Hydrological distribution of physicochemical parameters and heavy metals in surface water and their ecotoxicological implications in the Bay of Bengal coast of Bangladesh

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.

Ecological and public health risk assessment of potentially toxic elements in the surface sediments of the Pasur river estuary, Bangladesh

Potentially toxic elements (PTEs) in the surface sediments of the Pasur river estuary was investigated to assess its distribution, potential sources, and current dangers to ecological and public health. The Pasur River is a tidal, meandering, perennial river in south-western Bangladesh with a considerable number of fisheries and industrial activities. Sediment samples were collected from seven sampling points from January to December 2022 to assess the contamination level of six potentially toxic elements (Pb, Cr, Cd, As, Cu and Zn). Flame Atomic Absorption Spectrophotometer was utilized to detect the concentration of PTEs by following some sequential analytical procedure. Concentration of PTEs followed the reducing trend of Zn > Cr > Pb > As > Cu > Cd with the mean value of 61.04 > 49.15 > 26.58 > 10.28 > 6.28 > 1.59 mg/kg, respectively. The principle component and cluster analyses justified the anthropogenic source of the studied PTEs. The mean values of contamination factor (CF), geo-accumulation index (Igeo) and enrichment factor (EFc) showed that Pb and Cd were highly responsible for sediment (uncontaminated to moderate) contamination. Pollution load index (PLI) indicated higher pollution of sediments near the port areas. Potential ecological risk index (PERI) indicated low to moderate risks due to the contaminated sediment. However, the contamination of sediment was not associated with the non-carcinogenic (HQderm and HI < 1) and carcinogenic (CRderm < 10-6) risks due to the dermal contact. Although the risks were within the tolerable limit, regular monitoring is suggested to reduce the risk of PTEs contamination.

Assessing metal(loid)s-Induced long-term spatiotemporal health risks in Coastal Regions, Bay of Bengal: A chemometric study

Despite sporadic and irregular studies on heavy metal(loid)s health risks in water, fish, and soil in the coastal areas of the Bay of Bengal, no chemometric approaches have been applied to assess the human health risks comprehensively. This review aims to employ chemometric analysis to evaluate the long-term spatiotemporal health risks of metal(loid)s e.g., Fe, Mn, Zn, Cd, As, Cr, Pb, Cu, and Ni in coastal water, fish, and soils from 2003 to 2023. Across coastal parts, studies on metal(loid)s were distributed with 40% in the southeast, 28% in the south-central, and 32% in the southwest regions. The southeastern area exhibited the highest contamination levels, primarily due to elevated Zn content (156.8 to 147.2 mg/L for Mn in water, 15.3 to 13.2 mg/kg for Cu in fish, and 50.6 to 46.4 mg/kg for Ni in soil), except for a few sites in the south-central region. Health risks associated with the ingestion of Fe, As, and Cd (water), Ni, Cr, and Pb (fish), and Cd, Cr, and Pb (soil) were identified, with non-carcinogenic risks existing exclusively through this route. Moreover, As, Cr, and Ni pose cancer risks for adults and children via ingestion in the southeastern region. Overall non-carcinogenic risks emphasized a significantly higher risk for children compared to adults, with six, two-, and six-times higher health risks through ingestion of water, fish, and soils along the southeastern coast. The study offers innovative sustainable management strategies and remediation policies aimed at reducing metal(loid)s contamination in various environmental media along coastal Bangladesh.

From ground to gut: Evaluating the human health risk of potentially toxic elements in soil, groundwater, and their uptake by Cocos nucifera in arsenic-contaminated environments

This study aimed to gauge the toxicity of potentially toxic elements (PTEs) in coconut crops cultivated in arsenic-contaminated areas while offering a global perspective encompassing more than 100 impacted countries. The current investigation provides crucial insights into the assessment of PTEs pollution using the Bioaccumulation factor, Geo-accumulation index, Potential ecological risk index, Hazardous index, and Lifetime cancer risk (LCR) and highlights the potential human health risks posed by contaminated food, water, and soil. From 22 severely polluted sites in West Bengal, India, soil, groundwater (GW), and coconut water (CW) samples were collected, acidified, and digested using microwave digestion, for PTEs quantification using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results revealed that despite high concentrations of arsenic in soils (4.6 ± 3.4 mg kg-1), and GW (22.2 ± 150.9 μg L-1), CW (0.7 ± 3.1 μg L-1) levels were within permissible limits. Groups of PTEs with comparable sources and distributions were discovered through Principal Component Analysis (PCA). A speciation diagram was used to predict the prevalence of arsenic species in all three matrices. The Hazardous Index (HI < 1) indicated no probability of non-carcinogenic diseases for children and adults in all the compartments. However, exposure to GW and soil contaminated with Cr, As, and Cd by children (9.02 × 10-13 to 2.77 × 10-4) and adults (6.51 × 10-14 to 1.18 × 10-4) would increase their susceptibility to cancer (LCR >10-6). The study concluded that moderate lifetime consumption of CW is safe and has no significant impact on healthy individuals. Additionally, CW is a rich source of essential micronutrients such as Zn, Fe, Mn, and B. Overall, the findings of this study could help in developing appropriate strategies for reducing PTEs contamination and protecting human health.

Toxicity of two pesticides in binary mixture on survival and enzymatic response of Cerastoderma edule - The warming influence

Pesticide application increased by about 1 million tonnes in the last 3 decades. Pesticides' overuse, coupled with the need for several pesticides to control different pests in the same crop, and its application many times per year, results in dangerous chemical cocktails that enter in aquatic systems, with impacts to the ecosystems and its communities. Climatic changes are currently another great concern, is predicted by the end of the 21st century, the earth's surface temperature will increase by about 4 °C. Bivalve species are reported as essential to the ecosystems' balance. However, they are also indicated as the organisms that will suffer the most serious effects of the temperature increase. So, this work intends to: a) verify the harm of the sub-lethal concentrations of two worldwide used pesticides, oxyfluorfen and copper (Cu), when combined, to Cerastoderma edule at 15 °C and 20 °C; b) assess the changes in the antioxidant defence system, the activity of the neurological enzyme acetylcholinesterase and the nutritive value of C. edule, after exposure to sub-lethal concentrations of oxyfluorfen and Cu, single and in the mixture, at 15 °C and 20 °C; c) observe the interaction between Cu and oxyfluorfen, considering the different biomarkers. Bivalves were exposed to oxyfluorfen and Cu, single and combined, for 96 h, at 15 °C and 20 °C. Results showed lethal effects to the organisms exposed at 20 °C when exposed to the highest binary mixture concentrations. Biochemical effects were observed on the organisms exposed to 15 °C, despite not observing any lethal effects. Briefly, there was a reported increase in oxidative stress and a decrease in protein content, regardless of the increase in the activity of antioxidant enzymes. These results suggest the potentially dangerous effects of the chemicals' mixture combined with the temperature, on this species and its consumers, impacting the trophic chain, and consequently, the community structure and function.

Trace metals and pesticides in water-sediment and associated pollution load indicators of Netravathi-Gurupur estuary, India: Implications on coastal pollution

Various environmental indicators were used to evaluate the water and sediment quality of the Netravathi-Gurupur estuary, India, for trace metals and pesticide pollution. The descended order of studied metal concentrations (μg/L) in the water was Fe (592.71) > Mn (98.35) > Zn (54.69) > Cu (6.64) > Cd (3.24) > Pb (2.38) > Cr (0.82) and in sediment (mg/kg) was Fe (11,396.53) > Mn (100.61) > Cr (75.41) > Zn (20.04) > Cu (12.77) > Pb (3.46) > Cd (0.02). However, pesticide residues were not detected in this estuarine environment. The various metal indexes categorised the water as uncontaminated, whereas contamination factor, enrichment factor, geo-accumulation index, degree of contamination and pollution load index indicated low to moderate sediment contamination. Multivariate statistics showed that the dominance of natural sources of trace metals with little anthropogenic impact. Improvement in water/sediment quality during the study period might be due to COVID-19 imposed lockdown.

Pollution status and ecological risks of metals in surface water of a coastal estuary and health risk assessment for recreational users

Since the areas close to the Sundarbans mangrove estuary, which is one of the most dynamic and productive ecosystems in the world, are very suitable for urban and industrial activities, the coastal areas of this ecosystem are constantly exposed to metal contamination. In this study, we analyzed the levels, spatial distributions, sources, pollution status, ecological risks, and health risks for recreational users of 16 metals in surface water collected from 18 sampling sites in the Sundarbans estuary. Considering the mean values of metals, Sr (2523 μg/L), Al (1731 μg/L), B (1692 μg/L) and Fe (1321 μg/L) were the most abundant metals in the coastal waters of the estuary, while Cd (0.977 μg/L), Ni (3.11 μg/L), Cu (5.98 μg/L) and Cr (9.77 μg/L) were the less abundant metals. All metals except Zr had the coefficient of variation (CV) values of over 35%, suggesting that other metals showed strong variation between sampling sites due to anthropogenic activities. Al, Fe and Pb levels of all sampling sites were above the limit values set for coastal and marine waters. Similarly, Pb levels of all sites exceeded the USEPA chronic criterion set for saltwater aquatic life. The results of pollution indices indicated that there was a serious metal pollution in almost all sampling sites. Low ecological risk (ER) at four sites, moderate ER at five sites and considerable ER at nine sites were recorded. Dual hierarchical clustering analysis grouped 16 metals into four clusters based on their potential sources and 18 sampling sites into three clusters based on their similar pollution characteristics. Health risk assessment results indicated that total hazard index (THI) values of all sites for recreational children were above the acceptable level of 1, indicating that water of all sites is not safe for health of children. However, THI values of all sites except ST8 (1.1) and ST11 (1.19) for recreational adults were below 1. Among the metals studied, Zr was found to be metal that contributes the most (75.89%) to total health risk in this coastal estuary. This finding reveals the necessity of monitoring of such less-studied metals such as Zr in the surface water of coastal estuaries. Carcinogenic risk values of As were within or below the acceptable range at all sites, indicating that carcinogenic risks would not be expected for recreational users.

Bioaccumulation and sources of metal(loid)s in fish species from a subtropical river in Bangladesh: a public health concern

Toxic metals and freshwater fish's metalloid contamination are significant environmental concerns for overall public health. However, the bioaccumulation and sources of metal(loids) in freshwater fishes from Bangladesh still remain unknown. Thus, the As, Pb, Cd, and Cr concentrations in various freshwater fish species from the Rupsha River basin were measured, including Tenualosa ilisha, Gudusia chapra, Otolithoides pama, Setipinna phasa, Mystus vittatus, Glossogobius giuris, and Pseudeutropius atherinoides. An atomic absorption spectrophotometer was used to determine metal concentrations. The mean concentrations of metal(loids) in the fish muscle (mg/kg) were found to be As (1.53) > Pb (1.25) > Cr (0.51) > Cd (0.39) in summer and As (1.72) > Pb (1.51) > Cr (0.65) > Cd (0.49) in winter. The analyzed fish species had considerably different metal(loid) concentrations with seasonal variation, and the distribution of the metals (loids) was consistent with the normal distribution. The demersal species, M. vittatus, displayed the highest bio-accumulative value over the summer. However, in both seasons, none of the species were bio-accumulative. According to multivariate statistical findings, the research area's potential sources of metal(loid) were anthropogenic activities linked to geogenic processes. Estimated daily intake, target hazard quotient (THQ), and carcinogenic risk (CR) were used to assess the influence of the risk on human health. The consumers' THQs values were < 1, indicating that there were no non-carcinogenic concerns for local consumers. Both categories of customers had CRs that fell below the permissible range of 1E - 6 to 1E - 4, meaning they were not at any increased risk of developing cancer. The children's group was more vulnerable to both carcinogenic and non-carcinogenic hazards. Therefore, the entry of metal(loids) must be regulated, and appropriate laws must be used by policymakers.

Contamination and ecological risk assessment of Cr, As, Cd and Pb in water and sediment of the southeastern Bay of Bengal coast in a developing country

Safe levels of heavy metals in the surface water and sediment of the eastern Bay of Bengal coast have not been universally established. Current study characterized heavy metals such as arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in surface water and sediments of the most important fishing resource at the eastern Bay of Bengal coast, Bangladesh. Both water and sediment samples were analyzed using inductively coupled plasma mass spectrometer. Considering both of the seasons, the mean concentrations of Cr, As, Cd, and Pb in water samples were 33.25, 8.14, 0.48, and 21.14 μg/L, respectively and in sediment were 30.47, 4.48, 0.20, and 19.98 mg/kg, respectively. Heavy metals concentration in water samples surpassed the acceptable limits of usable water quality, indicating that water from this water resource is not safe for drinking, cooking, bathing, and any other uses. Enrichment factors also directed minor enrichment of heavy metals in sediment of the coast. Other indexes for ecological risk assessment such as pollution load index (PLI), contamination factor (CF), geoaccumulation index (Igeo), modified contamination degree (mCd), and potential ecological risk index (PERI) also indicated that sediment of the coastal watershed was low contamination. In-depth inventorying of heavy metals in both water and sediment of the study area are required to determine ecosystem health for holistic risk assessment and management.

Pollution source identification of nitrogen and phosphorus in the lower West Main Canal, the Ganfu Plain irrigation district (South China)

The degradation of surface water quality has been a widespread concern around the world. However, irrigation canal water does not attract much attention although it is important to agriculture and population. In this study, a 5-year water quality monitoring of surface water was conducted in the lower West Main Canal of the Ganfu Plain irrigation district to identify the levels and pollution sources of nitrogen and phosphorus.Over 75% of samples had total phosphorus (TP) concentrations of > 0.02 mg/L, and all samples had total nitrogen (TN) concentrations of > 0.2 mg/L, indicating a risk of eutrophication. The concentrations of NO3--N and NH4+-N averagely occupied 57% and 18% of TN, respectively. PCA analysis showed that phosphorus and nitrogen in canal water were associated with meteorological factors, urban life and surface runoff, agricultural cultivation, livestock-poultry breeding, and water-sediment interaction in the wet season, whereas they were affected by meteorological factors, industrial effluent, urban domestic sewage, and livestock-poultry breeding in the dry season. Absolute principal component score-multiple linear regression (APCS-MLR) model results revealed that (1) agricultural cultivation plus livestock-poultry breeding contributed 43.2% of TP in canal water in the wet season, while livestock-poultry breeding contributed 52.9% in the dry season, and (2) domestic sewage plus surface runoff contributed 29.4% of TN in the wet season, while livestock-poultry breeding contributed 45.9% in the dry season. The unidentified sources had significant contributions of > 20% for almost all variables. So further investigations are required for determining unidentified sources, and anthropogenic pollution control is imperative for canal water quality protection.

Post-consumption waterpipe tobacco waste as an unrecognized source of toxic metal(loid)s leachates into aquatic environments

Waterpipe is a common form of tobacco smoking, and recently, its use has been increasing globally. Therefore, concern arises regarding the large quantity of post-consumption waterpipe tobacco waste produced and released into the environment and which can contain high levels of dangerous pollutants such as toxic meta(loid)s. This study reports the concentrations of meta(loid)s in waste from fruit-flavoured and traditional tobacco smoking as well as the release rate of these pollutants from waterpipe tobacco waste into three types of water. These include distilled water, tap water, and seawater and contact times ranging from 15 min to 70 days. The mean concentration levels of Ʃmetal(loid)s in waste samples of Al-mahmoud, Al-Fakher, Mazaya, Al-Ayan brands and traditional tobacco brands were 212 ± 92.8, 198 ± 94.4, 197 ± 75.7, 214 ± 85.8 and 40.6 ± 16.1 μg/g, respectively. The concentration levels of Ʃmetal(loid)s in fruit-flavoured tobacco samples were significantly higher than for traditional tobacco samples (p < 0.05). It was found that waterpipe tobacco wastes leached toxic metal(loid)s into different water samples with similar trends. In addition distribution coefficients showed that most metal(loid)s are highly likely to enter the liquid phase. The concentration levels of these pollutants (except Ni and As) in deionized water and tap water exceeded the surface fresh water standards for sustaining aquatic life during long contact time (up to 70 days). In seawater, concentration levels of Cu and Zn exceeded the recommended standards for maintaining aquatic life in the sea. Therefore, due to the possibility of contamination by soluble metal(loid)s through disposal of waterpipe tobacco waste in wastewater, there is concern that these toxic chemicals might enter the human food chain. Appropriate regulatory measures for disposal of waterpipe tobacco waste are necessary to prevent environmental pollution due to discarded wastes into aquatic ecosystems.

Ecotoxicological and biochemical effects of a binary mixture of pesticides on the marine diatom Thalassiosira weissflogii in a scenario of global warming

Under the current scenario of global warming, it is ecologically relevant to understand how increased temperature influences the combined toxicity of pesticides to aquatic species. Hence, this work aims to: a) determine the temperature effect (15 °C, 20 °C and 25 °C) on the toxicity of two pesticides (oxyfluorfen and Copper (Cu)), on the growth of Thalassiosira weissflogii; b) assess whether temperature affects the type of toxicity interaction between these chemicals; and c) assess the temperature effect on biochemical responses (fatty acids (FA) and sugar profiles) of the pesticides on T. weissflogii. Temperature increased the tolerance of the diatoms to the pesticides with EC₅₀ values between 3.176 and 9.929 μg L^-1 for oxyfluorfen and 42.50-230.75 μg L^-1 for Cu, respectively, at 15 °C and 25 °C. The mixtures toxicity was better described by the IA model, but temperature altered the type of deviation from dose ratio (15 °C and 20 °C) to antagonism (25 °C). Temperature, as well as the pesticide concentrations, affected the FA and sugar profiles. Increased temperature increased saturated FA and decreased unsaturated FA; it also affected the sugar profiles with a pronounced minimum at 20 °C. Results highlight effects on the nutritional value of these diatoms, with potential repercussion on food webs.

Ocean acidification induces tissue-specific interactions with copper toxicity on antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818)

Toxicity of contaminants in organisms under ocean acidification (OA) has attracted increasing attention in ecotoxicological studies. This study investigated how pCO₂-driven OA affected waterborne copper (Cu) toxicity in antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818). Clams were continuously exposed to Cu at ambient relevant (0/no metal exposure, 10 and 50 μg L^-1) and polluted-high (100 μg L^-1) concentrations in unacidified (pH 8.10) and acidified (pH 7.70/moderate OA and 7.30/extreme OA) seawater for 21 days. Following coexposure, metal bioaccumulation and responses of antioxidant defence-related biomarkers to OA and Cu coexposure were investigated. Results showed that metal bioaccumulation was positively correlated with waterborne metal concentrations but was not notably influenced by OA conditions. Both Cu and OA affected the antioxidant responses to environmental stress. Additionally, OA induced tissue-specific interactions with Cu on antioxidant defences, varying with exposure conditions. In unacidified seawater, antioxidant biomarkers were activated to defend against oxidative stress induced by Cu and prevented clams from lipid peroxidation (LPO or MDA), but failed to defend against DNA damage (8-OHdG). OA exacerbated Cu toxicity in antioxidant defences and increased LPO levels in tissues. Gills and viscera adopted adaptive antioxidant defence strategies to manage oxidative stress, with the former being more vulnerable to oxidative stress than the latter. MDA and 8-OHdG were sensitive to OA and Cu exposure, respectively, and were useful bioindicators for assessing oxidative stress. Integrated biomarker response (IBR) and PCA can reflect the integrative responses of antioxidant biomarkers to environmental stress and illuminate the contributions of specific biomarkers to antioxidant defence strategies. The findings provided insights for understanding antioxidant defences against metal toxicity in marine bivalves under OA scenarios, which is essential into managing wild populations.

Delving into the molecular initiating event of cadmium toxification via the dose-dependent functional genomics approach in Saccharomyces cerevisiae

Determining dose-response relationship is essential for comprehensively revealing chemical-caused effects on organisms. However, uncertainty and complexity of gene/protein interactions cause the inability of traditional toxicogenomic methods (e.g., transcriptomics, proteomics and metabolomics) to effectively establish the direct relationship between chemical exposure and genes. In this work, we built an effective dose-dependent yeast functional genomics approach, which can clearly identify the direct gene-chemical link in the process of cadmium (Cd) toxification from a genome-wide scale with wide range concentrations (0.83, 2.49, 7.48, 22.45, 67.34, 202.03 and 606.1 μM). Firstly, we identified 220 responsive strains, and found that 142, 110, 91, 34, 8, 0 and 0 responsive strains can be respectively modulated by seven different Cd exposure concentrations ranging from high to low. Secondly, our results demonstrated that these genes induced by the high Cd exposure were mainly enriched in the process of cell autophagy, but ones caused by the low Cd exposure were primarily involved in oxidative stress. Thirdly, we found that the top-ranked GO biological processes with the lowest point of departure (POD) were transmembrane transporter complex and mitochondrial respiratory chain complex III, suggesting that mitochondrion might be the toxicity target of Cd. Similarly, nucleotide excision repair was ranked first in KEGG pathway with the least POD, indicating that this dose-dependent functional genomics approach can effectively detect the molecular initiating event (MIE) of cadmium toxification. Fourthly, we identified four key mutant strains (RIP1, QCR8, CYT1 and QCR2) as biomarkers for Cd exposure. Finally, the dose-dependent functional genomics approach also performed well in identifying MIE for additional genotoxicity chemical 4-nitroquinoline-1-oxide (4-NQO) data. Overall, our study developed a dose-dependent functional genomics approach, which is powerful to delve into the MIE of chemical toxification and is beneficial for guiding further chemical risk assessment.

Metal contamination in soil and vegetables around Savar tannery area, Dhaka, Bangladesh: A preliminary study for risk assessment

Monitoring of heavy metal concentrations in soil and their accumulation in vegetables grown in the newly shifted tannery area of Savar, Bangladesh, is crucial for human health. Heavy metals (i.e., Cr, Pb, Cu, Zn, Ni, and Cd) concentrations in soil and vegetable samples were determined by atomic absorption spectrophotometer (AAS). In soil, 3220 mg/kg Cr was observed, which was 32-fold greater than the WHO/FAO recommended limit. Ecological risk indices such as the contamination factor, enrichment factor, pollution load index, and geoaccumulation index showed metal levels as moderately to very highly contaminated. The non-carcinogenic risk (NCR) was found to be higher, and the carcinogenic risk (CR) exceeded the acceptable value 1 × 10^-6 and posed greater risks to children than adults, especially for Cr in soil. The main exposure pathway for soil metals was 97.8-99.9% due to oral ingestion. The concentration of heavy metals especially Cr, Pb, Zn, and Cd, in vegetables was alarming as they crossed the safety limit. The calculated mean hazard index (8.71) for vegetable samples showed elevated levels of potential NCR, while CR for Cr and Cd, exceeded the acceptable limit of 1 × 10^-6, indicating the probability of cancer risk to humans through the consumption of vegetables. This study revealed a to-and-fro analysis of the present scenario of the tannery area, giving importance to human health and the environment.

pCO2-driven seawater acidification affects aqueous-phase copper toxicity in juvenile flounder Paralichthys olivaceus: Metal accumulation, antioxidant defenses and detoxification in livers

Ocean acidification potentially influences the biotoxicity of metals and the antioxidant defense systems of marine organisms. This study investigated how pCO₂-driven seawater acidification (SA) affected aqueous-phase copper (Cu) toxicity in the juvenile flounder Paralichthys olivaceus from the perspective of hepatic oxidative stress and damage to better understand the mechanisms underlying the biological effects produced by the two stressors. Fish were exposed to aqueous-phase Cu at relevant ambient and polluted concentrations (0, 5, 10, 50, 100 and 200 μg L^-1) at different pH levels (no SA: pH 8.10; moderate SA: pH 7.70, pCO₂ ∼1353.89 μatm; extreme SA: pH 7.30, pCO₂ ∼3471.27 μatm) for 28 days. A battery of biomarkers in the livers was examined to investigate their roles in antioxidant defense and detoxification in response to coexposure. Hepatic Cu accumulation (30.22-184.90 mg kg^-1) was positively correlated with Cu concentrations. The biomarkers responded adaptively to different redox states following SA and Cu exposure. In unacidified seawater, increases in Cu concentrations significantly induced hepatic lipid peroxidation (LPO, by up to 27.03 %), although compensatory responses in antioxidant defenses and detoxification were activated. Moderate SA helped maintain hepatic redox homeostasis and alleviated LPO through different defense strategies, depending on Cu concentrations. Under extreme SA, antioxidant-based defenses were activated to cope with oxidative stress at ambient-low Cu concentrations but failed to defend against Cu toxicity at polluted Cu levels, and LPO (by up to 63.90 %) was significantly induced. Additionally, thiols (GSH and MT) responded actively to cope with Cu toxicity under SA. SOD, CAT, EROD, and GST were also sensitively involved in defending against hepatic oxidative stress during coexposure. These findings highlight the notable interactive effects of SA and Cu and provide a basis for understanding antioxidant-based defenses in marine fish confronting environmental challenges.

Arsenic in the foodstuffs: potential health appraisals in a developing country, Bangladesh

The presence of highly poisonous arsenic (As) elements in food concerns humans and animals. In Bangladesh, arsenic-contaminated groundwater is frequently utilized for agricultural irrigation. This is a significant source of arsenic pollution in the human food chain. For the first time, we investigated the presence of total arsenic in various foodstuffs obtained from 30 distinct agricultural eco-zones of Bangladesh to understand human exposure to arsenic through the food chain in Bangladesh. The greatest and lowest As concentrations were reported in fish among the examined dietary items (0.55 mg/kg, fw) and fruit (0.0068 mg/kg, fw), respectively. The results show that arsenic consumption from daily diet and food with drinking water was estimated to be 0.0352 mg/day for rural residents and 0.2002 mg/day for urban residents, respectively. The highest target hazard quotients (THQ) of arsenic in the fish samples surpassed the allowable limit (> 1), proving that fish are the primary dietary items influencing the possible danger to health. However, the target cancer risk (TR) from nutritional arsenic consumption was likewise higher than tolerable. A value of 10^-4 indicates that Bangladeshi people are continuously exposed to arsenic, which has carcinogenic and non-carcinogenic dangers. Overall, our results highlight that people in Bangladesh are exposed to hazardous levels of arsenic throughout the food chain, which should be addressed to ensure the country's food safety.

Distribution, sources, and pollution levels of toxic metal(loid)s in an urban river (Ichamati), Bangladesh using SOM and PMF modeling with GIS tool

Indexical assessment coupled with a self-organizing map (SOM) and positive matrix factorization (PMF) modeling of toxic metal(loid)s in sediment and water of the aquatic environment provides valuable information from the environmental management perspective. However, in northwest Bangladesh, indexical and modeling assessments of toxic metal(loid)s in surface water and sediment are still rare. Toxic metal(loid)s were measured in sediment and surface water from an urban polluted river (Ichamati) in northwest Bangladesh using an atomic absorption spectrophotometer to assess distribution, pollution levels, sources, and potential environmental risks to the aquatic environment. The mean concentrations (mg/kg) of metal(loid)s in water are as follows: Fe (871) > Mn (382) > Cr (72.4) > Zn (34.2) > Co (20.8) > Pb (17.6) > Ni (16.7) > Ag (14.9) > As (9.0) > Cu (5.63) > Cd (2.65), while in sediment, the concentration follows the order, Fe (18,725) > Mn (551) > Zn (213) > Cu (47.6) > Cr (30.2) > Ni (24.2) > Pb (23.8) > Co (9.61) > As (8.23) > Cd (0.80) > Ag (0.60). All metal concentrations were within standard guideline values except for Cr and Pb for water and Cd, Zn, Cu, Pb, and As for sediment. The outcomes of eco-environmental indices, including contamination and enrichment factors and geo-accumulation index, differed spatially, indicating that most of the sediment sites were moderately to highly polluted by Cd, Zn, and As. Cd and Zn content can trigger ecological risks. The positive matrix factorization (PMF) model recognized three probable sources of sediment, i.e., natural source (49.39%), industrial pollution (19.72%), and agricultural source (30.92%), and three possible sources of water, i.e., geogenic source (45.41%), industrial pollution (22.88%), and industrial point source (31.72%), respectively. SOM analysis identified four spatial patterns, e.g., Fe-Mn-Ag, Cd-Cu, Cr-Pb-As-Ni, and Zn-Co in water and three patterns, e.g., Mn-Co-Ni-Cr, Cd-Cu-Pb-Zn, and As-Fe-Ag in sediment. The spatial distribution of entropy water quality index values shows that the southwestern area possesses "poor" quality water. Overall, the levels of metal(loid) pollution in the investigated river surpassed a critical threshold, which might have serious consequences for the river's aquatic biota and human health in the long run.

Hydrochemical appraisal of surface water from a subtropical urban river in southwestern Bangladesh using indices, GIS, and multivariate statistical analysis

The Gorai River is a significant river  in Bangladesh's southwestern region, where residents make great use of the water despite a lack of adequate and reliable information concerning water quality and pollution levels. Thus, the goal of this research was to examine the spatio-temporal variations in water quality and determine whether it was suitable for drinking, agriculture, industrial, or livestock purposes, as well as the influencing factors and potential sources of water pollution. Surface water samples were collected in wet and dry seasons from ten sampling sites, and twenty water quality parameters were evaluated. The results showed that some studied water quality parameters, e.g., temperature, electrical conductivity, alkalinity, and nitrate, exceeded the maximum allowable limit. Water quality index values exhibited that the water quality of all sampling sites was found to be poor to very poor during the wet season, while only St-4 and St-5 were found to be poor and the rest of the investigated sites were good category during the dry season. Based on sodium adsorption ratio, soluble sodium percentage, residual sodium carbonate, residual sodium bicarbonate, and permeability index values, it was depicted that river water was suitable for irrigation purposes, but when compared to Kelly's ratio (KR) and magnesium hazard ratio values, river water was found to be unfit for irrigation. Moreover, potential salinity (PS) and sodium-to-calcium activity ratio (SCAR) values allow the water as moderately suitable for use in irrigation purposes. Langelier saturation index (LSI) and aggressive index (AI) values revealed that the river water was under saturated to supersaturated and moderate to non-aggressive in nature. However, Ryznar stability index (RSI), Puckorius scaling index (PSI), and Larson-Skold index (LS) values describe whether the water was high or severely corrosive, signifying its inappropriateness for industrial consumption. Principal component analysis (PCA) analysis depicted that the fluctuations in water quality are mostly related to point and non-point contaminations, such as urban and industrial effluent discharged and agricultural runoff of fertilizers. Cluster analysis (CA) revealed relative geographical and seasonal changes in water quality, showing the impact of hydrological changes and contamination.

Integration of leave-one-out method and real-time live cell reporter array system to assess the toxicity of mixtures

The ever-increasing number of chemicals and complex mixtures demands a time-saving and cost-effective platform for environmental risk assessment. However, there is limit promising tool for evaluating the contribution of each component to the total toxicity effects of the mixture. Here, four widely distributed environmental pollutants with different mode-of-actions, i.e., cadmium chloride (Cd), nitrofurazone (NFZ), triclosan (TCS), and tris(2-chloroethyl) phosphate (TCEP), were selected as components of artificial mixture. Integration of leave-one-out method and high-dimensional live cell array system was used to explore relative contribution of each component from the mixture. A quaternary mixture (All_4_chems) and four ternary mixtures (Leave_Cd, Leave_NFZ, Leave_TCS and Leave_TCEP) were investigated by Escherichia coli (E. coli) live cell array system with 90 environmental stress genes modified by green fluorescent protein (GFP) expressing reporter vectors. E. coli cytotoxicity tests demonstrated that TCS has antagonism effect with other three chemicals (Cd, NFZ and TCEP), while it was additive effect in other three binary combinations. A total of 26, 23, 13, 31 and 23 genes were significantly altered with fold-change greater than 2 over the 4 h exposure by All_4_chems, Leave_Cd, Leave_NFZ, Leave_TCS and Leave_TCEP, respectively. Clustering analysis based on time-series gene expression patterns and transcriptional effect level index (TELI) showed that Leave_TCEP has similar profiles with All_4_chems, demonstrating TCEP has the least contribution among four components to the quaternary mixture. Leave_NFZ has the least number of significantly altered genes, implying NFZ has the largest toxicity effect contribution to the quaternary mixture. The relative contribution in different pathways indicated that Cd has the most contribution to the mixture in redox stress, while TCS has the least contribution in DNA stress pathway. Collectively, our results demonstrated the utility of high-dimensional toxicogenomics data and leave-one-out method in prioritizing the relative contribution of each component in mixture.

Assessment of the effects of COVID-19 lockdown period on groundwater quality of a significant rice land in an urban area of Türkiye

In the current research, the impact of the COVID-19 lockdown period on groundwater quality of Lower Meriç Plain (Thrace Region of Türkiye) was evaluated. Some significant nutrient characteristics (NO₃^-, NO₂^-, and PO₄^3-), salinity characteristics (EC, TDS, and salinity), and physical characteristics (temperature, DO, pH, and turbidity) were investigated in groundwater samples collected from 45 sampling points in pre-lockdown and lockdown periods. Water quality index (WQI) and nutrient pollution index (NPI), Pearson correlation index (PCI), cluster analysis (CA), one-way ANOVA test (OWAT), and factor analysis (FA) were applied to assess ecological risk. Excluding recorded statistical differences in temperature and DO due to climatic conditions (p < 0.05), levels of all the investigated water quality parameters show no statistically significant differences and no significant reduction in pollutants measured in the lockdown period. On the contrary, the WQI and NPI scores have increased between the rates of 4.76-27.10% during the lockdown period. In the lockdown period, although the reduction of industry or limited production of many industrial facilities reduced the inorganic contaminant releases to the environment, ongoing agricultural activities and domestic wastes caused to prevent the reduction of organic pollutants in groundwater of the region during the lockdown period.

Computational assessment of groundwater salinity distribution within coastal multi-aquifers of Bangladesh

The rising salinity trend in the country’s coastal groundwater has reached an alarming rate due to unplanned use of groundwater in agriculture and seawater seeping into the underground due to sea-level rise caused by global warming. Therefore, assessing salinity is crucial for the status of safe groundwater in coastal aquifers. In this research, a rigorous hybrid neurocomputing approach comprised of an Adaptive Neuro-Fuzzy Inference System (ANFIS) hybridized with a new meta-heuristic optimization algorithm, namely Aquila optimization (AO) and the Boruta-Random forest feature selection (FS) was developed for estimating the salinity of multi-aquifers in coastal regions of Bangladesh. In this regard, 539 data samples, including ten water quality indices, were collected to provide the predictive model. Moreover, the individual ANFIS, Slime Mould Algorithm (SMA), and Ant Colony Optimization for Continuous Domains (ACOR) coupled with ANFIS (i.e., ANFIS-SMA and ANFIS-ACOR) and LASSO regression (Lasso-Reg) schemes were examined to compare with the primary model. Several goodness-of-fit indices, such as correlation coefficient (R), the root mean squared error (RMSE), and Kling-Gupta efficiency (KGE) were used to validate the robustness of the predictive models. Here, the Boruta-Random Forest (B-RF), as a new robust tree-based FS, was adopted to identify the most significant candidate inputs and effective input combinations to reduce the computational cost and time of the modeling. The outcomes of four selected input combinations ascertained that the ANFIS-OA regarding the best accuracy in terms of (R = 0.9450, RMSE = 1.1253 ppm, and KGE = 0.9146) outperformed the ANFIS-SMA (R = 0.9406, RMSE = 1.1534 ppm, and KGE = 0.8793), ANFIS-ACOR (R = 0.9402, RMSE = 1.1388 ppm, and KGE = 0.8653), Lasso-Reg (R = 0.9358), and ANFIS (R = 0.9306) models. Besides, the first candidate input combination (C1) by three inputs, including Cl⁻ (mg/l), Mg²⁺ (mg/l), Na⁺ (mg/l), yielded the best accuracy among all alternatives, implying the role importance of (B-RF) feature selection. Finally, the spatial salinity distribution assessment in the study area ascertained the high predictability potential of the ANFIS-OA hybrid with B-RF feature selection compared to other paradigms. The most important novelty of this research is using a robust framework comprised of the non-linear data filtering technique and a new hybrid neuro-computing approach, which can be considered as a reliable tool to assess water salinity in coastal aquifers.

Ecotoxicological risk assessment for sediments of Çavuşlu stream in Giresun, Turkey: association between garbage disposal facility and metallic accumulation

The objective of this paper was to stress the possible potential toxic element (PTE) accumulation in the surface sediments of the Çavuşlu Stream (ÇS), as well as examining the source identification of whether or not any association between garbage disposal facility (GDF) and ecotoxicity or human health risk in Giresun, Turkey. The sediment specimens were analyzed by inductively coupled plasma mass spectroscopy (ICP-MS) followed by microwave digestion. The descending order of metals (mg/kg) in sediments were as follows: Fe (38,791 ± 3269) > Al (27,753 ± 4051) > Mn (730.90 ± 114.60) > Cr (233.39 ± 53.32) > V (176.40 ± 19.66) > Cu (85.22 ± 6.06) > Ni (72.87 ± 11.50) > Zn (46.45 ± 3.68) > Co (21.96 ± 3.33) > Pb (12.17 ± 1.97) > As (3.12 ± 1.45) > Sb (0.22 ± 0.06) > Cd (0.17 ± 0.02) > Hg (0.04 ± 0.01). Among these elements, certain metals (V, Cr, Cu, and Ni) in the sediments were above the average shale. Cr and Ni levels were above their corresponding threshold effect level (TEL) and probable effect level (PEL) values while Cu concentration exceeding its TEL, indicating that benthic organisms in the sediment of ÇS have likely toxic responses. Based on the results from contamination factor (CF), enrichment factor (EF), and geo-accumulation factor (I_geo) values of PTEs, the sediment was frequently classified into moderate contamination, moderate enrichment, and unpolluted to moderately polluted group. Pollution load index (PLI), integrated pollution index (IPI), and ecological risk index (E_rⁱ) indicated low pollution or low potential ecological risk. Toxicity risk index (TRI) and toxic unit analysis (TUs) suggested moderate toxicity. The outcomes of hazard quotient (HQ), total hazard index (THI), and lifetime cancer risk (LCR) stressed out that PTEs would not pose a significant health risk when adults are exposed to sediments in ÇS. However, a non-cancerogenic health risk for children was considered as the collective effect of 14 PTE (THI = 1.47 > 1). Multivariate statistical analysis (principal component analysis (PCA), Pearson's correlation coefficient (PCC), and hierarchical cluster analysis (HCA)) outlined that the metallic accumulation in the sediments of ÇS was related to lithological, geological, and anthropogenic impacts. Therefore, the GDF is likely a major reason in terms of anthropogenic pollution in the sediments of the ÇS.

Toxic metal pollution and ecological risk assessment in water and sediment at ship breaking sites in the Bay of Bengal Coast, Bangladesh

Quantification of four toxic metals (As, Cr, Cd, and Pb) in water and sediments at the Sitakunda ship breaking area in Bangladesh was studied. Along with this, sediment quality and ecological risk were evaluated for the metal intrusion to the study area. A total sample number of 120 (water; n = 60 and sediment; n = 60) were analyzed for both winter and summer seasons using atomic absorption spectrophotometer (AAS). The trace metal concentration in both water and sediment showed decreasing trend as follows; Cr (mean-W: 0.118 mg/L; mean-S:121.87 mg/kg) > Pb (mean-W: 0.064 mg/L; mean-S: 65.31 mg/kg) > As (mean-W: 0.03 mg/L; mean-S: 32.53 mg/kg) > Cd (mean-W: 0.004 mg/L; mean-S: 4.81 mg/kg). However, in both segments, the concentrations of the toxic metals exceeded the recommended acceptable limits. As and Cd showed significant variation (water and sediment) between the seasons, while Pb and Cr had no seasonal impact. Metal pollution index (MPI) and contamination factor (CF) was evaluated and revealed that the study area exhibited the critical score of water quality (MPI > 100). The cumulative effect of the metal concentrations was high (CI > 3). The assessed mean geoaccumulaiton index (I_geo) revealed that the study area was moderate to strongly polluted except for Cr. According to the contamination factor (CF), the sediment samples were moderate to highly contaminated by Cd, Pb, and As. Moreover, the explored range of pollution load index (PLI) in all sampling sites in the ship breaking region was from 1.75 to 3.10, suggesting that the sediment in the study area was highly polluted by heavy metals (PLI > 1). The risk index and the potential ecological risk index (PERI) suggested that the study area was at high risk due to metals pollution. Therefore, it is obligatory to maintain some crucial efforts for the betterment of the surrounding environment near the investigated sites.

Heavy metals contamination and associated health risks in food webs-a review focuses on food safety and environmental sustainability in Bangladesh

Heavy metals occur naturally in very small amounts in living organisms, but exposure to their higher concentrations is hazardous. Heavy metals at hazardous levels are commonly found in foodstuffs of Bangladesh, mainly due to the lack of safety guidelines and poor management of industrial effluents. Several lines of evidence suggest that the level of heavy metals in foodstuffs of Bangladesh is higher than the acceptable limits set by World Health Organization/Food and Agriculture Organization. Literature survey revealed that the sources and transport pathways of heavy metals in the ecosystem and the abundance of heavy metals in the food products of Bangladesh are potential threats to food safety. However, an extensive assessment of the toxicity of heavy metals in food webs is lacking. Although widespread heavy metal contamination in various foodstuffs and environmental matrices have been summarized in some reports, a critical evaluation regarding multi-trophic transfer and the health risk of heavy metal exposure through food chain toxicity in Bangladesh has not been performed. This systematic review critically discussed heavy metal contamination, exposure toxicity, research gaps, existing legislation, and sustainable remediation strategies to enhance Bangladesh's food safety. In particular, this study for the first time explored the potential multi-trophic transfer of heavy metals via food webs in Bangladesh. Furthermore, we recommended a conceptual policy framework to combat heavy metal contaminations in Bangladesh.