Calculation and application of Sb toxicity coefficient for potential ecological risk assessment

The release of antimony from soils surrounding the smelters in Karst Areas and its Environmental Implications

Antimony(Sb) in soil can be reintroduced into the environment through leaching processes driven by rainfall and surface runoff, raising concerns about secondary pollution. This study examined the release dynamics of Sb in carbonate-rich soils from an Sb smelting area in the karst region of southern China, aiming to elucidate the roles of pH, organic matter (OM), and geological conditions in Sb mobilization. The experiment was conducted under three different pH conditions (4.5, 6.0, and 7.5) and explores the influence of OM on the release behavior of Sb in the soil. Results indicated a characteristic release pattern for Sb in the soil solution, with an initial rapid increase, followed by a sharp decline, and a subsequent rise.The leaching rate of Sb was higher in neutral to weakly alkaline soil compared to acidic soils.The removal of soil OM enhanced Sb release by 3.21-4.09 times, with a significant inhibition rate reaching 50.01-76.86 %. The findings suggested Sb release kinetics followed a triphasic pattern consisting of rapid initial release, mid-term adsorption inhibition, and late-stage secondary release, which elucidated the underlying mechanisms of long-term leaching risks and provided a theoretical foundation for predicting contaminant dispersion. Soil OM effectively reduced Sb mobility through functional group complexation and soil aggregate formation, offering direct evidence for OM-based remediation strategies such as organic amendment applications. Neutral to weakly alkaline conditions (pH 6.0-7.5) significantly enhanced Sb release rates by promoting mineral desorption, indicating elevated contamination risks of Sb in karst region soils. This study emphasizes that priority should be given to increasing OM concentration and regulating pH buffering capacity to suppress Sb activity in karst areas, providing actionable scientific solutions for the remediation and management of Sb-contaminated sites.

Pollution risk assessment and source apportionment of potentially toxic elements in agricultural soils using the APCS-MLR model: a case study near a non-ferrous metal smelting slag site in Gejiu, Yunnan

Industrial development has caused significant environmental damage, especially through potentially toxic element (PTE) pollution. Combining pollution indices, health risk assessment, spatial autocorrelation (Moran's I), and receptor modeling (APCS/MLR), this study quantified sources and risks of heavy metals in smelting-adjacent farmland soils, facilitating targeted PTE pollution mitigation. Soil analysis revealed significantly elevated mean concentrations of As (326 mg/kg), Cd (23 mg/kg), Cr (104 mg/kg), Cu (106 mg/kg), Ni (73 mg/kg), Pb (274 mg/kg), and Zn (660 mg/kg), all exceeding Yunnan provincial background values. The average total non-carcinogenic risk index (HIadult = 2, HIchild = 11) and total carcinogenic risk index (TCRadult = 5.52 × 10-4, TCRChild = 6.44 × 10-4) for both adults and children exceeded the threshold (HI = 1, TCR = 1 × 10-04). The results of environmental pollution evaluation show that the overall pollution in the study area is a heavy pollution level. The ACPS-MLR model showed that Cd and Zn in soil mainly came from industrial activities (37%). Cu and Pb were derived from motor vehicle emissions and agricultural activities (20%). As may be derived from agricultural and industrial activities. Furthermore, based on the combination of source apportionalization and the spatial distribution of environmental pollution, the northeastern part of the study area and transportation hubs are the key pollution areas and need to be given priority for treatment. PTEs accumulate in the soil, will be enriched through the food chain, and seriously threaten human health and soil ecological environment. Therefore, this study can provide a basis for identifying, preventing, and controlling the risk of PTEs pollution in soil.

Geospatial analysis of trace metal pollution and ecological risks in river sediments from agrochemical sources in Morocco's Sebou basin

Sediments in agricultural ecosystems serve as critical indicators of environmental pollution, particularly in regions subjected to intensive agricultural practices. This research evaluates the environmental hazards and implications of heavy metal (HM) contamination in river sediments from the Sidi Allal Tazi area within Morocco's Sebou basin. Twenty sediment samples were extracted from strategically designated locations, and the contamination levels were analyzed using a multi-index integration approach, multi-statistical analyses (MSA), and Geographic Information Systems (GIS). The results revealed considerable spatial variability in HM concentrations, with Cd and As displaying the highest contamination levels. Statistical analysis, incorporating Principal Component Analysis (PCA), identified anthropogenic activities as the primary contributors to contamination. Hierarchical Cluster Analysis (HCA) categorized metals based on common pollution pathways, while GIS mapping revealed the spatial distribution of contamination across vulnerable areas. Pollution indicators like the Geo-accumulation Index (Igeo) as well as the Pollution Load Index (PLI). revealed that 75% of sites were categorized under "very high pollution", emphasizing the severity of contamination. Contamination Factor (CF) classified 90% of Cd samples and 100% of As samples as "very high contamination". Risk indices indicated significant ecological threats, with Cd contributing to an RI exceeding 600 in many areas, signifying "very high risk". These findings highlight the urgent need for targeted mitigation strategies and sustainable agricultural practices. The integration of multi-index and GIS methodologies provides a comprehensive framework for assessing and managing sediment contamination, offering critical insights for policymakers and environmental managers.

Assessing natural background concentrations of chemical elements in urban soils: A case study in Benevento (Italy)

The main objective of this study is to propose a method to determine, as accurately as possible, the natural background content of a chemical element in urban soils, identify potential sources, and quantify emissions from human activities. To achieve this, 156 topsoil samples were taken from the surface horizon of the soil (first 20 cm) and analysed for 25 elements using a combination of inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS), after aqua regia digestion. The concentration data obtained were rigorously analysed using multivariate statistical analysis methods, including compositional data analysis (CoDA), clustering and dimension reduction techniques. This analysis separated the data into distinct populations, each characteristic of a natural or anthropogenic phenomenon. The ProUCL 5.2.0 software package was then used to calculate the natural background levels of each element for each data population. The background of some elements, including Co and Tl, exceeds the threshold values imposed in Italy by environmental law in some areas. These findings, together with the use of specific indices, allowed us to precisely define the degree of potentially toxic elements enrichment and the potential ecological risk of the studied area, thus providing valuable information for decisions on urban planning and environmental policy and potentially influencing future strategies for managing urban soil health.

Integrating spatial heterogeneity and speciation dynamics in source apportionment of toxic metal(loid)s at an abandoned hydrometallurgical zinc smelting site

Zinc hydrometallurgy sites are critical hotspots for combined toxic metal(loid)s (TMs) pollution, yet the integration of spatial heterogeneity and migration dynamics into source apportionment remains underexplored. This study investigated the concentrations, speciation, and spatial distribution of nine TMs (As, Cd, Cu, Hg, Mn, Ni, Pb, Sb, Zn) in soils at an abandoned zinc smelter in southwest China. Multivariate statistical methods and the Positive matrix factorization (PMF) model were applied to disentangle primary sources and secondary redistribution. Spatial analysis revealed that As, Cd, Cu, Pb, Sb, and Zn shared similar contamination patterns, concentrated in slag storage and comprehensive recovery areas, whereas Hg and Mn exhibited distinct hotspots near sulfuric acid production and electrolysis zones. Vertical migration was most pronounced for Cd and Zn (> 8 m depth), followed by Hg and Mn (4-8 m), while As, Cu, Pb, and Sb were restricted to 0-4 m due to adsorption in clay-rich layers. Speciation analysis indicated high mobility of Cd and Zn (acid-soluble fraction: 66.96 and 52.10%, respectively), contrasting with reducible Pb and Mn (51.59 and 48.32%) and residual As, Hg, Ni, Sb (60.74-76.64%). The results from PMF model identified aqueous-phase (Cd, Zn, Mn) and solid-phase (As, Cu, Pb, Sb) migration pathways, validated by spatial correlations with topography and functional zones. Aqueous-phase contributions dominated low-lying areas, while solid-phase contributions aligned with elevated regions, reflecting topography-driven redistribution. This study advances source apportionment of TM in soil by unifying spatial heterogeneity, speciation dynamics, and receptor modeling, offering a framework for targeted risk assessment and remediation of industrial sites.

Heavy metal(loid) contamination in forest fire affected soil and surface water: pollution indices and human health risk assessment

Forest fires, whether natural or anthropogenic, release and mobilize heavy metal(loids) (HM). Following intense rainfall events, soil-bound HM are transported from soil to surface water through surface runoff, leading to water quality deterioration. Pollution and ecological risk indices are effective tools for assessing HM contamination. Most forest fire-affected soils and surface water exhibited a degree of contamination greater than 3 and 8 (high and moderate pollution), with associated high and extremely high ecological risks (165 and 2389, respectively). Pollution indices revealed that soils were highly contaminated with Ni, Cu, Cr, and Pb, while Ni, Cu, Hg, Cd, and As posed significant ecological risks. Surface water was heavily contaminated with Pb, Mn, Al, and Fe, with Ni and V contributing to extremely high ecological risks. This study highlights that trace HM also requires substantial removal efforts to make water potable, with removal efficiencies needed for Sb (94.49%), Be (85.83%), Ba (70.75%), V (68.19%), and Se (65.51%). Fire-affected surface water poses an elevated cancer risk to both children (0.18 and 4.5 × 10-3) and adults (0.39 and 1.53 × 10-3) through oral and dermal exposure, respectively. Children are more vulnerable to dermal cancer and noncancer risks compared to adults. Low-cost treatment methods, such as the application of immobilizing agents combined with compost, straw mulching, and seeding, can be implemented to control soil erosion in forest areas, thereby reducing the transport of soil-bound HM to surface water. These findings can aid government agencies in developing new soil and water quality standards and implementing effective treatment measures.

Assessment of potential ecological risk by metals in Ilha Grande Bay (Southeast Brazil)

This study evaluates contamination and potential ecological risk in Ilha Grande Bay (BIG) in southeastern Brazil. To achieve these objectives, we analyzed physicochemical, sediment textural, and geochemical data from 134 stations distributed throughout the bay. The results reveal significant environmental degradation in the coastal areas of Paraty, Saco do Mamanguá, Angra dos Reis City, and Abraão Cove (at Ilha Grande island). These regions exhibit moderate to significant pollution from metals. High potential ecological risk was identified in approximately 87 stations (about 65 %), primarily due to Hg, Cd, and As, with additional contributions from Tl, Ni, and Cu. Evidence indicates that concentrations of these chemical elements have been increasing in recent years. Among these metals, Hg is particularly concerning because of its toxicity and persistence in the environment. The primary sources of contamination in BIG appear to be urban and industrial effluents, metalworks, the combustion of coal and oil, and the incineration of waste and sewage sludge, all of which have contributed to rising pollution levels over the past two decades. Sedimentary processes also facilitate the formation of pollution patches. It is crucial to address the recent escalation in contamination by effectively controlling pollution sources. This study recommends revising the methods and standards for metals established by national and international legislation to better assess sediment quality in marine environments.

Multi-isotopes (18O, 34S, 15N, and 13C) reveal the enrichment mechanism of antimony in high-antimony groundwater

Multi-isotopes can be effectively utilized to offer new insights into heavy-metal oxidation dynamics and variations in redox conditions. Therefore, hydrochemical data and isotopic characteristics (δ18OH2O, δD, δ34SSO4, δ18OSO4, δ15NNO3, δ18ONO3, δ13CDOC and δ13CDIC) were determined the oxidation mechanism of Sb(III) to Sb(V) in D3x4 groundwater. The results showed the concentration of Sb in D3x4 groundwater ranges from 0.005 to 20.700 mg/L, with an average of 2.300 mg/L, and Sb(V) represented the dominant form present within D3x4 groundwater. The δ34S、δ15N values in D3x4 groundwater ranges from -4.20‰ to 6.30‰, 1.20‰ to 22.70‰, respectively. the δ13CDOC and δ13CDIC content in D3x4 groundwater vary in the ranges of -26.97‰ to -16.70‰ and -17.84‰ to -2.30‰, respectively. Stibnite oxidation significantly influenced the enrichment of Sb(V) and SO42-, while microbial nitrification notably contributed to elevated NO3- levels in high-Sb groundwater by converting Sb(III) to Sb(V). The presence of redox-active moieties in DOM facilitated electron transfer for promoting Sb(III) oxidation rate during the stibnite oxidation process. Additionally, microbial oxidative degradation of DOM can promote Sb(V) enrichment, with carbon serving as an energy source for nitrification, facilitated this process and enhances the oxidation rate of Sb(III) to Sb(V). These findings contribute to a more comprehensive understanding of the geochemical behavior of antimony in groundwater and enhance our knowledge regarding Sb(III) oxidation mechanism in oxygenated groundwater.

Development of optimisation methods to identify sources of pollution and assess potential health risks in the vicinity of antimony mines

After elevated levels of lead (Pb) were found in the blood of children living near the antimony (Sb) mine and battery smelter in Zajača, Republic Serbia, studies were carried out to determine the health risk assessment (HRA) effects of the soil. In this study, for the first time a combination of Network Analysis, CoDA (Compositional Data Analysis) and receptor modelling was used to determine the geopedological and atmospheric origin of PTEs in soil and their historical significance. It was found that arsenic (As) and Pb are the main pollutants in the area. The largest contribution to the environmental risk (Er) was made by Pb. In addition to perception methods Network Analysis (NA) was used to determine the source of pollution and, for the first time, the strength of the positive and negative connections of the network nodes of the mutual influence of PTE. Lead pollution was found to originate from two sources: historical and present, and As was found to originate from a wider area. For the child population, an unacceptable risk for the occurrence of chronic diseases with a probability of 95% was found, with As and Pb accounting for the highest percentage. Similarly, As has the greatest impact on occurrence of cancer at the unacceptable risk level, while Pb is at the notable risk level. The historical exposure to Pb is slightly lower and the difference is slightly more pronounced for total pollution for HRA.

Exploring environmental risk in soils: Leveraging open data for non-sampling assessment?

Soil contamination by heavy metals (HM) is a critical area of research. Traditional methods involving sample collection and lab analysis are effective but costly and time-consuming. This study explores whether geostatistical analysis with GIS and open data can provide a faster, more precise, and cost-effective alternative for HM contamination assessment without extensive sampling. Concentrations of nine HMs (Cu, Pb, Ni, Co, Mn, As, Cd, Sb, Cr) were analysed from 498 soil samples collected in two mining areas in Portugal: the Panasqueira and Aljustrel mines. Corresponding data were extracted from the Lucas TOPSOIL 1 km raster maps. Several contamination indices, Contamination Factor (Cf), Modified Contamination Degree (mCd), Geoaccumulation Index (Igeo), Nemerow Pollution Index (Pn), Potential Ecological Risk Index (PERI), and Pollution Load Index (PLI) were calculated for both datasets. A confusion matrix was used to evaluate the percentage of correct classifications, while a concordance analysis assessed the alignment of accurately classified points between the two data sources. In the soil samples, very high contamination levels for As were observed in 42% of the samples, according to the Cf, with high levels for Sb found in approximately 30% of the samples. The mCd revealed that approximately 11% of soil samples exhibited very high levels of contamination, while the Pn indicated that 78.9% of the soil samples fell within the seriously polluted domain. Similar contamination trends were observed for the other indices. In contrast, the results for the LUCAS points showed significant discrepancies. No high contamination levels were found for any metal. The misclassification rates for mCd, Pn, PERI, and PLI were 84.25%, 97.55%, 95%, and 82%, respectively, when compared to the field data. This study concludes that while open data raster maps offer rapid overviews, they fall short of providing the detailed precision required for reliable contamination assessments. The significant misclassification rates observed highlight the limitations of relying solely on these tools for critical environmental decisions. Consequently, traditional sampling and laboratory analysis remain indispensable for accurate risk assessments of HM contamination, ensuring a more reliable foundation for decision-making and environmental management.

Priority sources identification and risks assessment of heavy metal(loid)s in agricultural soils of a typical antimony mining watershed

Heavy metal(loid) (HM) pollution in agricultural soils has become an environmental concern in antimony (Sb) mining areas. However, priority pollution sources identification and deep understanding of environmental risks of HMs face great challenges due to multiple and complex pollution sources coexist. Herein, an integrated approach was conducted to distinguish pollution sources and assess human health risk (HHR) and ecological risk (ER) in a typical Sb mining watershed in Southern China. This approach combines absolute principal component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) models with ER and HHR assessments. Four pollution sources were distinguished for both models, and APCS-MLR model was more accurate and plausible. Predominant HM concentration source was natural source (39.1%), followed by industrial and agricultural activities (23.0%), unknown sources (21.5%) and Sb mining and smelting activities (16.4%). Although natural source contributed the most to HM concentrations, it did not pose a significant ER. Industrial and agricultural activities predominantly contributed to ER, and attention should be paid to Cd and Sb. Sb mining and smelting activities were primary anthropogenic sources of HHR, particularly Sb and As contaminations. Considering ER and HHR assessments, Sb mining and smelting, and industrial and agricultural activities are critical sources, causing serious ecological and health threats. This study showed the advantages of multiple receptor model application in obtaining reliable source identification and providing better source-oriented risk assessments. HM pollution management, such as regulating mining and smelting and implementing soil remediation in polluted agricultural soils, is strongly recommended for protecting ecosystems and humans.

Heavy metal contamination assessment and source attribution in the Vicinity of an iron slag pile in Hechi, China: Integrating multi-medium analysis

Heavy metals, such as mercury, cadmium, and nickel, may contaminate human inhabited environments, with critical consequences for human health. This study examines the health impacts of heavy metal pollution from an iron slag pile in Hechi, China, by analyzing heavy metal contamination in water, sediment, soil, and crops. Here, the Nemerow pollution index (NI) indicated severe pollution at most sampling sites, the mean NI of groundwater, and surface water had reached 594.13 and 26.79, respectively. Bioaccumulation of mercury (Hg), cadmium (Cd), and nickel (Ni) was noted in crops, cucumbers showed comparatively lower risk levels. Logarithmic surface water-sediment partition coefficient calculations indicated that heavy metals such as chromium (Cr), ferrum (Fe), zinc (Zn), copper (Cu), Ni, arsenic (As), and lead (Pb) tend to accumulate in sediments. There was a high risk in groundwater (67.48-6590.54) and surface water (13.73-2500.85). Variably influenced by rainfall, these metals can be diluted and mobilized from surface water and sediments, thereby changing the contamination levels and ecological risks. Probabilistic health risk assessments indicated that health risks were higher in children than in adults, the mean total carcinogenic risk values of soil, groundwater, and surface water, were 6.79E-04, 4.20E-06, and 1.15E-6 for children, respectively. Moderate soil pollution is the main health hazard. A Positive Matrix Factorization model attributed over 60% of the pollution to slag stacking. Biotechnologies, solidification/stabilization techniques, field management, and institutional controls, driven by principles of green, low-carbon, and economic efficiency may mitigate. These findings contribute to the management of heavy metal pollution in iron slag pile areas.

Human health and ecological risk assessment of heavy metals in topsoil of different peatland use types

Peatlands, known for their ability to retain and immobilize heavy metals due to unique waterlogged conditions and organic matter, face challenges when subjected to disturbances such as land use changes. These disruptions alter the organic matter, redox potential, and pH of the peatsoil, potentially influencing the migration, mobilization, and increased availability of stored heavy metals. Peatsoil samples from various peatland use types (improved and semi-natural grassland, forest, industrial cutaway bog) were collected to assess the human health and ecological risk associated with heavy metals (Cd, Cu, Hg, Pb, and Zn) in Co-Offaly, Ireland. Results reveal variations in heavy metal concentrations across peatland use types, with Cd, Hg, and Pb in improved and semi-natural grassland peatsoils exceeding the World Health Organization (WHO) permissible safety limits. Contamination factors (CF) were higher in improved grassland, especially for Cd and Pb, exceeding one. Hakanson potential ecological risk assessment indicates acceptable overall risk levels, though variations exist between improved grassland, unimproved grassland, forest, and industrial cutaway bog. Combined exposure routes (dermal, ingestion and inhalation routes) to all heavy metals do not exceed safe exposure levels (indicating low non-carcinogenic risks. However, the cancer risk (CR) exceeds acceptable thresholds across all use types, with higher CR in improved grassland, especially for children. Overall, the findings emphasize the need for careful consideration of heavy metal risks associated with land use changes in peatlands, particularly in the improved grassland areas.

Considering the bioavailability and bioaccessibility of metal(loid)s for risk assessment of soils affected by different non-ferrous metal activities in Southwest China

Toxic metal(loid)s released into the soil by non-ferrous metal mining and smelting activities pose a serious threat to residents and the surrounding ecosystem. Considering only total metal(loid) concentrations likely overestimates routine (eco)toxicological risk assessment of soil. We hypothesize that considering metal(loid) bioavailability/accessibility will improve the accuracy of risk assessment. To test this hypothesis, four mining areas in Southwest China, including mining and surrounding sites, were studied. Bioavailability was determined considering metal(loid)s leached by a simulated strong acid rain (SSAR) treatment. In the four areas, the mining site showed higher cumulative releases of metal(loid)s under SSAR treatment than the agricultural field located in the surrounding sites. Thus, the bioavailable metal(loid)s contents were continuously being released during SSAR treatment and likely increased the environmental risk. Ecological and health risk assessment of soil, calculated using total metal(loid)s content, was corrected considering bioavailable/accessible metal(loid)s, which was determined by the heavy metal(loid)s forms and in vitro simulated intestinal stages. Although the corrected indices indicated that the risk of metal(loid)s-contaminated soil was reduced, unfavorable ecological and health risks remained in the four areas. Our study provides new perspectives to better predict the risk of bioavailable/accessible metal(loid)s in non-ferrous metal contaminated and surrounding soils.

Arsenic and fluoride in groundwater triggering a high risk: Probabilistic results using Monte Carlo simulation and species sensitivity distribution

The widespread presence of arsenic (As) and fluoride (F-) in groundwater poses substantial risks to human health on a global scale. These elements have been identified as the most prevalent geogenic contaminants in groundwater in northern Mexico. Consequently, this study aimed to evaluate the human health and ecological risks associated with the content of As and F- in the Meoqui-Delicias aquifer, which is in one of Mexico's most emblematic irrigation districts. Concentrations of As and F- were measured in 38 groundwater samples using ICP-MS and ion chromatography, respectively. Overall, these elements showed a similar trend across the aquifer, revealing a positive correlation between them and pH. The concentration of As and F- in the groundwater ranged from 5.3 μg/L to 303 μg/L and from 0.5 mg/L to 8.8 mg/L, respectively. Additionally, the levels of As and F- surpassed the established national standards for safe drinking water in 92% and 97% of samples, respectively. Given that groundwater is used for both agricultural purposes and human activities, this study also assessed the associated human health and ecological risks posed by these elements using Monte Carlo simulation and Species Sensitivity Distribution. The findings disclosed a significant noncarcinogenic health risk associated with exposure to As and F-, as well as an unacceptable carcinogenic health risk to As through water consumption for both adults and children. Furthermore, a high ecological risk to aquatic species was identified for F- and high to medium risks for As in the sampling sites. Therefore, the findings in this study provide valuable information for Mexican authorities and international organizations (e.g., WHO) about the adverse effects that any exposure without treatment to groundwater from this region represents for human health.

Comparison of antimony and arsenic behaviour at the river-lake junction in the middle of the Yangtze River Basin

As typical metalloid toxic elements widely distributed in environmental media, the geochemical behaviour of antimony (Sb) and arsenic (As) affects environmental safety. We selected the surface waters and sediments at the river-lake junction of Dongting Lake as the research objects, analysed the concentration and chemical partitioning of Sb and As, assessed its contamination and ecological risk levels, and discussed its sources and potential influencing factors. The concentrations of dissolved Sb and As in surface waters were low (< 5.46 µg/L), and the concentrations of Sb and As in surface sediments were 2.49-22.65 mg/kg and 11.10-136.34 mg/kg, respectively. Antimony and As in sediments were mainly enriched in the fraction of residues, but the proportion of As in bioavailability was significantly higher than that of Sb. Although the contamination level of Sb was higher than that of As, the risk assessment code (RAC) showed that the ecological risk level of As was higher than that of Sb. Rainwater erosion and mining activities (in the midstream of Zijiang River) were the main contaminated sources of Sb, while As was affect mainly by rainwater erosion. The contamination and ecological risk of Sb in the inlet of the Zijiang River should receive considerable attention, while those of As in the inlet of the Xiangjiang River should also be seriously considered. This study highlights the need for multi-index-based assessments of contamination and ecological risk and the importance of further studies on the environmental behaviour of metalloids in specific hydrological conditions, such as river-lake junctions.

Potential Linkage between Heavy Metal Pollution Risk Assessment and Dissolved Organic Matter Spectra in the WWTPs-River Integrated Area-Case Study from Ashi River

Direct sewage discharge can cause severe damage to the water environment of the river. However, the impacts of dissolved organic matter (DOM) in the discharge on the original pattern of DOM and the distribution of heavy metals (HMs) in the river are little known. How to monitor such areas in a long-term and systematic manner also needs to be urgently addressed. In this paper, we characterized the DOM of the sediments in the WWTPs (wastewater treatment plants)-river integrated zone by ultraviolet-visible absorption spectroscopy (UV-vis), three-dimensional excitation-emission matrix (3D-EEM) combined with parallel factor (PARAFAC) method. The effects of WWTP on receiving waters were investigated, and the potential link between DOM and HM pollution was explored. Hg (Igeo: 3.94 ± 0.65; EF: 44.83 ± 31.11), Cd (Igeo: 1.81 ± 0.69; EF: 8.02 ± 2.97), Cu (Igeo: 1.61 ± 0.83; EF: 6.85 ± 2.37), Zn (Igeo: 1.55 ± 0.54; EF: 7.24 ± 3.58), and Ni (Igeo: 1.46 ± 0.56; EF: 6.12 ± 1.99) in rivers were the primary risk sources of HM. The combined pollution risk indicates that the WWTPs-river integrated area is in a high pollution risk state. Moreover, α(254) has a significant correlation with pollution indicators and can be used as a proxy indicator. These results help to understand better the impact of WWTPs on receiving water bodies and the potential connection between DOM and HM pollution and provide new ideas for monitoring the water environment in highly polluted areas.

The new era hypothesis of coastal degradation: G(s) elements-gallium, gadolinium, and germanium

Mining of precious metals contributes to environmental pollution, especially in coastal areas, and conventional treatment methods are not always effective in removing metal contaminants. Some of these metals, such as gadolinium, germanium and gallium, have caused increasing concern worldwide, as little is known about their current concentrations in the aquatic environment and their biological significance. Therefore, the aim of this study was to determine for the first time the variation of average G(s) concentrations (gallium, gadolinium and germanium) by month/season/site differences along the coast of Istanbul. The ecological risk index was calculated to assess the contamination of seawater and to serve as a diagnostic tool for the mitigation of water pollution. The average distribution G(s) in seawater was in the following order: Ga > Gd > Ge. In addition, the potential ecological risk in the sampling areas ranged from 68 to 1049. Of the three metals, Gd poses the highest ecological risk (grade III). In the spatial distribution of ecological risks, Gd mainly originated from discharges from wastewater treatment plants. Therefore, the sources of the anthropogenic Gd anomaly in wastewater should be identified, as this indicates the possibility of human exposure to potentially harmful anthropogenic compounds.

Recent advances in sulfidized nanoscale zero-valent iron materials for environmental remediation and challenges

Over the past decade, sulfidized nanoscale zero-valent iron (S-nZVI) has been developed as a promising tool for the remediation of contaminated soil, sediment, and water. Although most studies have focused on applying S-nZVI for clean-up purposes, there is still a lack of systematic summary and discussion from its synthesis, application, to toxicity assessment. This review firstly summarized and compared the properties of S-nZVI synthesized from one-step and two-step synthesis methods, and the modification protocols for obtaining better stability and reactivity. In the context of environmental remediation, this review outlined an update on the latest development of S-nZVI for removal of heavy metals, organic pollutants, antibiotic resistance genes (ARGs), and antibiotic resistant bacteria (ARB) and also discussed the underlying removal mechanisms. Environmental factors affecting the remediation performance of S-nZVI (e.g., humic acid, coexisting ions, S/Fe molar ratio, pH, and oxygen condition) were highlighted. Besides, the application potential of S-nZVI in advanced oxidation processes (AOP), especially in activating persulfate, was also evaluated. The toxicity impacts of S-nZVI on the environmental microorganism were described. Finally, the future challenges and remaining restrains to be resolved for better applicability of S-nZVI are also proposed. This review could provide guidance for the environmental remediation with S-nZVI-based technology from theoretical basis and practical perspectives.

Effects of complex sulphur substrates on sludge bioleaching to improve heavy metal removal and microbial community diversity

In this study, H2S was used as a partial replacement nutrient substrate for sludge bioleaching. The effects of different combinations of H2S/sludge load and monomeric sulphur on heavy metal removal and microbial communities were investigated. Changes in pH, oxidation-reduction potential (ORP), SO42- concentration, heavy metal removal, and the content of heavy metal states during bioleaching were investigated, and community diversity analysis was performed. Daily introduction of H2S three times (at an interval of 8 h) at a gas flow rate of 2 ml/min and an H2S/sludge load of 15 ml/L with 5 g/L FeSO4·7H2O and 2 g/L monomeric sulphur as a nutrient substrate significantly accelerated both the bioleaching process and the pH drop in the sludge system, promoted the production of SO42-, and maintained a higher redox potential. The combination of H2S and monomeric sulphur had a significant effect on the leaching of heavy metals. Compared with the experimental group containing only H2S or monomeric sulphur, the removal rates of Zn, Ni, Pb, and Cr increased by 4.63%/13.8%, 8.5%/20.07%, 3.84%/9.5%, and 4.24%/8.02% respectively, while promoting the transformation of various heavy metal states to labile states, improving heavy metal stability, and reducing sludge ecotoxicity. High-throughput sequencing analysis showed that introducing the H2S gaseous matrix accelerated the decreasing trend of species number, bacterial abundance, and community diversity in the sludge system, promoting Proteobacteria as the dominant phylum, Acidithiobacillus, Metallibacterium, and Thiomonas as the dominant genera, and improving the bioleaching treatment effect.

High-resolution risk mapping of heavy metals in soil with an integrated static-dynamic interaction model: A case study in an industrial agglomeration area in China

Heavy metal pollution of soils in industrial agglomeration areas is an increasing concern worldwide. In this study, we traced the sources of heavy metal emissions using a positive matrix factorization (PMF) model. Accordingly, we proposed a novel static-dynamic risk interaction model incorporating multiple risk-related factors to quantify the spatial interaction of emission sources and the probability of accumulation of heavy metals on a large scale. This model was further classified using the Jenks optimization technique to predict the spatial distribution of high-risk hotspots. Our results determined four primary emission sources of heavy metals: industrial (35.01 %), natural (28.61 %), agricultural (26.07 %), and traffic (10.31 %) sources. Five levels were classified by the integrated risk coefficient (IRC), namely, from extremely high to extremely low risk. The extremely high- and high-risk hotspots constituting 41.52 % of the total area of the Zhenhai District, with IRC values ranging from 0.221 to 0.413, were mainly generated by multiple sources linked to PMF-based factors. This quantitative evaluation framework can generate a high-resolution spatially distributed pollution risk map at the grid scale (1 km), which can provide a relatively precise basis for policymaking for point-to-point soil pollution management.

A new strategy for risk assessment of PM2.5-bound elements by considering the influence of wind regimes

For regulatory purposes, air pollution has been reduced to management of air quality control regions (AQCR), by inventorying pollution sources and identifying the receptors significantly affected. However, beyond being source-dependent, particulate matter can be physically and chemically altered by factors and elements of climate during transport, as they act as local environmental constraints, indirectly modulating the adverse effects of particles on the environment and human health. This case study, at an industrial site in a Brazilian coastal city - Joinville, combines different methodologies to integrate atmospheric dynamics in a strategic risk assessment approach whereby the influence of different wind regimes on environmental and health risks of exposure to PM_2.5-bound elements, are analysed. Although Joinville AQCR has been prone to stagnation/recirculation events, distinctly different horizontal wind circulation patterns indicate two airsheds within the region. The two sampling sites mirrored these two conditions and as a result we report different PM_2.5 mass concentrations, chemical profiles, geo-accumulation, and ecological and human health risks. In addition, feedback mechanisms between the airsheds seem to aggravate the air quality and its effects even under good ventilation conditions. Recognizably, the risks associated with Co, Pb, Cu, Ni, Mn, and Zn loadings were extremely high for the environment as well as being the main contributors to elevated non-carcinogenic risks. Meanwhile, higher carcinogenic risks occurred during stagnation/recirculation conditions, with Cr as the major threat. These results highlight the importance of integrating local airshed characteristics into the risk assessment of PM_2.5-bound elements since they can aggravate air pollution leading to different risks at a granular scale. This new approach to risk assessment can be employed in any city's longer-term development plan since it provides public authorities with a strategic perspective on incorporating environmental constraints into urban growth planning and development zoning regulations.

Short-term exposure to antimony induces hepatotoxicity and metabolic remodeling in rats

Antimony (Sb) poses a significant threat to human health due to sharp increases in its exploitation and application globally, but few studies have explored the pathophysiological mechanisms of acute hepatotoxicity induced by Sb exposure. We established an in vivo model to comprehensively explore the endogenous mechanisms underlying liver injury induced by short-term Sb exposure. Adult female and male Sprague-Dawley rats were orally administrated various concentrations of potassium antimony tartrate for 28 days. After exposure, the serum Sb concentration, liver-to-body weight ratio, and serum glucose levels significantly increased in a dose-dependent manner. Body weight gain and serum concentrations of biomarkers of hepatic injury (e.g., total cholesterol, total protein, alkaline phosphatase, and the aspartate aminotransferase/alanine aminotransferase ratio) decreased with increasing Sb exposure. Through integrative non-targeted metabolome and lipidome analyses, alanine, aspartate, and glutamate metabolism; phosphatidylcholines; sphingomyelins; and phosphatidylinositols were the most significantly affected pathways in female and male rats exposed to Sb. Additionally, correlation analysis showed that the concentrations of certain metabolites and lipids (e.g., deoxycholic acid, N-methylproline, palmitoylcarnitine, glycerophospholipids, sphingomyelins, and glycerol) were significantly associated with hepatic injury biomarkers, indicating that metabolic remodeling may be involved in apical hepatotoxicity. Our study demonstrated that short-term exposure to Sb induces hepatotoxicity, possibly through a glycolipid metabolism disorder, providing an important reference for the health risks of Sb pollution.

Evaluating potential ecological risks of emerging toxic elements in lacustrine sediments: A case study in Lake Fuxian, China

The fragile ecosystems of plateau lakes are in face of ecological risks from emerging toxic elements. Beryllium (Be) and thallium (Tl) have been considered priority control metals in recent years owing to their persistence, toxicity, and bioaccumulation. However, the toxic factors of Be and Tl are scarce and ecological risks of them in the aquatic environment were seldom investigated. Hence, this study developed a framework for calculating the potential ecological risk index (PERI) of Be and Tl in aquatic systems and used it to assess the ecological risks of Be and Tl in Lake Fuxian, a plateau lake in China. The toxicity factors of Be and Tl were calculated to be 40 and 5, respectively. In sediments of Lake Fuxian, the concentrations of Be and Tl were between 2.18 and 4.04 mg/kg and 0.72-0.94 mg/kg, respectively. The spatial distribution indicated that Be was more abundant in the eastern and southern regions, and Tl had higher concentrations near the northern and southern banks, consistent with the distribution of anthropogenic activities. The background values were calculated as 3.38 mg/kg and 0.89 mg/kg for Be and Tl, respectively. In comparison with Be, Tl was more enriched in Lake Fuxian. The increasing Tl enrichment has been attributed to anthropogenic activities (e.g., coal burning and non-ferrous metal production), especially since the 1980s. Generally, Be and Tl contamination has decreased over the past several decades, from moderate to low, since the 1980s. The ecological risk of Tl was low, whereas Be might have caused low to moderate ecological risks. In the future, the obtained toxic factors of Be and Tl in this study can be adopted in assessing the ecological risks of them in sediments. Moreover, the framework can be employed for the ecological risk assessment of other newly emerging toxic elements in the aquatic environment.

Potential Ecological Risk Assessment of Critical Raw Materials: Gallium, Gadolinium, and Germanium

In recent years, the demand for critical raw materials such as gallium, gadolinium and germanium (G(s)) has steadily increased in various industries. However, treatment or recycling rates of these elements are extremely low, which can lead to environmental pollution. An assessment of the ecological risks was also not possible until now, as there were no calculated toxicity coefficients for G(s). In this study, a well-known method, the so-called potential ecological risk index (PERI), was used for the first time to calculate the toxicity coefficients of these elements using data from recent literature studies on G(s) elements. The toxicity coefficient of each of the three elements was determined as five (5). The results show that G(s) have the same toxicity coefficient as Cu and Pb and are higher than that of Cr. The ecological risk index results varied from 4 to 414, 0.98 to 25.98 and 2.50 to 284.64 for Ga, Gd and Ge, respectively. The results show that Ga and Ge pose high ecological risk while the Er_i of Gd is low. The toxicity coefficients of these elements have been calculated for the first time in the literature and provide a practical use for calculating the potential ecological risk index.

Ecotoxicological Differences of Antimony (III) and Antimony (V) on Earthworms Eisenia fetida (Savingy)

In this study, we assessed the acute and chronic toxic effects of Sb (III) and Sb (V) on Eisenia fetida (Savingy) (E. fetida) by applying the filter paper contact method, aged soil treatment, and avoidance test experiment. In the acute filter paper contact test, the LC50 values for Sb (III) were 2581 mg/L (24 h), 1427 mg/L (48 h), and 666 mg/L (72 h), which were lower than Sb (V). In the chronic aged soil exposure experiment, when the Sb (III)-contaminated soil was aged 10 d, 30 d, and 60 d after exposure for 7 d, the LC50 value of E. fetida was 370, 613, and >4800 mg/kg, respectively. Compared to Sb (V) spiked soils aged only for 10 d, the concentrations causing 50% mortality significantly increased by 7.17-fold after 14 days of exposure in soil aged for 60 d. The results show that Sb (III) and Sb (V) could cause death and directly affect the avoidance behavior of E. fetida; yet, the toxicity of Sb (III) was higher than that of Sb (V). Consistent with the decrease in water-soluble Sb, the toxicity of Sb to E. fetida was greatly reduced with time. Therefore, in order to avoid overestimating the ecological risk of Sb with varying oxidative states, it is important to consider the forms and bioavailability of Sb. This study accumulated and supplemented the toxicity data, and provided a more comprehensive basis for the ecological risk assessment of Sb.

Geochemical impact of dissolved organic matter on antimony mobilization in shallow groundwater of the Xikuangshan antimony mine, Hunan Province, China

Dissolved organic matter (DOM) is widely used in aquatic systems to control the environmental fate of As. However, similar to the behavior of As, Sb mobilization driven by DOM is poorly understood. A total of 25 samples were collected from shallow groundwater in the Xikuangshan mine to compare the spectroscopic characteristics and chemical properties of DOM between high- and low-Sb groundwater and to determine the roles of DOM in Sb mobility. The concentrations of Sb and DOM varied from 0.003 to 18.402 mg/L (mean: 3.407 mg/L) and 0.38 to 9.90 mg/L (mean: 2.49 mg/L), respectively. The DOM of the D₃x⁴ water was primarily dominated by terrestrial and microbial humic-like and fulvic acid substances, with a relatively small contribution of tryptophan-like components. Complexing agents, competitive adsorption, and photopromoted oxidation under sunlight were considered as the formation mechanisms for DOM-controlled Sb(V)-dominated Sb species in D₃x⁴ water. The weakly alkaline and oxidizing conditions, and the presence of Fe hydroxides facilitated the promotion of Sb(V) concentration. The findings of this study further enhance our understanding of the Sb migration mechanism in oxic groundwater.

Occurrence characteristics of uranium mineral-related substances in various environmental media in China: A critical review

The high demand and extensive exploitation of uranium resources resulted in the ubiquity and high detection levels of uranium mineral-related substances in various environment media in China. The potential adverse effects of uranium mineral-related substances on environment and human health have received extensive attention. Therefore, we reviewed the occurrence and spatial distribution of uranium mineral-related substances in various basins and environmental media in China to obtain an overall understanding. We collected information from over 70 papers reporting the occurrence and distribution of uranium mineral-related substances in multiple environments and 183 articles on the genesis of uranium deposits in China from 2001 to 2021. Then the occurrence of uranium mineral-related substances and corresponding correlation in different basins, environmental media and depth ranges were compared in detail. And this review assessed the uranium mineral-related pollution in China based on various environmental quality standards of China, EPA and WHO, and proposed the priority uranium mineral-related heavy metals and radioactive substances based on cluster analysis. This review showed that there were obvious differences in the occurrence characteristics of various uranium mineral-related substances in different environmental media, especially in the surrounding environment of sandstone type and hard rock type uranium deposits. These results will guide us to tackle the challenge of uranium mineral-related pollution in China. The correlation analysis of uranium mineral-related pollutants in different environmental media and the identification of priority pollutants will also provide instructions for us to control uranium mineral-related pollution. Finally, we put forward a series of urgent and practical suggestions on risk management and control of uranium mining according to the current situation of uranium mining environment in China, which is of guiding significance for the realization of "green uranium mining".

Source apportionment of soil heavy metals with PMF model and Pb isotopes in an intermountain basin of Tianshan Mountains, China

A boom in tourism may lead to the enrichment in heavy metals (HMs) in soils. Contamination with HMs poses a significant threat to the security of the soil environment. In this study, topsoil samples were collected from a tourist area of Sayram Lake, and the concentrations of HMs (Cr, Cu, Ni, Pb, Zn and Cd) were determined. With contamination and eco-risk assessment models, correlation analysis, Pb isotope ratios, redundancy analysis and positive matrix factorization (PMF) model, the risks and sources of HMs in the soil were studied. The I_geo results suggested that Cd was the primary pollutant in the tourist area of Sayram Lake. The potential ecological risk index (PERI) showed that the study area was at low risk, and the pollution load index (PLI) indicated that the study area had a moderate contamination level. Qualitative and quantitative analyses apportioned three sources of HMs, namely, natural sources (38.5%), traffic sources (27.2%) and mixed sources (tourist waste and atmospheric deposition) (34.3%). Redundancy analysis results showed that the HMs content was related to SiO₂, Al₂O₃, TiO₂, P₂O₅, MnO, K₂O, Fe₂O₃ and SOC, and heavy metals tended to be stored in soil particles of grain sizes < 32 µm. These findings are expected to provide useful insights into the source identification of HMs in the soils of mountain tourism areas and provide a scientific decision-making basis for sustainable tourism development and for the assessment of ecological service values in the Tianshan Mountains.

Toxic effects of antimony in plants: Reasons and remediation possibilities-A review and future prospects

Antimony (Sb) is a dangerous heavy metal (HM) that poses a serious threat to the health of plants, animals, and humans. Leaching from mining wastes and weathering of sulfide ores are the major ways of introducing Sb into our soils and aquatic environments. Crops grown on Sb-contaminated soils are a major reason of Sb entry into humans by eating Sb-contaminated foods. Sb toxicity in plants reduces seed germination and root and shoot growth, and causes substantial reduction in plant growth and final productions. Moreover, Sb also induces chlorosis, causes damage to the photosynthetic apparatus, reduces membrane stability and nutrient uptake, and increases oxidative stress by increasing reactive oxygen species, thereby reducing plant growth and development. The threats induced by Sb toxicity and Sb concentration in soils are increasing day by day, which would be a major risk to crop production and human health. Additionally, the lack of appropriate measures regarding the remediation of Sb-contaminated soils will further intensify the current situation. Therefore, future research must be aimed at devising appropriate measures to mitigate the hazardous impacts of Sb toxicity on plants, humans, and the environment and to prevent the entry of Sb into our ecosystem. We have also described the various strategies to remediate Sb-contaminated soils to prevent its entry into the human food chain. Additionally, we also identified the various research gaps that must be addressed in future research programs. We believe that this review will help readers to develop the appropriate measures to minimize the toxic effects of Sb and its entry into our ecosystem. This will ensure the proper food production on Sb-contaminated soils.

Assessing the environmental risk and mobility of cobalt in sediment near nonferrous metal mines with risk assessment indexes and the diffusive gradients in thin films (DGT) technique

The Jialing River is the tributary of the Yangtze River with the largest drainage area. In recent years, the Jialing River has suffered a series of environmental problems, such as discharge of industrial effluent and sand mining activities, which have severely threatened the aquatic ecosystem of the river. In the present study, we employed risk assessment indexes, sequential extraction and the diffusive gradients in thin films (DGT) technique to assess environmental risks and study the remobilization of cobalt (Co) in sediments. The potential ecological risk index and risk assessment code results demonstrated that Co may pose a low environmental and ecological risk to the local aquatic environment. However, BCR sequential extraction showed that the sum of the F1, F2 and F3 fractions of Co still accounted for over 50% of the Co in the study areas, indicating that sediments may be a source of Co release. The DGT results showed an increasing trend for DGT-labile Co in deep sediments (-8 cm to -12 cm), and the calculated flux values ranged from 0.08 to 15.54 ng cm²·day^-1, indicating that Co tends to transfer across the sediment-water interface at all sampling sites. Correlation analysis showed that F1-Co, F2-Co and F3-Co are the fractions readily captured by DGT and can be used for predicting Co remobilization in sediment. Sand mining activities contribute substantially to the release of Co from the F1 and F3 fractions as a result of strong stirring of sediments and introduction of oxygen into the sediments. The reductive dissolution of iron (Fe) and manganese (Mn) hydroxides or oxides causes the release of Co and Fe/Mn in the sediment, which leads to Co release from the reducible fraction. The above work suggests that sand mining in the Jialing River should be reasonably regulated to prohibit illegal sand mining activities.

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.

Pollution and Risk Assessments of Heavy Metal(loid)s in the Soil around Lead-Zinc Smelteries via Data Integration Analysis

Pb-Zn smelting is a major cause of heavy metal(loid) contaminations in soils. We collected data on heavy metal(loid)s in the soils near Pb-Zn smelteries globally from 54 peer-reviewed reports to study the metals' distribution, pollution index, and potential ecological and health risks. We observed that 90% of the studied Pb-Zn smelteries were distributed in Asia and Europe. Heavy metal(loid)s were mainly deposited within a 2 km distance to the smelteries, with mean concentrations (mg/kg) of 208.3 for As, 26.6 for Cd, 191.8 for Cu, 4192.6 for Pb, and 4187.7 for Zn, respectively. Cd and Pb concentrations in the soil exceeded their corresponding upper continental crust values several hundred folds, suggesting severe contamination. The smelting area had the highest heavy metal(loid) contamination in soil, followed by the forest land, farmland, and living area. Compared with the soil environmental standard values from various countries, As, Cd, Pb, and Zn were considered priority pollutants for protecting the ecosystem and human health. Likewise, As, Cd, and Pb were suggested as the priority pollutants for protecting groundwater safety. The potential ecological and health risks of heavy metal(loid)s in the soil within 2 km of Pb-Zn smelteries were severe and should be of concern.

Partitioning behavior and ecological risk of arsenic and antimony in the sediment-porewater profile system in the Three Gorges Reservoir, China

Arsenic and antimony are widely distributed toxic metalloids in aquatic environments. However, their partitioning behaviors in the sediment profile remain not well understood. Here, partitioning behaviors, diffusive fluxes, as well as the ecological risks of As and Sb in the sediment-porewater profile system in the tributaries of the Three Gorges Reservoir (TGR) were investigated. As and Sb showed markedly different spatial variations in the longitudinal profiles of both porewater and sediment samples. Specifically, the concentration of As showed an accumulation trend with depth, while that of Sb showed a relatively complicated trend. Further, As showed lower sediment-porewater partitioning coefficient (K_d) values, suggesting that it had a relatively lower sediment affinity and a higher mobility than Sb. Its residual fraction (30%-60%) was also lower than that of Sb. This phenomenon could be attributed to the chemical fractions of the trace metals and the pH value of the sediments. Furthermore, the K_d values corresponding to As were influenced by both the residual fraction (r = 0.338, p < 0.05) and the exchangeable fraction (r = -0.643, p < 0.01), while those corresponding to Sb were only influenced by pH. Additionally, even though these two trace metals showed low ecological and mobility risks, the diffusive fluxes at the sediment-water interface suggested that the sediment acted as a source of As and a sink for Sb relative to the overlying water. This study indicated that As and Sb had different partitioning behaviors and release risks in the sediment-porewater profile system, enhanced the understanding the transport and fate of As and Sb in the aquatic environment.

Ecological risk assessment of trace elements accumulated in stormwater ponds within industrial areas

Stormwater ponds can provide flood protection and efficiently treat stormwater using sedimentation. As the ponds also host aquatic biota and attract wildlife, there is a growing concern that the sediment bound pollutants negatively affect aquatic organisms and the surrounding ecosystem. In this study, we used three methods to assess the accumulation and the potential ecological risk of 13 different heavy metals and metalloids (e.g. trace elements) including both elements that are frequently monitored and some which are rarely monitored in sediment from 5 stormwater ponds located within catchments with predominately industrial activities. Ecological risk for organisms in the older ponds was observed for both commonly (e.g. Cd, Cu, Zn) and seldom (e.g. Ag, Sb) monitored trace elements. The 3 methods ranked the degree of contamination similarly. We show that methods usually used for sediment quality assessment in aquatic ecosystems can also be used for screening the potential risk of other trace elements in stormwater ponds and may consequently be useful in stormwater monitoring and management. Our study also highlights the importance of establishing background conditions when conducting ecological risk assessment of sediment in stormwater ponds.

Acidity-dependent mobilization of antimony and arsenic in sediments near a mining area

Coexisting antimony (Sb) and arsenic (As) have raised worldwide concerns, but the factors controlling the mobilization of Sb and As in sediments near mining areas are not fully understood. Herein, multiple leaching methods and complementary spectroscopic analyses were used to investigate the mobility of Sb and As and its controlling factors in sediments around the Xikuangshan tailings pond over a wide range of acidity. The general acid neutralizing capacity (GANC) test showed that the leachability of Sb and As exhibited a V-shape pattern with a minimum concentration at 1.6 eq H⁺/kg. The result of MINTEQ simulation agreed well with our GANC results, and demonstrated that the decrease of Sb and As in the range 0-1.6 eq H⁺/kg and the increase in 1.6-4 eq H⁺/kg were mainly controlled by the adsorption and dissolution of iron oxyhydroxide, respectively. Based on the V-shaped leaching trend, Sb and As were predicted to be immobilized in sediments when the acidity accumulated to 1.6 eq H⁺/kg for a long term up to 61 years. This study provides insights in assessing the leaching risks and predicting the mobilization of Sb and As in sediments.

The combination of aerobic digestion and bioleaching for heavy metal removal from excess sludge

In this study, bioleaching is employed for removing heavy metals from excess sludge generated during municipal wastewater treatment. To avoid organic matter impact on bioleaching, aerobic digestion was performed as pretreatment of the bioleaching or accompanied with the bioleaching. The results showed that the leaching amounts of heavy metals from the process of aerobic digestion accompanied with bioleaching was 2.3 times more than that of the process of aerobic digestion followed by bioleaching. The stable-state proportions of Zn, Cu, Ni and Mn increased by 83%, 94%, 96% and 91%, respectively, in the process of aerobic digestion accompanied with bioleaching, and moreover, the reduction rate of MLSS increased by 22.7%. Although the content of ammonia nitrogen and total phosphorus in sludge decreased after bioleaching treatment, they were still much higher than the soil background value. It indicates that the treated sludge still has agricultural value. High throughput sequencing analysis showed that the relative abundance of acid-producing bacteria (Romboutsia, Clostridium, Tricibacter, and Intestinibacter) significantly increased from 0% to 28.6%, 6.9%, 3.9%, and 2.4%. The enrichment of these acidogenic bacteria was the main reason for the pH decrease, which was conducive to the removal of heavy metals from sludge.

Antimony Immobilization in Primary-Explosives-Contaminated Soils by Fe-Al-Based Amendments

Soils at primary explosives sites have been contaminated by high concentrations of antimony (Sb) and co-occurring heavy metals (Cu and Zn), and are largely overlooked and neglected. In this study, we investigated Sb concentrations and species and studied the effect of combined Fe- and Fe-Al-based sorbent application on the mobility of Sb and co-occurring metals. The content of Sb in soil samples varied from 26.7 to 4255.0 mg/kg. In batch experiments, FeSO4 showed ideal Sb sorption (up to 97% sorption with 10% FeSO4·7H2O), whereas the sorptions of 10% Fe0 and 10% goethite were 72% and 41%, respectively. However, Fe-based sorbents enhanced the mobility of co-occurring Cu and Zn to varying levels, especially FeSO4·7H2O. Al(OH)3 was required to prevent Cu and Zn mobilization. In this study, 5% FeSO4·7H2O and 4% Al(OH)3 mixed with soil was the optimal combination to solve this problem, with Sb, Zn, and Cu stabilizations of 94.6%, 74.2%, and 82.2%, respectively. Column tests spiked with 5% FeSO4·7H2O, and 4% Al(OH)3 showed significant Sb (85.85%), Zn (83.9%), and Cu (94.8%) retention. The pH-regulated results indicated that acid conditioning improved Sb retention under alkaline conditions. However, no significant difference was found between the acidification sets and those without pH regulation. The experimental results showed that 5% FeSO4·7H2O + 4% Al(OH)3 without pH regulation was effective for the stabilization of Sb and co-occurring metals in primary explosive soils.

Presence, sources, and risk assessment of heavy metals in the upland soils of northern China using Monte Carlo simulation

The spatial dynamics of heavy metal contamination in the upland soils of northern China are relatively unknown, despite the region's high contribution to the national grain output. In this study, the concentrations of As, Cd, Co, Cr, Cu, Mn, Pb, Sb, Sc, Ti, and Zn and subsequent ecological and human health risks were investigated in three major grain producing areas (Hexi Corridor, L1; Hetao irrigation area, L2; and eastern Inner Mongolia, L3) of northern China. Among the heavy metals, Ti had the highest average concentration of 3.02 g/kg, followed by Mn (470 mg/kg), Cr (56.6 mg/kg), Zn (34.3 mg/kg), Pb (19.4 mg/kg), Cu (17.8 mg/kg), Co (9.66 mg/kg), Sc (7.26 mg/kg), As (5.35 mg/kg), Sb (0.73 mg/kg), and Cd (0.17 mg/kg). Generally, the heavy metal concentrations decreased from west to east (L1 > L2 > L3) across northern China. Moreover, three potential sources of the heavy metal were distinguished, including natural process, anthropogenic activities (industrial development and agricultural cultivation), and atmospheric deposition. Although the contamination of the single metal (including Cd, Cr, Cu, and Pb) was moderate in L1 and L2, the combined contamination was low in the upland soils. It was noted that Cd posed a moderate to considerable ecological risk on the upland soils in northern China. This metal was the most sensitive factor in assessing the combined ecological risk, with a contribution rate of 91.56-94.84%. Considering the ingestion exposure, the current concentrations of the metals posed minimal risks to human health. Furthermore, children experienced higher health risks than adults. Present study analyzed the probabilistic distribution of contamination, ecological, and health risk of heavy metals in upland soils of northern China, providing fundamental information for better agricultural heavy metal pollution assessment in China.

Environmental challenges related to cyanidation in Central American gold mining; the Remance mine (Panama)

Mine tailings are a potential source of environmental pollution because they typically contain potentially toxic elements (PTEs) and the residue of chemical compounds used during extraction processes. The Remance gold mine (NW Panama) is a decommissioned mine with mining activity records dating from the 1800s and several periods of abandonment. Very little remediation work has been performed, and waste is exposed to climatic conditions. This study aimed to evaluate the PTEs and cyanide contents in mine waste after mining operations ceased some 20 years ago, and to evaluate the degree of pollution and the environmental risks they pose with the use of the Pollution Load Index (PLI) and the Ecological Risk Index (RI). Although the total cyanide (T-CN) concentration (1.4-1.9 mg kg^-1) found in most of the study area falls within the limits of gold mining tailing values for American sites (1.5-23 mg kg^-1), it is worth noting that the values of the tailings of the last used mining operation exceed it (25.2-518 mg kg^-1) and persist at the site. The PLI and RI suggest that the tailings from the mine and mine gallery sediments represent a source of pollution for soils and surrounding areas given their high content of PTEs (As, Cu, Sb, Hg) and T-CN, which pose serious ecological risks for biota. Therefore, it is necessary to draw up a remediation plan for this area.

Investigations of Metal Pollution in Road Dust of Steel Industrial Area and Application of Magnetic Separation

Pollution characteristics and ecological risks for metals in non-magnetic and magnetic road dust from steel industrial areas were investigated by applying a magnetic separation method. Metal (except for Al, Li, Ti, As, and Sb) concentrations in the magnetic road dust were 1.2 (Sn) to 7.8 (Fe) times higher than those in the non-magnetic road dust. For the magnetic road dust, the geo-accumulation index revealed a strongly to extremely polluted status for Cr, Zn, Cd, and Sb, a strongly polluted status for Mn, Cu, and Pb, and a moderately to strongly polluted status for Fe, Ni, Mo, and Hg. This result indicates that the dominant metal pollution sources of road dust in industrial areas were the traffic activities of heavy-duty vehicles. The mean content of magnetic particles accounted for 44.7% of the total road dust. The metal loadings in the magnetic road dust were 86% (Fe), 77% (Cr), 67% (Mn), 86% (Ni), 76% (Cu), 72% (Zn), 64% (Mo), and 62% (Cd), respectively. Removal of the magnetic fraction from road dust using magnetic separation techniques not only reduces metal contamination but can also improve effective road cleaning strategies or reduce waste generation.

Antimony contamination and its risk management in complex environmental settings: A review

Antimony (Sb) is introduced into soils, sediments, and aquatic environments from various sources such as weathering of sulfide ores, leaching of mining wastes, and anthropogenic activities. High Sb concentrations are toxic to ecosystems and potentially to public health via the accumulation in food chain. Although Sb is poisonous and carcinogenic to humans, the exact mechanisms causing toxicity still remain unclear. Most studies concerning the remediation of soils and aquatic environments contaminated with Sb have evaluated various amendments that reduce Sb bioavailability and toxicity. However, there is no comprehensive review on the biogeochemistry and transformation of Sb related to its remediation. Therefore, the present review summarizes: (1) the sources of Sb and its geochemical distribution and speciation in soils and aquatic environments, (2) the biogeochemical processes that govern Sb mobilization, bioavailability, toxicity in soils and aquatic environments, and possible threats to human and ecosystem health, and (3) the approaches used to remediate Sb-contaminated soils and water and mitigate potential environmental and health risks. Knowledge gaps and future research needs also are discussed. The review presents up-to-date knowledge about the fate of Sb in soils and aquatic environments and contributes to an important insight into the environmental hazards of Sb. The findings from the review should help to develop innovative and appropriate technologies for controlling Sb bioavailability and toxicity and sustainably managing Sb-polluted soils and water, subsequently minimizing its environmental and human health risks.

Potential Loss of Toxic Elements from Slope Arable Soil Erosion into Watershed in Southwest China: Effect of Spatial Distribution and Land-Uses

The watershed-scale distribution and loss of potentially toxic elements (PTEs) through soil erosion from slope lands to a watershed has not yet been systematically studied, especially in small mountain watersheds with high geological background PTEs in Southwest China. In this study, the spatial distribution, loss intensities and ecological risks of 12 PTEs were investigated in 101 soil samples from four types of land use in a typical watershed, Guizhou Province. Moreover, in order to avoid over- or underestimation of the contamination level in such specific geologies with significant variability in natural PTE distribution, the local background values (local BVs) were calculated by statistical methods. The dry arable land had the highest loss intensity of PTEs and was the largest contributor of PTEs (more than 80%) in the watershed, even though it covers a much smaller area compared to the forest land. The loss of Cd, As, Sb, and Hg from slope arable lands into the watershed leads to a relatively high potential ecological risk. The study suggested that both PTEs content with different types of land-uses and intensities of soil loss are of great importance for PTEs’ risk assessment in the small watershed within a high geological background region. Furthermore, in order to reduce the loss of PTEs in soil, the management of agricultural activities in arable land, especially the slope arable land, is necessary.

Risk assessment and management of PM2.5-bound heavy metals in the urban area of Kitakyushu, Japan

The sampling campaign of PM_2.5 was carried out in Kitakyushu City on the western edge of Japan from 2013 to 2019, and 29 heavy metals loaded in PM_2.5 were measured in this study. During the whole sampling period, the PM_2.5 mass concentration ranged from 6.3 μg·m^-3 to 57.5 μg·m^-3, with a median value of 21.3 μg·m^-3, and the sum concentration of heavy metals only accounted for 3%. According to the enrichment factor (EF) and geo-accumulation index (Igeo) analysis, it can be known that Se, Mo, Pb, As, Zn, W, Sb, Cu, V, Cr, Ni, and Cs were mainly from anthropogenic sources, which had EF values larger than 10 and Igeo values larger than 0. The comprehensive ecological risk index for these 12 anthropogenic metals was far greater than 600. This large index showed severe metal pollution and very high ecological risk in the urban area of Kitakyushu, Japan, which should be paid great attention. The human health assessment result further revealed that children living at the sampling site faced severe non-carcinogenic risk (HI = 7.8) and moderate carcinogenic risk (CR = 1.2 × 10^-4), and oral ingestion was basically the most important exposure pathway, followed by dermal contact and inhalation. The priority control metals included Mo, Se, As, Pb, Sb, and Cr; moreover, the concentration-weighted trajectory analysis (CWT) indicated that Mo, Sb, and Cr were from ship emissions because some shipping routes around the Kyushu area were identified as their potential pollution source regions, while Se, As, and Pb were carried by the air masses from the Asian landmass. Overall, although the PM_2.5 concentration in the urban area of Kitakyushu, Japan was not high, the heavy metal risk cannot be overlooked; it is necessary to strengthen the source control of high-risk metals and raise public protection awareness.

Ecological and probabilistic human health risk assessment of heavy metal(loid)s in river sediments affected by mining activities in Ecuador

Gold mining is a significant source of metal(loid)s released into the environment. It is an issue of concern due to the potential adverse health effects associated with exposure to toxic elements. This study aimed to assess the ecological and human health risk caused by heavy metal(loid)s exposure in river sediments in Ponce Enríquez, one of the most important mining sites in Ecuador. Concentrations of As, Cd, Cu, Pb, and Zn were evaluated in 172 sediment samples to determine the Potential ecological risk (R_I) and the carcinogenic (CR) and non-carcinogenic risk (HQ). The human exposure to polluted sediments during recreational activities was computed using Bayesian probabilistic models. Residents were randomly surveyed to adjust the risk models to the specific population data. More than 68% of the sampling stations pose a severe As and Cd ecological risk index ([Formula: see text] > 320). Likewise, residents exposed to river sediments showed a non-acceptable carcinogenic risk by incidental ingestion, being As the primary contributor to overall cancer in both children and adults receptors. Moreover, non-carcinogenic risk through the incidental ingestion of sediments was above the safe limit for children. This is the first study conducted in a mining region in Ecuador that reveals the severe levels of ecological and human health risk to which the population is exposed. These results can be applied as a baseline to develop public health strategies to monitor and reduce the health hazards of the residents of mining communities.

Characteristics of Potentially Toxic Elements, Risk Assessments, and Isotopic Compositions (Cu-Zn-Pb) in the PM10 Fraction of Road Dust in Busan, South Korea

The pollution status of ten potentially toxic elements (PTEs), isotopic compositions (Cu, Zn, Pb), and the potential ecological risk posed by them were investigated in the PM10 fraction of road dust in Busan Metropolitan city, South Korea. Enrichment factors revealed extremely to strongly polluted levels of Sb, Cd, Zn, Pb, and Cu in the PM10 fraction of road dust, with Sb levels being the highest. Statistical analyses showed that the major cause for contamination with PTEs was non-exhaust traffic emissions such as tire and brake wear. Cu and Zn isotopic compositions of road dust were related to traffic-related emission sources such as brake and tires. Pb isotopic compositions were close to that of road paint, indicating that Pb was a different source from Cu and Zn in this study. No significant health risk was posed by the PTEs. Taking into account the total length of road in Busan, a high quantity of PTEs in road dust (PM10) can have serious deleterious effects on the atmospheric environment and ecosystems. The results of metal concentrations and isotopic compositions in road dust will help identify and manage atmospheric fine particle and coastal metal contamination derived from fine road dust.

Ecological and Health Risk Assessments of an Abandoned Gold Mine (Remance, Panama): Complex Scenarios Need a Combination of Indices

The derelict Remance gold mine is a possible source of pollution with potentially toxic elements (PTEs). In the study area, diverse mine waste has been left behind and exposed to weather conditions, and poses risks for soil, plants and water bodies, and also for the health of local inhabitants. This study sought to perform an ecological and health risk assessment of derelict gold mining areas with incomplete remediation, including: (i) characterizing the geochemical distribution of PTEs; (ii) assessing ecological risk by estimating the pollution load index (PLI) and potential ecological risk index (RI); (iii) assessing soil health by dehydrogenase activity; and iv) establishing non-carcinogenic (HI) and carcinogenic risks (CR) for local inhabitants. Soil health seems to depend on not only PTE concentrations, but also on organic matter (OM). Both indexes (PLI and RI) ranged from high to extreme near mining and waste accumulation sites. As indicated by both the HI and CR results, the mining area poses a health risk for local inhabitants and particularly for children. For this reason, it will be necessary to set up environmental management programs in the areas that are most affected (tailings and surrounding areas) and accordingly establish the best remediation strategies to minimize risks for the local population.

Implications of Soil Potentially Toxic Elements Contamination, Distribution and Health Risk at Hunan’s Xikuangshan Mine

A field survey was conducted to determine the pollution grade, sources, potential ecological risk, and health risk of soil potentially toxic elements (PTEs) in Xikuangshan Mine (XKS), the largest antimony (Sb) deposit in the world. A total of 106 topsoil samples were collected from 6 sites in XKS to measure the concentrations of PTEs Cr, Zn, Cd, Pb, As, Hg, and Sb. The results show that the average concentrations of these elements at all six sites were generally greater than their corresponding background values in Hunan province, especially Sb, Hg, and As. Correlation and principal component analyses suggested that Cd, Zn, Pb, Hg, and Sb were primarily released from mining and other industrial and human activities, while Cr and As were mainly impacted by the parent material from pedogenesis. A risk index analysis showed that, overall, sites were at very high ecological risk, and Sb is the highest ecological risk factor, followed by Cd and Hg. According to health risk assessment, oral ingestion is the main non-carcinogenic and carcinogenic risk exposure route. The higher potentially non-carcinogenic and carcinogenic risks happen to the local children who live in the vicinity of mining area. It revealed that the mining and smelting processes of XKS have negatively influenced the local people, therefore, we should pay increasing attention to this practical issue and take effective measures to protect the ecology of XKS.

Ecological risk and source analysis of soil heavy metals pollution in the river irrigation area from Baoji, China

Due to various human activities, soil quality under different land use patterns is deteriorating all over the world. This deterioration is very complex in the river irrigation area and is caused by multi-point and non-point source pollution and seasonal variation. Therefore, the characteristics and sources of soil metal pollution in river irrigation area of Baoji city were analyzed. The contents of 8 metals were given by ICP-MS, in the soil samples. Statistical methods, geo-accumulation index (I_geo) and potential ecological risk index (RI) were conducted to evaluate the spatial distribution features, sources and ecological risks of metal contamination from the study area soil. Principal component analysis and cluster analysis were used to analyze the pollution sources of metal. The analysis showed that Cd is the most polluted, and human activities represented a great impact on the contents of Zn, Ni, Cu and Cd in soil, Cd post moderate-strong pollution and strong risk, Cd has a maximum Igeo value of 3.17. All rivers were at risk of moderate pollution levels in study. Among them, some rivers had even reached strong pollution level. Pollution caused by human activities was the most significant pollution source of metal in the research area soil.

Metals pollution from textile production wastewater in Chinese southeastern coastal area: occurrence, source identification, and associated risk assessment

The metals used in textile wet processing are of significant concern for the environment and human health. However, our understanding of metals released by the Chinese textile industry and their potential risks to ecology is limited. This work quantified the concentrations of seven metals in 199 wastewater samples from 77 textile enterprises in the southeastern coastal area of China. In the water discharged after end-of-pipe treatment, the mean concentrations of Sb, Hg, Fe, Mn, Zn, Cr, and As were 0.289, 0.009, 0.579, 0.277, 0.035, 0.016, and 0.013 mg/L, respectively. Alkali deweighting effluents, dyeing effluents, and influents into regulation tanks were observed to be "hotspots" for metal distributions. Among the seven target metals, only Sb was found to be significantly correlated with COD, NH₃-N, TN, and TP. The results of one-way ANOVA suggested that the Sb mainly came from the processing of polyester fibers. Overall, the majority of discharged wastewater samples were at safe levels, according to six health indicators. Sb posed elevated risks in comparison to other elements, which necessitated further concern. The findings can help decision-makers prevent hazardous metal contamination in the textile and dyeing industry, and provide a basis for the further study of the mechanisms of metal migration in the environment.