paths via which metals migrate downwards

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.

Factors affecting trace element concentrations in soils developed on recent marine deposits from northern France

Total concentrations of 18 trace and 2 major elements (Al, Fe) as well as physico-chemical characteristics (texture, organic C, pH, CaCO 3 , CEC) were measured in cultivated soil samples (fraction <2 mm) from 23 surface and 38 deeper horizons developed in recent marine deposits. Correlations between trace element contents and other soil parameters were compared in order to reveal those soil factors affecting the trace element distributions. Whatever the horizon type, Co, Cr, In, Ni and V are almost exclusively associated with the fine (<20 μm) mineral fraction and do not show a direct association with organic matter. Bismuth, Sn, Tl and Zn also show a close association with the fine mineral fraction of the deep horizons, but seem to be partly associated with organic matter in the ploughed horizons. In the deep horizons, the association of Cd, Cu and Pb with the fine mineral fraction is clearly less close, while these elements appear to be associated with organic matter in the ploughed horizons. The Mn content increases with that of the fine mineral fraction up to a certain point. Arsenic, Mo and Sb contents are poorly correlated with the fine solid phase of the deep horizons. The distribution of Hg does not appear to be associated with any specific soil component. The ploughed horizons are highly enriched with Pb, Cu, Cd, Hg and Se (+ 84% to + 225%) and moderately enriched with Tl, Mn, Sb, Bi, Sn and Zn (+ 7% to + 48%). There is no surface enrichment of As, Co, Cr, In, Mo, Ni and V. It is possible to model most of the trace element distributions with pedotransfer functions of the physico-chemical characteristics.

Estimation of Soil Trace Metal Bioavailability using Unbuffered Salt Solutions: Degree of Saturation of Polluted Soil Extracts

Soil trace metal extractability by 0.01 mol l−1 CaCl2, 0.1 mol l−1 NaNO3 and 1 mol l−1 NH4NO3 solutions is very low. The hypothesis, according to which the saturation of extracts limits the concentrations in solution, was tested by the study of polluted soils. Thus, according to our calculations, cadmium and copper did not precipitate as carbonates, hydroxides and phosphates. In contrast, zinc might precipitate as phosphate, lead as carbonate, hydroxide, sulfate and phosphates. The influence of such phenomena on the estimation of Pb bioavailability was tested by studying the lead uptake of radish plants cultivated in sandy soils artificially enriched with lead. It was then demonstrated that the saturation of the solutions did not in these conditions allow the evaluation of lead bioavailability using such chemical extractions.

Fractionation of anthropogenic lead and zinc in Deûle River sediments

Environmental context. Metal contamination from smelting plants can have significant environmental and geochemical impacts on surrounding river systems, where large amounts of ores, dusts and slag are often discharged. Pollution levels in a river in northern France in the vicinity of a plant that had been producing zinc and lead have been measured. The authors assessed and identified the forms and phases of these metals in the polluted sediments, in order to assess the ability of these metals to pass into water when physicochemical changes (pH, redox potential) occur in the medium, for instance, as a result of dredging and barge traffic. Abstract. The degradation of a fluvial environment, the Deule River in northern France, with metals has been examined. Sites of environmentally significant sediment metal contamination were identified near a former smelting plant (Metaleurop) that produced lead and zinc. The chemical fractionation of sedimentary lead and zinc was carried out by using a four-stage sequential procedure in the polluted sediments. Chemical treatments were performed on these sediments with increasingly strong phase-specific reagents and under controlled thermal conditions; the recovered solutions were subsequently analysed using inductively coupled plasma–atomic emission spectroscopy (ICP-AES). The partitioning of lead and zinc in Deule River sediment samples was further compared with those found in less contaminated sites upstream and downstream from the former Metaleurop factory. Analytical data showed the extent of industrial pollution in this sediment, particularly, the implication of: (i) anthropogenic lead and zinc on the easily extractable fraction; (ii) smelter inputs containing of sulfidic ores on the sulfide/organic fraction; and (iii) smelter dust, slags and possibly ores derived from oxides in the reducible fraction. Overall, in polluted water, sediment-bound lead and zinc were found to be associated with all the sedimentary phases (the average mass percentages of lead and zinc in the exchangeable ions/carbonate fraction were respectively: 12% and 23%; in Fe and Mn oxides and hydroxides: 48% and 35%; in sulfides and organics: 33% and 29%; and in clays and aluminosilicates: 7% and 14%). Using X-ray diffraction, heavy minerals that were previously separated from sediments by decantation with gravity were shown to consist mostly of galena (PbS), wurtzite (ZnS), and pyrite (FeS2), showing the importance of sulfides in this sedimentary material. Using environmental scanning electron microscopy with energy dispersive X-ray spectroscopy (ESEM/EDS), sediments were found to be highly heterogeneous assemblages or aggregates, but with some isolated crystals that were identified. Detailed ESEM/EDS analyses (with imaging) have enabled us to demonstrate the existence of numerous lead and zinc phases that agree well with X-ray diffraction results and sequential extraction data.

Sustainability of an in situ aided phytostabilisation on highly contaminated soils using fly ashes: Effects on the vertical distribution of physicochemical parameters and trace elements

Aided phytostabilisation using trees and fly ashes is a promising technique which has shown its effectiveness in the management of highly metal-contaminated soils. However, this success is generally established based on topsoil physicochemical analysis and short-term experiments. This paper focuses on the long-term effects of the afforestation and two fly ashes (silico-aluminous and sulfo-calcic called FA1 and FA2, respectively) by assessing the integrity of fly ashes 10 years after their incorporation into the soil as well as the vertical distribution of the physicochemical parameters and trace elements (TEs) in the amended soils (F1 and F2) in comparison with a non-amended soil (R). Ten years after the soil treatment, the particle size distribution analysis between fly ashes and their corresponding masses (fly ash + soil particles) showed a loss or an agglomeration of finer particles. This evolution matches with the appearance of gypsum (CaSO4 2H2O) in FA2m instead of anhydrite (CaSO4), which is the major compound of FA2. This finding corresponds well with the dissolution and the lixiviation of Ca, S and P included in FA2 along the F2 soil profile, generating an accumulation of these elements at 30 cm depth. However, no variation of TE contamination was found between 0 and 25 cm depth in F2 soil except for Cd. Conversely, Cd, Pb, Zn and Hg enrichment was observed at 25 cm depth in the F1 soil, whereas no enrichment was observed for As. The fly ashes studied, and notably FA2, were able to reduce Cd, Pb and Zn availability in soil and this capacity persists over the time despite their structural and chemical changes.

Distribution coefficient and redox behaviour of uranium in Authie Bay (northern France)

Some mechanistic aspects associated with uranium release/immobilization and sedimentation in Authie Bay are presented in the present work. For this purpose, U contents in estuarine oxic waters, porewaters and sediment solids are determined. These analytical data allow us to appraise the partitioning of this metal between the liquid phase and the particulate matter/sedimentary material by calculating its distribution coefficient. Our findings further reveal that the distribution coefficient varies significantly with depth probably in response to the microbial activities in these sediments. This is confirmed by our studies on the geochemical behaviour of Fe and Mn in Authie Bay sediments. Finally, studies on the thermodynamic characteristics of sedimentary U in Authie Bay are undertaken in order to select possible U water–mineral equilibria that could involve in this environment, and to help define conditions of sedimentary U bioreduction.

The chemical behavior of sedimentary uranium in Authie Bay (France)

A general study on uranium present at trace levels in anoxic sediments derived from Authie Bay (in northern France) has been undertaken. For that purpose, concentrations of various uranium species in pore waters and recovered solutions (after mineralization of sediments) were determined by ICP-AES and ICP-MS. To access the extent of early diagenesis occurring in these sediments, reduced solid sulfur species were determined after their conversion into H2S gas following sequential extraction procedures. Our preliminary findings reveal that dissolved U(VI) precipitates rapidly with depth in pore waters certainly in the form of insoluble U(IV). Under stronger reducing conditions, new aqueous species [mostly and ] in which uranium is in oxidation state IV are formed in the pore water. Valuable interpretation of these particular properties of sedimentary U has necessitated a global examination of sediment biochemistry because of the influence of bacterial activities on the chemistry of Fe, Mn, S and more particularly U by metal-reducing bacteria.

Radial metal concentration profiles in trees growing on highly contaminated soils

The soil around Metaleurop, a big smelter, is heavily contaminated by Zn, Pb, Cd and Cu. In order to compare the impact of different soil amendments on the metal availability to trees, the polluted soil section was divided in a reference parcel and two others with either sulfo-calcic or silico-aluminous ash amendments. Five different tree species were planted on the parcels and the uptake of heavy metals in these trees was studied. Total and labile metal fractions were assessed in each of the 3 parcels. The mobility and assimilation of the metals was highest in the non-amended, reference soil parcel which had the lowest pH, organic matter and carbonate content. In all soils, pH decreased while organic matter content and mobility of the metals increased over time. Highest bulk concentrations of trace metals were found in white willow trees (Salix alba L.). Laser ablation-ICPMS was used to study changes in metal accumulation over a period of 10 years after planting the trees. The radial metal profiles in the trunk core samples varied between elements and tree species, however, in all willow trees the radial Cd and Zn profiles were significantly correlated. Radial pollutant concentration patterns are discussed in terms of seasonal effects, health status, tree species and metal mobility in the soil. For Cd and Zn, the profiles were influenced by their mobility in the soils. In general, periodical patterns were observed for Pb. Cu concentration profiles were decreasing over time, with the strongest decrease in the initial growth period.