Pollution Status Of Heavy Metals Research Articles

Seasonal Variation Characteristics and Pollution Assessment of Heavy Metals in Water and Sediment of Taipu River

Taipu River is a river spanning two provinces and one city in a demonstration area in the Yangtze River Delta on an ecologically friendly developmentand an important water source in the upper reaches of the Huangpu River in Shanghai. To understand the multi-media distribution characteristics, pollution status, and ecological risk of heavy metals in the Taipu River, the contents of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, and Zn) in the sediments of Taipu River were analyzed, and the pollution status and potential ecological risk were evaluated using the Nemerow comprehensive pollution index, geo-accumulation index, and potential ecological risk index methods. In addition, the health risk assessment model was used to assess the health risk of heavy metals in surface water of Taipu River. The results showed that the concentrations of Cd, Cr, Mn, and Ni in the surface water of Taipu River exceeded the class Ⅲ water limit at the upstream point in spring; the concentrations of Sb exceeded the class Ⅲ water limit at all points in winter; the average value of As exceeded the class Ⅲ water limit in overlying water during the wet season; and the average values of As and Cd exceeded the class Ⅲ water limit in pore water during the wet season. The health risk assessment of surface water implied that both adults and children had higher health risk in spring and lower health risk in other seasons. The health risk of children was significantly higher than that of adults, and it mainly came from chemical carcinogenic heavy metal elements As, Cd, and Cr. The average contents of Co, Mn, Sb, and Zn in Taipu River sediments in the four seasons all exceeded the Shanghai soil baseline; the average contents of As, Cr, and Cu in summer, autumn, and winter exceeded the Shanghai soil baseline; and the average contents of Cd, Ni, and Pb in summer and winter exceeded the Shanghai soil baseline. The evaluation results of the Nemerow comprehensive pollution index and geo-accumulation index showed that the pollution degree of the middle reaches of Taipu River was higher than that of the upper and lower reaches, and the Sb pollution was more serious. The potential ecological risk index method revealed that the Taipu River sediment was at a low risk. Cd had a high contribution in both the wet and dry seasons and could be regarded as the main heavy metal of potential ecological risk in the Taipu River sediment.

Trophic transfer of heavy metals in a wetland food web from an abandoned e-waste recycling site in South China

In order to understand the pollution status and trophic transfer of heavy metals across wetland food web organisms, four invertebrate species, six fish species, one snake species, and one bird species were collected from an abandoned e-waste site in South China for analysis of toxic elements (Ni, Zn, Cu, Cr, Cd, and Pb). The concentrations of Ni, Zn, Cu, Cr, Cd, and Pb were 0.16–15.6, 24.9–850, 1.49–645, 0.11–64.6, 0.01–4.53 and 0.41–40.4 mg/kg dry weight, respectively. The results demonstrated that the concentrations of six studied heavy metals decreased throughout the whole food web, but Cu and Zn concentrations increased along the bird and reptile food chains, respectively. The trophic transfer of metals for the key species should be of special attention, as the trophic biomagnification factor (TMF) in a food web may overlook the ecological risks of metals for certain species, especially those at high trophic levels. The estimated daily intake (EDI) and the target hazard quotient (THQ) results showed that Cu, Cd, and Pb posed the main risks on human health, especially through the consumption of snail and crab species.

Levels of heavy metal in soil and vegetable and associated health risk in peri-urban areas across China

Peri-urban vegetable field plays an essential role in providing vegetables for local residents. Because of its particularity, it is affected by both industrial and agricultural activities which have led to the accumulations of heavy metal in soil. So far, information on heavy metal pollution status, spatial features, and human health risks in peri-urban vegetable areas across China is still scarce. To fill this gap, we systematically compiled soil and vegetable data collected from 123 articles published between 2010 and 2022 at a national level. The pollution status of heavy metals (i.e., cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn)) in peri-urban vegetable soils and vegetables were investigated. To evaluate the levels of heavy metal pollution in soil and human health risks, the geoaccumulation index (Igeo) and target hazard quotient (HQ) were calculated. The results showed that mean concentrations of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in peri-urban vegetable soils were 0.50, 0.53, 12.03, 41.97, 55.56, 37.69, 28.55, and 75.38 mg kg−1, respectively. The main pollutants in peri-urban vegetable soil were Cd and Hg, and 85.25% and 92.86% of the soil samples had Igeo > 1, respectively. The mean Igeo values of this regions followed the order of northwest > central > south > north > east > southwest > northeast for Cd and northeast > northwest > north > southwest > east > central > south for Hg. The mean Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn concentrations in vegetables were 0.30, 0.26, 0.37, 0.54, 1.17, 6.17, 1.96, and 18.56 mg kg−1, respectively. Approximately 87.01% (Cd), 71.43% (Hg), 20% (As), 65.15% (Pb), 27.08% (Cr) of the vegetable samples exceeded the safety requirement values. The vegetables grown in central, northwest, and northern China accumulated much more heavy metals than those grown in other regions. As the HQ values for adults, 53.25% (Cd), 71.43% (Hg), 84.00% (As), and 58.33% (Cr) of the sampled vegetables were higher than 1. For children, the HQ values were higher than 1 for 66.23% (Cd), 73.81% (Hg), 86.00% (As), and 87.50% (Cr) of the sampled vegetables. The findings of this study demonstrate that the situation of heavy metal pollution in peri-urban vegetable areas across China are not optimistic and residents who consume the vegetables are at high risk of health issues. To ensure soil quality and human health, strategies should be taken to guide vegetable production and remedy soil pollution in peri-urban areas with the rapidly urbanizing China.

Assessment of heavy metal pollution in Nigerian surface freshwaters and sediment: A meta-analysis using ecological and human health risk indices

Heavy metal pollution in surface freshwaters is prevalent globally and is an environmental issue of concern. Many studies have described sources, concentrations in selected waterbodies and toxic effects in biological systems. The purpose of the present study was to assess the status of heavy metal pollution in Nigerian surface freshwaters as well as the ecological and public health risks associated with current levels of pollution. A literature review of studies which assessed concentrations of heavy metals in named freshwater bodies around the country was done to gather relevant data. These waterbodies included rivers, lagoons, and creeks. The data gathered was subjected to a meta-analysis using referenced heavy metal pollution indices, sediment quality guidelines, ecological risk indices and non-carcinogenic and carcinogenic human health risk indices. The result obtained showed that concentrations of Cd, Cr, Mn, Ni and Pb in Nigerian surface freshwaters are higher than the maximum recommended levels in drinking water. The heavy metal pollution indices calculated using drinking water quality criteria by the World Health Organization and the US Environmental Protection Agency, were also significantly higher than the threshold value of 100 (13,672.74 and 1890.65 respectively). These results indicate that the surface waters are unsafe for drinking purposes. The enrichment factor, contamination factor and ecological risk factor indices for cadmium (684.62, 41.73 and 1251.90 respectively) were all higher than the maximum threshold for each index (40, 6, 320 respectively). These results indicate that cadmium contributes significantly to the ecological risk associated with pollution in Nigerian surface waters. In terms of public health risk, the current levels of heavy metal pollution in Nigerian surface waters pose both non-carcinogenic and carcinogenic risks to children and adults who are exposed through ingestion and dermal routes as shown by results from the present study. Nigeria is blessed with abundant surface freshwater resources and many coastal indigenous populations use the water resources for drinking and domestic purposes. Many of them are also commercial fish farmers earning their daily living from fisheries resources. Heavy metal pollution must be regulated to levels below which end users and aquatic life are protected from adverse impacts of pollution.

Evaluation of health risk and heavy metal pollution status in the Bhima River water Kalaburagi, Karnataka, India

The current investigation aimed to examine the present status of pollution in the Bhima River using indices (degree of contamination, heavy metal evaluation index, & heavy metal pollution index) and health risk assessment (non-carcinogenic & carcinogenic) by choosing some heavy metals like copper (Cu), chromium (Cr), manganese (Mn), cadmium (Cd), nickel (Ni), lead (Pb), & zinc (Zn). Eight samples of surface water were collected monthly from October 2021 to September 2022 and analyzed by an atomic absorption spectrometer. The absorptions of heavy metals into sequence Mn > Zn > Cu > Pb > Ni > Cr > Cd have been observed. Pb, Cd, and Ni concentrations were considerably higher in samples collected near sewage runoff and along bridges. The calculated pollution indices indicate that five of the eight sampling sites are extremely polluted. Carcinogenic & Non-carcinogenic dangers were tabulated for adults, children, & infants according to the quantity of heavy metal content in an average daily consumption of water. For adults, children, as well as infants, the estimated non-carcinogenic standards were 3, 5, and 2, respectively. The computed carcinogenic risk levels for Pb, Cd, and Ni exceed the 10-6-10-4 acceptable limit. Indices and risk assessment values suggest that river water is not acceptable for ingestion by all age groups. Additionally, principal component analysis and cluster analysis disclosed that agricultural runoff, lead battery usage, sewage sludge, and bridge construction were the foremost sources of water quality degradation in the study zone. The development of a public drinking water supply is advised by this research to lessen negative impacts of heavy metal poisoning upon human health. Before making the water available for use by the public, it needs also be treated.

Assessment of heavy metals pollution status of surface soil dusts at the Katima Mulilo urban motor park, Namibia

The aim of the study was to examine the pollution status of environmentally concerned heavy metals: lead, cadmium, chromium, arsenic, cobalt, nickel, copper, zinc, vanadium, and manganese in surface soil dusts at the Katima Mulilo urban motor park (KMUMP), Namibia. Composite surface soil dusts samples were randomly collected from three points at 10 m apart within the motor park, and a control site on a weekly basis over 8 weeks. Pooled sampled were homogenized and 20 sub-samples (<75 μm soil fraction) were taken from the large sieved sample and digested according to EPA method 3050B. The digestates were analyzed for concentrations of the heavy metals using ICP-OES (Perkin Elmer Optima 7000 DV). The results showed a wide range of heavy metals concentrations from 0.33 mg/kg Cd to 13.7 mg/kg Zn, and differed statistically between study locations (p < 0.05). The results were generally lower than their WHO’s maximum permissible concentrations in soils for the protection of ecosystem’s health. The ecological risk indexes of the heavy metals suggest that the surface soil dusts at KMUMP were not contaminated by the heavy metals at this point. However, this does not preclude exposure risks to travelers, especially vulnerable children due to heavy metals’ toxicity and bioaccumulation.

Heavy Metal Concentration and Pollution Status of Cross River in Afikpo Catchment Area, Ebonyi State, Nigeria

Heavy Metal Concentration and Pollution Status of Cross River in Afikpo Catchment Area, Ebonyi State, Nigeria

Spatial Distribution Characteristics and Source Analysis of Heavy Metals in Soil of a Lead Plant in Sanmenxia

At present, a large-scale relocation of industrial enterprises is taking place in major cities in China, and a large number of contaminated relocation sites are being generated, among which the heavy metal pollution is particularly serious. In order to analyze the pollution status, spatial distribution, and sources of heavy metals in the soil of a lead factory in Sanmenxia, the spatial variation and distribution characteristics of heavy metals in the soil were analyzed using geostatistics, and the main sources of heavy metals in the soil were analyzed using a PMF model. The results showed that the average values of As, Cd, Cu, Pb, Hg, and Ni in the soil far exceeded the background values of the soil environment in Henan province; the contents of As, Cd, Pb, and Hg exceeded the screening values of soil pollution risk; and the contents of As, Pb, and Hg exceeded the control values of soil pollution risk. The high-value area was located on the northern part of the slag yard; the Cr, Ni, and Cd high-value area was located in the north and south of the slag yard; the high-value As area was located in the slag yard between the southern area and the living quarters; the Cu and Pb high-value area was relatively scattered, mainly concentrated in the central part of the raw material storage area and furnace area; and Ni and Cd and Cu and Pb had the same spatial distribution characteristics. Based on the PMF model, it can be seen that there were three main sources of the seven heavy metals, and Cd was mainly from waste residue accumulation, with a contributing rate of 87.60%. Cu, Pb, and Hg were mainly soil parent material, with contribution rates of 92.50%, 75.20%, and 95.40%, respectively. Cr, Ni, and As were mainly raw material dust exhaust gas sources, with contribution rates of 80.80%, 83.30%, and 62.00%, respectively.

Accurate Prediction of Soil Heavy Metal Pollution Using an Improved Machine Learning Method: A Case Study in the Pearl River Delta, China.

In traditional soil heavy metal (HM) pollution assessment, spatial interpolation analysis is often carried out on the limited sampling points in the study area to get the overall status of heavy metal pollution. Unfortunately, in many machine learning spatial information enhancement algorithms, the additional spatial information introduced fails to reflect the hierarchical heterogeneity of the study area. Therefore, we designed hierarchical regionalization labels based on three interpolation techniques (inverse distance weight, ordinary kriging, and trend surface interpolation) as new spatial covariates for a machine learning (ML) model. It was demonstrated that regional spatial information improved the prediction performance of the model (R2 > 0.7). On the basis of the prediction results, the status of HM pollution in the Pearl River Delta (PRD) region was evaluated: cadmium (Cd) and copper (Cu) were the most serious pollutants in the PRD (the point overstandard rates are 18.77% and 12.95%, respectively). The analysis of index importance and bivariate local indicators of spatial association (LISA) shows that the key factors affecting the spatial distribution of heavy metals are geographical and climatic conditions [namely, altitude, humidity index, and normalized vegetation difference index (NDVI)] and some industrial activities (such as metal processing, printing and dyeing, and electronics industry). This study develops a novel approach to improve existing spatial interpolation techniques, which will enable more precise and scientific soil environmental management.

Heavy metal pollution and risk assessment of tailings in one low-grade copper sulfide mine

Analyzing the pollution level and ecological risk of heavy metals in tailings is a necessary step for conducting revegetation after a tailings pond’s closure. Herein, we determined the heavy metal pollution status and ecological risk in one low-grade copper sulfide tailings pond using chemical and mineralogical analysis, chemical extraction, and ecological risk assessment. The results showed that the low-grade copper sulfide tailings displayed a low pollution status and exhibited a very low ecological risk. Among six heavy metals (Cu, Pb, Zn, As, Cr, and Cd), only Cu (53.7 mg/kg) slightly exceeded its standard value limit (50 mg/kg), and was the main pollutant in the tailings. Due to its high toxicity, As had the maximum contribution to the potential ecological risk in the tailings. Pb, Zn, Cr, and Cd in the tailings were practically of no pollution, and at low or none potential ecological risk. In order to conduct revegetation in the tailings pond, more attention should be paid to the acidity change of tailings and its impact on the chemical activity and bioavailability of Cu and As. This research provides a theoretical basis for heavy metals risk control and revegetation in the low-grade copper sulfide tailings pond.

Health and ecological risks assessment of heavy metals and metalloids in surface sediments of Urmia Salt Lake, Northwest of Iran.

Urmia Lake, in the northwest of Iran, is the largest body of saline water in the Middle East, which has been desiccated in recent decades. To investigate the pollution status and ecological-health risks of heavy metals and metalloids in the surface sediments of this lake, 26 sediment samples were collected along the salt marshes of the lake and were analyzed for heavy metals and metalloid concentrations. The potential ecological risk assessment was carried out using enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), and potential ecological risk (Eri) standard indices. The average concentrations (mg kg-1) of heavy metals and metalloids were as follows: Fe (11,714) > Sr (320.8) > Mn (274.3) > V (28.5) > Cu (24.7) > Zn (21.2) > As (17.3) > Ni (14.8) > Cr (12.6) > Pb (11) > Co (4.0) > U (1.7), Hg (0.6) > Mo (0.36). The concentrations of As, Hg, and Sr in lake sediments were higher than geochemical background values. The non-carcinogenic risks caused by heavy metals and metalloids were insignificant regarding health risks. Levels of carcinogenic risk for metal(loid)s were in the acceptable ranges (10-6-10-4). The ecological risk was low, except for As, Sr, and Hg which showed moderate to significant EF, Igeo, and CF values. Arsenic and Sr were enriched in the surface sediments in desiccated parts of the lake due to complete lake water evaporation. It seems that further drying of the lake increases the potential ecological risk of heavy metals and metalloids in the surface sediments of Urmia Lake.

Spatial Distribution and Risk Assessment of Heavy Metals in Surface Sediments from the Middle and Upper Reaches of the Yangtze River

The hydrological regime of rivers significantly changes after dam impoundment, which in turn affects the particle composition and heavy metal fractions of the river sediments. From June to July 2019, the sediments from 26 sampling sections were collected along the main stream of the Yangtze River from Panzhihua City in the upper reaches of the Yangtze River to Hukou City in the middle reaches of the Yangtze River. The concentrations and fractions of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn were measured using the BCR three-step extraction procedure. The pollution status and potential ecological risk of heavy metals in sediments were evaluated using the geo-accumulation index, the sediment quality guideline, and the risk assessment coding method (RAC). The results showed that the average particle size of sediments in the upper reaches of the Yangtze River (Jinsha River cascade reservoir section and the Three Gorges reservoir section) decreased from upstream to downstream, the total concentrations of As and Zn increased, and the variation trend in the middle reaches was not obvious. The content of clay particles was significantly positively correlated with the acid-soluble fraction concentrations of Cd and Ni. Cd was mainly in the residual fraction (59.26%) and acid-soluble fraction (24.67%). Large parts of Cr and Ni were residual fractions accounting for 92.41% and 83.41%, respectively. As, Co, Cu, Pb, and Zn were mainly in the residual fraction and the reducible fraction. The order of decrease for the pollution degree (Igeo) of As, Cd, Co, Cr, Ni, and Zn was the Jinsha River, the middle reaches of the Yangtze River, and the Three Gorges Reservoir. The decrease order of bioavailability (RAC) of Cd, Co, Cr, Cu, Ni, and Zn was the Three Gorges Reservoir, the Jinsha River, and the middle reaches of the Yangtze River. The bioavailability of As and Pb decreased in the order of the middle reaches of the Yangtze River, the Three Gorges, and the Jinsha River. According to the classification of the RAC, Cd in the Three Gorges Reservoir area exhibited a high risk with the RAC accounting for 48.44%. Cu, Ni, and Zn showed a low or medium risk.

Contamination And Health Risk Assessment Of Heavy Metals Form A Typical Pb-zn Smelter In Northwest China

Soil contamination by heavy metals due to metal smelting activities poses a serious threat to the ecological environment and to human health, as it is considered to be one of the most significant sources of soil pollution. The objective of this study was to analyze the pollution status and human health risks of heavy metals emitted from metal smelting activities of a Pb-Zn smelter. The results of mean values of Zn, Pb, Cd, Cr, Cu and Mn should be incorporated and mention the status in respect to background value. Contamination levels of heavy metals were evaluated using the potential ecological risk index (RI). Possible human health risks were assessed using the health risk assessment model developed by the US EPA. The results showed that the soils are seriously polluted, and migrated down the soil vertical profile. The index of RI indicated a very high potential ecological risk overall in the entire study area, especially for Cd. The health risk analysis showed that adults and children are exposed to significant non-carcinogenic health risks, and there are higher non-carcinogenic health risks for children than for adults. Additionally, the carcinogenic risks of Cr were higher than those of Cd for the two population groups, and children were more susceptible than adults. These results are useful for management, prevention, control and remediation of heavy-metal contamination. Meanwhile, this research provides methods, experiences, and reference to other study of similar heavy-metal soil pollution. Bangladesh J. Bot. 51(4): 995-1015, 2022 (December) Special

Mangrove (Avicennia marina) parts as proxies in marine pollution of Nizampatnam Bay, East Coast of India: An integrated approach

This study focuses on the assessment of heavy metals (HM) concentration and pollution status of the Nizampatnam Bay, east coast of India, from mangrove plant parts (roots and leaves) and sediment samples. This is the first of its kind work (comparison of data from both mangrove and sediment samples) from the third largest mangrove ecosystem in India. To carry out this work, plant (Avicennia mariana) and sediment samples were collected from five stations. The collected samples were carefully subjected to the laboratory methods and heavy metal concentrations were determined by using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The obtained results were juxtaposed with the optimal values of world surface pollution rock averages, and noticed heavy metals such as Cd and Cu exceed the optimal values. To know the contamination levels and the chemical elements that contribute to the pollution, various environmental indices, viz., contamination factor, enrichment factor, geoaccumulation index, and pollution load index were, carried out on the sediment sample data. To ascertain the mangrove plant's capacity (in the study area) for accumulation and translocation of heavy metals in different parts of the plants, factors such as bio-concentration and translocation were calibrated.

Pollution status and risk assessment of heavy metals in the sediment of a historically contaminated lake treated by oxidation pond in China.

Sediment plays animportant role in controlling biogeochemical cycling of heavy metals in aquatic environment. The Ya-Er Lake is a typical lake which was historically contaminated by heavy metals in Hubei province, China. After industries surrounding the Ya-Er Lake being shut down, oxidation pond treatment and dredging program were conducted for pollution management since 1970s. To date, the Ya-Er Lake has been used for aquaculture for several decades. However, the status of heavy metal levels and ecological risks in this lake remains unclear. Herein, concentrations, chemical fractions, and risk assessment of heavy metals were investigated in the Ya-Er Lake sediment. Results showed that concentrations of heavy metals in the Ya-Er Lake sediment were higher than other reported lake systems, suggesting that heavy metal pollution in the Ya-Er Lake is still serious. Relatively higher proportions of carbonates bound form of Cd and Ni indicated high-risk potential of these two heavy metals, and Cd and Ni should be listed as the primary heavy metal pollutants in the Ya-Er Lake according to the results of potential ecological risk index (PERI) and sediment quality guidelines (SQGs). The risk assessment code (RAC) analysis showed that Ni and Cd poses higher bioavailability and mitigation potential, and may affect the Ya-Er Lake ecosystem and downstream aquatic environment. These findings reflected that oxidation pond treatment and dredging sediment to near place are not effective to control heavy metal pollution, and a long-term ecological risk is still posed to surrounding aquatic environment. Our study provides scientific basis on pollution control and management in aquatic system contaminated by heavy metals.

Pollution Status of Sediment from a Remediated Crude Oil Produced Water Discharge Channel Using Various Indices

The Forcados Terminal effluent discharged channel was remediated about twenty years ago with recommendation for periodic assessment of the organic and inorganic contaminants in the area. Forcados Terminal is in Delta State, Nigeria. This study was carried out to evaluate heavy metals pollution status of sediments in the remediated crude oil effluent discharge channel. A total of sixteen sediments samples were collected from ten sampling locations using grab sampling technique in October 2019 (wet season) and February 2020 (dry season). Heavy metals were determined in all the samples using atomic absorption spectrophotometry after digestion with aqua regia. The results showed that the concentrations of the sediment samples (mg/kg) ranged from <0.01-0.05, <0.01-0.91, <0.01-3.46, 13.2-45.3, 14.7-64.1, 5.56-105, 3.10-108, 0.14-5.86, 78.8-289, 28.2-254 and 3529-7773 for Hg, As, Cd, Pb, Cr, Ni, Cu, V, Mn, Zn and Fe. Hg and As were generally not detected in the sediments. On the average, the geoaccumulation index of Cd in the sediments falls into the moderately polluted category while the geoaccumulation index of all the other metals falls into the practically unpolluted category. On the average, the Contamination/Pollution index (CPI) value of Cd was > 1 which indicates that the sediments were polluted with Cd but the CPI values of other heavy metals were < 1 which indicates that these sediments were contaminated with the other heavy metals.

Risk Assessment and Sources of Heavy Metals in Farmland Soils of Yellow River Irrigation Area of Ningxia

The farmland environment is directly related to the quality and safety of agricultural products. In order to understand the characteristics and main influencing factors of heavy metals in farmland soil in the Yellow River irrigation area of Ningxia, sampling and monitoring were conducted for five consecutive years from 2017 to 2021, and the distribution characteristics and correlation of heavy metals were analyzed. The pollution status and potential ecological risks of heavy metals were evaluated, and the main sources of heavy metals in farmland were analyzed. The results showed that the average values of Pb, As, Zn, Ni, Cu, Hg, Cr, and Cd in the soil of the Ningxia Yellow River irrigation area were 19.74, 11.67, 66.88, 29.09, 22.55, 0.03, 62.27, and 0.19 mg·kg-1, respectively, which were enriched to some extent compared with the background values of the soil environment in Ningxia. Among them, Hg and Cd had middle- and high-grade ecological risk points; however, none of them exceeded the control value of agricultural land soil pollution risk, and all sampling sites had no high-risk or extremely high-risk levels. The results of source analysis based on positive matrix factorization (PMF) and correlation analysis showed that there were five main sources of heavy metals in farmland soil in the study area: natural sources, mixed sources of industrial and mining activities and the production and life of residents, transportation sources, agricultural production activities sources, and industrial sources, with contribution rates of 26.54%, 25.59%, 22.52%, 15.63%, and 9.72%, respectively. On the whole, the heavy metals in farmland soil in the Ningxia Yellow River irrigation area did not exceed the standard, and there was no high-level ecological risk. The production environment of the farmland soil was good, but the contribution rate of human activities to soil heavy metals was large.

Variation in pollution status, sources, and risks of soil heavy metals in regions with different levels of urbanization

Soil heavy metal (HM) pollution is an increasing threat to ecosystem integrity and human health with rapid urbanization. Nevertheless, how soil HMs vary with the process of urbanization remains unclear. Here we used index evaluation, spatial analysis, and a positive matrix factorization (PMF) model to determine the pollution characteristics and sources of eight soil HMs (Mn, Cr, Cu, Zn, As, Cd, Pb, and Ni) among regions with different urbanization levels (urban area, suburb, and ecoregion) in Baoding City, Northern China. We also assessed the risks posed to the ecosystem and human health using risk assessment models. The results indicated that the mean levels of Cu, Zn, As, Cd, and Pb in the study area exceeded the soil environmental quality standards by 10.7 %, 10.7 %, 12.5 %, 23.2 %, and 3.57 %, respectively. A pronounced regional spatial distribution was discovered with high levels in suburban areas. Both the geo-accumulation index and potential ecological risk index revealed significantly higher HM contamination in suburban areas than in urban or ecoregion areas. Source apportionment based on the PMF model and correlation analysis showed that soil HMs in suburban areas primarily originated from agricultural activity, industrial sources, and natural sources. Those in urban soils originated from industrial sources, urban traffic, and natural sources, whereas those in ecoregions derived from natural sources and agricultural activity. The complex sources of soil HMs in suburban areas resulted in the highest carcinogenic risks to children health, followed by the ecoregion, but not in urban areas. This study identified the differences in pollution levels, sources, and risks of soil HMs among regions with different urbanization levels and can guide future efforts to mitigate and manage soil HM pollution during urbanization.

Spatial Risk Assessment and Source Identification of Heavy Metals in Riverine Sediments of Lake Chaohu Basin, China

In recent decades, the rivers in Lake Chaohu Basin have been subjected to intensive anthropogenic disturbance. However, previous studies have mainly focused on Lake Chaohu, and the inflowing and outflowing rivers have not been well examined. To characterize the pollution status of heavy metals in the entire Lake Chaohu Basin, 8 heavy metals (Cu, Zn, Pb, Cr, Cd, As, Hg, and Ni) in riverine surface sediments were measured at 131 sampling sites in 7 subbasins. Spatial patterns and pollution characteristics were evaluated based on the potential ecological risk, geoaccumulation, and pollution load indexes. The results showed that Cr and Hg were the 2 main heavy metal pollutants in the surface sediments, with mean contents exceeding background values by a factor of 4.12 and 2.64, respectively. The Nanfei River (NF), which flows through Hefei city (a metropolis of the capital of Anhui Province), is characterized by large amounts of domestic and industrial waste discharged into the water body due to human activities; this waste caused serious heavy metal pollution, and NF substantially contributed to heavy metal pollution inputs to Lake Chaohu. Several subbasins in the southern part of Lake Chaohu Basin exhibited high concentrations of Cu in surface sediments, mainly from mining and agriculture. This study identified the main contamination areas, revealed the possible sources of each heavy metal, and can serve as a reference for the remediation and management of Lake Chaohu Basin to ensure the water safety of Lake Chaohu.

Health risk assessment of heavy metal exposure through vegetable consumption around a phosphorus chemical plant in the Kaiyang karst area, southwestern China.

The phosphorus chemical industry is an important source of heavy metals in farmland. Vegetables grown on contaminated soil potentially impose adverse effects on human health. In this study, the pollution status and health risks of heavy metals in vegetables around a phosphorus chemical plant in Kaiyang County, Guizhou Province, southwestern China, were assessed, and the low-accumulation vegetables were screened by bioaccumulation factor (BAF) and cluster analysis. Results showed the average concentrations of Hg, As, Cd, Pb, Cr, Mn, Co, and Zn in vegetables were 0.015, 0.728 0.382, 0.227, 0.850, 27.227, 0.525, and 6.438mg/kg, respectively. The single-factor pollution index showed that Cd was moderately polluted, and Cr, Hg, As, and Pb were slightly polluted. The Nemerow pollution index showed that the overall heavy metal pollution was classified as moderately polluted. The accumulation of heavy metals in different vegetables varied greatly, and chard, crown daisy, chayote, pumpkin, eggplant, white radish, sweet potato, carrot, and potato were selected as the low-accumulator vegetables. The consumption of all vegetables except chayote poses both carcinogenic and noncarcinogenic risks; among them, the consumption of sweet potato leaves has the highest health risks. The local population needs to adjust plantation structure and change dietary habits, and government should strengthen the management of phosphorus chemical plant pollution.