High Potential Ecological Risk Research Articles

Polychlorinated biphenyls (PCBs) in sediments and fish from dredged tributaries and creeks of river Ethiope, South-South, Nigeria: sources, risk assessment and bioaccumulation

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are ubiquitous in nature. In this study, the levels of PCBs were evaluated in sediments and fish samples obtained from dredged tributaries and creeks of River Ethiope. The work also assessed the possible relationship between the parameters and risks posed by polychlorinated biphenyls via several pollution indices. The mean concentrations of \sum PCBs on the sediments spanned from 645 – 3,977 µg/kg (wet season) to 252 – 1,219 µg/kg (dry season) dry weight. The concentrations of PCBs in fishes were 1,688 µg/kg (wet season) and 557 µg/kg (dry season). Higher bioaccumulation factors were observed with lower molecular weight PCBs than the higher ones (9 – Hexa – PCB, 8- Tetra- PCB). The results of the ecological risk (160 \leq Eri < 320), and human health risk (\geq 10-4 to 10-3-\leq 10-6), showed moderately to very high contamination and also moderately to very high cancer risk for children and adults. The strong positive correlation between PCB-114 and PCB-77, PCB-81, PCB-105 (r2 = 1.00, 0.99 & 1.00, p < 0.01) and the risks assessment values which ranged from 6.10 × 10-3 to 1.47 × 10-2 for children and 6.30 × 10-4 to 1.11 × 10-3 for adults (wet season), 1.04 × 10-3 to 2.99 × 10-2 for children and 7.80 × 10-5 to 5.61 × 10-1 for adults (dry season), showed rarely to adversely high potential ecological risk, biological effect and human health risk across the environment. The data show that higher levels of PCBs were observed in sediments and fish samples when compared with available standards. Considering the ILCR, hazard index, toxic equivalent, the sediments and fish obtained from these sites would be considered risky for humans. Dredging activities are majorly responsible for the high levels of PCBs across the sites. These have contributed significantly to the environmental status of the studied area.

Characterization of Metal Elements in Atmospheric PM2.5 and Health Risk Assessment in Heze in Winter from 2017 to 2018

Atmospheric PM2.5 samples were collected in Heze, Shandong Province, from a total of three sampling sites at Heze College, Huarun Pharmacy, and a wastewater treatment plant between October 15, 2017 and January 31, 2018, to determine the concentrations of 21 metal elements in PM2.5 using inductively coupled plasma mass spectrometry (ICP-MS). The degree of elemental enrichment was also discussed, the health risks and potential heavy metal ecological risks were assessed. The results showed that ρ (PM2.5) ranged from 26.7 to 284.1 μg·m-3 at the three sampling sites during the sampling period, and the concentration values did not differ significantly, all of which were at high pollution levels. The highest concentrations of K were found in the three sampling sites, accounting for 31.03%, 39.47%, and 38.43% of the total, respectively, mainly due to the high contribution of biomass burning in autumn and winter in Heze, a large agricultural city. The highest concentrations of Zn, 89.70, 84.21, and 67.68 ng·m-3, were found in the trace elements at the three sampling sites, respectively. The enrichment factor results showed that the enrichment factor values of Zn, Pb, Sn, Sb, Cd, and Se were higher than 100, among which the enrichment factors of Cd and Se were higher than 2 000 and 4 000, respectively, which were significantly influenced by anthropogenic activities and might have been related to industrial production, metal smelting, road sources, and coal combustion emissions. The health risk results showed that there was some potential non-carcinogenic risk (HQ>0.1 for children and adults) for As and a combined potential non-carcinogenic risk (HI>0.1) and some potential carcinogenic risk (CRT>1×10-6) for both children and adults at the three sampling sites. There was a more significant carcinogenic risk (CRT>1×10-4) for adults at the wastewater treatment plant, and the slightly higher carcinogenic risk for adults than that for children may have been related to the longer outdoor activity and higher PM2.5 exposure for adults. The elements with the highest potential ecological risk values were Cd, As, and Pb, with Cd exhibiting a very high potential ecological risk that should be taken seriously. All three sampling sites showed a very high combined potential ecological risk, with the intensity spatially expressed as Heze College>Huarun Pharmacy>wastewater treatment plant.

Potential Ecological Risk Assessment of Soil Heavy Metals in Fengdong New District Based on Information Diffution Model

The large-scale construction of new districts has led to severe soil heavy metal pollution. Therefore, taking Fengdong New District as the target research area, the descriptive statistics of heavy metal content characteristics and Kriging interpolation analysis have been conducted, and the potential ecological risk index and information diffusion theory were further combined to create an information diffusion model based on risk assessment. Finally, the pollution degree, ecological risk, and risk occurrence probability of Pb, Cu, Cd, and Hg were discussed. The findings revealed that the average concentrations of the four heavy metals far exceeded the background value of soil heavy metals by a factor of 1.943 (Pb), 1.419 (Cu), 3.074 (Cd), and 3.567 (Hg), respectively. Moreover, the distribution of soil heavy metals showed strong variability(CV>65%)owing to human interference. The distribution of Pb and Cu pollution were predominantly influenced by industrial production and land development for construction purposes, whereas industrial activities, agricultural practices, and transportation served as the primary sources of Cd contamination. On the other hand, industrial construction emerged as the major factor contributing to Hg pollution. The average values of individual potential ecological risk index for heavy metals of 9.716 (Pb), 7.095 (Cu), 92.292 (Cd), and 142.469 (Hg), coupled with the regional comprehensive potential ecological risk index (RI) average of 251.573, signified that the region was overall characterized by a relatively high potential ecological risk status. The overall potential ecological risk for Pb and Cu in the region were mild, whereas Cd and Hg posed moderate to high risks, indicating that Cd and Hg were the dominant driving factors behind regional heavy metal pollution. The evaluation results of the information diffusion model based on the potential ecological risk indicated that the probability ranking of different levels of comprehensive potential ecological risk was as follows:slightly high (38.98%) > moderate (38.55%) > high (5.89%) > slight (5.15%) > extremely high (3.56%). The exceeding probabilities of potential ecological risk levels for Cd and Hg were significantly higher than those for Pb and Cu. The exceeding probability of different pollution levels of Hg were slight (94.89%), moderate (66.85%), slightly high (23.62%), high (3.9%), and extremely high (2%), of which only the surpassing probability of the slight level was lower than that of Cd. The prediction error of pollution probability of each potential ecological risk level was less than 5%, demonstrating the reliability of the information diffusion model based on the risk assessment. This research will provide technical reference and support for the monitoring and management of potential ecological risks from soil heavy metals in limited sample data regions.

Multi-media distribution and risk assessment of per- and polyfluoroalkyl substances in the Huai River Basin, China

The widespread existence, environmental persistence, and risks of per- and polyfluoroalkyl substances (PFASs) have attracted widespread attention. Herein, the distribution and risk assessment of PFASs were investigated from the Huai River Basin. The ranges in different media were 29.83–217.96 (average of 75.82 ± 35.64 ng/L) in water, 0.17–9.55 ng/g (2.56 ± 2.83 ng/g) in sediments, and 0.21–9.76 ng/g (3.43 ± 3.07 ng/g) in biota. Perfluoropentanoic acid (PFPeA) was the most prevalent PFAS in surface water, followed by perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA), accounted for 42.62 %, 22.23 % and 17.72 % of the total concentrations of the PFASs analyzed, respectively. PFBA was dominant in sediments, accounting for 60.37 % of the total concentrations of the PFASs analyzed. Perfluorooctane sulfonate (PFOS) was the main pollutant in biota, and the highest concentration (5.09 ng/g) was found in Channa argus. Considering the measured concentrations in water, sediments and biota, the sediment-water partition coefficients (log Kd) and bioaccumulation factors (BAF) of PFASs were determined. The log Kd of the PFASs differed among those with a different carbon chain length, C7-C11 PFASs were more likely to be adsorbed onto sediments as the carbon chain length increases, and PFUnDA and PFDA showed the higher BAF value in Channa argus. PFASs in the Huai River Basin posed an acceptable ecological risk, and long-chain PFAS contamination provided green algae with a higher potential ecological risk. Compared to drinking water, aquatic products constituted a higher PFASs threat to human health, especially for children. The highest HQ was found in PFOS, with an HQmax of 0.97–4.32. Residents in the Huai River Basin should reduce their intake of Channa argus, Coilia nasus, and Carassius auratus, children aged 2 to 4 are limited to consuming no more than 6.9 g/d, 9.7 g/d, and 16.6 g/d, respectively.

Spatial-temporal evolution of ecological risks in a typical urban lake in Southwestern China

During urbanization, excessive development and utilization pose varying risks and challenges to the ecosystems of many urban lakes. Sediments are invaluable archives of past ecosystem changes. By analyzing variations in 210Pb and other geochemical indicators in sediment cores, it is possible to assess how susceptible lakes are to the impacts of climate change and human-induced pollution, which is crucial for urban planning and the management of lake environments. This study investigated the status of heavy metal pollution in Lake Longquan, Chengdu City, and reconstructed the historical evolution of its ecological environment using 210Pb dating. Three main conclusions are drawn. (1) Currently, Cd, Cu, Pb, Zn, Cr, and organic matter in the surface sediments of Lake Longquan are highly enriched in the southeastern, central, and northeastern regions. Cd levels even reach 1.54 mg/kg in the southeastern part of the lake near the town. The high overlap of heavy metal distribution with historical aquaculture areas and some tourist areas indicates that aquaculture and tourism are important sources of heavy metals that increase their bioavailability. (2) Lake Longquan is currently at a high potential ecological risk level, and the high potential risk level of Cd may cause ecological safety problems. The biological toxicity of As should be considered, too. (3) The risk evolution in Lake Longquan can be divided into six stages: (i) Before 1977, the ancient river. With the destruction of forest vegetation and the intensification of rock weathering, ecological risks increased. (ii) 1977–1989, construction and development. Due to human factors and the joint influence of heavy precipitation events, ecological risks increased; and (iii) 1989–2010, development prioritized protection. Due to the ineffective implementation of protection policies, aquaculture increases risks. (iv) 2010–2017, development. As a provincial resort and tourism area, the significant increase in human activities has led to constantly rising sedimentation rates and heavy metal concentrations, resulting in an ecological risk peak. (v) 2017–2020, protection. The efficient implementation of lake protection and restoration policies proved to be effective, and the ecological risk started to decrease. (vi) After 2020, protective development. The government's plan to reduce fertilizer usage and increase forest cover will help control ecological risks. It is necessary to continue controlling tourism and aquaculture activities, and transitional areas should be established around lakes for city residents to engage in lakeside sightseeing and recreational sports. This study provides valuable references for controlling and preventing heavy metal pollution in urban lakes.

Microplastics contamination in two species of gobies and their estuarine habitat of Indian Sundarbans

Sundarbans, a Ramsar site of India is contaminated with heterogeneous microplastic wastes. Boddart's goggle eye mudskipper and Rubicundus eelgoby, were common gobies of Sundarbans estuary which accumulated microplastics during their normal biological activities. We estimated the abundance of microplastics in water, sediment; skin, gills, bucco-opercular cavity and gastrointestinal tract of these two goby fishes. Microplastic load estimated in gobies were 0.84 and 2.62 particles per fish species with a dominance of transparent, fibrous microplastics with 100–300 μm in length. ATR-FTIR and Raman spectroscopy revealed polyethylene as prevalent polymer. Surface degradations and adsorption of contaminants on microplastic surface were investigated by SEM-EDX analysis. Presence of hazardous polymers influenced high polymer hazard index and potential ecological risk index which indicated acute environmental threat to Sundarbans estuary and its resident organisms. Current study will provide a new information base on the abundance of microplastics and its ecological hazard in this biosphere reserve.

Microplastic pollution in urban rivers within China's Danxia landforms: Spatial distribution characteristics, migration, and risk assessment

The potential deleterious effects of microplastics on environmental integrity and human health have elicited global attention. Particularly vulnerable to microplastics are Danxia landforms, characterized by their unique topographical features and ecologically fragile milieu. Notwithstanding, empirical studies assessing the prevalence of microplastics in these unique landforms remain strikingly limited. The present investigation comprehensively examined the abundance of microplastics in surface water, sediment, and groundwater across six cities and six counties within the Danxia landforms. Comparative analysis revealed a moderate level of microplastic contamination in the urban rivers of the Danxia region relative to other freshwater rivers. Anthropogenic activities, notably urban wastewater treatment and tourism, emerged as principal contributors to microplastic pollution. Sedimentary microplastics exhibited an accumulative trend from upstream to downstream locations. The risk assessment revealed a high potential ecological risk in counties and a moderate risk in cities. Cluster analysis suggested that groundwater microplastics were a confluence of hydraulic interactions between surface and subsurface waters within the Danxia region. This investigation elucidates the microplastic contamination profile, origins, migratory patterns, and associated risks in Danxia's urban rivers, thereby furnishing scientific underpinning for health and ecological preservation strategies within urbanized Danxia landscapes.

Physicochemical properties and heavy metals distribution of waste fine particles and soil around urban and peri-urban dumpsites

In developing countries like Ghana, the use of open dumpsites and landfills without proper waste management technique has resulted in environmental pollution with long-term adverse effects on soil, groundwater, human health and environmental sustainability. This study assessed the contaminants in fine particles of dumpsite waste and soil around urban and peri‑urban dumpsites at different depths of excavation and different age of deposited waste. Specifically, the study: (i) assessed physiochemical properties of fine particles of dumpsite waste and the surrounding soil, (ii) assessed heavy metals distribution from waste fine particles and surrounding soil at different depths and different ages of deposition, (iii) also determined soil quality indices (pollution index, geo-accumulation, and the potential ecological risk), and the hazards associated with the dumpsites on the residents living near the dumpsites. About 50 kg of waste was taken from surface, 0.5, 1.0 and 1.5 m depths. The samples were dried, segregated and sieved to obtain fine particles. Again, 1 kg soil was excavated form 0.5, 1.0 and 1.5 m depths at different age zones around each dumpsite. The fine particles and soil were analysed for physiochemical parameters using standard methods, and heavy metals using microwave plasma spectroscopy. The results showed that, the concentrations (electrical conductivity, potassium, cadmium, iron, copper and zinc) of waste fine particles and soil samples observed statistically significant different between them (p < 0.05). Waste particles recorded high cadmium and iron concentrations (41.7 mg/kg) and (4355 mg/kg) respectively at urban dumpsite. Similarly, there is statistically significant difference between calcium concentrations (p = 0.0221), potassium concentrations (p = 0.0227) and cadmium concentrations (p = 0.019) in the three age zones of urban dumpsite. The fine particles were heavily polluted with cadmium (PI > 6). High potential ecological risk of Hg (RI = 514.29), and (RI = 571.43) was observed at (SMZC1) and (NZA1) respectively; and high potential ecological risk of Cd (1000 ≤ RI ≤ 320), at (SMZA1-SMCA4. The study shows that both dumpsites have caused environmental hazards and this can cause surface and groundwater pollution and adverse effect on public health. But the study could not assess the impacts of dumpsite on leachate and water quality. The findings can be used as benchmark for developing appropriate technology for dumpsite mining, reclamation or decommission project; and exploit valorization potentials of the fine particles of the waste as composite and construction materials.

Spatial Distribution, Speciation, and Ecological Risk Assessment of Heavy Metals in Surface Sediments of Dongjiang Lake, Hunan Province

To understand the heavy metal pollution status of Dongjiang Lake, the contents and species of heavy metals in the surface sediments were investigated during September 2021, and the heavy metal pollution level and potential ecological risk were evaluated. The results showed that Cd, Pb, As, Cu, Zn, Ni, and Cr contents were in the range of 0.40-34.1, 14.8-1688, 6.99-1155, 6.89-280, 26.2-1739, 6.29-55.4, and 23.3-44.8 mg·kg-1, respectively, with extremely uneven spatial distributions. The highest contents of Cd, Pb, As, Zn, Cu, and Ni were found in the site adjacent to Yaogangxian tungsten ore. The proportion of metal species with bioavailability was high, in which Cd in acid-soluble species was 46.7%-71.5% and Pb in reducible species was 46.8%-67.0%. The bioavailable species of Cu, Zn, Ni, and Cr were 35%-68%, 42%-72%, 26%-51%, and 6%-30%, respectively, although they primarily existed in residual species. According to the geo-accumulation index (Igeo), there was a moderate or extreme pollution status of Cd in all sites, moderate or extreme pollution status of Pb in 90% of sites, and moderate pollution status of As, Cu, and Zn in 30% of sites. The ecological risk factor (Eri) of Cd showed high potential ecological risk in all sites with significantly high potential ecological risk in 80% of sites. Moreover, As and Pb had significantly high potential ecological risk, and Cu had moderate potential ecological risk in S7, which was adjacent to Yaogangxian tungsten ore. There was a high total potential ecological risk in all sites and significantly high potential ecological risk in 50% of sites. Therefore, the surface sediments of Dongjiang Lake were under the combined pollution of Cd, Pb, As, Zn, and Cu with high bioavailability and high total potential ecological risk.

EVALUATION OF THE EFFECTS OF HEAVY METALS ON WATER FROM ILLEGAL CRUDE OIL REFINERIES: A CASE STUDY OF THREE SELECTED COMMUNITIES IN THE NIGER DELTA REGION, NIGERIA

In order to assess the levels of heavy metals and health concerns associated with the operations of illicit refineries in water, 15 surface water samples were taken from Okerenkoko, Peterou-Gbene, and Bille in the Niger Delta region of Nigeria. A number of heavy metal indices, including the Contamination Factor (Cf), Pollution Load Index (PLI), Modified Degree of Contamination (mCd), Ecological Risk Factor (Erf), and Geo Accumulation Index (Igeo), were successfully applied in the evaluation of heavy metal contamination in surface water using World Health Organization WHO (2011) and Nigerian Standard for Water Quality NSDWQ (2007) standards. Additional research from WHO and NSDWQ comparisons revealed that the majority of the investigated heavy metals were higher than permissble limits in comparison to the control site. Although the concentration of heavy metals in the aquatic habitats varies amongst the various communities in the area, according to the CV. Additionally, CV contends that there is a connection between the illicit refiners’ actions at the study site and the water chemistry changes that result in surface water contamination. According to data from the WHO and the NSDWQ, the majority of heavy metal concentration readings in the study sites exceeded the acceptable limits when compared to those in the control site. According to the results of heavy metals indices such as Cf and PLI, the surface water in the analyzed site ranges from very slightly contaminated to extremely contaminated. However, Erf and Igeo findings showed that human activities through illegal refiners increase heavy metal concentration, which results in a very high potential ecological risk associated with surface water. Additional mCd results demonstrated that in the studied sites, the surface water has a high degree of contamination. The findings suggest that surface water assessment is required to warn against a decline in water quality in the area.

Accumulation Pattern and Risk Assessment of Potentially Toxic Elements in Permafrost-Affected Agricultural Soils in Northeast China.

The accumulation of potentially toxic elements (PTEs) in agricultural soils is of particular concern in China, while its status, ecological risks, and human health hazards have been little studied in the permafrost areas of Northeast China. In this study, 75 agricultural soil samples (0-20 cm) were collected from the Arctic Village, Mo'he City, in the northernmost part of China. The average concentration (mean ± standard deviation) of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were 12.11 ± 3.66 mg/kg, 0.11 ± 0.08 mg/kg, 52.50 ± 8.83 mg/kg, 12.08 ± 5.12 mg/kg, 0.05 ± 0.02 mg/kg, 14.90 ± 5.35 mg/kg, 22.38 ± 3.04 mg/kg, and 68.07 ± 22.71 mg/kg, respectively. Correlation analysis, cluster analysis, and principal component analysis indicated that As, Cu, Ni, and Zn likely originated from geogenic processes, Hg and Pb from long-range atmospheric transport, Cd from planting activities, and Cr from Holocene alluvium. The geo-accumulation index and enrichment factor showed that As, Cd, Hg, and Zn are enriched in soils. The Nemerow pollution index showed that 66.67%, 24%, and 1.33% of soil samples were in slight, moderate, and heavy pollution levels, respectively, with Hg being the most important element affecting the comprehensive pollution index. The potential ecological risk index showed that 48.00% and 1.33% of soil samples were in the moderate ecological risk and high potential ecological risk levels, respectively. The non-carcinogenic and carcinogenic human health risk index for adults and children were both less than 1, which was within the acceptable range. This study revealed the accumulation pattern of PTEs in agricultural soils of permafrost regions and provided a scientific basis for research on ecological security and human health.

Source apportionment of heavy metal(loid)s in sediments of a typical karst mountain drinking-water reservoir and the associated risk assessment based on chemical speciations.

As important place for water storage and supply, drinking-water reservoirs in karst mountain areas play a key role in ensuring human well-being, and its water quality safety has attracted much attention. Source apportionment and ecological risks of heavy metal(loid)s in sediments of drinking-water reservoir are important for water security, public health, and regional water resources management, especially in karst mountain areas where water resources are scarce. To expound the accumulation, potential ecological risks, and sources of heavy metal(loid)s in a drinking-water reservoir in Northwest Guizhou, China, the surface sediments were collected and analyzed based on the combined use of the geo-accumulation index (Igeo), sequential extraction (BCR), ratios of secondary phase and primary phase (RSP), risk assessment code (RAC), modified potential ecological risk index (MRI), as well as the positive matrix factorization methods. The results indicated that the accumulation of Cd in sediments was obvious, with approximately 61.9% of the samples showing moderate to high accumulation levels, followed by Pb, Cu, Ni, and Zn, whereas the As and Cr were at low levels. A large proportion of BCR-extracted acid extractable and reducible fraction were found in Cd (72.5%) and Pb (40.3%), suggesting high bioavailability. The combined results of RSP, RAC, and MRI showed that Cd was the major pollutant in sediments with high potential ecological risk, while the risk of other elements was low. Source apportionment results of heavy metal(loid)s indicated that Cd (75.76%) and Zn (23.1%) mainly originated from agricultural activities; As (69.82%), Cr (50.05%), Cu (33.47%), and Ni (31.87%) were associated with domestic sources related to residents' lives; Cu (52.36%), Ni (44.57%), Cr (34.33%), As (26.51%), Pb (24.77%), and Zn (23.80%) primarily came from natural geological sources; and Pb (47.56%), Zn (22.46%) and Cr (13.92%) might be introduced by mixed sources of traffic and domestic. The contribution ratios of the four sources were 18.41%, 36.67%, 29.48%, and 15.44%, respectively. Overall, priority control factors for pollution in relation to agricultural sources included Cd, while domestic sources are primarily associated with As. It is crucial to place special emphasis on the impacts of human activities when formulating pollution prevention and control measures. The results of this study can provide valuable reference and insights for water resources management and pollution prevention and control strategies in karst mountainous areas.

Analysis of Toxic Metal-Induced Ecological Risk in Kepez Stream, Çanakkale, Türkiye

Ecological risk in the mouth of Kepez Stream has recently increased notably due to waste from the Kepez settlement, agricultural activity in the Kepez delta, maritime traffic in the Çanakkale Strait, and summer houses in the coastal area. This study analyzed the ecological risk of 10 sediment samples along the bed in the mouth of Kepez Stream to shed light on anthropogenically induced pollution. The pollution proxies such as chlorophyll degradation products, heavy metal concentrations and organic carbon of the sediment samples were determined. Enrichment Factor (EF), Contamination Factor (CF), Geoaccumulation Index (Igeo) and Potential Ecological Risk Index (PER) were calculated from the results obtained. Spearman's correlation analysis and factor analysis were also performed. The obtained data show that there is moderate enrichment of Zn, As and Co, a significant level of Pb, and very high level of Cr in the sediments of Kepez Stream. Ni enrichment was determined to be excessive and poses a high potential ecological risk. Cleaning and rehabilitation need to be carried out urgently in the mouth of Kepez Stream. It should be determined whether metals are being transmitted to aquatic organisms, and measures should be taken to reduce the sources of pollution.

Spatial distribution and ecological risk assessment of heavy metal elements in rock‐soil in the mountainous areas of Southwest China: A case study of Xichang

This study employs the Muller geological accumulation index method and the Hakanson risk assessment method in combination with ArcGIS technology to assess the potential heavy metal pollution in soil. The study aims to investigate the geochemical characteristics, pollution degree, and potential ecological risks associated with soil heavy metal element content and distribution across various geological formations. The concentrations of eight heavy metals, namely Cu, Cd, Ni, Pb, Zn, Hg, As, and Cr, were analysed by collecting samples of the soil layer, parent material layer, and parent rock layer. The proportions of samples with different risk levels are accurately calculated to locate areas with high pollution risks. The findings are as follows: Firstly, the soil pH value in the study area is low, and the Cd and Cr concentrations are 1.38 and 1.20 times the background concentrations in soil in Sichuan Province, respectively. Moreover, Cu, Cd, Ni, Zn, and Cr concentrations are 1.23, 1.10, 1.20, 1.10, and 1.55 times the background concentrations in soil in China. Secondly, the distribution of heavy metal elements varies across different geological formation units, and the heavy metal contents of different samples from the same formation also varies significantly. The concentrations of heavy metal elements are influenced by different geological formations, with the pedogenic parent rock in the soil determining the initial concentrations of heavy metal elements. Thirdly, the spatial distribution of heavy metal elements indicates a good spatial distribution coupling relationship among the soil layer, parent material layer, and rock layer. The study suggests that the contents of the eight heavy metal elements in the soil inherited the characteristics of the parent material to a large extent and are influenced and controlled by the pedogenic parent rock (geological formation). Finally, the evaluation results reveal that all eight heavy metal elements exhibit moderate pollution, with a relatively large distribution area exhibiting moderate Cd, Hg, and As pollution and above. The overall study area exhibits a mild potential ecological risk level, with some areas at a moderate potential ecological risk level, distributed in patches across the study area. Cd and Hg exhibit relatively high potential ecological risks. The potential ecological risks of heavy metals are relatively high in the JKms and Tss units. While the overall quality of the soil in the study area is good, heavy metal pollution and potential ecological risks of some elements are still above ideal levels.

Spatial Distribution and Risk Assessment of Heavy Metal(oid)s Contamination in Topsoil around a Lead and Zinc Smelter in Henan Province, Central China.

A total of 137 farmland soil samples were collected around a lead/zinc smelter within 64 km2. The concentration, spatial distribution, and potential source of nine heavy metal(oid)s (As, Cd, Co, Cr, Cu, Ni, Pb, V, and Zn) in soils and their potential ecological risk were investigated in detail. The results showed that the average concentrations of Cd, Pb, Cr and Zn in these soils were higher than their background value in Henan Province, and the average content of Cd was 2.83 times of the risk screening values in the national standard of China (GB 15618-2018). According to the distribution of different heavy metal(oid)s in soils, Cd and Pb in soil decrease gradually with the increase of distance from the smelter to the surrounding area. This indicates that the Pb and Cd originate from smelters via airborne practices according to the typical air pollution diffusion model. The distribution of Zn, Cu, and As were similar to Cd and Pb. However, Ni, V, Cr, and Co were mainly affected by soil parent materials. The potential ecological risk of Cd was higher than those of other elements, and the risk grade of the other eight elements was mainly low. The polluted soils with significantly high and high potential ecological risk covered 93.84% of all the studied regions. This should be of serious concern to government. The results of a principal component analysis (PCA) and cluster analysis (CA) show that Pb, Cd, Zn, Cu, and As were the elements mainly stemmed from smelter and other types of plants, with a contribution rate of 60.08%, while Co, Cr, Ni, and V are mainly caused by nature, with a contribution rate of 26.26%.

Ecological and health risk assessment of radionuclides and heavy metals of surface and ground water of Ishiagu–Ezillo quarry sites of Ebonyi, Southeast Nigeria

Exposure to heavy metals and natural radionuclides via water sources disposes mankind to deterioration of health. Radionuclides (238U, 232Th, 40K) and heavy metals (Pb, Cr, Cd, As) in surface and borehole waters close to granite quarry sites and the extent of metal contamination for evaluating health risk for individual populations were studied. Mean values of 238U, 232Th, and 40K in surface water (11.56, 8.84 and 35.66 Bq/l) and borehole water (2.68, 10.81 and 18.66 Bq/l) were determined. Total estimated annual effective doses for ingestion of radionuclides via surface and borehole water samples were: children (1.139; 1.058 mSv/y) and adults (2.377; 2.231 mSv/y), adults are more vulnerable to radiation risk. Average heavy metals in both water sources are in order, As >Cr > Pb> Cd. Radionuclides and heavy metals exceeded WHO standards for potable water. Contamination factor, pollution load index, geo-accumulation index, ecological risk and potential ecological risk indices (PERI) showed that surface water contamination is higher than the borehole water within the study areas. Multivariate statistical analysis accounted for 86.30% of the total variance indicating strong correlation between As, Cr, Pb and PERI which was traced to geogenic and anthropogenic sources of the metals that contributed to high potential ecological risk in surface water. Hazard quotient (HQ) and hazard index (HI) (non-carcinogenic) and carcinogenic risk assessment values were within USEPA HQ and HI ≤ 1 and 1 × 10−6 – 1 × 10−4 which portrays little or no significant health effect from the use of studied water sources. Therefore, surface and borehole water within 5 km radius from granite quarry locations should be pretreated before use to avoid long-term effect of pollutants accumulation.

Heavy metals in the sediments of urban sinkholes in Cancun, Quintana Roo

Soils in urban areas can accumulate heavy metals as a result of anthropogenic inputs. This research focuses on a young coastal tourist city that has been urbanized over the last 52 years and shows accelerated demographic growth and urban development. Deposition of heavy metals in soils is caused by human economic activities, which has significant implications for the environment. We evaluated heavy metal concentrations in urban sinkholes, which are sites for the natural accumulation of water and sediments. These locations also receive rainfall runoff or have been used as unregulated dumps. By performing a multistage extraction to address availability and risk, we found that Zn, Fe and Al were the predominant metals; Cu, Pb and Ni were only detected in some sinkholes. The contamination factor was high for Zn and moderate for Pb. The geoaccumulation index showed that Zn is the most abundant and available metal in urban sinkholes and the metal with the highest potential ecological risk. Between 12 and 50% of the total concentration of all metals was extracted from the organic matter phase. Correlations were found between the degree of urbanization of the city and the degree of pollution, and the trends were stronger in older sections of the city. Zn is the most prevalent element and has high concentrations. The metal concentrations in the sediments can be used as warning signs for their potential risk to environmental and human health, and these results can be compared with those of other tourist cities in karstic environments around the world.

Toxic metals and the risks of sludge from the treatment of wastewater from beryllium smelting

The release of highly toxic beryllium in sludge (BCS) produced by physico-chemical treatment of beryllium-containing wastewater from Be smelting production has become a growing concern with the widespread use of Be in the defense industry. This work investigated the potential mobility of Be in BCS. The toxicity characteristic leaching procedure (TCLP) of BCS showed that the amount of leached Be was up to 202 mg L−1, which exceeded the regulated limit by nearly 10,000 times. The chemical fractionation analysis further revealed that the excessive amount of Be leached from BCS was contributed to the high content of acid-soluble fraction and reducible fraction of Be, which accounted for over 70% of the Be content. The results obtained from mineralogical automatic analyzer (MLA) showed that gypsum (23.23%) and epidote (19.55%) were the two major mineralogical phases of BCS. Both were small and loosely structured agglomerated particles with a D50 of 6.61 μm and 3.31 μm. ToF-SIMS results revealed that the Be distribution on the surface of BCS particles was relatively dispersed, with no aggregation or encapsulation. Be co-precipitated with gypsum and chlorite in the form of unstable Be(OH)2, which attached to the surface of these small particles. The unstable state of Be and the small size, loose structure and high liberation of the host material phases are the main reasons for the high leaching mobility of Be. The results of the risk assessment indicated that BCS posed an extremely high potential ecological risk, with Be being the most significant contributor.

Contamination and human health risk assessment of heavy metal(loid)s in topsoil and groundwater around mining and dressing factories in Chifeng, North China

Chifeng is a concentrated mining area for non-ferrous metal minerals, as well as a key prevention and control area for heavy-duty enterprises. This situation necessitates an effective ecological and human health risk assessment of heavy metal(loid)s driven by the wide distribution of metal ore processing, mining, and smelting factories in Hexigten Banner and Bairin Left Banner. We conducted surveys to assess the levels of heavy metal(loid)s (Cr, As, Pb, Cd, and Hg) in the topsoil and groundwater of the areas. The results indicated that the concentrations of As, Cd, and Pb in partial soil samples exceeded the environmental quality standards of Grade II. Based on contamination assessments, such as geoaccumulation indices and pollution indices, we inferred that Cd, Pb, and As were primary pollutants in topsoil. Potential ecological risks when considered as part of the average risk indices (RI) are up to 1626.40 and 2818.76, respectively, in the two areas. Comparative analysis revealed that Cd posed a very high potential ecological risk, followed by As. Moreover, the evaluation showed that the three exposure pathways of carcinogenic and non-carcinogenic risk followed a descending order: inhalation > ingestion > dermal contact, except for Pb. Arsenic in topsoil posed a potential non-carcinogenic risk to human health, while there were no adverse effects of As in groundwater. In addition, the average total carcinogenic risk for As in the two areas, as well as the risk of Pb in the topsoil of Bairin Left Banner and all the five heavy metal(loid)s in groundwater, exceeded human tolerance. Pb–Zn mines caused higher human health risks. In addition, the tandem contamination of heavy metal(loid)s in soil and groundwater was not obvious. This research study provides a basis for pollution remediation to control heavy industry-induced ecological and health risks of heavy metal(loid)s.

Nematode as a biomonitoring model for evaluating ecological risks of heavy metals in sediments from an urban river

Heavy metals have attracted much attention due to their irreversibility, persistence, concealment and bioaccumulation. Biomonitoring method combined chemical analysis can be well evaluate health risks of heavy metals in the environment. In this study, eleven sediments and water samples were collected along Xihe River, which was polluted by heavy metals in Shenyang city of China. The content of multiple heavy metals in these samples was determined by inductively coupled plasma mass spectrometry. 18S rRNA gene sequencing was performed to identify the composition and diversity of nematodes in fine River sediments. The biological toxicity of water-soluble extracts from the samples was further assessed by referring to different endpoints of Caenorhabditis Elegans. The results indicated that the risk of heavy metals in Xihe River was high (potential ecological risk index = 308.75), in which Hg and Cd are the main contributing factors. The relative abundance of nematodes complemented the chemical analysis result, Enoplida, Mononchida, Triplonchida, and Chromadorida nematodes presented a significant positive correlation with the concentration of heavy metals. Specially, Chromadorida nematodes were sensitive to changes in heavy metals in Xihe River, which was significant positively correlated with As, Pb and V. Therefore, nematodes such as Chromadorida can be applied in environmental monitoring to evaluate the health risks of heavy metals.