Spatial distribution and hydrogeochemical evaluations of groundwater and its suitability for drinking and irrigation purposes in kaligonj upazila of satkhira district of Bangladesh

Groundwater is a significant water resource for drinking and irrigation in Satkhira district, Bangladesh. The depletion of groundwater resources and deterioration in its quality are the results of the confluence of factors such as industrialization, intensive irrigation, and rapid population growth. For this reason, this study focused on the evaluation of tubewell water of six unions of Kaligonj upazila in Satkhira district, which is situated in the coastal southwest part of Bangladesh. Major and trace elemental concentrations were assimilated into positive matrix factorization (PMF) to identify potential sources and their respective contributions. Principal component analysis (PCA) revealed that groundwater salinization and manmade activities were the primary causes of heavy metals in the coastal groundwater. Its average pH value was found to be 7.5, while Dissolved oxygen, Total dissolved solids, salinity, and conductivity, with values ranging from 1.18 to 7.38 mg/L, 0.5-4.88 g/L, 0.4-5%, and 0.95 to 8.56 mS/cm, respectively. The total hardness average value was 561.7 mg/L, classified into the very hard water categories, which is why 90% of the tubewell water samples were unfit for household purposes. All samples had an excessive level of arsenic present. The iron concentration of fifteen (15) samples crossed the standard limit according to WHO 2011 value. Around 63% of the samples were of the Na+-K+-Cl--SO42- type, and about 72% were sodium-potassium and alkali types. 98% of samples were covered in chloride and bicarbonate. The findings showed that 45.83% of the groundwater samples had negative Chloroalkaline index (CAIs), while 54.16% had positive. The permeability index (PI) was an average of 73%, and residual sodium carbonate (RSC) averaged 260.2 mg/L, and the findings clearly showed that 80% of the samples weren't appropriate for irrigation. According to the sodium adsorption ratio (SAR) value, 65% of the samples fell into the unsuitable category. These calculations indicated a high overall salinity hazard in the study area, which may be caused by the intrusion of sea water given that the study area is close to the coastal region. Findings compared to standards revealed that the majority of the samples were deemed unfit for drinking and irrigation purposes. Hence, additional attention must be paid to this area to ensure the availability of drinkable water and to preserve sustainable farming practices.

Origin, spatial distribution, sediment contamination, ecological and health risk evaluation of trace metals in sediments of ship breaking area of Bangladesh

Eleven trace metals (Cd, Cr, Fe, Mn, Cu, Ni, Co, Zn, As, Pb, and Ag) in sediments of Bangladesh's ship breaking area were measured by an atomic absorption spectrometer to determine origin, contamination extent, spatial distributions, and associated ecological and human health hazards. This study found considerable quantities of Pb, Cd, Mn, Zn, and Cu when compared with standards and high levels of Pb, Cd, Zn, Cu, As, and Ag contamination according to pollution evaluation indices. Different indices indicate most of the sampling sites were highly polluted. However, spatial distribution maps indicate that trace metals were predominantly deposited in the northern and southern region. The ecological risk index revealed that Cd has the highest while Pb and As had moderate risk. Based on the health index values, Zn for both adults and children were higher than the safe limit while Mn, Pb, Cr, As, Fe, Cu, Ni, and Co for children were close to the threshold. The mean total carcinogenic risk values of Cr, As, and Ni for children and Ni for adults exceeded the permissible threshold. The cancer risk possibilities were further assessed using Monte Carlo simulation. Most trace metals have anthropogenic origins, which were attributed to ship breaking activities.

Heavy metals in popularly sold branded cigarettes in Bangladesh and associated health hazards from inhalation exposure

Tobacco products are widely recognized as a major contributor to death. Cigarette smoke contains several toxic chemicals including heavy metals particulate causing high health risks. However, limited information has been available on the health risks associated with the heavy metals in cigarettes commonly sold in the Bangladeshi market. This study evaluated the concentrations and potential health risks posed by ten concerned heavy metals in ten widely consumed cigarette brands in Bangladesh using an atomic absorption spectrometer. The concentration (mg/kg) ranges of heavy metals Pb, Cd, Cr, As, Co, Ni, Mn, Fe, Cu, and Zn vary between 0.46-1.05, 0.55-1.03, 0.80-1.2, 0.22-0.40, 0.46-0.78, 2.59-3.03, 436.8-762.7, 115.8-184.4, 146.6-217.7, and 34.0-42.7, respectively. We assume that the heavy metals content among cigarette brands is varied due to the differences in the source of tobacco they use for cigarette preparation. The carcinogenic risks posed by heavy metals follow the order of Cr > Co > Cd > As > Ni > Pb, while the non-carcinogenic risks for Cu, Zn, Fe, and Mn were greater than unity (HQ > 1), except for Fe. The existence of toxic heavy metals in cigarette tobacco may thus introduce noticeable non-carcinogenic and carcinogenic health impacts accompanying inhalation exposure. This study provides the first comprehensive report so far on heavy metal concentration and associated health risks in branded cigarettes commonly sold in Bangladesh. Hence, this data and the information provided can serve as a baseline as well as a reference for future research and have potential implications for policy and legislation in Bangladesh.

Human exposures to multiple water sources in the southwestern coastal region of Bangladesh: water quality, pollution sources, and preliminary health risks appraisals

The coastal areas of Bangladesh have poor accessibility to fresh drinking water and the groundwater is not suitable for drinking, cooking, and other domestic uses due to high levels of salinity and potentially toxic elements. The current study focuses on understanding of the distribution of some physicochemical parameters (temperature, pH, EC, TDS, and salinity) and chemical elements (Fe, Mn, Zn, Ca, Mg, Na, K, Cu, Co, Pb, As, Cr, Cd, and Ni) with health perspective in drinking water from the southwestern coastal area of Bangladesh. The physicochemical properties of the water samples were examined with a multiparameter meter, while the elemental concentrations were analyzed using atomic absorption spectrometer. Water quality index (WQI) and irrigation indices were utilized to determine the drinking water quality and irrigation feasibility, respectively, whereas hazard quotients (HQs) and hazard index (HI) were used to assess the probable pathways and the associated potential risks to human health. The concentrations of some toxic elements in measured samples were relatively higher compared to drinking water guidelines, indicating that ground and surface water are not apt for drinking and/or domestic uses. The multivariate statistical approaches linked the source of the pollutants in the studied water body mostly to the geogenic origin including saline water intrusion. WQI values ranged from 18 to 430, reflecting excellent to unsuitable categories of water quality. The assessment of human health risks due to exposure to contaminated water demonstrated both carcinogenic and non-carcinogenic health risks in the exposed residents of the study area. Therefore, appropriate long-term coastal area management strategies should be adopted in the study region for environmental sustainability. The findings of this research will be supportive in understanding the actual situation of fresh drinking water in the area for policymakers, planners, and environmentalists to take effective necessary measures to ensure safe drinking water in the study area.

Characterization of Growth-Promoting Activities of Consortia of Chlorpyrifos Mineralizing Endophytic Bacteria Naturally Harboring in Rice Plants-A Potential Bio-Stimulant to Develop a Safe and Sustainable Agriculture

Eighteen pesticide-degrading endophytic bacteria were isolated from the roots, stems, and leaves of healthy rice plants and identified through 16S rRNA gene sequencing. Furthermore, biochemical properties, including enzyme production, dye degradation, anti-bacterial activities, plant-growth-promoting traits, including N-fixation, P-solubilization, auxin production, and ACC-deaminase activities of these naturally occurring endophytic bacteria along with their four consortia, were characterized. Enterobacter cloacae HSTU-ABk39 and Enterobacter sp. HSTU-ABk36 displayed inhibition zones of 41.5 ± 1.5 mm, and 29 ± 09 mm against multidrug-resistant human pathogenic bacteria Staphylococcus aureus and Staphylococcus epidermidis, respectively. FT-IR analysis revealed that all eighteen isolates were able to degrade chlorpyrifos pesticide. Our study confirms that pesticide-degrading endophytic bacteria from rice plants play a key role in enhancing plant growth. Notably, rice plants grown in pots containing reduced urea (30%) mixed with either endophytic bacterial consortium-1, consortium-2, consortium-3, or consortia-4 demonstrated an increase of 17.3%, 38.6%, 18.2%, and 39.1% yields, respectively, compared to the control plants grown in pots containing 100% fertilizer. GC-MS/MS analysis confirmed that consortia treatment caused the degradation of chlorpyrifos into different non-toxic metabolites, including 2-Hydroxy-3,5,6 trichloropyridine, Diethyl methane phosphonate, Phorate sulfoxide, and Carbonochloridic. Thus, these isolates could be deployed as bio-stimulants to improve crop production by creating a sustainable biological system.

Characterization of microplastic pollution in the Pasur river of the Sundarbans ecosystem (Bangladesh) with emphasis on water, sediments, and fish

An emerging concern of today's world, due to their universal dispersion worldwide, is the environment's microplastic pollution. The Sundarbans, the world's largest mangrove, have unique and dynamic environmental settings with numerous pollution risk exposures, including microplastics (MPs). Thus, the present study has focused on the MP pollution in water, sediment, and fish samples of the Sundarbans of Bangladesh for the first time. Water and sediment samples were collected (n = 30/each) from sampling locations along the Pasur river (Bangladesh). Furthermore, nine species of fish samples were collected from a local fish market situated at the Mongla port. Results show that 100 % of the analyzed samples have evidence of MPs. On average, 2.66 × 10³ plastic particles/L and 1.57 × 10⁵ particles/kg were found in water and sediment samples, respectively. Furthermore, results show a higher number of MPs in the animals' gastrointestinal tract (GIT) (10.41 particles/g), concerning the average concentration recorded in the muscles (4.68 particles/g). O. pama and H. nehereus were the species that showed the highest MPs accumulation in the GIT. In the muscles, the highest MP levels were observed in T. ilisha and L. calcarifer. Most of the particles were smaller than 1 mm; black-colored particles dominated the pool. FT-IR analysis revealed the presence of seven polymer types where polyamide was abundant in water and sediment samples. SEM analysis showed morphological structures and adsorbed particles on the surface of plastic samples, and the spatial distribution of MPs indicates that the location with high human intervention has elevated levels of MPs. Therefore, our study demonstrates that Sundarbans mangrove forests are highly contaminated with MPs and that its fisheries can be a potential source of human exposure to these pollutants.

Microplastics in different fish and shellfish species in the mangrove estuary of Bangladesh and evaluation of human exposure

The water bodies in Bangladesh thrive from plastic pollution. Estuaries are pools of environmental contaminants, and the world's largest mangrove forest, Sundarbans' estuary, is no exception. Thus, for the first time, we investigate MPs abundance in the muscle and gastrointestinal tract (GIT) of twenty estuarine species of fish and shellfish of the Sundarbans, as well as the human health risk. MPs abundance was evident in all the samples ranging from 5.37 ± 1.07 to 54.30 ± 16.53 MP items/g wet body weight (dw) in muscle samples and 7.33 ± 1.89 to 205.61 ± 136.88 MP items/g (dw) in GIT samples. The estimated health risk from MPs is substantial, where the average human intake will be 85,710.08 items of MPs per year per capita for the population of Bangladesh. The dominant polymer types observed using ATR-FTIR are PP and PE (17.5 %), PA (17.5 %) in the muscle tissues, and PP and PE (11.11 %), and EVA (11.11 %) in the GITs. Bottom-feeding species, such as demersal and benthic species, are more contaminated. However, the level of MPs in the species shows a negative correlation with the length and weight of the species. This study reveals that MP pollution is widespread and concerning in Bangladesh's Sundarban mangrove estuarine zone.

Identification and quantification of microplastics in agricultural farmland soil and textile sludge in Bangladesh

Although microplastic (MP) pollution of aquatic ecosystems is a high-priority study topic, the issue of terrestrial environment and textile manufacturing waste has received little attention. Thus, this study was carried out to investigate the presence of MPs in agricultural land near textile industries and textile sludge samples in Bangladesh. Thirty-two soil samples from four agricultural farmland and five sludge samples were collected and analyzed. We show that the MPs content from agricultural farmland soil and textile sludge samples was 2.13 × 10⁴ ± 0.13 × 10⁴ MPs/kg and 2.92 × 10⁴ ± 0.14 × 10⁴ MPs/kg, respectively. MPs with a size between 1.0 and 1.5 mm were the least frequent in both soil and textile sludge samples. Fibers were more prevalent in textile sludge and fragments in soil samples. In addition, the percentage of transparent/white MPs was higher in the soil samples, and those classified as "multicolor" and "others" were more frequent in the sludge samples. Nine types of polymers were identified in the soil samples: PS, EVA, latex, HDPE, PVC, ABS, CA, LDPE, and PP. Except for LDPE, all these polymers were also found in the textile sludge samples, in addition to PU, nylon, and FEP, totaling eleven polymer types. On the other hand, we did not find evidence to support the association between MP contamination in soil samples and MPs identified in textile sludge samples. As demonstrated in the principal components analysis (PCA), the analyzed samples were separated by PC1, which suggests that the MPs reported in the soil come from sources that are not directly related to the textile industries. Thus, further research is needed to fully reveal MPs' fate and ecological risks in the soil environment and textile sludge, and necessary action is required to control MP pollution in terrestrial ecosystems.

Spatial distribution, water quality, human health risk assessment, and origin of heavy metals in groundwater and seawater around the ship-breaking area of Bangladesh

The concentrations of eleven heavy metals (Pb, Cd, Cr, Fe, Mn, Zn, Cu, Ni, Co, As, and Ag) were assessed in both groundwater and seawater collected from the ship-breaking industrial area of Bangladesh using an atomic absorption spectrometer. The investigation aimed to estimate the water quality and pollution level employing several indices, and its associated health risks for the first time in that area. This study found that Cd, Cr, Fe, Pb, Mn, and Ni were higher in both groundwater and seawater compared with WHO standards. Based on the WQI (water quality index) and EWQI (entropy water quality index) classifications, the quality of most of the groundwater is extremely poor or unsuitable for drinking purposes. Furthermore, the HPI (heavy metal pollution index), HEI (heavy metal evaluation index), and CD (degree of contamination) values of most groundwater and all seawater samples exhibit a higher degree of pollution. In addition, the results of NI (Nemerow pollution index) come to an end that both groundwater and seawater in the study area are mostly polluted by Fe, Mn, Pb, Cr, and Cd. Although the HI (hazard quotient index) values of almost all studied heavy metals in both cases of adults and children are within the safe limit, the HI value of Cr for an adult is near the threshold limit and the maximum HI value of Cr for children exceeds this limit. The carcinogenic risk reveals that Cr, Pb, As, and Cd produce detrimental effects on local people through the direct ingestion of groundwater. The pollution source is identified using principal component analysis and a Pearson correlation matrix as being primarily anthropogenic and attributed to intensive ship-breaking activities or other industries in the area.

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.

Exposure and health risks of metals in imported and local brands' lipsticks and eye pencils from Bangladesh

Elemental contamination in cosmetics is a serious health concern as it can pose a cumulative effect on the user's body over a long period. The prime motive of the study was to assess the concentration of 10 concerning chemical elements (Pb, Cd, Cr, As, Co, Ni, Cu, Zn, Fe, and Mn) in imported and local lipsticks and eye pencil samples collected from retail outlets in central Bangladesh (Dhaka city) and to assess their dynamic health risks for users. A total of 18 lipsticks and 24 eye pencils were studied and concentrations of chemical elements were examined with atomic absorption spectrophotometer. The health risk assessment was performed for dermal and ingestion routes of the contaminants. The results reveal that the concentrations of the examined elements vary with colors, brands, and origins. Pb and As concentrations were found below the permissible limit but Cr concentration in some samples exceeded the allowable limit in cosmetics. Cd was not detected in any samples; however, other examined elements such as Co, Ni, Cu, Mn, Zn, and Fe were detected in considerable concentrations. Elements like Mn, Zn, and Fe were found at high levels. In the case of lipstick samples, elemental concentrations followed the order of Fe > Zn > Mn > Ni > Cr > Cu > Pb > Co > As, while the order was Fe > Cu > Mn > Zn > Ni > Cr > Co > Pb > As for eye pencil samples. Results of the hazards quotient (HQ) indicate that there were no non-carcinogenic or carcinogenic risks of elements in samples for dermal exposure. But the cancer risk values of Cr (HQ > 1 for ingestion) in brown color lipsticks and Ni indicate that lipsticks have some carcinogenic effects if they enter the user's body. Dermal cancer risk for eye pencils has also been calculated and for Pb, Cr, Ni, and As; the values were found within the acceptable ranges of 10^-6-10^-4. It is suggested that the allowable limit of all toxic elements in cosmetics must be established. Furthermore, continuous monitoring is urgently needed for personal care products like lipsticks and eye pencils commonly available in the local markets in the country like Bangladesh.

Assessment of microplastics pollution in aquatic species (fish, crab, and snail), water, and sediment from the Buriganga River, Bangladesh: An ecological risk appraisals

Current work focus on microplastic (MPs) occurrence in the water, sediment, and aquatic species (fish, crab, and snail) of the Buriganga River, Bangladesh, with an ecological risk assessment perspective. It also includes the distribution of MPs in different river ecosystem segments and the presence of heavy metal (loid)s (HMs) in water, sediments, and MPs surface. The MPs were inspected by stereomicroscope to identify the shapes, color, and size, and Fourier transform infrared (FTIR) spectroscopy was used to characterize polymer types. The samples concentration of four HMs viz., As, Cd, Cr, and Pb were determined by atomic absorption spectrometry (AAS). The possible MPs content in water, sediment, fish, crab, and snail were varied from 0.250 to 0.117 MPs/mL, 3.5-8.17 MPs/g, 0.65-3.82 MPs/g, 3.75-4.28 MPs/g, and 0.84-1.12 MPs/g, respectively. Fibers and fragments were the most dominant shape, less than 0.5 mm was dominant in size, and blue was the dominant color. In the evaluation of the chemical composition of MPs in water, sediment, fish, snail, and crab samples, Polyethylene terephthalate (PETE), Ethylene-vinyl acetate (EVA), High-density polyethylene (HDPE), Acrylonitrile butadiene styrene (ABS), Cellulose acetate (CA), and Nylon were identified. Regarding HMs load, the river demonstrated a highly polluted environment following the abundance pattern Cr > Pb > As>Cd. SEM-EDAX of MPs was conducted to investigate the surface MP's surface and elemental composition. It reveals that the MPs surface has characteristic flakes, cracks, and adhering particles along with Si, K, Au, C, and O on the surface studied MPs. There is no significant relationship found among the ecosystem segments. However, Ompok bimaculatus species show a negative relationship of MPs distribution with water and sediment. Moreover, according to the ecological risk of MPs pollution in the Buriganga River, it was in category-I, indicating considerable pollution load due to the presence of MPs.

Is there tea complemented with the appealing flavor of microplastics? A pioneering study on plastic pollution in commercially available tea bags in Bangladesh

Microplastic pollution is a global concern, mainly due to its adverse effects on organisms and ecosystems. However, our knowledge of its impact on humans, in particular, is still very limited. Thus, while we have not gathered definitive information on their consequences, studies that aim to identify the MP's sources constitute subsidies to better understand the various exposure pathways to these pollutants. Thus, we investigated the possible presence of MP-like particles in teabag samples (of different brands) obtained in Dhaka, Bangladesh. Surprisingly, all analyzed samples (five brands) were contaminated with MPs. Fragments and fibers were identified in a higher percentage, and a wide variety of colors was identified, with a predominance of brown, blue, and red colors. Scanning electron microscope images of teabags exhibited net-like structures of fiber particles with a smooth surface. Furthermore, we observed irregularly shaped MPs and rougher surfaces and fragments in the process of detachment from the main fiber, oxidation flakes, and fracture-like. The average size of these pollutants was between 200.6 and 220.7 μm, and the polymer types identified via Fourier-transform infrared spectroscopy (FT-IR) were polytetrafluoroethylene, high-density polyethylene, polycarbonate, nylon, polyvinyl chloride, polytetrafluoroethylene, ethylene-vinyl acetate, cellulose acetate, and acrylonitrile butadiene styrene, the last three being the most frequent in the analyzed samples. Finally, we noticed that MPs from tea bags in Dhaka could cause an average emission of 10.9 million grams of MPs/year. Although the teabags analyzed in our study are not "complemented with the appealing flavor of MPs", it is very likely that tea ingestion in Dhaka is accompanied by the concomitant ingestion of plastic particles making teabags an important route of human exposure to these micropollutants.

Seasonal distributions and risk assessment of polychlorinated biphenyls (PCBs) in the surficial sediments from the Turag River, Dhaka, Bangladesh

Polychlorinated biphenyls (PCBs) were determined in sediment samples collected from the Turag River, Dhaka city, Bangladesh. This river provides critical ecological services to agriculture, industry, and transportation. However, it is one of the most polluted rivers surrounding the capital city. This study analyzed six PCB congeners (PCB 10, PCB 28, PCB 52, PCB 138, PCB 153, and PCB 180) by GC-ECD at 9 sampling sites in two different seasons. The total concentrations of PCBs in studied samples varied from 344 to 0.217 ng/g dw and 10.6 to 1.68 ng/g dw in Monsoon-season and Dry-season, respectively. The paramount contributor-congener to the total PCBs was PCB 180, and it was found at all the study sites. The ecological risk assessment indicated a high potential risk in the Monsoon-season ([Formula: see text]= 277) and low potential risk in the Dry-season ([Formula: see text]= 25.7). Sediment quality guideline quotients (SQGQs) showed that PCBs in the Monsoon-season would cause "no" or "moderate" biological effects on organisms at every site except site-5 (S5) (high biological effects), while no adverse ecotoxicological effect was observed in the Dry-season. Considering both probable effect level (PEL) and threshold effect level (TEL), the new sediment quality guideline quotient (NSQGQ) showed that in the Dry-season PCB contamination would cause "moderate" biological effects. At the same time, in the Monsoon-season, the findings remained consistent with the findings of SQGQ. This study looked at the PCB contamination scenario in the Turag River sediments for the first time and allowed for a comparison with other rivers worldwide.

Mechanism of arsenic enrichment and mobilization in groundwater from southeastern Bangladesh: Water quality and preliminary health risks assessment

To understand the mechanistic pathway of arsenic (As) enrichment and mobilization in groundwater (southeastern Bangladesh) and to evaluate the water quality as well as associated health risks, a suite of systematically collected groundwater samples (depth: 17-61 m) were analyzed. Arsenic concentrations (μg L^-1) in the groundwater samples were ranged from 6 to 581 with a mean value of 199 which is significantly higher than the recommended values. The assessment of water quality using entropy water quality index and irrigation water quality indices revealed that the groundwater in the studied region was not recommended for drinking and irrigation, respectively with few exceptions. Dominant water types in the studied area were Ca-Mg-HCO_3, Na-HCO₃, and Na-Cl types. Various forms of water-rock interactions, leaching of evaporates, and the confined nature of the aquifer mostly control the hydro-chemical parameters. Fe/Mn bound As are likely to be released in the aquifer through the dissolution of carbonate minerals of Fe/Mn while the higher degree of water-rock interaction and probable oxidation of organic materials helped to elevate As concentration. The probable longer residence time of groundwater guided by topographic slope and the neighboring clayey aquitard govern the As mobilization in the aquifer. Probabilistic health risk assessment revealed that groundwaters from the studied area can cause both non-carcinogenic and carcinogenic health risks.

Trace metals and organochlorine pesticide residues in imported fishes in Bangladesh and human health risk implications

Substantial quantity of fish has been imported to Bangladesh without adequate food safety assessment which can pose a serious health risk to local people. This study analyzed the trace metals and organochlorine pesticides residues and the associated human health risk in 33 imported fishes (9 species) from four countries (India, Myanmar, Oman, and United Arab Emirates) collected from three different ports (Benapole, Bhomra, and Chittagong) of Bangladesh with invoice lists from the port authorities. Trace metal concentrations were determined using graphite furnace absorption spectrometry and flame absorption spectrometry. The two organochlorine pesticides (Aldrin and Chlordane) residues were determined by GC-MS and found as below detection level (BDL). The trace metal concentrations (mg/kg-ww) in imported fish samples ranged as As 0.008 to 0.558, Pb 0.004 to 0.070, Cr 0.010 to 0.109, Cd 0.00 to 0.083, Ni 0.011 to 0.059, Co BDL to 0.067, Mn BDL to 0.0780, Fe 1.780 to 10.77, Cu 0.055 to 0.632, and Zn 0.898 to 9.245. Concentrations of As and Cd were higher than the food safety guideline. Considering the source country of imported fishes, fish samples from Oman were mostly contaminated by the trace metals. The estimated daily intake (EDI) was higher for Cr. However, the target hazard quotient (THQ) for individual metal and total THQ for combined metals were lower than 1, indicating no apparent non-carcinogenic health risk for consumers. The cancer risk (CR) was within the acceptable range. But extensive monitoring of these toxic chemicals is needed prior to import these fishes to the country. Given the self-sufficiency in fish production, this study also argues whether Bangladesh needs to import the fishes at all.

Multivariate statistics and entropy theory for irrigation water quality and entropy-weighted index development in a subtropical urban river, Bangladesh

Currently, a well-developed combination of irrigation water quality index (IWQIs) and entropy water quality index (EWQIs) for surface water appraisal in a polluted subtropical urban river is very scarce in the literature. To close this gap, we developed IWQIs by establishing statistics-based weights of variables recommended by FAO 29 standard value using the National Sanitation Foundation Water Quality Index (NSFWQI) compared with the proposed EWQIs based on information entropy in the Dhaleshwari River, Bangladesh. Fifty surface water samples were collected from five sampling locations during the dry and wet seasons and analyzed for sixteen variables. Principal component analysis (PCA), factor analysis (FA), Moran's spatial autocorrelation, and random forest (RF) model were employed in the datasets. Weights were allocated for primary variables to compute IWQI-1, 2 and EWQI-1, 2, respectively. The resultant IWQIs showed a similar trend with EWQIs and revealed poor to good quality water, with IWQI-1 for the dry season and IWQI-2 for the wet season is further suggested. The entropy theory recognized that Mg²⁺, Cr, TDS, and Cl^- for the dry season and Cd, Cr, Cl-, and SO₄^2- for the wet season are the major contaminants that affect irrigation water quality. The primary input variables were lessened to ultimately shortlisted ten variables, which revealed good performance in demonstrating water quality status since weights have come effectively from PCA than FA. The results of the RF model depict NO₃^-, Mg²⁺, and Cr as the most predominant variables influencing surface water quality. A significant dispersed pattern was detected for IWQImin-3 in the wet season (Moran's I>0). Overall, both IWQIs and EWQIs will generate water quality control cost-effective, completely objective to establish a scientific basis of sustainable water management in the study basin.

Chromium Contamination from Tanning Industries and Phytoremediation Potential of Native Plants: A Study of Savar Tannery Industrial Estate in Dhaka, Bangladesh

Tannery wastewater is a significant cause of chromium (Cr) contamination in land and water. This study assessed Cr contamination caused by the discharge of tannery wastewater in the Dhaleshwari River and identified possible native plants for phytoremediation of Cr. Water, soil and sediments samples were collected from upstream and downstream of the wastewater discharge channel of Savar tannery industrial estate situated on the bank of the river. Samples of root, stem, leaf and fruit of four selected plants (i.e., Eichhornia crassipes, Xanthium strumarium L., Cynodon dactylon, Croton bonplandianum Baill.) were also collected from those sampling points. The total Cr in acid digested samples were determined by flame atomic absorption spectrometry. High concentrations of Cr were detected in the water, soil and sediment samples collected near the wastewater discharge channel. Of all the plant species, Xanthium strumarium L. exhibited high translocation factors (TF) and bioconcentration factors (BCF) for Cr. Based on the findings of this study Xanthium strumarium L. is preferable as a native species for phytoremediation of Cr.

Chemical and physicochemical characterization of effluents from the tanning and textile industries in Bangladesh with multivariate statistical approach

Industrial effluents are one of the foremost concerns relating to the anthropogenic environmental pollution. The effluents from the tanning and textile industries in Dhaka, Bangladesh, were characterized chemically and physicochemically with multivariate statistical techniques. The concentrations of heavy metals viz., Pb, Cd, Cr, Mn, Fe, Ni, Cu, and Zn were determined by atomic absorption spectrometer while concentrations of anions viz., F^-, Cl^-, NO₂^-, NO₃^-, and SO₄^2- were measured by ion chromatograph. The physicochemical parameters viz., temperature, pH, electrical conductivity (EC), salinity, turbidity, dissolved oxygen (DO), and biological oxygen demand (BOD) were measured by a multiparameter meter while total suspended solids (TSS) and total dissolved solids (TDS) were measured gravimetrically. This study showed that effluents from both industries demonstrated high levels of TSS, TDS, EC, and heavy metals. Tannery effluents have lower pH and DO, and higher BOD, Cl^-, SO₄^2-, and Cr concentrations while textile dyeing effluents have higher pH, NO₂^-, and NO₃^- concentrations, compared to the standard limits promulgated by the Bangladesh government. Multivariate statistical techniques such as cluster analysis and principal component analysis along with the correlation matrices showed significant association among the measured parameters and identified pollution sources as well as effluent types in the study area which could be linked to the processes used in textile dying and tanning industries. This study will be useful for identifying pollutants emanating from the two industries and will guide future industrial aquatic studies where multiple industrial runoffs are concerned.