Use of an in vitro digestion method to estimate human bioaccessibility of Cd in vegetables grown in smelter-impacted soils: the influence of cooking

Metal contamination of urban soils and homegrown vegetables has caused major concern. Some studies showed that cadmium (Cd) was among the most significant hazards in kitchen garden soils and prolonged exposure to this metal could cause deleterious health effects in humans. In general, most risk assessment procedures are based on total concentrations of metals in vegetables. The present study assesses human bioaccessibility of Cd in vegetables cultivated in smelter-impacted kitchen garden soils. Seven vegetables (radish, lettuce, French bean, carrot, leek, tomato, and potato) were considered. Using the UBM protocol (unified BARGE bioaccessibility method), the bioaccessibility of Cd was measured in raw/cooked vegetables. A considerable amount of Cd was mobilized from raw vegetables during the digestion process (on average 85% in the gastric phase and 69% in the gastrointestinal phase), which could be attributed to a high uptake of Cd during the growth of the vegetables. Most Cd is accumulated in the vacuoles of plant cells, except what is absorbed by the cell wall, allowing Cd to be released from plant tissues under moderate conditions. Cooking by the steaming process generally increased the bioaccessibility of Cd in French bean, carrot, and leek. For potato, few or no significant differences of Cd bioaccessibility were observed after the steaming process, while the frying process strongly decreased bioaccessibility in both phases. The estimation of metal bioaccessibility in vegetables is helpful for human health risk assessment.

Arsenic mobility and speciation in contaminated kitchen garden and lawn soils: an evaluation of water for assessment of As phytoavailability

Emissions from primary lead smelters have been recognized as one of the mainly factor which has contributed to the contamination of soils by metals. Less attention has been paid to volatile metalloids such as arsenic (As) which accompanies lead (Pb) smelting activities. One of the objectives of this study was to determine the As concentrations in various extracting solutions using a collection of urban soils located no far away from two former Pb and zinc plants in the North of France. The procedure for the determination of As, As(III), and As(V) with hydride vapor generator atomic absorption spectrometry was described in details. Pseudo-total concentrations of As in the studied soils ranged from 5.3 to 65.9 mg kg(-1). Good correlations were found between As and lead, zinc, and cadmium concentrations in soils. These depended on the soil uses and the soil distance from the source of contamination. Because the form of As may pose a health risk to human population, its speciation was determined in each urban top soils. Very good correlations were found between As(III) and As(V) versus As concentrations in soils studied, but the results did no permit to establish a relation between the location of soils and their uses. In contrast, it was shown that the highest mobility factor and lowest partitioning index values were related to the location. The mobilty of As depended on the assimilated phosphorus (P), carbonate contents, and pH. The percentages of the water-extractable As concentrations ranged from 0.3 to 3.0% of the As concentrations in soils. Very good positive correlations between water-extractable As(III) and As(V) versus water-extractable As concentrations were obtained. It was shown that the water-extractable As(III) concentrations depended on the soil uses. The results revealed that soils for which the As was the most mobile presented the highest water-extractable As concentrations. Principal component analysis indicated that mechanisms related to the release of As depended on the physico-chemical parameters of the soils, particularly on the assimilated P, organic matter, and/or iron oxides/hydroxides contents. Finally, the glasshouse experiments using ryegrass as plant model and three soils with similar physico-chemical parameters with regard to the PCA analysis showed that the water extracting solution could be a good indicator to evaluate the As phytoavailability.

Effect of Miscanthus cultivation on metal fractionation and human bioaccessibility in metal-contaminated soils: comparison between greenhouse and field experiments

The in situ stabilization of metals in soils using plants with great biomass value is a promising, cost-effective, and ecologically friendly alternative to manage metal-polluted sites. The goal of phytostabilization is to reduce the bioavailable concentrations of metals in polluted soil and thus reduce the risk to the environment and human health. In this context, this study aimed at evaluating Miscanthus × giganteus efficiency in phytostabilizing metals on three contaminated agricultural sites after short-term exposure under greenhouse conditions and after long-term exposure under field conditions. Particular attention was paid to the influence of Miscanthus cultivation on (i) Cd, Pb, and Zn fractionation using sequential extractions and (ii) metal bioaccessibility using an in vitro gastrointestinal digestion test. Data gave evidence of (i) different behaviors between the greenhouse and the field; (ii) metal redistribution in soils induced by Miscanthus culture, more specifically under field conditions; (iii) higher environmental availability for Cd than for Pb and Zn was found in both conditions; and (iv) overall, a higher bioaccessible fraction for Pb (about 80 %) and Cd (65-77 %) than for Zn (36-52 %) was recorded in the gastric phase, with a sharp decrease in the intestinal phase (18-35 % for Cd, 5-30 % for Pb, and 36-52 % for Zn). Compared to soils without culture, the results showed that phytostabilization using Miscanthus culture provided evidence for substantial effects on oral bioaccessibility of Cd, Pb, and Zn.

Combining spatial distribution with oral bioaccessibility of metals in smelter-impacted soils: implications for human health risk assessment

Geostatistical analysis and GIS-based spatial mapping have been widely used for risk assessment of environmental pollution. The objectives of this study were to: (1) investigate the spatial variability of pseudototal concentrations of Cd, Pb, and Zn; (2) estimate the degree of contamination on the basis of pollution indexes; and (3) combine geostatistical analysis with oral bioaccessibility to better assess the population's exposure to metals in smelter-impacted soils. Implications for human health risks were assessed by considering soil as a contaminant source, a release mechanism of contaminated soil to the hands, ingestion as an exposure route, and metal bioaccessibility. The bioaccessibility data in the gastric (G) and gastrointestinal (GI) phases were integrated into the standard hazard quotient-based risk assessment method. Using pollution indices showed that the entire area studied was highly polluted in terms of soil metal concentrations. However, the spatial pattern of health risk levels did not coincide with the spatial distribution of the degree of soil contamination. Introducing the bioaccessible fraction of metals from soils into the exposure calculations resulted in a substantial decrease in calculated risk (HI, hazard index) and provided a more realistic estimate of exposure to the three metals. For the highly exposed population, 46% of the soils studied provided an HI-G > 1.0 and 15% provided an HI-GI > 1.0, suggesting probable adverse health effects in children. The present study highlights the importance of conducting studies taking into account metal bioaccessible values in risk assessment.

Suitability of Miscanthus species for managing inorganic and organic contaminated land and restoring ecosystem services. A review

The mitigation of potential health hazards and land scarcity due to land use change can be addressed by restoring functional and ecosystem services of contaminated land. Physico-chemical remediation options are criticized as being costly and not providing environment-friendly solutions. The use of plants and associated microorganisms could be a sustainable, cost-effective option to reduce pollutant exposure. Phytomanagement aims at using valuable non-food crops to alleviate environmental and health risks induced by pollutants, and at restoring ecosystem services. Suitable plant species must be tolerant to contaminants, reduce their transfer into the food chain, and efficiently produce marketable biomass. Based on Miscanthus' capacity to sequestrate inorganic contaminants into the root system and to induce dissipation of persistent organic contaminants in soil, these plant species are favorable for phytostabilization and phytodegradation. Among Miscanthus species, the noninvasive hybrid Miscanthus × giganteus, with a high lignocellulosic content, is a promising biomass crop for the bio-economy, notably the biorefinery and bioenergy industries. Planting this species on contaminated and marginal land is a promising option to avoid changes in arable land use to mitigate the food vs. biofuel controversy. Key issues in promoting sustainable management of Miscanthus sp. on contaminated land are: (a) crop suitability, integration, and sustainability in a region with a potential local market; (b) site suitability in relation to the species' requirements and potential, (c) biotic interactions in the landscape diversity; and (d) increase in shoot yields in line with various stressors (e.g., pollutants, drought, cold temperatures), and with minimal inputs.

Effects of field metal-contaminated soils submitted to phytostabilisation and fly ash-aided phytostabilisation on the avoidance behaviour of the earthworm Eisenia fetida

The earthworm Eisenia fetida avoidance behaviour test was used to assess the quality recovery of metal-contaminated soils from lands submitted for 10 years to remediation. Soils were from plots located in the surroundings of a former lead smelter plant of Northern France. Metal concentrations in the soils ranged from 93 to 1231, 56 to 1424, 0.3 to 20 and 15 to 45.5mg metal/kg dry soil for Pb, Zn, Cd and Cu, respectively. Several former agricultural plots were treated either by a single phytostabilisation process involving the plantation of a tree mix or by fly ash aided-phytostabilisation. Silico-aluminous or sulfo-calcic ashes used were ploughed up to a 25- to 30-cm soil depth at a rate of 23.3kg/m(2) (i.e., 6 percent W/W). E. fetida was shown to avoid significantly the 10 years ash-treated soils whose habitat function has to be considered as limited. This avoidance would relate to a change of the texture of soils induced by the addition of ashes and consisting in an increased level of fine silts together with a decreased level of clays. By contrast, afforested metal-contaminated soils appeared for E. fetida as more attractive than unplanted ones. Regarding the influence of the metal contamination of the soils on E. fetida, none of the soils tested even the highest contaminated one was significantly avoided by worms. This lack of reaction would result from the low bioavailability of the metals in the soils tested. At the lights of our results and those previously published on both these ashes and these ash-treated soils, the usefulness of these soil treatments is discussed.

Arundo donax L., a candidate for phytomanaging water and soils contaminated by trace elements and producing plant-based feedstock. A review

Plants and associated microorganisms are used to remediate anthropogenic metal(loid) contamination of water, soils and sediments. This review focuses on the potential of Arundo donax L. (Giant reed) for alleviating risks due to soils, water, and sediments contaminated by trace elements (TE), with emphasis on its advantages and limits over macrophytes and perennial grasses used for bioenergy and plant-based feedstock. Arundo donax is relevant to phytomanage TE-contaminated matrices, notably in its native area, as it possesses characteristics of large biomass production even under nutrient and abiotic stresses, fast growth rate, TE tolerance and accumulation mainly in below ground plant parts. Cultivating A. donax on contaminated lands and in constructed wetlands can contribute to increase land availability and limit the food vs. plant-based feedstock controversy. To gain more tools for decision-taking and sustainable management,further researches on A. donax should focus on: interactions between roots, TE exposure, and rhizosphere and endophytic microorganisms; biomass response to (a)biotic factors; sustainable agricultural practices on marginal and contaminated land; integration into local, efficient, energy and biomass conversion chains with concern to biomass quality and production; Life-Cycle Assessment including contaminant behavior, as well as environmental, agricultural and socio-economic benefits and drawbacks.

Influence of land use on human bioaccessibility of metals in smelter-impacted soils

An investigation was undertaken to evaluate the empirical model developed by Pelfrêne et al. (2012), predicting the human bioaccessibility of Cd and Pb in smelter-contaminated agricultural topsoils, by including other soil uses: 50 urban and 65 woody habitat topsoils collected in the same area. The results showed that land use significantly affected the pseudototal metal concentrations and their oral bioaccessibility. However, whatever the soil's physicochemical parameters and degree of contamination, the 'agricultural' model can be used to simulate metal gastric bioaccessibility in urban and woody habitat soils. To simulate gastrointestinal bioaccessibility, this model can be used directly if the pseudototal metal concentrations are on the same order of magnitude as those usually recorded in the agricultural soils studied or after the use of a correction factor if these concentrations are greater. These results showed that the oral bioaccessibility predictions could be applicable for further environmental risk evaluation.

Assessment of potential health risk for inhabitants living near a former lead smelter. Part 1: metal concentrations in soils, agricultural crops, and homegrown vegetables

Soil contamination by metals engenders important environmental and health problems in northern France where a smelter (Metaleurop Nord) was in activity for more than a century. This study aims to look at the long-term effects of the smelter after its closedown by combining data on the degree of soil contamination and the quality of the crops grown (agricultural crops and homegrown vegetables) in these soils for a better assessment of the local population's exposure to Cd, Pb, and Zn. Seven years after the Metaleurop Nord closedown, (1) the agricultural and urban topsoils were strongly contaminated by Cd, Pb, and Zn; (2) the kitchen garden topsoils were even more polluted than the agricultural soils, with great variability in metal concentrations within the gardens studied; (3) a high proportion of the agricultural crops for foodstuffs did not conform with the European legislation; (4) for feedstuffs, most samples did not exceed the Cd and Pb legislation limits, indicating that feedstuffs may be an opportunity for most agricultural produce; and (5) a high proportion of the vegetables produced in the kitchen gardens did not conform with the European foodstuff legislation. The high contamination level of the soils studied continues to be a risk for the environment and the population's health. A further investigation (part 2) assesses the associated potential health risk for local inhabitants through consumption of homegrown vegetables and ingestion of soil particles by estimating the site-specific human health assessment criteria for Cd and Pb.

Assessment of potential health risk for inhabitants living near a former lead smelter. Part 2: site-specific human health risk assessment of Cd and Pb contamination in kitchen gardens

Metal contamination of urban soils and homegrown products has caused major concern. In Part 1, we investigated the long-term effects of a former smelter on the degree of kitchen garden-soil contamination and the quality of the homegrown vegetables from these gardens. The results showed that the soils retained a high level of contamination and that a large proportion of the vegetables produced did not comply with the legislation on the levels of metals allowed for human consumption. The present study aims to assess the associated potential health risk to local inhabitants through consumption of homegrown vegetables and ingestion of soil particles using a land use-based approach. For lead (Pb), the standard hazard quotient (HQ)-based risk assessment method was used to determine the HQ. For cadmium (Cd), the approach consisted of calculating the HQs and then deriving site-specific assessment criteria (SSAC) using the SNIFFER method. The results suggested that the exposure pathways considered should not engender any form of deleterious health effects for adults. For children, Pb was the main concern and induced a relatively high health risk through soil particle ingestion, and most total soil Cd concentrations exceeded the derived SSAC, in particular, through consumption of vegetables. The metal bioaccessibility in soils was incorporated into the methods to establish more realistic risk assessment measures. This study proposes an approach to integrate different human health risk assessment methods. Further investigations should complete the assessment to improve risk determination, e.g., the determination of metal bioaccessibility in vegetables.

Minimizing Chloride Interferences Produced by Calcium Chloride in the Determination of Cd by Graphite Furnace Atomic Absorption Spectrometry

Cadmium concentrations in CaCl2 extracting solutions at various concentrations were determined by graphite furnace atomic absorption using two background correctors: the deuterium and the high-speed self-reversal background correction systems. Under- and overestimation of the Cd absorbance signals in CaCl2 solutions were observed for concentrations greater than 0.005 M using the deuterium lamp while no important effect was observed using the other background correction system. The analytical performance of the spectrometer for the determination of Cd was studied in 0.01 M CaCl2 solution and single extractions were performed using reference materials and contaminated soil samples. Cadmium was determined using the two background correction systems and a third method, which consists of the use of the deuterium lamp without any chemical modifier, was added to the study. The results showed that the third method was unable to determine Cd concentrations in the CaCl2 solution due to the presence of extractable arsenic and iron. For solutions without any dilution or diluted with a very low dilution factor, the CaCl2-extractable Cd concentrations measured using the deuterium lamp were systematically below those found using the high-speed self-reversal method. These differences were explained by the presence of chloride ions in the atomization step.

Application of the high-speed self-reversal background corrector to the determination of cadmium by chemical vapor generation atomic absorption spectrometry

Concentrations of cadmium (Cd) in extracting solutions (neutral salts) from contaminated soils are often too low to be determined by conventional flame atomic absorption spectrometry. For this reason, determination of Cd requires sensitive analytical methods free from interference problems generated by samples. In this context, vapor generation atomic absorption spectrometry (HGAAS) was combined with a high-speed self-reversal background corrector. This new approach was successfully applied after optimization of the analytical parameters to obtain a maximal absorbance signal of the volatile Cd species. The optimum condition was achieved with a 3% (m/v) NaBH4 in 1.5% (m/v) NaOH reducing solution and a solution containing 0.3 mol/L HNO3. The detection limit was 1 ng mL–1 under the previous conditions and the relative standard deviation was up to 5% for 10 replicate analyses of Cd at 0.2 and 1 ng mL–1, reflecting a very highly sensitive and reproducible method. Moreover, the results showed that the proposed combination was an efficient method to overcome the interference problems caused by different coexisting cations, As, Al, Ca, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn, up to 10 µg mL–1. The method was validated with analyses of two standard reference materials and was used for Cd determination in 0.01 mol/L CaCl2 extracts from contaminated kitchen garden soils. The data were compared with those obtained by two other more conventional methods, electrothermal atomic absorption spectrometry (ETAAS) and flame atomic absorption spectrometry (FAAS). The analytical results obtained by the ETAAS and HGAAS were in a good agreement, suggesting the suitability of the method for Cd determination in 0.01 mol/L CaCl2 extracting solution.

Effects of grinding and shaking on Cd, Pb and Zn distribution in anthropogenically impacted soils

The effects of grinding size and shaking process on the results of Cd (cadmium), Pb (lead) and Zn (zinc) distribution measurements three agricultural and three kitchen garden soils highly contaminated by past atmospheric fallout of two lead and zinc smelters in northern France were studied. The physico-chemical parameters and pseudo-total concentration of metals within these soils were determined. The fractionation of metals was performed in triplicate, using the procedure recommended by the Standards, Measurements and Testing program (SM&T), on each air-dried soil sample, ground to pass through 2-mm, 0.315-mm and 0.250-mm sieves and using a reciprocating or rotary shaker. The samples were analysed by flame or electrothermal absorption atomic spectrometry using a self-reversal background system. For both shaking processes, the grinding size had no effect on the fractionation of metals in contaminated agricultural soils. In contrast, using a reciprocating shaker, the fractionation of metals in the kitchen garden samples sieved at <2mm was so different that in the samples prepared to pass through the 0.315-mm and 0.250-mm sieves. Therefore changes (use of a 50 mL graduated polypropylene centrifuge tube, evaporation of the solution to a fixed volume in step 3 and the use of an automatic shaking heating bath) were made to the initial procedure and a rotary shaker was used to improve the suspension of the soil samples during extraction. For all grinding sizes, the fractionation of the three metals contained in the contaminated kitchen garden soil samples was successfully achieved. Nevertheless, some discrepancies from samples sieved at <2mm were obtained. On the other hand, it is worth noting that the effect of the type of shaker on the distribution of metal depended on the soil and the grinding size. From an analytical point of view, precision and trueness were improved after optimisation of the procedure for all sequential extraction procedure steps. The best results were obtained for samples sieved at <0.250 mm. Similar trends were obtained using the CRM BCR(®)-701 certified material. All the results showed that optimisation of the sequential extraction procedure could be adopted for the Cd-, Pb- and Zn-partitioning in contaminated kitchen garden soils with high-level anthropogenic sources.

Lead contamination in French children's homes and environment

Lead in homes is a well-known source of childhood lead exposure, which is still of concern due to the health effects of low lead doses. This study aims to describe lead contamination in the homes of children aged 6 months to 6 years in France (without overseas). Between October 2008 and August 2009, 484 housing units were investigated. Lead in tap water and total and leachable lead levels from floor dust, outdoor soils and paint chips were measured. X-ray fluorescence measurements were carried out on non-metallic and metallic substrates. Nationwide results are provided. The indoor floor dust lead (PbD) geometric mean (GM) was 8.8 μg/m² (0.8 μg/ft²) and 6.8 μg/m² (0.6 μg/ft²) for total and leachable lead respectively; 0.21% of homes had an indoor PbD loading above 430.5 μg/m² (40 μg/ft²). The outdoor play area concentration GM was 33.5 mg/kg and 21.7 mg/kg in total and leachable lead respectively; 1.4% of concentrations were higher than or equal to 400 mg/kg. Outdoor floor PbD GM was 44.4 μg/m² (4.1 μg/ft²) that was approximately 3.2 times higher than the GM of indoor PbD. Lead-based paint (LBP) was present in 25% of dwellings, LBP on only non-metallic substrates was present in 19% of homes and on metallic substrates in 10% of dwellings. The GM of lead concentrations in tap water was below 1 μg/L; 58% of concentrations were lower than 1 μg/L and 2.9% were higher than or equal to 10 μg/L. The age cut-off for homes with lead would be 1974 for paint and 1993 for indoor floor dust. This study provides, for the first time, a look at the state of lead contamination to which children are exposed in French housing. Moreover, it provides policy makers an estimate of the number of French dwellings sheltering children where abatement should be conducted.

Effects of iron concentration level in extracting solutions from contaminated soils on the determination of zinc by flame atomic absorption spectrometry with two background correctors

Zinc and iron concentrations were determined after digestion, water, and three-step sequential extractions of contaminated soils. Analyses were carried out using flame absorption spectrometry with two background correctors: a deuterium lamp used as the continuum light source (D(2) method) and the high-speed self-reversal method (HSSR method). Regarding the preliminary results obtained with synthetic solutions, the D(2) method often emerged as an unsuitable configuration for compensating iron spectral interferences. In contrast, the HSSR method appeared as a convenient and powerful configuration and was tested for the determination of zinc in contaminated soils containing high amounts of iron. Simple, fast, and interference-free method, the HSSR method allows zinc determination at the ppb level in the presence of large amounts of iron with high stability, sensitivity, and reproducibility of results. Therefore, the HSSR method is described here as a promising approach for monitoring zinc concentrations in various iron-containing samples without any pretreatment.

Bioaccessibility of trace elements as affected by soil parameters in smelter-contaminated agricultural soils: a statistical modeling approach

An investigation was undertaken to identify the most significant soil parameters that can be used to predict Cd, Pb, and Zn bioaccessibility in smelter-contaminated agricultural soils. A robust model was established from an extended database of soils by using: (i) a training set of 280 samples to select the main soil parameters, to define the best population to be taken into account for the model elaboration, and to construct multivariate regression models, and (ii) a test set of 110 samples to validate the ability of the regression models. Total carbonate, organic matter, sand, P(2)O(5), free Fe-Mn oxide, and pseudototal Al and trace element (TE) contents appeared as the main variables governing TE bioaccessibility. The statistical modeling approach was reasonably successful, indicating that the main soil factors influencing the bioaccessibility of TEs were taken into account and the predictions could be applicable for further risk evaluation in the studied area.

Gene expression analysis of 4 biomarker candidates in Eisenia fetida exposed to an environmental metallic trace elements gradient: a microcosm study

Past activities of 2 smelters (Metaleurop Nord and Nyrstar) led to the accumulation of high amounts of Metal Trace Elements (TEs) in top soils of the Noyelles-Godault/Auby area, Northern France. Earthworms were exposed to polluted soils collected in this area to study and better understand the physiological changes, the mechanisms of acclimation, and detoxification resulting from TE exposure. Previously we have cloned and transcriptionally characterized potential biomarkers from immune cells of the ecotoxicologically important earthworm species Eisenia fetida exposed in vivo to TE-spiked standard soils. In the present study, analysis of expression kinetics of four candidate indicator genes (Cadmium-metallothionein, coactosin like protein, phytochelatin synthase and lysenin) was performed in E. fetida after microcosm exposures to natural soils exhibiting an environmental cadmium (Cd) gradient in a kinetic manner. TE body burdens were also measured. This microcosm study provided insights into: (1) the ability of the 4 tested genes to serve as expression biomarkers, (2) detoxification processes through the expression analysis of selected genes, and (3) influence of land uses on the response of potential biomarkers (gene expression or TE uptake).

In vitro digestion and DGT techniques for estimating cadmium and lead bioavailability in contaminated soils: influence of gastric juice pH

A sensitivity analysis was conducted on an in vitro gastrointestinal digestion test (i) to investigate the influence of a low variation of gastric juice pH on the bioaccessibility of Cd and Pb in smelter-contaminated soils (F(B), using the unified bioaccessibility method UBM) and fractions of metals that may be transported across the intestinal epithelium (F(A), using the diffusive gradient in thin film technique), and (ii) to provide a better understanding of the significance of pH in health risk assessment through ingestion of soil by children. The risk of metal exposure to children (hazard quotient, HQ) was determined for conditions that represent a worst-case scenario (i.e., ingestion rate of 200 mg day(-1)) using three separate calculations of metal daily intake: estimated daily intake (EDI), bioaccessible EDI (EDI-F(B)), and oral bioavailable EDI (EDI-F(A)). The increasing pH from 1.2 to 1.7 resulted in: (i) no significant variation in Cd-F(B) in the gastric phase but a decrease in the gastrointestinal phase; (ii) a decrease in soluble Pb in the gastric phase and a significant variation in Pb-F(B) in the gastrointestinal phase; (iii) a significant decrease in Cd-F(A) and no variation in Pb-F(A); (iv) no change in EDI-F(B) and EDI-F(A) HQs for Cd; (v) a significant decrease in EDI-F(B) HQs and no significant variation in EDI-F(A) HQ for Pb. In the analytical conditions, these results show that risk to children decreases when the bioavailability of Pb in soils is taken into account and that the studied pH values do not affect the EDI-F(A) HQs. The present results provide evidence that the inclusion of bioavailability analysis during health risk assessment could provide a more realistic estimate of Cd and Pb exposure, and opens a wide field of practical research on this topic (e.g., in contaminated site management).

Assessing Cd, Pb, Zn human bioaccessibility in smelter-contaminated agricultural topsoils (northern France)

The extractability of Cd, Pb, and Zn was investigated in contaminated agricultural topsoils located in an area highly affected by the past atmospheric emissions of two smelters in northern France in order to assess their mobility and human bioaccessibility. The determination of Cd, Pb, and Zn bioaccessibility (Unified Barge Method, in vitro test) was made to evaluate the absolute trace element (TE) bioavailability. The results highlighted differences in bioaccessibility between Cd, Pb, and Zn (Cd > Pb > Zn). The mean values of the bioaccessible fractions of Cd, Pb, and Zn during the gastric phase were 82, 55, and 33%, respectively, of the pseudototal concentrations, whereas during the gastrointestinal phase, the bioaccessible fractions of metals decreased to 45, 20, and 10%, respectively. Stepwise multiple regression analysis showed that human bioaccessibility was affected by various physicochemical parameters (i.e., sand, carbonates, organic matter, assimilated P, free Al oxides, and pseudototal Fe contents). Sequential extractions were performed as an indication of the TE availability in these soils. Cadmium occurred in the more available fractions, Pb was mostly present as bound by oxides, and a significant contribution to the pseudototal Zn concentration was defined as the unavailable residual form related to the crystalline structures of minerals. The concepts of bioavailability and bioaccessibility are important for quantifying the risks associated with exposure to environmental pollutants and providing more realistic information for human health.

Assessment of fly ash-aided phytostabilisation of highly contaminated soils after an 8-year field trial Part 2. Influence on plants

Aided phytostabilisation is a cost-efficient technique to manage metal-contaminated areas, particularly in the presence of extensive pollution. Plant establishment and survival in highly metal-contaminated soils are crucial for phytostabilisation success, as metal toxicity for plants is widely reported. A relevant phytostabilisation solution must limit metal transfer through the food chain. Therefore, this study aimed at evaluating the long-term efficiency of aided phytostabilisation on former agricultural soils highly contaminated by cadmium, lead, and zinc. The influence of afforestation and fly ash amendments on reducing metal phytoavailability was investigated as were their effects on plant development. Before being planted with a tree mix, the site was divided into three plots: a reference plot with no amendment, a plot amended with silico-aluminous fly ash and one with sulfo-calcic fly ash. Unlike Salix alba and Quercus robur, Alnus glutinosa, Acer pseudoplatanus and Robinia pseudoacacia grew well on the site and accumulated, overall, quite low concentrations of metals in their leaves and young twigs. This suggests that these three species have an excluder phenotype for Cd, Zn and Pb. After 8 years, metal availability to A. glutinosa, A. pseudoplatanus and R. pseudoacacia, and translocation to their above-ground parts, strongly decreased in fly ash-amended soils. Such decreases fit well together with the depletion of CaCl(2)-extractable metals in amended soils. Although both fly ashes were effective to decrease Cd, Pb and Zn concentrations in above-ground parts of trees, the sulfo-calcic ash was more efficient.

Influence of fly ash aided phytostabilisation of Pb, Cd and Zn highly contaminated soils on Lolium perenne and Trifolium repens metal transfer and physiological stress

Due to anthropogenic activities, large extends of soils are highly contaminated by Metal Trace Element (MTE). Aided phytostabilisation aims to establish a vegetation cover in order to promote in situ immobilisation of trace elements by combining the use of metal-tolerant plants and inexpensive mineral or organic soil amendments. Eight years after Coal Fly Ash (CFA) soil amendment, MTE bioavailability and uptake by two plants, Lolium perenne and Trifolium repens, were evaluated, as some biological markers reflecting physiological stress. Results showed that the two plant species under study were suitable to reduce the mobility and the availability of these elements. Moreover, the plant growth was better on CFA amended MTE-contaminated soils, and the plant sensitivity to MTE-induced physiological stress, as studied through photosynthetic pigment contents and oxidative damage was lower or similar. In conclusion, these results supported the usefulness of aided phytostabilisation of MTE-highly contaminated soils.

Spatially explicit analysis of metal transfer to biota: influence of soil contamination and landscape

Concepts and developments for a new field in ecotoxicology, referred to as “landscape ecotoxicology,” were proposed in the 1990s; however, to date, few studies have been developed in this emergent field. In fact, there is a strong interest in developing this area, both for renewing the concepts and tools used in ecotoxicology as well as for responding to practical issues, such as risk assessment. The aim of this study was to investigate the spatial heterogeneity of metal bioaccumulation in animals in order to identify the role of spatially explicit factors, such as landscape as well as total and extractable metal concentrations in soils. Over a smelter-impacted area, we studied the accumulation of trace metals (TMs: Cd, Pb and Zn) in invertebrates (the grove snail Cepaea sp and the glass snail Oxychilus draparnaudi) and vertebrates (the bank vole Myodes glareolus and the greater white-toothed shrew Crocidura russula). Total and CaCl₂-extractable concentrations of TMs were measured in soils from woody patches where the animals were captured. TM concentrations in animals exhibited a high spatial heterogeneity. They increased with soil pollution and were better explained by total rather than CaCl₂-extractable TM concentrations, except in Cepaea sp. TM levels in animals and their variations along the pollution gradient were modulated by the landscape, and this influence was species and metal specific. Median soil metal concentrations (predicted by universal kriging) were calculated in buffers of increasing size and were related to bioaccumulation. The spatial scale at which TM concentrations in animals and soils showed the strongest correlations varied between metals, species and landscapes. The potential underlying mechanisms of landscape influence (community functioning, behaviour, etc.) are discussed. Present results highlight the need for the further development of landscape ecotoxicology and multi-scale approaches, which would enhance our understanding of pollutant transfer and effects in ecosystems.

Growth and metal accumulation in Porcellio scaber exposed to poplar litter from Cd-, Pb-, and Zn-contaminated sites

This study aimed at determining, in the laboratory, the effects of poplar litter collected in woody habitats contaminated by heavy metals on growth and metal accumulation in the terrestrial isopod Porcellio scaber. Cd, Pb, and Zn pseudototal and CaCl(2)-extractable concentrations in litter types were determined using AAS. Juveniles were fed ad libitum, individually, for 28 days with four litter types presenting an increasing gradient of metal contamination. Individuals were weighed every week and metal body burdens were determined at the end of the experiment. From the first week until the end of the experiment, a decrease in P. scaber growth related to the increase of metal concentration in litter types was recorded. Significant correlations were observed between metal body burdens and metal concentrations in litter types. However, Cd accumulation in woodlice appeared to be related to the Cd/Zn concentration ratio in litter types. All these results showed the potential of weight gain in P. scaber as a suitable indicator for litter quality assessment with ecological relevance.

Assessment of fly ash-aided phytostabilisation of highly contaminated soils after an 8-year field trial: part 1. Influence on soil parameters and metal extractability

Sustainable management of large surface areas contaminated with trace elements is a real challenge, since currently applied remediation techniques are too expensive for these areas. Aided phytostabilisation appears to be a cost efficient technique to reduce metal mobility in contaminated soils and contaminated particle spread. In this context, this study aimed at evaluating the long-term efficiency of aided phytostabilisation on former agricultural soils highly contaminated with trace elements. The influence of afforestation and fly ash amendments to reduce metal mobility was investigated. Before being planted with a tree mix, the study site was divided into three plots: a reference plot with no amendment, the second amended with silico-aluminous fly ash and the third with sulfo-calcic fly ash. After eight years, some soil physico-chemical parameters, including cadmium (Cd), lead (Pb) and zinc (Zn) extractability were modified. In particular, pH decreased on the whole site while organic carbon content increased. The alteration of these parameters influencing trace element mobility is explained by afforestation. Over time, concentrations of CaCl(2)-extractable metals increased and were correlated with the soil pH decrease. In the amended soils, extractable Cd, Pb and Zn concentrations were lower than in the reference soil. The results indicated that the two fly ashes buffered natural soil acidification due to vegetation development and limited trace element mobility and thus could limit their bioavailability. For long-term phytostabilisation, special attention should be focused on the soil pH, metal mobility and phytoavailability analysis.

Spatial distribution of metals in smelter-impacted soils of woody habitats: influence of landscape and soil properties, and risk for wildlife

The spatial distribution of total and CaCl(2)-extracted Cd, Pb and Zn concentrations in smelter-impacted soils was investigated over a polluted site (40 km(2)) in Northern France. The study was conducted on 262 soils sampled in woody habitats. Total and extracted concentrations of trace metals (TMs) rose up to 2402 and 59.5 mg kg(-1) for Cd, 41 960 and 13.7 mg kg(-1) for Pb, 38 760 and 143.0 mg kg(-1) for Zn, respectively. The spatial dependence of both total and extracted concentrations showed a high spatial auto-correlation and ordinary kriging was used to predict soil concentrations. Investigating which variables influenced metal concentrations and their spatial distribution, we found that total concentrations mostly depended on the distance from the smelter, the wind and the organic carbon, while extracted concentrations were mainly modulated by the pH. Conditionally to those variables, other soil properties and landscape characteristics influenced both total and extracted concentrations. We conclude that total and extracted TM concentrations are governed by different processes which act at various spatial ranges: total concentrations are mainly related to input and retention of metals (large scale) whereas extracted concentrations were mainly explained by factors controlling metal solubility in soils (local scale). Spatial distributions of total and extracted TMs differed over the area, which should be considered for risk assessment. Maps of risk based on the US EPA's Eco-SSLs (for plants, invertebrates and vertebrates) were realized, showing that wildlife may be at risk but that the relevance of Eco-SSL values is questionable.