Heavy metal distribution, translocation, and human health risk assessment in the soil-rice system around Dongting Lake area, China

Effects of atmospheric deposition on heavy metal contamination in paddy field systems under different functional areas in ChangZhuTan, Hunan Province, China

In recent decades, the problem of heavy metal contamination in rice paddies has attracted widespread attention. However, most studies on heavy metal contamination in paddy fields are biased towards soil and/or rice plants, without taking atmospheric deposition into account. In this study, atmospheric deposition, paddy soil, and rice samples were collected from three functional areas (area proximity to factories, along the roadside, and suburban) in ChangZhuTan, Hunan Province. The pollution characterization, translocation, and health risk of heavy metals were reassessed. The findings revealed that Cd and As contamination in the study area's soils was more severe, with point exceedance rates reaching 70 % and 35.9 %, respectively. The highest concentrations of As, Ni, Cd, and Pb in atmospheric deposition were found along the roadside, with 1.42 μg/m2/day, 3.21 μg/m2/day, 0.34 μg/m2/day, and 8.28 μg/m2/day, respectively. In area proximity to factories, As and Ni in atmospheric deposition showed to be lowest, whereas Cd and Pb concentrations showed lowest in suburban areas. Furthermore, the accumulation of Cd and Pb in rice grains in regions proximity to factories was significantly higher than in other regions. The human health risk assessment indicated the health risk caused by rice intake in areas proximity to factories was the highest and requires attention, which was mainly due to Cd accumulation, with HQ value reached 3.19. Correlation tests indicate that atmospheric deposition has a positive effect on heavy metal enrichment in rice grains. Further Random Forest analysis revealed that the transport of heavy metals from atmospheric deposition to leaves and shells were important influencing factors for As, Cd, Ni and Mg accumulation in rice grain. Therefore, more attention should be paid to the effects of atmospheric deposition on the accumulation of heavy metals in paddy fields in order to maintain the production safety of crops.

Solidification/stabilization of lead-contaminated soil using alkali-activated volcanic ash

The bioaccumulation of lead in soil poses a significant human health risk. The solidification/stabilization (S/S) technique, employing binders like Portland cement or lime, is a common method for remediating lead-contaminated soil. However, cement production has adverse environmental impacts, prompting the exploration of eco-friendly alternatives like alkali-activated materials (AAMs). This study assesses AAM efficacy in the S/S of lead-contaminated soil. The effects of several factors, including varying amounts of volcanic ash (VA), lead concentration, curing temperatures, and curing times are investigated. Unconfined compressive strength (UCS), toxicity characteristic leaching procedure test (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscope-energy-dispersive spectroscopy-mapping analyses (FESEM/EDS/mapping) analyses are used to study the specimens. The findings indicated a substantial increase in the UCS of lead-contaminated soil treated with 15% VA (under oven curing (OC) conditions), and 10% VA (under ambient curing (AC) conditions) exhibited remarkable increases of up to 600% and 458%, respectively. Moreover, the leaching of Pb2+ ions from samples contaminated with 10,000 mg/kg (under OC conditions) and 2500 mg/kg (under AC conditions) experienced significant reductions of 87% (from 135.14 to 13.36 ppm) and 91% (from 26.32 to 2.21 ppm), respectively. The S/S process in these samples operated through three primary mechanisms of chemical bonding, physical encapsulation, and the formation of insoluble silicate. The formation of N-A-S-H and hydroxy sodalite structures played a vital role in facilitating these mechanisms. Therefore, alkali-activated VA demonstrated excellent performance in the remediation of lead-contaminated soil.

Deterioration phenomenon of Pb-contaminated aqueous solution remediation and enhancement mechanism of nano-hydroxyapatite-assisted biomineralization

Modern metallurgical and smelting activities discharge the lead-containing wastewater, causing serious threats to human health. Bacteria and urease applied to microbial-induced carbonate precipitation (MICP) and enzyme-induced carbonate precipitation (EICP) are denatured under high Pb2+ concentration. The nano-hydroxyapatite (nHAP)-assisted biomineralization technology was applied in this study for Pb immobilization. Results showed that the extracellular polymers and cell membranes failed to secure the urease activity when subjected to 60 mM Pb2+. The immobilization efficiency dropped to below 50% under MICP, whereas it due to a lack of extracellular polymers and cell membranes dropped to below 30% under EICP. nHAP prevented the attachment of Pb2+ either through competing with bacteria and urease or promoting Ca2+/Pb2+ ion exchange. Furthermore, CO32- from ureolysis replaced the hydroxyl (-OH) in hydroxylpyromorphite to encourage the formation of carbonate-bearing hydroxylpyromorphite of higher stability (Pb10(PO4)6CO3). Moreover, nHAP application overcame an inability to provide nucleation sites by urease. As a result, the immobilization efficiency, when subjected to 60 mM Pb2+, elevated to above 80% under MICP-nHAP and to some 70% under EICP-nHAP. The findings highlight the potential of applying the nHAP-assisted biomineralization technology to Pb-containing water bodies remediation.

Cadmium accumulation in tropical island paddy soils: From environment and health risk assessment to model prediction

Cultivated soil quality is crucial because it directly affects food safety and human health, and rice is of primary concern because of its centrality to global food networks. However, a detailed understanding of cadmium (Cd) geochemical cycling in paddy soils is complicated by the multiple influencing factors present in many rice-growing areas that overlap with industrial centers. This study analyzed the pollution characteristics and health risks of Cd in paddy soils across Hainan Island and identified key influencing factors based on multi-source environmental data and prediction models. Approximately 27.07% of the soil samples exceeded the risk control standard screening value for Cd in China, posing an uncontaminated to moderate contamination risk. Cd concentration and exposure duration contributed the most to non-carcinogenic and carcinogenic risks to children, teens, and adults through ingestion. Among the nine prediction models tested, Extreme Gradient Boosting (XGBoost) exhibited the best performance for Cd prediction with soil properties having the highest importance, followed by climatic variables and topographic attributes. In summary, XGBoost reliably predicted the soil Cd concentrations on tropical islands. Further research should incorporate additional soil properties and environmental variables for more accurate predictions and to comprehensively identify their driving factors and corresponding contribution rates.

Ensemble learning-based applied research on heavy metals prediction in a soil-rice system

Accurate prediction of heavy metal accumulation in soil ecosystems is crucial for maintaining healthy soil environments and ensuring high-quality agricultural products, as well as a challenging scientific task. In this study, we constructed a dataset containing 490 sets of multidimensional environmental covariate data and proposed prediction models for heavy metal concentrations (HMC) in a soil-rice system, EL-HMC (including RF-HMC and GBM-HMC), based on Random Forest (RF) and Gradient Boosting Machine (GBM) ensemble learning (EL) techniques. To reasonably evaluate the effectiveness of each model, Multiple linear and Bayesian regressions were selected as benchmark models (BM), and mean absolute error (MAE), root mean square error (RMSE), and determination coefficient R2 were selected as evaluation indicators. In addition, sensitivity and spatial autocorrelation (SAC) analyses were used to examine the robustness of the model. The results showed that the R2 values of RF-HMC and GBM-HMC for modeling available cadmium (Cd) concentrations in soil were 0.654 and 0.690, respectively, with an average increase of 48.0 % compared to the BMs. The R2 values of RF-HMC and GBM-HMC for predicting Cd, lead (Pb), chromium (Cr), and mercury (Hg) concentrations in rice ranged from 0.618 to 0.824 and 0.645 to 0.850, respectively, with an average increase of 58.2 % compared with the BMs. The corresponding MAEs and RMSEs of RF-HMC and GBM-HMC had low error levels. Sensitivity analysis of the input features and the SAC of the prediction bias showed that the EL-HMC models have excellent robustness. Therefore, the EL technology-based prediction models for HMCs proposed herein are practical and feasible, demonstrating better accuracy and stability than the traditional model. This study verifies the application potential of EL technology in pollution ecology and provides a new perspective and solution for sustainable management and precise prevention of heavy metal pollution in farmland soil at the regional scale.

Biopolymer-assisted enzyme-induced carbonate precipitation for immobilizing Cu ions in aqueous solution and loess

Wastewater, discharged in copper (Cu) mining and smelting, usually contains a large amount of Cu2+. Immobilizing Cu2+ in aqueous solution and soils is deemed crucial in preventing its migration into surrounding environments. In recent years, the enzyme-induced carbonate precipitation (EICP) has been widely applied to Cu immobilization. However, the effect of Cu2+ toxicity denatures and even inactivates the urease. In the present work, the biopolymer-assisted EICP technology was proposed. The inherent mechanism affecting Cu immobilization was explored through a series of test tube experiments and soil column tests. Results indicated that 4 g/L chitosan may not correspond to a higher immobilization efficiency because it depends as well on surrounding pH conditions. The use of Ca2+ not only played a role in further protecting urease and regulating the environmental pH but also reduced the potential for Cu2+ to migrate into nearby environments when malachite and azurite minerals are wrapped by calcite minerals. The species of carbonate precipitation that are recognized in the numerical simulation and microscopic analysis supported the above claim. On the other hand, UC1 (urease and chitosan colloid) and UC2 (urea and calcium source) grouting reduced the effect of Cu2+ toxicity by transforming the exchangeable state-Cu into the carbonate combination state-Cu. The side effect, induced by 4 g/L chitosan, promoted the copper-ammonia complex formation in the shallow ground, while the acidic environments in the deep ground prevented Cu2+ from coordinating with soil minerals. These badly degraded the immobilization efficiency. The Raman spectroscopy and XRD test results tallied with the above results. The findings shed light on the potential of applying the biopolymer-assisted EICP technology to immobilizing Cu ions in water bodies and sites.

Ecological risk assessment of potentially toxic elements in selenium-rich soil with different land-use types

Dashan Village area is one of the representative areas in China with high selenium concentration in the natural environment. A total of 133 topsoil samples have been collected in the Dashan Village area to explore the potential toxic elements (PTEs) background concentrations in soils under different land-use types for a comprehensive PTEs risk assessment (arsenic, cadmium, chromium, copper, mercury, nickel, lead, selenium and zinc). The results show that the geometric mean concentrations of As, Cr, Cu, Hg, Ni, Pb, Se and Zn found in the soil of the Dashan Village area were lower than the control standard for soil contamination risk in agricultural land. However, the geometric mean concentrations of Cd exceeded their corresponding standard values. For different land-use types, geometric mean concentrations of As, Cd, Cu, Hg, Ni and Pb in the arable soils were higher than in woodland soils and tea garden soils. Based on the potential ecological risk assessment, the woodland, arable and tea garden were at low-risk levels. Cadmium posed the highest ecological risk, while the other PTEs were of low risk in soils. Multiple statistical analyses and geostatistical analysis indicated that the concentrations of Cr, Ni, Pb, Cu, Zn and Se originated mainly from natural sources, while the concentrations of Cd, As and Hg could be influenced by anthropogenic activities. These results provide scientific support for the safe utilization and ecological sustainability of selenium-rich land resources.

What adverse health effects will environmental heavy metal co-exposure bring us: based on a biological monitoring study of sanitation workers

To investigate the relationship between health effect profile and co-exposure to heavy metal, 254 sanitation workers from Guangzhou, China, were recruited. Ten urinary metals were determined by inductively coupled plasma mass spectrometry. Parameters of physical examination, including blood lipid metabolism, renal function, blood pressure, and lung function, were tested for each participant. The hazard quotients (HQs) of eight heavy metals were evaluated. Cobalt, copper (Cu), molybdenum (Mo), nickel (Ni), and tin (Sn) demonstrated the top five associations with human health with the ∑₁₉β as 2.220, 1.351, 1.234, 0.957, and 0.930, respectively. Most physical examination parameters of workers were under the normal ranges, except the levels of forced mid expiratory flow rate (MMEF_75/25), the maximum expiratory flow rate at 25% vital capacity (MEF₂₅) and apolipoprotein B in the first quartile, and the level of uric acid in the third quartile of sanitation works. Moreover, Cu was significantly associated with diastolic pressure, pulse, and high density lipid (p < 0.05). Each unit increase in Mo level was related to a 120% increase odd ratio (OR) of abnormal of systolic pressure, but was significantly and negatively correlated with high density lipoprotein and apolipoprotein A, suggesting that Mo exposure may be a risk factor of cardiovascular disease. Each unit increase in Ni and Sn levels was associated with an increased OR of abnormal rate of MMEF_75/25 and MEF₂₅ (p < 0.001), suggesting the increasing risks of respiratory diseases. Sanitation workers exposed to Ni and Pb alone had no carcinogenic risks (HQ < 1). However, 23.8%, 34.6%, and 87.3% of sanitation workers confronted non-carcinogenic risks when exposed to Cu, Mo alone (HQ > 1), or co-exposed to the four heavy metals (HI > 1). Our study preliminarily revealed the potential sensitive health indicators of heavy metal co-exposure, which will provide beneficial health protection suggestions for the occupational populations.

The ignored risk: heavy metal pollution of medicine and food homologous substances

A survey was conducted to investigate the effects of cadmium (Cd), arsenic (As), chromium (Cr), lead (Pb), and copper (Cu) in medicine and food homologous substances (MFHs) on human health. Nine common and typical MFHs (Dendrobium, Bulbus lilii, Poria, Semen nelumbinis, Radix puerariae, Gardenia jasminoides, Hordeum vulgare L, Semen coicis, and Ganoderma Karst) in the form of medicinal slices ready for decoction were purchased from pharmacies. Five among the MFHs (Dendrobium, Bulbus lilii, Poria, Semen nelumbinis, and Radix puerariae) were further obtained from a local field as raw materials for comparison. The results showed that raw materials of MFHs collected from the field had higher contents of heavy metal and greater health risks than medicinal slices purchased from pharmacy. Generally, the heavy metal residues in MFHs of different medicinal parts were different, and MFHs from roots or stems had significantly higher contents of heavy metals than those from fruits or seeds. Most importantly, the contents of Cd in Bulbus lilii and As in wild Poria from field were higher than the contents described in the Pharmacopoeia of the People's Republic of China (ChP). Non-carcinogenic and carcinogenic risk assessments revealed that Poria from field had larger non-carcinogenic and carcinogenic risks to human health; Bulbus lilii showed no non-carcinogenic risk but exhibited carcinogenic risks, whereas Cr showed carcinogenic risks in all samples. Given that MFHs are incorporated in regular foods, care should be taken to minimize health hazards caused by heavy metals to human. This study creates awareness on the safety issues associated with MFHs, and provides basic information for establishing the maximum allowable contents of medicinal and food substances in normal diets.

The lead and cadmium content in rice and risk to human health in China: A systematic review and meta-analysis

Numerous studies have investigated concentrations of lead (Pb) and cadmium (Cd) in rice in China, but have come to divergent conclusions. Therefore we systematically reviewed and meta-analyzed the available evidence on levels of Pb and Cd in rice in different regions of China in order to assess the potential risk to human health. The meta-analysis included 24 studies of Pb levels and 29 studies of Cd levels, published in 2011-2021. The pooled Pb concentration in rice was 0.10 mg per kg dry weight (95% CI 0.08-0.11), while the pooled Cd concentration was 0.16 mg per kg dry weight (95% CI 0.14-0.18). These levels are within the limits specified by national food safety standards. However, the total target hazard quotient for both metals exceeded 1.0 for adults and children, suggesting that rice consumption poses a health risk.

Accumulation and risk assessment of heavy metals in rice: a case study for five areas of Guizhou Province, China

In the present study, the concentration and accumulation abilities of five heavy metals (Cd, Hg, As, Pb, Cr) in rice were assessed and their human health risk to local citizens had been evaluated. Soil and rice samples (125 samples) were collected from Guiyang (GY), Qiannan (QN), Bijie (BJ), Tongren (TR), and Zunyi (ZY) in Guizhou Province. Heavy metals were measured by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave digestion. The mean concentrations of Cd, Hg, As, Pb, and Cr were 0.58, 0.65, 12.31, 38.70, and 87.30 mg/kg in soil and were 0.05, 0.005, 0.11, 0.07, and 0.34 mg/kg in rice, respectively. The bioconcentration factors (BCF) decreased with the order Cd > Hg > As > Cr > Pb. Non-carcinogenic risk in this study was evaluated using the method of the hazard quotient (HQ) and hazard index (HI). The mean HQ values for Cd, Hg, Pb, and Cr were all lower than the standard limit (1.0) for children and adults, except As with the mean HQ for children of 2.79. The mean HI values for children and adults were 4.22 and 1.42, which exceeded 1.0. The mean carcinogenic risk (CR) values of As and Pb for children and adults were higher than the upper limit of the acceptable range (1 × 10^-4) established by the United States Environmental Protection Agency (USEPA). In a conclusion, the non-carcinogenic and carcinogenic risks induced by heavy metals for children were higher than that for adults. This study revealed that consumption of rice in study areas may pose potential non-carcinogenic and carcinogenic risks to humans, and As was the largest contributor.

The Spatiotemporal Evolution Characteristics of Cultivated Land Multifunction and Its Trade-Off/Synergy Relationship in the Two Lake Plains

The material foundation of sustainable agricultural development is cultivated land resources, and their sustainable use is critical to fostering agricultural sustainability and guaranteeing national food security. In this paper, the multifunctional evaluation framework of the cultivated land system based on the "GESEL" model at the grid scale (5 km × 5 km) is constructed to explore the spatiotemporal evolution characteristics of a multifunctional cultivated land system in two lake plains and the trade-off and synergy between the functions. The five functions are all unstable in time scales, and their spatial distribution characteristics are also different. The trade-off and synergy between the multiple functions of the cultivated land system in the two lake plains from 2000 to 2019 showed significant spatial heterogeneity. Most of the functions were mainly collaborative, and a few were trade-offs. The two lake plains can be divided into four multi-functional cultivated land zones: a grain production leading zone, a distinctive agricultural planting zone, a high-efficiency agricultural development zone, and an ecological agricultural construction zone. This research puts forward some countermeasures and suggestions to promote the sustainable utilization of cultivated land resources.

Convolutional neural networks-based health risk modelling of some heavy metals in a soil-rice system

The long-term consumption of heavy metal-rich rice can cause serious harm to human health. However, the existing health risk assessment (HRA) can only be performed after the rice has been harvested, and this approach belongs to a passive and lagging pattern. This study is the first to explore the feasibility of health risk (HR) prediction by proposing the indirect model CNNHR-IND and the direct model CNNHR-DIR based on the convolutional neural network (CNN) technology. The dataset included 390 pairs of soil-rice samples collected from You County, China, with 17 environmental covariates. The R² values for CNNHR-IND for non-carcinogenic and carcinogenic risks were 0.578 and 0.554, respectively, and those for CNNHR-DIR were 0.647 and 0.574, respectively. The results demonstrated that both models performed well, especially CNNHR-DIR had a higher estimation accuracy. The spatial autocorrelation analysis indicated that CNNHR-DIR exerted no systematic bias in the prediction results for health risks, confirming the rationality of the CNNHR-DIR model. The sensitivity analysis further confirmed the generalizability and robustness of CNNHR-DIR. This study proved the feasibility of HR prediction and the potential of CNN technology in HRA, and is significant regarding early risk warnings of rice planting and the sustainable development of public health.

Co-exposure of potentially toxic elements in wheat grains reveals a probabilistic health risk in Southwestern Guizhou, China

Bijie is located at a typical karst landform of Southwestern Guizhou, which presented high geological background values of potentially toxic elements (PTEs). Recently, whether PTE of wheat in Bijie is harmful to human health has aroused people's concern. To this end, the objectives of this study are to determine the concentrations of PTE [chromium (Cr), nickel (Ni), arsenic (As), lead (Pb), cadmium (Cd), and fluorine (F)] in wheat grains, identify contaminant sources, and evaluate the probabilistic risks to human beings. A total of 149 wheat grain samples collected from Bijie in Guizhou were determined using the inductively coupled plasma mass spectrometer (ICP-MS) and fluoride-ion electrode methods. The mean concentrations of Cr, Ni, As, Cd, Pb, and F were 3.250, 0.684, 0.055, 0.149, 0.039, and 4.539 mg/kg, respectively. All investigated PTEs met the standard limits established by the Food and Agriculture Organization except for Cr. For the source identification, Cr and Pb should be originated from industry activities, while Ni, As, and Cd might come from mixed sources, and F was possibly put down to the high geological background value. The non-carcinogenic and carcinogenic health risks were evaluated by the probabilistic approach (Monte Carlo simulation). The mean hazard quotient (HQ) values in the three populations were lower than the safety limit (1.0) with the exception of As (children: 1.03E+00). However, the mean hazard index (HI) values were all higher than 1.0 and followed the order: children (2.57E+00) > adult females (1.29E+00) > adult males (1.12E+00). In addition, the mean carcinogenic risk (CR) values for Cr, As, Pb, and Cd in three populations were all higher than 1E-06, which cannot be negligible. The mean threshold CR (TCR) values were decreased in the order of children (1.32E-02) > adult females (6.61E-03) > adult males (5.81E-03), respectively, all at unacceptable risk levels. Moreover, sensitivity analysis identified concentration factor (C _W ) as the most crucial parameter that affects human health. These findings highlight that co-exposure of PTE in wheat grains revealed a probabilistic human health risk. Corresponding measures should be undertaken for controlling pollution sources and reducing the risks for the local populace.

Metal(loid) flux change in Dongting Lake due to the operation of Three Gorges Dam, China

A drastic decrease in the suspended sediment of Dongting Lake (DTL) has been observed due to Three Gorges Dam (TGD) impoundment operation since 2003. However, the relationship between sediment loads and metal fluxes has not been studied. This study comprehensively analyzed the content characteristics of seven metal(loid)s (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the surface sediment of DTL from 2000 to 2019. The period of 2005-2009 corresponded to a metal(loid) enrichment stage in the sediment of DTL. The metal(loid) cumulative input of DTL from 2000 to 2019 reached 153 × 10³ t, and the increasing rate was gradually diminished because of TGD operation, while the metal(loid) cumulative output reached 132 × 10³ t. Undergoing an input-output state transition, the metal(loid) cumulative deposition of DTL in 2019 was only 42% of its peak in 2007. Especially, the metal(loid) fluxes of DTL all became negative for the first time in 2006. It is worth noting that Cd in DTL has shifted to a net export during the study period. Finally, the assessment results of pollution, risk, and toxicity indicated that metal(loid) effects on sediment quality were weakening in recent years. This study confirmed that DTL has shifted from metal(loid) deposition to export, providing new information for future DTL management options.

Probabilistic health risk assessment for residents exposed to potentially toxic elements near typical mining areas in China

Public health problems caused by toxic elements in mining areas have always been an important topic worldwide. However, existing studies have focused on single exposure routes and common toxic elements, which might underestimate the risks faced by residents. In this study, three typical mining areas in central China were selected to assess the health risks of 14 potentially toxic elements through five exposure routes using Monte Carlo simulations. The results indicated that the 95th percentile non-carcinogenic risk values to humans via rice and vegetable ingestion ranged from 9.8 to 26.0 and 6.2 to 19.0. The corresponding carcinogenic risks ranged from 1.4E-2 to 6.3E-2 and from 2.9E-3 to 2.3E-2, respectively. Therefore, residents face serious health risks. Multi-element analysis showed that cadmium (Cd), boron (B), and arsenic (As) were the main contributors to rice non-carcinogenicity, whereas Cd and nickel (Ni) were the main elements of rice carcinogenicity. B and lead (Pb) played an essential role in the non-carcinogenesis of vegetables, and B, Ni, and Cd played an essential role in carcinogenesis. Accidental ingestion is the main route of soil exposure. In these three areas, the probability of non-carcinogenic risk faced by adults was 40%, 0%, and 1%, respectively, while the probabilities for children were 100%, 62%, and 83%, respectively. Regarding carcinogenicity, the risk for both adults and children was up to 100%. This study emphasizes the overall health risks in polluted areas via multi-route and multi-element analysis. This conclusion is helpful to comprehensively assess the potential health risks faced by residents in mining areas and provide baseline data support and a scientific basis for formulating reasonable risk control measures.

Convolutional neural network-based applied research on the enrichment of heavy metals in the soil-rice system in China

The enrichment of heavy metals in the soil-rice system is affected by various factors, which hampers the prediction of heavy metal concentrations. In this research, a prediction model (CNN-HM) of heavy metal concentrations in rice was constructed based on convolutional neural network (CNN) technology and 17 environmental factors. For comparison, other machine learning models, such as multiple linear regression, Bayesian ridge regression, support vector machine, and backpropagation neural networks, were applied. Furthermore, the LH-OAT method was used to evaluate the sensitivity of CNN-HM to each environmental factor. The results showed that the R² values of CNN-HM for Cd, Pb, Cr, As, and Hg were 0.818, 0.709, 0.688, 0.462, and 0.816, respectively, and both the MAE and RMAE values were acceptable. The sensitivity analysis showed that the concentrations of Cd and Pb, mechanical composition, soil pH, and altitude were the main sensitive features for CNN-HM. Compared with CNN-HM based on all input features, the performance of the quick prediction model that was based on the sensitive features did not degrade significantly, thereby indicating that CNN-HM has stronger stability and robustness. The quick prediction model has extensive application value for timely prediction of the enrichment of heavy metals in emergencies. This study demonstrated the effectiveness and practicability of CNNs in predicting heavy metal enrichment in the soil-rice system and provided a new perspective and solution for heavy metal prediction.

Effects of phosphorus-containing material application on soil cadmium bioavailability: a meta-analysis

Diverse phosphorus-containing materials (PCMs) were widely applied in remediation of cadmium-contaminated soils, and their effects on the change of soil cadmium availability (SCA) varied with their physicochemical characteristics and environmental conditions. Investigation on the effect of various PCMs on reducing SCA under different conditions favors the safe utilization of Cd-contaminated soil. Herein, a meta-analysis of literature published before August 2021 was carried out. A total of 342 independent observations were obtained from 42 published papers which included 9 factors that may affect the passivation effect of fertilizer content: phosphorus type, phosphorus application rate, soil pH, soil CEC, soil organic matter, experiment type, and time. Results of boosted regression tree analysis showed that the application rate is the most important factor contributing to the SCA, followed by soil pH and duration. Results of this meta-analysis showed that medium P input shows potential for reactivating the SCA. Under alkaline soil conditions and high soil CEC values, PCM input can better deactivate SCA. In addition, the difference from the previous understanding is that under the medium input of phosphorus-containing fertilizer (90-500 mg P∙kg^-1), it will significantly increase the content of available cadmium in soil. In addition, future recommendation for exploring novel PCMs and suitable strategies for controlling the SCA though PCM application were also proposed. Our works may promote the interpretation of the interference factors on the SCA changes and fill the research gaps on utilization of PCM in Cd-polluted soil remediation.

Distribution, bioavailability, and human health risk assessment of arsenic in groundwater-soil-rice system in the Jianghan Plain, Central China

Many studies have reported high arsenic concentrations in the groundwater and soil of the Jianghan Plain (JHP), an important rice production base in China. However, no comprehensive study on the occurrence and risk of As in groundwater-soil-rice systems in this region has been conducted. In this study, As concentrations in groundwater, soil, rice straw, and rice grain samples were analyzed. Arsenic concentrations were found to range from BDL to 42.88 μg/L (median 0.34 μg/L) in phreatic water, BDL to 41.77 μg/L (median 8.64 μg/L) in soil pore water, 10.20 to 21.90 mg/kg (mean 16.52 mg/kg) in soil, 0.204 to 2.860 mg/kg (mean 0.847 mg/kg) in rice straw, and 0.131 to 0.951 mg/kg (mean 0.449 mg/kg) in rice grain. Arsenic uptake by rice from soils was evaluated according to bioavailable As defined by chemical extraction and diffusive gradients in thin films. The results indicated that owing to the low content of highly mobile As fractions, the less mobile As fraction (mainly bound with amorphous Fe/Al (hydr)oxides) also contributed to bioavailable As, suggesting that amorphous Fe/Al bound As should be considered in analyzing bioavailable As. In terms of the geoaccumulation index and the Chinese paddy soil standard (GB15618-2018) limit (25 mg/kg), As pollution in water and soils in the study area is at a low level and can be considered relatively safe. However, the target hazard quotients and cancer risk assessment indicated that As pollution is at a dangerous level with potential human health risk. According to the bioconcentration factor, the bioavailability of soil is higher in JHP compared with other rice-growing areas owing to the unique hydrogeological conditions and irrigation using groundwater with high As content. Rice planting areas in JHP should be set as far away from large rivers as possible, and groundwater with high As concentrations must be pre-treated prior to irrigation.

Ecological and health risk assessment of heavy metals in soil and Chinese herbal medicines

As medicinal plants can accumulate harmful metals from the native soil, people's consumption of these materials may cause the human body to accumulate toxic metal elements. This has given rise to people's concerns about the quality and safety of Chinese medicinal materials. This research aims to determine the levels of Cr, Ni, Cu, Zn, As, Cd, Hg and Pb in four medicinal plant species (Aster tataricus L.f., Salvia miltiorrhiza Bge, Radix Aucklandiae, Scutellaria baicalensis Georgi) and their native soil. All samples were collected from Qian'an city, beside Yanshan Mountain Range in Tangshan city, east Hebei Province, north China. The contents of heavy metals we detected in the soil conformed to the current limits. However, the Cd and Hg in the soil had a very high potential ecological risk because of their contents higher than the base level of local soil. The contents of Cu, Cd, Hg and Pb in some medicinal herbs exceeded the standards. The content of Cu in Radix Aucklandiae exceeded the standard by 3 times, and others exceeded the standard by less than one time. The comprehensive health risk assessment of heavy metals with chronic non-carcinogenic effects for human body showed that none of the four medicinal herbs can create a health risk. Thus, there is no strong positive correlation between heavy metal pollution in medicinal herbs and that in the native soil. Further research should be investigated to the connection between the heavy metal levels in the soil and plants, and the comprehensive effects of soil, air and irrigation water on heavy metal pollution of Chinese herbal medicines. We also recommend that Chinese herbal medicines should be cultivated and gathered only from controlled or uncontaminated areas.

Pollution monitoring, risk assessment and target remediation of heavy metals in rice from a five-year investigation in Western Fujian region, China

Recently, rice contamination by heavy metals (HMs) has become a severe problem. Taking the Western Fujian region as an example in this study, a total of 1311 rice samples containing eight HMs were collected from 2015 to 2019, then used to explore their pollution characteristics, health risks, and Spatio-temporal variations, finally derive the target remediation areas of the key pollutants. The results showed that average concentrations of all the HMs had not reached the limits of the National Standards of Food Safety, but pollution indexes of As (0.783) and Cu (0.665) were at accumulation level (>0.6), which posed high pollution risks. Furthermore, locations of higher HMs concentrations coincided with those of higher pollution estimation probabilities. The non-carcinogenic risk (4.150, 2.434) and carcinogenic risk (4.96 × 10^-3, 2.92 × 10^-3) for children and adults cannot be negligible, As and Cd were the largest contributors. Children were more susceptible than adults due to the metal concentrations and rice intake rate. The spatio-temporal changes indicated that a decreasing trend in average concentrations of HMs (except Cr), but As (0.37%-0.88%) contents increased in the west and northeast parts, and so did Cd (1.92%-5.11%) in the central region during monitoring. For the target remediation, particular regions in the western and eastern were used as risky areas of As and Cd, respectively. Our results will provide theoretical support for the pollution management of HMs in rice.

Probabilistic health risk assessment of inorganic arsenic and some heavy metals in rice produced from a typical multi-mining county, China

The potential impact of exposure to toxic elements in rice on human health has become a global public health issue. This study analyzed the pollution characteristics and probabilistic health risks of exposure to iAs, Pb, Cd, Cr, and Hg in rice produced in a typical multi-mining county using Monte Carlo simulation, a geographic information system, and bioavailability analysis. The results showed that the enrichment of As and Cd was prominent in rice, with mean tAs, iAs, and Cd contents of 0.34 ± 0.20, 0.15 ± 0.09, and 0.48 ± 0.50 mg·kg^-1, respectively. The probability of non-carcinogenic risk via rice consumption in adults and children exceeding the threshold was 72% and 78%, respectively, and that of carcinogenic risk was as high as 100%. Among toxic elements, Cd and iAs were the main risk factors for health risks. The high-level health-risk areas mainly occurred in the north-eastern and central parts of the study area. Sensitivity analysis highlighted that the top three influential parameters for non-carcinogenic risk in adults were Content(Cd), Content(iAs), and Bioaccessibility(Cd), whereas those in children were ingestion rate of rice, Content(Cd), and Content(iAs). The Content(Cd) was the decisive factor for carcinogenic risk, with a sensitivity coefficient of 78.0% in adults and 64.7% in children. Considering the high risk of ingestion of local rice in this area, it is imperative to place strict supervision and take control measures.

The Rice Cation/H+ Exchanger Family Involved in Cd Tolerance and Transport

Cadmium (Cd), a heavy metal toxic to humans, easily accumulates in rice grains. Rice with unacceptable Cd content has become a serious food safety problem in many rice production regions due to contaminations by industrialization and inappropriate waste management. The development of rice varieties with low grain Cd content is seen as an economic and long-term solution of this problem. The cation/H⁺ exchanger (CAX) family has been shown to play important roles in Cd uptake, transport and accumulation in plants. Here, we report the characterization of the rice CAX family. The six rice CAX genes all have homologous genes in Arabidopsis thaliana. Phylogenetic analysis identified two subfamilies with three rice and three Arabidopsis thaliana genes in both of them. All rice CAX genes have trans-member structures. OsCAX1a and OsCAX1c were localized in the vacuolar while OsCAX4 were localized in the plasma membrane in rice cell. The consequences of qRT-PCR analysis showed that all the six genes strongly expressed in the leaves under the different Cd treatments. Their expression in roots increased in a Cd dose-dependent manner. GUS staining assay showed that all the six rice CAX genes strongly expressed in roots, whereas OsCAX1c and OsCAX4 also strongly expressed in rice leaves. The yeast (Saccharomyces cerevisiae) cells expressing OsCAX1a, OsCAX1c and OsCAX4 grew better than those expressing the vector control on SD-Gal medium containing CdCl₂. OsCAX1a and OsCAX1c enhanced while OsCAX4 reduced Cd accumulation in yeast. No auto-inhibition was found for all the rice CAX genes. Therefore, OsCAX1a, OsCAX1c and OsCAX4 are likely to involve in Cd uptake and translocation in rice, which need to be further validated.

Farmland heavy metals can migrate to deep soil at a regional scale: A case study on a wastewater-irrigated area in China

Heavy metal risks to human health in farmland of wastewater-irrigated areas have long been recognized. It remains to be shown whether farmland heavy metals from wastewater irrigation can migrate to deeper soil at a regional scale. In this study, nine soil cores deep to 30 m from three transects (A, B and C) of a linear wastewater reservoir and the adjacent farmland topsoils and wheat grains were sampled. Heavy metals including As, Cd, Cr, Cu, Pb and Zn in the soils and wheat grains were determined, and the grains' health risks were assessed using the Target Hazard Quotient (THQ). Considerably high contents of heavy metals in both total and soluble forms were detected in deep soils, especially for the transect B where total As of 73.0 mg kg^-1 at 29 m, Cd of 3.80 mg kg^-1 at 13 m and Pb of 214 mg kg^-1 at 30 m were detected. The silty clayey and silty layers of the transect B had higher contents of As, Cr, Cu, Pb and Zn compared with the sandy layers. Across the studied area, 19.5%-34.1% of the topsoil samples were contaminated by As, Cd, Cu, Pb and Zn, and 34.1% and 19.5% of the wheat grains were contaminated by Cd and Pb, respectively. Wheat grains from all the sampling sites had a combined target hazard quotient (TTHQ) value of >1, with As and Cd being the most important contributors. Our study revealed a wider and deeper risk of typical heavy metals originated from long-term wastewater irrigation in the sampling area, which may pose substantial health risks to the local residents via wheat grains and groundwater.

Geogenic enrichment of potentially toxic metals in agricultural soils derived from black shale in northwest Zhejiang, China: Pathways to and risks from associated crops

Agricultural soils derived from black shale are typically enriched in potentially toxic metals. This is a serious problem, both in terms of the ecological environment and human health. To assess the levels of potentially toxic metals, 90 paired soil-crops samples were collected from the Anji Country, western Zhejiang province, a typical exposed black shale area in China. Concentrations and bioavailability of potentially toxic metals in the soil-crops system were measured, and the associated potential risks were further evaluated. Results showed the enrichment of potentially toxic metals (i.e. Cd, Pb, Cu, Zn and Ni) in the soil and crop samples, especially a significant accumulation of Cd. Sequential extraction data indicated that Cd in soils derived from black shale was the second most dominant element in the exchangeable fraction (mean at 33.42%) and possessed high bioavailability, whereas Pb was mostly retained in the residual fraction (mean at 76.34%) and exhibited low mobility. The total concentration as well as mobility and bioavailability of Cd were the highest in the sampled soils. This resulted in a high potential ecological risk in areas with agricultural soils derived from black shale, which could eventually jeopardize the health of local residents through various exposure pathways. Overall, our findings provide a scientific basis for developing suitable management strategies to mitigate the exposure to potentially toxic metals in high risk areas.

Geochemistry of heavy metal-contaminated sediments from the Four River inlets of Dongting lake, China

The concentrations of major and trace elements in the sediments from the Four River inlets of Dongting Lake were analysed. The results show that the element compositions of the Four River inlet sediments are different, among which higher amounts of Al2O3, Fe2O3, MnO, Cs, Rb, Th, U, Y, and REE are found, while MgO, CaO, Na2O, and Sr are more depleted in the sediments from the Xiangjiang and Zijiang inlets than in the sediments from the Yuanjiang and Lishui inlets. The Xiangjiang inlet sediments are distinctly higher enriched (EF > 5.0) in heavy metals Bi, Cd, Mn, Cu, Pb, and Zn, while the other river sediments are moderately enriched (EF > 2.0) in these heavy metals. These geochemical differences are resulted from the source lithology, chemical weathering, hydrological sorting, and anthropogenic processes taking place in the watersheds. The principal component analysis and the geochemical vertical profiles suggest that the trace metals Ba, Mo, V, Cr, Co, Ni, Cs, Rb, Sc, Th, U, Ga, Ge, Zr, Hf, Ta, Nb, and REE are of terrigenous sources. The heavy metals including Bi, Cd, Mn, Cu, Pb, and Zn in the sediments can include those contributed by anthropogenic processes, such as mining and smelting of Pb-Zn ores. Therefore, presenting a scheme for the geochemical backgrounds of the watershed is recommended here for future assessment of the heavy metal contamination in sediments of the watershed.

Risk assessment and hotspots identification of heavy metals in rice: A case study in Longyan of Fujian province, China

The potential threats of heavy metals in rice have attracted increasing attention worldwide. In this study, we assessed the pollution status and health risk of rice collected from Longyan in Fujian, China. Meanwhile, we explored the spatial pattern and hotspots of those metals. The results showed that the average concentrations of Cd, Hg, As, Pb, Cr, Ni, Cu, and Zn in rice were 0.064, 0.002, 0.464, 0.072, 0.138, 0.106, 10.819, and 23.788 mg kg^-1, respectively. Among them, As and Cu remarkably accumulated with the exceeding ratio of 50.30% and 55.12%, respectively. Furthermore, the values of the target hazard quotient in rice ranked as As > Cu > Zn > Cd > Pd > Ni > Hg > Cr, which As and Cu was greater than 1.0. And the carcinogenic risk values were in the order of As > Cd > Ni > Cr, which all exceeded the tolerance level (1 × 10^-4). Risk assessment indicated that both children and adults were posed the non-carcinogenic and carcinogenic risk from rice intake, and As had the largest contribution rate for them. Comparison found that the spatial patterns of heavy metals distribution were consistent with the hotspots. The hotspots for As and Zn located in the western part (Changting and Wuping), Cd and Cu in the eastern part (Xinluo and Yongding), Cr and Ni were simultaneously found in the northeast (Zhangping), while Hg and Pb were mainly located in the central region (Shanghang). Overall, combining the pollution status, risk assessment, and hotspot distribution in rice, the western region (Changting and Wuping) were identified as priority areas for remediation.

Estimation of spatial distribution and health risk by arsenic and heavy metals in shallow groundwater around Dongting Lake plain using GIS mapping

Potable groundwater has become the primary water source for the local population because of the serious pollution of As and heavy metals in the surface water around the Dongting Lake Plain. A comprehensive research on the shallow groundwater was performed in this study via geographical information system (GIS) and geochemical method to evaluate groundwater quality and health risks of shallow groundwater in Dongting Lake Plain. Eighty-seven samples were collected and the content of As and twelve other heavy metals (e.g., Al, Fe, Zn, Cu, Mo, Ni, Mn, Co, Ba, Pb, Cd, and Cr) in the samples were detected by inductively coupled plasma-mass spectrum (ICP-MS) technology. The water pollution situation was assessed using heavy metal contents and evaluation indices, and human health risks were evaluated on the basis of both carcinogenic and noncarcinogenic aspects. Results showed that the shallow groundwater quality is moderately to heavily contaminated and should be considered in some areas of the Li and Xiangjiang River coasts. Several regions have the potential of carcinogenic risks induced by As and the groundwater in some regions may have the risk of Cr carcinogenesis in the wet season. These findings suggested that the potential harm caused by Fe, Zn, Mn, Cr, and As pollution of groundwater, especially As and Cr in wet season, must be considered. The spatio-temporal study on the groundwater quality evaluation may be beneficial to the protection and sustainable development of groundwater resources in Dongting Lake Plain.Summary: Although the overall noncarcinogenic health risk by metals in shallow groundwater of Dongting Lake is low, noncarcinogenic health risks caused by Fe, Zn, Mn, and As exist in some areas.

Contamination assessment, health risk evaluation, and source identification of heavy metals in the soil-rice system of typical agricultural regions on the southeast coast of China

To quantitatively assess heavy metal accumulation and potential ecological and human health risks as well as analyze the sources of metals in a typical soil-rice system located on the southeast coast of China, 120 topsoil samples and corresponding rice grain samples were collected across the study area. The concentrations of As, Cd, Pb, Cr, Hg, Zn, Cu, and Ni were analyzed. The results revealed that Hg, Cd, and Cu were the main pollutants in soils. Besides, according to geo-accumulation value of Hg, 18.3% of samples were at or above moderate contamination levels. Additionally, the soil was in moderate ecological risk from combined heavy metal pollution, and 49.7% and 27.0% of this risk could be attributed to Hg and Cd pollution, respectively, due to their high toxic-response factors. For the rice samples, Cd content showed the highest biological accumulation coefficient value (40.8%) in rice grains and was slightly greater than its maximum allowable value (MAV) (0.2 mg/kg) in 7.5% of samples, whereas the other metals were all lower than their corresponding MAVs. Heavy metal exposure (especially As exposure) via rice consumption causes significant carcinogenic and non-carcinogenic risks to adults, and non-carcinogenic risk to children, while the carcinogenic risk to children was at tolerable level. Greater rice consumption might be responsible for the greater health risk to adults than children. Natural sources (loaded heavily with Cr and Ni) such as lithogenic components and soil parent materials, agricultural activities (loaded heavily with Cd, Cu, and Zn), especially excessive use of pesticides and fertilizers, and industrial activities (loaded heavily with Hg, Pb, and As) including vehicle emissions, coal combustion, and those of the textile and chemical industries were identified as the main sources. Effective regulations should be enforced to guarantee the safety of farm produce and protect ecological and human health in the study area.

Diagnosis and evaluation of the health status of sediment-water-farmland-rice system in Longtang

As one of the largest electronic waste (e-waste) disassembling sites in China, environmental quality and human health of Longtang town have always been the focus of concern and research. With the effective enforcement of relevant laws, most informal e-waste dismantling centers have been shut down, but heavy metals are non-biodegradable and easily enriched contaminants that are difficult to remove from the environment. This research investigated the heavy metal (Cd, Pb, Cu, Zn, As, and Cr) level in sediments, water, paddy soils, and the matched rice plants in Longtang, and assessed the potential ecological risk and human health risk of heavy metals. The results showed that the heavy metal content was highest in the sediment, followed by paddy soil and rice, the lowest in water, and the surface water was higher than groundwater. In the paddy soil, the heavy metal content in the topsoil was the highest, and all exceeded the soil background value of Guangdong Province, and the level of Cu (129.45 mg kg^-1), Cd (0.44 mg kg^-1), and Pb (100.63 mg kg^-1) exceeded the national risk screening value (GB 15618-2018). Compared with previous studies, the contents of Cd, Cu, and Zn in soil showed a downward trend. Potential ecological risk assessment showed that the risk level of Cd in the topsoil was high, and the risk levels of Cd and Cu in the sediment were very high and considerable, respectively, posing a major risk to human health. In rice plants, heavy metals mainly accumulated in the roots of rice, and their migration ability in rice tissues was poor. The heavy metal level in grain was within the threshold value set by the Codex Alimentarius Commission (CAC, CXS 193-1995) or China (GB 2762-2017), and the risk level to human health was low. Accordingly, it is imperative to continuously monitor the content of heavy metals in the sediment and soil of Longtang, especially Cu and Cd.

Potential health risk assessment for inhabitants posed by heavy metals in rice in Zijiang River basin, Hunan Province, China

The contents of total arsenic (tAs), inorganic arsenic (iAs), Cd, Cr, Cu, Mn, Ni, Pb, Sb, and Zn in 135 rice grain samples from Zijiang River basin were determined, and the probabilistic distribution of noncarcinogenic and carcinogenic risks associated with ingesting locally produced rice was determined by Monte Carlo simulation. Further, multivariate statistical analysis was used to analyze the potential sources of the heavy metals in rice grains. The average concentrations of the heavy metals in rice grains were ranked as follows: Mn (17.314 mg/kg) > Zn (16.043 mg/kg) > Cu (2.013 mg/kg) > Ni (1.332 mg/kg) > Cr (0.571 mg/kg) > Cd (0.283 mg/kg) > tAs (0.241 mg/kg) > Pb (0.145 mg/kg) > Sb (0.027 mg/kg). These heavy metals were significantly enriched in some rice grain samples. The analysis of potential sources indicated that As, Pb, Sb, and Zn were mainly derived from mining and smelting and agricultural activities; Cd, Cu, Mn, and Ni were mainly derived from the agricultural activities; Cr were mainly derived from the natural source. The results of Monte Carlo simulation indicated that ingestion of rice grown in the area may pose health risks for children, adult males, and adult females. The noncarcinogenic risks were mainly from As, Cd, Mn, Ni, and Sb, and the carcinogenic risk was mainly from As, Cd, and Ni. This study could provide basic information for land management and rice intake in the study area.

Distribution of Selected Heavy Metals Bioaccumulation in Various Parts of Indigenous Rice (Bokilong, Ponsulak and Taragang) in North Borneo

The prospect of three native upland paddy landraces known as Bokilong, Ponsulak and Taragang as heavy metals accumulator for phytoremediation was determined. Bioaccumulation of heavy metals (As, Cd, Cr, Cu, Fe, Pb, and Zn) in various parts of paddy plants collected from Kiulu valley, North Borneo in the natural conditions during the vegetative phase and harvest season were analysed by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). All selected heavy metals were traced in soil samples of all three paddy landraces rhizosphere where the most available heavy metals were Fe followed by Zn. Heavy metals bioavailability in soil seemed to be influenced by the local climate of the cultivation field. Bokilong landrace is an accumulator of As, Cd, Cu, Pb and Zn. Ponsulak paddy can help clean up the soil by phytoextraction of As, Cr, Cu, Fe and Zn. Taragang paddy has a prospect in phytoextraction of Cd and Pb to remediate excess amount of this element in the soil. Different heavy metals concentration trends were accumulated in these three paddy landraces in grain indicated different nutritional values. Heavy metal uptake characteristic differs between upland paddy landraces and there was also environmental influence affecting the mobility rate of these elements in paddy plant depending on the element type and paddy genotype.

Ecological risk evaluation and source apportionment of heavy metals in park playgrounds: a case study in Xi'an, Shaanxi Province, a northwest city of China

Park playgrounds recently are suffering serious heavy metals contamination in China. It is urgent to assess the ecological risk and identify the sources for heavy metals. A total of 111 topsoil samples were collected from four park playgrounds in Xi'an, and the X-ray fluorescence (XRF) instrument was used to measure the concentrations of heavy metals including chromium(Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), manganese (Mn), and cobalt (Co), respectively. Ecological risk ([Formula: see text]) and potential ecological risk index (RI) were introduced to determine the pollution level and ecological risk, and the absolute principal component score-multiple linear regression (APCS-MLR) model was implemented to identify the sources for heavy metals. The main results were as follows. (1) Except As, the mean concentrations of measured heavy metals of four park playgrounds surpassed the soil background values of Shaanxi Province. (2) In each park playground, the [Formula: see text] was below a "low" risk level ([Formula: see text]=10) for Cr, Ni, Zn, As, and Mn; Cu was between a "moderate" and "considerable" risk level; Pb was between a "low" and "moderate" risk level; and [Formula: see text] was between a "considerable" and "high" risk level for Co. Besides, the RI index was on a "high" risk level (120 < RI < 240) with an obvious spatial distinction. (3) The anthropogenic factors were the main sources for heavy metals, and mixed sources and natural sources were considered as the minor sources for metals. (4) The sources contributions for Co had obvious spatial heterogeneity in each park situated in four different urban planning districts.

Compound health risk assessment of cumulative heavy metal exposure: a case study of a village near a battery factory in Henan Province, China

The concentrations of the heavy metals Hg, As, Ni, Pb, Cd, Cr, Cu and Zn in soil, groundwater, air, and locally produced grain (wheat and corn) and vegetables were determined in a village near a battery factory in Xinxiang, Henan Province, China. A multimedia, multipathway health risk assessment of heavy metal exposure was carried out using the health risk model recommended by the United States Environmental Protection Agency (US EPA). The results showed that the concentrations of Cd in soil, Cd and Pb in wheat, Hg in corn, Cd, Hg, and Pb in vegetables, and Cd and As in PM2.5, PM10, and TSP were all higher than the corresponding limits for heavy metals in China. The non-carcinogenic risks (HIs) for all environmental media were higher in children than in adults, and the carcinogenic risks (TCRs) of heavy metal exposure in other media except for soil were higher in adults than in children. The total HI and TCR in adults and children were higher than the standard limit values because of heavy metal exposure through soil, groundwater, PM10, grain and vegetables. Cd was the most significant heavy metal in terms of HI and TCR factors; among the evaluated pathways, the contribution of diet was the largest. The HI and TCR caused by dietary crops account for 96.7% and 98.9% of the total in adults and 90.2% and 96.2% of the total in children, respectively. To maintain the health of the residents in the study area, it is strongly recommended to stop planting edible agricultural products immediately, start buying grain and vegetables from outside the study area, and strictly strengthen the control of heavy metal pollution in the study area. The source apportionment results show that Cd, Ni and As were mainly from industrial sources, which was related to sewage irrigation and battery plant deposition, and Pb and Cr were mainly from agricultural activities.

Geogenic cadmium pollution in multi-medians caused by black shales in Luzhai, Guangxi

Cadmium (Cd) concentration was investigated in parent rocks, surrounding soil of black shales outcrop, stream water, stream sediments, paddy soil as well as rice plants. Leaching test and sequential extraction procedure were applied to evaluate Cd mobility and bioavailability in soil samples. This study aims to emphasize ecological risk of Cd induced by black shales by combining various natural medias in black shales area and control area. The black shales parent rocks have elevated Cd concentration and act as a source of Cd. The liberated Cd from black shales outcrop temporarily accumulated in the acidized surrounding soil and could arise potential adverse impacts on environment due to rainfall. Although high concentration of Cd was not detected in stream water, Cd concentrated stream sediment was a hidden toxin for surface water system. Cd in paddy soil was primarily from geogenic source and effected little by anthropogenic source. The concentration as well as mobility and bioavailability of Cd were high in paddy soil in black shales area, which lead to elevated Cd concentration in roots, shoots and grains of rice. As a result, residents in black shales area suffer increased non-carcinogenic risk of Cd via food chain.

Enrichment, Source Apportionment and Health Risk Assessment of Soil Potentially Harmful Elements Associated with Different Land Use in Coastal Tidelands Reclamation Area, Eastern China

Coastal tidelands are important ecological habitat resources and valuable resources for agricultural land reclamation. Enrichment of potentially harmful elements (PHEs) in soil caused by anthropogenic activity is an important factor implicated in the ecological deterioration of soil in China. A total of 54 soil sample sites were selected from a 30-year reclaimed tideland and an adjoining coastal wetland. Descriptive and multivariate statistical analyses were performed to describe the enrichment, source, health risk status of eight PHEs (As, Co, Cr, Cu, Mn, Ni, Pb, and Zn) after long-term reclamation. Results indicated that after 30 years of reclamation, most soil PHEs are slightly enriched, whereas no serious threat of environmental pollution was observed. In the reclamation area, the enrichment of PHEs in the aquaculture land, industrial land, and cropland was relatively high compared with other land use types, such as tideland and halophyte land. The source analysis divided the PHEs into five categories: (1) Cu; (2) Co and Mn; (3) Cr; (4) As and Pb; (5) Zn and Ni. Cu was completely derived from natural parent materials and other elements were governed by both weathering of parent rock and human activities, including agricultural activities, industrial production, and transportation emissions. The health risk assessment showed that the soil PHEs potentially had no non-carcinogenic risk to the public, but there was an acceptable probability to have cancer due to Cr and As. Meanwhile, children are more susceptible to harm from the PHEs in soil than adults. According to the economic and social development situation in the coastal region, it is necessary to pay attention to the environmental threats of PHEs enrichment.