Heavy metals and metalloids in the surface sediments of the Xiangjiang River, Hunan, China: distribution, contamination, and ecological risk assessment

Water contamination: A culprit of serum heavy metals concentration, oxidative stress and health risk among residents of a Nigerian crude oil-producing community

Niger Delta has become popular for crude oil extraction for the past few decades. This uncoordinated activity has made it a hotspot for xenobiotics exposure and water bodies remain the environmental matrix significantly affected. One of the most deleterious components of crude oil is heavy metals (HMs). This study investigates HMs concentration in water and serum of humans residing in an oil-host community with the consideration of systemic effects, pollution status, carcinogenic and non-carcinogenic health risks and comparison made with residents from a non-oil-producing community. Heavy metal analysis, serum electrolytes, Urea, Creatinine, and liver enzymes were assessed using standard procedures; malondialdehyde, catalase, SOD, glutathione reductase, GPx and total antioxidant capacity (TAC) by spectrophotometry and TNF-α and 8-OHdG assessed via ELISA method. We found altered serum electrolytes; increased serum Pb and Cd levels; increased AST, ALT, ALP and lipid peroxidation; and decreased enzymes antioxidants including TAC among Ugbegugun community residents compared with control. We observed an association between environmental crude oil contamination, ecological and health risks in the community. We concluded that protracted exposure to HMs induces multi-systemic toxicities characterized by DNA damage, depletion of the antioxidant system, and increased free radical generation culminating lipo-peroxidation with significant ecological, carcinogenic, and non-carcinogenic risks characterize crude oil water contamination.

Systematic literature review of heavy metal contamination of the Nigerian environment from e-waste management: Associated health and carcinogenic risk assessment

E-waste -the aftermath of large amount of electrical and electronic equipment ferried into Africa from which Nigeria receives a significant chunk, is composed of components known to be hazardous to health. Composition of series of heavy metals (HMs) in e-waste is traceable to many health conditions including cancer which is hitherto incompletely understood. This study harmonizes primary data on HMs from e-waste in different Nigerian environmental media including the air, soil, surface dust, water and plant. We estimated the possible health implications, single and aggregative soil and water pollution indices both in adult and children categories, carcinogenic and non-carcinogenic risks secondary to HM exposure and mapped out the possible mechanism of carcinogenesis. Analysis showed that soil, water, surface dust and plant matrices in Nigerian environment are variedly but considerably contaminated with combination of HMs. The significantly high values of the hazard quotient and hazard index of both water and surface dust matrices are indicative of adverse health effect of the non-carcinogenic risk. The highest HQ is generated by Pb and Cr through dermal exposure to soil and surface dust with mean values of 1718.48, 1146.14, 1362.10 and 1794.61 respectively among Nigerian children followed by the oral exposure. This pattern of observation is similar to that obtained for adult category. HI due to Pb and Cr in soil constitutes the highest HI (2.05E+03 and 1.18E+03 respectively) followed by surface dust. However, this study precipitates the observation that children are more at health risk than adults in contaminated environment. Carcinogenic risk also follows the same pattern of expression in the Nigerian environment. We conclude that exposure to e-waste poses significant carcinogenic and non-carcinogenic health risks and the induction of toxicity may be mediated via DNA damage, oxidative stress and inflammatory/immune cells dysfunction in Nigerian environment.

The effects of different electrode materials on the electric field-assisted co-composting system for the soil remediation of heavy metal pollution

The electric field-assisted composting system (EACS) is an emerging technology that can enhance composting efficiency, but little attention has been given to electrode materials. Herein, an EACS was established to investigate the effects of electrode materials on humic substance formation and heavy metal speciation. Excitation-emission matrix analysis showed that carbon-felt and stainless-steel electrodes increased humic acid (HA) by 48.57 % and 47.53 %, respectively. In the EACS with the carbon-felt electrode, the bioavailability factors (BF) of Cu and Cr decreased by 18.00 % and 7.61 %, respectively. Despite that the stainless-steel electrodes decreased the BF of As by 11.26 %, the leaching of Cr, Ni, Cu, and Fe from the electrode itself is an inevitable concern. Microbial community analyses indicated that the electric field increased the abundance of Actinobacteria and stimulated the multiplication of heavy metal-tolerant bacteria. Redundancy analysis indicates that OM, pH, and current significantly affect the evolution of heavy metal speciation in the EACS. This study first evaluated the metal leaching risk of stainless-steel electrode, and confirmed that carbon-felt electrode is environment-friendly material with high performance and low risk in future research with EACS.

Evaluation of pollution levels in sediments from Lake Edku, Egypt using laser ablation inductively coupled plasma mass spectrometry

The concentrations of 11 heavy metals in sediments from Lake Edku, Egypt were determined using LA-ICP-MS. The average concentrations of elements occurred in the order of Fe > V > Cr > Zn > Ni > Cu > Co > Pb > As > Sn > Mo with respective values of 4.67 %, 104.8, 77.9, 76.6, 59.2, 52, 27.8, 19.8, 4.14, 2.24, and 1.45 μg/g. Several pollution indices were used to evaluate individual and cumulative contamination levels. All HMs were found to be in the deficiency to minimal enrichment range based on the enrichment factor. The contamination factor indicated low contamination levels of Cr and As, low to moderate contamination levels of Fe, Ni, Zn, Mo, Sn, and Pb, and moderate contamination levels of Co and Cu. The pollution load index and contamination degree indicated the sediments to be polluted and moderately polluted, respectively.

Unveiling the Rising Threat of Cadmium Pollution and Alarming Health Risks Associated with the Consumption of 15 Commercially Important Fish Species in the Middle Stretch of River Ganga, at Patna, India

Among environmental contaminants, the rising level of cadmium in freshwater ecosystems is one of the most significant global concerns. The study addresses the current pollution status of cadmium in the middle stretch of River Ganga and explores the potential hazard associated with the consumption of 15 commercially important fish species by the inhabitants. Together 72 water and sediment samples were analyzed from the four representative sampling sites of River Ganga after the surveillance of major anthropogenic stressors. The concentration of cadmium ranges from 0.003 to 0.011 mg/l and 0.2 to 3.48 mg/kg in water and sediment respectively in 2022. The average concentration of cadmium was recorded to be the highest in Channa punctatus (1.35 mg/kg), followed by Rita rita = Johnius coitor (1.15 mg/kg), and the lowest in Labeo bata (0.2 mg/kg). The finding highlights greater exposure duration and feeding preferences of fish species have played a significant role in the bioaccumulation of the metal in the riverine system. Notably, the domestic effluents, agricultural runoffs, and pollutants brought along by the tributaries of River Ganga are identified as the main anthropogenic stressors for the moderate to considerably polluted status of the River Ganga. The target hazard quotient (THQ) and target carcinogenic risk (TCR) have revealed a higher susceptibility to cadmium contamination in children followed by females, and males. In addition, hierarchical cluster analysis (HCA) has noted intake of Rita rita, Channa punctata, Puntius sophore, and Johnius coitor could be more detrimental to children's health than adults.

Accelerated export and transportation of heavy metals in watersheds under high geological backgrounds

The geological background level of metals plays a major role in mineral distribution and watershed diffuse heavy metal (HM) pollution. In this study, field research and a distributed hydrological model were used to analyze the distribution, sources, and pollution risk of watershed HMs in sediments with high geological HM backgrounds. Study showed that the mineral distribution and landcover promoted the transport differences of watershed HMs from upstream to the estuary. And the main sources of Co, Ni, and V in the estuarine sediments were natural sources. Sources of Pb and Zn were dominated by anthropogenic sources, accounting for 76% and 64% of their respective totals. The overall ecological risk of anthropogenically sourced HMs was dominated by Pb (46.6%), while the contributions of Co and Ni were also relatively high, accounting for 35.70% and 33.40%. Moreover, redundancy analysis showed that HM variations in the sediments were most sensitive to soil erosion and mineralizing rock distribution. The spatial patterns of watershed HMs from natural sources were significantly influenced by P loading, precipitation, and forest distribution. This combination of experiments and model improves the understanding of watershed HM variation and provides a new perspective for formulating effective watershed HM management strategies.

Health risk assessment of heavy metals in wild fish and seasonal variation and source identification of heavy metals in sediments: a case study of typical urban river in Xi'an, China

In order to determine the status of heavy metal pollution in river sediments and wild fish in Xi'an, concentrations of heavy metals (Cr, Ni, Cu, Zn, As, and Pb) were collected and analyzed in sediments and wild fish during dry season (October-November 2020) and wet season (June-July 2021). This study aimed to investigate the spatial and temporal variations of heavy metals in urban rivers of Xi'an, China. Their distribution characteristics and sources as well their pollution levels and health risks were assessed. The findings revealed that influenced by human activities, the heavy metal content in sediments (mg·kg-1 dry weight) in wet season was ranked as follows: Cr (73.09) > Zn (63.73) > Pb (40.31) > Ni (31.52) > Cu (24.86) > As (6.83); in the dry season: Zn (94.07) > Cr (69.59) > Cu (34.24) > Ni (33.60) > Pb (32.87) > As (7.60). Moreover, 32 fish samples from six species indicated an average metal content trend (mg·kg-1 wet weight) of Zn (8.70) > Cr (0.57) > Pb (0.28) > Ni (0.27) > Cu (0.24) > As (0.05). The potential ecological risk indices for sediment heavy metal concentrations in both seasons were well below the thresholds, which indicates that the aquatic environment is in safe level. The analysis of the potential ecological risk of sediment heavy metal concentrations indicates that the aquatic environment is safe for the time being. Based on the estimated daily intake (EDI), target risk quotient (THQ), total target risk quotient (TTHQ), cancer risk (CR), total cancer risk (TCR), and the permissible safety limits set by the agencies, the consumption of the fish examined is safe for human health. However, the presence of Cr and As in wild fish should still be a concern for human health, especially for children. The cumulative effect of heavy metals and the bioconcentration factor (BCF) suggest that sediment and heavy metals in fish are closely related, with higher concentrations in fish living in the bottom layer of the water column than in other water layers, and increasing with increasing predator levels. Correlation analysis and PMF modeling identified and determined four comparable categories of potential sources, namely, (1) atmospheric deposition and traffic sources, (2) agricultural sources, (3) industrial sources, and (4) natural sources.

Distribution, source and contamination of rare earth elements in sediments from lower reaches of the Xiangjiang River, China

Rare earth elements (REEs) are emerging micropollutants in aquatic environments. In this study, concentrations of REEs and major elements, and mineralogical compositions of sediments from lower reaches of the Xiangjiang River (China) were analyzed using ICP-MS technique. The results suggested that sediments were characterized by terrigenous compositions TiO2, SiO2, Al2O3, K2O, Na2O and P2O, and contained high concentrations of REEs with mean total REE concentrations (∑REE) of 318.7 mg/kg. REEs were moderately enriched in upper river sediments, and slightly or less enriched in downriver sediments. The normalized REE distribution pattern for sediments was characterized by flat shalelike and Eu depleted V-shape REE patterns, which indicated REEs in sediments were lithologically contributed from sedimentary rocks and granites distributed in the watershed respectively. REEs in sediments were hosted mainly in Fe-Mn oxides, and sulfide and organic matters that were characterized by middle REEs (MREE) enrichments relative to light REEs (LREE) and heavy REEs (HREE), and the distribution and differentiation of REEs in sediments were controlled by clays, Fe-Mn oxides, organic matters and finer grains; and also by accessory minerals (e.g., zircon) from granite. The distribution features of REEs in sediments and BCR extraction results suggested that the sediment REE enrichment resulted from additional REE input from anthropogenic sources, including those in discharges from sulfide-ore smelting industries at Zhuzhou city and from phosphate fertilizer plants at Xiangtan city along the river. Thus, sediments were contaminated with REEs in moderate degree in upper river area, and REE contamination was then formed by superimposing anthropogenic REEs on lithological residues. Finally, concentrations of Ce > 100 mg/kg, Gd > 8.12 mg/kg, ∑REE >274.9 mg/kg, ∑LREE >252.3 mg/kg and ∑HREE >28.8 mg/kg here were recommended as the REE contamination levels that represented as REE indices for identifying and rating REE contamination in this mining impacted river.

Microstructural Characterization and Prior Particle Boundary (PPB) of PM Nickel-Based Superalloys by Spark Plasma Sintering (SPS)

This research investigates the microstructure and defects of powder metallurgy (PM) nickel-based superalloys prepared by spark plasma sintering (SPS). The densification, microstructural evolution, and precipitate phase evolution processes of FGH96 superalloy after powder heat treatment (PHT) and sintering via SPS are specifically analyzed. Experimental results demonstrate that SPS technology, when applied to sinter at the sub-solidus temperature of the γ' phase, effectively mitigates the formation of a prior particle boundary (PPB). Based on experimental and computational findings, it has been determined that the presence of elemental segregation and Al₂O₃ oxides on the surface of pre-alloyed powders leads to the preferential precipitation of MC-type carbides and Al₂O₃ and ZrO₂ oxides in the sintering necks during the hot consolidation process, resulting in the formation of PPB. This study contributes to the understanding of microstructural modifications achieved through SPS technology, providing crucial information for optimizing sintering conditions and reducing the widespread occurrence of PPB, ultimately enhancing the material performance of PM nickel-based superalloys.

Assessment of potential ecological risk based on the vertical characteristics of potential toxic elements in sediments from a high-density cage culture reservoir in China

The pollution of sediments around Lu Ban Island is a serious environmental issue that is threatening human health. The concentration of As, Cd, Cu, Cr, Hg, Ni, Pb, and Zn at 73 layer points were investigated, vertical distribution characteristics, correlation among potential toxic elements and potential ecological risks of sediments at different depth were analyzed. The following results were obtained, (1) the hypothesis that there was a linear relationship between concentration of potential toxic elements and the reciprocal of deep was reasonable. Based on hypothesis, the ultimate value of concentration by making depth go to infinity was regarded as the background concentration. The background concentration of As, Cd, Cu, Cr, Hg, Ni, Pb, and Zn are respectively 4.94 mg/kg, 0.20 mg/kg, 15.48 mg/kg, 58.41 mg/kg, 0.062 mg/kg, 26.96 mg/kg, 20.29 mg/kg, and 53.31 mg/kg. (2) But correlation between Ni and As was relatively weak, high degree of correlation among other potential toxic elements were found. Based on their correlation, eight potential toxic elements were classified into three groups. First group included Ni and Cr, mainly releasing by coal burning; Cu, Pb, Zn, Hg, and Cd were grouped together, possibly due to their shared source of fish cage culture; Arsenic with relatively weak correlation with other potential toxic elements was classified as a separate class, which was usually one important mineral resource associated with phosphate. (3) Potential ecological risk index (PERI) of sediment above - 0.40 m belonged to moderate risk, the PERI of sediment in - 0.10 m, - 0.20 m, and - 0.40 m were 289.06, 254.33, and 201.44, respectively. Sediment below - 0.40 m belonged to low risk with average PERI value 112.82, with no significant changes in PERI values. The order of contribution to PERI was Hg > Cd > As > Cu > Pb > Ni > Cr > Zn. (4) According to result of cluster analysis and potential ecological risk, the potential ecological risk of sediment above - 0.40 m mainly contributed by potential toxic elements of Cu, Cd, Hg, Pb, and Zn sharing source of fish cage culture.

Magnetic susceptibility and heavy metal contents in sediments of Riam Kiwa, Riam Kanan and Martapura rivers, Kalimantan Selatan province, Indonesia

Kalimantan Selatan is proud of the Martapura River's natural and cultural history. Martapura tributaries include Riam Kanan and Kiwa. The Martapura River is essential because it provides clean water and a livelihood for riverside residents. Human-caused river pollution grows with population density (also known as anthropogenic pollutants). This study characterizes surface sediment magnetic characteristics and heavy metal contents along the Riam Kanan, Riam Kiwa, and Martapura rivers. The purpose of this research is to evaluate the magnetic signal with respect to heavy metal contents found in surface sediments taken from rivers and to confirm the use of the rock magnetism method in environmental studies in the study area. Surface sediment samples were gathered and tested for magnetic, heavy metal, and mineralogical content. According to the findings, the pseudo-single domain (PSD) magnetite mineral predominates among the magnetic minerals that can be found in the surface sediments of the rivers Riam Kanan, Riam Kiwa, and Martapura. This substantially greater grain size may be due to magnetic particles produced by erosion along the river banks. The mass-specific magnetic susceptibility of surface sediments ranges from 103.11 to 1403.64 × 10^-8 m³/kg, with an average value of 355.67 × 10^-8 m³/kg due to the peatland environment. Magnetic susceptibility strongly negatively correlates with heavy contents like Cu, Zn, and Hg, according to Pearson correlation analysis. Due to this correlation, magnetic susceptibility may indicate heavy metal pollution in certain rivers. This current study demonstrates the novelty of the relationship between magnetic susceptibility and the contents of heavy metals in surface sediments from rivers in peatland and tropical environments by illustrating how the relationship affects the magnetic susceptibility of the sediments.

Integrated assessment of land-to-river Cd fluxes and riverine Cd loads using SWAT-HM to guide management strategies

In 2011, China invested US$9.8 billion to combat the severe heavy metal pollution in the Xiang River basin (XRB), aiming to reduce 50% of the 2008 industrial metal emissions by 2015. However, river pollution mitigation requires a holistic accounting of both point and diffuse sources, yet the detailed land-to-river metal fluxes in the XRB remain unclear. Here, by combining emissions inventories with the SWAT-HM model, we quantified the land-to-river cadmium (Cd) fluxes and riverine Cd loads across the XRB from 2000 to 2015. The model was validated against long-term historical observations of monthly streamflow and sediment load and Cd concentrations at 42, 11, and 10 gauges, respectively. The analysis of the simulation results showed that the soil erosion flux dominated the Cd exports (23.56-80.14 Mg yr^-1). The industrial point flux decreased by 85.5% from 20.84 Mg in 2000 to 3.02 Mg in 2015. Of all the Cd inputs, approximately 54.9% (37.40 Mg yr^-1) was finally drained into Dongting Lake; the remaining 45.1% (30.79 Mg yr^-1) was deposited within the XRB, increasing the Cd concentration in riverbed sediment. Furthermore, in XRB's 5-order river network, the Cd concentrations in small streams (1st order and 2nd order) showed larger variability due to their low dilution capacity and intense Cd inputs. Our findings highlight the need for multi-path transport modeling to guide future management strategies and better monitoring schemes to restore the small polluted streams.

Ecological risk assessment and identification of the distinct microbial groups in heavy metal-polluted river sediments

To assess the health of river ecosystems, it is essential to quantify the ecological risk of heavy metals in river sediments and the structure of microbial communities. As important tributaries of the Tuo River in the upper reaches of the Yangtze River, the Mianyuan River and the Shiting River, are closely related to the economic development and human daily life in the region. This study assessed the ecological risks of heavy-metal-polluted river sediments, the heavy-metal-driven bacterial communities were revealed, and the relationships between the ecological risks and the identical bacterial communities were discussed. The Cd content was significantly greater than the environmental background value, leading to a serious pollution and very high ecological risk at the confluence of the two rivers and the upper reaches of the Mianyuan River. Microbial community analysis showed that Rhodobacter, Nocardioides, Sphingomonas, and Pseudarthrobacter were the dominant bacterial genera in the sediments of the Shiting River. However, the dominant bacterial genera in the Mianyuan River were Kouleothrix, Dechloromonas, Gaiella, Pedomicrobium, and Hyphomicrobium. Mantel test results showed (r = 0.5977, P = 0.005) that the Cd, As, Zn, Pb, Cr, and Cu were important factors that influenced differences in the distribution of sediment bacterial communities Mianyuan and Shiting rivers. A correlation heatmap showed that heavy metals were negatively correlated for most bacterial communities, but some bacterial communities were tolerant and showed a positive correlation. Overall, the microbial structure of the river sediments showed a diverse spatial distribution due to the influence of heavy metals. The results will improve the understanding of rivers contaminated by heavy metals and provide theoretical support for conservation and in situ ecological restoration of river ecosystems.

Metal-mining-induced sediment pollution presents a potential ecological risk and threat to human health across China: A meta-analysis

Aquatic sediment polluted by potentially toxic elements (PTEs) from mining activities represents a potential health "time bomb" for humans and the local ecology, but the integrated analysis of pollution and hazards of PTEs in sediment around typical metal mines in China is limited. Presently, the associated pollution status, spatial distribution, and ecological and health hazards of Cd, Cu, Zn, Pb, Cr, and As were investigated through index evaluation, spatial analysis, health risk assessment models, and Monte Carlo simulation. Overall, the sediment exhibited varying degrees of PTE contamination; notably, the level of Cd was 104.85 times higher than its background value, and it became the most enriched element in the surveyed sediment, followed in descending order by Cu, As, Zn, Pb, and Cr. Nationally, over 64.5% of metal-mining-affected sediment presented a very high ecological risk, contributed mostly by Cd (43.2%-98.7%) followed by As, Pb, and Cu; the risk contributed by both Cr and Zn was found to be negligible. The adverse health risk posed to children by most sediment was 1.72 and 6.46 times higher than that posed to adults for cancerous and noncancerous risks, respectively. The potential noncarcinogenic risks were mainly caused by As, which contributed over 78.9% of the Hazard Index values, then followed by Pb (>9.3%). For both children and adults, the carcinogenic risk of PTEs decreased in the following order: As > Cd > Cr > Pb. The investigated sediment was found seriously affected by nearby metal mines, especially those in regions with long-term and large-scale nonferrous-metal-mining activities. This study could provide a reference for policymakers to develop control strategies for PTE pollution in sediment around mining areas.

Assessment of heavy metal accumulation in Penaeus monodon and its human health implications

Asian tiger shrimp Penaeus monodon (P. monodon) of Chilika lagoon, India was studied regarding the metal accumulation and its associated human health risks. It showed a tendency of metal accumulation in the following order: Zn > Ni > Cu > Co > Cr > Pb > Cd. A two-way ANOVA indicated the metal accumulation was insignificant with respect to season (n = 421, p = 0.59) and sector (n = 32, p = 0.61). The estimated daily intake (EDI), targeted hazard quotient (THQ) and hazard index (HI), and carcinogenic risks (CR) revealed no potential human health risks and were safe for consumption. The pollution load index (PLI) of <1, Geo-accumulation index (Igeo,) and contamination factor (CF) indicated that the study area was unpolluted. This pioneering study highlighted that P. monodon was nurtured well in the healthy habitat of Chilika lagoon and the fair level of metal content made it an excellent source of dietary components.

Effect of incubation time of three single extraction procedures on trace element extraction from sediment and soil

The use of standard single-extraction procedures to evaluate the mobility and availability of trace elements is a common practice in most laboratories dealing with soil or sediment analysis. Most standard single-extraction procedures describe incubations last for 2 h. However, these were tested and validated for soil analysis. Applying them for sediment analysis without further investigation might be misleading and should be reviewed with care. This paper investigates the effect of incubation time on the extraction efficiency of three standard single-extracting reagents (0.01 M CaCl₂, 1 M NH₄NO₃, and 0.05 M EDTA). Incubation experiments with sediment and soil samples lasting for 2 h, 10 h, and 10 d were performed. The results indicated that 2 h appears sufficient to reach equilibrium using CaCl₂ or NH₄NO₃ for soil analysis; but when analyzing sediments, incubation for 10 d resulted in higher concentrations. Incubation experiments with 0.05 M EDTA showed that incubation for 2 h was enough to extract Cd from the soil sample, Mn and to a lesser extent Cd from the sediment samples; while for the other elements, incubation for 10 d yielded higher concentrations for both sample types compared to that obtained after 2 h and 10 h separately. Relative to the pseudo-total metal contents, more than 55% of all studied elements were extracted by using 0.05 M EDTA, indicating high bioavailable metal fraction.

Leaching and characterization studies of heavy metals in contaminated soil using sequenced reagents of oxalic acid, citric acid, and a copolymer of maleic and acrylic acid instead of ethylenediaminetetraacetic acid

In this work, the removal performance of three environmentally friendly reagents, oxalic acid (OA), citric acid (CA), and a copolymer of maleic and acrylic acid (PMAA), on heavy metals in polluted soil was studied at the optimum conditions and compared their sequenced performance. The results showed that the consecutive washing with the individual acids significantly improved the removal percentage of heavy metals in the soil compared to that of EDTA (10.2%, 71.3%, 29.8%, 61.6%, and 52.4% removal for As, Cd, Cu, Pb, and Zn, respectively). The removal of As, Cd, Cu, Pb, and Zn in the sequence of CA-OA was 65.6%, 79%, 59.1%, 64.6%, and 63.5%, respectively. In addition, the organic acids had little influence on the soil physicochemical properties after washing with slight reductions of acidity (pH) and soil organic matter (SOM), which are the major determinants of the usability of washed soils for plant growth. The germination rate of Sorghum bicolor in CA-OA-washed soils reached over 70% on the 7th day. CA-OA-washed soils collectively stand out in using washed soils for plant growth with the following advantages: simultaneous removal of cationic and anionic metals, less harmful impact on soil properties, and successful support for the germination of crops. Based on the findings, we recommend the CA-OA sequence as the best alternative to EDTA with higher metal removal efficiency and germination success.

Biotransformation and detoxification mechanism of inorganic arsenic in a freshwater benthic fish Tachysurus fulvidraco with dietborne exposure

Inorganic arsenic (iAs) is a pervasive environmental toxin, its metabolism and detoxification mechanism in freshwater benthic fish under dietary exposure remain unknown. In this study, dietborne exposure of two iAs (arsenate (AsV) and arsenite (AsIII)) was conducted for yellow catfish (Tachysurus fulvidraco) to investigate the bioaccumulation, biotransformation, and detoxification of iAs in the fish liver. The results showed that As significantly accumulated in both the AsIII and AsV treatments compared to the control, and the final As concentration was comparable for both treatments. The detoxification of iAs in freshwater fish depends on the degree of arsenic methylation and the level of antioxidants. Both reduction processes of AsV to AsIII and oxidation processes of AsIII to AsV were found in AsV and AsIII treatments. The major-low toxicity intermediates, which also are detoxification products in the AsIII treatment, were pentavalent dimethylarsinic acid and arsenobetaine (AsB), and AsB was major-low toxicity intermediate in the AsV treatment. Both antioxidants glutathione and glutathione S-transferase contribute to the detoxification of iAs by scavenging excessive reactive oxygen species and promoting iAs methylation in yellow catfish under iAs exposure.

Heavy metals in Chinese freshwater fish: Levels, regional distribution, sources and health risk assessment

China is a major producer and consumer of freshwater fish, which can provide nutrients to the human body but is also of great concern because of the bioaccumulation and amplification of heavy metals that are directly related to human health. In this paper, we reviewed the accumulation and distribution patterns of lead (Pb), arsenic (As), mercury (Hg), cadmium (Cd), and chromium (Cr) in freshwater fish from 2010 to 2020 in nine basins of China (Yangtze River, Pearl River, Yellow River, Haihe River, Huaihe River, Songhua and Liaohe River, Continental, Southeast, and Southwest basins), assessed the health risks, and compared them with those in Chinese marine fish, international freshwater fish, Chinese wild freshwater fish, and artificially cultured freshwater fish. The results showed that 1) the pollution status of the five heavy metals in freshwater fish from nine basins in China is at an intermediate level internationally; 2) the magnitude of heavy metal concentration in four types of artificially farmed freshwater fish and wild freshwater fish is ranked as follows: rice-farmed fish < cage-farmed fish < pond-farmed fish < lake-farmed fish < wild fish; 3) the noncarcinogenic risk factors for heavy metals in freshwater fish in the nine major basins in China were <1 for adults, but the noncarcinogenic risk factors for heavy metals in freshwater fish in the Yellow River, Yangtze River, Pearl River, Songhua and Liaohe River, and Huaihe River basins were all >1 for children.

Ecotoxicological Assessment of Potentially Toxic Elements (as, Cd, Ni and V) Contamination in the Sediments of Southern Part of Caspian Sea, the Case of Khazar Abad, Mazandaran Province, Iran

In this study, the contamination of arsenic, cadmium, nickel and vanadium in the surface sediments of Khazar Abad, in the southern part of the Caspian Sea was analyzed in 2019 using ecotoxicological indices. The geoaccumulation index (Igeo) values showed that the sediment samples of the study area could be classified as 'unpolluted' to 'strongly polluted', while, the values of toxic units (TUs) with an average value of 0.591 indicated that all samples could be classified as 'at low toxicity level'. Moreover, the ecotoxic risk level (TRI) in the studied sediments was classified at the level of 'no toxic risk' for Cd and 'considerable toxic risk' for As and Ni. On the whole, the results showed that the levels of contamination were higher in the areas where industrial, domestic and agricultural wastewater was discharged (i.e. S4, S7, S10, S11 and S12). Finally, to avoid and/or reduce ecotoxicological dangers, periodic monitoring of PTEs in the coastal strip of the southern part of the Caspian Sea is recommended.

Distribution, risk assessment, and source identification of trace metal pollution along the Babolsar coastal area, Caspian Sea

The Caspian Sea is exposed to numerous anthropogenic activities such as untreated wastewater discharge and agricultural activities which increased trace metals contamination. The current study was employed to assess the distribution, ecological risk assessment, and source identification of some trace metals in 125 samples of surface sediments and soil from 6 distinctive sections of Babolsar in the coastal line of the Caspian Sea. The sediment quality guidelines (SQGs) and individual risk assessment indices including enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (Cf), and potential risk factor (Er) suggested a hazardous level of Cd and Cr contamination. There was a relatively high level of Pb contamination while other studied trace metals were at a low contamination level. Cumulative risk indices such as modified degree of contamination (mCD), pollution load index (PLI), and the potential ecological risk index (RI) identified that the river, wetland, and farmland sites were more contaminated compared to the Caspian Sea samples which exhibited a moderate level of contamination. The lowest level of contamination was recorded in the coastline and river delta sites. Two analytical methods including Pearson's correlation coefficient and multivariate clustering dendrogram were also applied to identify the potential sources of contamination. The results suggested that wastewaters, nitrogen, and phosphate fertilizers were the main anthropogenic source of Cd, Co, Pb, and Ni while fossil fuels and transportation activities were the predominant sources of anthropogenic Cu, V, and Zn contamination. Further studies about trace metals risk assessment and fractionation could contribute to more effective decisions for reducing the anthropogenic trace metal pollution in the Caspian Sea.

Biomonitoring of a Nile Delta Lake using benthic foraminifera

Lake Edku, one of the northern Nile Delta lakes, is a shallow brackish coastal lake subjected to domestic and agricultural effluents via two main drains, El-Khairy and Barsik, in addition to the discharge water of hundreds of fish farms. This study measures the responses of the benthic foraminiferal assemblage to the environmental stressors in Lake Edku. Grain size, organic carbon, and seven potentially toxic elements (Cu, Pb, Zn, Cd, Cr, Ni, and As) were determined in nine short cores (25-35 cm depth). The lake was characterized by vertical increase in mud, organic matter, and concentrations of all metals, particularly in the eastern basin at the vicinity of the drain discharges. This trend coincides with a general decrease in species diversity and increase in deformed specimens. The foraminiferal assemblage was dominated by Ammonia tepida (Cushman), a pollution-tolerant and euryhaline species. This study demonstrates that benthic foraminiferal assemblages provide a reliable pollution proxy in the brackish environments of Nile Delta that can be used in the periodical monitoring of the coastal lakes.

Spatial distribution of heavy metals in rice grains and human health risk assessment in Hunan Province, China

Rice is the main food in China, and its pollution by heavy metals has attracted widespread attention. In this study, rice grain samples were collected from 14 prefecture-level cities in Hunan Province, China. The contents of 9 heavy metals (i.e., As, Cr, Co, Ni, Cu, Zn, Cd, Pb, and Sb) were measured using graphite digestion-inductively coupled plasma mass spectrometry (ICP-MS). Pearson correlation analysis and principal component analysis were performed to evaluate the correlation among these heavy metals. In addition, ordinary kriging interpolation were applied to investigate the spatial distribution pattern of the heavy metals. Results showed that the average concentrations of these heavy metals were 0.48 (As), 1.28 (Cr), 0.03 (Co), 0.84 (Ni), 2.39 (Cu), 15.73 (Zn), 0.28 (Cd), 0.66 (Pb), and 0.0043 (Sb) mg/kg, respectively. The single-factor pollution index (SFPI) contamination assessment showed that As, Pb, Cr, Ni, and Cd accumulated significantly in the rice grain, with over-standard rates of 100%, 100%, 64.70%, 47.05%, and 44.12%, respectively. The Sb concentrations at the sampling sites were low, and there was no obvious pollution. Health risk assessment showed that the target hazard quotient followed the order of As> Cr> Cd> Pb> 1.0> Co> Cu> Zn> Ni> Sb, and the carcinogenic risk value was in the order of Cd> Ni> As> Cr> 1.0×10^-4> Pb. In particular, quick actions should be taken to regulate As, Cr, and Cd contents in rice because they posed greater non-carcinogenic and carcinogenic health risks than the others to the local residents.

Response of microbial community to different land-use types, nutrients and heavy metals in urban river sediment

Nutrients and heavy metals (HM) in the sediment have an impact on microbial diversity and community structure. In this study, the distribution characteristics of nutrients, HM, and microbial community in the sediments along the Longsha River, a tributary of the Pearl River (or Zhu Jiang), China were investigated by analyzing samples from 11 sites. On the basis of the HM-contamination level, the 11 sampling sites were divided into three groups to explore the changes in microbial communities at different ecological risk levels. Results indicated that nutrient concentrations were higher near farmlands and residential lands, while the ecological risk of HM at the 11 sampling sites was from high to low as S10 > S2 > S9 > S6 > S11 > S7 > S5 > S8 > S3 > S4 > S1. Among these HM, Cu, Cr, and Ni had intense ecological risks. In addition, the results of Variance Partitioning Analysis (VPA) revealed a higher contribution of HM (35.93%) to microbial community variation than nutrients (12.08%) and pH (4.08%). Furthermore, the HM-tolerant microbial taxa (Clostridium_sensu_stricto_1, Romboutsia, norank_o__Gaiellales, and etc.) were the dominant genera, and they were more dynamic around industrial lands, while microbes involved in the C, N, and S cycles (e.g., Smithella, Thiobacillus, Dechloromonas, Bacter oidetes_vadinHA17, and Syntrophorhabdus) were inhibited by HM, while their abundance was lower near industrial lands and highway but higher around residential lands. A three-unit monitoring program of land-use types, pollutants, and microbial communities was proposed. These results provide a new perspective on the control of riparian land-use types based on contaminants and microbes, and different microbial community response patterns may provide a reference for contaminant control in sediments with intensive industrial activities.

Fractionation analysis and risk assessment of potential toxic elements in reservoir sediments in central China

The pollution of potential toxic elements (PTEs) in the environment is a persistent issue and draws public attention constantly. However, there is no study comprehensively assessing the PTE pollution of water supply reservoirs in central China. This study determined the total contents and fractions of seven PTEs in 10 water supply reservoirs of central China, and evaluated PTE pollution risks by adopting various models. The results indicated that PTE pollution in water supply reservoirs was lower comparing that in estuary or river sediments, and Mn (manganese) was the predominant PTE in central China reservoirs. Fractionation analysis revealed that for B1 fraction (exchangeable/acid-soluble fraction) of Mn, Zn (zinc) and B2 fraction (reducible fraction) of Pb (lead) was high, while the effective state portion of Cr (chromium) was small. The monomial potential ecological risk indices and Igeo values were low among most samples, indicating overall modest PTE pollution. However, the results of the individual contamination factor (ICF) suggested that Pb might lead to potential health risks to human beings.

Receptor model-oriented sources and risks evaluation of metals in sediments of an industrial affected riverine system in Bangladesh

Toxic metals in river sediments may represent significant ecological concerns, although there has been limited research on the source-oriented ecological hazards of metals in sediments. Surface sediments from an industrial affected Rupsa River were utilized in this study to conduct a complete investigation of toxic metals with source-specific ecological risk assessment. The findings indicated that the average concentration of Ni, Cr, Cd, Zn, As, Cu, Mn and Pb were 50.60 ± 10.97, 53.41 ± 7.76, 3.25 ± 1.73, 147.76 ± 36.78, 6.41 ± 1.85, 59.78 ± 17.77, 832.43 ± 71.56 and 25.64 ± 7.98 mg/kg, respectively and Cd, Ni, Cu, Pb and Zn concentration were higher than average shale value. Based on sediment quality guidelines, the mean effective range median (ERM) quotient (1.29) and Mean probable effect level (PEL) quotient (2.18) showed medium-high contamination in sediment. Ecological indexes like toxic risk index (20.73), Nemerow integrated risk index (427.59) and potential ecological risk index (610.66) posed very high sediment pollution. The absolute principle component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) model indicated that Zn (64.21%), Cd (51.58%), Cu (67.32%) and Ni (58.49%) in APCS-MLR model whereas Zn (49.5%), Cd (52.7%), Cu (57.4%) and Ni (44.6%) in PMF model were derived from traffic emission, agricultural activities, industrial source and mixed sources. PMF model-based Nemerow integrated risk index (NIRI) reported that industrial emission posed considerable and high risks for 87.27% and 12.72% of sediment samples. This work will provide a model-based guidelines for identifying and assessing metal sources which would be suitable for mitigating future pollution hazards in Riverine sediments in Bangladesh.

Temporal distribution patterns of metals in water, sediment, and components of the trophic structure in a tropical coastal lagoon of the Gulf of Mexico

Trophic transfer and bioaccumulation of trace metals have a profound impact on the structure and function of coastal areas; however, the metal accumulation patterns in detritus-based food webs and the influence of climatic variability have not been thoroughly investigated. The Tampamachoco Lagoon (Gulf of Mexico) is a coastal system impacted by emissions from a thermoelectric plant. We evaluated the spatial-temporal distribution patterns of Al, Cd, Hg, Cr, Cu, and Pb in water, sediments, and in organisms categorized by trophic levels (TLs), trophic guilds, and habitat preferences. The sediments had the highest concentrations of metals with no significant differences between seasons. The indices of geo-accumulation and potential ecological risk classified sediments as "moderately contaminated", evidencing a threat to human health through consumption of detritivores and filter-feeders. The lowest TLs (filter-feeders and detritivorous) reached the maximum Metal Pollution Index in the rainy season. According to discriminant analyses of metals and species, omnivorous and zoobentivorous organisms were associated with Hg during the rainy and dry seasons; while Al, Cd, and Cu were related to low TLs, and seston was associated with Pb. Food web magnification factor analysis showed that: (a) Pb, Cu, and Cr were biodiluted as trophic levels increased; (b) Cd and Hg showed temporal biomagnification trends; (c) Al, Pb, Cu, and Cd showed significant biodilution from the lowest TL to intermediate TLs; and (d) Hg was transferred from the lowest to intermediate TLs with clear biomagnification effects.

Distribution of Pb isotopes in different chemical fractions in bed sediments from lower reaches of the Xiangjiang River, Hunan province of China

This paper reports Pb isotopes in different fractions following the three step BCR and 1 M HCl extractions on river sediments from lower reaches of the Xiangjiang river in China, and highlights the importance of Pb isotopes in heavy metal contamination assessment. Lead concentrations and Pb isotopes in bulk sediments and sediment fractions (leachates and residues) from the river were analysed using ICP-MS techniques. Results showed that sediments were highly enriched with Pb with enrichment factors >5.5, while Pb in sediments was dominated by reducible and residual Pb fractions, residing mainly in Fe-oxide and silicate minerals. Pb isotopes in sediments was characterized by radiogenic Pb produced from the decay of uranium and thorium with ²⁰⁶Pb/²⁰⁷Pb ratios of 1.1744 for less radiogenic Pb and 1.1816 for more radiogenic Pb. The leachates and residues from BCR extraction generally had similar Pb isotope compositions, of which the ²⁰⁶Pb/²⁰⁷Pb ratios were 1.1798 ± 0.002 and 1.1844 ± 0.008 respectively. Differentiation of Pb isotopes between BCR leachates and residues was insignificant. However, differentiation between leachates and residues using 1 M HCl extraction was significant, as shown by average ²⁰⁶Pb/²⁰⁷Pb ratios of 1.1746 ± 0.005 and 1.1858 ± 0.008 for leachates and residues respectively. Pb isotopic tracing suggests that Pb in sediments from Zhuzhou section arose from the mixing of anthropogenic Pb from coal combustion (39%) and mining-smelting for Pb-Zn ores (58%); while Pb in sediments from Xiangtan, Changsha and Xiangyin sections arose from the mixing of anthropogenic Pb from mining-smelting for Pb-Zn ores (54%), and lithologically inherited Pb from granite weathering (35%) with a small amount of contribution from coal combustion (10%). The present study suggests that the BCR extraction scheme was not appropriate for ecological risk assessment of heavy metal contamination in mining-impacted (ore-Pb dominated) river sediments.

The role of microplastics in altering arsenic fractionation and microbial community structures in arsenic-contaminated riverine sediments

The ability of microplastics (MPs) to interact with environmental pollutants is of great concern. Riverine sediments, as sinks for multi-pollutants, have been rarely studied for MPs risk evaluation. Meanwhile, MPs generated from biodegradable plastics are questioning the safety of the promising materials. In this study, we investigated the effects of typical non-degradable polyethylene (PE) and biodegradable polylactic acid (PLA) MPs on sediment enzymes, arsenic (As) fractionation, and microbial community structures in As-contaminated riverine sediments. The results indicated that the presence of MPs (1% and 3%, w/w) led As transformed into more labile and bioavailable fractions in riverine sediments, especially under higher As and MPs levels. Analysis on microbial activities and community structures confirmed the strong potential of MPs in inhibiting microbial activities and shifting bacterial community succession patterns through enrichment of certain microbiota. Moreover, biodegradable PLA MPs presented stronger alterations in arsenic fractionation and microbial community structures than PE MPs did, which might be jointly attributed to adsorption behaviors, microbial alterations, and potential PLA degradation behaviors. The study indicated that MPs contamination increased As mobility and bioavailability, and shifted microbial communities in riverine sediments. Moreover, biodegradable MPs might lead to stronger microbial alterations and increases in As bioavailability, acting as a threat to ecological safety, which needed further exploration.

Evaluation of metal accumulation in Terme River sediments using ecological indices and a bioindicator species

Freshwater resources are hotspot areas for sustainable water use. Surface sediment samples from four stations in Terme River were collected seasonally between April 2019 and January 2020. Sample collection from 0 to 10 cm depth of the riverbed was carried out with an Ekman Dredge Grab. Cu, Pb, Zn, Ni, Mn, Fe, Co, As, Cr, Cd, and Al concentrations were determined with an inductively coupled plasma-mass spectrometry (ICP-MS). The percentage of organic matter in the sediment was evaluated by the combustion method. pH measurements were made with a pH meter. The concentrations of elements measured are listed in descending order as follows: Fe > Al > Mn > Cr > Cu > Zn > Ni > Co > Pb > As > Cd. Enrichment factor (EF), contamination factor (CF), and geo-accumulation index (I_geo) are the most commonly used tools to determine whether elements are of natural origin or anthropogenic origin. According to average EF values, the metals are listed as follows: Cd > Cu > Co > Fe > Cr > Pb > Mn > Zn > Al > Ni > As. The CF and I_geo values are listed as follows: Cd > Cu > Co > Fe > Cr > Pb > Mn > Zn > Al > Ni > As. According to EF results, Cd and Cu originate from human activities. The CF and I_geo indicate minimal enrichment for all metals. Potential ecological risk (PERI), pollution load (PLI), modified hazard quotient (mHQ), ecological contamination (ECI), and toxic risk indices (TRI) indicate low risk in the region. Human health risk indices also show that carcinogenic and noncarcinogenic risks are low. In the bioaccumulation evaluation performed on Myriophyllum spicatum species, it was determined that the plant accumulated Mn, Co, Ni, Cu, Zn, As, and Cd. These results show that Myriophyllum spicatum can be used as a bioindicator.

Severe contamination of carcinogenic heavy metals and metalloid in agroecosystems and their associated health risk assessment

The contamination of toxic heavy metals (i.e., Cd, Cr, Pb, and Ni) and metalloid (i.e., As) (TMMs) is considered as a major cause of increasing incidences of human and livestock cancers, gastrointestinal disorders and neurological problems. The levels of these TMMS in soil, irrigation water, and plants like Salanum lycopersicum (tomato), Spinacia oleracea (Spinach), and Triticum aestivum (Wheat) samples were detected which were collected from various localities across 100 km around the city of Lucknow, India. This study reported that the concentration of TMMs was within the range of maximum allowable concentration (MAC) (FAO/WHO, 2011) in most of the agricultural soil, whereas, it was higher in irrigation water. The TMMs levels in the edible parts of vegetables and cereal were in the range 1.91-53.94 μg/g, 5.06-40.49 μg/g, 4.08-2312-29 μg/g, 0.43-51.48 μg/g, and 0.01-1.65 μg/g, respectively which was significantly higher than the MAC. The B_AF of Cd and Ni was very high in the edible parts of the vegetables and cereal samples indicating an entry of TMMs in food chain through the metal-contaminated irrigation water, even if TMMs are low in the field soil. The contamination coefficient (Cfi) and Ecological risk factors (Efi) of the TMMs were detected in the range of low risk in all agricultural soil. The Ecological risk index (E_RI) of TMMs was at moderate risk, indicating a mild impact of the metal toxicity in the agro-ecosystems but the high risk on the consumers. The daily intake (DI) of TMMs through vegetables and cereal was below the maximum allowable daily intake (MTDI) but the carcinogenic risk factor (CRs) potential of Cr, Cd, Ni, and As was observed significantly higher for these vegetables and cereal, which indicated a complex scenario of a far-future carcinogenic health hazard on consumers in densely populated city of Lucknow, India and its surrounding regions.

Assessment of heavy metals in surface water, sediment and macrozoobenthos in inland rivers: a case study of the Heihe River, Northwest China

Long-term retention and accumulation of heavy metals in surface water and sediment pose a great threat to the sustainable development of aquatic ecosystems and human health. In this research, macrozoobenthos, and surface water and sediment heavy metal (Mn, Cr, Cu, Ni, Pb, Zn, Cd, and As) samples were collected from 23 sites in the upper and middle reaches of the Heihe River in the summers of 2019-2020. The interrelationships between heavy metals and macrozoobenthos were analyzed by Pearson correlation analysis and redundancy analysis (RDA), and the contamination level and potential ecological risk of the heavy metals in surface water and sediments were assessed by comprehensive pollution index (WQI), single potential ecological risk index ([Formula: see text]), and sediment quality guideline-quotient (SQG-Q), respectively. The results showed that the level of heavy metal pollution in the surface water of the Heihe River was extremely low, but the contents of Mn and Pb exceeded the third class of surface water environmental quality standards (GB 3838-2002). The spatial distribution of heavy metals in surface sediments were significantly different, and the average concentration of 8 heavy metals exceeded the background values of Gansu Province. Meanwhile, the pollution level of heavy metals in surface sediments was high pollution, and the ecological risk level was moderate risk. Combining [Formula: see text] and SQG-Q evaluations showed that Cd, Ni, and Cr were the main ecological risk factors. In addition, the distribution coefficients of Cr and Cd were low, indicating that Cr and Cd were easily released from the surface sediments, causing secondary pollution. In terms of the source of the heavy metals, Cu, As, Zn, Cr, and Ni mainly came from industrial and agricultural wastewaters, Pb was from the mining industry and natural sources, and Mn and Cd mainly came from tailings and their landfill leachate. Basommatophora and Araneae can be used as potential indicator organisms for heavy metal pollution in surface water, and Basommatophora, Coleoptera, Hemiptera, and Araneae can be used as indicator species for heavy metal pollution in surface sediments. The study showed that macroinvertebrate community characteristics had a sensitive response to heavy metals in the surface waters and sediments of the Heihe River, which can be used to evaluate the pollution status of heavy metals in inland rivers.

Assessment of Potentially Toxic Elements’ Contamination in the Soil of Greater Cairo, Egypt Using Geochemical and Magnetic Attributes

Enhanced soil’s magnetic susceptibility reflects particles of anthropogenic/natural origin; therefore, it can be utilized as an indication of soil contamination. A total of 51 different land-use soil samples collected from Greater Cairo, Egypt, were assessed integrally using potentially toxic elements content (PTEs), magnetic susceptibility, and statistical and spatial analysis. PTE concentrations were compared to the world average, threshold, and screening values set by literature. Various environmental indices were estimated to assess soil contamination with these elements. Spatial distribution maps of PTEs and environmental indices were constructed to provide decision makers with a certain identification of riskier areas. In general, the concentrations of the analyzed PTEs showed variation with land-use types and follows a pattern of: Industrial > Agricultural > Urban. The distribution of PTEs in Greater Cairo was influenced by several anthropogenic sources, including traffic emission, industrial activity, and agricultural practices. The measured magnetic susceptibility values indicate magnetically enhanced soil signals dominated by multi-domain or pseudo-single-domain superparamagnetic particles of anthropogenic origin. A significant association was observed between magnetic susceptibility values and Co, Cr, Cu, Ni, and V, and the calculated environmental indices. It can be concluded that magnetic susceptibility is of proven effectivity in the assessment of soil contamination.

Ecological Risk Assessment Related to the Presence and Toxicity of Potentially Toxic Elements in Ashes from Household Furnaces

The study material was comprised of 23 samples of ashes generated after the combustion of conventional and alternative fuels combined with selected fractions of municipal waste. The analyses performed involved determining the total concentration of As, Al, Cr, Fe, Ni, and their bioaccessible, ion-exchange, and carbonate-bound fractions. It was found that all of the samples analysed may display an elevated level of susceptibility to the reduction processes, which undoubtedly increases the mobility of trace elements, including the toxic ones. The predominant elements were Al and Fe, whereas considerably lower concentrations were observed for Ni, Cr, and As. The percentage share of the ion-exchange and carbonate-bound fraction ranged from 49% of the total concentration for As to as much as 0.35% in the case of Fe. The calculated Risk Assessment Code index points to a high risk related to the presence of As, medium to low risk related to the presence of Ni and Cr, and low to no risk related to the presence of Fe and Al. The calculated values of the Ecological Risk Index, associated with the combustion of selected municipal waste fractions and low-quality hard coals, combusted individually or in combination with different types of wood, point to a very high ecological risk. This is mainly related to the high concentrations and toxicity of As.

An in-depth human health risk assessment of potentially toxic elements in highly polluted riverine soils, Příbram (Czech Republic)

Environmental pollution by potentially toxic element (PTE) and the associated health risks in humans are increasingly becoming a global challenge. The current study is an in-depth assessment of PTEs including the often studied lead (Pb), manganese (Mn), zinc (Zn), arsenic (As) and the less-studied titanium (Ti), rubidium (Rb), strontium (Sr), zirconium (Zr), barium (Ba) and thorium (Th) in highly polluted floodplain topsoil samples from the Litavka River, Czech Republic. Soil chemical properties including carbon (C_ox) and reaction (pH_H₂O) together with iron (Fe) were assessed in the same soils. A portable X-ray fluorescence spectrometer (p-XRFS) (Delta Premium) was used to measure the PTEs and Fe contents of the soils. Soil organic carbon and reaction pH were determined following routine laboratory procedures. The concentration level of each PTE was compared against world average and crustal values, with the majority of elements exceeding the aforementioned geochemical background levels. Distributions of the PTEs were mapped. Two pollution assessment indices including enrichment factor (EF) and pollution index (PI) levels were calculated and their means for Zn (43.36, 55.54), As (33.23, 43.59) and Pb (81.08, 103.21) show that these elements were enriched. Zn, As and Pb accounted for the high pollution load index (PLI) levels observed in the study. The EF and PI distribution maps corresponded with the concentration distribution maps for each PTE. On health risk assessment, hazard quotients (HQ) in different human groups varied. Children had the highest HQs for all PTEs than adults (women and men). PTEs with high HQ levels in distinct human groups were As, Zr and Pb. Zirconium is a less likely element to pose a health risk in humans. Nonetheless, it should be kept in check despite its low pollution occurrence.

A comprehensive exploration on distribution, risk assessment, and source quantification of heavy metals in the multi-media environment from Shaying River Basin, China

Comprehensively understand the distribution of pollutants in the multi-media environment at basin scale is of major importance to the ecological risk assessment and pollution control. In this study, multi-media contamination characteristics of eight heavy metals in the water, soil, and sediment from the Shaying River Basin of China have been analyzed to probe their ecological risks and potential sources. Results revealed that heavy metal concentrations in pore water were higher than those in surface water. While the mean concentrations of most heavy metals increased follow the order of bankside soil (BS)<water-level-fluctuating zone soil (WLFZS)<sediment. The WLFZ was an important transition zone between the BS and sediment for pollutant exchange. The mean heavy metal concentrations in surface water were all below their corresponding water quality standards except Hg. Whereas the mean concentrations of Cr, Ni, Zn, Cd, and Hg in BS, WLFZS, and sediment exceeded their corresponding background values. The assessment results of pollution and risks indicated that Hg and Cd posed the highest potential risks in each medium. Furthermore, according to the factor analysis and PMF model, six potential sources were identified, in which agricultural, fuel combustion, and industrial sources were the dominant anthropogenic sources, accounting for 23.84%, 17.43%, and 14.25% of the total contribution.

Trace metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in the surface sediments from Sanya River, China: Distribution, sources and ecological risk

The urban inland river ecosystems are now facing comprehensive pollution and governance pressures. Up to now, few works related to the multiple pollution assessment of trace metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) for the urban inland river sediments have been reported in China. Our study investigated the spatial distribution, ecological risk and potential sources of trace metals, PAHs and PCBs in surface sediment collected from 20 sampling sites of Sanya River, Hainan Province, China. The pollution status and potential ecological risk of trace metals were evaluated using the contamination indexes including geoaccumulation index (I_geo), individual potential ecological risk (E_rⁱ), potential ecological risk index (RI) and pollution load index (PLI). Considering the carcinogenicity and toxicity of PAHs and PCBs to human health and the ecological environment, we also analyzed the distributions, sources and adverse biological effects of PAHs and PCBs according to the sediment quality guidelines (SQGs), principal component analysis (PCA) and other source analysis. This study revealed that the surface sediments in Sanya River were extremely slight pollution and showed a very low ecological risk according to I_geo, E_rⁱ, PLI and RI results for trace metals. Besides, PAHs and PCBs pollution detected may not pose considerable adverse biological effect to ecological environment in a foreseeable period on the basis of comprehensive research results. The overall surface sediments quality of the Sanya River not seem to pose a serious pollution and ecological risk based on the evaluation results of multiple pollution factors. The study provided detailed information on the multiple pollution status and location of surface sediments, one of the key environmental indicators of international tourism cities, in the Sanya River, which would be useful for the water quality improvement of Sanya River and the environmental remediation of the other coastal ecosystems from different regions.

Eco-toxic risk assessment and source distribution of trace metals in surface sediments of the coastal and in four rivers estuary of Sarawak

Background

Trace metals pollution in the coastal and estuarine sediment could harm water quality and aquatic organisms, leading to potential long-term health risks on the environment and humans. Thus, the purpose of this study was to conduct an assessment of selected trace metals in surface sediments of the coastal and in four rivers estuary in the Sarawak State of Malaysia to investigate their distribution, environmental risk, and potential source distribution.

Results

Average concentrations of trace metals in sediment increased in the following order: Cd ˂ As ˂ Co ˂ Cu ˂ Ni ˂ Cr ˂ Zn ˂ Mn ˂ Mg ˂ Fe. The enrichment, contamination, and geo-accumulation index results showed that surface sediments were polluted with Zn and Mg. In contrast, the other metals (i.e., As, Fe, Mn, Ni, Cr, Cu, Co, and Cd) indicated background concentration to minor contamination. Generally, the pollution load index values showed that almost all the sampling sites were unpolluted with the selected trace metals. Sediment quality guidelines (SQGs) and risk indexes were employed to assess the ecotoxicological risk of trace metal contamination in the sediments. The results proved that studied trace metals are not likely to have a deleterious impact on bottom-dwelling organisms. Still, a further accumulation of trace metals such as Zn, Ni, and Cr with time may adversely affect bottom-dwelling organisms. The risk index results showed a low ecological risk to the study sites. The correlation analysis and principal component analysis indicated that nine studied trace metals have strong interrelationships, suggesting common pollution sources or similar geochemical characteristics.

Conclusions

The study highlights the need to make tremendous efforts to monitor and control trace metal pollution in the coastal and estuarine areas.

Microbial diversity in intensively farmed lake sediment contaminated by heavy metals and identification of microbial taxa bioindicators of environmental quality

The cumulative effects of anthropogenic stress on freshwater ecosystems are becoming increasingly evident and worrisome. In lake sediments contaminated by heavy metals, the composition and structure of microbial communities can change and affect nutrient transformation and biogeochemical cycling of sediments. In this study, bacterial and archaeal communities of lake sediments under fish pressure contaminated with heavy metals were investigated by the Illumina MiSeq platform. Despite the similar content of most of the heavy metals in the lagoon sediments, we found that their microbial communities were different in diversity and composition. This difference would be determined by the resilience or tolerance of the microbial communities to the heavy metal enrichment gradient. Thirty-two different phyla and 66 different microbial classes were identified in sediment from the three lagoons studied. The highest percentages of contribution in the differentiation of microbial communities were presented by the classes Alphaproteobacteria (19.08%), Cyanophyceae (14.96%), Betaproteobacteria (9.01%) y Actinobacteria (7.55%). The bacteria that predominated in sediments with high levels of Cd and As were Deltaproteobacteria, Actinobacteria, Coriobacteriia, Nitrososphaeria and Acidobacteria (Pomacocha), Alphaproteobacteria, Chitinophagia, Nitrospira and Clostridia (Tipicocha) and Betaproteobacteria (Tranca Grande). Finally, the results allow us to expand the current knowledge of microbial diversity in lake sediments contaminated with heavy metals and to identify bioindicators taxa of environmental quality that can be used in the monitoring and control of heavy metal contamination.

Evaluation of potential ecological risks in potential toxic elements contaminated agricultural soils: Correlations between soil contamination and polymetallic mining activity

Extensive mineral exploitation activities in history have aggravated potential toxic elements (PTEs) contamination in agricultural soils in China. Comprehensive ecological risk assessment is of great significance to orientate the restoration of contaminated soils, especially for those with high background values and multiple sources. The study area is located in the major rice producing area of China. Historically, there was a silver mine and a lead-zinc mine in the area, which were successively closed during the investigation. The intensive mining activities caused serious PTEs pollution in the agricultural soils around the mining area. In this study, five PTEs (As, Cd, Cr, Hg and Pb) selected to assessed the potential of geoaccumulation index in assessing agricultural soil potential risk assessment by identifying ecological risk sources. 315 of soil samples collected in 2009, 2014, 2018 were comprehensively analyzed by single pollution index evaluation (single factor index, geoaccumulation index), comprehensive evaluation (Nemerow index, potential ecological risk index) and trend analysis. Single factor index analysis showed that geoaccumulation index considered the impact of natural diagenesis of background values and human activities on the environment, ensuring high evaluation accuracy comparing to other methods used in typical complex agricultural soils. The modified potential ecological risk index revealed that the high background area did not represent high risk area, which was consistent with the implementation effect of governance measures. This study can provide important insights for policymakers and environmental engineers to quantitatively recognize the soil pollution and the effectiveness of governance based on applicable and reasonable evaluation methods.

Distribution and assessment of cadmium contamination in sediments from the Four River inlets to Dongting Lake, China

The total concentrations of Cd in bulk sediments and those of the BCR sequential extraction fractions of sediments from inlets of the Four Rivers that feed Dongting Lake were determined using ICP-MS techniques. The results suggested that Cd was heterogeneously distributed in the inlet sediments of the rivers, with the highest degree of enrichment in sediments from the Xiangjiang River. The Cd anomaly was defined as Cd enrichment in sediments with an EF (enrichment factor) > 10.0, and it was identified in the inlet sediments of the Xiangjiang River. Cd in the sediments was dominated by acid-soluble Cd at a proportion of 23.9-69.8 (%) compared to its total concentrations in the sediments. The inlet sediments of the Four Rivers were contaminated with Cd, with the highest degree of contamination in the inlet sediments of the Xiangjiang River. The Cd contamination as well as the Cd anomaly in the sediments were closely related to the industrial activities (e.g. smelting and refining for ore minerals) in the areas, and Cd contamination at high levels may represent an ecological risk for the lake watershed. Cd contamination of the inlet sediments may also impact the lake basin sediments and is harmful to the lake ecological system, particularly for sediments of the Xiangjiang River. Therefore, it is essential to control and treat Cd contamination in the inlet sediments for ecological environmental protection of lake watersheds.

Effect of minerals and heavy metals in sand samples of Ponnai river, Tamil Nadu, India

River sand samples have been collected from Ponnai river, Tamil Nadu, India for characterization of minerals and heavy metals by different spectroscopic techniques. Initially, the samples were subjected by Fourier Transform-Infra Red (FT-IR) spectroscopic technique and infra-red absorption bands values are observed in the range of 515–520, 695–700, 775–780 cm⁻¹ which shows the presence of quartz in all the samples. Similarly, infra-red peaks were absorbed for feldspar, kaolinite, calcite, gibbsite and organic carbon and confirmed by X-Ray diffraction (XRD) technique. Additionally, zircon, aragonite, magnetite and kyanite minerals were identified in the samples using only the XRD method. The concentration of heavy metals such as Pb, Cr, Zn, Ni, Hg, As, Mn, Cu has been determined by flame atomic absorption spectrometry (FAAS). An average metal concentration measured in mg kg⁻¹ were: Pb 0.12, As 0.15, Hg 0.13, Cu 2.80, Zn 10.15 Cr 12.70, Ni 2.86 and Mn 104.94 and hence found in the order of Mn > Cr > Zn > Ni > Cu > As > Hg > Pb. These average values do not exceed the world average value and hence potentially do not affect the quality of sand in the river. In addition to that, presences of heavy metals are confirmed by scanning electron microscope equipped with energy dispersive X-ray spectrometry (SEM/EDS) analysis. In order to understand the possible natural and anthropogenic sources of heavy metals, multivariate statistical techniques such as Pearson correlation, principal component and cluster analysis were performed. Results obtained from the statistical techniques were good agreement with each other.

Pollutant source, ecological and human health risks assessment of heavy metals in soils from coal mining areas in Xinjiang, China

This study aims to analyze the pollution characteristics and sources of heavy metal elements for the first time in the Zhundong mining area in Xinjiang using the linear regression model. Additionaly, the health risks with their probability and infleuencing factors on different groups of people's were also evaluated using Monte Carlo (MC) simulation approach. The results shows that 89.28% of Hg was from coal combustion, 40.28% of Pb was from transportation, and 19.54% of As was from atmospheric dust. The main source of Cu and Cr was coal dust, Hg has the greatest impact on potential ecological risks. which accounted for 60.2% and 81.46% of the Cu and Cr content in soil, respectively. The all samples taken from Pb have been Extremely polluted (100%). 93.3% samples taken from As have been Extremely polluted. The overall potential ecological risk was moderate. Adults experienced higher non-carcinogenic risks of heavy metals from their diets than children. Interestingly, body weight was the main factor affecting the adult's health risks. This research provides more comprehensive information for better soil management, soil remediation, and soil pollution control in the Xinjiang mining areas.

Research trends and frontiers on source appointment of soil heavy metal: a scientometric review (2000-2020)

In recent years, source appointment of soil heavy metal has attracted growing attention. However, few studies have attempted to make a comprehensive and systematical review on this topic. For this reason, a total of 1051 publications were retrieved from the Web of Science (WOS) database between 2000 and 2020. A scientometric analysis was carried out to reveal the characteristics of publications, research power, and research hotspots. CiteSpace was used to visualize and summarize the information about the development in this field. The results showed that (1) the number of publications in source appointment of soil heavy metal had increased rapidly; Environmental science and ecology and environmental sciences were top 2 most popular subject categories; (2) Research power was mainly distributed in Asia, Europe, and North America. China and Chinese Academy of Sciences were the most productive country and institution in terms of publications in this field. Biao Huang (China) was the most productive author. However, Hakanson L (Sweden) was the most influential author in terms of citation frequency; (3) Heavy metal, source identification, and contamination were the most frequent keywords. Keyword clustering analysis showed that the research hotspots mainly concentrated on air pollution, bioremediation, spatial distribution, soil, PCA, and so on; (4) Keyword bursts analysis showed that the research frontiers mainly focused on spatial analysis of soil heavy metal and exposure risk to human health.

Distribution of Pb, Zn and Cd in stream and alluvial sediments in the area with past Zn smelting operations

The sources of Zn, Pb and Cd in alluvial and stream sediments have been studied in the area of historical Zn smelting tradition. 30 samples of stream sediments and samples from 4 alluvial sediment profiles were collected. Fractions 0.125–0.063 and < 0.063 mm were analysed by the means of ICP-MS prior 4-acid digestion. The highest levels of Zn, Cd and Pb were detected in the alluvial sediments in the closest vicinity to the abandoned slag and ore roasting residue waste dumps, reaching 96 and 4520 mg/kg, 522 and 26,800 mg/kg and 3.7 and 31 mg/kg for Pb, Zn and Cd in stream and alluvial sediments, respectively. The Voglajna River then transports contamination particles into the Savinja River, which afterwards flows into the Sava River. Consequently, the anomaly can even be detected in the Sava River, more than 30 km downstream. Higher levels of Pb, Zn and Cd have been found in fraction < 0.063 mm compared to 0.125–0.063 mm fraction. Impacts of historically contaminated soil erosion and in particular the wash-out of Zn-smelting waste from the improperly managed waste dump were recognised as the dominant sources of Zn, Cd and Pb in the stream and alluvial sediments.

Exposure to multiple metals and the risk of hypertension in adults: A prospective cohort study in a local area on the Yangtze River, China

BACKGROUND

Exposure to multiple metals is recognized as a common and real scenario in daily life. However, limited prospective studies have assessed associations between multiple metals exposure and hypertension.

METHODS

In total, 2625 adults in a local area on the Yangtze River were investigated at baseline from 2014 to 2015 and followed up in 2019. We measured baseline urine levels of 22 metals and used multivariate logistic analysis and Bayesian kernel machine regression (BKMR) to explore associations between multiple metals exposure and the risk of hypertension.

RESULTS

A total of 385 individuals (29.6%) were diagnosed with hypertension. Five metals (cadmium, copper, magnesium, molybdenum and zinc) were positively associated with hypertension in single-metal models. Cadmium and zinc remained significantly positive associations after adjusting for these five metals, with the odds ratio (OR) in the highest quartiles of 1.49 (95% CI: 1.01, 2.21; p-trend = 0.05) and 1.60 (95% CI: 1.08, 2.38; p-trend = 0.02), respectively. BKMR analysis showed a significant joint effect of multiple metals on hypertension when the concentrations of five metals were at or above their 55th percentile compared with their median values. A potential interaction between cadmium and zinc in increasing the risk of hypertension was observed with the OR_int of 1.41 (95%CI: 1.05, 1.89).

CONCLUSIONS

We identified the joint effect of multiple metals on hypertension and observed a significant interaction between cadmium and zinc. Further cohort studies are needed to clarify the health effects of multiple metals exposure in a larger population.

Co-exposures of TiO2 nanoparticles and cadmium ions at non-lethal doses aggravates liver injury in mice with ConA-induced hepatitis

The wide applications of titanium dioxide nanoparticles (TNP) and ubiquitous cadmium (Cd) pollution increase the chances of their co-existence in the environment and also pose potential health risks to humans. However, toxicological understanding of effects of co-exposures of TNP and Cd to mammals is still lacking. In this study, non-lethal doses of TNP and CdCl2 were intravenously co-administered to healthy or Concanavalin A (ConA)-induced acute hepatitis mice. Co-exposures of TNP and CdCl2 increased the accumulation of Cd2+ in the liver of hepatitis mice, which was 1.42-fold higher than that of healthy mice. Co-exposures also caused liver damage only in hepatitis mice on the basis of histopathological and biochemical evidence. Further study showed that co-exposure upregulated hepatic oxidative stress, which further induced autophagy and apoptosis only in the liver of hepatitis mice. This finding underlines the potential toxicological consequences of co-exposures of TNP and CdCl2 in hepatitis sufferers.

Significant Decrease in Heavy Metals in Surface Sediment after Ten-Year Sustainable Development in Huaxi Reservoir Located in Guiyang, Southwestern China

In the Karst area of southwestern China, the heavy metals in the sediment of a reservoir are determined by both human activities and the high background values. Thus, this study explores the change of heavy metals in surface sediment after ten-year sustainable development in the upstream areas of a reservoir, Huaxi Reservoir, located in Guiyang of southwestern China, then evaluates the risk of these heavy metals to water environment systematically and finally identifies the sources in both 2019 and 2009. The results reveal that all of the measured heavy metals decrease dramatically and their spatial distributions change from the increase-decrease pattern to decrease-increase pattern, implying different locations of main source input. The risk indices based on the total or average content and relative or reference values have decreased to the lowest level. However, those indices calculated from the absolute content of each metalloid still show a low or a moderate risk because of the high background value, such as As and Cr. Moreover, although only one main source of heavy metals is identified in both 2019 and 2009, the risk from human activities still cannot be neglected because agricultural production and infrastructure construction would promote the weathering of soil and then these heavy metals from the soil will be brought into the reservoir with the rainfall-runoff process. The high background value of specific heavy metals, e.g., As and Cr would still exert some challenges to the water environment protections because the non-point source input of heavy metal cannot be controlled easily by promulgating a series of bans. These results provide important reference for creating the policies of water environment protection, especially in some Karst area of southwestern China that exhibits high background value of heavy metals.

Physical and chemical characteristics of slag produced during Pb refining and the environmental risk associated with the storage of slag

Metallurgical waste originating from the Zn and Pb refining process presents varying chemical composition and physical properties and contains varying quantities of pollutants. In the study, both fresh and weathered samples of production slag from the final Pb refining process were used to determine its physical parameters and chemical composition as well as to perform an environmental risk assessment (RAC, mRAC) related to its storage. This paper focuses on determining parameters such as natural humidity (1.8%) and bulk density (1267 kg/m³) of the slag. Also, its toxicity was analysed using bio-tests, its pH was measured (11.92) and the content of sulphates (3.5 wt%), chlorides (0.3 wt%) and selected heavy metals (Cd, Cu, Fe, Mn, Zn, Pb) was determined. The Individual Contamination Factor was determined, yielding the following order of the hazard level: Pb > Cu > Zn > Cd > Fe > Mn. Based on the mobility of metals determined using the Mobility Factor, it was concluded that the hazard level followed the sequence Cd > Pb > Zn > Mn > Fe > Cu. The obtained water leaching results were compared to the values found in the legal regulations in force. Based on this comparison, it was established that the slag studied constitutes toxic waste containing considerable quantities of sulphides and chlorides. The material is also a considerable source of readily leaching elements (Cd, Zn and Pb), and thus any product created using the slag may become hazardous to the environment. Also, the waste studied must not be used in the form in which it is currently stored due to the leaching of particularly toxic elements (Cd and Pb) in water solutions with increasing acidity.

Concentrations, Distribution, and Pollution Assessment of Metals in River Sediments in China

This study conducted a review on the concentrations, spatial distribution and pollution assessment of metals including As, Hg, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in 102 river sediments in China between January 2008 and July 2020 based on the online literature. The geo-accumulation index (Igeo) and potential ecological risk index (RI) were used for the pollution assessment of the metals. The results showed that the ranges of metals were: 0.44 to 250.73 mg/kg for As, 0.02 to 8.67 mg/kg for Hg, 0.06 to 40 mg/kg for Cd, 0.81 to 251.58 mg/kg for Co, 4.69 to 460 mg/kg for Cr, 2.13 to 520.42 mg/kg for Cu, 39.76 to 1884 mg/kg for Mn, 1.91 to 203.11 mg/kg for Ni, 1.44 to 1434.25 mg/kg for Pb and 12.76 to 1737.35 mg/kg for Zn, respectively. The median values of these metals were descending in the order: Mn > Zn > Cr > Cu > Pb > Ni > Co > As > Cd > Hg. Compared with the SQGs, As and Cr manifested higher exceeding sites among the metals. Metals of river sediments manifested a significant spatial variation among different regions, which might be attributed to the natural weathering and anthropogenic activity. The mean Igeo values of the metals presented the decreasing trends in the order: Cd > Hg > Zn > Cu > As > Pb > Ni > Co > Cr > Mn. Cd and Hg manifested higher proportions of contaminated sites and contributed most to the RI, which should be listed as priority control of pollutants. Southwest River Basin, Liaohe River Basin, and Huaihe River Basin manifested higher ecological risks than other basins. The study could provide a comprehensive understanding of metals pollution in river sediments in China, and a reference of the control of pollutant discharge in the river basins for the management.