Toxic Element Pollution Research Articles

Characteristics of potentially toxic elements and multi-isotope signatures (Cu, Zn, Pb) in non-exhaust traffic emission sources

Non-exhaust emissions (e.g., particles from brake pads, asphalt, curb, road paint, tire) are important sources of potentially toxic elements (PTEs) pollution in urban environments and are potential causes of PTEs pollution in road dust. We present the PTEs concentrations (Cr, Ni, Cu, Zn, As, Cd, Sn, Sb, Pb) of non-exhaust emission sources and pollution degree of PTEs. Isotopic signatures of Cu, Zn, and Pb were also analyzed to distinguish these sources. Among PTEs, the Cu concentration in all brake pads was significantly high and brake pads from Korea showed remarkably high Sb concentrations. Asphalt had a higher Pb concentration than other non-exhaust emission sources. Mean of δ65CuAE647, δ66ZnIRMM3702, and 206Pb/207Pb values of non-exhaust emission sources in this study ranged from −0.49‰ to +0.19‰, −0.24‰ to +0.16‰, and 1.1535 to 1.4471, respectively. Non-exhaust emission sources could be discriminated by plotting the concentration and isotopic composition of Cu. Cu isotopic compositions (δ65CuAE647) were clearly distinguished between brake pads including domestic and imported products and tires. Zn isotope values (δ66ZnIRMM3702) of brake pads, tires, and asphalt overlapped, but discriminated from road paint and curb. Our results indicate that the combination of Cu and Zn isotopic signatures can distinguish various non-exhaust traffic emissions, especially brake pads and tires.

Tracing the pollution and human risks of potentially toxic elements in agricultural area nearby the cyanide baths from an active private gold mine in Hainan Province, China.

Mining activities are well-known sources of potentially toxic elements (PTEs) pollution, which often jeopardize the biosphere, pedosphere, and hydrosphere. However, the soil and groundwater pollution caused by active private mining activities has long been neglected. This study investigated the occurrence of PTEs and cyanide (CN) in agricultural soils, mine tailings, and groundwater nearby the cyanide baths from a private gold mine in Hainan Province, southern China. Results indicated that concentrations of Pb, As, Cd, Hg, and CN in different soil depths and mine tailings were up to ten thousand mg/kg, and relatively higher content of As and Pb was detected in groundwater. The chemical forms of Cd, Pb, As, and Hg varied greatly in different soil depths; over 80% of Cd distributed in the water-soluble fraction, suggesting its higher mobility in soils, while approximately 60-90% of Pb, As, and Hg distributed in other chemical fractions, indicating relatively lower mobility in soils. The pollution indices also revealed the serious pollution and deterioration of site quality in this area. Human risk assessments also reflected a high non-carcinogenic/carcinogenic health risk in this area. The framework of integrated management strategies for private metal mines was proposed to mitigate PTEs pollution and reduce health risks.

Concentrations, spatial distribution, sources and environmental health risks of potentially toxic elements in urban road dust across China

Potentially toxic element (PTE) pollution is widespread in road dust across China, and the effects of PTEs in road dust on health cannot be ignored. In this study, the concentrations of six PTEs (Pb, Cd, Cr, Cu, Zn and Ni) in 4336 road dust samples from 58 cities in 31 provincial regions of China taken after 2000 were obtained from the literatures. Based on these data, the spatial distribution, pollution sources, and ecological and human health risks of PTEs in road dust were comprehensively assessed and the main pollution factors and areas of high risk were identified. The results revealed that PTE levels are generally higher in eastern cities than western cities in China. The key driving factors are socioeconomic factors, including those related to transportation, industry, and population, for which the contribution rates are 57.80%, 55.39% and 37.19%, respectively. PTEs in the road dust with high ecological risks are mainly distributed in the southeastern coastal areas and the Beijing-Tianjin-Hebei region. No obvious noncarcinogenic risk was found for PTEs in road dust, but Cd and Pb may have potential noncarcinogenic risk, mainly distributed in cities in western China. Therefore, regions and pollution sources contributing to Pb and Cd levels should be monitored. The control of PTE pollution in China is a priority for ecological and environmental protection.

Assessing toxic metal chromium in the soil in coal mining areas via proximal sensing: Prerequisites for land rehabilitation and sustainable development

The rapid and accurate determination of soil chromium (Cr) is crucial for preventing toxic element pollution in soils and ensuring ecological security. Proximal sensing technology uses visible and near-infrared (Vis-NIR) diffuse reflectance spectroscopy, which has been demonstrated to be a viable approach for monitoring soil Cr concentrations. However, at trace levels, soil Cr is not especially spectrally active, thus limiting the practical application of using corresponding spectral data for quantifying soil Cr concentrations. In this study, we hypothesized that fused proximal sensing and soil auxiliary attributes (including organic matter (OM) and pH) could improve estimation of Cr concentrations in the soil. Additionally, the introduction of best-fit variogram models was theoretically possible to improve spatial visualization. To address these hypotheses, we collected 168 soil samples from the open coal mine area in the Eastern Junggar Basin, China. Fractional-order derivative (FOD) pretreatment and optimal band combination methods were implemented for spectral data mining and the derivation of spectral parameters, respectively. Soil Cr estimation models were calibrated with a partial least squares (PLS) approach through four designed strategies with different predictors: (I) full Vis-NIR variables, (II) effective three-band spectral indices (TBIs), (III) the effective TBIs and OM, and (IV) the effective TBIs, OM, and the pH. The results suggest that FOD could identify abundant spectral variability. Compared with full Vis-NIR variables, the effective TBIs can effectively magnify the subtle spectral signals concerning soil Cr. The optimal estimation model was determined as Strategy IV, indicating that the introduction of soil auxiliary attributes (pH and OM) can improve the estimation performance of the model; notably, the coefficient of determination (R2) and ratio of performance to interquartile distance (RPIQ) were 0.87 and 2.68, respectively. Based on the optimal semivariance model, we used kriging interpolation to map regional soil Cr. In the study area, the soil Cr distribution features strong spatial dependence and strong associations. Our study might inspire further research on soil contamination mapping based on proximal Vis-NIR sensors.

Investigating microplastics and potentially toxic elements contamination in canned Tuna, Salmon, and Sardine fishes from Taif markets, KSA.

Microplastics (MPs) have been documented in different foodstuffs and beverages, that could affect human health due to their ingestion. Furthermore, seafood contamination with MPs puts pillars of food availability and utilization at risk. The present study investigates MPs and toxic elements pollution in commercially canned fishes from Taif governorate markets. Seven different canned fishes’ brands were used in the present study from different manufacturer countries and purchased from Taif markets. Tissue samples were digested by 10% of KOH; then, dry filters were analyzed by Fourier-transform infrared spectroscopy to detect MPs. Filtrates were used to detect any potentially toxic elements by inductively coupled plasma. Different MPs were detected in edible tissue, such as canned Tuna contaminated with nylon, 1,2-polybutadiene, and ethylene vinyl alcohol. Sardines contain ethylene vinyl alcohol and poly(vinyl stearate), but Salmon does not have any MPs. Different elements were present in the selected samples in the decreasing order of Al > Se > Zn and traces of As and Sb. Canned fishes were contaminated with MPs and potentially toxic elements. This contamination could be a warning of the potential health risks with the long-term exposure. Therefore, it is recommended to include micro-, meso-, and even nanoplastics in the guidelines of testing food safety management systems.

Optimal spatial sampling design for monitoring potentially toxic elements pollution on urban green space soil: A spatial simulated annealing and k-means integrated approach

Sampling design in soil science is critical because the lack of reliable methods and collecting samples requires tremendous work and resources. The aims were to obtain an optimal sampling design for assessing potentially toxic elements pollution using pilot Pb soil samples from the urban green space area of Shanghai, China. Two general steps have been used. The first step is to determine the optimum sample size against improving the prediction accuracy and monitoring costs using the spatial simulated annealing (SSA) algorithm. Secondly, we evaluated their likely placement of new extra sampling points by integrated SSA with k-means (SSA+ k-means) and expert-based (SSA+ expert-based) sampling methods. The improvement of sampling design by the integrated sampling approaches was evaluated using mean kriging variance (MKV), root mean square error (RMSE), and mean absolute percentage error (MAPE). The findings indicated that adding and placing 350 new monitoring points upon the existing sampling design by SSA increased the prediction accuracy by 64.35%. The MKV for the optimized SSA+ k-means sample was lower than by 4.12 mg/kg, 9.46 mg/kg compared with locations optimized by SSA and SSA+ expert-based method, respectively. Optimizing new sampling locations by SSA+ k-means sampling method was reduced MAPE by 9.26% and RMSE by 7.13 mg/kg compared to optimizing by SSA alone. However, there was no improvement in placing the new sampling points in SSA+ expert-based sampling method; instead, it increased the error by 8.11%. This paper shows integrating optimization approaches to evaluate the existing sampling design and optimize a new optimal sampling design.

Multi-level methods to quantify risk assessment, source apportionment and identifying key risk areas of soil toxic elements in Ashi River watershed, China

With the advancement of small watershed governance in agricultural production process, soil toxic element pollution issue in watersheds constitutes a recent research hot spot. The Ashi River watershed is an agriculture-dominated small watershed which is exposed to toxic element sources, posing high risk of toxic element pollution to the planting areas. In this study, collection of soil samples was carried out along the periphery of the river network, and the soil physicochemical parameters and toxic elements (As, Cd, Cr, Cu, Pb, and Zn) were analyzed. The results showed that: (1) The geo-accumulation index (Igeo) and potential ecological risk index were used to evaluate the pollution degree, and the contents of As, Cd, and Zn in some sampling sites exceeded risk screening values. Moreover, soils closer to mining sources were found to be more polluted; (2) Redundancy analysis confirmed the contribution rate relationship between environmental factors and toxic elements. C/N ratio, total carbon (C), and total potassium (K) exhibited significant relationships with toxic elements (P < 0.01 or P < 0.05), respectively. Moreover, geographic locations (longitude, latitude, and elevation) showed significant impacts on toxic element contents (except for Cu); (3) The apportionment of toxic element pollution sources by using principal component analysis showed that Pb, Zn, Cu, and Cd were mainly related to mining activities, while As was closely related to insecticide and herbicide, and Cr was mainly related to soil parent material and electroplating factory; (4) Through the integrated resistance base surface and toxic element sources combined with minimum cumulative resistance model, the toxic element risk areas were identified. The middle reaches corresponded to the extremely high risk zone, which undeniably requires the strengthening of the environmental management.

Sources of and Control Measures for PTE Pollution in Soil at the Urban Fringe in Weinan, China

The environment of the urban fringe is complex and frangible. With the acceleration of industrialization and urbanization, the urban fringe has become the primary space for urban expansion, and the intense human activities create a high risk of potentially toxic element (PTE) pollution in the soil. In this study, 138 surface soil samples were collected from a region undergoing rapid urbanization and construction—Weinan, China. Concentrations of As, Pb, Cr, Cu, and Ni (Inductively Coupled Plasma Mass Spectrometry, ICP-MS) and Hg (Atomic Fluorescence Spectrometry, AFS) were measured. The Kriging interpolation method was used to create a visualization of the spatial distribution characteristics and to analyze the pollution sources of PTEs in the soil. The pollution status of PTEs in the soil was evaluated using the national environmental quality standards for soils in different types of land use. The results show that the content range of As fluctuated a small amount and the coefficient of variation is small and mainly comes from natural soil formation. The content of Cr, Cu, and Ni around the automobile repair factory, the prefabrication factory, and the building material factory increased due to the deposition of wear particles in the soil. A total of 13.99% of the land in the study area had Hg pollution, which was mainly distributed on category 1 development land and farmland. Chemical plants were the main pollution sources. The study area should strictly control the industrial pollution emissions, regulate the agricultural production, adjust the land use planning, and reduce the impact of pollution on human beings. Furthermore, we make targeted remediation suggestions for each specific land use type. These results are of theoretical significance, will be of practical value for the control of PTEs in soil, and will provide ecological environmental protection in the urban fringe throughout the urbanization process.

Predicting Bioaccumulation of Potentially Toxic Element in Soil–Rice Systems Using Multi-Source Data and Machine Learning Methods: A Case Study of an Industrial City in Southeast China

Potentially toxic element (PTE) pollution in farmland soils and crops is a serious cause of concern in China. To analyze the bioaccumulation characteristics of chromium (Cr), zinc (Zn), copper (Cu), and nickel (Ni) in soil-rice systems, 911 pairs of top soil (0–0.2 m) and rice samples were collected from an industrial city in Southeast China. Multiple linear regression (MLR), support vector machines (SVM), random forest (RF), and Cubist were employed to construct models to predict the bioaccumulation coefficient (BAC) of PTEs in soil–rice systems and determine the potential dominators for PTE transfer from soil to rice grains. Cr, Cu, Zn, and Ni contents in soil of the survey region were higher than corresponding background contents in China. The mean Ni content of rice grains exceeded the national permissible limit, whereas the concentrations of Cr, Cu, and Zn were lower than their thresholds. The BAC of PTEs kept the sequence of Zn (0.219) &gt; Cu (0.093) &gt; Ni (0.032) &gt; Cr (0.018). Of the four algorithms employed to estimate the bioaccumulation of Cr, Cu, Zn, and Ni in soil–rice systems, RF exhibited the best performance, with coefficient of determination (R2) ranging from 0.58 to 0.79 and root mean square error (RMSE) ranging from 0.03 to 0.04 mg kg−1. Total PTE concentration in soil, cation exchange capacity (CEC), and annual average precipitation were identified as top 3 dominators influencing PTE transfer from soil to rice grains. This study confirmed the feasibility and advantages of machine learning methods especially RF for estimating PTE accumulation in soil–rice systems, when compared with traditional statistical methods, such as MLR. Our study provides new tools for analyzing the transfer of PTEs from soil to rice, and can help decision-makers in developing more efficient policies for regulating PTE pollution in soil and crops, and reducing the corresponding health risks.

Potentially toxic trace element pollution in long-term fertilized agricultural soils in China: A meta-analysis

Fertilization results in potentially toxic trace element (PTTE) pollution in agricultural soils. However, it is unclear which factors determine the effect sizes of fertilization on PTTEs at the multiple spatial-temporal scale. This work synthesized 379 observations in 78 field sites (3–35 years) across China's main grain producing areas, and showed that long-term organic fertilization significantly enhanced total Cu, Zn and Cd by 25.7%, 18.9% and 66.6%, and soil available Cu, Zn and Cd by 60.5%, 155.3% and 83.6%, respectively; whereas long-term inorganic fertilization increased only available Cu, Zn and Cd by an average of 6.3%. Organic fertilizer (OF) type and application rate dominated the variation of PTTE concentrations, where approximately one-half of Cd pollution (42.6% of total Cd and 47% of available Cd) was observed. Furthermore, OFs containing Cd less than 1 mg kg−1 were recommended to be safely applied to agricultural soils. Soil type was main factor under long-term inorganic fertilization determining available PTTE variation, resulted in higher pollution risk in some soils such as Alfisols and Semi-hydromorphic soils, where we suggested the use of lower amounts of P fertilizers or the application of ones having small amounts of PTTEs. In short, long-term organic fertilization caused serious pollution of PTTEs especially Cd in Chinese croplands, and some strategies with a focus towards reducing the pollution risk must be developed, e.g., promoting straw return, forbidding Cd addition to feeds and feed additives, and improving carbon sequestration efficiency (CSE) of OFs and thus soil organic matter (SOM).

Source-specific ecological and health risks of potentially toxic elements in agricultural soils in Southern Yunnan Province and associated uncertainty analysis

Source-specific risk apportionment is critical to prevent and control soil potentially toxic element (PTE) pollution. This study explored source-specific ecological and human health risks of soil PTEs in Southern Yunnan Province. Geochemical baseline values were determined to assess the pollution level of PTEs; then source-specific risk was apportioned combining positive matrix factorization (PMF) with ecological and human health risk assessment. Obvious accumulation of As, Cd, Pb, and Zn was observed in this area, especially Cd in 21.33% of the samples exhibited significant enrichment. Four sources were quantified based on PMF assisted with GIS-mapping: natural sources (41.49%), traffic emissions (24.70%), industrial activities (17.48%), and agricultural activities (16.33%). Industrial activities were the largest source (64.55%) to ecological risk. Agricultural activities were regarded as the major contributor to non-carcinogenic (adults: 75.93%, children: 62.33%) and carcinogenic risks (adults: 55.97%, children: 56.36%). Non-carcinogenic and carcinogenic risks for children were higher than adults, and their health risks showed similar trend. Thus, agricultural activities should be regarded as a priority to reduce health risk, whereas industrial activities should be given priority to control ecological risk. Although source-specific risk was quantified, combination with bioavailability and interactions of PTEs are necessary to obtain more accurate results in future.

Global soil pollution by toxic elements: Current status and future perspectives on the risk assessment and remediation strategies – A review

The aim of this article is to review and present the state of the arte about the status of toxic elements (TEs) in soils and assess the potential risk using single and total complex pollution indices in a global scale. We compiled, integrated, and analyzed soil TE pollution data over almost a decade through key maps, which have not been reviewed up to date. All the in-situ and ex-situ remediation treatments have been also reviewed, illustrated, and compared, for the first time. The future perspectives have been discussed and summarized. This review demonstrates that the cornerstone maps and integrated information provide reliable geographical coordinates and inclusive information on TEs pollution, particularly in China. In-situ treatment approaches for TEs polluted soils are more cost-effective and applicable than ex-situ treatment trials. Selecting a feasible remediation strategy should to take the extent of contamination, treatment objectives, site characteristics, cost-efficiency, and public suitability into account. The summarized findings in this review may help to develop innovative and applicable methods for assessing the global soil pollution by TEs. Also, these findings may help to develop innovative, applicable, and feasibly economic methods for sustainable management of TEs contaminated soils to mitigate the environmental and human health risk.

Removal Mechanisms of Slag against Potentially Toxic Elements in Soil and Plants for Sustainable Agriculture Development: A Critical Review

Potentially toxic element (PTE) pollution is a major abiotic stress, which reduces plant growth and affects food quality by entering the food chain, and ultimately poses hazards to human health. Currently, the use of slag in PTE-contaminated soils has been reported to reduce PTEs and toxicity in plants. This review highlights the role of slag used as a fertilizer for better crop production and sustainable agricultural development. The application of slag increased the growth, yield, and quality of crops under PTE toxicity. The mechanisms followed by slag are the immobilization of PTEs in the soil, enhancement of soil pH, changes in the redox state of PTEs, and positive changes in soil physicochemical and biological properties under PTE toxicity. Nevertheless, these processes are influenced by the plant species, growth conditions, imposition length of stress, and type of slag used. The current review provides an insight into improving plant tolerance to PTE toxicity by slag-based fertilizer application and highlights the theoretical basis for applying slag in PTE-contaminated environments worldwide.

Potentially toxic elements pollution in road deposited sediments around the active smelting industry of Korea

Potentially toxic elements (PTEs) were investigated in the different sizes of road deposited sediments (RDS) around the active smelting industry to understand their sources and to assess the pollution and ecological risk levels. The highest PTEs concentrations was shown near the raw materials import port and the smelting facilities. The fine particles of RDS showed extremely high PTEs concentrations. Zn has the highest mean concentration in the < 63 μm particle size of RDS, followed by Pb > Cu > As > Cr > Ni > Cd > Hg. The PTEs concentrations of this study were the highest values compared to the soils around the smelter and the RDS in urban and industrial areas in the world. This indicates that these PTEs pollution in RDS were mainly attributed to the transportation of raw materials for the smelting industry. According to nemerow pollution index calculation, RDS at all sampling sites with particles of less than 250 mm was seriously polluted with PTEs. The ecological risk was also found to be very high in all RDS fractions and highly toxic elements such as Cd, Pb and Hg pose extremely risk. Given the total amounts PTEs in the road surface, it is necessary to apply RDS removal management plan to reduce the PTEs pollution.

Phytoremediation of potentially toxic elements in a polluted industrial soil using Poinsettia

Potentially toxic elements (PTEs) pollution has become a serious environmental threat, particularly in developing countries such as China. In response, there is a growing interest in phytoremediation studies to identify plant species as designated hyperaccumulators of PTEs in polluted soils. Poinsettia was selected as a candidate species for phytoremediation of six PTEs (Zn, Pb, Hg, Cr, As, Cu) in this study. A pot cultivation experiment (randomized incomplete block experimental design with 5 treatments and 4 blocks) was conducted using contaminated soils gathered from an industrial area in southcentral China. The bioaccumulation factor (BAF), translocation factor (TF), and bioconcentration factor were analyzed to determine the phytoremediation potential of poinsettia potted in different ratios of polluted soils. One-way ANOVA with post-hoc Tukey’s test showed that poinsettia had significant uptake of Zn, Pb, Cu (BAF < 1 and TF < 1, p < 0.05) and Hg (BAF < 1 and TF > 1, p < 0.05). Poinsettias can therefore effectively accumulate Zn, Pb, and Cu in their lateral roots while extracting and transferring Hg into their leaves. Moreover, poinsettia exhibited tolerance towards As and Cr. Interestingly, it was also observed that PTEs can inhibit the height of potted poinsettia at a certain concentration.

Current Status and Temporal Trend of Potentially Toxic Elements Pollution in Agricultural Soil in the Yangtze River Delta Region: A Meta-Analysis.

Potentially toxic elements (PTEs) pollution in the agricultural soil of China, especially in developed regions such as the Yangtze River Delta (YRD) in eastern China, has received increasing attention. However, there are few studies on the long-term assessment of soil pollution by PTEs over large regions. Therefore, in this study, a meta-analysis was conducted to evaluate the current state and temporal trend of PTEs pollution in the agricultural land of the Yangtze River Delta. Based on a review of 118 studies published between 1993 and 2020, the average concentrations of Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni were found to be 0.25 mg kg−1, 0.14 mg kg−1, 8.14 mg kg−1, 32.32 mg kg−1, 68.84 mg kg−1, 32.58 mg kg−1, 92.35 mg kg−1, and 29.30 mg kg−1, respectively. Among these elements, only Cd and Hg showed significant accumulation compared with their background values. The eastern Yangtze River Delta showed a relatively high ecological risk due to intensive industrial activities. The contents of Cd, Pb, and Zn in soil showed an increasing trend from 1993 to 2000 and then showed a decreasing trend. The results obtained from this study will provide guidance for the prevention and control of soil pollution in the Yangtze River Delta.

Assessment of potentially toxic element pollution in soils and related health risks in 271 cities across China

Potentially toxic element (PTE) pollution has been extensively studied at a local and regional scale in China. However, further research needs to be conducted at a national level. To this end, in current study we systematically compiled data of around 170,000 soil samples collected from 1153 papers published between 2008 and 2018. Based on these data we conducted a comprehensive analysis on the pollution status, pollution hotspots, and potential dominant sources of PTEs (As, Cd, Cr, Cu, Hg, Pb, Ni and Zn) in soils in 271 cities of China using geochemical accumulation index, potential ecological risk index, health risk evaluation model, univariate local Moran’s I index, and bivariate local Moran’s I index. Our results indicated an obvious accumulation of PTEs in the soils of most cities. In addition, the contents of Cd, Hg, Pb, and Ni were higher in China when compared to other several countries under comparison. Pollution hotspots of PTE and hotspots of human health risks may occur due to PTE exposure were mainly distributed in South (S) and Southwest (SW) of China. Cities with PTEs accumulation in soil due to industrial activities were mainly located in East (E) and North (N) China. Cities that had high concentrations of PTE due to agricultural activities were mainly located in central and Northeast (NE) China. Most cities with an accumulation of PTEs in soils primarily due to mining activities were found in West (W) and Northwest (N) China. Cities with PTEs mainly sourced from soil parental material were distributed in Southwest (SW) China. This study provides comprehensive and specific information and valuable implications for developing advanced scientific and efficient strategies to prevent and control PTE pollution the soils in China.

Source apportionment and spatial distribution of potentially toxic elements in soils: A new exploration on receptor and geostatistical models

Potentially toxic element (PTE) pollution is considered as the main soil environmental problem in the world. Source apportionment and spatial pattern of soil PTEs are essential for soil management. US-EPA positive matrix factorization (EPAPMF) and sequential Gaussian simulation (SGS) are general modeling tools for source apportionment and spatial distribution, respectively. Factor analysis with nonnegative constraints (FA-NNC) and stochastic partial derivative equations (SPDE) provided potential tools for this issue. We compared the performance of FA-NNC with PMF and the performance of SPDE with SGS, based on a dataset containing 9 PTEs in 285 topsoil samples. Three factors were determined by the two receptor models, and the source contributions were similar, suggesting that FA-NNC can validly identify quantitative sources of soil PTEs. The average source contributions were calculated based on the PMF and FA-NNC. Natural sources dominated the contents of As, Co, Cr, Cu, Ni, and Zn and affected 56.0%, 38.7%, and 84.8% of the Cd, Hg, and Pb concentrations, respectively. A total of 59.8% of Hg and 12.0% of Pb were associated with atmospheric deposition from coal combustion, industrial and traffic emissions, respectively. Agricultural and industrial activities contributed 37.2% of Cd concentration. SPDE proved to be an effective geostatistical technique to simulate the spatial patterns of soil PTEs with higher prediction accuracy than SGS. Co, Cr, Cu, and Ni had similar spatial patterns with hotspots randomly distributed across the study area. The common hotspots of As, Cd, Hg, Pb, and Zn in central parts inherited their high geochemical background in mudstone, while intensive human inputs in these areas also contributed to the accumulation of Cd, Hg, and Pb.

Fuzzy health risk assessment and integrated management of toxic elements exposure through soil-vegetables-farmer pathway near urban industrial complexes

Urban industrial areas were being built globally, which decreased key geographical separation between agriculture and industrial areas, especially in developing countries. Now, limited studies concerned coordinated the vegetables and soil management for toxic elements (TEs) in this mixed land system. To fill this gap, an integrated environmental multi-media risk management method was explored based on laboratory analysis, health risk assessment, uncertainty control, and source apportionment. The Chinese Beihu area of Wuhan City was selected as a typical case and the measurements of Zn, Cr, Cu, Pb, As, and Cd in soil revealed that TEs pollution was slight and concentrations met the Chinese standards. Meanwhile, some vegetables exceeded corresponding standard limits. To further quantify negative health effects posed by the studied TEs both in soils and vegetables, an established fuzzy health risk assessment for farmers was employed and the results indicated that the soil exposure of As and the vegetable consumption needed the priority control. The carcinogenic risk (CR) of As in soil was [4.60E-6, 1.45E-5] and the cumulative CR (sum of CRAs, CRPb and CRCd) in leafy vegetables was [1.08E-4, 1.38E-4], which was higher than that of the other vegetables. Preventing soil oral exposure and reducing self-grown vegetable consumption (30%–50%) were proven as effective risk interventions via uncertainty control methods. Spatially, the risk grades under maximum membership principle decreased from south to north in the Beihu area, and the south area was identified as the priority control area. Source apportionment identified four source patterns (Zn-Cr-Cu, Pb, As, and Cd) for soil, and the probable bioaccumulation mechanisms for leafy vegetables by multivariate statistical analyses. Finally, the integrated management strategies were formulated from perspectives of the risk sources, exposure pathways and the scenario.

The influence of long-term Zn and Cu contamination in Spolic Technosols on water-soluble organic matter and soil biological activity

Potentially toxic elements (PTE) pollution has a pronounced negative effect on the soil and its components. The characteristics of soil organic matter and the activity of soil enzymes can serve as sensitive indicators of the degree of changes occurring in the soil. This study aims to assess the effect of long-term severe soil contamination with Zn and Cu on water-soluble organic matter (WSOM) and the associated changes in the biochemical activity of microorganisms. The total content of Zn and Cu in the studied soils varies greatly: Zn from 118 to 65,311 mg/kg, Cu from 52 to 437 mg/kg. The content of WSOM was determined using cold and hot extraction. It was revealed that the WSOM, extracted with cold water is a sensitive indicator reflecting the nature of the interaction of Zn and Cu with it. With an increase in the Cu and Zn content, the amount of WSOM extracted with cold water increases due to rise in the complex-bound metal compounds associated with it. The content of complex-bound compounds Zn in Spolic Technosols reaches 50% of the total metal content. It is shown that one of the biogeochemical mechanisms of microorganisms' adaptation to metal contamination is clearly manifested by the increase in the content of WSOM. The precipitation of metal carbonates develops in the soil which reduces the mobility and toxicity of PTE. Due to this mechanism, a decrease in the activity of dehydrogenases and urease was not prominent in all studied soils, despite the very high level of pollution and the transformation of organic matter. The study of the relationship of PTE with the most easily transformed part of WSOM and the activity of soil enzymes is of great importance for an objective assessment of possible environmental risks.