Risk analysis of heavy metal concentration in surface waters across the rural-urban interface of the Wen-Rui Tang River, China

Impact of coking plant to heavy metal characteristics in groundwater of surrounding areas: Spatial distribution, source apportionment and risk assessments

Coking industry is a potential source of heavy metals (HMs) pollution. However, its impacts to the groundwater of surrounding residential areas have not been well understood. This study investigated the pollution characteristics and health risks of HMs in groundwater nearby a typical coking plant. Nine HMs including Fe, Zn, Mo, As, Cu, Ni, Cr, Pb and Cd were analyzed. The average concentration of total HMs was higher in the nearby area (244.27 µg/L) than that of remote area away the coking plant (89.15 µg/L). The spatial distribution of pollution indices including heavy metal pollution index (HPI), Nemerow index (NI) and contamination degree (CD), all demonstrated higher values at the nearby residential areas, suggesting coking activity could significantly impact the HMs distribution characteristics. Four sources of HMs were identified by Positive Matrix Factorization (PMF) model, which indicated coal washing and coking emission were the dominant sources, accounted for 40.4%, and 31.0%, respectively. Oral ingestion was found to be the dominant exposure pathway with higher exposure dose to children than adults. Hazard quotient (HQ) values were below 1.0, suggesting negligible non-carcinogenic health risks, while potential carcinogenic risks were from Pb and Ni with cancer risk (CR) values > 10-6. Monte Carlo simulation matched well with the calculated results with HMs concentrations to be the most sensitive parameters. This study provides insights into understanding how the industrial coking activities can impact the HMs pollution characteristics in groundwater, thus facilitating the implement of HMs regulation in coking industries.

Non-phytoremediation and phytoremediation technologies of integrated remediation for water and soil heavy metal pollution: A comprehensive review

Since the 1980s, there has been increasing concern over heavy metal pollution remediation. However, most research focused on the individual remediation technologies for heavy metal pollutants in either soil or water. Considering the potential migration of these pollutants, it is necessary to explore effective integrated remediation technologies for soil and water heavy metals. This review thoroughly examines non-phytoremediation technologies likes physical, chemical, and microbial remediation, as well as green remediation approaches involving terrestrial and aquatic phytoremediation. Non-phytoremediation technologies suffer from disadvantages like high costs, secondary pollution risks, and susceptibility to environmental factors. Conversely, phytoremediation technologies have gained significant attention due to their sustainable and environmentally friendly nature. Enhancements through chelating agents, biochar, microorganisms, and genetic engineering have demonstrated improved phytoremediation remediation efficiency. However, it is essential to address the environmental and ecological risks that may arise from the prolonged utilization of these materials and technologies. Lastly, this paper presents an overview of integrated remediation approaches for addressing heavy metal contamination in groundwater-soil-surface water systems and discusses the reasons for the research gaps and future directions. This paper offers valuable insights for comprehensive solutions to heavy metal pollution in water and soil, promoting integrated remediation and sustainable development.

Analysis and probabilistic health risk assessment of vertical heavy metal pollution in the water environment of reservoir in the West Coast New Area of Qingdao, China

The West Coast New Area is a typical city in China where water supply is predominantly sourced from reservoirs. Heavy metal pollution in these reservoirs directly impacts the safety of drinking water and human health. Therefore, this study comprehensively evaluated the status of heavy metal pollution in the water environment and sediment of the main water supply reservoir in the study area, revealing the interaction relationship and pollution sources, as well as assessing the probabilistic health risks to human beings. The results show that there are different degrees of pollution in the main water supply reservoirs in the study area, and the pollution increases with the increase of water depth. The heavy metal pollution index was up to 2681, indicating heavily pollution. The main polluting elements were Mn and Fe, and the maximum contents were 4.11 mg·L-1 and 0.68 mg·L-1, respectively, which far exceeded the Class III standard limit of drinking water in China. The main source of pollution is human activities, and Mn release from sediment aggravates deep water pollution. The non-carcinogenic risk index of heavy metals in the reservoir, ranging from 4% to 14%, is higher than 1, indicating a potential non-carcinogenic threat. Furthermore, heavy metals have a much greater impact on children compared to adults, among which Mn is the main contributor to human non-carcinogenic risk, contributing more than 60%. Therefore, controlling the content of Mn and Fe can effectively reduce the heavy metal pollution of reservoir and human health risk. The research results are of great significance for the utilization of reservoir water resources and the protection of the ecological environment in the study area.

Comprehensive monitoring of contamination and ecological-health risk assessment of potentially harmful elements in surface water of Maroon-Jarahi sub-basin of the Persian Gulf, Iran

The increase in heavy metal concentration in water bodies due to rapid industrial and socio-economic development significantly threatens ecological and human health. This study evaluated metal pollution and related risks to ecology and human health in the Maroon-Jarahi river sub-basin in the Persian Gulf and Oman Sea basin, southwest Iran, using various indicators. A total of 70 water samples were taken from the sampling sites in the Maroon, Allah, and Jarahi sub-basins and analyzed for nine heavy metals. According to the results, the mean concentration of metals in the sampling locations across the entire sub-basin of Maroon-Jarahi was observed as follows Iron (528.22 µg/L), zinc (292.62 µg/L), manganese (56.47 µg/L), copper (36.23 µg/L), chromium (11.78 µg/L), arsenic (7.09 µg/L), lead (3.43 µg/L), nickel (3.23 µg/L), and cadmium (1.38 µg/L). Most of the metals were detected at the highest concentration in the sub-basin of the Jarahi River. The Water Quality Index (WQI) index in the basin varied from 18.74 to 22.88, indicating well to excellent quality. However, the investigation of the pollution status at the monitoring stations, based on the classification of Degree of Contamination (CD) and Heavy Metal Pollution Index (HPI) indices, revealed that they are in the category of relatively high pollution (16 < CD < 32) to very high (32 ≤ CD), and in the low pollution category (HPI < 15) to high pollution (HPI < 30), respectively. According to the three sub-basins, the highest amount of WQI, HPI, and Cd was observed in the stations located in the sub-basins of the Jarahi River. The calculation of Heavy Metal Evaluation Index (HEI) also indicated that only 10% of the monitoring stations are in moderate pollution (10 < HEI < 20), while in other monitoring stations the HEI level is less than 10. The Potential ecological risk factors ( E r i ) of an individual metal was obtained as follows: Cd (173.70) > As (131.99) > Zn (57.52) > Cu (55.39) > Ni (48.98) > Cr (21.57) > Pb (0.71), revealing that Cd and As are the main elements responsible for creating ecological risk in the studied area. The Maroon-Jarahi watershed included areas with ecological risks that ranged from low (PERI ≤ 150) to very high (PERI ≥ 600). HI and ILCR health indicators indicated that consumption and long-term contact with river water in the study area can cause potential risks to human health, especially children. Moreover, the findings, the highest level of pollution and health risk for both children and adults, considering both exposure routes, occurred in the Jarahi River sub-basin, suggesting that those who live in the vicinity of the Jarahi River are likely to face more adverse health effects. In addition, the findings of the evaluation of the relationship between land use patterns and water quality in the studied basin showed that agricultural lands acts as a main source of pollutants, but forest lands play an important role in the deposition of pollutants and the protection of water quality at the basin scale. In general, the results of pollution indicators, risk assessment, and statistical techniques suggest that the lower sub-basin, the Jarahi area, and the Shadegan wetland are the most polluted areas in the investigated sub-basin due to excessive discharge of agricultural runoff, industrialization, and rapid urbanization. Thus, special measures should be considered to reduce the risks of HMs pollution in the sub-basin of the Maroon-Jarahi watershed, especially its downstream and the impact of agricultural land use on water quality should be taken into consideration in basin management plans.

Comprehensive approach integrating water quality index and toxic element analysis for environmental and health risk assessment enhanced by simulation techniques

Due to water shortages and the potential impact of Ethiopia's new dam on the Nile River, Egypt is seeking new water resources. This study assesses the drinking water quality and associated risks from potentially toxic elements (PTEs) in the Quaternary aquifer (QA) in Beni-Suef, Egypt. Using a comprehensive approach, including PHREEQC geochemical modeling, ionic ratios, multivariate statistical analyses, and the integrated weight water quality index (WQI), the study evaluated the sources of ion contamination and the mixing of Nile water with QA. Various indices, such as the Heavy Metal Pollution Index (HPI), ecological Risk Index (RI), Hazard Quotient (HQ), and Hazard Index (HI), were used to assess ecological and health risks. Monte Carlo simulations provided probabilistic assessments of non-carcinogenic risks for adults and children. GIS tools were used to map risk indices, identifying the most deteriorated locations for sustainable management. The hydrochemical analysis revealed water facies including Na-Cl, Ca-Mg-HCO3, and mixed types, influenced by carbonate dissolution, ion exchange, and silicate weathering. Contamination sources, particularly in the north and south, were linked to agricultural activities, irrigation return flow, municipal waste, and evaporation. The WQI indicated that 10.14% of samples were extremely poor, 21.7% were poor, 26% were medium, and 42% were good to excellent. PTE contamination varied, with HPI values indicating good water quality in the central area in 53.6% of the collected samples (HPI < 30), but contamination in the north and south is high (HPI > 51). Ecological Risk Index values were below the threshold in 100% of samples (RI < 30), confirming water safety regarding PTEs. In comparison, for hazard index (HI) through oral/ingestion, adults exhibited HI values ranging from 0.012 to 2.16, while children showed higher values, ranging from 0.045 to 8.25. However, the hazard index for oral/ingestion exceeded safe limits in the north and south (HI oral > 1), posing non-carcinogenic risks. Monte Carlo simulations revealed significant risks from oral exposure to manganese (HQ oral > 1), particularly in El-Wasta and El-Fashn, necessitating further treatment and management.

Gut dysbiosis of Rana zhenhaiensis tadpoles after lead (Pb) exposure based on integrated analysis of microbiota and gut transcriptome

Lead (Pb) is a ubiquitously detected heavy metal pollutant in aquatic ecosystems. Previous studies focused mainly on the response of gut microbiota to Pb stress, with less emphasis on gene expression in intestine, thereby limiting the information about impacts of Pb on intestinal homeostasis in amphibians. Here, microbial community and transcriptional response of intestines in Rana zhenhaiensis tadpoles to Pb exposure were evaluated. Our results showed that 10 μg/L Pb significantly decreased bacterial diversity compared to the controls by the Simpson index. Additionally, 1000 μg/L Pb exposure resulted in a significant reduction in the abundance of Fusobacteriota phylum and Cetobacterium genus but a significant expansion in Hafnia-Obesumbacterium genus. Moreover, transcriptome analysis revealed that about 90 % of the DEGs (8458 out of 9450 DEGs) were down-regulated in 1000 μg/L Pb group, mainly including genes annotated with biological functions in fatty acid degradation, and oxidative phosphorylation, while up-regulated DEGs involved in metabolism of xenobiotics by cytochrome P450. The expression of Gsto1, Gsta5, Gstt4, and Nadph showed strong correlation with the abundance of genera Serratia, Lactococcus, and Hafnia-Obesumbacterium. The findings of this study provide important insights into understanding the influence of Pb on intestinal homeostasis in amphibians.

Assessing surface water quality in Hungary's Danube basin using geochemical modeling, multivariate analysis, irrigation indices, and Monte Carlo simulation

Evaluation of water quality is crucial for managing surface water effectively, ensuring its suitability for human use, and sustaining the environment. In the lower Danube River basin, various methods were employed to assess surface water quality for irrigation, drinking, human health risk purposes and the main mechanism control the surface water chemistry. These methods included water quality indicators (WQIs), complex statistical analyses, geographic information systems (GIS), Monte Carlo simulation, and geochemical modeling. Physicochemical analyses of surface water samples revealed primarily Ca-Mg-HCO3- is the dominant water types. Principal component analysis (PCA), ionic ratios and piper, chloro alkaline index, Chadha, and Gibbs diagrams identified three distinct water characteristics influenced by water-rocks interaction, evaporation, ions exchange, and human activities. The geochemical modeling showed Danube River water's strong ability to dissolve gypsum, halite, and anhydrite (SI < 0) and precipitate aragonite, dolomite, and calcite with saturation index (SI) value greater than 0 along its flow path. The irrigation water quality index (IWQI = 99.6-107.6), sodium adsorption ratio (SAR = 0.37-0.68), sodium percentage (Na% = 13.7-18.7), soluble sodium percentage (SSP = 12.5-17.5), Potential Salinity (PS = 0.73-1.6), and Residual Sodium Carbonate (RSC = - 1.27-0.58) values were used, mainly indicating acceptable quality with some limitations. Danube River water was unsuitable for drinking based on WQI value (WQI = 81-104). Oral exposure of children to specific components showed a higher hazard index (HI > 1) compared to adults, indicating a 2.1 times higher overall non-carcinogenic risk hazard index. However, Monte Carlo simulation demonstrated negligible iron, manganese, and nitrate health hazards for both age groups. These findings are valuable for water quality management decisions, contributing to long-term resource sustainability.

Advanced approach combines integrated weight water quality index and potential toxic elements for environmental and health risk assessment supported by simulation technique in Oued Souf, Algeria

The current research study evaluated the health and environmental risks issues associated with potentially toxic elements (PTEs) in the complex terminal aquifer located in the Algerian desert. The methods used included principal component and cluster (dendrogram) analysis to estimate source of ions and contamination. Various indices such as the Heavy Metal Pollution Index (HPI), Metal Index, hazard quotient, hazard index (HI), and cancer risk (CR) were applied to assess both environmental and human health risks. Furthermore, the Monte Carlo method was applied for probabilistic assessment of carcinogenic and non-carcinogenic risks through oral and dermal exposure routes in both adults and children. The results revealed that approximately 16% of the samples fell within the low pollution category (HPI < 100), indicating relatively lower levels of heavy metal contamination. However, the remaining 84% of the samples exhibited high pollution levels, indicating a significant presence of heavy metal pollutants in the northeastern part of the investigated area. The calculated average risk index (RI) for the collected samples was 18.99, with a range from 0.03 to 103.21. This indicates that a large portion, 82% of the samples, could cause low ecological risk (RI < 30), whereas the remaining 18% indicate a significant environmental pollution risk. The HI for oral ingestion showed that adults had HI values ranging from 0.231 to 1.54, while children exhibited higher values, ranging from 0.884 to 5.9 (Fig. 5a). For dermal exposure, HI values in adults ranged from 2.71E-07 to 8.74E-06 and in children, from 2.18E-06 to 7.03E-05. These findings highlight the potential non-carcinogenic risks associated with oral exposure to PTEs and underscore the increased vulnerability of children to metals such as Fe, Mn, Pb, and Cr. Most samples showed CR exceeding 1 × 10-4 for chromium (Cr) and lead (Pb), indicating a significant vulnerability to carcinogenic effects in both children and adults.

Land use/cover drive functional patterns of bacterial communities in sediments of a subtropical river, China

The bacterial community in sediment serves as an important indicator for assessing the environmental health of river ecosystems. However, the response of bacterial community structure and function in river basin sediment to different land use/cover changes has not been widely studied. To characterize changes in the structure, composition, and function of bacterial communities under different types of land use/cover, we studied the bacterial communities and physicochemical properties of the surface sediments of rivers. Surface sediment in cropland and built-up areas was moderately polluted with cadmium and had high nitrogen and phosphorus levels, which disrupted the stability of bacterial communities. Significant differences in the α-diversity of bacterial communities were observed among different types of land use/cover. Bacterial α-diversity and energy sources were greater in woodlands than in cropland and built-up areas. The functional patterns of bacterial communities were shown that phosphorus levels and abundances of pathogenic bacteria and parasites were higher in cropland than in the other land use/cover types; Urban activities have resulted in the loss of the denitrification function and the accumulation of nitrogen in built-up areas, and bacteria in forested and agricultural areas play an important role in nitrogen degradation. Differences in heavy metal and nutrient inputs driven by land use/cover result in variation in the composition, structure, and function of bacterial communities.

Health Risk Assessment of Heavy Metal(loid)s in the Overlying Water of Small Wetlands Based on Monte Carlo Simulation

Heavy metal(loid) (HM) contamination is a significant threat to wetland ecosystem. However, contamination risks of HMs in overlying water of small wetlands, which are easily ignored because of their minor occupancy in an overall area, are nearly unknown. A total of 36 water samples containing six HMs were collected from the urban and rural small wetlands of Urumqi in China, and the contamination levels and probabilistic health risks caused by HMs were assessed using the Nemerow pollution index (NPI) and the health risk assessment model introduced by the US EPA. The results revealed that the average concentration of Hg in the urban and rural small wetlands surpassed the Class II thresholds of the Environmental Quality Standards for Surface Water (GB 3838-2002) by factors of 3.2 and 5.0 times, respectively. The overall contamination levels of HMs in the small wetlands fall into the high contamination level. Results of a health risk assessment indicated that non-carcinogenic health risk of the investigated HMs are found to be lower than the acceptable range for adults, but higher than the acceptable range for children. Meanwhile, As falls into the low carcinogenic risk level, whereas Cd falls into the very low carcinogenic risk level. Overall, HMs in rural small wetlands showed relatively higher contamination levels and probabilistic health risks than that of urban small wetlands. In addition, As was identified as the dominant health risk factor in the overlying water of small wetlands in the study area. Findings of this study provide scientific support needed for the prevention of HM contamination of small wetlands in arid zones.

Assessment of Human Health Risk Indices Due to Metal Contamination in the Surface Water of the Negro River Sub-Basin, Áncash

The accelerated loss of glacial cover in the Cordillera Blanca in Áncash, Peru, exposes the underlying rocks with high concentrations of sulfides from the Chicama Formation to oxidation and leaching processes, generating acid rock drainage (ARD) in glacial and periglacial areas. These are transported by surface runoff, contaminating the surface water with high concentrations of metals and sulfates, as well as increasing the acidity, which poses a risk to human health and the ecosystem. Therefore, the risk indices for human health due to metal contamination were evaluated at 19 surface water sampling points distributed in the Río Negro sub-basin. Hydrochemical analyses revealed average metal concentrations in the following order: Fe (28.597 mg/L), Al (3.832 mg/L), Mn (1.085 mg/L), Zn (0.234 mg/L), Ni (0.085 mg/L), Co (0.053 mg/L), Li (0.036 mg/L), Cu (0.005 mg/L), and Pb (0.002 mg/L). The risk was determined by calculating the Heavy Metal Pollution Index (HPI) and the Hazard Index (HI). The average HPI value was 360.959, indicating a high level of contamination (HPI ≥ 150). The human health risk assessment indicated that adverse effects caused by iron, lithium, and cobalt in children and adults should be considered. Through the use of Pearson correlation analysis, principal component analysis, and cluster analysis, it was identified that SO42-, Fe, S, Al, Co, Mn, Ni, Zn, and Li originate from natural sources, associated with the generation of ARD in glacial and periglacial areas.

Ecological risk assessment of heavy metal(loid)s in riverine sediments along the East China Sea: A large-scale integrated analysis

This study comprehensively assesses spatial distribution, pollution levels, and potential sources of heavy metal(loid)s in surface sediments across multiple river systems along the coastal area of the East China Sea. Copper in Qiantang River and Xiangshan Bay showed higher concentations and exceeded the threshold effect value, while the higher content of Lead was mainly found in the Saijiang River, Oujiang River, and Minjiang River. Heavy metal(loid)s in the alluvium of Qiantang River, Jiaojiang River, and Yangtze River showed low to moderate pollution levels, with Cd posing the highest ecological risk, followed by Hg. Meanwhile, Qiantang River, Jiaojiang River, Yangtze River, and Oujiang River exhibited considerable to moderate ecological risks and low toxic risk. PMF model analysis results reveal that concentrations of Cr, Ni, and As were closely related with natural geogenic input (36.56 %), while industrial and traffic activities (48.77 %) were primary source of Cu, Pb, Zn, and Hg, and main source of Cd was agricultural emissions (14.67 %).

Source-specific probabilistic health risk assessment of heavy metals in surface water of the Yangtze River Basin

The detrimental effects of heavy metal accumulation on both ecosystems and public health have raised widespread concern. Source-specific risk assessment is crucial for developing effective strategies to prevent and control heavy metal contamination in surface water. This study aims to investigate the contamination characteristics of heavy metals in the Yangtze River Basin, identifying the pollution sources, assessing the risk levels, and further evaluating the health risks to humans. The results indicated that the average concentrations of heavy metals were ranked as follows: zinc (Zn) > arsenic (As) > copper (Cu) > chromium (Cr) > cadmium (Cd) > nickel (Ni) > lead (Pb), with average concentrations of 38.02 μg/L, 4.34 μg/L, 2.53 μg/L, 2.10 μg/L, 1.17 μg/L, 0.84 μg/L, and 0.32 μg/L, respectively, all below the WHO 2017 standards for safe drinking water. The distribution trend indicates higher concentrations in the upper and lower reaches and lower concentrations in the mid-reaches of the river. By integrating the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) receptor model and Positive Matrix Factorization (PMF) model, the main sources of heavy metals were identified as industrial activities (APCS-MLR: 41.3 %; PMF: 42.1 %), agricultural activities (APCS-MLR: 30.1 %; PMF: 27.4 %), and unknown mix sources (APCS-MLR: 29.1 %; PMF: 30.4 %). The calculation of the hazard index (HI) for both children and adults was <1, indicating no non-carcinogenic or carcinogenic risks. Based on the source-specific risk assessment, agricultural activities contribute the most to non-carcinogenic risks, while industrial activities pose the greatest contribution to carcinogenic risks. This study offers a reference for monitoring heavy metals and controlling health risks to residents, and provides crucial evidence for the utilization and protection of surface water in the Yangtze River Basin.

Distribution, seasonal variation and influencing factors of total dissolved inorganic arsenic in the middle and lower reaches of the Yellow River

The concentrations of dissolved arsenate in natural water has an important impact on human health. The distributions, seasonal variation and major influencing factors of total dissolved inorganic arsenic (TDIAs) were studied in the Yellow River. The concentrations of TDIAs in the middle and lower reaches of the Yellow River ranged from 4.3 to 42.4 nmol/L, which met the standards for drinking water of WHO. The seasonal variation of TDIAs concentration in the middle and lower reaches of the Yellow River was highest in summer, followed by autumn and winter, and lowest in spring. The influencing factors of TDIAs concentration in the middle and lower reaches of the Yellow River mainly include the hydrological conditions, topographical variation, the adsorption and desorption of suspended particulate matter (SPM) and the intervention of human activities. The absorption of TDIAs by phytoplankton in the Xiaolangdi Reservoir (XLD) is an important factor affecting its distributions and seasonal variation. The annual flux of TDIAs transported from the Yellow River into the Bohai Sea ranged from 1.1 × 105 to 4.5 × 105 mol from 2016 to 2018, which is lower than the flux in 1985 and 2009. The carcinogenic risks (CR) of TDIAs for children and adults were all within acceptable levels (<10-6).

Improvement of heavy metal separation performance by positively charged small-sized graphene oxide membrane

Multilayered graphene oxide (GO) membranes are promising to be widely applied to purify water effectively. However, the performance of most membranes prepared at present is not ideal, which may be related to the pore diameter of the substrate (determining the real loading amount of GO) and the size of the GO nanosheets (determining the number of channels on the unit area), which has not been fully studied. In this study, a rotating dip-coating reactor were firstly developed to ensure the uniform deposition of reactants on the surface of the substrate. Then, the preparation method for the membrane was improved. Microfiltration membranes were used as the supporting substrate, polydopamine was deposited as the adhesive layer, ethylenediamine was used to restrict the layer spacing to strengthen the size exclusion effect, and positively charged polyethyleneimine (PEI) was used to strengthen the Donnan effect. Finally, the effects of the pore size of the substrate and the size of the GO nanosheets on the membrane performance were investigated. Compared with the substrates with a pore size of 0.22 μm in most literatures, substrates of 0.1 μm can retain more small GO (SGO) nanosheets, thereby improving the performance. The performance of the SGO membrane was much better than that of the large-sized GO membrane. With a water permeability of no less than 7.9 L/(m2·h·bar), rejection rates for Pb2+ and Cd2+ of the SGO membrane could reach more than 97%. These findings are constructive to separate heavy metals from water effectively.

Impact of industrial hotspots on Tamla nala and Nunia nala confluence - a tributary of the Damodar river

Clean water is essential for drinking, household use, and agriculture. Researchers studied 39 sites near Tamla nala and Nunia nala channels in Durgapur and Asansol City (West Bengal) to assess the deterioration level of water due to industrial discharge. During the first phase out of three, the researchers conducted a spatial representation of various physicochemical parameters, such as temperature, pH, Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Total Hardness (TH), Electrical Conductivity (EC), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), significant anions such as chloride (Cl-), nitrate (NO3-), phosphate (PO4-3), sulfate (SO42-), cyanide (CN-1) and fluoride (F-), as well as heavy metals/metalloids such as lead (Pb), cadmium (Cd), chromium (Cr), iron (Fe), copper (Cu), nickel (Ni), mercury (Hg) and arsenic (As). As observed the parameters at various sites along the stream exceeded threshold limits majorly due to industrial discharge: highest pH, TDS, TH, EC, Cl-, SO42- at site 26; Fe at site 1, TSS, COD, CN- at site 33, 31, 2 respectively; Cd, Ni, Cu at site 19; Hg and Pb at site 3 and As at site 20. Contaminated areas were marked in red and secure areas in green. Additionally, the HMPI (Heavy metal pollution index) was estimated for eight locations to understand the impact of heavy metal pollution in the second phase of the study. An extremely high HMPI indicates heightened toxicity and health risks for both residents and outsiders. The Canadian Water Quality Index (1.0) was calculated for eight sites in the third phase based on seventeen parameters. The resulting WQI value was below 44, indicating poor water quality at the sites. Due to the poor quality and critical heavy metal toxicity, the authors recommended continuous monitoring, strict regulation enforcement, increased treatment capacity, Zero Liquid Discharge implementation, and raising awareness among residents.

Risk Assessment and Sources Apportionment of Toxic Metals in Two Commonly Consumed Fishes from a Subtropical Estuarine Wetland System

The widespread occurrence of heavy metals in aquatic environments, resulting in their bioaccumulation within aquatic organisms like fish, presents potential hazards to human health. This study investigates the concentrations of five toxic heavy metals (Pb, Hg, Zn, Cu, and Cr) and their potential health implications in two economically important fish species (Otolithoides pama and Labeo bata) from a subtropical estuarine wetland system (Feni estuary, Bangladesh). Muscle and gill samples from 36 individual fish were analyzed using energy dispersive X-ray fluorescence (EDXRF). The results revealed that the average quantities of heavy metals in both fishes' muscle followed the declining order of Zn (109.41-119.93 mg/kg) > Cu (45.52-65.43 mg/kg) > Hg (1.25-1.39 mg/kg) > Pb (0.68-1.12 mg/kg) > Cr (0.31-5.82 mg/kg). Furthermore, Zn was found to be present in the highest concentration within the gills of both species. While the levels of Cu, Zn, and Cr in the fish muscle were deemed acceptable for human consumption, the concentrations of Pb and Hg exceeded the permissible limits (>0.5 mg/kg) for human consumption. Different risk indices, including estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and carcinogenic or target risk (TR), revealed mixed and varying degrees of potential threat to human health. According to the EDI values, individuals consuming these fish may face health risks as the levels of Zn, Cu, and Cr in the muscle are either very close to or exceed the maximum tolerable daily intake (MTDI) threshold. Nevertheless, the THQ and HI values suggested that both species remained suitable for human consumption, as indicated by THQ (<1) and HI (<1) values. Carcinogenic risk values for Pb, Cr, and Zn all remained within permissible limits, with TR values falling below the range of (10-6 to 10-4), except for Zn, which exceeded it (>10-4). The correlation matrix and multivariate principal component analysis (PCA) findings revealed that Pb and Cr primarily stemmed from natural geological backgrounds, whereas Zn, Cu, and Hg were attributed to human-induced sources such as agricultural chemicals, silver nanoparticles, antimicrobial substances, and metallic plating. Given the significance of fish as a crucial and nutritious element of a balanced diet, it is essential to maintain consistent monitoring and regulation of the levels and origins of heavy metals found within it.

Occurrence, distribution, and ecological risk assessment of heavy metals in Chao Phraya River, Thailand

Understanding heavy metals in rivers is crucial, as their presence and distribution impact water quality, ecosystem health, and human well-being. This study examined the presence and levels of nine heavy metals (Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in 16 surface water samples along the Chao Phraya River, identifying Fe, Mn, Zn, and Cr as predominant metals. Although average concentrations in both rainy and dry seasons generally adhered to WHO guidelines, Mn exceeded these limits yet remained within Thailand's acceptable standards. Seasonal variations were observed in the Chao Phraya River, and Spearman's correlation coefficient analysis established significant associations between season and concentrations of heavy metals. The water quality index (WQI) demonstrated varied water quality statuses at each sampling point along the Chao Phraya River, indicating poor conditions during the rainy season, further deteriorating to very poor conditions in the dry season. The hazard potential index (HPI) was employed to assess heavy metal contamination, revealing that during the dry season in the estuary area, the HPI value exceeded the critical threshold index, indicating the presence of heavy metal pollution in the water and unsuitable for consumption. Using the species sensitivity distribution model, an ecological risk assessment ranked the heavy metals' HC5 values as Pb > Zn > Cr > Cu > Hg > Cd > Ni, identifying nickel as the most detrimental and lead as the least toxic. Despite Cr and Zn showing a moderate risk, and Cu and Ni posing a high risk to aquatic organisms, the main contributors to ecological risk were identified as Cu, Ni, and Zn, suggesting a significant potential ecological risk in the Chao Phraya River's surface water. The results of this study provide fundamental insights that can direct future actions in preventing and managing heavy metal pollution in the river ecosystem.

Spatial and temporal distribution characteristics and risk assessment of heavy metals in groundwater of Pingshuo mining area

Groundwater pollution in the Pingshuo mining area is strongly associated with mining activities, with heavy metals (HMs) representing predominant pollutants. To obtain accurate information about the pollution status and health risks of groundwater, 189 groups of samples were collected from four types of groundwater, during three periods of the year, and analyzed for HMs. The results showed that the concentration of HMs in groundwater was higher near the open pit, waste slag pile, riverfront area, and human settlements. Except for Ordovician groundwater, excessive HMs were found in all investigated groundwater of the mining area, as compared with the standard thresholds. Fe exceeded the threshold in 13-75% of the groundwater samples. Three sources of HMs were identified and quantified by Pearson's correlation analysis and the PMF model, including coal mining activities (68.22%), industrial, agricultural, and residential chemicals residue and leakage (16.91%), and natural sources (14.87%). The Nemerow pollution index revealed that 7.58% and 100% of Quaternary groundwater and mine water samples were polluted. The health risk index for HMs in groundwater showed that the non-carcinogenic health risk ranged from 0.18 to 0.42 for adults, indicating an acceptable level. Additionally, high carcinogenic risks were identified in Quaternary groundwater (95.45%), coal series groundwater (91.67%), and Ordovician groundwater (26.67%). Both carcinogenic and non-carcinogenic risks were greater for children than adults, highlighting their increased vulnerability to HMs in groundwater. This study provides a scientific foundation for managing groundwater quality and ensuring drinking water safety in mining areas.

Responses in Plant Growth and Root Exudates of Pistia stratiotes under Zn and Cu Stress

At present, the situation regarding heavy metal pollution in aquatic environments is becoming more and more serious. The bioaccumulation of heavy metals in aquatic plants causes obvious phytotoxicity, which can also induce secondary pollution in the aquatic environment. Zinc and copper, as indispensable elements for plant growth, are also prominent heavy metals in water pollution in China, and their concentrations play a crucial role in plant growth. In this study, we investigated the response of Pistia stratiotes (P. stratiotes) to different concentrations of Zn and Cu, and the results showed that plant growth and photosynthesis were inhibited under both Zn (1, 2, 4, and 8 mg/L) and Cu (0.2, 0.4, 0.8, and 1 mg/L) stresses. The relative growth rates of P. stratiotes under 8 mg/L Zn or 1 mg/L Cu stress were 6.33% and 6.90%, which were much lower than those in the control group (10.86%). Meanwhile, Zn and Cu stress caused insignificant change in the relative water contents of plants. The decrease in phlorophyll fluorescence parameters and chlorophyll contents suggested the significant photoinhibition of Zn and Cu stress. Chemical analysis of plant root exudates showed that the root secretion species obtained by gas chromatography-mass spectrometry (GC-MS) mainly included amino acids, alkanes, aldehydes, ketones, phenols, and more. Compared with the control group, the influence of Zn or Cu on the reduction in relative amounts of exudates was greater than that on the increase. The results of this study provide important data for the utilization of P. stratiotes in heavy metal-polluted water environments.

Potentially toxic elements in sediments near mines-a comprehensive approach for the assessment of pollution status and associated risk for the surface water environment

This research is focused on the assessment of the pollution status of river and lake sediments near Pb, Zn, and Cu mines and tailings in the southeastern part of Serbia-Krajište area. The study is based on hypothesis that investigated rivers and lakes in the Krajište area could be polluted by potentially toxic elements (PTEs) and that these elements could pose considerable ecological risk to the studied surface water environment. High PTE contents are detected in studied river sediments (up to 7892 mg kg-1 for Zn, 3224 mg kg-1 for Cu, 36,790 mg kg-1 for Pb, 64.2 mg kg-1 for Cd, and 1444 mg kg-1 for As). Given that the contents of the studied elements in most of the river sediments exceeded the background values, values prescribed by regulations of the Republic of Serbia, as well as probable effect concentration (PEL), it is possible to conclude that sediments were heavily polluted and that detrimental effects can be expected. Contamination indices including the enrichment factor (EF), contamination factor (CF), index of geoaccumulation (Igeo), potential ecological risk index (Eri), ecological risk index (RI), pollution load index (PLI), and aggregative toxicity index (ATI) were used to assess the degree of pollution by PTEs. The ecological risk assessment revealed that there is a significant risk observed for toxic elements (primarily Pb, Cu, Cd, and As) at this moment. The highest contamination indices (EF, Igeo, CF, PLI, and ATI) are mainly associated with historical and current mining activities. The Monte Carlo analysis based on the risk assessment indices was used to evaluate the uncertainty. The most pronounced toxic risk is found for the Pb, Cu, Cd, and As which assessment was in the range of high and extremely high-risk probabilities. The obtained results suggest that levels of toxic elements pose a significant ecological risk to the surface water environment near Pb, Zn, and Cu mines in the Krajište area. The methodology applied in this paper could be very useful for other researchers dealing with the problem of environmental pollution by toxic elements.

Heavy metals/-metalloids (As) phytoremediation with Landoltia punctata and Lemna sp. (duckweeds): coupling with biorefinery prospects for sustainable phytotechnologies

Heavy metals/-metalloids can result in serious human health hazards. Phytoremediation is green bioresource technology for the remediation of heavy metals and arsenic (As). However, there exists a knowledge gap and systematic information on duckweed-based metal phytoremediation in an eco-sustainable way. Therefore, the present review offers a critical discussion on the effective use of duckweeds (genera Landoltia and Lemna)-based phytoremediation to decontaminate metallic contaminants from wastewater. Phytoextraction and rhizofiltration were the major mechanism in 'duckweed bioreactors' that can be dependent on physico-chemical factors and plant-microbe interactions. The biotechnological advances such as gene manipulations can accelerate the duckweed-based phytoremediation process. High starch and protein contents of the metal-loaded duckweed biomass facilitate their use as feedstock in biorefinery. Biorefinery prospects such as bioenergy production, value-added products, and biofertilizers can augment the circular economy approach. Coupling duckweed-based phytoremediation with biorefinery can help achieve Sustainable Development Goals (SDGs) and human well-being.

Potentially toxic elements contamination in the water resources: an integrated risk assessment approach in the upper Citarum watershed area

The Citarum watershed is West Java Province's most important water resource; hence, harmful compounds should be monitored regularly. This study assessed pollution levels along with ecological and health risks from Cd, Pb, Mn, Fe, Cu, Cr, and Hg contamination in river water, sediment, groundwater, and soil in Citarum's upper watershed. In river water, the average amounts of Cd, Pb, Mn, Fe, Cu, Cr, and Hg were 0.002, 0.05, 0.092, 0.649, 0.022, 0.001, and 0.421 mg/L. In sediment, they were 7.4, 1175.1, 32,289.9, 37.3, 3.9, and 0.015 mg/kg. The mean concentrations of Cd, Pb, Mn, Fe, Cu, Cr, and Hg in groundwater were 0.004, 0.046, 0.567, 0.366, 0.019, 0.001, and 0.177 mg/L, and in soil, BDL, 10.2, 744.6, 50,094.1, 45.6, 5.9, and 0.015 mg/kg. The river water and groundwater were highly polluted by PTEs, with HPI values of 14,733 and 933, respectively. While PTEs pollution levels and risk in sediment and soil were low based on I-geo, CF, PLI, and M-ERM-Q values, PTEs contamination in river water may cause adverse impacts on aquatic living organisms (HQ > 1). The population doing recreational activities in river ecosystems was still safe from non-carcinogenic and carcinogenic impacts due to PTEs exposure from river water and sediment (THI < 1 and TCR value < 1E-04), while the population in the upper Citarum River was not safe from the carcinogenic risk due to PTE exposure from groundwater and soil (TCR > 1E-04). The sensitivity analysis showed that Cd concentration in groundwater is the most influential factor in cancer risk, with a total contribution of 99.9%. Therefore, a reduction in Cd concentration in groundwater is important to reduce cancer risk in the population.

Evaluation of metal pollution characteristics using water and moss in the Luanchuan molybdenum mining area, China

Luanchuan is rich in molybdenum resources, and mining activities are frequent, but over-mining can cause serious metal pollution to the local environment. To explore the degree of metal pollution caused by mining activities, the content characteristics and spatial distribution of metals in mining areas were studied by measuring the concentrations of Fe, Mn, Zn, Ba, Mo, Cu, Cr, Co, V, and W in surface water and mosses of mining areas. In addition, the metal pollution index (HPI), contamination factor (CF), and pollution load index (PLI) were used to evaluate metal pollution, and factor analysis was used to analyze the sources of metals. The results of the analysis of surface water at the mine site indicate the most abundant element in surface water, with a maximum concentration of 3713.8 μg/L, and its content far exceeds the water quality standard of Class III of the Environmental Quality Standard for Surface Water. The results of the HPI analysis showed that nearly 90% of the surface water was moderately contaminated (HPI ≥ 15). The results of the analysis of atmospheric deposition at the mine site confirm that the metal elements with a high threat to the atmospheric environment are Mo and W. The results of PLI indicate that the level of atmospheric deposition pollution in the study area is severe (PLI > 4). Factor analysis indicated that rock weathering and mining activities were the main sources of metals. This study provides a theoretical basis for the investigation and control of metal pollution in similar metal mining areas.

Gut microbiota perturbations during larval stages in Bufo gargarizans tadpoles after Cu exposure with or without the presence of Pb

Cu and Pb are ubiquitous environmental contaminants, but there is limited information on their potential impacts on gut microbiota profile in anuran amphibians at different developmental stages during metamorphosis. In this study, Bufo gargarizans tadpoles were chronically exposed to Cu alone or Cu combined with Pb from Gs26 throughout metamorphosis. Morphology of tadpoles, histological characteristic and bacterial community of intestines were evaluated at three developmental stages: Gs33, Gs36, and Gs42. Results showed that Cu and Cu + Pb exposure caused various degrees of morphological and histological changes in guts at tested three stages. In addition, bacterial richness and diversity in tadpoles especially at Gs33 and Gs42 were disturbed by Cu and Cu + Pb. Beta diversity demonstrated that the bacterial community structures were influenced by both heavy metals exposure and developmental stages. Alterations in taxonomic composition were characterized by increased abundance of Proteobacteria and Firmicutes, reduction of Fusobacteriota, as well as decreased Cetobacterium and increased C39 at all three stages. Overall, response of gut bacterial diversity and composition to Cu stress depends on the developmental stage, while the altered patterns of bacterial community at Cu stress could be modified further by the presence of Pb. Moreover, predicted metabolic disorders were associated with shifts in bacterial community, but needs integrated information from metagenomic and metatranscriptomic analyses. These results contribute to the growing body of research about potential ecotoxicological effects of heavy metals on amphibian gut microbiota during metamorphosis.

Oral and dermal exposure to natural radionuclides and heavy metals in water and sediments of Nile River, Qena, southern Egypt

This study assessed the levels of natural radionuclides (226Ra, 232Th, and 40K) and heavy metals (Hg, Fe, Cr, As, Zn, Cu, Cd, and Pb) in surface water and sediment samples from the Nile River in Qena Governorate, southern Egypt, using a gamma-ray spectrometer, 3" NaI (Tl) scintillation detector coupled with 1024 multi-channel analyzer, and an atomic absorption spectrometer. In surface water and sediments, the average activity concentrations of natural radionuclides were 40K (4.73 Bq L-1; 395.76 Bq kg-1) > 226Ra (0.41 Bq L-1; 18.14 Bq kg-1) > 232Th (0.30 Bq L-1; 17.98 Bq kg-1). The average heavy metal concentrations in surface water in µg L-1 were Fe (121.0) > Zn (33.80) > Cr (28.0) > Cu (8.62) > Pb (8.35) > As (1.19) > Hg (0.81) > Cd (0.12). In Nile sediments the concentrations in mg kg-1 were Fe (1670.0) > Zn (207.0) > Cr (29.40) > Cu (16.20) > Pb (4.32) > Hg (0.41) > Cd (0.31) > As (0.14). The heavy metal evaluation index (HMEI) calculations for water samples revealed that 31% of the samples were suitable for domestic use, while 69% were not. The geo-accumulation index, enrichment factor, and ecological risk factor for sediments were estimated, showing extreme enrichment for Hg and Zn with high ecological risk for Hg. Health risks for adults were evaluated due to oral and dermal exposure to Nile surface water and sediments from the study area, indicating minimal radiological risks and potential carcinogenic and non-carcinogenic risks from the metals.

Characterization and source apportionment of microplastics in Indian composts

Microplastics (MP), small plastic particles under 5 mm, are pollutants known to carry heavy metals in ecosystems. Composts are a significant source of soil microplastics. This study examined MSW composts from Kochi and Kozhikode in India for microplastic concentrations and heavy metals' accumulation thereon. Microplastics were isolated using zinc chloride density separation, with Fenton's reagent used for organic matter oxidation. Resin types were identified using FTIR analysis that showed the presence of PE, PP, PS, nylon, PET, and allyl alcohol copolymer. In Kozhikode's compost, the average concentration of microplastics was 840 ± 30 items/kg, while Kochi had 1600 ± 111 items/kg, mainly polyethylene films. PE was the most prevalent resin, comprising 58.3% in Kozhikode and 73.37% in Kochi. Heavy metal analysis of MP showed significant concentrations of lead, cadmium, zinc, copper, and manganese adsorbed on the surface of microplastics. The concentrations of heavy metals in the MP before Fenton oxidation ranged from 1.02 to 2.02 times the corresponding concentrations in compost for Kozhikode and 1.23 to 2.85 times for Kochi. Source apportionment studies revealed that 64% of microplastics in Kozhikode and 77% in Kochi originated from single-use plastics. Ecological risk indices, PLI and PHI, showed that composts from both locations fall under hazard level V. The study revealed that compost from unsegregated MSW can act as a significant source of microplastics and heavy metals in the soil environment, with single-use plastics contributing major share of the issue.

Effect of Copper Exposure on the Cholesterol Metabolism in Broiler Liver

Copper (Cu) is a kind of widely used dietary supplement in poultry production, and a common environmental pollutant at the same time. Excess Cu exposure has been reported to accumulate in the liver and induce cytotoxicity, but the effect of Cu toxicity on hepatic cholesterol metabolism is still uncertain. Herein, we aimed to reveal the effect of excess Cu on the liver and primary hepatocytes of broilers at various concentrations. We found that 110 mg/kg Cu supplement remarkably increased blood cholesterol levels by detecting serum TC, LDL-C, and HDL-C in the broilers, while there was no significant difference in 220 and 330 mg/kg Cu supplements. In addition, high Cu exposure resulted in severe hepatic steatosis and hepatic cord derangement in the broilers. Oil red O staining of primary hepatocytes showed that Cu treatment caused intracellular neutral lipid accumulation. However, the hepatic TC content indicated a downward trend in both liver tissues and hepatocytes after Cu exposure. Furthermore, the expression of cholesterol metabolism-related indicators (SREBP2, HMGCR, LDLR, and CYP7A1) was notably decreased in the Cu-treated groups. While the expression of the key enzyme of cholesterol esterification (ACAT2) did not change significantly. Taken together, our findings preliminarily revealed excess Cu-induced hepatic cholesterol metabolism dysfunction, providing a deeper understanding of the molecular mechanisms of Cu-induced hepatotoxicity.

Investigating the impacts of heavy metal(loid)s on ecology and human health in the lower basin of Hungary's Danube River: A Python and Monte Carlo simulation-based study

This study aimed to determine the environmental and health risks of the heavy metal levels in the Danube River in Hungary. The metals, including Fe, Mn, Zn, Cu, Ni, Cr, Pb, and As, were measured in the period from 2013 to 2019. The Spearman correlation and heatmap cluster analysis were utilized to determine the origin of pollution and the factors that control surface water quality. Several indices, such as the heavy metal pollution index (HPI), metal index (MI), hazard quotient oral and dermal (HQ), hazard index oral and dermal (HI), and carcinogenic risk (CR), were conducted to evaluate the potential risks for the environment and human health. The values of the HPI were between the range of 15 < HPI < 30, which indicated moderate pollution; however, the MI results showed high pollution in Dunaföldvár and Hercegszántó cities. The ecological risk (RI < 30) and HI values (< 1) showed low environmental risks and non-carcinogenic impacts of the existing metals, either on adults or children. The mean CR value of oral arsenic was 2.2E-04 and 2.5E-04 during April-September and October-March, respectively, indicating that children were the most vulnerable to arsenic-carcinogenic oral effects. While lead's CR oral values for children during April-September exceeded the threshold of 1.0E-04, chromium's oral and dermal CR values for both adults and children were 2.08E-04, 6.11E-04, 1.97E-04, and 5.82E-04 during April-September and October-March, respectively. These results demonstrate the potential carcinogenic risks related to chromium exposure within the two pathways in Hungary and highlight the need for effective measures to mitigate these risks.

Ecological and human health risk assessment of potentially toxic elements in water and soils within a crude oil waste management facility, Southwestern Ghana

Crude oil waste management is challenging due to the diverse constituents of the waste and its consequent impact on valued environmental receptors (water and soil). Characterization of the potentially toxic elements (PTEs) in soils and water within the surroundings of crude oil waste management facility is imperative, to aid evaluation of potential risks. The study assessed the potential environmental and human health risks posed by PTEs in soil and water from surroundings and adjoining settlement communities. A total of forty-four (44) samples were analyzed for PTEs (Cr, Pb, Zn, Co, Mn, Ni, Hg, Fe, As, Cu, Hg, and Cd) and physicochemical properties in both matrices. The total carcinogenic risk (TCR) for adults and children in the neighbouring community was 4.73 × 10-6 and 1.2 × 10-4, respectively, which was due to the high carcinogenic slope factor of arsenic. A strong correlation was observed between the PTEs and physicochemical properties, and their health risk was attributed to both geogenic and anthropogenic factors. The study indicated that the human health and ecological risk values obtained were within acceptable limits, with the waste management facility posing a higher risk in comparison to the nearby community. These risks may be attributed to the specific nature and intensity of the activities conducted at the facility. Hence, there is the need for continuous promotion of occupational and public awareness on the health and environmental impact of crude oil waste management.

The impact of maize straw incorporation on arsenic and cadmium availability, transformation and microbial communities in alkaline-contaminated soils

Increasing evidence of the uncertainty of crop straw returning in heavy metal-contaminated soil is a significant concern. The present study investigated the influence of 1 and 2% maize straws (MS) amendment on As and Cd bioavailability in two different alkaline soils (A-industrial and B-irrigation) after 56 days of ageing. Adding MS to the two soils decreased the pH by 1.28 (A soil) and 1.13 (B soil) and increased the concentration of dissolved organic carbon (DOC) by 54.40 mg/kg (A soil) and 100.00 mg/kg (B soil) during the study period. After 56 days of ageing, the overall NaHCO3-As and DTPA-Cd increased by 40% and 33% (A) and 39% and 41% (B) soils, respectively. The MS additions increased the alteration of As and Cd exchangeable and residual fractions, whereas advanced solid-state 13C nuclear magnetic resonance (NMR) revealed that alkyl C and alkyl O-C-O in A soil and alkyl C, Methoxy C/N-alkyl, and alkyl O-C-O in B soil significantly contributed to the As and Cd mobilisation. Collectively, 16 S rRNA analyses revealed Acidobacteria, Firmicutes, Chloroflexi, Actinobacteria and Bacillus promoted the As and Cd mobilisation following the MS addition, while principle component analysis (PCA) demonstrated that bacterial proliferation significantly influenced MS decomposition, resulting in As and Cd mobilisation in the two soils. Overall, the study highlights the implications of applying MS to As- and Cd-contaminated alkaline soil and offers the framework for conditions to be considered during As- and Cd-remediation efforts, especially when MS is the sole remediation component.

Effects of cadmium exposure on metabolism, antioxidant defense, immune function, and the hepatopancreas transcriptome of Cipangopaludina cathayensis

Cadmium (Cd) is a common contaminant in aquatic environments. However, little is known about the mechanisms underlying Cd toxicity in the freshwater snail Cipangopaludina cathayensis (Heude, 1890). This study to investigate the toxic effects of Cd on the standard metabolism, antioxidant activities, immune function, and hepatopancreas transcriptome profiles of C. cathayensis. C. cathayensis was exposed to 0.25, 0.5, 1.0, or 1.5 mg/L Cd for 3 h, with results showing that Cd significantly inhibited oxygen consumption and ammonia excretion and disrupted the respiratory metabolism of C. cathayensis. In addition, the O:N ratio dropped below 7, indicating that C. cathayensis may rely exclusively on proteins as an energy source under Cd stress. To understand how Cd impacts the antioxidant activities, immune function, and transcriptional profiles, C. cathayensis were exposed to 0.5 (low exposure, L14) or 1.5 (high exposure, H14) mg/L Cd for 14 days. Our results indicate that Cd exposure leads to oxidative stress and immunosuppression, with the latter effect being larger for exposure to higher Cd concentrations. A total of 2172 differentially expressed genes (DEGs) were identified by transcriptome analysis of the hepatopancreas, of which 885 were upregulated and 1287 were downregulated. Gene ontology and KEGG analyses revealed that the DEGs in the H14 group are enriched for energy generation terms and the "oxidative phosphorylation" pathway, respectively. Therefore, up-regulation of energy metabolism may be an adaptive strategy under Cd stress. Moreover, several genes involved in antioxidant activity were downregulated, whereas genes related to reactive oxygen species generation were upregulated. In addition, many immunity-related genes were identified within the DEGs, indicating that Cd toxicity may affect immune defense. Further, DEGs in the H14 group were enriched for disease-associated pathways. Taken together, our results indicate that Cd exposure leads to metabolic disorders, oxidative stress, and immunosuppression and thus may potentially contribute to disease outbreaks.

Trace metals in surface water of the Pechora River and its tributaries: Content, water quality and risks assessment (Arctic Ocean basin)

The article is devoted to the study of trace metals content in the Pechora River and its tributaries, which is the largest river in the Arctic Ocean basin. The study of physico-chemical properties of water showed aerobic conditions of low-mineralised water with pH values suitable for drinking water. Analysis of the content of trace metals has revealed that the main flow of Al, Mn, Co, Cu, Zn, V, As, Mg and Fe into the Pechora River comes from its tributaries. The average content of Cr, Mn, Cu, Zn, Pb, V, As, Mg and Fe in the water of the Pechora River delta was higher than for the main river channel, which indicates the transfer of a large mass of trace metals to the Barents Sea and the Arctic water ecosystem. For the studied river and tributaries, chronic pollution of the Pechora River with Al, Mn, Ba, Fe, Cu, U and Pb metals has adverse effects on waterborne organisms. The degree of contamination of natural waters by metals has been assessed using water quality indices (TMPI, TMEI, TMTI) and public health risks (HI and CR). Low contamination and weak toxicity of the Pechora River water has been determined, but serious contamination, toxicity and high non-carcinogenic risk of some of its tributaries have been observed. A high carcinogenic risk has been established for the consumption of all water sampled. Al, Ni, As, Fe, Mn, Cr, Cd, and Ba were found to be the highest priority contaminating trace metals. At present, contamination of the Pechora River and its tributaries with trace metals is formed under the influence of dissolution processes of rocks of the Ural Mountains, the Taminsky Ridge, underlying mineral deposits, permafrost degradation processes and glacier melting. Anthropogenic factors include oil and gas production and transportation.

Detrimental influence of industrial effluents, especially heavy metals, on limnological parameters of water and nutritional profile in addition to enzymatic activities of fish, Sperata seenghala (Sykes, 1839) from diverse Ramsar sites, India (Punjab)

The present research was designed to determine the nutritive value of the liver and intestine of fish, Sperata seenghala, the impact of effluence load on limnological parameters of water and proximate composition of fish organs, especially on fatty acids, liver enzymatic activities, seasonal variations in the nutritional profile of fish, and to check and compare the pollution status of Ramsar sites in Punjab by calculating the water quality index, heavy metal pollution index, and metal index from June 2018 to August 2020. WQI of Harike wetland was found to be 53.95, which depicts that water quality in this region is "poor". At Nangal wetland, water quality index was reported to be "excellent" quality water and fit for the whole ecological unit. Overall heavy metal pollution index for Harike wetland was reported 174.569, whereas for Nangal wetland it was 5.994, depicting massive contaminant loads in a polluted region. MI value was also recorded as being higher (6.9336) in polluted habitat than in control habitat (0.8175). In fish liver, significant (p < 0.05) higher mean total lipids (6.73%), total proteins (3.98%), moisture (77.69%), ash (3.56%), and carbohydrates (3.79%) were observed in the samples from Nangal wetland than Harike wetland. A similar trend was reported in all biochemical contents of the fish intestine. Enzyme activities such as aspartate-aminotransferase and alanine-aminotransferase were significantly elevated (p < 0.05) in the specimens collected from the polluted region. The mean total n-3 (except in spring), n-6 polyunsaturated fatty acids (except in winter), and average monounsaturated and saturated fatty acids diminished significantly (p < 0.05) in the liver of fish from contaminated habitat than control site. In the intestine of fish collected from the polluted region, significant reductions in the mean total n-3 (except in autumn as well as summer), total n-6 PUFAs (in autumn and winter), and total SFAs were reported than control site.

Influences of chronic copper exposure on intestinal histology, antioxidative and immune status, and transcriptomic response in freshwater grouper (Acrossocheilus fasciatus)

Copper (Cu) contamination is commonly found in both natural water environments and fish farms, and it can cause severe damage to different fish organs, but Cu-induced intestinal damage has been rarely studied. This study subjected three groups of freshwater grouper (Acrossocheilus fasciatus) (initial weight: 1.56 ± 0.10 g) to 0 mg/L, 0.01 mg/L, and 0.04 mg/L Cu2+ for 30 days, named Con, Cu0.01, and Cu0.04 groups, respectively. The histological observation indicated that the Cu0.04 group caused a significant decrease in villus length, lamina propria width, and muscular thickness compared to the Con group (P < 0.05). Additionally, the Cu0.04 group significantly increased intestinal superoxide dismutase (SOD), glutathione peroxidase (GPx), lysozyme (LZM) activities, as well as malondialdehyde (MDA) content than the Con group (P < 0.05). Meanwhile, the Cu0.01 and Cu0.04 groups showed significantly increased immunoglobulin M (IgM), complement 3 (C3), and glutathione (GSH) contents than the Con group (P < 0.05). Transcriptomic analysis revealed a total of 101 differentially expressed genes (DEGs), including 47 up-regulated and 54 down-regulated DEGs, were identified between the Cu0.04 and Con groups. Notably, the DEGs were mainly related to intestinal structure construction, immune functions, apoptosis, and resistance to DNA damage and pathogen infection. The findings suggest that chronic Cu exposure caused intestinal histological alterations, activated the antioxidative and immune systems, and induced systematic adaptation to cope with the physical barrier injury, DNA damage, and potential pathogen growth.

Dietary berberine against intestinal oxidative stress, inflammation response, and microbiota disturbance caused by chronic copper exposure in freshwater grouper (Acrossocheilus fasciatus)

Berberine (BBR) is known for its strong antioxidant, anti-inflammatory, and capacity to preserve intestinal microbiota balance in fish. This study aimed to investigate the protective effects of berberine against copper-induced toxicity in the intestine of freshwater grouper Acrossocheilus fasciatus. The experiment involved four groups: a control group, a Cu group exposed to 0.02 mg/L Cu²⁺, and two BBR groups fed with 100 or 400 mg/kg of berberine diets and exposed to the same Cu²⁺ concentration. Three replicates of healthy fish (initial weight 1.56 ± 0.10 g) were subjected to their respective treatments for 30 days. Results showed that none of the treatments significantly affected the survival rate, final weight, weight gain, and feed intake (P > 0.05). However, supplementation with 100 and 400 mg/kg of BBR significantly lowered the antioxidant activities, and glutathione peroxidase (gpx) and superoxide dismutase (sod) expression levels, as well as reduced malondialdehyde (MDA) content caused by Cu²⁺ exposure (P < 0.05). Berberine inclusion significantly downregulated proinflammatory factors NLR family pyrin domain containing 3 (nlrp3), interleukin 1 beta (il1β), interleukin 6 cytokine family signal transducer (il6st) but upregulated transforming growth factor beta 1 (tgfβ1) and heat shock 70kDa protein (hsp70) expression. Moreover, berberine at both levels maintained the intestinal structural integrity and significantly improved gap junction gamma-1 (gjc1) mRNA level compared to the Cu group (P < 0.05). Based on 16S rDNA sequencing, the richness and diversity of intestinal microbiota in different groups were not significantly influenced. Berberine reduced the Firmicutes/Bacteroidota ratio and stifled the growth of some specific pathogenic bacteria such as Pseudomonas, Citrobacter, and Acinetobacter, while boosting the richness of potential probiotic bacteria, including Roseomonas and Reyranella compared with the Cu group. In conclusion, berberine showed significant protective effects against Cu²⁺-induced intestinal oxidative stress, inflammation response, and microbiota disturbance in freshwater grouper.

Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review

Heavy metal contamination of water sources has emerged as a major global environmental concern, threatening both aquatic ecosystems and human health. Heavy metal pollution in the aquatic environment is on the rise due to industrialization, climate change, and urbanization. Sources of pollution include mining waste, landfill leachates, municipal and industrial wastewater, urban runoff, and natural phenomena such as volcanic eruptions, weathering, and rock abrasion. Heavy metal ions are toxic, potentially carcinogenic, and can bioaccumulate in biological systems. Heavy metals can cause harm to various organs, including the neurological system, liver, lungs, kidneys, stomach, skin, and reproductive systems, even at low exposure levels. Efforts to find efficient methods to remove heavy metals from wastewater have increased in recent years. Although some approaches can effectively remove heavy metal contaminants, their high preparation and usage costs may limit their practical applications. Many review articles have been published on the toxicity and treatment methods for removing heavy metals from wastewater. This review focuses on the main sources of heavy metal pollution, their biological and chemical transformation, toxicological impacts on the environment, and harmful effects on the ecosystem. It also examines recent advances in cost-effective and efficient techniques for removing heavy metals from wastewater, such as physicochemical adsorption using biochar and natural zeolite ion exchangers, as well as decomposition of heavy metal complexes through advanced oxidation processes (AOPs). Finally, the advantages, practical applications, and future potential of these techniques are discussed, along with any challenges and limitations that must be considered.

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

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

Heavy metal fraction, pollution, and source-oriented risk assessment in biofilms on a river system polluted by mining activities

The Lanping Pb-Zn mine is the largest source of Pb and Zn ores in China, thus posing a great threat to local ecosystems and human health. A total of seven heavy metals (Zn, Pb, Ni, Cu, Cr, Cd, and As) in the Bijiang River near the Pb-Zn mine were measured in winter and summer to assess their spatial-temporal enrichment, ecological risk, and source-oriented health risk in periphytic biofilms. Positive matrix factorization (PMF) receptor model and clustering analysis were used to quantitatively identify pollution sources. The results of PMF were then imported into the health risk assessment to further determine the carcinogenic and noncarcinogenic risks of various pollution sources. The results indicated distinct seasonal patterns in metal concentrations, with much higher concentrations in winter. Sites near the Pb-Zn mine tailing reservoir exhibited higher metal contamination levels than other sites. A strong correlation between the enrichment factor and the levels of nonresidual fraction suggested that anthropogenic inputs were the main source of these metals. Mining industries (Cd, Zn, and Pb), natural sources (As, Ni, and Cu), and agricultural activities (Cr) were the primary sources of heavy metal pollution in biofilms, accounting for 44.43%, 33.32%, and 22.26% of the total metal accumulation, respectively. Moreover, the carcinogenic and noncarcinogenic risks via dermal contact of the studied elements in biofilms were typically acceptable. Notably, as concentration was the main factor influencing these risks in children and adults. This study provides evidence that natural epilithic periphyton may be a potential metal biomonitor in aquatic systems and provide supporting information for effective source regulation.

Copper-mediated shifts in transcriptomic responses of intestines in Bufo gargarizans tadpoles to lead stress

The differential transcriptomic responses of intestines in Bufo gargarizans tadpoles to Pb alone or in the presence of Cu were evaluated. Tadpoles were exposed to 30 μg/L Pb individually and in combination with Cu at 16 or 64 μg/L from Gosner stage (Gs) 26 to Gs 38. After de novo assembly, 105,107 unigenes were generated. Compared to the control group, 7387, 6937, and 11139 differentially expressed genes (DEGs) were identified in the treatment of Pb + Cu0, Pb + Cu16, and Pb + Cu64, respectively. In addition, functional annotation and enrichment analysis of DEGs revealed substantial transcriptional reprogramming of diverse molecular and biological pathways were induced in all heavy metal treatments. The relative expression levels of genes associated with intestinal epithelial barrier and bile acids (BAs) metabolism, such as mucin2, claudin5, ZO-1, Asbt, and Ost-β, were validated by qPCR. This study demonstrated that Pb exposure induced transcriptional responses in tadpoles, and the responses could be modulated by Cu.

Ecological risk assessment of trace elements (TEs) pollution and human health risk exposure in agricultural soils used for saffron cultivation

Contamination of farmland soils by trace elements (TEs) has become an international issue concerning food safety and human health risks. In the present research, the concentrations of TEs including cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn) and iron (Fe) in soils of 16 farmlands were determined in Gonabad, Iran. In addition, the human health risks due to exposure to the TEs from the soils were assessed. Moreover, the soil contamination likelihood was evaluated based on various contamination indices including contamination factor [Formula: see text]), enrichment factor (EF), geo-accumulation index (Igeo), and pollution load index (PLI) calculations. The soil mean concentrations for Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn and Fe ranges as 0.102, 6.968, 22.550, 29.263, 475.281, 34.234, 13.617, 54.482 and 19,683.6 mg/kg in farmland soils. The mean concentrations of the TEs decreased in the order of Fe > Mn > Zn > Ni > Cu > Cr > Pb > Co > As > Cd. Levels of all metals in this study were within the FAO/WHO and Iranian soil standards. The HQ values from investigated elements for adults and children in the studied farms were less than the limit of 1, indicating no health risks for the studied subpopulations. The results of the present research indicated no significant carcinogenic health hazards for both adults and children through ingestion, skin contact and inhalation exposure routes. [Formula: see text] values of Ni and Zn in 100% and 6.25% of farmlands were above 1, showing moderate contamination conditions. EF values of metals in farmlands were recorded as "no enrichment", "minimal enrichment" and "moderate enrichment" classes. Furthermore, it can be concluded that the all farms were uncontaminated except Ni (moderately contaminated) based on Igeo. This is an indication that the selected TEs in the agricultural soils have no appreciable threat to human health.

Adsorption and Removal of Cr6+, Cu2+, Pb2+, and Zn2+ from Aqueous Solution by Magnetic Nano-Chitosan

Magnetic nano-chitosan (MNC) was prepared and characterized. The kinetics, thermodynamics, and influencing factors of the adsorption of Cr6+, Cu2+, Pb2+, and Zn2+, as well as their competitive adsorption onto MNC in aqueous solution, were studied. The results showed that the adsorption kinetics and thermodynamics of Cr6+, Cu2+, Pb2+, and Zn2+ were well described by the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, indicating that the adsorption was mainly chemical adsorption and endothermic. Increasing the dosage of MNC, the equilibrium adsorption capacity (qe) of Cr6+, Cu2+, Pb2+, and Zn2+ decreased; their removal rate (η) increased. With the increase in the solution’s pH, the qe and η of Cr6+ first increased and then decreased; the qe and η of Cu2+, Pb2+, and Zn2+ increased. With the increase in the metal ion initial concentration, the qe increased; the η of Cr6+, Cu2+, and Zn2+ decreased, while the η of Pb2+ increased first and then decreased. Temperature had a weak influence on the qe of Cr6+ and Pb2+, while it had a strong influence on Cu2+ and Zn2+, the qe and η were greater when the temperature was higher, and the adsorption was spontaneous and endothermic. The qe and η of Cu2+, Pb2+, and Zn2+ decreased in the presence of co-existing ions. The influences among metal ions existed in a binary and ternary ion system. The current study’s results provide a theoretical support for the simultaneous treatment of harmful metal ions in wastewater by MNC.

Sentinel animals for monitoring the environmental lead exposure: combination of traditional review and visualization analysis

In nature, certain animals share a common living environment with humans, thus these animals have become biomonitors of health effects related to various environmental exposures. As one of the most toxic environmental chemicals, lead (Pb) can cause detriment health effects to animals, plants, and even humans through different exposure pathways such as atmosphere, soil, food, water, and dust, etc. Sentinel animals played an "indicative" role in the researches of environmental pollution monitoring and human health. In order to comprehend the usage of sentinel animals in the indication of environmental Pb pollution and human Pb exposure completely, a combination of traditional review and visualization analysis based on CiteSpace literature was used to review earlier researches in this study. In the first instance, present researches on exposure sources and exposure pathways of Pb were summarized briefly, and then the studies using sentinel animals to monitor environmental heavy metal pollution and human health were combed. Finally, visualization software CiteSpace 5.8.R3 was used to explore and analyze the hotspots and frontiers of lead exposure and sentinel animals researches at home and abroad. The results showed that certain mammals were good indicators for human lead exposure. Sentinel animals had been widely used to monitor the ecological environment and human lead exposure. Among them, the blood lead levels of small mammals, particularly for domestic dogs and cats, had a significant correlation with the blood lead levels of human living in the same environment. It indicated that certain biological indicators in animals can be used as surrogates to monitor human body exposure to heavy metals. This study also explored the challenges and perspectives that may be faced in sentinel animal research, in order to provide a certain theoretical basis and train of thought guidance for future research.

Impact of Textile Industries on Surface Water Contamination by Sb and Other Potential Toxic Elements: A Case Study in Taihu Lake Basin, China

Contamination of industry-derived antimony (Sb) is currently of great concern. This study was conducted to identify the source of Sb together with other potential toxic elements (PTEs) in a typical industrial area in China and emphasize the contribution of Sb to ecological risk in the local aquatic environment. By investigating the distribution of nine PTEs in surface water in Wujiang County in dry and wet seasons, this study revealed that textile wastewater was the main source of Sb. The distribution of Sb (0.48~21.4 μg/L) showed the least seasonal variation among the nine elements. Factor analysis revealed that the factor that controlled Sb distribution is unique. In general, Sb was more concentrated in the southeastern part of the study area where there was a large number of textile industries, and was affected by the specific conductivity and total dissolved solids in water (p < 0.01). Sb concentration in 35.71% of samples collected from the drainage outlet exceeded the standard limit of 10 μg/L. Results from three pollution assessment methods suggested that >5% of the sampling sites were slightly too heavily polluted and Sb contributed the most. Therefore, it is necessary to strengthen the administrative supervision of local textile enterprises and elevate the local standard of textile wastewater emission.

Assessment of water quality, trace metal pollution, source apportionment and health risks in the groundwater of Chakwal, Pakistan

Groundwater quality evaluation is the main concern in the regions like Chakwal where it is major source of water for drinking and irrigation due to low storage capacity of the surface water and lack of proper irrigation system. The aim of the present study was to evaluate various physicochemical parameters (pH, EC, TDS, DO, TA, TH and chlorides) and selected essential/toxic trace metal concentrations (Na, K, Ca, Mg, Sr, Li, Ag, Zn, Fe, Cu, Co, Mn, Cr, Cd, and Pb) in order to explore their distribution, correlation, spatial variations and health risk assessment. Average concentration of some trace metals (Co, Cd and Pb) and physicochemical parameters (EC, TDS, and alkalinity) were found to exceed the national/international standards. Multivariate methods of analysis showed strong associations among Fe-Li-K, Sr-Mg-Ca, Cd-Mn, Cu-Zn, Ag-Co, and Cr-Pb-Na which were significantly contributed by anthropogenic activities. Irrigation water quality index exhibited intermediate suitability of the groundwater for irrigation purpose. Health risk evaluation of the trace metals revealed significant non-carcinogenic risks for Cd, Co and Pb (HQ_ing > 1) especially for children. Similarly, significant carcinogenic risk was found to be associated with Pb and Cr which exceeded the safe limit, suggesting the lifetime carcinogenic risk associated with these metals in the groundwater. The present health risk problems should be considered on top priority and immediate actions should be taken to safeguard the water quality in the study area.

Effects of single and combined exposure to zinc and two tetracycline antibiotics on zebrafish at the early stage

Tetracycline antibiotics (TCs) and heavy metals are commonly used in livestock and poultry farming, leading to their coexistence in the aquatic environment. This coexistence causes combined toxicity to aquatic organisms. Here, zebrafish embryos were exposed to chlortetracycline (CTC), oxytetracycline (OTC), zinc chloride (ZnCl₂), and their combinations for 120 h to evaluate their adverse effects on the growth, antioxidant system, immune system, and endocrine system during the early stage of life. OTC/ZnCl₂ combined exposure significantly reduced the body weight, whereas the TCs/ZnCl₂ combination significantly increased the heart rate of zebrafish larvae, suggesting growth impairment induced by TCs and ZnCl₂. Further, combined groups showed more prominent toxicity to the antioxidant system than single groups, as revealed by related levels of enzyme activity and gene expression. In addition, the levels of most pro-inflammatory genes were downregulated, and those of NF-κB-related genes were upregulated in all treatment groups, indicating an immunosuppressive response and the potential role of NF-κB signaling, while the combined treatment was not more toxic than TCs or ZnCl₂ alone. Similarly, hormone and endocrine related gene levels were determined. Although both single and combined exposures caused certain endocrine-disrupting effects, the combined exposure did not result in higher toxicity than a single exposure. Our findings showed that a mixture of TCs and ZnCl₂ might exert greater toxic effects as compared to a single compound on some systems, providing fundamental data on the toxic effects of single and combined TC and ZnCl₂ exposure on aquatic organisms, although studies are needed to explore the underlying mechanisms.

Effects of COVID-19 era on a subtropical river basin in Bangladesh: Heavy metal(loid)s distribution, sources and probable human health risks

The COVID-19 era has profoundly affected everyday human life, the environment, and freshwater ecosystems worldwide. Despite the numerous influences, a strict COVID-19 lockdown might improve the surface water quality and thus provide an unprecedented opportunity to restore the degraded freshwater resource. Therefore, we intend to investigate the spatiotemporal water quality, sources, and preliminary health risks of heavy metal(loid)s in the Karatoya River basin (KRB), a tropical urban river in Bangladesh. Seventy water samples were collected from 35 stations in KRB in 2019 and 2022 during the dry season. The results showed that the concentrations of Ni, Cu, Zn, Pb, Cd, and Cr were significantly reduced by 89.3-99.7 % during the post-lockdown period (p < 0.05). However, pH, Fe, Mn, and As concentrations increased due to the rise of urban waste and the usage of disinfectants during the post-lockdown phase. In the post-lockdown phase, the heavy metal pollution index, heavy metal evaluation index, and Nemerow's pollution index values lessened by 8.58 %, 42.86 %, and 22.86 %, respectively. Besides, the irrigation water quality indices also improved by 59 %-62 %. The total hazard index values increased by 24 % (children) and 22 % (adults) due to the rise in Mn and As concentrations during the lockdown. In comparison, total carcinogenic risk values were reduced by 54 % (children) and 53 % (adults) in the post-lockdown. We found no significant changes in river flow, rainfall, or land cover near the river from the pre to post-lockdown phase. The results of semivariogram models have demonstrated that most attributes have weak spatial dependence, indicating restricted industrial and agricultural effluents during the lockdown, significantly improving river water quality. Our study confirms that the lockdown provides a unique opportunity for the remarkable improvement of degraded freshwater resources. Long-term management policies and regular monitoring should reduce river pollution and clean surface water.

Characterization and health risk assessment of arsenic in natural waters of the Indus River Basin, Pakistan

The elevated concentrations of arsenic in natural water are one of the major environmental threats to human health. However, the existing characteristics, controlling mechanisms, and associated risks of arsenic in natural waters in the Indus River Basin (IRB), Pakistan, are yet to be unequivocally understood. In this study, a total of 203 samples of surface water (SW), shallow groundwater (SGW), and deep groundwater (DGW) were collected from the IRB to assess the geochemical characteristics of arsenic and its associated health risks, as all three kinds of waters are the main sources of drinking and domestic usage. The results revealed that the arsenic concentrations in the SW, SGW, and DGW were in the ranges of 1.1-26.45, 1.05-44.44, and 0.67-41.09 μg L^-1, respectively. Furthermore, the predominance of As (V) (97 %) over As(III) (3 %) confirmed that the desorption of As in oxidizing environments with elevated pH and Eh is the controlling mechanism. The hazard quotient of 11-45 % and 20-60 % samples and cancer risk of 26-64 % and 26-68 % samples indicated high health risks for the adults and children, respectively, suggesting an immense need for appropriate measures of reducing natural water arsenic concentrations in IRB from the human health perspectives.

Lead and copper led to the dysregulation of bile acid homeostasis by impairing intestinal absorption in Bufo gargarizans larvae: An integrated metabolomics and transcriptomics approach

Bile acids, as metabolic regulators and signaling molecules, play key roles in the regulation of host metabolism and immune responses. Heavy metals such as lead (Pb) and copper (Cu) are widespread environmental pollutants that threaten public health. However, the effects of heavy metals on bile acid metabolism and the underlying molecular mechanisms remain unclear, particularly for ecologically important amphibian species. In the present research, the effects of exposure to environmentally-relevant concentrations of Pb (250 μg/L), Cu (50 μg/L), and a mixture of both (Mix) on bile acid metabolism and the underlying molecular mechanisms in the intestines of Bufo gargarizans larvae were comprehensively investigated using histopathology, metabolomics and transcriptomics analysis. Our results suggested that Pb and/or Cu caused histopathological damage to the intestine and liver, such as decreased intestinal epithelial cell height and dilated hepatic sinusoid. The total bile acid level was decreased in the Pb and Mix exposure groups but elevated in the Cu treatment. A significant decrease in the ratio of conjugated to unconjugated bile acids was present in all treatment groups. Also, the level of GCA was increased while TCA and TCDCA were decreased in all exposure groups. In addition, exposure to Pb and Cu altered the expression levels of genes related to intestinal absorption. For example, mrp2, mrp3 and aqp4 had higher expression in the Pb and Mix treatment groups, and aqp1 and mrp4 were increased in the Cu treatment group. Overall, we speculated that the dysregulation of bile acid homeostasis induced by Pb and Cu exposure may be due to impaired intestinal absorption. These findings raise further concerns about the hazards of Pb and/or Cu in influencing bile acid metabolism that might lead to the development of metabolic diseases and inflammatory disorders.

Removal efficacy of fly ash composite filler on tailwater nitrogen and phosphorus and its application in constructed wetlands

Constructed wetlands (CWs) have been widely used in tailwater treatment. However, it is difficult to achieve considerable removal efficiency of nitrogen and phosphorus in tailwater solely by CWs-an efficient green wetland filler is also important. This study investigated 160 domestic sewage treatment facilities (DSTFs) in rural areas from two urban areas in Jiaxing for TP and NH₃-N and found that TP and NH₃-N concentrations in rural domestic sewage (RDS) in this plain river network are still high. Therefore, we selected a new synthetic filler (FA-SFe) to enhance nitrogen and phosphorus reduction, and we discuss the importance of filler in constructed wetlands. Experiments revealed the adsorption capacity of the new filler: the maximum adsorption amounts of TP and NH₃-N reached 0.47 g m^-2 d^-1 and 0.91 g m^-2 d^-1, respectively. The application potential of FA-SFe was verified in actual wastewater treatment, with the removal rates of ammonia nitrogen and TP reaching 71.3% and 62.7%, respectively. This study provides a promising pathway for nitrogen and phosphorus removal from rural tailwaters.