Investigation of heavy metal concentrations on urban soils,dust and vegetables nearby a former smelter site in Mortagne du Nord,Northern France

Environmental situations near former industrial sites like Mortagne du Nord (Northern France) in which the soil, dust and homegrown vegetables have been contaminated by heavy metals can represent a sanitary risk to the surrounding population. In order to evaluate the contamination level in different exposition media in this site, 26 urban topsoils, 17 dust and 38 vegetable samples were taken near the former zinc smelter site. All the observed levels on urban soil samples (except one) are over regional agricultural reference values for Cd and Pb. 45 % of the vegetable samples are over the European foodstuff limits and one dust sample taken in the school playground outdoor tarmac area exceeds the French limit in dust set up at 1,000 μg m^?2 for Pb. The Cd and Pb levels fluctuate depending on the use of the ground (kitchen garden, lawn, courtyard) and its location. The lack of simple correlations between the distance from the former smelter site and the Pb concentrations on sampled soils let us think that human activities contributed in the local urban contamination. In this context, who is now responsible for the soil contamination and the human exposure?     

Contamination of soils near a copper smelter by arsenic,antimony and lead

Stack dust from a large Cu smelter near Tacoma, Washington has contaminated soil with As, Sb, and Pb. Within 5 km of the smelter 380 ppm (dry weight) As, 200 ppm Sb, and 540 ppm Pb have been measured in the surface soil (0–3 cm). Plants grown in these soils may be affected and also the consumption of plants coated with this heavy metal rich dust may be of concern.     

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.     

Management of human health risk in the context of kitchen gardens polluted by lead and cadmium near a lead recycling company

Purpose

At the global scale, gardening activities are often performed in urban areas with a historical background of pollution. In this study, a participatory program was developed with citizens concerned by gardening activities near a 50-year-old regulated lead recycling company, with the aim of co-constructing the tools for the assessment and management of potential sanitary risks induced by historic pollution with persistent (eco) toxic metals: lead and cadmium.

Materials and methods

Soils and vegetables (lettuce, leek, celery, carrot, chard, pumpkin, and celeriac) samples were collected from four kitchen gardens neighboring a 50-year-old secondary lead smelter. Both total and in vitro human bioaccessible metal concentrations in the cultivated plants were measured in relation to soil characteristics.

Results and discussion

The results showed that the soils of these gardens were slightly contaminated by metals (Pb, 77 to 236 mg kg^?1; and Cd, 0.5 to 1 mg kg^?1) in comparison with the natural geologic background. However, significant pollution of vegetables can occur especially with lead (Pb up to 9.8 mg kg^?1 in lettuce) and certainly as a result of direct foliar transfer. The washing of plants before consumption is therefore recommended in the context of atmospheric fallout of ultrafine particles enriched with metals.

Conclusions

Metal bioaccessibility measure integrates the influence of metal type, plant type, and soil physico-chemical properties. Based on the results, it is proposed that human bioaccessible fraction of metals may also be currently taken into account as well as total metal quantities and bioaccumulation factors in risk assessment studies performed in gardens. Overall, this study has led to reflections and functional recommendations aimed at reducing human exposure and to finally developing sustainable gardening practices.

     

磷改良剂对中度和高度含碳酸盐的菜园土壤中Cd和Pb环境有效性和植物有效性的影响

The behaviour of metals mainly depends on soil p H, carbonate contents and contamination level, which should be considered for the management of contaminated soils. In this study, kitchen garden topsoils(0–25 cm) were sampled from the area around three smelters in France, with different Cd and Pb contamination levels. Effect of a phosphate amendment(a mixture of diammonium phosphate and hydroxyapatite) on the environmental availability and phytoavailability of Cd and Pb was evaluated by different chemical extractions and cultivating lettuce(Lactuca sativa L.), respectively. Changes in the distribution of Cd and Pb were found in most contaminated soils after phosphate amendment. An increase of Cd and Pb in the residual phase was highlighted in almost all carbonated contaminated soils, whereas a decrease of Pb in the exchangeable, water and acid-soluble phase was observed in most contaminated soils with the lowest carbonate contents. The concentrations of extractable Cd and Pb using calcium chloride and acetic and citric acids generally decreased after the soil amendment. Lettuces grown on amended soils were acceptable for human consumption as regard to Pb concentration. In contrast, some lettuces were unacceptable for human consumption, since the concentrations of Cd in the leaves were higher than the European legislation limit. Surprisingly, in carbonated soils with very low concentration of Cd, the Cd concentrations in lettuce reached up to the European legislation limit, making the lettuce unacceptable for human consumption.Our study highlighted the fact that the total metal concentration in soils does not always allow to predict the metal accumulation in the edible parts of vegetables in order to make a judgement about their acceptability or unacceptability for human consumption.     

Soil lead concentrations in residential Minnesota as measured by ICP-AES

A total of 2454 samples were collected to evaluate the degree, extent, and distribution of Pb contaminated soil in Minnesota. Samples were collected primarily at locations where susceptible populations were concentrated. Soil Pb concentrations in chilldren's play areas, urban gardens, and at open sites were generally below 100 μg g ^?1 when Pb painted structures were absent. Street side and yard soils typically had Pb concentrations between 10 to 300 μg g^?1, with samples collected near major highways or Pb painted structures exhibiting greater values. The most severely contaminated soils were found in localized areas around the foundations of private residences, where concentrations up to 20 136 μg g^?1 were detected. Exterior Pb based house paint is the major Pb source in these soils, and its presence greatly influences the distribution of contaminated soil in individual yards. Contamination attributable to autoemissions is less concentrated but more widespread than contamination from paint. A higher proportion of soils exceeding 1000 wg g^?1 Pb was found in large cities than elsewhere. However, a sufficient number were detected in small cities and rural areas to confirm that high soil Pb levels are not exclusively an urban phenomenon. By examining the degree, extent, and distribution of Pb contaminated soils in Minnesota, this study provides information useful in guiding response actions to reduce children's exposure to Pb by this pathway.     

Permissible Concentrations of Arsenic and Lead in Soils Based on Risk Assessment

Establishing permissible concentrations for As and Pb in soils is of practical importance because of toxicity of these metals, their widespread contamination, and limited resources available for remediation of contaminated soils. The USEPA pathway approach to risk assessment was used to assess an environmental hazard related to As and Pb in soils and to evaluate safe concentrations of these metals in contaminated soil. The results from large-scale field experiments with soil fly ash-biosolids blends were used as input data to analyze pathways of the most intense transfer of the contaminants to a target organism. A direct soil ingestion by children (the soil-human pathway) was considered the most important exposure route to soil As and Pb. A conservative risk analysis shows that As concentrations in soil can reach 40 μg g^-1 without a hazard to exposed organisms. A Pb concentration in soil up to 300 μg g^-1 does not cause an excessive intake of Pb by humans as evaluated by a direct soil ingestion exposure model.     

Soil Surface Geochemical Anomaly Around the Copper-Nickel Metallurgical Smelter

The soils were sampled from the center of airborne contamination caused by long time activity of a copper/nickel smelter complex in the Kola Peninsula, Russia. The soil specimens were taken from an area about 250 km², which included the town of Monchegorsk, with frequency of 1 sample (plot) per 3 km² and heavy metals nickel, copper, cobalt, chromium, lead, cadmium, strontium, iron, manganese and arsenic were measured. The soil surrounding the Smelter, including the inhabited territory of the town, was found to be contaminated by nickel and copper to levels 450- and 250 times higher in comparison to the background, respectively. These soils were found to be extremely toxic and represented a severe threat to human health. Elevated concentrations of iron and arsenic caused by smelter emissions were found too.     

Dry Atmospheric Contribution to the Plant–Soil System Around a Cement Factory: Spatial Variations and Sources—a Case Study from Oman

The present study determines the source of dust particles and investigates their impact on the chemical compositions of plants and soils around a cement factory in Oman within a radius of 10 km of this disturbed ecosystem. A total number of nine samples of the species of plants (Rhazya stricta), nine samples of soils, and nine samples of dust were collected and analyzed for major ions and trace elements including rare earth elements (REEs). Principal component analysis applied to the major and trace element concentrations in the dust indicated the input of at least two sources to the dust in the study area: ophiolites and cement. The REE distribution in the plants and soils revealed that the most available elements to plants originated dominantly from ophiolites rather than from cement. The contribution of cement industry is significant only in the zone located at about 0.500 to 2 km around the cement factory, whereas the contribution of ophiolites increases with distance from the cement factory.     

人为污染土壤中Cd、Pb、和Zn的化学有效性：地球化学反应与口服生物有效性评价

The most recent in vitro tests used to determine metal bioaccessiblility are generally time-consuming and expensive.This study aimed at determining potential relationships between the concentrations of metals extracted using single-extraction methods and the concentrations of bioaccessible metals assessed by a harmonised in vitro test,the Unified BARGE Method (UBM).A total number of 27 soil samples were collected from kitchen gardens and lawns with various physicochemical parameters and contamination levels.Significant relationships were obtained between Cd,Pb and Zn extracted in gastric and gastrointestinal phases and using single extractions.The best relationhips were established using acetic and citric acids for Cd,whereas for Pb,citric acid and ethylenediaminetetraacetic acid (EDTA) were identified as the best extractants.These relationships were improved by means of a linear multiple regression with a downward stepwise procedure involving agronomic parameters (soil cation exchange capacity and assimilated P).This method highlighted the fact that the cation exchange capacity and P contents in soils were the two main parameters that controlled the human bioaccessibility of Cd,Pb and Zn in the gastric phase.Besides,the metal concentrations extracted with the acetic and citric acids correlated well with the metal concentrations in the gastric and gastrointestinal phases,suggesting that the bioaccessible metals were mainly in a soluble form,weakly bound to the organic matter and associated with the carbonates and the Fe and Mn oxides/hydroxides in soils.     

中国农田土壤重金属污染的人体健康风险评估：研究进展与展望

农田土壤重金属污染对食品安全和人体健康构成巨大的威胁。重金属主要通过经口摄入土壤、吸入土壤颗粒、皮肤接触和食物链摄取等暴露途径进入人体,其中经口摄入重金属污染土壤和农产品是主要的暴露途径。人体健康风险评估在农田土壤质量分类和风险管控中起着重要作用。因此,梳理了中国农田土壤重金属污染的人体健康风险评估的发展状况,介绍了人体健康风险评估的基本流程和评估技术,论述了影响人体健康风险评价准确性的主要因素及优化措施。在农田土壤重金属健康风险评估中,应加强耦合污染源识别技术、重视食物消费暴露途径、精准识别不同敏感受体、本土化敏感受体的暴露参数、纳入重金属的生物可给性,同时提高农田土壤重金属健康风险评估的准确性。未来可从加强应对健康风险评估过程不确定性的技术方法、考虑各种饮食的暴露途径和建立本土化的重金属毒性标准数据等多方面深化农田土壤重金属健康风险评估,以期推动中国农田土壤重金属人体健康风险评估的理论和技术发展。     

Mechanisms of metal-phosphates formation in the rhizosphere soils of pea and tomato: environmental and sanitary consequences

Purpose

At the global scale, soil contamination with persistent metals such as lead (Pb), zinc (Zn), and copper (Cu) induces a serious threat of entering the human food chain. In the recent past, different natural and synthetic compounds have been used to immobilize metals in soil environments. However, the mechanisms involved in amendment-induced immobilization of metals in soil remained unclear. The objective of the present work was therefore to determine the mechanisms involved in metal-phosphates formation in the rhizospheric soils of pea and tomato currently cultivated in kitchen gardens.

Materials and methods

Pea and tomato were cultivated on a soil polluted by past industrial activities with Pb and Zn under two kinds of phosphate (P) amendments: (1) solid hydroxyapatite and (2) KH₂PO₄. The nature and quantities of metal-P formed in the rhizospheric soils were studied by using the selective chemical extractions and employing the combination of X-ray fluorescence micro-spectroscopy, scanning electron microscopy, and electron microprobe methods. Moreover, the influence of soil pH and organic acids excreted by plant roots on metal-P complexes formation was studied.

Results and discussion

Our results demonstrated that P amendments have no effect on metal-P complex formation in the absence of plants. But, in the presence of plants, P amendments cause Pb and Zn immobilization by forming metal-P complexes. Higher amounts of metal-P were formed in the pea rhizosphere compared to the tomato rhizosphere and in the case of soluble P compared to the solid amendment. The increase in soil-metal contact time enhanced metal-P formation.

Conclusions

The different forms of metal-P formed for the different plants under two kinds of P amendments indicate that several mechanisms are involved in metal immobilization. Metal-P complex formation in the contaminated soil depends on the type of P amendment added, duration of soil-plant contact, type of plant species, and excretion of organic acids by the plant roots in the rhizosphere.     

The Diversity of Bacterial Communities in Urban Soils

Urbanozems (Urbic Technosols) contaminated by heavy metals and polychlorbiphenyls (Urbic Technosols Toxic) and intruzems (Urbic Technosols Toxic) were studied in Moscow; additionally, we studied recreazems (Urbic Technosols Thaptohumic) and culturozems (Urbic Technosols Pantohumic) on the territory of the Botanical Garden of Moscow State University (Aptekarskii Ogorod, the Apothecaries’ Garden). In the soils contaminated with heavy metals and oil products, the number of viable cells of bacteria decreased, whereas the content of filterable forms of bacteria increased. The taxonomic structure of saprotrophic bacterial complexes in contaminated urban soils was transformed towards an increase in the diversity of bacterial taxa atypical of natural undisturbed soils. Rhodococci (Rhodococcus genus) predominated in the soils contaminated with oil and polychlorbiphenyls, enterobacteria (Escherichia, Enterobacter, and Klebsiella genera) predominated in the soils contaminated with municipal wastes, and Arthrobacter genus was dominant in the soils contaminated with cement dust. Soils of both Botanical Gardens of Moscow State University were characterized by the high population density and specific distribution of bacteria in the profile; the structure of their saprotrophic bacterial complex had some similarity with that in the soils of more southern regions. The obtained data on the bacterial diversity of urban soils attest to considerable transformation of bacterial communities both in the contaminated urban soils and in the soils of botanical gardens.     

土法炼锌区大气沉降Pb、Zn、Cd及其对土壤质量的影响

Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Guizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible effects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn (508 mg kg-1), Pb (95.6 mg kg-1), and Cd (5.98 mg kg-1) with low ratios of Zn/Cd (59.1--115) and Pb/Cd (12.4--23.4). Composite pollution indices (CPIs) of surface soils (2.52--15.2) were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals (SDM) in soils within 1.5 km of the smelter (averaging 1.25) was six times higher than that of the reference soils (0.209). A smaller soil microbial biomass was found more frequently in metal accumulated soils (85.1--438 μg C g-1) than in reference soils (497 μg C g-1), and a negative correlation (P < 0.01) of soil microbial biomass carbon to organic carbon ratio (Cmic/Corg) with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM (R = -0.773, P < 0.01). Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and weredetrimental to soil quality mainly in respect of microbial biomass.     

Plant–soil interactions in metal contaminated soils

The legacy of industrialization has left many soils contaminated. However, soil organisms and plant communities can thrive in spite of metal contamination and, in some cases, metabolize and help in remediation. The responses of plants and soil organisms to contamination are mutually dependent and dynamic. Plant–soil feedbacks are central to the development of any terrestrial community; they are ongoing in both contaminated and healthy soils. However, the theory that governs plant–soil feedbacks in healthy soils needs to be studied in contaminated soils. In healthy soils, negative feedbacks (i.e. pathogens) play a central role in shaping plant community structure. However to our knowledge, the nature of feedback relationships has never been addressed in contaminated soils. Here we review literature that supports a plant–soil feedback approach to understanding the ecology of metal-contaminated soil. Further, we discuss the idea that within these soils, the role of positive as opposed to negative plant–soil feedbacks may be more important. Testing this idea in a rigorous way in any ecosystem is challenging, and metal contamination imposes an additional abiotic constraint. We discuss research goals and experimental approaches to study plant–soil interactions applicable to metal-contaminated soils; these insights can be extended to other contaminated environments and restoration efforts.     

Human health risk due to consumption of vegetables contaminated with carcinogenic polycyclic aromatic hydrocarbons

Purpose  

Polycyclic aromatic hydrocarbons (PAH) are persistent, toxic, and carcinogenic contaminants present in soil ecosystem globally. These pollutants are gradually accumulating in wastewater-irrigated soils and lead to the contamination of vegetables. Food chain contamination with PAH is considered as one of the major pathways for human exposure. This study was aimed to investigate the concentrations of PAH in soils and vegetables collected from wastewater-irrigated fields from metropolitan areas of Beijing, China. Origin of PAH, daily intake, and health risks of PAH through consumption of contaminated vegetables were studied.     

Spatiotemporal dynamics of the pollution of Al–Fe-humus podzols in the impact zone of a nonferrous metallurgical plant

The dependence of the level of contamination of the upper horizon of Al–Fe-humus podzols (Podzols Rustic) with heavy metals (Ni, Cu) on the distance from the Severonickel smelter (Monchegorsk, Murmansk oblast) was studied on a number of test plots in the medium-aged pine stands. It was found that metal concentrations in the soils could be reasonably approximated by the negative exponential function. In the buffer zone of the smelter, the concentrations of Ni and Cu exceed background values by 8–17 times; in the impact zone, by 50–100 times. The study of the dynamics of acid-soluble forms of Ni and Cu in the organic horizons of podzols on the key plots showed that the boundaries of polluted territory shift towards background regions despite the recent five–eightfold decrease in the emissions. The concentrations of heavy metals in the litter horizons continued to increase in the buffer zone. In the impact zone, their contamination remained at the very high level. Firm bounding of heavy metals in the organic horizon coupled with their continuing aerial input did not allow the beginning of the soil self-purification process, which might last for decades and centuries. Raster electron microscope and X-ray spectral microanalysis showed that particles (>85%) of the ashed matter of organic horizons from the background region, the buffer zone, and the impact zone is mainly represented by various soil-forming minerals and iron oxides (in particular, magnetite). In the samples from the impact zone, about 5% of the mineral particles had the surface morphology and chemical composition typical of dust particles emitted into the air by metal smelters. Most probably, these spherical particles represented magnetite Fe₃O₄ enriched in heavy metals (Cu, Ni).     

Myriapod and isopod communities in soils contaminated by heavy metals in northern France

Soil invertebrates suffer from contamination of the soil by heavy metals. We have studied the effects of contamination by cadmium, zinc and lead on their communities in soils in northern France by comparing polluted land with non‐contaminated sites. We have followed the seasonal variations and effects of soil properties. Saprophagous invertebrates (Diplopoda, Isopoda) and Chilopoda were sampled by pitfall‐trapping from February to November in fairly contaminated areas. In addition, a Berlese extraction of the litter in two very highly contaminated sites was conducted during autumn; animals were also trapped during June in the same locations. The most active period for myriapods was spring (April and May), whereas isopods were abundant from April to the end of summer. No clear relation was found relating dominant species or number of myriapods or isopods to concentration of heavy metal in the little‐contaminated soils. The dominant species seemed not to be related to pollution but to vegetation or soil characteristics. In the most contaminated sites, with metalliferous grassland and a thick undecomposed litter layer, a threshold in contamination values seemed to be reached: no isopods or millipedes were found, but only Chilopoda and Symphyla.     

Elemental characterization of plants and soils in Panasqueira tungsten mining region

Purpose

Mining activities represent a current source of pollution due to the large release of trace elements from mineral particles into the soil, atmosphere, and ecosystems. In active or abandoned metal-mining areas, direct discharge from mining deposits is one of the most common processes of contamination.

Materials and methods

In this work, we calculated the elemental concentrations of plants, edible for cattle, which might contain high values of toxic elements, such as As, Cu, Zn, and W, originated from mining exploitation, especially wolframite. Several species of plants originating from the same contaminated place, close to the mine, were the subject of our study in order to compare the uptake of harmful elements, from the contaminated soils, in the different plants. We have used the energy-dispersive X-ray fluorescence technique to perform the analysis and quantification of the elements present in the collected samples. The quantification was based on the fundamental parameters method for plants and on the WinAxil compare mode using a standard reference material, for soils. Calibration against a series of standard samples has been carried out.

Results and discussion

A comparison between contaminated and control samples, within the same species, was performed. The contamination of the two mining wash sites is assessed by comparing the elemental concentration of several plants in these places. Elemental content in soils was investigated, and a comparison between elemental levels in plants was performed.

Conclusions

High concentrations of tungsten were found near the new wash site. Arsenic was found throughout the area in concentrations many times higher than those recommended by the World Health Organization.     

Effects of heavy metal contamination and remediation on soil microbial communities in the vicinity of a zinc smelter as indicated by analysis of microbial community phospholipid fatty acid profiles

Heavy metal contamination in an area immediately surrounding a zinc smelter has resulted in destruction of over 485 hectares of forest. The elevated levels of heavy metals in these soils have had significant impacts on the population size and overall activity of the soil microbial communities. Remediation of these soils has resulted in increases in indicators of biological activity and viable population size, which suggest recovery of the microbial populations. Questions remain as to how the metal contamination and subsequent remediation at this site have impacted the population structure of the soil microbial communities. In the current study, microbial communities from this site were analyzed by the phospholipid fatty acid (PLFA) procedure. Principal component analysis of the PLFA profiles indicated that there were differences in the profiles for soils with different levels of metal contamination, and that soils with higher levels of metal contamination showed decreases in indicator PLFAs for mycorrhizal fungi, Gram-positive bacteria, fungi, and actinomycetes. PLFA profiles for remediated sites indicated that remediated soils showed increases in indicator PLFAs for fungi, actinomycetes, and Gram-positive bacteria, compared to unremediated metal contaminated soils. These data suggest a change in the population structure of the soil microbial communities resulting from metal contamination and a recovery of several microbial populations resulting from remediation.