Potentially Toxic Elements In Soils Research Articles

Health Risk Assessment for Potential Toxic Elements in the Soil and Rice of Typical Paddy Fields in Henan Province

The accumulation of potential toxic elements in agricultural soil and rice is of particular concern in China. However, studies on the risk assessment of these elements in regional soil–rice systems remain limited. The aim of this study is to evaluate the pollution status and potential health risk of potential toxic elements in typical paddy soil and rice in Henan Province. A total of 80 soil samples and corresponding rice samples were collected to determine the contents of Cd, Pb, As, Cr, Cu, Zn, and Ni, and to assess their potential health risks to local consumers. Results showed that the average contents of these elements in soils were below the national risk screening values in GB15618-2018. Only the average content of Cr in rice exceeded the limit in GB 2762-2022 specified by the national food safety standard. The rates of exceeding the limits for Cd, Pb, As, and Cr in rice samples were 13.89%, 15.28%, 15.28%, and 27.78%, respectively. The health risk assessment indicated that rice intake for both adults and children caused carcinogenic and non-carcinogenic health risks to varying degrees. Local residents are advised to purchase rice from outside the study area to meet their daily needs and strictly regulate the pollution of potential toxic elements within the area.

Improved X-ray fluorescence spectroscopic monitoring of potentially toxic elements by multivariate analysis: A case study of soils near abandoned coal mines (NW Portugal)

Reusing soils near abandoned mines requires the assessment of soil quality, which includes determining potentially toxic elements (PTEs), such as As, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Sr, Zn and Zr. Levels of PTEs in soil can be harmful. Hence, the measurement of their concentrations is crucial to assess whether soil properties are reusable or it represents a potential environmental risk. Field techniques such as X-ray fluorescence (XRF) imprinting may be an option for rapid PTEs monitoring. Still, due to low sensitivity and selectivity, the partially obtained results by XRF software can be biased. This study presents an alternative solution for soil PTEs monitoring based on the advantages of multivariate analysis (MVA) principally partial least square (PLS) regression applied to orthogonally signal-corrected (OSC) XRF spectroscopic data. The developed PLS models were applied to soil samples from two regions of adjacent abandoned coal mines, in NW Portugal. High correlation coefficients obtained for As, Fe, Pb, Sr and Zn validation models (R2 = 0.79–0.99) pointed to the improved accuracy of their monitoring (compared to directly obtained XRF results) in this regional soil environment. The other PTEs (Co, Cr, Cu, Ni and Zr) showed good PLS models at local environment (R2 = 0.84–0.98). The test of these models in the contaminated regions reinforces their effectiveness in monitoring contaminated soils toward the reuse of environments near abandoned mines.

Assessment of potential toxic elements in soils, sediments, and vegetation in the surroundings of Anapa, Russia.

The study presented here reports the concentration of major, trace, and rare earth elements in soil, sediments, and vegetation samples collected from 13 locations around Anapa City located on the northern coast of the Black Sea in Russia. The neutron activation analysis technique has been used to fulfill this objective. Along with this, the bioconcentration and translocation factors were calculated. Overall, the content of 31 elements was detected in soil and sediments while 20 elements were determined in three types of vegetation: macroalgae (Cystoseira sp. and Ulva sp.), aquatic plants (Phragmites australis), and sea grass (Zostera sp.). The quantified concentration followed the order soil > sediment > vegetation. The phytotoxic levels for Zn, V, Mn, and Fe have been quantified as the highest. Bromine was the most abundant and accumulated in Phragmites australis. Based on the results obtained from this investigation, there is a possibility of contamination in the study area.

Assessing soil contamination by potentially toxic elements in artisanal and small-scale gold mining sites of the Adamawa Region, Cameroon

Gold mining is acknowledged as a principal source of environmental contamination, primarily due to the release of potentially toxic elements (PTEs) through tailings dispersion into adjacent soils. Such contamination leads to land degradation, pollution, biodiversity loss and soil contamination, and subsequently impacts the food chain, human health and soil ecosystems. This study evaluates the extent of PTE contamination in soils at artisanal and small-scale gold mining (ASGM) sites within the Meiganga area of the Adamawa-Yade Domain, Cameroon. ASGM extraction processes from quartz veins in this area involve the removal of topsoil to access the ore. Comparative analysis of soil samples from three profiles within the mining zone were conducted to determine contamination levels using pollution indices: enrichment factor, geoaccumulation index, contamination factor and pollution load index. Results indicate higher concentrations of PTEs in soils from the mining area compared to the control profile, with notable contamination in the bottom slope profiles and B horizons, reflecting considerable metal accumulation. The contamination levels of PTEs substantially exceed background levels in the upper continental crust. The study attributes the elevated concentrations of PTEs not only to local mineralization but also to anthropic activities, particularly ASGM, which contributes to their enrichment, distribution and mobility. This pronounced contamination necessitates immediate intervention, advocating for pollution-control measures to address potential ecosystem and human health risks. It highlights the environmental toll of ASGM and underscores the imperative for sustainable mining practices and effective soil remediation techniques, including phytoremediation and soil replacement, to alleviate the adverse effects.

Bayesian multivariate receptor model and convolutional neural network to identify quantitative sources and spatial distributions of potentially toxic elements in soils: A case study in Qingzhou City, China

Determining sources and spatial distributions of potentially toxic elements (PTEs) is a crucial issue of soil pollution survey. However, uncertainty estimation for source contributions remains lack, and accurate spatial prediction is still challenging. Robust Bayesian multivariate receptor model (RBMRM) was applied to the soil dataset of Qingzhou City (8 PTEs in 429 samples), to calculate source contributions with uncertainties. Multi-task convolutional neural network (MTCNN) was proposed to predict spatial distributions of soil PTEs. RBMRM afforded three sources, consistent with US-EPA positive matrix factorization. Natural source dominated As, Cr, Cu, and Ni contents (78.5 %∼86.1 %), and contributed 37.1 %, 61.0 %, and 65.9 % of Cd, Pb, and Zn, exhibiting low uncertainties with uncertainty index (UI) < 26.7 %. Industrial, traffic, and agricultural sources had significant influences on Cd, Pb, and Zn (30.2 %∼61.9 %), with UI < 39.3 %. Hg originated dominantly from atmosphere deposition (99.1 %), with relatively high uncertainties (UI=87.7 %). MTCNN acquired satisfactory accuracies, with R2 of 0.357–0.896 and nRMSE of 0.092–0.366. Spatial distributions of As, Cd, Cr, Cu, Ni, Pb, and Zn were influenced by parent materials. Cd, Hg, Pb, and Zn showed significant hotspot in urban area. This work conducted a new approach exploration, and practical implications for soil pollution regulation were proposed.

Potential of Castanea sativa for biomonitoring As, Hg, Pb, and Tl: A focus on their distribution in plant tissues from a former mining district

Bioavailability of potentially toxic elements (PTEs) from the Earth's crust in the soil, e.g., As, Hg, Tl, and Pb, can pose a potential environmental and health risk because of human activities, especially related to mining extraction. The biomonitoring allows to detect PTE contamination through their measurement in living organisms as trees. However, the choice of which plant species and tissue to analyse is a key point to be evaluated in relation to PTE absorption and translocation. The aim of this work was to assess the As, Hg, Tl, and Pb distribution in Castanea sativa Mill. plant tissues, given its importance for both biomass and food production. The study identified two sites in the Alpi Apuane (Italy), with similar environmental conditions (e.g., elevation, exposure, forest type, and tree species) but different soil PTE levels. The topsoil was characterized, and the PTE fractions with different bioavailability were measured. The PTE concentrations were also analysed in chestnut plant tissues (leaves, bark, wood, nuts, and shells) in parallel with and evaluation of plant health status through the determination of micro and macronutrient concentrations and the leaf C and N isotope composition (δ13C or δ15N). Chestnut trees showed a good health status highlighting its suitability for Tl, As, Hg, and Pb biomonitoring, displaying a tissue-specific PTE allocation. Thallium and Hg were detected in all plant tissues at similar concentrations, As was found in leaves, wood, and nuts while Pb only in the bark. The δ15N negatively correlated with leaf Mn and Tl concentrations, suggesting possible changes in N source and/or plant metabolism due to the high contamination level and acid soil pH. Thallium in La Culla site trees was associated with its presence in the carbonate rocks but not in the topsoil, highlighting the potentiality of chestnut in providing valuable information for geochemical surveying.

Integrating waste valorization and symbiotic microorganisms for sustainable bioremediation of metal(loid)-polluted soils

Remediation strategies for metal(loid)-polluted soils vary among the wide range of approaches, including physical, chemical, and biological remediation, or combinations of these. In this study, we assessed the effectiveness of a set of soil remediation treatments based on the combined application of inorganic (marble sludge) and organic amendments (vermicompost, and dry olive residue [DOR] biotransformed by the saprobic fungi Coriolopsis rigida and Coprinellus radians) and inoculation with arbuscular mycorrhizal fungi (AMFs) (Rhizophagus irregularis and Rhizoglomus custos). The treatments were applied under greenhouse conditions to soil residually polluted by potentially toxic elements (PTEs) (Pb, As, Zn, Cu, Cd, and Sb), and wheat was grown in the amended soils to test the effectiveness of the treatments in reducing soil toxicity and improving soil conditions and plant performance. Therefore, we evaluated the influence of the treatments on the main soil properties and microbial activities, as well as on PTE availability and bioaccumulation in wheat plants. Overall, the results showed a positive influence of all treatments on the main soil properties. Treatments consisting of a combination of marble and organic amendments, especially biotransformed DOR amendments, showed the greatest effectiveness in improving the soil biological status, promoting plant growth and survival, and reducing PTE availability and plant uptake. Furthermore, AMF inoculation further enhanced the efficacy of DOR amendments by promoting the immobilization of PTEs in soil and stimulating the phytostabilization mechanisms induced by AMFs, thus playing an important bioprotective role in plants. Therefore, our results highlight that biotransformed DOR may represent an efficient product for use as a soil organic amendment when remediating metal(loid)-polluted soils, and that its application in combination with AMFs may represent a promising sustainable bioremediation strategy for recovering soil functions and reducing toxicity in polluted areas.

Integrated framework to assess soil potentially toxic element contamination through 3D pollution analysis in a typical mining city

Soil potentially toxic elements (PTEs) pollution of contaminated sites has become a global environmental issue. However, given that previous studies mostly focused on pollution assessment in surface soils, the current status and environmental risks of potentially toxic elements in deeper soils remain unclear. The present study aims to cognize distribution characteristics and spatial autocorrelation, pollution levels, and risk assessment in a stereoscopic environment for soil PTEs through 3D visualization techniques. Pollution levels were assessed in an integrated manner by combining the geoaccumulation index (Igeo), the integrated influence index of soil quality (IICQs), and potential ecological hazard index. Results showed that soil environment at the site was seriously threatened by PTEs, and Cu and Cd were ubiquitous and the predominant pollutants in the study area. The stratigraphic models and pollution plume simulation revealed that pollutants show a decreasing trend with the deepening of the soil layer. The ranking of contamination soil volume is as follows: Cu > Cd > Zn > As > Pb > Cr > Ni. According to the IICQs evaluation, this region was subject to multiple PTE contamination, with more than 60% of the area becoming seriously and highly polluted. In addition, the ecological hazard model revealed the existence of substantial ecological hazards in the soils of the site. The integrated potential ecological risk index (RI) indicated that 45.7%, 10.13%, and 4.15% of the stereoscopic areas were in considerable, high, and very high risks, respectively. The findings could be used as a theoretical reference for applying multiple methods to integrate evaluation through 3D visualization analysis in the assessment and remediation of PTE-contaminated soils.

Source identification and driving factor apportionment for soil potentially toxic elements via combining APCS-MLR, UNMIX, PMF and GDM

The contamination and quantification of soil potentially toxic elements (PTEs) contamination sources and the determination of driving factors are the premise of soil contamination control. In our study, 788 soil samples from the National Agricultural Park in Chengdu, Sichuan Province were used to evaluate the contamination degree of soil PTEs by pollution factors and pollution load index. The source identification of soil PTEs was performed using positive matrix decomposition (PMF), edge analysis (UNMIX) and absolute principal component score-multiple line regression (APCS-MLR). The geo-detector method (GDM) was used to analysis drivers of soil PTEs pollution sources to help interpret pollution sources derived from receptor models. Result shows that soil Cu, Pb, Zn, Cr, Ni, Cd, As and Hg average content were 35.2, 32.3, 108.9, 91.9, 37.1, 0.22, 9.76 and 0.15 mg/kg in this study area. Except for As, all are higher than the corresponding soil background values in Sichuan Province. The best performance of APCS-MLR was determined by comparison, and APCS-MLR was considered as the preferred receptor model for soil PTEs source distribution in the study area. ACPS-MLR results showed that 82.70% of Cu, 61.6% of Pb, 75.3% of Zn, 91.9% of Cr and 89.4% of Ni came from traffic-industrial emission sources, 60.9% of Hg came from domestic-transportation emission sources, 57.7% of Cd came from agricultural sources, and 89.5% of As came from natural sources. The GDM results showed that distance from first grade highway, population, land utilization and total potassium (TK) content were the main driving factors affecting these four sources, with q values of 0.064, 0.048, 0.069 and 0.058, respectively. The results can provide reference for reducing PTEs contamination in farmland soil.

Identification of spatial clusters of potentially toxic elements in different soil types using unsupervised machine learning and compositional data analysis

Soil health is important, with soil chemical composition data, including potentially toxic elements (PTEs) being one of its conceptual components. This study aims to reveal the spatial distribution patterns of soil PTEs contents, identify their potential sources, and unveil their geochemical associations in Aragatsotn region, Armenia. For that purpose, the contents of Cr, V, Ti, As, Zn, Cu, Co, Fe, Mn, Ba, and Pb were determined using an X-ray fluorescence spectrometer. The mean contents of Cr and As exceeded their upper continental crust by 1.5 and 3.1 times and their maximum acceptable values by 1.5 and 1.5 times. The analysis demonstrated the presence of sites where all these elements displayed comparatively higher values. The combined application of compositional data analysis and geospatial mapping revealed multivariate outliers, which were located in structural-metallogenic zones with active ore exploitation . The application of unsupervised machine learning algorithm unveiled three groups within the main dataset and the clr-biplot identified the source-specific elements. Particularly, Group I included Cu and displayed the highest mean value among the identified groups. The soil samples included in Group I were in areas where Calcisols were developed and comparatively high Cu contents were attributed to agricultural activities and vehicle emissions. Group II is represented by the geochemical association of Fe, Co, Cr, Mn, Zn, and As. The formation of this group is conditioned by volcanic rocks of the local geological origin. However, no spatial pattern was identified in Group II distribution aligned with soil types. Group III included Ti, V, Pb, and Ba, which may have a mixed origin as it is spatially distributed in areas where regional highways pass through and where Group II elements also exhibit their higher values.

Hydropedological Characterization of a Coal Mining Waste Deposition Area Affected by Self-Burning

Coal mining often produces severe environmental effects, including impacts on the soil system and, specifically, on hydropedological conditions that control the leaching of significant ions and Potentially Toxic Elements (PTEs). The research objective is to assess changes in the hydropedological conditions in an area with a coal mining waste pile that underwent self-burning. An integrative approach was implemented, starting with the definition of hydropedological zoning based on field observations of soil formation factors (namely, parent material, relief, biological activity, anthropic influence, and time). The soil profile in each hydropedological zone was characterized regarding morphological features. The upper mineral horizons were sampled and characterized in terms of mineralogy and PTE geochemistry. Field measurements of unsaturated hydraulic conductivity, soil water content, and hydrophobicity were performed. Afterwards, the hydrogeochemistry of leachates was determined, and the soil leaching potential was evaluated. The research outcomes express substantial differences regarding the hydropedological zones: development of different soil profiles, diverse mineralogy and PTE geochemistry, higher unsaturated hydraulic conductivity and leaching of major ions, and PTEs in soils affected by coal mining activities. Finally, a Principal Component Analysis confirmed the existence of significant contrasts according to hydropedological zoning.

Pollution levels and probability risk assessment of potential toxic elements in soil of Pb-Zn smelting areas.

Soil pollution around Pb-Zn smelters has attracted widespread attention around the world. In this study, we compiled a database of eight potentially toxic elements (PTEs) Pb, Zn, Cd, As, Cr, Ni, Cu, and Mn in the soil of Pb-Zn smelting areas by screening the published research papers from 2000 to 2023. The pollution assessment and risk screening of eight PTEs were carried out by geo-accumulation index (Igeo), potential ecological risk index (PERI) and health risk assessment model, and Monte Carlo simulation employed to further evaluate the probabilistic health risks. The results suggested that the mean values of the eight PTEs all exceeded the corresponding values in the upper crust, and more than 60% of the study sites had serious Pb and Cd pollution (Igeo > 4), with Brazil, Belgium, China, France and Slovenia having higher levels of pollution than other regions. Besides, PTEs in smelting area caused serious ecological risk (PERI = 10912.12), in which Cd was the main contributor to PREI (86.02%). The average hazard index (HI) of the eight PTEs for adults and children was 7.19 and 9.73, respectively, and the average value of total carcinogenic risk (TCR) was 4.20 × 10-3 and 8.05 × 10-4, respectively. Pb and As are the main contributors to non-carcinogenic risk, while Cu and As are the main contributors to carcinogenic risk. The probability of non-carcinogenic risk in adults and children was 84.05% and 97.57%, while carcinogenic risk was 92.56% and 79.73%, respectively. In summary, there are high ecological and health risks of PTEs in the soil of Pb-Zn smelting areas, and Pb, Cd, As and Cu are the key elements that cause contamination and risk, which need to be paid attention to and controlled. This study is expected to provide guidance for soil remediation in Pb-Zn smelting areas.

Source apportionment of soil PTE in a northern industrial county using PMF model: Partitioning strategies and uncertainty analysis

Positive matrix factorization (PMF) has commonly been applied for source apportionment of potentially toxic elements (PTE) in agricultural soil, however, spatial heterogeneity of PTE significantly undermines the accuracy and reliability of PMF results. In this study, a representative industrial-agricultural hub in North China (Xuanhua district, Zhangjiakou City) was selected as the research subject, multiple partition processing (PP) strategies and uncertainty analyses were integrated to advance the PMF modeling and associated algorithm mechanisms were comparatively discussed. Specifically, we adopted three methods to split the research area into several subzones according to industrial density (PP-1), population density (PP-2), and the ecological risk index (PP-3) respectively, to rectify the spatial bias phenomenon of PTE concentrations and to achieve a more interpretable result. Our results indicated that the obvious enrichment of Cd, Pb, and Zn was found in the agricultural soil, with Hg and Cd accounted for 83.49% of the overall potential ecological risk. Combining proper PP with PMF can significantly improve the modelling accuracy. Uncertainty analysis showed that interval ratios of tracer species (Cd, Pb, Hg, and Zn) calculated by PP-3 were consistently lower than that of PP-1 and PP-2, indicating that PP-3 coupled PMF can afford the optimal modeling results. It suggested that natural sources, fertilizers and pesticides, atmosphere deposition, mining, and smelting were recognized as the major contributor for the soil PTE contamination. The contribution of anthropogenic activities, specifically fertilizers and pesticides, and atmosphere deposition, increased by 1.64% and 5.91% compared to PMF results. These findings demonstrate that integration of proper partitioning processing into PMF can effectively improve the accuracy of the model even at the case of soil PTE contamination with high heterogeneity, offering support to subsequently implement directional control strategies.

Evaluation of potentially toxic elements within the vicinity of an integrated agro industry, Nigeria

The contamination of soils and crops by potentially toxic elements (PTEs) affects the food quality and it is perceived as a huge threat to human health. PTEs (Chromium, Cadmium, Lead, Copper, Nickel and Zinc) were evaluated in soil and crop (Manihot esculenta) around an integrated agro industry in Nsukka in two different seasons using Flame Atomic Absorption Spectrophotometer (FAAS). The concentration status of these PTEs, their ecological risks and human health risk potential associated with their consumption were evaluated. The following PTE mean concentration ranges (ppm) were found in the crop throughout the dry season: Zn (0.0115 - 0.1470), Pb(0.2499 - 0.2601), Cu(0.0215 - 0.1359), Ni(0.1029 - 0.3760), and Cr(0.1560 - 0.4279). During the wet season, the mean concentration ranges (ppm) of PTEs in crop are as follows: chromium (undetectable (ND) - 0.3498), Cd(ND - 0.0598), Pb(ND - 0.1989), Cu(0.0218 - 0.0860), Ni(0.1029 - 0.1116), Zn(0.0090 - 0.0720), and so on. During the dry season, the PTEs in soil are as follows: Cr(0.1180 - 0.3887), Cd(0.0597 - 0.1313), Pb(0.2598 - 0.8330), Cu(0.0333 - 0.1834), Ni(0.2069 - 0.7860), and Ni(0.1160 - 1.7550). The following are the mean concentration ranges (ppm) of PTEs found in soil during the wet season: Zn(0.0119 -0.1013), Pb(0.2981 - 0.3974), Cu(0.0220 - 0.0860), Ni(0.1034 - 0.4449), and Cr(ND - 0.1561). The health risk index for Manihot esculenta, according to its non-carcinogenic human health risk assessment, was as follows: Pb(2.598 for adults and 9.329 for children in the dry season) and Cd(0.342) and chromium (0.449) on farm 1, respectively; Zn, Cu and Ni did not exhibit any health risk values; Cr(1.226 and 1.001 for children in the dry and wet seasons) on farm 2, and other metals did not exhibit any human health risk values; on farm 3, Pb(2.498 for adults and 8.974 for children in the dry season), Cd(0.852 and 0.685 for children in the wet and dry seasons respectively) and (0.239 and 0.192 for adults in the wet and dry seasons respectively), while the other metals did not exhibit any health risk values. According to the carcinogenic health risk evaluation, every metal evaluated had an incremental lifetime cancer risk (ILCR) value between 10−3 and 10−6 for adults and children on every farm that was studied. According to the ecological risk index, pollution load index (PLI), the levels of contamination (Cf), transfer factor (Tf) and degree of contamination (Cd) were all below the corresponding threshold limits. This generally showed that the vicinity of the industry is relatively polluted and there should be a regulatory enforcement on the surrounding environment.

Comprehensive exploration on transfer and human health risk of potential toxic element in soil‐rice system from the Pearl River Delta

AbstractThe transfers of potential toxic elements (PTEs) from root soil to rice grains and its driving factors are of major worldwide concern. And it is still not clear whether the parent material has influence on the transfers of PTEs in soil. Thus, the aim of this study is to investigate the transfers of PTEs in soil‐rice system from different parent materials area, identify its driving factors and evaluate human health risk. 157 sets of root soil and rice grains samples collected from the areas with quaternary sediments, acidic magmatic rocks and terrigenous clastic rocks in the Pearl River Delta, China. Pearson correlation analysis, discriminant analysis, redundancy analysis, path analysis and human health risk model were utilized for data processing and analysis. The results reveal that parent materials play a primary role affecting the transfers of PTEs in soil‐rice system, and its influence on transfers of PTEs is achieved by governing physicochemical properties of soil. And physicochemical parameters like MgO, SiO2, Al2O3, TFe2O3, and organic matter (OM) exerted significant influence on transfers of PTEs. The influences of some physicochemical parameters on the transfers of PTEs are most significantly in the area of quaternary sediments. The values of the total non‐carcinogenic and the total carcinogenic risks for children and adults caused by rice consumption are much higher than the corresponding risk limits, and the main contributing elements are Pb, As, and As, Cd, respectively. The human health risks caused by rice consumption are greatest in the area with quaternary sediments.

Potentially Toxic Elements (PTEs) Dispersion in Alluvial Deposits from Abandoned Mining Sites

In the watersheds of abandoned mining districts, it is common to find remains of former facilities and waste dams on stream banks and slopes—a situation that results in the transport and accumulation of metal(loid)s in alluvial deposits. To analyze this problem, an area of the former mining district of Linares–La Carolina (southern Spain) was selected to evaluate the contents and distributions of Ag, As, Ba, Cu, and Pb as potentially toxic elements (PTEs) found in the mineral paragenesis. Specifically, this study focused on the Siles Stream, which runs through a sector where underground mining for the exploitation of galena veins generated abundant mining wastes, mainly waste rock and tailings. Thirty-four sediment samples from the stream bed of the Siles Stream and two sediment samples from the Guadiel River, of which it is a tributary, were analyzed. Floodplain sediments were sampled in the stream banks at the middle and lower reaches (11 samples), as well as the riverine soils developed at the mouth of the Siles Stream (22 samples). The analyzed samples presented high levels of PTEs, in most cases with values much higher than the generic reference levels established by European and regional legislation for PTEs in soils. In the case of Pb, the main metal mined in this district, contents of up to 27,074 mg·kg−1 were observed in the stream bed sediments. Very high concentrations of Pb also appeared in the floodplain sediments, with maximum values in the middle course of the stream, where the concentration reached 43,692 mg·kg−1. With respect to the sediments of the Guadiel river bed, the Pb content was 699 mg·kg−1 before the confluence with the stream and 2537 mg·kg−1 downstream, which clearly reflects the influence of the contributions from the Siles Stream. The enrichment factors (EFs) show that the sediments present a severe to very severe anthropogenic influence for Ag, As, Ba, Cu, and Pb. The geoaccumulation index (Igeo) indicates that the entire basin is extremely polluted by Pb, to which As and Ag are added in the middle course of the stream. The potential ecological risk index (RI) and pollution load index (PLI) based on the contamination factor (CF) suggested that metal loads far exceeded the reference values. Selective chemical extraction methods were used to assess the potential bioavailability of these elements in sediment and soil samples. The results showed high concentrations of Pb in the exchangeable fraction, which poses a significant ecological risk and potential human health risks.

Characteristics, source analysis, and health risk assessment of potentially toxic elements pollution in soil of dense molybdenum tailing ponds area in central China.

The issue of potentially toxic elements (PTEs) contamination of regional soil caused by mining activities and tailings accumulation has attracted wide attention all over the world. The East Qinling is one of the three main molybdenum mines in the world, and the concentration of PTEs such as Hg, Pb and Cu in the slag is high. Quantifying the amount of PTEs contamination in soil and identifying potential sources of contamination is vital for soil environmental management. In the present investigation, the pollution levels of 8 PTEs in the Qinling molybdenum tailings intensive area were quantitatively identified. Additionally, an integrated source-risk method was adopted for resource allocation and risk assessment based on the PMF model, the ecological risk, and the health risk assessment model. The mean concentrations of Cu, Ni, Pb, Cd, Cr, Zn, As, and Hg in the 80 topsoil samples ranged from 0.80 to 13.38 times the corresponding background values; notably high levels were observed for Pb and Hg. The source partitioning results showed that PTEs were mainly affected by four pollution sources: natural and agricultural sources, coal-burning sources, combined transport and mining industry sources, and mining and smelting sources. The health risk assessment results revealed that the risks of soil PTEs for adults are acceptable, while the risks for children exceeded the limit values. The obtained results will help policymakers to obtain the sources of PTEs of tailing ponds intensive area. Moreover, it provides priorities for the governance of subsequent pollution sources and ecological restoration.

Source analysis and contamination evaluation of potentially toxic elements in soil in typical high geological background areas at the county scale in northeastern Yunnan, China

The pollution risk of potentially toxic elements (PTEs) in soil is a common concern in the fields of environmental science and agriculture. The spatial distribution characteristics, pollution risk assessment and genetic sources of PTEs in soil in high geological background areas are crucial to the safe use of land. Based on the data for five PTEs in 921 surface soil samples from typical high geological background areas in SW China, we discuss their spatial distribution characteristics using geostatistics, the semivariance function and its model. We carry out pollution risk assessment using the influence index of comprehensive quality (IICQ) and analyse their genetic sources using the UNMIX receptor model. The spatial distribution of element content has a high spatial coupling with the stratigraphic spread, which is affected by external random factors, resulting in a weakened autocorrelation. The IICQ indicates that soil is dominated by mild and moderate pollution, accounting for 42.24 and 44.95%, respectively, with cadmium contributing up to 63.00% to the IICQ. Chromium and cadmium are controlled by natural sources, accounting for 83.98 and 69.39%, respectively. Arsenic and mercury have anthropogenic sources, accounting for 68.7 and 44.0%, respectively. Lead is controlled by both lead–zinc mining and geological background, accounting for 47.7 and 36.4%, respectively. The UNMIX model demonstrates that the spatial variability of PTEs is influenced by anthropogenic factors, such as coal combustion emissions, which account for 30.1% of the pollution sources. Soil parent material sources contribute 49.4%, followed by lead–zinc mining and smelting activities at 20.5%.

Potentially toxic elements (PTEs) and ecological risk at waste disposal sites: An analysis of sanitary landfills.

This study presents an analysis of soil contamination caused by Ni, Zn, Cd, Cu, and Pb at municipal solid waste (MSW) landfills, with a focus on ecological risk assessment. The approach aims to assess how different landfill practices and environmental conditions affect soil contamination with potentially toxic elements (PTEs) and associated environmental risks. Soil samples were collected from MSW landfills in Poland and the Czech Republic. The research included a comprehensive assessment of PTEs in soils in the context of global environmental regulations. The degree of soil contamination by PTEs was assessed using indices: Geoaccumulation Index (Igeo), Single Pollution Index (Pi), Nemerow Pollution Index (PN), and Load Capacity of a Pollutant (PLI). The ecological risk was determined using the Risk of PTEs (ERi) and Sum of Individual Potential Risk Factors (ERI). The maximum values of the indicators observed for the Radiowo landfill were as follows: Igeo = 4.04 for Cd, Pi = 24.80 for Cd, PN = 18.22 for Cd, PLI = 2.66, ERi = 744 for Cd, ERI = 771.80. The maximum values of the indicators observed for the Zdounky landfill were as follows: Igeo = 1.04 for Cu, Pi = 3.10 for Cu, PN = 2.52 for Cu, PLI = 0.27, ERi = 25 for Cd, ERI = 41.86. The soils of the tested landfills were considered to be non-saline, with electrical conductivity (EC) values less than 2,000 μS/cm. Varying levels of PTEs were observed, and geostatistical analysis highlighted hotspots indicating pollution sources. Elevated concentrations of Cd in the soil indicated potential ecological risks. Concentrations of Cu and lead Pb were well below the thresholds set by the environmental legislation in several countries. In addition, Ni concentrations in the soils of both landfills indicated that the average levels were within acceptable limits. Principal Component Analysis (PCA) revealed common sources of PTEs. The identification of specific risk points at the Radiowo and Zdounky sites contributes to a better understanding of potential hazards in landfill environments. By establishing buffer zones and implementing regular maintenance programs, emerging environmental problems can be addressed in a timely manner.

Spatial distribution and source identification of potentially toxic elements in Yellow River Delta soils, China: An interpretable machine-learning approach

Identifying the driving factors and quantifying the sources of potentially toxic elements (PTEs) are essential for protecting the ecological environment of the Yellow River Delta. In this study, data from 201 surface soil samples and 16 environmental variables were collected, and the random forest (RF) and Shapley additive explanations (SHAP) methods were then combined to explore the key factors affecting soil PTEs. An innovative t-distributed random neighbor embedding-RF-SHAP model was then constructed, based on the absolute principal component score and multivariate linear regression model, to quantitatively determine PTE sources. Although average PTE concentrations did not exceed the risk control values, PTE distributions exhibited significant differences. It was found that sodium, soil organic matter, and phosphorus contents were the three most important factors affecting PTEs, and human activities and natural environmental factors both influence PTE contents by altering the soil properties. The proposed model successfully determined PTE sources in the soil, outperforming the original linear regression model with a significantly lower RMSE. Source analysis revealed that the parent material was the main contributor to soil PTEs, accounting for more than half of the total PTE content. Industrial and agricultural activities also contributed to an increase in soil PTEs, with average contributions of 19.91 % and 17.44 %, respectively. Unknown sources accounted for 10.83 % of the total PTE content. Thus, the proposed model provides innovative perspectives on source parsing. These findings provide valuable scientific insights for policymakers seeking to develop effective environmental protection measures and improve the quality of saline-alkali land in the Yellow River Delta.