Source identification of eight heavy metals in grassland soils by multivariate analysis from the Baicheng-Songyuan area, Jilin Province, Northeast China

Fractionation, chemometric analysis, and sophisticated risk assessment indices to appraise sediment contamination of a tropical mangrove forests, the Red Sea

This paper adds a new perspective to Ras Mohamed Protectorate mangrove sediment quality studies in terms of bioavailability, mobility, human and eco-environmental risk of various potential toxic elements (PTEs). Fe > Mn > Pb > Cu > Cd was the order in which the PTE levels declined. Residual fraction controlled the geochemical speciation of all elements. The following was the order of the mean percentages of mobile elements in sediments: Mn > Fe > Pb > Cu > Cd. All sediment samples had low to moderate risk, according to synergistic indices (GCF, mRAC, PETI-A and PTEI-B). Mn was the primary ecological risk PTE contributor. According to the suggested individual indices, Mn is the most mobile and bioavailable element (0.4-1), whereas Cd, Cu, Fe, and Pb have moderate mobility and bioavailability (MI 0.1-0.4 and BI 0.1-0.4, respectively). The current PTE exposure in sediments did not constitute a significant health concern (THQ < 1 and LCR < 10-4).

Geochemical background of some trace elements in Atlantic Forest soils in a cocoa-producing region and its implications for human health and food safety

The background values for trace elements (TEs) in soils are crucial for environmental monitoring and food safety, as establishing quality reference values (QRVs) and help distinguish natural from anthropogenic sources. Brazil is the sixth-largest cocoa producer globally, with plantations concentrated in northeast and north regions. However, data on natural TEs concentrations in soils remain scarce, posing a significant challenge for food safety, human health, and environmental regulations. This study aims to determine natural TEs concentrations and establish QRVs for selected elements. Surface soil samples were collected from 38 native forest units and analyzed using exploratory, univariate, and multivariate statistical methods. Compared to soils around the world and from northern and northeastern Brazil, Ba and Cd (66.8 and 2.7 mg kg-1, respectively) exhibited the highest mean concentrations, except when compared to European soils. The results highlight that TEs concentrations in Atlantic Forest soils of southern Bahia differ due to geological diversity. Pedogenetic processes influenced TEs distribution, following the order: Fe > Ti > Ba > V > Cr > Zn > Cu > Co > Ni > Pb > Cd > Sb > Mo. QRVs were established using the 75th and 90th percentiles. Future research could integrate ecological and human health risk indices in cocoa-cultivated areas, considering soil, litter, plant tissues, and almonds. This approach would enhance understanding of TEs behavior under varying edaphic conditions, ultimately strengthening environmental monitoring strategies and food safety regulations.

Safe utilization of cadmium-rich soil for planting lilies and maize using a random forest model based on soil properties

The factors influencing the uptake of soil Cd by crops are complex and closely related to the different crop varieties. Efficient and safe utilization of land resources with high soil Cd levels has become a significant challenge in the scientific community. This study focuses on the anomalously high Cd distribution area in the northern part of Longshan County, Hunan, China. By systematically collecting and testing Cd content in the edible parts of lily and maize, as well as corresponding root soil Cd, pH, and oxides, the study reveals the differences in the bioconcentration factors of Cd (BCF-Cd) for lily and maize and their influencing factors. Using the random forest method and hyperparameter optimization, optimal prediction models for BCF-Cd in lily and maize were established. The results indicate that the BCF-Cd of lily is significantly higher than that of maize. The primary factors influencing BCF-Cd in lily and maize include soil pH, Mn, OM, and ba. Feature importance analysis identifies pH as the most critical factor affecting BCF-Cd in both lily and maize. Based on the prediction results of the random forest model, this study proposes a zoning scheme for the safe utilization of arable land to maximize benefits while ensuring the medicinal safety of lily and the food safety of maize. This provides scientific evidence for ensuring food security and maximizing the productive value of land resources.

Heavy metal pollution and probabilistic risk assessment in soil of desert road shelterbelts in typical oasis cities in Northwest China

The topic of this paper is the heavy metal pollution in desert road soil and the probability risk assessment of heavy metal pollution. The research topic adopts a quantitative analysis method to quantify the impact of soil heavy metal concentration and the contribution of soil heavy metal impact to human health risks. During the research process, surface soil collection was completed, with samples from two desert road protection forest belts in oasis cities. The assessment methods for heavy metal pollution levels include heavy metal migration factor, Nemero comprehensive pollution index, pollution index, and geochemical baseline value. The results confirm that there is a moderate risk of heavy metal pollution in the sample, but there is no overly obvious ecological risk. Zhongwei City has relatively severe Pb pollution, while Wuwei City has severe Cd pollution. Subsequently, based on Species Sensitivity Distribution as the basic support, the derivation and calculation of Predicted No Effect Concentration were completed, and the ecological risk was evaluated. The health risk assessment tools for different populations include health risk assessment models and Monte Carlo models. From the evaluation conclusion, the non-carcinogenic risk of Pb (adult: 99.98%; child: 99.98%) and As (adult: 54.28%; child: 98.11%) in the protective forest of Wuwei Desert is low, and the probability of carcinogenic risk is high. The results in Zhongwei are similar to those in Wuwei, both of which have a more serious health probability risk. From the derivation and calculation results, it can be seen that GB 36600-2018 (Soil Environmental Quality Standards) cannot protect species diversity well. The research conclusion can promote the analysis and control of environmental risks on desert highways from both theoretical and practical perspectives.

Black shale high geological background potential toxic elements(PTEs) in middle reaches of the Yangtze River tributary basin water environment, China: Distribution, pollution sources, and risk assessment

As a typical high geological background area in the middle reaches of the Yangtze River tributary basin in China, the Loushao Basin in Hunan is covered with high mineral black shale, with an average element value 4.76-8.97 times higher than the world average rock level. The aim of this study is to analyze the water environment pollution in the middle reaches of the Yangtze River tributary basin under high geological background based on the spatial distribution differences of black shale concentration. PCA source analysis is used to track the source of pollution and highlight the differences in body shape to assess regional health risks. The research results show that Cd in water quality exceeds the background value by 7.5 times. There is a strong homology among Pb, Cd, Cr, As, and Hg elements in water bodies, mainly derived from the natural weathering, migration, and enrichment of rocks. Hg element is a pollution caused by human factors, and water pollution is more severe in areas close to high concentrations, with severe exceedance of Cr element in water quality. The main controlling factor for individual health risk differences is body shape, and men's health is more susceptible to threats.

Using Sediment Bacterial Communities to Predict Trace Metal Pollution Risk in Coastal Environment Management: Feasibility, Reliability, and Practicability

The distribution of trace metals (TMs) in a continuous water body often exhibits watershed attributes, but the tidal gates of the coastal rivers may alter their transformation and accumulation patterns. Therefore, a tidal gate-controlled coastal river was selected to test the distribution and accumulation risks of Al, As, Cr, Cu, Fe, Mn, Ni, Sr, and Zn in the catchment area (CA), estuarine area (EA), and offshore area (OA). Associations between TMs and bacterial communities were analyzed to assess the feasibility of using bacterial parameters as ecological indicators. The results showed that As and Cr were the key pollutants due to the higher enrichment factor and geoaccumulation index, reaching slight to moderate pollution levels. The Nemero index was highest in EAs (14.93), indicating a higher pollution risk in sediments near tide gates. Although the TM dynamics can be explained by the metal-indicating effects of Fe and Mn, they have no linear relationships with toxic metals. Interestingly, the metabolic abundance of bacterial communities showed good correlations with different TMs in the sediment. These results highlight bacterial community characteristics as effective biomarkers for assessing TM pollution and practical tools for managing pollution control in coastal environment.

A remote sensing analysis method for soil heavy metal pollution sources at site scale considering source-sink relationships

Conventional methods for identifying soil heavy metal (HM) pollution sources are limited to area scale, failing to accurately pinpoint sources at specific sites due to the spatial heterogeneity of HMs in mining areas. Furthermore, these methods primarily focus on existing solid waste polluted dumps, defined as "direct pollution sources", while neglecting existing HM pollution hotspots generated by historical anthropogenic activities (e.g., mineral development, industrial discharges), defined as "potential pollution sources". Addressing this gap, a novel remote sensing analysis method is proposed to identify both direct and potential pollution sources at site scale, considering source-sink relationships. Direct pollution sources are extracted using a supervised classification algorithm on high-resolution multispectral imagery. Potential pollution sources depend on the spatial distribution of HM pollution, mapped using a machine learning model with hyperspectral imagery. Additionally, a source identification algorithm is developed for gridded pollution source analysis. Validated through a case study in a cadmium (Cd)-polluted mine area, the proposed method successfully extracted 21 solid waste polluted dumps with an overall accuracy approaching 90 % and a Kappa coefficient of 0.80. Simultaneously, 4167 HM pollution hotspots were identified, achieving optimal inversion accuracy for Cd (Rv2 = 0.91, RMSEv = 4.27, and RPDv = 3.02). Notably, the spatial distribution patterns of these identified sources exhibited a high degree of similarity. Further analysis employing the identification algorithm indicated that 3 polluted dumps and 258 pollution hotspots were pollution sources for a selected high-value point of Cd content. This innovative method provides a valuable methodological reference for precise prevention and control of soil HM pollution.

Ecological risk and spatial distribution, sources of heavy metals in typical purple soils, southwest China

The identification and quantification of the ecological risks, sources and distribution of heavy metals in purple soils are essential for regional pollution control and management. In this study, geo-accumulation index (Igeo), enrichment factor (EF), pollution index (PI), potential ecological risk index (RI), principal component analysis (PCA) model and geographical detector (GD) were combined to evaluate the status, ecological risk, and sources of heavy metals (HMs) in soils from a typical purple soil areas of Sichuan province. The results showed that the average contents of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in purple soil were 7.77, 0.19, 69.5, 27.9, 0.077, 30.9, 26.5 mg/kg and 76.8 mg/kg, and the Igeo, EF and RI of topsoil Hg and Cd in designated area was the highest, and the average contents of Hg and Cd in topsoil were obviously greater than respective soil background value in Sichuan province and purple soil. The hot spots for the spatial distribution of 8 HMs were mainly focused in the southwest and northeast of the designated area, and there were also significant differences for 8 HMs distribution characteristics in the profile soil. Cu comes from both anthropogenic and natural sources, Zn, Ni and Cr mainly come from natural sources, but As, Pb, Hg and Cd mainly derived from human activities. GD results showed that soil texture (X18), altitude (X4), total nitrogen (TN), clay content (X3), sand content (X2) and silt content (X1) had the greatest explanatory power to 8 HMs spatial differentiation.This study provides a reference for understanding the status and influencing factors of HM pollution in typical purple soil, and lays a theoretical foundation for the environmental treatment of purple soil in China.

Determination of threshold values and heavy metal pollution assessment of soils in an industrial area in Ghana

Industrial activities have the potential to pollute soils with a wide variety of heavy metals (HMs). In Ghana, however, assessment of HM pollution of soils in industrial areas remains limited. Accordingly, HM soil pollution in one of the industrial areas in Accra, Ghana was assessed. Soil samples were taken and analysed for HMs, including Fe, Zr, Zn, Ti, Sr, Rb, Mn, Pb, Cu, and Co, using X-Ray Fluorescence (XRF). HM geochemical threshold values (GTVs) were determined to establish soil HM pollution levels and identify areas needing remediation. Furthermore, risk assessments were conducted to evaluate the potential ecological and human health risks associated with these metals. The mean concentrations of Fe, Zn, Rb, Sr, Zr, Ti, Mn, Co, Cu, and Pb in the soils were: 27133.83, 147.72, 16.30, 95.95, 307.11, 4663.66, 289.85, 418.54, 44.97, and 112.88 mg/kg, respectively. Generally, the concentrations of HMs decreased with depth, although some lower layers exhibited elevated HM levels. Soil pollution levels were categorized as low for Fe, Rb, Zr, Ti, Mn, Co, and Cu; moderate for Sr and Zn; and considerable for Pb. Notably, the northwestern part of the study area displayed a considerable to very high degree of HM contamination. While HMs in the soils posed low ecological risk, the human health risk assessment indicated potential health effects from Co, particularly in children. The presence of HMs in the soils was noted to originate from both natural geological phenomena and human activities, including industrial operations, agricultural practices, landfill activities, and vehicular emissions.

Heavy metals and Pb isotopes in sediment cores from the Bering and Chukchi seas: Implications for environmental changes and human activities over the past century

The Bering Sea and the Chukchi Sea are important regions for marine ecosystems and climate change. However, the historical deposition and sources of metals in these regions are poorly understood. In this study, we utilized Pb isotopes and multi-element concentrations (Ni, Cu, Fe, Mn, Zn, Cd, Pb) coupled with Pb-210 dating to investigate the historical deposition and source identification of metals in sediment cores collected from the Bering Sea and the Chukchi Sea. Our findings reveal that the transport of organic matter was mainly transported by marine and terrestrial sources in the Bering and Chukchi Sea, respectively. Historical variations of metals were similar in both seas, showing an increasing trend of metals (excluding Mn) from the 1960s to the 1990s, followed by a gradual decrease after the 1990s, which can be attributed to the development of industrial and gasoline emission. The results of the geo-accumulation index indicated that sediment in both seas was relatively unpolluted with metals. Additionally, Pb isotopic ratios suggested that natural weathering was the primary source of Pb in the area, but the use and phase-out of gasoline were also well-reconstructed. This study provides valuable information for assessing environmental changes and human activities over the past century in the Arctic and subarctic Ocean.

Accumulation, potential risk and source identification of toxic metal elements in soil: a case study of a coal-fired power plant in Western China

Coal-fired power plants (CPP) usually release massive numerous amounts of potentially toxic metal(loid)s (PTMs) into nearby ecosystems. There have been relatively few studies targeted on the ecological influences of PTMs related to the CPP in arid area. In this work, the distribution pattern, source apportionment and environmental risks of As, Cd, Cr, Hg, Pb and a couple of seldom monitored PTMs (Se, Zn, Co, Cu, Fe, Mn and Ni) in the soils near a coal electricity integration base were investigated in Hami, a city in northwestern China. Nemerow synthesis pollution index, geo-accumulation index and ecological risk index were used to assess pollution state of these PTMs in soils, and ordinary Kriging interpolation was used to analyze the spatial distribution for these elements. Methods of CA, PCA, CA and PAM were carried out for quantitative source analysis. The research outcome includes: (1) the contents of individual PTMs in most samples were greater than the background values, the pollution degrees of Se, Pb, Hg, Cd and As were significant, and some areas exceeded the warning threshold value; (2) the main sources of these PTMs were natural sources (35%), coal mine sewage (11%), atmospheric release during coal combustion (21%), dust generated from coal and combustion products (33%); (3) attention should be paid to the open-pit coal mines, shaft coal mines and ash dumps where the contents of metal elements were significantly polluted; and (4) wind is the main driving forces of PTMs migration in arid areas.

Quantifying ecological and human health risks of heavy metals from different sources in farmland soils within a typical mining and smelting industrial area

The quality of food crops and human health is threatened by heavy metals (HMs) accumulated in farmland soils for a long time. In this study, we selected 148 soil samples randomly from farmlands in a region featuring abandoned lead-zinc (Pb-Zn) mining activities with the aim to quantify the pollution risk and identify potential sources of heavy metals, based on a case in the southwestern of China. The median contents of metals, such as Pb, Zn, Cd, As, Cu and Cr, are above the background values for Chinese soils and prescribed pollution threshold guide values (GB15618-2018), except Hg and Ni. The farmland soils in sites surrounding areas with previous Pb-Zn mining and smelting activities were classified as seriously polluted. Pollution sources were evaluated using GIS-based geostatistical methods, multivariate statistical analyses and positive matrix factorization (PMF) modeling. Four sources were quantitatively apportioned, which were industrial sources such as mining and smelting (53.1%), agricultural practices (11.6%), natural source (21.6%) and other industrial sources such as electroplating (13.7%). The potential risks of contamination associated with the heavy metals were evaluated using several indices including the Nemerow, geoaccumulation (Igeo) and ecological risk (RI) indices. Based on the Igeo index, As and Pb were the most severe pollutants among all of those measured. With the combination of the potential ecological risk index (RI) and human health risk (HHR) assessment models, the ecological risk and HHR from different sources were analyzed quantitatively. Industrial activities such as mining and smelting were the greatest contributors to ecological risk, non-carcinogenic risk and carcinogenic risk, accounting for about 86.9%,73.9% and 81.9%, respectively. Additionally, the health risks of children were more serious relative to those of adults from the perspective of non-carcinogenic and carcinogenic risks.

Combination of enrichment factor and positive matrix factorization in the estimation of potentially toxic element source distribution in agricultural soil

The study intended to assess the level of pollution of potential toxic elements (PTEs) at different soil depths and to evaluate the source contribution in agricultural soil. One hundred and two soil samples were collected for both topsoil (51), and the subsoil (51) and the content of PTEs (Cr, Cu, Cd, Mn, Ni, Pb, As and Zn) were determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The concentrations of Zn and Cd in both soil horizons indicated that the current study levels were higher than the upper continental crust (UCC), world average value (WAV), and European average values (EAV). Nonetheless, the concentration values of PTEs such as Mn and Cu for EAV, As, Cu, Mn, and Pb for UCC, and Pb for WAV were lower than the average values of the corresponding PTEs in this study. The single pollution index, enrichment factor, and ecological risk revealed that the pollution level ranged from low to high. The pollution load index, Nemerow pollution index, and risk index all revealed that pollution levels ranged from low to high. The spatial distribution confirmed that pollution levels varied between the horizons; that is, the subsoil was considered slightly more enriched than the topsoil. Principal component analysis identified the PTE source as geogenic (i.e. for Mn, Cu, Ni, Cr) and anthropogenic (i.e. for Pb, Zn, Cd, and As). PTEs were attributed to various sources using enrichment factor-positive matrix factorization (EF-PMF) and positive matrix factorization (PMF), including geogenic (e.g. rock weathering), fertilizer application, steel industry, industrial sewage irrigation, agrochemicals, and metal works. Both receptor models allotted consistent sources for the PTEs. Multiple linear regression analysis was applied to the receptor models (EF-PMF and PMF), and their efficiency was tested and assessed using root-mean-square error (RMSE), mean absolute error (MAE), and R² accuracy indicators. The validation and accuracy assessment of the receptor models revealed that the EF-PMF receptor model output significantly reduces errors compared with the parent model PMF. Based on the marginal error levels in RMSE and MAE, 7 of the 8 PTEs (As, Cd, Cr, Cu, Ni, Mn, Pb, and Zn) analysed performed better under the EF-PMF receptor model. The EF-PMF receptor model optimizes the efficiency level in source apportionment, reducing errors in determining the proportion contribution of PTEs in each factor. The purpose of building a model is to maximize efficiency while minimizing inaccuracy. The marginal error limitation encountered in the parent model PMF was circumvented by EF-PMF. As a result, EF-PMF is feasible and useful for apparently polluted environments, whether farmland, urban land, or peri-urban land.

Distribution, bioavailability, and ecological risk assessment of potentially toxic heavy metals in El-Burullus Lake sediments, Egypt

El-Burullus Lake is the second largest coastal lagoon in Egypt in addition to its connection to the Mediterranean Sea. In this study, geochemical fractionations of heavy metals (Fe, Pb, Cd, Cu, Cr and Zn) were investigated after the great efforts made to rehabilitate and restore the lake by the Egyptian Government. The results indicated that F4 (residual fraction) was the dominant fraction for all studied metals followed by F3 (oxidizable fraction). That means the majority of studied metals source in the lake is lithogenic. Contamination by each individual heavy metal or multi elements was low according to individual contamination factor (ICF) and global contamination factor (GCF). Risk assessment code (RAC) classification showed that Cd and Cu exhibited low risk, Zn was of moderate risk, whereas, other metals are safe. The toxicity calculated by toxic risk index (TRI) indicating that no toxic risk was expected in the Lake.

Source Apportionment and Model Applicability of Heavy Metal Pollution in Farmland Soil Based on Three Receptor Models

The identification of the source of heavy metal pollution and its quantification are the prerequisite of soil pollution control. The APCS-MLR, UNMIX and PMF models were employed to apportion pollution sources of Cu, Zn, Pb, Cd, Cr and Ni of the farmland soil in the vicinity of an abandoned iron and steel plant. The sources, contribution rates and applicability of the models were evaluated. The potential ecological risk index revealed greatest ecological risk from Cd. The results of source apportionment illustrated that the APCS-MLR and UNMIX models could verify each other for accurate allocation of pollution sources. The industrial sources were the main sources of pollution (32.41~38.42%), followed by agricultural sources (29.35~31.65%) and traffic emission sources (21.03~21.51%); and the smallest proportion was from natural sources of pollution (11.2~14.42%). The PMF model was easily affected by outliers and its fitting degree was not ideal, leading to be unable to get more accurate results of source analysis. The combination of multiple models could effectively improve the accuracy of pollution source analysis of soil heavy metals. These results provide some scientific basis for further remediation of heavy metal pollution in farmland soil.

A spatial distribution - Principal component analysis (SD-PCA) model to assess pollution of heavy metals in soil

With the rapid development of urbanization, heavy metal pollution of soil has received great attention. Over-enrichment of heavy metals in soil may endanger human health. Assessing soil pollution and identifying potential sources of heavy metals are crucial for prevention and control of soil heavy metal pollution. This study introduced a spatial distribution - principal component analysis (SD-PCA) model that couples the spatial attributes of soil pollution with linear data transformation by the eigenvector-based principal component analysis. By evaluating soil pollution in the spatial dimension it identifies the potential sources of heavy metals more easily. In this study, soil contamination by eight heavy metals was investigated in the Lintong District, a typical multi-source urban area in Northwest China. In general, the soils in the study area were lightly contaminated by Cr and Pb. Pearson correlation analysis showed that Cr was negatively correlated with other heavy metals, whereas the spatial autocorrelation analysis revealed that there was strong association in the spatial distribution of eight heavy metals. The aggregation forms were more varied and the correlation between Cr contamination and other heavy metals was lower. The aggregation forms of Mn and Cu, Zn and Pb, on the other hand, were remarkably comparable. Agriculture was the largest pollution source, contributing 65.5 % to soil pollution, which was caused by the superposition of multiple heavy metals. Additionally, traffic and natural pollution sources contributed 17.9 % and 11.1 %, respectively. The ability of this model to track pollution of heavy metals has important practical significance for the assessment and control of multi-source soil pollution.

A Monte Carlo simulation-based health risk assessment of heavy metals in soils of an oasis agricultural region in northwest China

In recent years, heavy metal contamination of soils has been increasing, posing a major threat to food security, human health, and soil ecosystems. This study analyzed the spatial characteristics, contamination sources, risks of heavy metals by collecting topsoil samples from farmland in an oasis agricultural region in northwest China. The results found that soil heavy metals in farmland were at a moderate contamination level. The PMF model classifies soil heavy metals as fertilizer and pesticide sources dominated by As and Mn with 27.8 %, mixed sources of transport and agricultural sources dominated by Cu, Zn, Cd and Pb with 26.9 %, metal processing sources dominated by Cr and Ni with 22.6 %, and the combined pollution sources of Ti, V, Cr, Mn, Fe, As, Pb dominated by natural sources and fuel combustion. The noncarcinogenic and carcinogenic risks values from the ingestion route were higher for children than for adults. The non-carcinogenic risk of heavy metals to adults in the southwestern and central regions of the study area was >1 × 10^-4. The carcinogenic risk was >1 in all adults, but >1 in children in the central and southwestern study areas. Monte Carlo simulation takes into account the parameters and their distributions that affect the health risk assessment model by combining the uncertainty assessment with the health risk, which will reduce the uncertainty of the health risk assessment. The results showed that conventional deterministic risk assessment may overestimate health risk outcomes. In addition, As has a 1.85 % probability of non-carcinogenic risk to children, and an 85.3 % probability of total non-carcinogenic risk for children for all heavy metals. 69.5 % and 11.4 % probability of carcinogenic risk for children and adults respectively for Ni, and 96.4 % and 52.1 % probability of total carcinogenic risk, suggesting that Ni is a priority control heavy metal.

Comprehensive assessment of heavy metals in soil-crop system based on PMF and evolutionary game theory

The traditional assessment of farmland environmental quality usually focuses on soil heavy metals, but ignores agricultural produce safety. It is urgent to comprehensively assess the effects of farmland environmental quality based on soil quality and produce safety. To fill this gap, the comprehensive assessment method was improved based on previous studies, which was used to assess the pollution level of heavy metals in soil-crop system of Shenyang, Liaoning Province, Northeast China. In addition, this study also made a comprehensive analysis of pollution sources based on positive matrix factorization (PMF) model, and discussed soil-crop system income stability by evolutionary game theory. The mean concentrations of As, Cd, Cr, Hg, Pb, Cu, Zn, and Ni in soil exceeded the corresponding Shenyang soil background values (5.68 %, 14.36 %, 57.61 %, 7.86 %, 30.32 %, 5.21 %, 211.72 %, 171.88 %). The results showed that about 28.28 % of paired soil-crop points were polluted by heavy metals, especially rice-soil points. Furthermore, heavy metals in crops may be transmitted less from soil and more from other environmental media. The PMF analysis results showed that there were six pollution sources in study area, and the major contributor of pollution were agricultural activities, traffic-related activities, and industrial activities. In farmland environment protection, the only stable strategy is soil-crop system, and soil-crop system is better than the benefits of single soil or crop from the perspective of benefits. This study provides a scientific and reliable method to combine soil quality with produce safety to assess the risk of heavy metals in farmland.

Assessment of Metal Contamination in Water of Freshwater Aquaculture Farms from a South Asian Tropical Coastal Area

Heavy metal accumulation in aquaculture farms has become a major problem due to the widespread use of artificial feed to enhance fish productivity. To estimate the contamination level and identify metal sources, we investigated the amounts of seven heavy metals (Cu, Zn, Pb, Cd, Cr, Ni, and Mn) in the surface water of commercial fresh water aquaculture farms in a south Asian tropical coastal area. Atomic absorption spectrometry (AAS) was used to analyze 36 water samples from 12 commercial fish farms. The results demonstrated that the range of three heavy metals were detected in a decreasing order of Mn (0.0574−0.4100 mg.L−1) > Zn (0.0125−0.3250 mg.L−1) > Cu (0.0275−0.085 mg.L−1). In all samples, the remaining four heavy metals (Pb, Cd, Cr, and Ni) were below the detectable level (BDL). Except for Mn, the amounts of the metals examined were below WHO and USEPA guideline values. According to the findings, the levels were found to be safe for drinking, agriculture production, and aquaculture. There was no significant correlation (p > 0.05) between heavy metal concentrations and water quality parameters, indicating that pollution came from diverse sources and that no single factor was controlling their levels. Furthermore, Analysis of Variance (ANOVA) revealed no significant differences in the mean metal values among the fish farms (p > 0.05). Multivariate analyses (CA and PCA) demonstrated the association and sources of metal in the study area. Although metal levels were not beyond the threshold limit, it is recommended that suitable measures and continuous monitoring should be undertaken to reduce heavy metal pollution in aquaculture farms and prevent water quality degradation.

Risk assessment of trace elements accumulation in soil-herbage systems at varied elevation in subalpine grassland of northern Tibet Plateau

Ecological environment of remote grassland has become a problem in many countries due to mining, tourism, grazing, and other human activities. In this study, a total of 15 pairs of soil-herbage samples were collected in the northeast of the Tibet Plateau to study the relationship between physicochemical properties and content of trace elements in soils at different elevation, and to examine the accumulation and fractionation of heavy metals in soil-herbage systems. In addition, the ecological risk of the subalpine grassland was also assessed. The average concentrations of Hg, As, Cu, Zn, Pb, Cd, Cr, and Mn in soil were higher than their background values of Gansu soil, but the average concentrations of these heavy metals in herbage satisfied Hygienical Standard for Feeds. The speciation analysis of heavy metals in soil indicated that the exchangeable content of heavy metal was very low, except Pb, Cd, and Mn. There was a linear relationship between pH, CaCO₃, total phosphorus (TP), organic matter (OM), concentrations of Hg, As, Zn, Pb, Cr, and Mn in soils, dry weight of herbage, and elevation, while there was a quadratic curve trend between Cu, Cd in soils, and elevation. The results of risk assessment showed that there was no obvious ecological risk in the study area.

Evaluating a Sampling Regime for Estimating the Levels of Contamination and the Sources of Elements in Soils Collected from a Rapidly Industrialized Town in Guangdong Province, China

Gaogang Town, a typical urban center within the Pearl River Delta region of China, suffers contamination of soils with metals/metalloids due to rapid development of industrial activities and agriculture. Few studies have been conducted to systematically describe the main sources, influencing factors, and ecological risks of metals/metalloids in soils in China. In this study, 312 surface soil samples were collected, and 15 elements were detected by plasma emission spectroscopy, atomic fluorescence spectroscopy, and atomic emission spectrometry. Element content features were analyzed by index of geo-accumulation (I_geo), pollution load index (PLI), potential ecological risk index (RI), positive matrix factorization model (PMF), and geostatistical analysis. The PLI value is between 0 and 1, indicating that the whole study area is lightly polluted. Combining PMF model and geostatistical analysis, soil elements in surface soils of Gaogang town were quantitatively apportioned into four sources: parent material and basic substances (23.5%), natural sources (32.2%), agricultural activities and industrial pollution (22.9%), and transportation (21.4%). The comprehensive analysis results show that polluted areas are mainly distributed on roads, rivers, and industrial and human activity areas. The main sources of ecological risks are factory pollution and human activity. Finally, we found that a quarter of the sampling density was the best sample size for this study.

Composition, environmental implication and source identification of elements in soil and moss from a pristine spruce forest ecosystem, Northwest China

The environmental quality of remote alpine ecosystem has been drawn increasing attention owing to the increasingly severe atmospheric pollution. This study investigated the composition and sources of elements in the soil and moss collected from a pristine spruce forest in the Qilian Mountains, Northwest China. The order of mean concentrations of elements investigated in soil was Fe > K > Na > Mg > Ca > Mn > Cr > Zn > Pb > Ni > Cu > As > Cd > Hg, and that of moss was Ca > Fe > Mg > K > Na > Mn > Cr > Zn > Pb > Ni > Cu > As > Cd > Hg. The concentrations of trace metals (except for As) in soil were greater than the soil background values, with Pb contamination more serious than the other elements. The Nemerow integrated pollution index (NIPI) values indicated that the soils were heavily polluted by Pb, Cd and Ni. The potential ecological risk index (PERI) suggested that the soils were at moderate risk. In particular, Hg and Cd were the most critically potential factors for ecological risk. According to the bioaccumulation factors (BAF), the accumulated concentrations of Ca, Hg, Cd, Pb, Ni, Mg, Cr and Zn in moss were higher than those in soil. By performing the multivariate analyses, natural sources (airborne soil particles) were identified to be the major contributors for all elements, whereas anthropogenic sources also contributed to the accumulations of Pb and Cd in the soil and moss in this region.

Heavy metal accumulation and genotoxic effect of long-term wastewater irrigated peri-urban agricultural soils in semiarid climate

Water scarcity is becoming an alarming issue in the Mediterranean countries. Therefore, using the treated wastewater in the irrigation is considered as a valuable option. However, uncontrolled and long-term irrigation by wastewater leads to human health and environmental damages, mainly related to some specific pollutants. The assessment of the availability and toxicity of the heavy metals after long term irrigation, under semi-arid climate, is not yet well documented. In this study, physicochemical properties, genotoxicity (Vicia faba micronucleus test), total and available (CaCl₂-extractable) concentrations of Cr, Pb, Cu, Zn, Co and Cd in eight soils of peri-urban farms irrigated with wastewater were examined to evaluate their accumulation. The results indicated that long-term irrigation with wastewater induced significant increase of electrical conductivity, organic matter, calcium carbonate equivalent and nutrient availability. Total and available concentration of heavy metals were significantly higher (P < 0.05) in irrigated soils by wastewater. The total concentrations of Zn, Pb, Cu, Cr, Cd and Co in irrigated soils by wastewater at 0-40 cm depth were 85.69, 43.94, 34.86, 14.62, 9.94 and 7.17 mg kg^-1, respectively. Furthermore, the increase of the available metal fraction in irrigated soils by wastewater at 0-40 cm depth followed the following order: Co (1270.1%) > Cd (914.5%) > Cu (881.5%) > Cr (471.2%) > Pb (230.8%) > Zn (223.8%). The micronucleus assay indicated significant increase of micronucleus frequencies (41.25‰, 35.48‰, 21.66‰, 16.23‰ and 13.62‰ respectively for P1, P2, P3, P4 and P7) which were higher than the negative control (0‰) and the irrigated soil by fresh water (3.29‰). The micronucleus induction was significantly correlated with the high available fraction of Cd, Co and Zn at P1, P2 and P7. The genotoxicity can be a powerful test to assess the ecological effects associated with the interactions of heavy metals with other pollutants.

Research trends and frontiers on source appointment of soil heavy metal: a scientometric review (2000-2020)

In recent years, source appointment of soil heavy metal has attracted growing attention. However, few studies have attempted to make a comprehensive and systematical review on this topic. For this reason, a total of 1051 publications were retrieved from the Web of Science (WOS) database between 2000 and 2020. A scientometric analysis was carried out to reveal the characteristics of publications, research power, and research hotspots. CiteSpace was used to visualize and summarize the information about the development in this field. The results showed that (1) the number of publications in source appointment of soil heavy metal had increased rapidly; Environmental science and ecology and environmental sciences were top 2 most popular subject categories; (2) Research power was mainly distributed in Asia, Europe, and North America. China and Chinese Academy of Sciences were the most productive country and institution in terms of publications in this field. Biao Huang (China) was the most productive author. However, Hakanson L (Sweden) was the most influential author in terms of citation frequency; (3) Heavy metal, source identification, and contamination were the most frequent keywords. Keyword clustering analysis showed that the research hotspots mainly concentrated on air pollution, bioremediation, spatial distribution, soil, PCA, and so on; (4) Keyword bursts analysis showed that the research frontiers mainly focused on spatial analysis of soil heavy metal and exposure risk to human health.

Spatial heterogeneity of pH and heavy metal Cd in the soils of tea gardens in the plateau mountain regions, PR China

To explore the spatial heterogeneity of pH and cadmium (Cd) content in the soils of the tea gardens in the plateau mountain regions as well as its driving factors, the pH values, Cd content and other physical and chemical indicators from 423 soil samples were examined. A coefficient of variation method and a semivariance function model was adopted to explore the soils' spatial heterogeneity, and a random forest approach was applied to evaluate the factors influencing environmental Cd under different pH values. The results show that the pH values of the soils of the tea gardens in the plateau mountain regions were within the appropriate range for the growth of tea plants, and soil samples with pH values falling between 4.5 and 6.0 account for 74% of all samples. A comparison against the criteria of risk screening values for the contamination of agricultural land, a component of quantifying soil environmental quality in China, was preformed; it was determined that the content of heavy metal Cd in the soil of the tea gardens did not exceed the limit. The content of soil pH in the research area gradually declined from southwest to northeast, exhibiting two distinct parallel distribution zones running along the southwest-northeast direction. The spatial distribution of the heavy metal Cd content in the soil showed a gradually decreasing trend from north to south, with low-value polygons dominantly appearing in the southeasternmost area and high-value polygons concentrated in the north. When the soil pH ≤ 5.5, it had the largest effect on the Cd content; when 5.5 < pH ≤ 6.5, the physical indicators in soil had a relatively larger impact on the Cd content.

A simple electrochemical sensor based on rGO/MoS2/CS modified GCE for highly sensitive detection of Pb(ii) in tobacco leaves

High-performance electrode modification materials play a crucial role in improving the sensitivity of sensor detection in electrochemical determination of heavy metals. In this study, a rGO/MoS₂/CS nanocomposite modified glassy carbon electrode (GCE) was used to construct a sensitive sensor for detecting lead ions in tobacco leaves. The reduced graphene oxide (rGO) was used to increase the conductivity of the sensor, and the nano-flowered MoS₂ could provide a large reaction specific surface area and a certain active site for heavy metal reaction. Chitosan (CS) was used to improve the enrichment ability of heavy metals and increase the electrocatalytic activity of electrode. Thus, an electrochemical sensor with excellent performance in reproducibility, stability and anti-interference ability was established. The stripping behavior of Pb(ii) and the application conditions of the sensor were studied by square wave anodic stripping voltammetry (SWASV). The investigation indicated that the sensor exhibited high detection sensitivity in the range of 0.005-0.05-2.0 μM, and the limit of detection (LOD) was 0.0016 μM. This work can provide a fast and effective method for determination of Pb(ii) in samples with low content, such as tobacco leaves.

Spatial distribution, ecological risk and sources of heavy metals in soils from a typical economic development area, Southeastern China

Identification and quantification of the distribution, ecological risk, and sources of heavy metals in soils are essential for regional pollution control and management. In this study, spatial analysis (SA), GeogDetector model (GDM), and positive matrix factorization (PMF) model were combined to evaluate the status, ecological risk, and sources of heavy metals in soils from a typical coastal economic development area in Southeastern China. The mean contents of Cd, Pb, Cr, Cu, and Zn in the surface soils (0-20 cm) were 0.45, 41.72, 90.50, 47.86, and 145.33 mg/kg, respectively. In accordance, the mean contents of Cd exceeded the risk screening value for contamination of agricultural soil in China. Our results revealed that industrial and residential soils had higher enrichment of heavy metals than agricultural and fallow soils. Industrial production was the major driving factors influencing the spatial distribution of heavy metals. Soil OM and pH were found to be the most important factors affecting the potential ecological risk of heavy metals, followed by distance from the industrial enterprises and roads. Heavy metals in the study area were mainly originated from industrial emissions/atmospheric deposition, agricultural sources, and followed by natural sources. Therefore, regular monitoring and source control for heavy metals, especially for Cd, along with the integrated soil environmental management in the study area are crucial to ensure soil health and ecosystem security.

The Monitoring of Selected Heavy Metals Content and Bioavailability in the Soil-Plant System and Its Impact on Sustainability in Agribusiness Food Chains

This study assisted in identifying and preventing the increase in heavy metals in soil and winter wheat. Its accumulation can affect cultivated crops, quality and crop yields, and consumers’ health. Selected heavy metals were analyzed using the GTAAS method. They were undertaken on selected heavy metals content (Cd, Cu, Pb, and Zn) in arable soils at three sites in Slovakia and their accumulation in parts of cultivated winter wheat. Our study showed that the limit value of Cd in soil samples was exceeded in the monitored arable soils from 2017–2019. The average content values of Cu and Zn did not exceed the limit values, even in Pb values (except for the spring period). The analyses also showed that the heavy metals content for plants bioavailable in soil did not exceed the statutory critical values for Cd, Cu, and Zn’s average content values. However, Pb content exceeded permitted critical values. Heavy metals bioaccumulation (Zn, Cu) was within the limit values in wheat. Analyzed Cd content in wheat roots and Pb content were determined in all parts of wheat except grain. The study showed that grain from cultivated winter wheat in monitored arable soils is not a risk for consumers.

Plastic shed production systems: The migration of heavy metals from soil to vegetables and human health risk assessment

Plastic shed production system (PSPS) provide abundant vegetable products for human consumption. Comprehensive and accurate heavy metal (HM) risk assessment of soil and vegetable under plastic sheds is crucial for human health. Pollution assessment, bioavailability and mobility evaluation and health risk assessment of Cd, Cr, Cu, Zn Ni, Pb, and As were performed in a presentative Plastic shed production system. The concentrations of the Cd, Cu and Zn exceeded their background value. Positive I_geo values suggested that soil under plastic sheds was widely contaminated with Cd. The bioavailability of heavy metals in soils was evaluated using DTPA extraction and DGT methods. The results of both methods demonstrated that Cd, Cu, and Zn have high bioavailability, especially Cd. Analogically, the results of mobility assignment based on DIFS showed that Cd has a high migration risk due to the large available pool. Based on specific cultivation and management patterns of plastic shed production system, pH reduction and salt and nutrient accumulation may increase the heavy metals migration risk in soil under plastic sheds, while a high organic matter content may reduce the heavy metals migration risk. The average concentrations of Cd, Cr, Cu, Zn, Ni, Pb, and As in vegetables were 0.023, 0.226, 0.654, 2.984, 0.329, 0.041, and 0.010 mg/kg, respectively. All samples were well below the threshold. The order of target hazard quotient of different heavy metals caused by vegetable consumption was Cd > Cr > As > Cu, Ni, Pb, Zn, and the average total hazard index value was below 1, which demonstrated that risk of vegetable consumption in the study area. However, due to its high concentration and transfer coefficient in spinach, Cd might pose a health risk to humans, which requires special attention. In this study, Cd caused a significant issue than other HMs, whether pollution level, health risk and migration risk. DGT and DIFS can be used as an effective evaluation tool in the research of controlling heavy metals migration in soil-crop systems.

Accumulation and health implications of metals in topsoil of an urban riparian zone adjacent to different functional areas in a subtropical city

The riparian zone is a river-land ecotone, and its environmental conditions have a significant effect on the river ecosystem and population health. In this study, As, Cu, Cr, Cd, Mn, Fe, Ni, Pb, and Zn in the topsoils of urban riparian zones in a subtropical city in southeast China were quantitatively estimated by inductively coupled plasma-optical emission spectrometry. The geoaccumulation index and health risk evaluation model were adopted to assess the accumulation characteristic and health risk of residents' exposure to metals. Principle component analysis was used to determine the source of metals. The results showed that the mean contents of metals (except Fe) were higher than the soil background value, but none of the metal contents exceeded the mass limit of environmental quality standards. The order of the geoaccumulation index was Cd > Mn > Cu > Cr > Pb > Zn > As > Ni > Fe. The contamination level of Cd was classified as slight, whereas the other metals did not contribute to pollution. The spatial distribution of metals in the riparian zone was compatible with the pattern of functional zones in the adjacent urban areas, where levels of Cr, Cd, Fe, Mn, and Ni were higher in commercial areas, as were Pb and Zn in under-construction land and As in residential and industrial areas. Carcinogenic risks of Cr, As, and Pb were acceptable. The hazard index indicated no significant noncarcinogenic risks from any metals. However, noncarcinogenic risks of metals other than Mn were higher for children than for adults, and the primary exposure route of metal into the human body was ingestion for children and inhalation for adults. Principle component analysis indicated that the primary sources of Cr, Ni, Mn, Cu, and Fe were pedogenic processes and mineral weathering, whereas Zn, As, Pb, and Cd mainly originated from anthropogenic sources, specifically, Zn from transportation emission, Pb from transportation emission and industry waste, As from coal combustion and residential waste, and Cd from pigments/paint used in commercial buildings, urban greening, consumer waste, and transportation emission.

Polybrominated Diphenyl Ethers and Heavy Metals in a Regulated E-Waste Recycling Site, Eastern China: Implications for Risk Management

Serious pollution of multiple chemicals in irregulated e-waste recycling sites (IR-sites) were extensively investigated. However, little is known about the pollution in regulated sites. This study investigated the occurrence of 21 polybrominated diphenyl ethers (PBDEs) and 10 metals in a regulated site, in Eastern China. The concentrations of PBDEs and Cd, Cu, Pb, Sb, and Zn in soils and sediments were 1-4 and 1-3 orders of magnitude lower than those reported in the IR-sites, respectively. However, these were generally comparable to those in the urban and industrial areas. In general, a moderate pollution of PBDEs and metals was present in the vegetables in this area. A health risk assessment model was used to calculate human exposure to metals in soils. The summed non-carcinogenic risks of metals and PBDEs in the investigated soils were 1.59-3.27 and 0.25-0.51 for children and adults, respectively. Arsenic contributed to 47% of the total risks and As risks in 71.4% of the total soil samples exceeded the acceptable level. These results suggested that the pollution from e-waste recycling could be substantially decreased by the regulated activities, relative to poorly controlled operations, but arsenic pollution from the regulated cycling should be further controlled.

Spatial distribution and risk assessment of agricultural soil pollution by hazardous elements in a transboundary river basin

The present study aimed to evaluate the sources of pollution and the potential human and ecological risks of hazardous elements (HEs) in 40 hotspot sites of the agricultural soil around the Arvand River, Iran. The mean concentrations of As, Cd, Co, Cr, Ni, Pb, Zn, and Hg were measured to be 7.2, 0.8, 14.0, 67.9, 69.5, 63.0, 296, and 0.66 (mg kg^-1), respectively. With the exception of Ni, the mean concentrations of all the elements were found to be higher than those in the background. The spatial distribution of HEs in the study area indicated an increasing trend of contamination from the north to the south. Pb, Zn, and Hg were the most enriched elements, resulting in a high pollution load. Moreover, the agricultural soil of the study area was threatened by a very high ecological risk due to the contribution of Hg, Cd, and Pb. Multivariate statistical analyses determined that the pollution sources are specified by the oil refinery emissions and effluents, irrigation with polluted water, fertilizers, dust storms, and airport emissions. The carcinogenic risk of HEs in both adults and children revealed an acceptable level; however, children faced a great chance of non-carcinogenic risk. The results provide a scientific basis for monitoring HEs and managing health risks via effective methods in the agricultural areas of the Arvand River basin.

Ecological risk and early warning of soil compound pollutants (HMs, PAHs, PCBs and OCPs) in an industrial city, Changchun, China

Soil ecological risk caused by compound pollutants is a topic that deserves increasing attention, and soil risk early warning is a more in-depth discussion on this topic. In this study, we collected soil samples from Changchun, a typical industrial city, and determined the contents of 13 heavy metals (HMs) (0.00 mg kg^-1-6380 mg kg^-1), 16 polycyclic aromatic hydrocarbons (PAHs) (0.00 mg kg^-1-27.7 mg kg^-1), 7 polychlorinated biphenyls (PCBs) (0.30 μg kg^-1-168 μg kg^-1), and 8 organochlorine pesticides (OCPs) (0.00 mg kg^-1-4.52 mg kg^-1). The soil ecological risks of compound pollutants were assessed. The results showed that PAHs were the greatest risk pollutants, followed by PCBs and HMs, and OCPs were the smallest risk pollutants. Most of the ecological risks of compound pollutants were classified as "moderate severity" level according to the (contamination severity index) CSI evaluation criteria. With the help of modern industrial economic theory, through the analysis of the annual accumulation of pollutants, it is possible to predict the future pollutant content in Changchun, and the soil risks could be forewarned. The results showed that if active measures were not taken to reduce the accumulation of PAHs in Changchun soil, the CSI-PAHs would be classified as "ultra-high severity" level in 2035.

Comprehensive assessment of heavy metals pollution of farmland soil and crops in Jilin Province

As a major agricultural province in China, it is necessary to study the content of heavy metals in farmland soil and crop in Jilin Province and to evaluate the risks to ecology and human health. This study presented the work completed on 79 soil samples, 10 rice samples, 66 maize samples and 15 soybean samples collected from Jilin Province farmland and evaluated six heavy metals (Zn, Cu, Pb, Cd, Hg and As) concentrations. The results showed that the concentrations of the six heavy metals in farmland soil and crop samples from Jilin Province basically met the soil standards and food health standards of China. The agricultural soil pollution spatial distribution was the most serious in the south of Jilin Province and the lightest in the west. The non-carcinogenic risks faced by children eating crops were higher than those of adults, but the carcinogenic risks were lower than those of adults. Both of the two health risks to adults and children from eating crops were very limited. The results would help determine the heavy metals pollution in farmland soil in Jilin Province efficiently and accurately and helped decision makers to achieve a balance between production and environmental regulation.

Evaluation of heavy metal contamination and ecological risk of soil adjacent to Saravan municipal solid waste disposal site, Rasht, Iran

This study was performed on the soil of the Hyrcanian forests near Saravan municipal solid waste dumpsite, Rasht, Iran. In this research, the contents of metals (As, Pb, Cr, Cd, Cu, Hg, and Zn) were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The geoaccumulation index (I_geo), contamination factor (CF), and enrichment factor (EF), as well as pollution load index (PLI), were used to evaluate the metals contamination. The ecological risk factor ([Formula: see text]) and the potential ecological risk index (PERI) were applied to assess ecological risk. Pearson's correlation coefficients and the principal component analysis (PCA) were used to determine the possible origin of the metals. The metal concentrations were as follows: Zn > Pb > Cu > Cr > As > Cd > Hg. The results of the statistical tests showed that, except for Cr, the other elements had a significant difference with the control station (P < 0.05). The results of the Pearson's correlation coefficients, the PCA, and the I_geo revealed that the possible source of As, Hg, and Pb was the waste dumpsite activities and other anthropogenic origins, while Cd, Cu, Zn, and Cr probably have geogenic sources. The PLI was < 1, in unpolluted grade for all stations. The [Formula: see text] of the metals ranged as follows Hg > Cd > As > Pb > Zn, Cu > Cr, which implies that Cd and Hg play a key role in determining the ecological risk. The mean value of the PERI was 192.11 that represented a moderate ecological risk.

Current status, spatial features, health risks, and potential driving factors of soil heavy metal pollution in China at province level

In this study we systematically reviewed 1203 research papers published between 2008 and 2018 in China and recorded related data on eight kinds of soil heavy metals (Cr, Pb, Cd, Hg, As, Cu, Zn, and Ni). Based on that, the pollution levels, ecological risk and health risk caused by soil heavy metals were evaluated and the pollution hot spots and potential driving factors of different heavy metals in different provinces were also identified. Results indicated accumulation of heavy metals in soils of most provinces in China compared with background values. Consistent with previous findings, the most prevalent polluted heavy metals were Cd and Hg. Polluted regions are mainly located in central, southern and southwestern China. Hunan, Guangxi, Yunnan, and Guangdong provinces were the most polluted provinces. For the potential health risk caused by heavy metals pollution, children are more likely confront with non-carcinogenic risk than adults and seniors. And children in Hunan and Guangxi province were experiencing relatively larger non-carcinogenic risk. In addition, children in part of provinces were undergoing potentially carcinogenic risks due to soil heavy metals exposure. Furthermore, in our study the 31 provinces in mainland China were divided into six subsets according to corresponding potential driving factors for heavy metal accumulation. Our study provide more comprehensive and updated information for contributing to better soil management, soil remediation, and soil contamination control in China.

Geochemical background concentrations of potentially toxic elements in soils of the Carajás Mineral Province, southeast of the Amazonian Craton

The objective of this study was to establish background concentrations of potentially toxic elements (PTEs) in soils from the Carajás Mineral Province (CMP), southeastern Amazonian Craton. The PTEs Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V, and Zn were digested in microwaves and quantified by optical emission spectrometry (ICP OES). The variability of physical-chemical and mineralogical attributes contributed to variation in PTE concentrations. High background concentrations of Al, Fe, Cr, Mn, Mo, Ni, Ti, and V and, in particular, the PTE concentrations of Cd, Cu, Cr, Ba, and Co were greater than the prevention values defined by the Brazilian National Council of Environment. Soil quality reference values (QRVs) were greater than those determined for most Brazilian states and soils in the state of Pará. The high background concentrations and QRVs of PTEs show that the region is strongly influenced by the source material, rich in ferruginous deposits and other associated minerals. The results are an important tool for establishing soil quality standards and public policies for environmental protection in regions naturally PTE enriched.

Soil accumulation and chemical fractions of Cu in a large and long-term coastal apple orchard, North China

PURPOSE

Coastal orchards, with greater humidity and precipitation, are favorable for fruit production, as well as mildew fungi development, thus becoming hot spots of Cu concentrations in soils due to the use of copper-based fungicides. However, little is known on the variation tendencies of Cu availability and mobility from these soils. This study aims to investigate the accumulation, spatial-temporal distribution, and chemical fractions of soil Cu in one of the largest coastal apple-producing area with over 40-year intensive cultivation in China.

MATERIALS AND METHODS

A total of 104 orchard and 31 farmland topsoil samples were collected from Jiaodong Peninsula, Shandong Province. The total Cu concentration (T-Cu) and major element components (MnO, TiO₂, SiO₂, Fe₂O₃, and Al₂O₃) in the soil were determined by X-ray fluorescence spectroscopy. Available Cu concentration (A-Cu) was extracted with HCl or DTPA. Chemical fractionations of Cu were determined via sequential extraction method. The variation tendencies of T-Cu, A-Cu, Cu available ratio (AR), and chemical fractions with planting duration in the orchards were explored while a cokriging method was selected to predict their spatial distributions. Moreover, Pearson's correlation and multiple linear stepwise regressions were constructed to distinguish the vital factors in controlling Cu availability and mobility from these soils.

RESULTS AND DISCUSSION

The results showed that long-term application of Cu-containing fungicides had increased Cu concentrations in orchard soils (85.77 mg kg^-1) 3.5 times higher than the background value (24.0 mg kg^-1) of local agricultural soils, in which 23.8% existed in the available form. Cu in the weak acid-soluble fraction (F1, 5.0 ± 3.5 %), reducible fraction (F2, 24.7 ± 6.6%), and oxidizable fraction (F3, 18.5 ± 7.8%) in orchard soils increased significantly with increasing planting durations whereas the residual fraction (F4, 51.7 ± 15.4%) exhibited a reverse trend. Total content, available content, and chemical fractions of Cu showed strong spatial heterogeneity. The availability and mobility of Cu in orchard soils were mainly controlled by total Cu content, pH, and soil organic carbon.

CONCLUSIONS

Coastal orchards under warm and humid climate condition in China exhibited higher Cu input, along with acidification and rapid organic carbon turnover in the soils, eventually leading to large accumulation and high mobility of Cu in the soils.

Eutrophication and heavy metal pollution patterns in the water suppling lakes of China's south-to-north water diversion project

This study used non-supervised machine learning self-organizing maps (SOM) in conjunction with traditional multivariate statistical techniques (e.g., hierarchical cluster analysis, principle component analysis, Pearson's correlation analysis) to investigate spatio-temporal patterns of eutrophication and heavy metal pollution in the water supplying lakes (i.e., the Gao-Bao-Shaobo Lake, GBSL) of the eastern route of China's South-to-North Water Diversion Project (SNWDP-ER). A total of 28 water quality parameters were seasonally monitored at 33 sampling sites in the GBSL during 2016 to 2017 (i.e., 132 water samples were collected in four seasons). The results indicated that: 1) spatially, the western and south-western GBSL was relatively more eutrophic and polluted with heavy metals; and 2) temporally, the lakes suffered from high risks of heavy metal contamination in spring, but eutrophication in summer while water quality in winter was the best among the four seasons. Two main potential sources of pollution and transport routes were identified and discussed based on the pollution patterns. These findings contributed considerably to providing in-depth understanding of water pollution patterns, as well as potential pollution sources in the water-supplying region. Such understanding is crucial for developing pollution control and management strategies for this mega inter-basin water transfer project.

Mercury accumulation in soil from atmospheric deposition in temperate steppe of Inner Mongolia, China

Mercury (Hg) is a toxic and persistent pollutant and has long-term impacts on ecological systems and human health. Coal-fired power plants (CFPPs) are the main source of anthropogenic Hg emission, and the emitted atmospheric Hg is deposited to the surrounding environments which causes soil pollution. To assess the effects of atmospheric Hg from CFPPs in China on the temperate steppe, Hg contents in the topsoil and subsoil were analyzed for samples collected from 80 sites in central Inner Mongolia during 2012-2015. The average content of Hg in topsoil and subsoil were 14.9 ± 10.4 μg kg^-1 and 8.9 ± 5.8 μg kg^-1, respectively. The principal components analysis (PCA) indicated that the soil organic matter content and atmospheric deposition were the main factors determining soil Hg content in Inner Mongolia. We used the power plant impact factor (PPIF) to evaluate the impacts of the surrounding CFPPs. The PPIF results showed the most positive correlation with Hg content in topsoil at more than 400 km distances, indicating that the contribution of the long-range transport of Hg emitted from CFPPs is regional in scale. Considering the potential of Hg accumulation in soil, long-term and regional measurements of soil Hg and stricter emission-limit standards for power plants should be implemented to control soil Hg pollution in China.

Cycling and total risks of multiple As fractions in the Beijing-Tianjin-Hebei area on the agricultural plain, China

The high toxicity of As can cause serious health risks for humans; therefore, understanding the behavior of As in weakly alkaline soil conditions relevant to agricultural plains is important. To investigate the mobility and total risks of multiple fractions of As, 230 pairs of soil (including soil cores) and, wheat grain, and corresponding groundwater samples and 38 atmospheric deposition samples were collected from agricultural soil in the Beijing-Tianjin-Hebei region, China, which is a typical wheat-growing area. Seven fractions of As, namely, water-soluble (As1), exchangeable (As2), carbonate-bound (As3), humic acid-bound (As4), Fe-Mn oxide-bound (As5), organic matter-bound (As6), and residual (As7) As, were analyzed using a sequential extraction procedure to better understand and confirm the relationship among these different forms. Correlation and principal components analyses showed a significant relationship among As1-As5, and As in atmospheric deposits and As in groundwater and soil samples showed a positive relationship. As found in wheat, therefore, mainly originated from the soil and atmospheric deposits, and indirectly from the groundwater. As in the soil samples was mainly controlled by Mn and Fe₂O₃ based on the vertical distribution of soil cores and correlation analysis. The health risk assessments showed that As in the multiple fractions did not form a potential non-cancer risk for children and adults. However, residents could still face the risk of developing cancer by ingesting wheat and drinking the groundwater. The findings of this study have important implications for understanding the hydrological/geochemical behavior of As and the soil and water quality in a wide range of environmental settings. Additionally, our findings provided arguments for decreasing the concentrations of As in the wheat production system and to remind residents to decrease ingestion of their staple food (wheat) and drink less of the local groundwater.

Spatial distribution and ecological risk assessment of heavy metals in soil from the Raoyanghe Wetland, China

Wetlands are recognized as one of the most important natural environments for humans. At the same time, heavy metal pollution has an important impact on wetlands. China's Raoyanghe Wetland is one of the most important natural wild species gene banks in China. Eight heavy metal elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in surface layer and deep layer soils were analyzed using statistical-, pollution index-, and Nemerow index-based methods, the Hakanson potential ecological risk index method, and principal component and cluster analyses. The results showed that the maximum concentrations of heavy metals exceeded the background values in the core area and buffer zone of the wetland, but the heavy metal content of the soils was generally low and did not exceed 30%. With the exception of Hg, heavy metal concentrations showed strong spatial differentiation. The differences between the surface layer and deep layer soils of the core area were smaller than in the buffer zone. With the exception of Cd, a clear vertical zonation in the buffer zone soils was observed, showing greater evidence of external influences in this zone than the core. With the exception of partial surface soils, which indicated a safe level of pollution in the core area, all other soils were classified as having a ‘mild’ level of pollution. Thus, the wetland is moderately polluted, with both the core area and the buffer zone presenting a low level of potential ecological risk. According to the results of the present study, heavy metal contaminants in the wetland soils were found to be derived mainly from the natural sources.

Cd, Cu, and Zn Accumulations Caused by Long-Term Fertilization in Greenhouse Soils and Their Potential Risk Assessment

The intense management practices in greenhouse production may lead to heavy metal (HM) accumulations in soils. To determine the accumulation characteristics of HM and to evaluate possible HM sources in greenhouse soils, thirty typical greenhouse soil samples were collected in Shouguang District, Shandong Province, China. The results indicate that the Cd, Cu, and Zn concentrations are, respectively, 164.8%, 78.6%, and 123.9% higher than their background values. In the study area, Cd exhibits certain characteristics, such as wide variations in the proportion of its exchangeable form and the highest mobility factor and geo-accumulation index, which are indicative of its high bioavailability and environmental risk. In addition, there is a significant positive correlation between pairs of Cd, P, soil organic carbon, and cultivation age. Combined with principal component analysis, the results indicate the clear effects that agricultural activities have on Cd, Cu, and Zn accumulation. However, Cr, Ni, and Pb have a significant correlation with soil Fe and Al (hydr)-oxides, which indicates that these metals mainly originate from parent materials. This research indicated that long-term intensive fertilization (especially the application of chemical fertilizers and livestock manure) leads to Cd, Cu, and Zn accumulation in greenhouse soils in Shouguang. And the time required to reach the maximum permeable limit in agricultural soils for Cd, Cu, and Zn is 23, 51, and 42 years, respectively, based on their current increasing rates.

Pollution, Source, and Relationship of Trace Metal(loid)s in Soil-Wheat System in Hebei Plain, Northern China

To study the complex migration and transformation of trace metal(loid)s in a soil–wheat system, 225 pairs of surface soil and wheat samples were collected from the Taihang Mountains front plain, Hebei Province, northern China. The concentrations and pools (F1, water-soluble; F2, exchangeable; F3, carbonate-bound; F4, humic acid-bound; F5, Fe–Mn oxide-bound; F6, organic matter-bound; and F7, residual) of Cu, Pb, Zn, Cr, Ni, Cd, and Hg, and the soil properties of the samples were analyzed. The sum of the F1, F2, F3, and F4 proportions of Cd was higher than that of the other trace metal(loid)s, implying that Cd has greater mobility. We found a significant correlation (p < 0.01) between pools of trace metal(loid)s and the corresponding elements in wheat and a significant correlation (p < 0.01) between pools of trace metal(loid)s and pH, cation exchange capacity, clay, and total organic carbon. The results of principle component analysis (PCA)indicated that Cr, Ni and As mainly come from natural sources and Cu, Pb, Zn, and Cd from mixed groups related to farming and industry, Hg come from the coal burning. In addition, the total target hazard quotients showed the presence of harmful levels of trace metal(loid)s in wheat.

Source, Spatial Distribution and Pollution Assessment of Pb, Zn, Cu, and Pb, Isotopes in urban soils of Ahvaz City, a semi-arid metropolis in southwest Iran

This study examined the status of toxic metal contamination of the urban industrial city of Ahvaz in Iran. Two hundred and twenty-seven surface soils from a depth horizon of 0–10 cm were collected from urban areas. In addition, 15 soil samples were collected to recognise the sources of Pb in urban topsoils in Ahvaz city. Mean concentration of Pb, Zn, Cu and As were 181 ± 167, 123 ± 118, 185 ± 167 and 6.9 ± 8.9 mg.kg⁻¹, respectively. Results of inter-element relationship among studied toxic metals revealed that Pb, Zn and Cu may have the same anthropogenic origin, whilst As originated from different sources. The results of pollution index (PI) and Nemerow pollution index (NPI) implied that Pb, Zn, and Cu had a moderate to high level of pollution. The Pb isotopic composition analysis suggested clear anthropogenic origins of Pb including industrial emission, vehicle exhaust and dust storm with the mean contributions of 47%, 15% and 7%, respectively, by a four-end member model.

Heavy metals in agricultural soils from a typical township in Guangdong Province, China: Occurrences and spatial distribution

To investigate contamination level, origins and spatial distribution characteristics of heavy metals (Cu, Pb, Zn, Hg, Ni, Cd, As, and Cr) in agricultural soils of Gaogang Town, a typical industrial transfer-undertaking region of the Pearl River Delta (PRD), China, a total of 162 surface soil samples were collected in August 2016 and determined using inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry and atomic fluorescence spectrometry. Moreover, heavy metals contents were systematically analyzed by pollution index, enrichment factor, multivariate statistical approaches and geostatistical analysis. The results showed that the mean concentrations of Cd, Pb, Zn, Ni, Cu and Hg were higher than the soil background values of Guangdong Province, and the relatively high values of pollution index and enrichment factor indicated that these elements (Cd, Pb, Zn and Hg) had cumulative trends in soil. All results of multivariate statistical approaches and geostatistical analysis showed that pollution were heavily distributed in areas of industries, river and dense road network. The eight heavy metals in agricultural soils of Gaogang Town came from three different sources. Arsenic, Cr, Cu and Ni arose mainly from parent materials. Agricultural practices and traffic activities were the main sources of Cd, Pb and Zn. Mercury mainly came from industrial practices.

Risk-based assessment of soil pollution by potentially toxic elements in the industrialized urban and peri-urban areas of Ahvaz metropolis, southwest of Iran

The main purpose of this research was to assess the level of contamination, source identification, geochemical fractionation, and health risk of potentially toxic elements (PTEs) in industrial soils from urban and peri-urban areas of Ahvaz city. A total of 92 surface soil samples were gathered and concentrations of sixteen PTEs were measured using aqua regia digestion by an inductively coupled plasma mass spectrometry (ICP-MS). Possible sources of PTEs were quantitatively determined by positive matrix factorization (PMF) receptor model combined with geostatistical analyses and geochemical methods. The results showed that long-term industrial activities have enhanced the levels of some PTEs particularly Pb, Hg, Zn, Mo, Sb, Fe, Cu, and Cd to different extents. Contamination indices including geoaccumulation index, pollution index, and Nemerov integrated pollution index along with multivariate statistical analyses confirmed that steel and iron industries are the most contaminating industries in the study area. The outcomes attained from Kruskal-Wallis test affirmed that there was a significant difference among the concentrations of As, Hg, Mn, Cu, Fe, Pb, Mo, Cd, V, Zn, and Sb in soils around different industrial clusters. Among the studied elements, the highest mobility factors belonged to Zn (81.49%), Pb (76.71%), Cu (71.65%), Hg (66.23%), Mn (62.48%), and Mo (59.27%), respectively. Also, the PMF model showed that steel and iron industries (51.2%) and natural sources (23.4%) are the main sources of PTEs, followed by industrial towns (16.7%) and power plants (8.7%). This is in line with the results of principal component analysis (PCA). Majority of the measured PTEs showed the highest bioavailability in surface soils collected from around the steel and iron industries. Also, based on the outcomes of the health risk assessment model, particular attention should be paid to Hg, Pb, Zn, and Cu in industrial soils of Ahvaz.

Contamination assessment, source apportionment and health risk assessment of heavy metals in paddy soils of Jiulong River Basin, Southeast China

To trace the sources and evaluate the health risks of heavy metals in paddy soils of Jiulong River Basin, seventy-one samples of paddy soils were collected in July 2017. The heavy metals contents were determined using inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrophotometry (AFS). The geo-accumulation index (I_geo) and potential ecological risk index (RI) methods were applied to evaluate the contamination of heavy metals, principal component analysis (PCA) and absolute principal component scores-multiple linear regression (APCS-MLR) were applied to trace the sources, and dose–response model was applied to assess the health risks to the human body. The results indicated that the paddy soils were moderately to heavily polluted by Cd and slightly polluted by Hg, Pb, As and Zn. Heavy metals in paddy soils presented considerable to high potential ecological risk, mostly contributed by Cd and Hg with contribution rates of 59.4% and 26.2%, respectively. The heavy metals contaminating paddy soils were derived from natural sources, agricultural activities, industrial discharge, coal combustion and unidentified sources, with source contribution rates of 31.37%, 24.87%, 19.65%, 18.05% and 6.06%, respectively. The heavy metals in paddy soils presented carcinogenic risks which humans can tolerate and no non-carcinogenic risks. The total non-carcinogenic risks mainly derived from agricultural activities and coal combustion, with contribution rates of 62.16% and 20.21%, respectively, while the total carcinogenic risks mainly derived from natural sources and industrial discharge, with contribution rates of 51.17% and 18.98%, respectively.

APCS-MLR and dose–response model were combined to identify the sources and human health risks of heavy metals in paddy soils.