Bioaccessibilities and health implications of heavy metals in exposed-lawn soils from 28 urban parks in the megacity Guangzhou inferred from an in vitro physiologically-based extraction test

Analysis of driving factors for potential toxic metals in major urban soils of China: a geodetetor-based quantitative study

Potential toxic metal (PTM) is hazardous to human health, but the mechanism of spatial heterogeneity of PTM at a macro-scale remains unclear. This study conducts a meta-analysis on the data of PTM concentrations in the soil of 164 major cities in China from 2006 to 2021. It utilizes spatial analysis methods and geodetector to investigate the spatial distribution characteristics of PTMs. The geographic information systems (GIS) and geodetector were used to investigate the spatial distribution characteristics of PTMs, assess the influence of natural factors (NFs) and anthropogenic factors (AFs) on the spatial heterogeneity of PTMs in urban soils, and identified the potential pollution areas of PTMs. The results indicated that the pollution levels of PTMs in urban soils varied significantly across China, with higher pollution levels in the south than in the north. Cd and Hg were the most severely contaminated elements. The geodetector analysis showed that temperature and precipitation in NFs and land use type in AFs were considered as the main influencing factors, and that both AF and NF together led to the PTM variation. All these factors showed a mutually enhancing pattern which has important implications for urban soil management. PTM high-risk areas were identified to provide early warning of pollution risk under the condition of climate change.

Heavy metal spatial distribution, source analysis, and ecological risks in the central hilly area of Hainan Island, China: results from a high-density soil survey

The presence of heavy metals in soil has gained considerable attention due to their potential risks to ecosystems and human health. In this study, a thorough soil investigation was performed in the hilly region of central Hainan, which was formerly regarded as an area with the highest ecological environmental quality. A total of 7094 soil samples were systematically collected with high density over a large area. Simultaneously, a detailed investigation was conducted on the surrounding environment of each sampling point, including environmental factors such as soil, land use and crop types. The soil samples were analysed for heavy metals, pH, organic matter, and other parameters. The soil heavy metal pollution level, ecological risk and health risk were evaluated using the geo-accumulation index and the potential ecological risk index. The findings showed that the average contents of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were 1.68, 0.042, 24.2, 6.49, 0.0319, 7.06, 29.6 and 49.8 mg·kg-1 respectively. Except for Hg, the mean values of the other heavy metals were either lower than or similar to the background values of Hainan. Also, only a few localised areas showed contamination by heavy metals. The primary sources of heavy metals, identified by a positive matrix factorisation model, could be categorised into four types: natural sources related to the soil formation process from acidic intrusive rocks (such as granite); natural sources primarily influenced by atmospheric deposition; anthropogenic sources associated with agricultural activities; and natural sources related to the soil formation process from middle-mafic intrusive rocks and black shales. The correlation analysis and variance analysis findings suggested that the content of heavy metals in the soil was primarily associated with the parent rock. The study area generally had low heavy metal levels and was not significantly polluted. However, agricultural activities still affected the enrichment of heavy metals. Therefore, it is imperative to remain vigilant about the ecological risks linked to soil heavy metals while continuing land development and expanding agricultural activities in the future. These findings indicate that conducting high-density soil surveys can enhance our understanding of regional soil heavy metals and enable reliable recommendations for agricultural planning. Whether in areas with low pollution risk or potential pollution risk, it is recommended that high-density soil surveys be conducted provide scientific guidance for further agricultural development.

Using oral bioaccessibility measurements to refine risk assessment of potentially toxic elements in topsoils across an urban area

Elevated concentrations of As, Cr, Cu, Ni, Pb, V and Zn in topsoils in Belfast, Northern Ireland have been found to exceed assessment criteria in the city and therefore may pose a risk to human health. Most generic assessment criteria (GAC) for potentially toxic elements (PTEs) in soils assume PTEs are 100% bioavailable to humans. Here we use in-vitro oral bioaccessibility testing using the Unified BARGE method (UBM) to measure what proportion of soil contamination dissolves in the digestive tract and therefore is available for absorption by the body. This study considers how PTE bioaccessibility in soils varies spatially across urban areas and refines human health risk assessment for these PTEs using site specific oral bioaccessibility results to present the first regional assessment of risk that incorporates bioaccessibility testing. A total of 103 urban soil samples were selected for UBM testing. Results showed low bioaccessible fraction (BAF) for the PTEs from geogenic sources: Cr (0.45-5.9%), Ni (1.1-46.3%) and V (2.2-23.9%). Higher BAF values were registered for PTEs from anthropogenic sources: As (8.0-86.9%), Cu (3.4-67.8%), Pb (9.1-106.2%) and Zn (2.4-77.5%). Graphs of bioaccessibility adjusted assessment criteria (BAAC) were derived for each urban land use type and PTE. These provide a visual representation of the significance of oral bioaccessibility when deriving BAAC and how this is affected by 1) dominant exposure pathways for each land use and 2) relative harm posed from exposure to PTEs via each pathway, allowing oral bioaccessibility research to be targeted to contaminants and pathways that most significantly impact risk assessment. Pb was the most widespread contaminant with 16.5% of sites exceeding the Pb GAC. Applying BAAC did not significantly change risk evaluation for these samples as many had Pb BAF>50%. In contrast, all samples that exceeded the As GAC were found to no longer exceed a minimal level of risk when oral bioaccessibility was considered. Oral bioaccessibility testing resulted in a 45% reduction in the number of sites identified as posing a potential risk to human health.

Assessment of source-oriented health risk associated with the oral ingestion of heavy metals in dust within an iron/steel smelting-affected area of the North China Plain

Heavy metals (HMs) from iron/steel smelting activities pose notable risks to human health, especially to those living around industrial facilities of North China Plain, the base of China's steel production. In this study, 78 outdoor windowsill dust samples were collected around a large-scale iron/steel smelter with more than 65 years of production history in the western North China Plain. Nine HMs were analysed to comprehensively assess the health risks by integrating Monte Carlo simulation, oral bioaccessibility, and source apportionment. Results showed serious pollution with Cd, Pb, and Zn based on their geo-accumulation index values and concentrations. Four potential sources including industrial sources (49.85%), traffic sources (21.78%), natural sources (20.58%), and coal combustion (7.79%) were quantitatively identified by multivariate statistical analysis. The oral bioaccessibilities of HMs determined by the physiologically based extraction test ranged from 0.02% to 65.16%. Zn, Mn, Cd, and Pb had higher bioaccessibilities than other HMs. After incorporating oral bioavailability adjustments, noncarcinogenic and carcinogenic risks were significantly reduced, especially for adults. The mean hazard index (HI) for children and adults was below the safety threshold (1.0), whereas the mean of the total carcinogenic risk (TCR) based on HM bioaccessibilities in the gastric phase remained above the acceptable level (1.0E-06) (children: 5.20E-06; adults: 1.16E-06). Traffic sources warranted increased concern as it substantially increased TCR. Cd was identified as the priority pollution in iron/steel smelting areas. Assessing source-oriented health risks associated with oral ingestion exposure can guide the management and control of HM contamination within iron/steel smelting-affected areas.

Assessment of heavy metal contamination in street dust: concentrations, bioaccessibility, and human health risks in coal mine and thermal power plant complex

Coal mining has also been associated with adverse environmental and health impacts including cancer and respiratory disorders, with the presence of thermal power plants exacerbating the problem of heavy metal pollution. Minimal studies have been conducted on the environmental impacts, health risks, and bioaccessibility of heavy metals in coal mine areas. Consequently, samples of street dust were collected from different locations in the Singrauli mine complex and analysed. Heavy metals (Cu, Ni, Zn, Cr, Co, As, and Mo) were found to be higher than the background concentration, with the maximum concentration was found in areas close to the Thermal Power Plants, like Near Vindyachal TPP, Near Shakti Nagar TPP, and Anpara. The highest geo-accumulation index value was found for Co, Mo, Zn, and As, indicating moderate to strong pollution levels. Health risk assessment (for both adults and children) revealed that Cr and Fe posed significantly higher Hazard Quotient and Hazard Index (HI) values, indicating significant non-carcinogenic threats. Moreover, Carcinogenic Risk (CR) values for Cd, Cr, and Ni indicated a risk of carcinogenicity to the public exposed to road dust. The study also examined the bioaccessibility of the metals, which showed that the gastric phase accumulated a higher percentage of Ni (42.52%), Pb (34.79%), Co (22.22%), As (20%) and Cu (15%) than the intestinal phase. Strong positive correlation was observed between metal concentration (Cu, Pb, Cr, Fe, Zn, and Mn), HI, and CR of adult and child, while bioaccessibility of intestinal phase was positively correlated with gastric phase of metals (Cu, Ni, Co, As, and Mn).

Extraction methods optimization of available heavy metals and the health risk assessment of the suburb soil in China

Heavy metal pollution has attracted increasing concern due to its high toxicity and persistence. A suitable extraction procedure for available heavy metals in soil is necessary for assessing the ecological risk. In this work, the single extraction methods aided by shaking and microwaves were investigated and analyzed for their ability to extract available heavy metals from soil samples, and a total of 42 soil samples were collected from suburbs of Zhengzhou city in China. The extraction efficiency of Cu, Zn, As, and Cd in the certified fluvo-aquic soil was compared using eight different types of solutions: CaCl2, CH3COONH4, NH4NO3, CH3COOH, Na2EDTA, DTPA, HNO3, and NH4H2PO4. Results indicated that the shaking-assisted method that utilized Na2EDTA as an extractant demonstrated satisfactory efficiency and was chosen for further optimization and that the optimal conditions were obtained using 0.05 M Na2EDTA at pH 7, soil-liquid ratio 1:20, and extraction duration 2 h, which gained the perfect extraction efficiency ranging from 85.8 to 109.5%. The proposed approach has been applied to extract available Cu, Zn, As, and Cd in soils of Zhengzhou suburbs, where the mean values varied from 0.129 to 6.881 mg/kg. The bioavailability of different heavy metals in the soil varies greatly, with Cd having the highest activity in the survey region. Significant (p < 0.01) positive relationships were observed between the available state and the total amount of all the heavy metals. The assessment of health risks associated with heavy metals indicated that there was no risk for chronic non-carcinogenic effects. Even though the total amount of metal elements in suburban soil of Zhengzhou is 1.6% with high carcinogenic risk, the risk of available elements is still within the acceptable range, which verified that the risk grade obtained by the total amount is higher than the actual risk.

Biomonitoring trace metal contamination in Guangzhou urban parks using Asian tramp snails (Bradybaena similaris)

Anthropogenic activities have caused environmental metal contamination in urban areas. Biomonitoring using organisms such as invertebrates can evaluate metal pollution, supplementing chemical monitoring, which cannot comprehensively reflect how metals influence organisms in the urban environment. To assess metal contamination in Guangzhou urban parks and its source, Asian tramp snails (Bradybaena similaris) were collected from ten parks in Guangzhou in 2021. The metal concentrations (Al, Cd, Cu, Fe, Mn, Pb, and Zn) were measured by ICP-AES and ICP-MS. We evaluated the metal distribution characteristics and correlations among metals. The probable sources of metals were determined by the positive matrix factorization (PMF) model. The metal pollution levels were analysed using the pollution index and the Nemerow comprehensive pollution index. The mean metal concentrations were ranked Al > Fe > Zn > Cu > Mn > Cd > Pb; metal accumulation in the snails was ranked Al > Mn > CuFe > Cd > Zn > Pb. Pb-Zn-Al-Fe-Mn and Cd-Cu-Zn were positively correlated in all samples. Six major metal sources were identified: an Al-Fe factor corresponding to crustal rock and dust, an Al factor related to Al-containing products, a Pb factor indicative of traffic and industries, a Cu-Zn-Cd factor dominated by the electroplating industry and vehicle sources, an Mn factor reflecting fossil fuel combustion, and a Cd-Zn factor related to agricultural product use. The pollution evaluation suggested heavy Al pollution, moderate Mn pollution, and light Cd, Cu, Fe, Pb, and Zn pollution in the snails. Dafushan Forest Park was heavily polluted; Chentian Garden and Huadu Lake National Wetland Park were not widely contaminated. The results indicated that B. similaris snails can be used as effective biomarkers for monitoring and evaluating environmental metal pollution in megacity urban areas. The findings show that snail biomonitoring provides a valuable understanding of the migration and accumulation pathways of anthropogenic metal pollutants in soil‒plant-snail food chains.

Health risk assessment of heavy metals in road dust from the fourth-tier industrial city in central China based on Monte Carlo simulation and bioaccessibility

Health risks caused by heavy metal (HM) exposure in road dust has attracted extensive attention, but few studies have focused on the health risks of residents living in small- and medium-sized cities with rapid industrialization and urbanization. Thus, 140 road dust samples were collected across Anyang, a typical fourth-tier industrial city in central China, which were analysed for 10 different HMs (Mn, Zn, Pb, V, Cr, As, Cd, Ni, Cu and Co). Monte Carlo simulation and bioaccessibility were used to quantify the health risks of heavy metals comprehensively in road dust. Results revealed a remarkable accumulation of Mn, Zn, Pb, Cd and Cu. According to the Geo-accumulation index and potential ecological risk index, Cd was priority control pollutant. Moreover, 55.0% of the road dust samples reached heavily polluted level, and 52.86% of the samples were at high ecological risk levels. These results illustrated that HM contamination was serious and universal in the road dust of Anyang. The occurrences of HMs were allocated to traffic emissions, natural sources, industrial activities and agricultural activities with contribution rates of 35.4%, 6.0%, 41.6% and 17.0%, respectively. Except for Zn in the gastric phase, all other HMs had relatively low bioaccessibilities in the gastrointestinal system, usually less than 20%. The bioaccessibilities of most HMs were higher in the gastric phase, except for Cr, Ni and Cu, which remained higher in the intestinal phase. The non-carcinogenic risk and carcinogenic risk were remarkably reduced when considering the HM bioaccessibilities in the gastrointestinal system, especially for adults. The outcomes of this paper are valuable for understanding HM contamination in road dust and highlight the importance of risk assessment for populations living in the fourth- and fifth-tier cities.

Heavy metal(loid)s in agricultural soil from main grain production regions of China: Bioaccessibility and health risks to humans

Unintentional ingestion of metal-contaminated soils may pose a great threat to human health. To accurately evaluate the health risks of heavy metal(loid)s in soils, their bioaccessibility has been widely determined by in vitro assays and increasingly employed to optimize the assessment parameters. Given that, using meta-analysis, we analyzed the literature on farmland heavy metal(loid)s (As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn) in Chinese main grain production regions, and collected their total and bioaccessibility data to accurately assess their human health risks. Monte Carlo simulation was used to reduce the uncertainty in metal concentration, intake rate, toxicity coefficient, and body weight. We found that the mean concentration (0.47 mg/kg) and geological accumulation index (I_geo, 0-5.24) of Cd were the priority position of controlling metals. Moreover, children are more vulnerable to carcinogenic risks than adults. Soil mineralogy, physicochemical properties, Fe, and the types of in vitro assays are the influencing factors of bioaccessibility discrepancy. Furthermore, appropriate bioaccessibility determination methods can be adapted according to the differences in ecological receptors for the risk assessment, like developing a "personalized assessment" scheme for polluted farmland soil management. Collectively, bioaccessibility-based models may provide an accurate and effective approach to human health risk assessment.

Trace Metal(loid) Migration from Road Dust to Local Vegetables and Tree Tissues and the Bioaccessibility-Based Health Risk: Impacts of Vehicle Operation-Associated Emissions

Traffic activities release large amounts of trace metal(loid)s in urban environments. However, the impact of vehicle operation-associated emissions on trace metal(loid) enrichment in road dust and the potential migration of these trace metal(loid)s to the surrounding environment remain unclear. We evaluated the contamination, sequential fraction, and bioaccessibility of trace metal(loid)s in urban environments by assessing their presence in road dust, garden vegetables, and tree tissues, including bark and aerial roots, at a traffic-training venue impacted by vehicle operation emissions and, finally, calculated the bioaccessibility-based health risk. The results indicated a significant accumulation of trace metal(loid)s in road dust, with the highest lead (Pb), cadmium (Cd), and antimony (Sb) concentrations in the garage entrance area due to higher vehicle volumes, frequent vehicle starts and stops, and lower speeds. Aerial roots exposed to hill start conditions exhibited the highest Pb, Zn, and Sb levels, potentially caused by high road dust resuspension, confirming that this tree tissue is an appropriate bioindicator. Sequential extraction revealed high percentages of carbonate-, Fe/Mn oxide-, and organic/sulphide-associated fractions of Pb, copper (Cu), and zinc (Zn) in road dust, while most Cd, Cr, Ni, and Sb occurred as residual fractions. According to the potential mobilizable fractions in sequential extraction, the in vitro gastrointestinal method could be more suitable than the physiologically based extraction test to evaluate the bioaccessibility-related risk of traffic-impacted road dust. The bioaccessibility-based health risk assessment of the road dust or soil confirmed no concern about noncarcinogenic risk, while the major risk originated from Pb although leaded gasoline was prohibited before the venue establishment. Furthermore, the cancer risks (CRs) analysis showed the probable occurrence of carcinogenic health effects from Cd and Ni to adults and from Cd, Cr, and Ni to children. Furthermore, the Cd and Pb concentrations in the edible leaves of cabbage and radish growing in gardens were higher than the recommended maximum value. This study focused on the health risks of road dust directly impacted by vehicle emissions and provides accurate predictions of trace metal(loid) contamination sources in the urban environment.

Towards an integrated health risk assessment framework of soil heavy metals pollution: Theoretical basis, conceptual model, and perspectives

The health risk of soil heavy metals pollution has been gaining increasing public concern. However, many countries have not set their own health risk assessment (HRA) framework and most of the existing studies directly referred to the USEPA risk assessment model and parameters. For those countries that do not propose an original HRA framework, the experience of developed countries is crucial for advancing their own HRA system. This study systematically reviewed the development of HRA framework in some representative developed countries. The theoretical basis, conceptual model, progress, and challenges of HRA researches concerning soil heavy metals pollution were summarized. By recalling and comparing the health risk-related laws and guidance in the USA, UK, and Japan, results showed that the construction of HRA framework varied between these countries, but HRA has become the main method for deriving their soil environmental criteria. We further summarized the evaluation scales, land use types, exposure pathways, and sensitive receptors of HRA studies, and highlighted the key parameters affecting health risk outputs. There has been a shift toward the incorporation of probabilistic modeling, metals bioavailability, and sources emission characteristics into recent HRA studies. Nonetheless, challenges remained on how to minimize the uncertainty of generating probability distribution and detecting metal bioavailability. To facilitate the development of HRA framework, it was advised that developing countries should strengthen the theoretical researches of health risk and localization researches of exposure factors. Future directions are suggested to tend to: 1) promote sensitive analysis to quantify the impact of distribution assumptions on health risk outputs, 2) derive reasonable risk threshold and consistent evaluation protocol for bioavailability-based health risk assessment method, and 3) strive to explore the combined health effect of exposure to heavy metals in soil through source-media-receptor integrated studies.

In Vitro Bioaccessibility and Health Risk Assessment of Arsenic and Zinc Contaminated Soil Stabilized by Ferrous Sulfate: Effect of Different Dietary Components

Iron-based materials have good stability in reducing the mobility and toxicity of heavy metals, but the behavior and human health risks of heavy metals could be affected by dietary components. This study investigated the effect of typical diets (lettuce, cooked rice and apples) on the bioaccessibility and morphological changes of arsenic (As) and zinc (Zn) in contaminated site after stabilization by ferrous sulfate (FeSO4). The results showed that the bioaccessibility of As and Zn were increased in a co-digestion system of food. The augmented effect on As bioaccessibility mainly occurred in the gastric phase: apple > lettuce > cooked rice (p < 0.05), while the augmented effect on Zn bioaccessibility mainly occurred in the intestinal phase: lettuce > apple > cooked rice (p < 0.05). FeSO4 weakened the dissolution effect of dietary components on As bioaccessibility, and reduced As bioaccessibility in the gastric and intestinal phases by 34.0% and 37.9% (p < 0.05), respectively. Dietary components and Fe fractions influenced the speciation and distribution of As and Zn. FeSO4 reduced the hazard quotient (HQ) and carcinogenic risk (CR) values of the contaminated soil by 33.97% and 33.59%, respectively. This study provides a reference for a better understanding of more realistic strategies to modulate exposure risks of heavy metal-contaminated sites.

Geochemical Contamination, Speciation, and Bioaccessibility of Trace Metals in Road Dust of a Megacity (Guangzhou) in Southern China: Implications for Human Health

Road dust has been severely contaminated by trace metals and has become a major health risk to urban residents. However, there is a lack of information on bioaccessible trace metals in road dust, which is necessary for an accurate health risk assessment. In this study, we collected road dust samples from industrial areas, traffic intersections, and agricultural fields from a megacity (Guangzhou), China, and conducted a geochemical enrichment, speciation, and bioaccessibility-based health risk assessment of trace metals. In comparison with local soil background values, the results revealed a significant accumulation of trace metals, including Zn, Cd, Cu, and Pb in the road dust, which is considered moderate to heavy pollution. Sequential extraction indicated that most trace metals in the road dust were primarily composed of a Fe/Mn oxide-bound fraction, carbonate-bound fraction, and residual fraction, while the dominant fraction was the organic matter-bound fraction of Cu, and the residual fractions of As, Cr, and Ni. The in vitro gastrointestinal (IVG) method revealed that high percentages of Zn, Cd, Cu, and As were bioaccessible, suggesting the possible dissolution of trace metals from adsorbed and carbonate-associated fractions in road dust exposed to the biological fluid matrix. The IVG bioaccessibility-based concentration largely decreased the noncarcinogenic health risk to a negligible level. Nevertheless, the entire population is still exposed to the cumulative probability of a carcinogenic risk, which is primarily contributed to by As, Cd, Cr, and Pb. Future identification of the exact sources of these toxic metals would be helpful for the appropriate management of urban road dust contamination.

Multi-geostatistical analyses of the spatial distribution and source apportionment of potentially toxic elements in urban children's park soils in Pakistan: A risk assessment study

In the past few decades, contamination of urban children's parks (UCPs) with potentially toxic elements (PTEs) has been attracting more and more interest; however, assessment of eco-environmental and child exposure risks particularly in developing countries remains limited. The current study investigated PTE (Cr, Ni, Zn, As, Cd, and Pb) concentrations, potential sources, and their health risk assessment in UCP soils of 12 major cities in Pakistan. The results showed that the mean concentration of Ni exceeded the SEPA-permissible limit in all UCP sites, while other PTEs were found to be within acceptable limits. The soil properties such as pH, electrical conductivity, organic matter, and soil particles size were determined in UCPs soils. The contamination factor and pollution load index results indicated low to moderate pollution levels (CF < 3) and (PLI<1) for all PTEs except Ni in some of the selected cities. Quantile-quantile (Q-Q) plotting determined the normal distribution line for all PTEs in the UCPs. Principal component analysis showed the mixed sources of contamination from industrial emissions, fossil fuel combustion, vehicular emissions, wastewater irrigation, as well as solid waste disposal and natural sources of soil parent materials in all park sites. ANOVA results showed that all the PTEs except Cd had moderate to higher contamination values than the reference site. The risk assessment study revealed that children had high exposure to the selected PTEs via all exposure pathways. The hazard index (HI) mean value (1.82E+00) of Ni for all exposure pathways was greater than 1, while total risk value of Cr (1.00E-03) had exceeded USEPA limit, indicating cancer risk. Consequently, the study of UCPs soils revealed PTEs contamination that could pose a potential health risk to the local population in the studied UCPs regions of Pakistan. Thus, the present study recommends that the influx of PTEs originating from natural and anthropogenic sources should be mitigated and government should implement strict enforcement of environmental regulations and proper management, as well as air quality monitoring guidelines for public health should be strictly adopted to reduce traffic- and industrial emission-related to PTEs in metropolitan areas.

Potential ecological and health risks of heavy metals for indoor and corresponding outdoor dust in Hefei, Central China

The harm caused by indoor dust has received increasing attention in recent years. However, current studies have ignored comparisons with the corresponding outdoor dust. This study aimed to investigate the distribution of heavy metals in indoor and corresponding outdoor dust and the ecological and health risks they pose in Hefei, Central China. We analyzed O/I (outdoor/indoor concentration ratios) values, background comparison, and correlation analysis (heavy metal concentrations vs. particle size) and found that Cu, Zn, and Cd mainly existed in indoor sources, while V, Co, and As mainly existed in outdoor sources, and both family sizes and floor number influenced the variation of O/I. Through a new potential ecological risk assessment method, we determined that Cd risk levels in indoor and outdoor dust were extreme and high to extreme, respectively. Additionally, the carcinogenic risks of Ni, As, and Cr were not negligible. The risk of indoor dust was higher than that of outdoor dust for the heavy metals studied, implying a poor indoor environment. Notably, indoor dust from families with smaller sizes, lower floors, and smokers had higher ecological and carcinogenic risks.

Contamination and source-specific risk analysis of soil heavy metals in a typical coal industrial city, central China

Source-specific risk apportionment for soil heavy metals (HMs) is crucial for pollution mitigation and risk control in coal-mining areas. The ecological and human health risks resulting from different sources were evaluated through an integrated method that combines risk assessments with positive matrix factorization (PMF) model. Thirty soil samples were collected from a typical coal-mining city in central China and analyzed for six HMs (Cu, Ni, Pb, Cd, As, and Hg). The results indicate that surface soil in the study area suffered from moderate HMs pollution, especially pollution by Cd and Hg. Four potential sources of soil HMs were identified and quantified in the study area, including natural source (27.7%), traffic emissions (33.4%), agricultural practices (16.2%), and industrial activities (22.7%). The ecological risk of the study area was at moderate level, and the leading contributions in urban and suburban areas were from industrial activities and agricultural practices, respectively. The non-carcinogenic risks for adults and children were lower than the risk threshold, while the carcinogenic risks ranged between 1E-06 and 1E-04, suggesting that carcinogenic risks and hazards to human health should not be neglected. Traffic emissions and natural sources mainly contributed to the non-carcinogenic and carcinogenic risks, due to the strong non-carcinogenicity and carcinogenicity of As and Ni. These findings highlight the ecological and health risks linked to potential sources of soil HMs contamination and provide valuable information on the reduction of corresponding risks for local environmental managers.

COVID-19 and urban rivers: Effects of lockdown period on surface water pollution and quality- A case study of the Zarjoub River, north of Iran

Due to the spreading of the coronavirus (COVID-19) in Iran, restrictions and lockdown were announced to control the infection. In order to determine the effects of the lockdown period on the status of the water quality and pollution, the concentrations of Al, As, Ba, Cr, Cu, Mo, Ni, Pb, Se, and Zn, together with Na+, Mg2+, Ca2+ and electrical conductivity (EC), were measured in the Zarjoub River, north of Iran, in both pre-lockdown and post-lockdown periods. The results indicated that water pollution and associated human health risk reduced by an average of 30% and 39%, respectively, during the lockdown period. In addition, the multi-purpose water quality index also improved by an average of 34%. However, the water salinity and alkalinity increased during the lockdown period due to the increase of municipal wastewater and the use of disinfectants. The major sources of pollution were identified as weathering, municipal wastewater, industrial and agricultural effluents, solid waste, and vehicular pollution. PCA-MLR receptor model showed that the contribution of mixed sources of weathering and municipal wastewater in water pollution increased from 23 to 50% during the lockdown period. However, the contribution of mixed sources of industrial effluents and solid wastes reduced from 64 to 45%. Likewise, the contribution of traffic-related sources exhibited a reduction from 13% in the pre-lockdown period to 5% together with agricultural effluent in the post-lockdown period. Overall, although the lockdown period resulted in positive impacts on diminishing the level of water pollution caused by industrial and vehicular contaminants, the increase of municipal waste and wastewater is a negative consequence of the lockdown period.

Urbanization influences the distribution, enrichment, and ecological health risk of heavy metals in croplands

The contamination of urban soils with heavy elements due to the rapid development of urbanization and urban services has become a major environmental and human health challenge. This study provides insight into the urbanization controls on combined pollution severity and health risk potential of heavy metals in corn-cultivated urban versus non-urban soils. A multifaceted assessment was conducted using enrichment factor (EF), ecological risk (ER), bioconcentration factor (BCF), transmission factor (TF), hazard index (HI), and carcinogenic risk (CR). The results indicate a significant increase in the concentration of all metals in urban farmlands. When compared to the non-urban soils, EF implies a significant increase of all metals in the urban soil, downgrading this index from minimal enrichment (EF < 2) in the control soils to moderate enrichment (2 ≤ EF < 5) in the urban soils. Likewise, the average ER value showed an increase in the urban soils than in the control soils in the order of Fluvisols (66.6%) > Regosols (66.1%) > Cambisols (59.8%) > Calcisols (47%). The BCF and TF values for different elements decreased in the order of Cd (0.41-0.92) > Cu (0.1-0.23) > Zn (0.1-0.18) > Ni (0.01-0.03) > Pb (0.005-0.011) and Zn (0.75-0.94) > Cu (0.72-0.85) > Pb (0.09-0.63) > Cd (0.17-0.22) > Ni (0.01-0.21), respectively, which indicates that certain metals were not mobilized to the extent that they had been accumulated in the plant roots. The total carcinogenic risk was ranged from 5.88E-05 to 1.17E-04 for children and from 1.17E-04 to 2.30E-04 for adults, which implies a greater associated health risk for children.

Urinary heavy metals in residents from a typical city in South China: human exposure and health risks

Although heavy metal pollution has developed into a major global environmental problem, most research has focused on specific elements, especially arsenic (As) and selenium (Se), and on the health risks to people in polluted areas or by occupation. This study investigated the urine of 480 participants from Guangzhou with a population of 18 million and targeted nine heavy metals: As, Se, chromium (Cr), manganese (Mn), nickel (Ni), cadmium (Cd), lead (Pb), antimony (Sb), and mercury (Hg). The heavy metals were widely detected, of which As, Se, Cd, and Pb all exceed 98%. Among the toxicants, As showed the highest concentration, followed by Se with 40.5 and 35.4 μg/L, respectively. The heavy metal levels from suburban subjects were generally higher than those in urban subjects (except for Sb), and the Cd level of males was lower than that of females. Concentrations were related to age, body mass index, alcohol consumption, and smoking. According to the health risk assessment, most subjects experienced potential non-carcinogenic risk from As, Cd, Se, and Hg, which accounted for 38.2%, 8.83%, 8.31%, and 3.38%, respectively. The carcinogenic risk of As and Cd surpassed the risk level of 10^-6, and 90.1% and 35.4% of the subjects, respectively, exceeded 10^-4, an unacceptable risk level. More attention to the high carcinogenic risk from heavy metals and the high detected levels of As and Cd is required.

Heavy metals in soil from gangue stacking areas increases children health risk and causes developmental neurotoxicity in zebrafish larvae

Coal is the main energy source in China, with 4.5 billion metric tons of coal gangue accumulating near the mining areas in the process of coal mining. The objectives of the present study were to identify the health risks to children from soil pollution caused by coal gangue accumulation and to clarify the possible developmental neurotoxicity caused by this accumulation using zebrafish (Danio rerio) as a model. The results reveal that As and seven other heavy metals in soil samples from the gangue dumping area to the downstream villages exhibited distance-dependent concentration variations and posed substantial potential non-carcinogenic risks to local children. Additionally, soil leachate could affect the key processes of early neurodevelopment in zebrafish at critical windows, mainly including the alterations of cytoskeleton regulation (α1-tubulin), axon growth (gap43), neuronal myelination (mbp) and synapse formation (sypa, sypb, and psd95), eventually leading to hypoactivity in the zebrafish larvae. These findings suggest the possible health risks of soil pollution in the coal gangue stacking areas to children, particularly affecting their early neurodevelopment.

A novel method to analyze the spatial distribution and potential sources of pollutant combinations in the soil of Beijing urban parks

Organic and inorganic pollutants are often co-sedimentary in soils and have the same sources in the urban environment. The identification of the sources and distribution of combined pollutants is a basic step in risk management. In this study, the levels of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) were measured in urban park soils in Beijing. Bivariate local Moran's I and positive matrix factorization (PMF) source apportionment were used to identify the spatial clustering patterns and potential sources of PAHs and HMs, as well as to ultimately define a pollution risk control area. The results revealed an obvious clustered distribution of PAHs and HMs in the park soils. High-high areas were defined as sites containing a complex mixture of pollutants, which were mainly located in the center and north of Beijing. High-low and low-high areas were located outside the city center but had the potential for combined pollution, and therefore require continuous attention. Bivariate local indicators of spatial association (LISA) enabled a more accurate analyses of the mechanism controlling the spatial distribution of PAH and HM combinations in urban parks. The source apportionment indicated that industrial and traffic emissions were the most important sources of the pollutant combinations in urban parks, with traffic emissions accounting for most of the pollution.

Assessment of Soil Contamination with Potentially Toxic Elements and Soil Ecotoxicity of Botanical Garden in Brno, Czech Republic: Are Urban Botanical Gardens More Polluted Than Urban Parks?

Though botanical gardens are an important and widely visited component of urban green spaces (UGS) worldwide, their pollution is rarely studied. The aim of this study was to assess botanical garden soil contamination and ecotoxicity and to evaluate whether urban botanical gardens are more contaminated than urban parks. Soil assessments showed serious contamination with Cd, Pb and Zn, emitted predominantly by traffic, agrochemicals and past construction and demolition waste. The discovery of hazardous historical ecological burden in the UGS calls for the necessity of detailed surveys of such areas. Despite prevailing moderate-to-heavy contamination, the soil was only slightly ecotoxic. Maximum immobilisation inhibition of Daphnia magna reached 15%. Growth of Sinapis alba L. was predominantly stimulated (73%), and Desmodesmus subspicatus Chodat was exclusively stimulated, possibly due to soil alkalinity and fertiliser-related nutrients. The hypothesis of a higher contamination of urban botanical gardens compared to urban parks was confirmed. However, urban parks can face a greater risk of soil ecotoxicity, hypothetically due to decreased activity of soil organisms resulting from adverse soil conditions caused by active recreation. The results highlight the need for an increased focus on botanical and ornamental gardens when assessing and managing UGS as areas potentially more burdened with contamination.

Heavy Metals in Indoor Dust Across China: Occurrence, Sources and Health Risk Assessment

In this study, the occurrence of heavy metals including cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) was investigated in indoor dust samples collected from 33 urban and rural areas in 11 provinces, China. The concentrations of the selected heavy metals were determined by an inductively coupled plasma mass spectrometry. The mean concentrations of Zn (166 mg kg^-1), Pb (40.7 mg kg^-1), Cr (19.8 mg kg^-1), Cu (16.9 mg kg^-1), and Cd (2.29 mg kg^-1) in indoor dust are in low or moderate levels compared with other countries or regions. Cd was significantly enriched with the highest enrichment factor of 23.7, followed by Zn, Pb, Cu, and Cr, which were all lower than 3. The concentrations of Pb from Northern China (61.4 mg kg^-1) were significantly higher than those from Southern China (8.88 mg kg^-1). The concentrations of heavy metals in indoor dusts from rural areas were higher than those from urban areas except for Cu. The multivariate analysis of variance revealed that wall cover, fuel types, and air conditioning were dominant factors influencing the levels of heavy metals in indoor dust. Principal component analysis showed that outdoor dust and wall paint were main factors for the high concentrations of Cd, Pb, and Cr, accounting for 40.6% of the total contribution; traffic sources contributed to the high levels of Cu and Zn explained 20.6% of the total variance. The hazard indexes of selected heavy metals were less than 1 and carcinogenic risk value of Cr were between 1.01 × 10^-6 and 1 × 10^-4, indicating minor noncarcinogenic and carcinogenic risks from heavy metals in indoor dust for residents in China. Pb contributed 72.0% and 86.9% to the sum of noncarcinogenic risk values of selected heavy metals for adults and children, respectively. The carcinogenic risk value of Cr was approximately 13-fold higher than that of Cd for both adults and children. Children endured higher risks from heavy metals in indoor dust compared with adults.

In vitro bioaccessibility, phase partitioning, and health risk of potentially toxic elements in dust of an iron mining and industrial complex

Dust emitted from mining, ore processing, and tailing dumps have direct effects on miners who work close to these operations. The Gol-E-Gohar (GEG) mining and industrial company is one of the most important iron concentrate producers in the Middle East. The objective of the present study was to estimate the distribution, fractionation, and oral bioaccessibility of potentially toxic elements (PTEs) in dust generated by the GEG mining and industrial company. Total PTE content including Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, V, and Zn was quantified for suspended particulate matter (PM) in PM_2.5, PM₁₀, and total suspended particulate matter (TSP). As, Cd, Co, Cu, Fe, Ni, and Pb were quantified in fallout dust samples for oral bioaccessibility using in vitro Unified BARGE (UBM) Method and modified BCR fractionation analysis. Enrichment factors (EF) were calculated for the studied elements in PM; Cu, Fe, and As were found to be extremely enriched. Oral bioaccessibility of selected PTEs in fallout dust samples ranged from 0.35% to 41.55% and 0.06-37.58% in the gastric and intestinal phases, respectively. Regression modeling revealed that the bioaccessibilities of the PTEs could mostly be explained by total concentrations in dust particles. Average daily intake (ADI) calculations revealed that the intake of PTEs did not exceed the tolerable daily intake (TDI) values and as such was not considered a significant risk to workers. Additionally, the hazard quotients (HQ) and carcinogenic risk (CR) values were lower than the acceptable level. This study can provide further risk assessment and management of PTE pollution in occupational environments.

Oceanic karma? Eco-ethical gaps in African EEE metal cycle may hit back through seafood contamination

The increasing global demand for electric and electronic equipment (EEE) such as smartphones, tablets and electric car batteries has resulted in an increase in heavy metal releases to the environment at different steps during its manufacture (e.g. mining, extraction, production and e-waste). Some critical raw materials (CRMs) that supply the worldwide demand of technology are mainly sourced from Africa, but their resulting heavy metal pollution can reach citizens from other regions of the world through seafood caught in African waters, which would act as a vector. In this study, we review heavy metal contents in African fish and, as proof of concept, we analyse heavy metal content in three tuna species (Thunnus alalunga, T. albacares and T. obesus) caught in different regions inside the Sustainable Fisheries Partnership Agreements (SFPAs) by Spanish fleets and commercialised in Spain. Thunnus alalunga and T. albacares from African waters had higher concentrations of heavy metals (especially Hg but also As and Pb) in muscle than samples of the same species caught in other waters. Metal profiles in tunas from African waters were significantly correlated with those of continental and coastal fish from nearby areas impacted by mines and e-waste, as found in the literature review. Based on these results we identify research priorities that should be addressed in order to improve the social and environmental sustainability of EEE metal manufacture in Africa.

Human health and ecological risk assessment of trace elements in urban soils of 101 cities in China: A meta-analysis

Urban soils pollution by trace elements arouses the growing interest in China. The aim of this study was to assess urban soil pollution by As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in China and the possible impacts on urban inhabitants and urban green spaces (UGS). Data from more than 17,000 samples were applied to characterize the status of 101 cities. The pollution assessment proved that 11% of the cities are heavily polluted. According to the Hazard Index, the value of risk for the infant population in 15 cities exceed the standardly accepted tolerable levels. The carcinogenic risk assessment demonstrated the potential threat in the cities with the total population approximately 20,566,900. Cr and As were detected to be the most hazardous elements. UGS may be seriously threatened by trace elements toxicity in 38 cities. Cd was found to be the riskiest element for UGS. Ecosystem services of UGS can be significantly disrupted under the current situation in China and their status is expected to deteriorate in the future. For this reason, it is essential to alter the policy of the urbanization process and develop functional concepts of urban green infrastructures adapted to the high level of contamination which shall improve human well-being in China.

Assessment of microbial and heavy metal contamination in shallow hand-dug wells bordering Ona River, Southwest Nigeria

Ona River is one of the three major rivers draining the city of Ibadan. Groundwater is the major source of drinking water in the metropolis; however, data on quality of shallow aquifers bordering Ona River is relatively scarce. This study aimed to evaluate bacteriological status, heavy metal content, and associated human and ecological health risks in hand-dug wells nearby Ona River. A total of 24 water samples from 12 sampling points were collected for chemical and microbial analyses. Heavy metals and microbial pathogens were analyzed using atomic absorption spectrometry and total plate count methods, respectively. Analyses of microbial and heavy metal (HMs) data showed that shallow hand-dug wells within the vicinity of Ona River were bacteriologically contaminated while most of analyzed heavy metals (except manganese) exceeded the drinking water quality standards. Interpretation of microbial and heavy metal (HMs) data identified predominance of anthropogenic activities as the major source of contamination in drinking water. Further scrutiny of HM data through integrated pollution indices identified two nearby wells (S₇ and S₈) exceed the safe limits and pose considerable risk to inhabitants. In terms of ecological risk index (ER), cadmium exhibited considerable to very high ER in all collected samples while manganese and zinc showed low ER in all analyzed water samples. Potential of non-carcinogenic risk through ingestion pathway in the study area was identified with the order of contributive ratios by HMs as Cd > Pb > Zn > Fe > Mn. The calculated target hazard quotient (THQ) due to ingested HMs for three human population categories exceeds the safe limit in the order of adult < children < infants. The study revealed the deteriorated state of waterside shallow hand-dug wells that need immediate actions by relevant stakeholders in water management. The study recommends improved hygienic practices, pretreatment of water before use, and most importantly, provision of potable pipe-borne water supply to the residents of the study area.

Relationship between Urban Green Spaces and Cancer: A Scoping Review

This scoping study aims to explore the relationships between urban green spaces (UGSs) and the onset, remission and recovery of cancer. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews (protocol published in 2018). Eligibility criteria for papers were: (1) to be concerned with UGSs, (2) reporting effects of UGSs on cancer-related outcomes including direct or indirect measures, (3) reporting randomized controlled trials, prospective cohort studies, case studies, observational studies, non-comparative studies, (4) in English or French. The search covered primary studies in the published and unpublished (grey) literatures searching by hand and electronic databases (MEDLINE, Green File, Cumulative Index to Nursing and Allied Health Literature and ScienceDirect). Among 1703 records screened by two reviewers independently, 29 were included for qualitative synthesis. We classify the cancers concerned and the effects reported i.e., protective effect, risk or without association. The most investigated cancers are bladder, breast and lung cancer. Our study also identified contributing factors and their mediating effects between UGSs and cancer. Even though the strength of the evidence of the associations between UGSs and cancer is still weak due to the low number of studies and their design, results highlight the wide variety of possible mediating factors between the use of green spaces and cancer occurrence, remission and/or prevention. Knowledge gaps and future research perspectives should be oriented to qualitative research on protective factors with an attention to equity in UGS access and use.

Spatial distribution, risk assessment, and source identification of heavy metals in water from the Xiangxi River, Three Gorges Reservoir Region, China

Heavy metals (HMs) contamination in rivers has attracted wide concern due to its persistence and potential risks to the natural environment and human health. In this study, eight HMs (As, Hg, Cu, Pb, Ca, Zn, Mn, and Ni) were measured by inductively coupled plasma mass spectrometry in 24 water samples to investigate HMs contamination levels in the Xiangxi River of the Yangtze River basin. A geographic information systems kriging interpolation method was used to reveal the spatial distribution of HMs contamination. The results indicate that most HMs occurred at acceptable levels below the Surface Water Quality Standard (GB 3838-2002), with the highest concentration (23.23 mg kg^-1) of Mn being observed at sampling site X20. The values of the potential ecological risk index (RI) suggest that high potential ecological risks were present at sampling sites X1, X3, X4, X14, X16, X17, and X24, which reached moderate risk level. The highest value of RI (279.56) was observed at site X17. HM spatial distributions show that upstream pollution is more severe than downstream. The hazard index was below 1 for all HMs except for Mn, indicating that HMs in Xiangxi River pose a low risk to human health. HM source identification was accomplished using principal component analysis and Pearson's correlation. Cu, Cd, Ni, and Hg originate primarily from agriculture, while Pb, Zn, and As originate primarily from transportation and mining. This research provides a reference on the risks posed by HMs in Xiangxi River and will support efforts to protect and improve water quality in Xiangxi River.

Phytoavailability and human risk assessment of heavy metals in soils and food crops around Sutlej river, India

We assessed the phytoavailability of heavy metals in wheat and rice grown on soils along flood plains of Sutlej river (India) and its effects on human health. Surface soil samples along with wheat (pre-monsoon season) and rice (post-monsoon season) grain samples were collected during the years 2017 and 2018. Soil samples were analysed for total and DTPA-extractable metals and, wheat and rice grains samples for total metals. There were no significant (p < 0.05) changes in total metal concentration during both the years, but the concentration of DTPA-extractable metals was higher during pre-monsoon than post-monsoon season. The concentration of Pb, Cd, and Co in wheat grains, whereas the concentration of Cr, Co, Pb and Cd in rice grains surpassed their safe limits. Both DTPA-extractable metals (water soluble plus exchangeable) and non-exchangeable fractions explained more than 80% of the variations in metal uptake by plants. The bioaccumulation factor for DTPA-extractable metals (BCF) was above one, but Pollution Load Index for these metals (PLI) was less than one. The carcinogenic risks due to ingestion of wheat and rice grains were higher for Cd. The BAF, PLI and health risks were higher along transboundary of the river. These results suggest that exchangeable and non-exchangeable fractions are contributing towards metals uptake by wheat and rice along flood plain soils of the Sutlej river and the present study may act as a model for carrying out similar studies to find out the risks of heavy metals and it effect on human health in future.

Trace elements in two particle size fractions of urban soils collected from playgrounds in Bratislava (Slovakia)

Today, it is proven that the contaminated urban soils are hazardous for the human health. Soil substrates of playgrounds call for special research as they are places where children are directly exposed to soil contaminants. Therefore, the objective of this work was to measure the pseudo-total contents and bioaccessibility of several metals and metalloids (As, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, V, Zn) in two grain sizes (< 150 μm and < 50 μm) of playground soils in Bratislava city (the capital of Slovakia). The content of metal(loid)s in the soils was controlled by a number of factors, with their increased contents (above 75% percentile or higher) at sites influenced by point sources of pollution (industry and agriculture) or at old sites located in the city centre. Cobalt, Cr, Fe, Mn, Ni and V had relatively uniform contents in soils compared to the other elements. As regression modelling with a categorical variable confirmed, the age of urban areas influenced the accumulation of As, Bi, Cd, Cu, Hg, Pb, Sb and Sn in playground soils. Exploratory statistical techniques with compositionally transformed data (principal component analysis, cluster analysis and construction of symmetric coordinates for correlation analysis) divided trace elements into the two main groupings, Co, Cr, Fe, Mn, Ni, V and Bi, Cd, Cu, Hg, Pb, Sb, Sn, Zn. Median concentrations of the elements in smaller soil grains (< 50 μm) were significantly higher than in coarser grains (< 150 μm). Cobalt, Cu, Mn, Pb, Sn and Zn had significantly higher bioaccessible proportions (% of the pseudo-total content) in < 50 μm soil size than in < 150 μm; however, the same order of bioaccessibility was achieved in both grain sizes. The highest bioaccessibility had Cd, Cu, Pb and Zn (~ 40% and more), followed by Co, As, Mn, Sb (18-27%), Hg, Ni, Sn (10-12%) and finally Cr, Fe and V (less than 4%). The hazard index and carcinogenic risk values were higher in < 50 μm than in < 150 μm and significantly decreased in the two soil sizes when the bioaccessibility results were included in the health hazard calculation.

Chemical fractionation and bioaccessibility of potentially toxic elements in area of artisanal gold mining in the Amazon

Artisanal mining may have modified the mobility, bioavailability and bioaccessibility of potentially toxic elements (PTEs) in the Serra Pelada gold mine, eastern Amazon, Brazil, which has not yet been studied. The objectives were to perform chemical fractionation of barium (Ba), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), and to determine the bioaccessibility of these elements in soils and mining wastes collected in agriculture, forest, mining, and urban areas from the influence zone of the Serra Pelada gold mine. Pseudo total concentrations were obtained by acid digestion, chemical fractionation was performed using the Bureau Community of Reference (BCR) sequential extraction, oral bioaccessibility was obtained by the Simple Bioaccessibility Extraction Test (SBET) and lung bioaccessibility was obtained through Gamble's solution. The pseudo total concentrations indicated contamination by Ba, Cu and Ni. The sequential extraction revealed the predominance of all elements in the residual fraction. However, Ba is in high concentrations in the greater mobility forms, ranging from 166.36 to 1379.58 mg kg^-1. Regardless of the area, Cr and Cu are more oral bioaccessible in the intestinal phase, and Zn in the gastric phase. Ba, Cr and Zn are not lung bioaccessible, while Cu, Ni and Pb are bioaccessible via inhalation. The PTEs studied deserve attention not only due to the high pseudo total concentrations found (which indicate potential risk), but also the concentrations in high mobility forms and bioaccessible fractions, especially in the areas of greatest anthropogenic occupation.

Improvement of water quality in the Pearl River Estuary, China: a long-term (2008-2017) case study of temporal-spatial variation, source identification and ecological risk of heavy metals in surface water of Guangzhou

A series of environmental protective policies have been taken recently in the Pearl River Estuary (PRE) to alleviate water pollution; however, their influence on the reduction of heavy metals in estuarine water has not been known. This study selected Guangzhou as a representative city in the PRE and collected estuarine water monthly from 2008 to 2017 to track the variation of As, Hg, Pb, Cd, Cu, Zn, and Se. During the last decade, the high time-resolved record showed that the concentration of Hg, Pb, Cd, Cu, and Zn in estuarine water reduced by 39.5%, 91.0%, 86.2%, 74.6%, and 97.3%, respectively. However, the concentration of As kept in a stable range (1.89-2.69 μg L^-1) and Se (0.17-0.65 μg L^-1) increased slightly. The principal component analysis (PCA) and absolute principal component scores-multiple linear regression (APCS-MLR) results suggested that the upstream industrial effluents were major sources for Hg (45.5-92.7%), Pb (47.3-100%), Cd (42.0-90.6%), Cu (85.5-100%), and Zn (100%) and the geogenic source was major origin for As (84.6-98.3%) and Se (0-67.5%). The risk quotient of Hg, Pb, Cd, Cu, and Zn to aquatic organisms largely decreased from 0.03, 0.59, 0.03, 2.06, and 0.26 in 2008 to 0.02, 0.05, 0.006, 0.52, and 0.007 in 2017, respectively. The effective control of heavy metal pollution in the study area can be primarily due to the relocation of hundreds of polluting factories during the last decade.

An Uncertainty Assessment of Human Health Risk for Toxic Trace Elements Using a Sequential Indicator Simulation in Farmland Soils

Toxic trace elements in farmland soils are potential threats to human health. In this study, we collected soil samples from the farmlands of southern Guangzhou. We used a sequential indicator simulation (SIS) to deal with the problem of skewed distribution in the sample data. We assessed the human health risks, as well as the uncertainties, of five toxic trace elements: arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and mercury (Hg). The results were as follows: (1) The risk indices of two trace elements (Cd and Hg) were less than the standard threshold, which means that there was no human health risk due to Cd and Hg in the study area. However, the maximum risk indices of As, Cr, and Pb exceeded the standard threshold. In particular, the maximum risk index of Pb was twice the standard threshold; (2) The risk probabilities of As and Cr were less than 25% in most areas, and only a few parcels of farmland have a 100% risk probability. The risk map of Pb was used to identify contiguous areas of high-risk probability (i.e., 75%–100%) in the center of the study area. (3) E-type estimation by the SIS method overestimates the risk when the number of samples with concentrations above the threshold have a large proportion of total samples. Our conclusions are as follows: (1) The simulation results show that areas with high-risk indices were concentrated in the Panyu District, which is close to the Pearl River and the core urban area of Guangzhou; (2) Except for Pb, these trace elements are not likely to pose health risks in southern Guangzhou; (3) This study considers the risk probability found with the SIS method to be more reliable for visualizing regional risk.

Metal(loid) bioaccessibility and children's health risk assessment of soil and indoor dust from rural and urban school and residential areas

This study focused on the oral bioaccessibility and children health risks of metal(loid)s (As, Cd, Cr, Cu, Ni, Pb and Zn) in soil/indoor dust of school and households from Lanzhou, China. The simple bioaccessibility extraction test method was applied to assess bioaccessibility, and children's health risk was assessed via statistical modeling (hazard quotients, hazard index and incremental lifetime carcinogenic risk). Metal(loid) content and bioaccessibility in indoor dust samples were significantly higher than those in corresponding soil samples (p < 0.05). The order for mean values of bioaccessibility of the elements in soil was as follows: Cd (57.1%) > Zn (44.6%) > Pb (39.9%) > Cu (33.2%) > Ni (12.4%) > Cr (5.3%) > As (4.4%), while for indoor dust, the order was: As (73.0%) > Cd (68.4%) > Pb (63.3%) > Zn (60.4%) > Cu (36.5%) > Ni (25.2%) > Cr (13.6%). The Pearson correlation coefficient showed that metal(loid) bioaccessibility was in general significantly negatively correlated to the Al, Fe and Mn contents. Neither noncarcinogenic nor carcinogenic risks exceeded the tolerance interval for 3-5- and 6-9-year-old children for all elements. They both were mostly attributed to As considering metal(loid)s types and to school indoor dust considering sources. Therefore, maintaining interior sanitation would be an effective measure to reduce the potential health effects of indoor dust on children.

Uptake of vegetable and soft drink affected transformation and bioaccessibility of lead in gastrointestinal track exposed to lead-contaminated soil particles

Accidental ingestion of Pb-contaminated soil particles by direct hand-to-mouth activity or by swallowing airborne dust particles is important pathway of human exposure to Pb. Appropriate evaluation of Pb risk to human is important in determining whether the soil needs remediation or not, however, there is paucity of data about the dietary influences on Pb bioaccessibility (Pb-BA) and transformation in humans. This study chose two typical foods, spinach and cola, representing vegetable and soft drink, respectively, and investigated their effects on Pb species in gastrointestinal tract using the physiologically based extraction test. Results showed that ingestion of spinach and cola decreased the Pb-BA by 52%-94% in the gastric phase and by 38%-95% in the intestinal phase, respectively. The reduction of Pb-BA by spinach was attributed to the precipitation of Pb with phosphorus in spinach and the sorption of Pb by the generated hydrolysate and un-hydrolysate from spinach in gastrointestinal tract. Cola decreased Pb-BA mainly via formation of insoluble Pb phosphates precipitates. Analysis of X-ray diffraction and MINTEQ modeling demonstrated that the dissolved Pb was transformed to precipitated or sorbed Pb with intake of cola or spinach. Our findings suggest that dietary habit greatly influence the speciation and subsequent Pb-BA in the gastrointestinal tract, which should be incorporated into human health risk assessment of Pb-contaminated soil.

Health risk assessment and bioaccessibilities of heavy metals for children in soil and dust from urban parks and schools of Jiaozuo, China

Urban parks and schools sever as the mainly activity areas for children, but risk assessment posed by heavy metals (HMs) from soil and dust in these area has rarely been investigated. In this study, six urban parks and seven schools in Jiaozuo, China, were taken as research objects to understand the contamination level and bioaccessibility of HMs from soil and dust in urban parks and schools. The results indicated that Zn, Cu, Pb, Cd, As, Ni and Co from soil and dust were above the background values, especially Zn and Cd in dust, and As and Cd in soil. Serious Cd pollution was discovered, and respective Cd concentrations in soil and dust were 17.83 and 7.52 times the background value. Additionally, the average concentration and bioaccessibility of Zn, Mn, Pb, Cd, Cr, Ni and Co in dust were both higher than in soil. High concentration and high bioaccessibility of HMs in dust suggested that HMs contamination were serious and universal in Jiaozuo. The concentrations of most HMs were higher in the gastric phase, except for Cu and Cd which remained higher in the intestinal phase. Both in the gastric phase and intestinal phase, Mn, As and Cd in soil and dust both have high bioaccessibility which all exceed 10%. The carcinogenic and non-carcinogenic risks base on the total HMs for children (soil: 7.93, 1.96E-05; dust: 6.44, 3.58E-05) were greater than those for adults (soil: 6.35E-01, 1.32E-05; dust: 5.06E-01, 2.42E-05), and urban parks and schools posed high potential risk for children. Therefore, assessment the risk posed by HMs contamination of soil and dust in urban parks and schools is vital and urgent for children.

A preliminary study on upstream migration of mangroves in response to changing environment along River Hooghly, India

Environmental changes and anthropogenic activities can be linked to altered distribution and abundance of species. However, the ecological impacts of change in the microenvironment have not been well documented. Herein, we have identified the distribution of mangroves and associated species and characterized surface sediment and water samples along the banks of River Hooghly. The application of Combined Mangrove Recognition Index (CMRI) and its validation with the available ground data on satellite image of 2015 indicates that some mangrove species have reclaimed the upper course of the river, which was earlier absent before 1995. This study is the first report on the upstream migration of mangrove species such as Sonneratia caseolaris, Sonneratia apetala, Derris trifoliata, Hibiscus tiliaceus, and Thespesia populnea in River Hooghly. The changes in pollution load, varied sedimentation pattern, high chemical oxygen demand, mean sea-level rise, and anthropogenic activity might have played a significant role in the upstream migration of mangroves.

Variations in stable carbon and nitrogen isotopes of particulate organic matter in surface waters of water-receiving area of Eastern Route of South-to-North Water Transfer Project, China

The purpose of this study was to assess the water quality and variations in stable carbon and nitrogen isotopes of particulate organic matter (δ¹³C_POM and δ¹⁵N_POM), as well as to evaluate the sources of carbon and nitrogen that contribute to the POM pools in lakes and reservoirs located in the water-receiving area of the Eastern Route of South-to-North Water Transfer Project (SNWTP) in Northern China. During each season from October 2013 to July 2014, samples of POM from 14 lakes and reservoirs in Northern China were collected. The lakes and reservoirs were meso-eutrophic with considerably high brackish ions (SO₄^2-, 173 mg/L; Cl^-, 296 mg/L) in Yangtze River lake, and high total nitrogen: total phosphorus ratio (averaged with 772) or dissolved inorganic nitrogen: soluble reactive phosphorus molar ratios (averaged with 1077) in mountainous reservoirs. The δ¹³C_POM, δ¹⁵N_POM, carbon to nitrogen (C/N) ratios showed significant seasonal variation, with ranges of - 32.5 to - 17.4‰, - 3.6 to 13.5‰, and 5.1-13.2, respectively, while they were hard to be distinguished among types of water sources. Principal component analysis (PCA) indicated that brackish ions, nutrients, and their molar ratios were the main factors influencing variations in δ¹³C_POM and δ¹⁵N_POM. δ¹³C_POM and C/N ratios suggested autochthonous primary production mainly contributed to POM during from April to October, while exogenous organic matter might mainly contribute these carbon pools in January. The low values of δ¹⁵N_POM (< 0‰) and negative correlation between δ¹⁵N_POM and TN suggested discharge of agricultural waste water (e.g., fertilizers, irrigation tailwater) in Bailanghe, Xinan, and Taihe Reservoir during the fertilization season, while higher values indicated domestic sewage input to waterbodies (e.g., Mishan, Gengjing, Donghai Reservoir). Our results suggested that the aquatic ecosystem in water-receiving area of SNWTP would be potentially affected by the inter-basin water diversion, and thus, ecosystem-based strategies were also presented accordingly.

Fuzzy synthetic evaluation and health risk assessment quantification of heavy metals in Zhangye agricultural soil from the perspective of sources

Heavy metals in agricultural soil receive much attention because they are easily absorbed by crop into the ecosystem. Managing the discharge of heavy metals from the source is an effective way to prevent and control heavy metals pollution. Grouped principal component analysis (GPCA) and Positive Matrix Factorization (PMF) receptor models were utilized in this study to conduct source apportionment, and the former was optimal because of the accuracy of predicting. Based on the source contribution by GPCA/APCS, heavy metals were evaluated by fuzzy synthetic evaluation model and health risk assessment model. The results of source apportionment showed that heavy metals in Zhangye agricultural soil were mainly affected by steel industry, traffic, agrochemicals, manures, mining activities, leather industry and metal processing industry source. Fuzzy synthetic evaluation showed that the pollution levels of Chromium (Cr) derived by leather industry and metal processing industry and Nickel (Ni) derived by steel industry and traffic source were higher. Health risk assessment revealed that the non-carcinogenic and carcinogenic risks of Cr derived by leather industry and metal processing industry and Lead (Pb) derived by steel industry and traffic source were higher.

Multivariate Analyses and Human Health Assessments of Heavy Metals for Surface Water Quality in the Xiangjiang River Basin, China

Pollution by heavy metals in river water is becoming a major subject of global drinking water concern, and the Xiangjiang River is one of the most heavily polluted rivers in China. Water samples were collected from 17 sites spanning the entire Xiangjiang watershed from 2005 to 2016 to investigate spatial-temporal distributions and potential human health risks related to 8 metal pollutants (As, Cd, Hg, Cr, Cu, Pb, Zn, and Se). The results of spatial-temporal distribution analyses proved that most metals were below the guideline limits the majority of the time. However, the hazard index and carcinogenic risk analyses indicated that As and Cr were associated with a potential risk of cancer, although noncarcinogenic heavy metals in general and carcinogenic risk declined year by year. A nonparametric seasonal Mann-Kendall's test revealed that there were notable decreasing trends in As, Cd, Zn, Cu, Cr, and Pb for most sites, whereas Se and Hg significantly increased in some areas over the targeted 12 yr. The results of principal component analysis agreed with those of dual hierarchical cluster analysis in the identification of pollution sources, the results of which are as follows: 1) As, Cd, Pb, Hg, and Zn were mainly derived from anthropogenic activities and the smelting industry; 2) Cr and Cu mainly originated from agricultural or industrial activities; and 3) Se was predominantly from natural erosion. The present study will be conducive to optimizing the distribution of water monitoring stations and drafting remediation strategies pertaining to the protection of public health in metal-polluted areas. Environ Toxicol Chem 2019;38:1645-1657. © 2019 SETAC.

Differences in the risk assessment of soil heavy metals between newly built and original parks in Jiaozuo, Henan Province, China

Differences in the concentrations of heavy metals between newly built and original parks remain incompletely understood. In this work, two newly built and four original parks in Jiaozuo, China, were taken as research objects. Using the geo-accumulation index, ecological risk assessment index and human health risk model, differences in heavy metal pollution between the two types of parks were determined. In the surveyed region, five heavy metals, namely, Zn, Cu, As, Ni and Co, polluted the environment. Serious As pollution was discovered, and respective As concentrations in the soils of newly built and original parks were 5.9 and 3 times the background value. The concentrations of Zn, Mn, As, Pb, Cr and Ni in newly built parks were higher than those in the four original parks, although the concentrations of Cu and Co between the two types of parks were not significantly different. The carcinogenic and non-carcinogenic risks of these metals in newly built parks (adults: 4.27E-05, 1.08; children: 2.53E-04, 8.94) were greater than those in original parks (adults: 2.57E-05, 0.67; children: 1.52E-04, 5.39), and newly built parks posed higher potential risk than original parks. Therefore, the concentration of heavy metals in soil must be assessed before former industrial sites are transformed into parks.

Soil physiochemical properties and landscape patterns control trace metal contamination at the urban-rural interface in southern China

This study examined the influences of three subsets of environmental factors (i.e. soil physicochemical properties including pH, organic matters and soil texture, landscape patterns, and parent materials) on the spatial variations and sources of soil trace metal contamination across an urban-rural environmental gradient in Guangzhou City, southern China. We collected 318 surface soil samples from forests, orchards, farmlands, and urban lawns using a random tessellation design for selecting sample sites. The geo-accumulation indices showed that 18%-88% of soil samples were contaminated: moderate to high contamination with Cd and Hg, low to moderate contamination with Cu, Pb, Zn and Ni, and low contamination with As and Cr. However, less than 13% of soil samples were considered to have exceeded the national standards causing environmental and human health concerns. The mean geo-accumulation indices increased in the order of forest, paddy field/orchard, vegetable, road/residential, and park/residential areas for As, Cd, Ni, Pb, Zn, closely following a land disturbance gradient. Spearman Correlation and Cluster Analyses showed that Pb-Cu-Zn had traffic-related origins, Cd-Hg were mainly influenced by fertilization or industrial emissions, and As-Cr-Ni had geogenic origins for agricultural soils. In contrast, the Ni, Hg and Cd contamination sources for urban soils included both anthropogenic and geogenic origins. The Stepwise Regression and Partial Redundancy Analyses showed that three subsets of environmental factors explained 43%-87% of variations of soil contamination for both agricultural and urban soils. We concluded that soil contamination was mainly controlled by soil physiochemical properties followed by landscape patterns. Soil absorption of aerial loads of trace metal pollutants dominated the soil contamination processes. Our findings implied that improving soil physiochemical properties and landscape designs can strengthen environmental buffering and carrying capacity, thus alleviating soil contamination and reducing non-point-source pollution in the study region.

Appraisal of heavy metal contents in groundwater and associated health hazards posed to human population of Ropar wetland, Punjab, India and its environs

Heavy metals are well recognised for their toxicity and pose human health risks even at very low levels. In the present work, groundwater from Ropar wetland, Punjab, India and its environs (18 sites), were analysed for physico-chemical parameters, water quality indices, heavy metal contents (cadmium, cobalt, chromium, copper, lead and zinc) and possible health risks posed to adults and children during summer and winter seasons. Groundwater was slightly-alkaline, non-saline and hard which may be suitable for irrigation purposes. Among 18 samples, 7 and 9 samples in summer; 8 and 18 samples in winter exceeded BIS acceptable limits (mg L^-1) of 0.003 and 0.05 for cadmium and chromium, respectively. Mean non-cancer hazard quotients for cobalt (5.09-7.63) were >1. Mean hazard indices for cumulative risks posed by all heavy metals (6.00-10.11) were also >1. These results indicated higher risk of non-cancerous health problems in residents of the study area. Chromium was found to pose significant possible cancer risk (1.20-2.99 cases/1000 persons). Children were more prone to health problems than adults due to their lower body weight with greater risk in winters, which may be attributed to higher contamination of heavy metals in groundwater after leaching during monsoons. The results of water quality analysis and risk assessment indicated that the groundwater suffered from significant contamination and if used for long-term without pre-treatment, may pose serious health risks to human population via drinking water and irrigation of agricultural fields due to bioconcentration of heavy metals in food crops cultivated in those fields.

Health risk assessment of heavy metals in soil samples from an abandoned industrial waste dumpsite in Ibadan, Nigeria

This study was carried out to determine the concentrations of heavy metals in the soil samples collected from an abandoned lead acid battery (LAB) industrial waste dumpsite in Ibadan, southwestern Nigeria. This was to assess the potential risks of the heavy metals on human due to exposure among local residents (children and adults) of the area. Forty (40) soil samples were collected over the entire dumpsite at 0-20 cm depth. The elemental concentrations of Pb, Cr, Cd, Zn, Cu, and Ni were measured using an atomic absorption spectrophotometer (AAS) technique. The contamination load was estimated by employing index of geoaccumulation (I_geo) and potential human health risks due to multiple exposure pathways (inhalation, dermal absorption, and ingestion) were estimated using the risk-based equations and exposure parameters developed by the United States Environmental Protection Agency (USEPA). The average concentrations (± standard deviation) of Pb, Cr, Cu, Mn, Cd, Ni, and Zn were 3.79 ± 2.16, 8.36 ± 3.90, 7.77 ± 2.70, 7.75 ± 3.10, 4.31 ± 0.82, 3.09 ± 2.29, and 3.07 ± 1.74 μg/g, respectively. The mean values of I_geo follow the order of Mn < Cr < Pb = Ni < Zn < Cu < Cd. The dermal contact with the heavy metals appeared to be the major route of exposure to children followed by inhalation and ingestion. Inhalation is the main route of exposure for the adults. The hazard quotients (HQ) of all the heavy metals are lower than 1, implying that the adverse health impact on the children and adult exposed to heavy metals from the dumpsite was relatively moderate. The hazard index (HI) values of Cd were 2.0 and 1.2 for exposed adults and children, respectively. The carcinogen risks for inhalation exposure ranged from 2.3 × 10^-6 to 6.4 × 10^-6, which falls within the acceptable limit of 10^-4 to 10^-6. There is concern over the potential health risk of the local residents, most especially the children living in the vicinity of the dumpsite due to the possibility of dispersal of heavy metals to the entire community, leading to long-life exposure and residents' detrimental health.

Characterization, Source and Risk of Pharmaceutically Active Compounds (PhACs) in the Snow Deposition Near Jiaozhou Bay, North China

The occurrence and distribution of 110 pharmaceutically active compounds (PhACs) were investigated in snow near Jiaozhou Bay (JZB), North China. All target substances were analyzed using solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry.A total of 38 compounds were detected for the first time in snow, including 23 antibiotics, eight hormones, three nonsteroidal anti-inflammatory drugs, two antipsychotics, one beta-adrenergic receptor and one hypoglycemic drug. The total concentration of PhACs in snow ranged from 52.80 ng/L to 1616.02 ng/L. The compounds found at the highest mean concentrations included tetracycline (125.81 ng/L), desacetylcefotaxime (17.73 ng/L), ronidazole (8.79 ng/L) and triamcinolone diacetate (2.84 ng/L). The contribution of PhACs in the vicinity of JZB to the PhACs in the snow is far greater than the contribution of those transmitted over a long distance. PhACs are mainly derived from drugs applied to local humans and animals. Based on the individual risk quotient (RQ) values, tetracycline poses high risks to the relevant aquatic organisms (algae and invertebrates). The rational application and scientific management of PhACs is an effective approach to reduce the ecological risks in JZB.

Concentrations and distribution of phthalate esters in the seamount area of the Tropical Western Pacific Ocean

A total of 14 phthalate esters (PAEs) were analysed by gas chromatography-mass spectrometry (GC-MS) to better understand its occurrence and distribution in seawater samples of M2 seamount in the Tropical Western Pacific Ocean (TWPO). The concentrations of ΣPAEs in the seawater ranged from 12.13 ng L^-1 to 60.69 ng L^-1 (av. 28.86 ng L^-1), dominated by dibutyl phthalate (DBP), di(2‑ethylhexyl) phthalate (DEHP) and diisobutyl phthalate (DiBP). ΣPAEs concentrations in the southwest of the seamount were lower than those in the northeast, with the minima appearing above the seamount summit. Current-seamount interaction was reckoned to be the principal driving factors in the distribution of PAEs. DEHP posed a medium risk in seawater, suggesting that marine plastic pollution has become an urgent environmental issue that calls for more attention and actions. Microplastics leaching and atmospheric deposition might be the potential sources of PAEs.

Mechanisms of radical-initiated methylmercury degradation in soil with coexisting Fe and Cu

Methylmercury (MeHg) is a toxic compound. It forms mainly in reducing environments, and then degrades through biogeochemical processes. Photodegradation and microorganism degradation of MeHg are among the processes that have been reported. However, little attention has been focused on the abiotic degradation of MeHg in soil/sediment without light. In our study, the percent MeHg of total Hg in Guangzhou soil in southern China was found to be variable and exhibited a significant negative correlation with the content of Fe or Cu where annite (KFe²⁺₃(AlSi₃O₁₀)(OH)₂), a Fe-bearing mineral, was identified. To understand the mechanisms of radical-initiated MeHg degradation by Fe/Cu-containing components, batch experiments were done. Results showed that annite in the soils could activate O₂ to generate OH and O₂^- and facilitate MeHg degradation under oxic conditions. Meanwhile, Cu components in the soil further enhanced the production of O₂^-, and was oxidized to Cu(III) promoting degradation of MeHg directly. These findings help us understand that the distribution of MeHg in soil depends on not only external pollution sources, but also on biogeochemical processes in subsurface environments.

An exploration of an integrated stochastic-fuzzy pollution assessment for heavy metals in urban topsoil based on metal enrichment and bioaccessibility

An integrated stochastic-fuzzy pollution assessment method (ISFPAM) for soil heavy metal was established based on geo-accumulation index (I_geo), stochastic-fuzzy theory and double weight system under synthetical consideration of metal ecotoxicity and bioaccessibility. The pollution characteristics of the topsoil heavy metals (Cu, Zn, Cd, Pb and Cr) in Xiangjiang New District were evaluated by the widely-used Single factor index (SF), Nemerow index (NI), I_geo, Potential ecological index (PERI), Risk assessment code (RAC) and the ISFPAM. The results of SF, NI, I_geo, RI and RAC of the studied metals revealed the following orders: Cd > Zn > Cr > Cu > Pb, Cd > Zn > Pb > Cr > Cu, Cd > Cr > Cu > Zn > Pb, Cd > Cu > Pb > Cr > Zn, and Cd > Pb > Cr > Zn > Cu, respectively. The different pollution assessment methods outputted the differentiated conclusions to some extent except the judgment for Cd. Results based on ISFPAM indicated that metal pollution degrees decreased in the order of Cd (5.91, Grade 6) > Cu (2.81, Grade 3) > Pb (2.66, Grade 3) > Cr (1.58, Grade 2) > Zn (0.69, Grade 1). By detailed comparison analysis, the double weight system and stochastic-fuzzy theory made ISFPAM better resolving ability to find out priority heavy metals and areas with relatively higher enrichment, ecotoxicity and bioaccessibility under efficient parameter uncertainty control. Cd, Cu and Pb were regarded as the priority control metals, especially Cd. Simultaneously, the reliabilities of heavy metal pollution corresponding to adjacent pollution grades were quite close in some sites, which recommend recheck for avoid misleading the decision-makers.