Potentially Toxic Elements In Soils Research Articles

Characterization and risk assessment of soil around waste rock heaps affected by acid rock drainage in an abandoned pyrite mining area

Acid rock drainage (ARD) is one of the most serious and potentially lasting environmental issues for the mining industry. Many researchers investigated the impact of ARD on downstream farmland, but few focused on the soil properties change around waste rock heaps. In this study, a total of 119 soil samples were taken around the 35 waste rock heaps which are scattered in 12 mining sites in an abandoned pyrite mining area (Baihe County, Northwest China). Both rainy and dry seasons of ARD were collected from the discharge outlet of each mining site. The bulk levels of potentially toxic elements (PTEs), including As, Cd, Cu, Ni, Cr, Zn, Pb, Fe, Mn, and F, in waste rock, soil, and ARD samples were analyzed. Leaching concentration and chemical speciation of these PTEs in soils were further investigated. The results show that the ARD had very high pollution loads of PTEs both in the rainy season and dry season, continuously exporting pollutants to the surrounding soils. More than 70% of the soil samples were acidic (pH<5.5). The bulk of As in 17 soil surface samples exceeded the risk control limit specified in China (60 mg/kg), while the leaching concentrations of As and other PTEs in soil were far below the regulated limits. According to the sequential extraction results, the residual fraction of As, Cr, Cu, Zn, and Ni in the soil accounted for over 90%, indicating these metals were possibly retained by the silicate matrix. Considering the relatively low bioavailability of PTEs and limited exposure routes, the human health risk of the soil surrounding the waste heap is generally acceptable. This research work provides a more comprehensive understanding of the properties and effects of ARD in the pyrite mining area which is conducive to the development of a sustainable control strategy of environmental pollution in typical mining regions.

Use of modeling to map potentially toxic elements and assess the risk to human health in soils affected by mining activity

Determining the levels and spatial distribution of potentially toxic elements (PTEs) is essential in designing mitigating strategies to remediate contaminated areas. Efficient prediction of PTEs is difficult due to high spatial variability and multiple sources of contamination. The use of machine learning algorithms is an alternative for the improvement of the predictions. Objective of the study was to model the spatial distribution of PTEs in soils surrounding a tailings pile and to assess potential risks to human health. A total set of 116 soil samples was collected to a depth of 0–10 cm. The covariate database was composed of morphometric variables derived from a DEM and the creation of a tailings pile location covariate. The models tested were Cubist (CUB), Random Forest (RF), Support Vector Machine (SVM), and Linear Model (Lm). Based on the best predictive model, maps showing the spatial distribution, pollution and risk to human health were created. The SVM model had the best performance for predicting spatially the soil contents of Pb and Zn, with lower values of mean absolute error (MAE − 744.71; 306.36) and higher values of R2 (0.56; 0.52). It was possible to verify that the mining tailings pile is the main source of Pb and Zn contamination in the study area. The enrichment factor (EF) and the geoaccumulation index (Igeo) of Pb and Zn show that the soils close to the tailings piles are extremely contaminated (Igeo > 5 and EF > 40), and pose risks to human health (Total carcinogenic risk > 1 × 10–6), especially for children. Therefore, new studies must be carried out with the aim of monitoring and rehabilitating the contaminated areas.

Factors conditioning soil PTE contents and the associated health risk in an area with mixed land use.

The study of soil chemical composition and geochemical characterization is of great concern. In 2020, a soil survey of the Ararat region (Armenia) was conducted to study the contents of soil elements (Cr, V, Ti, As, Zn, Cu, Co, Fe, Mn, Ba, Pb, Mo, Ca, and K), identify pollution sources and factors conditioning their spatial distribution patterns, and assess the health risk associated with potentially toxic elements (PTEs). The combined application of compositional data analysis and geospatial mapping allowed to reveal three subsamples with unique chemical signatures. Group I included soils in which Fe, Co, Ti, Mn, V, Ba, Pb, and Zn had mainly a natural origin. Soils of Group II are localized in heavily urbanized and industrialized parts of the region, and their spatial distribution is in line with relatively high contents of Cu and partially As, Cr, and K. The spatial distribution of Group III coincides with positions of soils with relatively high contents of Ca and is in line with the geological features and the locations of stone quarries. The human health risk assessment showed that As contents pose a mono-elemental noncarcinogenic health risk to children in two sites (near the Gold Factory and Tigranashen village), whereas a multi-elemental health risk to children was identified on almost the entire region's territory. Moreover, the comparatively high level of As risk was identified in Group III and linked to the travertine quarries exploitation. The results of this study indicated the need for additional in-depth studies targeting As contents and its unrevealed features linked to the travertine quarries exploitation.

A machine learning and geostatistical hybrid method to improve spatial prediction accuracy of soil potentially toxic elements

Effective environmental management and contamination remediation require accurate spatial distributions and predictions of potentially toxic elements (PTEs) in the soil. However, no single method has been developed to predict soil PTE accurately. This study evaluated the advanced geostatistical method of empirical Bayesian kriging regression prediction (EBKRP), machine learning algorithm of random forest (RF), and hybridized model (RF-EBKRP) to predict and map PTEs content in greenspace soils. As identified by RF, soil organic carbon, organic matter, total (nitrogen, phosphorus, and potassium), topographic features, and urban functional types were used as significant covariates to improve the prediction accuracy of PTEs in soil. The model prediction performance was evaluated using the root mean square error (RMSE), mean absolute percentage error (MAPE), and coefficient of determination (R2). Results showed that RF performed much better than EBKRP in predicting soil PTEs, with lower prediction errors and a higher R2. The RMSE, MAPE, and R2 values for the RF model were 0.25–85.32 mg/kg, 3.86–25.40%, and 0.77–0.90, respectively, while the values for the EBKRP method were 0.51–99.03 mg/kg, 5.42–32.13%, and 0.40–0.66. Moreover, the RF-EBKRP method produced more accurate spatial predictions and distributions of PTEs than the individual models, with R2 improvements of 122.5% for EBKRP and 15.58% for RF. The better performances of RF-EBKRP are due to its incorporation of various covariates and its ability to handle complex nonlinear relationships between soil PTEs and covariates. In the end, a hybrid RF-EBKRP method is a promising approach to improving the spatial distribution map of soil PTEs.

A joint method to assess pollution status and source-specific human health risks of potential toxic elements in soils.

Potential toxic elements (PTEs) in soils follow various exposure pathways (e.g., ingestion, dermal contact, and inhalation) when migrating to the human body, and can threaten human health. The objective of this study was to quantitatively evaluate the pollution status and human health risk for different age groups (i.e., children and adults) caused by source-specific PTEs in the soil. A total of 425 topsoil samples (0-20 cm) were collected in the Zhangqiu District of China, and contents of eight PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were analyzed simultaneously. The PTE sources were identified using a geostatistical method, and positive matrix factorization was used to apportion the contribution rate of each PTE source for human health risk of different age groups based on a health risk assessment model. Results showed that: (1) As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn contents all exceeded the background values in soil, indicating that there had been a slight enrichment of soil PTEs over time; (2) Cr and Ni were derived from natural sources, while Cd, Cu, and Zn were derived from transportation sources; industrial emissions and coal burning intensified pollution from Hg, Pb, and As in soils, as shown in the average contribution percentages of natural sources (24.36%), transportation sources (33.79%), and industrial sources (41.85%); (3) the non-carcinogenic risk caused by soil PTEs did not endanger human health, but the carcinogenic risk was close to the risk threshold, and should be given attention; the largest carcinogenic risk (36.53%) and non-carcinogenic risk (36.01%) for children were attributed to industrial sources, while the largest carcinogenic risk (34.98%) and non-carcinogenic risk (37.06%) for adults were attributed to transportation sources. The results presented in this study provide support for effectively preventing PTE health risks in different age groups from source-specific PTE pollution of the soil.

Accumulation pattern and risk assessment of potentially toxic elements in selected wastewater-irrigated soils and plants in Vehari, Pakistan

There are scarce data about the accumulation pattern and risk assessment of potentially toxic elements (PTEs) in soil and associated potential ecological risks, especially in less-developed countries. This study aims to assess the pollution levels and potential ecological risks of PTEs (As, Cr, Cd, Cu, Ni, Mn, Pb and Zn) in wastewater-irrigated arable soils and different edible-grown plants in selected areas of Vehari, Pakistan. The results revealed that the values of PTEs in soil samples were higher than their respective limit values by 20% for As, 87% for Cd, 15% for Cu, 2% for Cr, 83% for Mn, 98% for Fe, and 7% for Zn. The values of soil risk indices such as the potential ecological risk (PERI >380 for all samples), pollution load index (PLI >4 for 94% of studied samples), and degree of contamination (Dc > 24 for all samples) showed severe soil contamination in the study area. Some vegetables exhibited a high metal accumulation index (e.g., 8.1 for onion), signifying potential associated health hazards. Thus, long-term wastewater irrigation has led to severe soil contamination, which can pose potential ecological risks via PTE accumulation in crops, particularly Cd. Therefore, to ensure food safety, frequent wastewater irrigation practices need to be minimized and managed in the study area.

Assessment of potential exposure to As, Cd, Pb and Zn in vegetable garden soils and vegetables in a mining region

Mining and smelting activities can contaminate soils and affect farming due to high emissions and input of potentially toxic elements (PTE) into the environment. Soils (sampled from two depths) and market vegetables from vegetable gardens located within the vicinity of unconfined slag deposits from decades of mining and smelting activities in Kutná Hora, Czechia were assessed to determine to what extent they pose a health hazard to communities that use these gardens. Pseudo-total As concentrations in the soils exceeded background levels (4.5 mg kg−1) 1.9–93 times, with higher concentrations in the deeper layer. The pseudo-total concentrations of PTE in soils ranked in the order As > Zn > Cd > Pb. Phyto-available concentrations of PTE in soils were relatively low, compared to pseudo-total concentrations. Concentration of As, Cd, Pb and Zn in the vegetables exceeded guideline values, with the highest concentrations found in the fruits of cucumber, peppers, and zucchini. Despite low phyto-available PTE concentrations in soils, all the PTE concentrations in the vegetables surpassed the guidelines set by the Czech Ministry of Health and EU directive, indicating a health hazard to consumers.

Evaluating sample sizes and design for monitoring and characterizing the spatial variations of potentially toxic elements in the soil

Cost-effective, representative and spatial coverage sampling designs are required to monitor the effects of potentially toxic elements (PTEs) in the soil. This study aims to evaluate the minimum sample sizes and placement of soil sampling designs to monitor and characterize the spatial variation of the PTEs (Cu, Zn, Cd, Cr, Pb, and Ni) in the soils. However, there is no standardized approach for evaluating the optimum soil sample size and monitoring location because of the spatial heterogeneity of PTEs in the soil. As a result, three broad techniques were applied. The first step was to use Global Moran's I and q-statistic values to describe the variability of soil PTEs and select appropriate evaluation methods. Second, using simple random sampling (SRS), ordinary kriging (OK), and Mean of Surface with Non-homogeneity (MSN), we estimated and evaluated soil PTEs in the current soil sampling schemes. Finally, MSN and spatial simulated annealing (SSA) optimization techniques were used to assess the required sample sizes and placements in the existing designs. Method performance was evaluated using a standard error (SE) and a relative standard error of the mean (RSE). Except for Zn and Cd, all PTEs tested showed heterogeneous distributions over the area. The MSN lowered the predicted SE by 79–86 % compared with SRS. The OK approach also outperformed the SRS method regarding mean estimated values of soil PTEs by 42–57 %. After SSA refined the initial design, the predicted SE by MSN of Cr and Zn was lowered by 13 % and 39 %, respectively. The MSN was effective with small sample sizes, reducing sample sizes and surveying costs by 39 % after SSA optimized the existing sample numbers. Thus, integrating various sampling strategies may be efficient for building optimal sample designs to monitor PTEs in the soil.

Coronilla juncea, a native candidate for phytostabilization of potentially toxic elements and restoration of Mediterranean soils

Soil contamination pattern due to industrial activities often leads to high concentrations of potentially toxic elements (PTE) decreasing with depth. This spatial heterogeneity of the soil contamination may have significant consequences on the soil properties and soil living communities. We evaluated the effects of both surface and solum soil contamination heterogeneity on Coronilla juncea L. (Fabaceae) functional traits in field conditions and the phytostabilization potential of this species. Plant and soil samples were collected on 3 sites along a PTE contamination gradient. The correlations between PTE concentration in plant and soil samples at 2 depths, physico-chemical properties of soil, plant biomass and soil microbial activity were tested. Field measurements highlight a decreasing PTE concentration with soil depth in addition to an important surface heterogeneity of As, Cu, Pb, Sb and Zn soil concentrations. Root PTE concentrations in C. juncea did not follow soil PTE concentrations. Concentrations of PTE in the root parts were higher than those of the aerial parts. Low PTE translocation and root symbioses with microorganisms suggest that this native plant species may play a role as engineer species with positive implications for the phytostabilization of Mediterranean PTE contaminated soils and their ecological restoration.

Analysis of potential toxic elements in soil of the Czech dump-side

Analysis of potential toxic elements in soil of the Czech dump-side

Recognition method for the health risks of potentially toxic elements in a headwater catchment

The spatial association of potentially toxic elements (PTEs) in soil–crop–groundwater systems is poorly recognised. In this study, the contents of arsenic (As), cadmium (Cd), copper (Cu) and lead (Pb) in paddy soils, rice and groundwater in the Xiancha River catchment were determined. The intrinsic effects of PTEs in soils on their spatial distribution in groundwater and rice were explored. Also, the potential sources and health risks of PTEs in multi-media were investigated. Results showed that the mean contents of As and Cd in soils were 23.86 and 0.26 mg kg−1, respectively. In groundwater, the maximum (average) content of As reached 6.55 (1.84) μg L−1. Moreover, As contents in soils and groundwater showed a sound spatial correlation (q = 0.81), and this is supported by the result of the soil column experiment, indicating homology and the strong vertical migration capacity of As. The non-homologous patterns of Pb, Cu and Cd contaminations in soil–groundwater system suggested that geogenic processes influenced the distribution of these PTEs. Cd presented a poor spatial correlation in soil–rice system, as multiple factors controlled its transfer process. Multivariate statistical analysis results demonstrated that As, Cu and Pb in soils mainly came from agricultural sources, whereas high Cd levels were from mining activities. Additionally, direct consumption of As-contaminated groundwater and Cd-contaminated rice posed significant health risks to local residents. This study, which proposes a risk recognition method used to investigate target PTEs in multi-media, may serve as a valuable reference for further research involving catchments.

Source Identification and Apportionment of Potential Toxic Elements in Soils in an Eastern Industrial City, China.

The extensive pattern of economic growth has an inestimable negative impact on the ecological environment, which causes the soil pollution problem to become increasingly prominent. In order to improve the effectiveness and rationality of prevention and control of heavy metal pollution in regional soil, it is necessary to understand the current situation of pollution, identify pollution sources and clarify future pollution risks. In this paper, an industrially developed city in eastern China was taken as the study region. The positive matrix factorization model (PMF) model and Unmix model was applied to identify and apportion the pollution sources of soil potential toxic elements after evaluating the ecological risk of soil potential toxic elements. The PMF model identified six factors, including single source and composite source. The Unmix model also identified six sources, including sources of nature, industrial discharge and traffic emissions. The comparison between the two models showed that Hg and Ni pollution, as well as Cr enrichment in the study region, were related to the industrial discharge from enterprises and factories. Cd pollution was related to traffic emission sources. Cu and Zn pollution were related to the multiple sources mixed with soil parent material, traffic emissions and industrial discharge from electronic enterprises. Pb pollution was related to natural sources (e.g., soil pH) but also to industrial sources (e.g., industrial wastes discharge). Enrichment was related to soil parent material and agricultural inputs. Our study also implies that soil heavy metal pollution or enrichment in the study region was mainly from anthropogenic sources and supplemented by natural sources.

Hazardous enrichment of toxic elements in soils and olives in the urban zone of Lavrio, Greece, a legacy, millennia-old silver/lead mining area and related health risk assessment

Lavrio is a Greek town with several abandoned Ag/Pb mines. In this study, 19 potentially toxic elements (PTEs) were measured in soil, weeds, and olives. Levels of seven of the studied PTEs in soil were highly elevated: Zn (56.2–58,726 mg kg-1), Pb (36.2–31,332), As (7.3–10,886), Cu (8.3–1273), Sb (0.99–297.8), Cd (0.17–287.7), and Ag (0.09–38.7). Synchrotron-based X-ray absorption near edge structure analysis of the soils revealed that As was predominantly associated with scorodite, Pb with humic substances, Zn with illite, Zn(OH)2 and humic substances, and Fe with goethite-like minerals. The transfer of the PTEs to weeds was relatively low, with the transfer coefficient being less than 1.0 for all PTEs. Cadmium in table olives surpassed 0.05 mg kg-1 fresh weight (the limit in EU), while Pb surpassed its limit in approximately half of the samples. Health risk assessment confirmed soil contamination in the study area where As and Pb hazard quotients were well above 1.0 and the average hazard index equaled 11.40. Additionally, the cancer risk values exceeding the 1 × 10-4 threshold. The results obtained in the study indicate that Lavrio urgently requires an adequate ecofriendly remediation plan, including revegetation with tolerant species and targeted efforts to chemically stabilize harmful PTEs. The presented approach may serve as a pivotal study for industrial areas with similar contamination levels.

Spatial distribution patterns and sources for potential toxic elements in soil in the Daxing District, Beijing, China

Spatial distribution patterns and sources for potential toxic elements in soil in the Daxing District, Beijing, China

Phytoremediation of Soils Contaminated with Heavy Metals from Gold Mining Activities Using Clidemia sericea D. Don.

Soils contaminated by potentially toxic elements (PTEs) as a result of anthropogenic activities such as mining are a problem due to the adverse effects on human and environmental health, making it necessary to seek sustainable strategies to remediate contaminated areas. The objective of this study was to evaluate the species Clidemia sericea D. Don for the phytoremediation of soils contaminated with PTEs (Hg, Pb, and Cd) from gold mining activities. The study was conducted for three months, with soils from a gold mining area in northern Colombia, and seeds of C. sericea, under a completely randomized experimental design with one factor (concentration of PTEs in soil) and four levels (control (T0), low (T1), medium (T2), and high (T3)), each treatment in triplicate, for a total of twelve experimental units. Phytotoxic effects on plants, bioconcentration (BCF), and translocation (TF) factors were determined. The results obtained for the tissues differed in order of metal accumulation, with the root showing the highest concentration of metals. The highest values of bioconcentration (BCF > 1) were presented for Hg at T3 and Cd in the four treatments; and of translocation (TF > 1) for Hg and Pb at T0 and T1; however, for Pb, the TF indicates that it is transferable, but it is not considered for phytoextraction. Thus, C. sericea demonstrated its potential as a phytostabilizer of Hg and Cd in mining soils, strengthening as a wild species with results of resistance to the stress of the PTEs evaluated, presenting similar behavior and little phytotoxic affectation on the growth and development of each of the plants in the different treatments.

A comprehensive exploration on the health risk quantification assessment of soil potentially toxic elements from different sources around large-scale smelting area.

Non-ferrous metal smelting activities have always been considered as one of the foremost anthropogenic sources of potentially toxic elements (PTEs). The enrichment factor (EF) and pollution load index (PLI) were used to evaluate the pollution level of soil PTEs; positive matrix factorization (PMF), correlation analysis, and geostatistics were utilized to quantify the sources of soil PTEs; and potential ecological risk (PER) and human health risk (HHR) of different sources from farmland, construction land, and natural land were quantifiably determined via combined PTE sources with PER and HHR assessment models. Taking the smelting area of Daye City as an example, the evaluation results of EF and PLI showed that the soil PTE pollution in the study area was serious, especially Cd and Cu. And four sources were quantitatively allocated as agricultural practices (12.14%), traffic emissions (23.07%), natural sources (33.46%), and industrial activities (31.33%). For PER, industrial activities were the largest contributor to PER, accounting for 55.66%, 56.30%, and 55.36% of farmland, construction land, and natural land, respectively, and Cd was the most dangerous element. In terms of HHR, industrial activities were also the cardinal contributors under the three land use types. Children were exposed to serious non-carcinogenic risks under three land use patterns and slight carcinogenic risk in construction land (1.06E - 04). Significantly, the carcinogenic risk of children in farmland (9.06 × 10-5) was very close to the threshold (1 × 10-4), which requires attention. Both non-carcinogenic and carcinogenic risk for adults were all at acceptable levels. The health risks (carcinogenic and non-carcinogenic risks) of children from four different sources were distinctly higher than those of adults. Consequently, strict management and control of industrial activities should be given priority, and the management of agricultural practices should not be ignored.

Assessment of Potentially Toxic Element Concentrations in Soil And Vegetables and Impact on Human Health Through TF, EDI, and HRI Indicators: Case Study Anadrinia Region (Kosovo).

Vegetable cultivation areas in the Anadrinia region may have higher than background concentrations of potentially toxic elements (PTEs) from contaminated sources including anthropogenic activity and lithologic composition. The purpose of the present study was to assess PTEs concentrations in soil and vegetables and their impact on human health. In this study, 50 soils and 5 vegetables were sampled from the studied area. PTEs (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES) after digestion in microwave system. PTEs in soil and vegetables were assessed and compared to international data (Dutch List and WHO/FAO 2011), and their toxicological risk was estimated using transfer factor (TF), estimated daily intake (EDI), and hazard quotients (HQ). The average values of As, Cd, Co, Fe, and Mn in soil were 44.96, 0.324, 16.34, 13,172, and 765.1 mg/kg, and Cr, Ni, and Pb in vegetables were 21.02, 17.11, and 4.982 mg/kg. TF values were less than 1, suggesting low bioaccumulation. EDI values of Cu, Ni, Pb, and Zn were 6.29, 6.23, 2.09, and 16.6 mg/kg, higher than international guidelines. HQ values of Pb, Ni, and Cu were 6.22, 3.66, and 1.72, higher than maximum tolerable value 1 indicating significant health risk. Some of the analyzed elements in soil and vegetable exceeded permissible limits to Dutch List and WHO/FAO 2011, respectively. From a health point of view, this study revealed vegetable contamination, recommends periodic monitoring.

Appraisal of vulnerable zones of non-carcinogenic and carcinogenic causing health risks associated with exposure of potentially toxic elements in soils of India: a meta-analysis

Contamination of soil potentially toxic elements (PTEs) has observed in many parts of the world, specifically developing countries such as India. In this study, we only obtained the available data in the literature from 2001 to 2020 on soil PTEs in India. To evaluate the soil contamination, geo-accumulation index and contamination factor (CF) were implemented, along with the health risk assessment was also applied which was proposed by the US Environmental Protection Agency. The mean values obtained for soils of India are Cr (412.28 mg/kg), Cu (159.78 mg/kg), Zn (437.44), Pb (77.25 mg/kg) and As (38.61 mg/kg). The geo-accumulation index and CF showed that Cu, Zn, Ni and As are the main contaminants. The results of health risk show that children are susceptible to both non-carcinogenic and carcinogenic risks of the studied PTEs compared to adults.

Effects of mining on the potentially toxic elements in the surrounding soils in China: A meta-analysis

Previous studies about the effects of mining on the potentially toxic elements (PTEs) in the surrounding soils mainly focused on single or few mining areas. However, these studies couldn't comprehensively quantify the mining-induced variations of soil PTE concentrations at the national scale. Moreover, the quantitative relationships between the effects of mining on soil PTEs and some related factors remained unclear at the national scale. This study first conducted a literature survey for soil PTE data affected by mining in China. Then, the random-effects model in the meta-analysis was used to quantify mining-induced variations of soil PTE concentrations in the surrounding areas. Last, the single meta-regression was used to explore the relationships between the effects of mining on soil PTEs and the related factors at the national scale. Results showed that: (i) mining-induced increases of soil PTE concentrations followed the order: Cd (1017%) > Hg (319%) > Pb (291%) > Zn (176%) > Cu (129%) > As (92%) > Ni (23%); (ii) mining-induced increases of soil PTE concentrations in clay (531%), non-ferrous mine (188%), paddy field (212%), and Central South China (290%) were more than those in other soil textures, mine types, land-use types, and geographical divisions, respectively; (iii) the effects of mining on soil PTEs were negatively correlated with soil pH (QM = 29.76, p < 0.01) and positively correlated with soil organic carbon (QM = 28.54, p < 0.01) and mean annual precipitation (QM = 91.75, p < 0.01); (iv) the effects of mining overall decreased with the sampling year (QM = 35.01, p < 0.01) and showed latitudinal zonality (QM = 180.39, p < 0.01). The above results provided valuable information for soil PTE mitigation in the areas affected by mining in China.

Integrated assessment of the impact of land use types on soil pollution by potentially toxic elements and the associated ecological and human health risk

The impact of land use type on the content of potentially toxic elements (PTEs) in the soils of the Qinghai-Tibet Plateau (QTP) and the associated ecological and human health risks has drawn great attention. Consequently, in this study, top- and subsurface soil samples were collected from areas with four different land uses (i.e., cropland, forest, grassland, and developed area) and the total contents of Cr, Cd, Cu, Pb and Zn were determined. Geostatistical analysis, self-organizing map (SOM), and positive matrix factorization (PMF), ecological risk assessment (ERA) and human health risk assessment (HRA) were applied and used to classify and identify the contamination sources and assess the potential risk. Partial least squares path modeling (PLS-PM) was applied to clarify the relationship of land use with PTE contents and risk. The PTE contents in all topsoil samples surpassed the respective background concentrations of China and corresponding subsurface concentrations. However, the ecological risk of all soil samples remained at a moderate or considerable level across the four land use types. Developed area and cropland showed a higher ecological risk than the other two land use types. Industrial discharges (32.8%), agricultural inputs (22.6%), natural sources (23.7%), and traffic emissions (20.9%) were the primary PTE sources in the tested soils, which indicate that anthropogenic activities have significantly affected soil PTE contents to a greater extent than other sources. Industrial discharge was the most prominent source of non-carcinogenic health risk, contributing 37.7% for adults and 35.2% for children of the total risk. The results of PLS-PM revealed that land use change associated with intensive human activities such as industrial activities and agricultural practices distinctly affected the PTE contents in soils of the Qinghai-Tibet Plateau.