First report on population dynamics and stock status of Badis badis in a wetland ecosystem (NW Bangladesh): Insights from new recorded maximum length.

Badis badis (Hamilton, 1822) is a popular ornamental fish species in the world. This study provides valuable insights into some biological indices of B. badis using a sample of 293 individuals. These individuals were captured from June 2021 to May 2022 using several traditional fish harvesting gears and traps in the Babu Mondoler beel, a wetland ecosystem in NW Bangladesh. Biometric data were collected for each individual, contributing to a comprehensive understanding of this species. The recorded results revealed a wide range of total length (TL), varying from 2.30 to 11.33 cm. Notably, we observed a maximum length of 11.33 cm TL and a maximum body weight (BW) of 18.18 g, ranging from 0.20 to 18.18 g, setting a new record and showcasing the diversity in size within the population. The estimated allometric coefficient (b) showed that combined sexes had negative allometric growth (b = 2.67). Growth parameters were assessed as L∞ = 11.93 cm, K = 0.95 year-1 and Ø' = 2.13. The tmax was 3.16 years. The Lm was measured at 7.02 cm TL and tm = 0.89 year. In this study, KF (1.4240 ± 0.3194) was best for the wellbeing of B. badis in the study area. The a3.0 was estimated at 0.0079 and the relative weight WR (100.90 ± 16.994). Physiological status showed that maximum fatty fish were observed at 10.00-12.00 cm TL; lowest at 4.0-6.00 cm TL. Moreover, the Z, Mw, F and E were estimated to be 3.29 year-1, 1.45 year-1, 1.84 year-1and 0.56, respectively. Additionally, the Lopt for this species was found to be 7.91 cm TL. The findings from this study hold great potential for enhancing the assessment and management of the specimen in the study area and its ecological community. These valuable insights into the population parameters, growth patterns, and exploitation rates of B. badis can inform future management strategies, ensuring the sustainable utilization of this fishery resource in Bangladesh and others neighboring countries.

Macro and microanatomy of some organs of a juvenile male Ganges River dolphin (Platanista gangetica spp. gangetica).

Ganges River dolphins (Platanista gangetica spp. gangetica) are air-breathing, warm-blooded mammals endemic to the Ganges and Karnaphuli rivers of the Indian subcontinent. Nevertheless, very little basic histomorphological research has been conducted on this endangered species. Therefore, this study aimed to describe the morphological features of different organs of P. gangetica. Despite becoming aquatic animals, they showed similarities with terrestrial mammals, such as the pair of lungs and an apical bronchus in the respiratory system, which are pretty standard in ruminants and pigs. However, unlike the terrestrial animal, the tracheobronchial tree was stiffer due to circularly arranged anastomosing plates of the hyaline cartilaginous ring in the trachea, cartilaginous plates in the bronchiole, and thick alveolar septa. The digestive system showed a three-chambered mechanical and glandular stomach similar to the artiodactyles. However, the intestine showed smaller caecum like the monogastric mammal. The urogenital system showed lobulated kidneys, a urinary bladder, a fibroelastic penis with sigmoid flexure, and a long urethral process similar to some terrestrial ruminants. Considering the aquatic environment, all those modifications, unlike terrestrial mammals, are necessary for their adaptation. Thus, this research will broadly help our clinicians and conservationist to take further steps toward disease diagnosis and monitoring of marine health of this endangered species.

Estimation of life history parameters for river catfish Eutropiichthys vacha: insights from multi-models for sustainable management.

The river catfish, Eutropiichthys vacha is a vital protein source for rural communities and has high commercial value, but understanding its life history and management strategies reveals major inadequacies and ambiguities in the riverine ecosystems. Consequently, this study employs multi-models to analyze the life history parameters of E. vacha in the Ganges River (northwestern Bangladesh) from January to December, 2020. The total length (TL) and body weight (BW) of 362 individuals (male = 170, female = 192) were measured by a measuring board and a digital weighing balance, respectively. The overall sex ratio (male: female) was 1.0: 1.13 and did not oscillate statistically from the standard 1:1 ratio (p > 0.05). The TL varied from 6.7-19.2 cm for males and 6.3-19.0 cm for females. The length-frequency distributions (LFDs) revealed females outnumbered in 8.0-9.99 cm TL whereas males in 7.0-7.99 cm TL. The slope (b) of the length-weight relationship (TL vs. BW) for both sexes (b = 2.87) was substantially lower than isometry, specifying negative allometric growth pattern for E. vacha. Sex-specific relative (K R ) and Fulton's (K F ) condition analysis revealed better state of well-being of males than females. Only K F exhibited significant correlation with both BW and TL, hence making it ideal condition for predicting the fitness of E. vacha in this river. Moreover, the relative weight (W R ) suggests an imbalanced habitat for females with higher abundance of predators but suitable for males. The form factor (a 3.0 ) was 0.0062 and 0.0065, whereas the size at first maturity (L m ) and mean natural mortality (M W ) were 11.38 and 11.27 cm TL and 1.29 and 1.28 year-1 for the respective sexes. Besides, the calculated mean optimum catchable length (L opt ) was 13.58 and 13.09 cm TL for each sex. These findings will be crucial for further studies and to recommend appropriate strategy for the sustainable management of E. vacha in the Ganges River and adjacent watersheds.

Rapid Characterization of Macroplastic Input and Leakage in the Ganges River Basin.

Efforts to understand macroplastic pollution have primarily focused on coastal and marine environments to the exclusion of freshwater, terrestrial, and urban ecosystems. To better understand macroplastics in the environment and their sources, a dual approach examining plastic input and leakage can be used. In this study, litter aggregation pathways at 40 survey sites with varying ambient population counts in the Ganges River Basin were surveyed in pre- and postmonsoon seasons. We examine active litter leakage using transect surveys of on-the-ground items, in conjunction with assessments of single-use plastic consumer products at the point of sale. We find that sites with low populations have a significantly higher number of littered items per 1,000 people than those with mid to high populations. Over 75% of litter items were plastics or multimaterial items containing plastic, and tobacco products and plastic food wrappers were the most recorded items. There was no significant variation of litter densities pre- and postmonsoon. Most single-use plastic consumer products were manufactured in-country, but approximately 40% of brands were owned by international companies. Stratified sampling of active litter input and consumer products provides a rapid, replicable snapshot of plastic use and leakage.

Regional-scale hydrogeochemical evolution across the arsenic-enriched transboundary aquifers of the Ganges River Delta system, India and Bangladesh.

Arsenic (As) dynamics within the extensively contaminated aquifers of the Ganges River delta have been widely studied over the past few decades, but the hydrogeochemical signatures across the delta aquifers remain to be characterized. Here, we characterize the varied geochemical and isotopic (δ18O, δ2H) signatures of groundwater across the delta and interpret the hydrogeochemical evolution pathways and the driving processes on a regional-scale as a function of the delta hydrostratigraphy. Our hydrostratigraphic model identifies three major aquifer sub-systems across the delta from north-west to south-east: a single continuous unconfined aquifer (Type I); a semiconfined vertically-segregated aquifer sub-system (Type II); and a nearly confined multilayered aquifer sub-system (Type III). The Type I aquifer is dominated by Ca-Mg-HCO3-rich waters, while the aquifers to the south (Type II and Type III) exhibits increasing dominance of Na-Cl hydrogeochemical facies at shallow and intermediate depths and Na-HCO3 hydrogeochemical facies in the deep aquifers. The spatial distribution of As is also found to be heavily dictated by hydrostratigraphy, wherein the Type I aquifer sub-system yields similar concentrations across depths, while the Type II and Type III aquifer sub-systems exhibit a sharp increase in As-safe aquifers with depth. Although dominant reducing conditions occur within the delta groundwater, co-occurrence of redox-sensitive solutes from varying redox stability fields indicates to the development of overlapping redox zones. Stable isotopic signatures of groundwater exhibit a progressive depletion away from the Bay of Bengal. The Type I aquifer exhibits relatively homogenous hydrogeochemical signatures, possibly suggesting deeper infiltration of recharge under higher vertical hydraulic gradients, while the Type II and Type III aquifers exhibit variability across depth, which is possibly a reflection of horizontally stratified groundwater flows, dictated by the spatial geometry of the intervening aquitard layers.

Reproductive performance of Asian stinging catfish Heteropneustes fossilis (Bloch 1794) in the Ganges River (NW Bangladesh) in relation to environmental factors.

Reproduction plays an important role in fish population efficiency and its resiliency to fishing and environment changes. The present study described the comprehensive information on reproductive feature of stinging catfish, Heteropneustes fossilis (Bloch 1794), including size at sexual maturity, spawning season, and fecundity using 622 female individuals sampling by the use of gill net, cast net, and square lift net from January to December 2019 in the Ganges River. We calculated the influences of various environmental parameters which include temperature, dissolved oxygen, pH, and rainfall on the reproductive feature of H. fossilis in the Ganges River. For every specimen, total length (TL), standard length (SL), and body weight (BW) were estimated by measuring board and electronic weighing scale. With ventral dissection of fishes, female gonads were cautiously removed and measured to 0.01 g precision. The gonadosomatic index (GSI), modified gonadosomatic index (MGSI), and Dobriyal index (DI) were used to assess the size at sexual maturity (Lm) and spawning season. According to the results of these indices, Lm was obtained 15.5 cm in TL. Also, TL50 was determined through logistic function as 15.5 cm in TL. Moreover, the highest GSI, MGSI, and DI values indicated the spawning season as of March-August, with peak in May-June. Total fecundity (FT) varied from 2059 to 59,984 with a mean of 25,028 ± 15,048. Temperature and rainfall was statistically correlated with GSI. In addition, long climatic data series analysis denoted that yearly mean atmospheric temperature is rising in 0.028 °C/year and yearly mean rainfall is declining in 2.98 mm/year which may suggest a potential shift of the spawning period of the species in the future if this trend persists. The results of our study might be more useful in imposing particular management and conservation for H. fossilis in the Ganges River and the surroundings.

Reassessing riverine carbon dioxide emissions from the Indian subcontinent.

Anthropogenic perturbations are increasing uncertainties in estimating CO2 emissions via air-water CO2 flux (FCO2) from large rivers of the Indian subcontinent. This study aimed to provide an improved estimate of the total FCO2 from the subcontinental rivers by combining calculations of the partial pressure of CO2 (pCO2) in eight major rivers with new measurements in the Ganges and Godavari. The average pCO2 in the two newly surveyed rivers, including tributaries, wastewater drains, and impoundments, were 3-6 times greater than the previously reported values. In some highly polluted urban tributaries and middle reaches of the Ganges that drain metropolitan areas, the measured pCO2 exceeded 20,000 µatm, ~40 times the background levels of the headwaters originating in the carbonate-rich Himalayas. The high pCO2 above 28,000 µatm in the lower reach of the Godavari was seven times the moderate levels of pCO2 in the headwaters of the volcanic Deccan Traps, indicating enhanced CO2 production in soils and anthropogenic sources under favorable conditions for organic matter degradation. Across the northern rivers, pCO2 exhibited a significant negative relationship with dissolved oxygen, but a positive relationship with inorganic N or P concentrations. The strong influence of water pollution on riverine pCO2 suggests that CO2 emissions from hypoxic, eutrophic reaches can greatly exceed phytoplanktonic CO2 uptake. Spatially resolved pCO2 data, combined with three gas transfer velocity estimates, provided a higher range of FCO2 from the subcontinental rivers (100.9-130.2 Tg CO2 yr-1) than the previous estimates (7.5-61.2 Tg CO2 yr-1). The revised estimates representing 2-5% of the global riverine FCO2 illustrate the importance of the Indian subcontinental rivers under increasing anthropogenic pressures in constraining global inland waters FCO2.

Assessing the snow cover dynamics and its relationship with different hydro-climatic characteristics in Upper Ganges river basin and its sub-basins.

Snowmelt is an important source of water in upstream part of the Ganges river basin (GRB), which provides water for different purposes to its 655 million inhabitants. However, studies assessing relationship between snow cover dynamics and changes in hydro-climatic variables are limited within this region, motivating the current research. In this study, MODIS snow cover product (MOD10A1) was used to assess the snow cover area (SCA) dynamics within the Upper Ganges river basin (UGRB) and its sub-basins for the time period of 2002-2014; available climate and hydrological data were used to assess the hydrological characteristics within three selected sub-basins in Nepal; and relationships between snow cover and different hydro-climatic variables are established for three sub-basins owing to availability of hydro-climatic data. Results show that the average annual maximum SCA is around 24.6-47.5% for UGRB and its sub-basins. Upper Yamuna river basin (UYRB) with lowest mean elevation among the sub-basins shows a single SCA peak in spring within an annual cycle, whereas UGRB and the higher sub-basins show an additional lower peak in fall mainly resulted from snow sublimation. During 2002-2014, SCA shows slight decreasing trends for UGRB (Kendall's Tau τ = -0.039) and the higher elevation zones B (3001-4500 m a.s.l.) and C (>4500 m a.s.l.) of most sub-basins, with significance in Zone C of SaRB (τ = -0.070) and KoRB (τ = -0.062). Annual discharge for Gandaki river basin (GaRB) and Koshi river basin (KoRB) shows non-significant decreasing trends (τ = -0.182, -0.303) which are resulted from decreasing discharge in different seasons in different sub-basins. Seasonal correlation analysis indicates an important water supply from rainfall in GaRB and combined water supply from rainfall and snowmelt in KoRB, along with dominant contribution of precipitation in monsoon months and snowmelt in non-monsoon months for all the three sub-basins.

Impact of global-scale hydroclimatic patterns on surface water-groundwater interactions in the climatically vulnerable Ganges river delta of the Sundarbans.

The global climate patterns like El Niño Southern Oscillation (ENSO) cycle and Indian Ocean Dipole (IOD) have impacts on surface water quality and groundwater recharge patterns. But the ENSO and IOD impacts on surface water-groundwater (SW-GW) interaction in terms of quality have not been studied. Therefore, the present study was conducted to delineate the impacts of ENSO and IOD on the SW-GW interaction process-induced groundwater quality of coastal aquifers of Sundarbans, by the application of isotopic signature, salinity content of groundwater and seawater in relation to rainfall variability. Study results revealed that the declining trend of rainfall potentially increases the seawater salinity. The rainfall pattern also positively correlates with the groundwater level (GWL) at a 5% level of significance observed from the wavelet analysis. The deficit in rainfall due to the El Niño is the possible reason for the declining GWL, which is giving rise to groundwater salinity. El Niño also affected the nearshore seawater salinity which was increased from 19 to 24 ppT. The study provides a surrogate understanding of the potential impact of El Niño in one of the most climatically vulnerable parts of the planet, while IOD impacts are not conclusive. In the scenario of depleted rainfall amount, groundwater abstraction practices need to be managed, otherwise, it could create a potential threat to the available drinking water resources in the present and future climate change scenarios.

Abundance and Diversity of Phages, Microbial Taxa, and Antibiotic Resistance Genes in the Sediments of the River Ganges Through Metagenomic Approach.

In this study, we have analyzed the metagenomic DNA from the pooled sediment sample of the river Ganges to explore the abundance and diversity of phages, microbial community, and antibiotic resistance genes (ARGs). Utilizing data from Illumina platform, 4,174 (∼0.0013%) reads were classified for the 285 different DNA viruses largely dominated by the group of 260 distinctive phages (3,602 reads, ∼86.3%). Among all, Microcystis (782 hits), Haemophilus (403), Synechococcus (386), Pseudomonas (279), Enterococcus (232), Bacillus (196), Rhodococcus (166), Caulobacter (163), Salmonella (146), Enterobacteria (143), Mycobacterium and (128) phages show the highest abundance and account for ∼90% of the total identified phages. In addition, we have also identified corresponding host pertaining to these phages. Mainly, Proteobacteria (∼69.3%) dominates the microbial population structure. Primarily, orders such as Caulobacterales (∼28%), Burkholderiales (∼13.9%), Actinomycetales (∼13.7%), and Pseudomonadales (∼7.5%) signify the core section. Furthermore, 21,869 (∼0.00695%) reads were classified in 20 ARG types (classes) and 240 ARGs (subtypes), among which 4 ARG types, namely multidrug resistance (12,041 reads, ∼55%), bacitracin (3,202 reads, ∼15%), macrolide-lincosamide-streptogramin (1,744 reads, ∼7.98%), and fosmidomycin (990 reads, ∼4.53%), have the highest abundance. Simultaneously, six resistance mechanisms were also recognized with the dominance of antibiotic efflux (72.8%, 15,919 reads). The results unveil the distribution of (pro)-phages; microbial community; and various ARGs in the Ganges river sediments.

Impact of Covid-19 Lockdown on Availability of Drinking Water in the Arsenic-Affected Ganges River Basin.

The 2020 COVID-19 pandemic has not only resulted in immense loss of human life, but it also rampaged across the global economy and socio-cultural structure. Worldwide, countries imposed stringent mass quarantine and lockdowns to curb the transmission of the pathogen. While the efficacy of such lockdown is debatable, several reports suggest that the reduced human activities provided an inadvertent benefit by briefly improving air and water quality. India observed a 68-days long, nation-wide, stringent lockdown between 24 March and 31 May 2020. Here, we delineate the impact of the lockdown on groundwater and river sourced drinking water sustainability in the arsenic polluted Ganges river basin of India, which is regarded as one of the largest and most polluted river basins in the world. Using groundwater arsenic measurements from drinking water wells and water quality data from river monitoring stations, we have studied ~700 km stretches of the middle and lower reaches of the As (arsenic)-polluted parts of the river for pre-lockdown (January-March 2020), syn-lockdown (April-May), and post-lockdown periods (June-July). We provide the extent of As pollution-free groundwater vis-à-vis river water and examine alleviation from lockdown as an opportunity for sustainable drinking water sources. The overall decrease of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations and increase of pH suggests a general improvement in Ganges water quality during the lockdown in contrast to pre-and-post lockdown periods, potentially caused by reduced effluent. We also demonstrate that land use (agricultural/industrial) and land cover (urban-periurban/rural) in the vicinity of the river reaches seems to have a strong influence on river pollutants. The observations provide a cautious optimistic scenario for potentially developing sustainable drinking water sources in the arsenic-affected Ganges river basin in the future by using these observations as the basis of proper scientifically prudent, spatially adaptive strategies, and technological interventions.

Phages from Ganges River curtail in vitro biofilms and planktonic growth of drug resistant Klebsiella pneumoniae in a zebrafish infection model.

Bacteriophages are a promising alternative for curtailing infections caused by multi drug resistant (MDR) bacteria. The objective of the present study is to evaluate phage populations from water bodies to inhibit planktonic and biofilm mode of growth of drug resistant Klebsiella pneumoniae in vitro and curtail planktonic growth in vivo in a zebrafish model. Phage specific to K. pneumoniae (MTCC 432) was isolated from Ganges River (designated as KpG). One-step growth curve, in vitro time kill curve study and in vivo infection model were performed to evaluate the ability of phage to curtail planktonic growth. Crystal violet assay and colony biofilm assay were performed to determine the action of phages on biofilms. KpG phages had a greater burst size, better bactericidal potential and enhanced inhibitory effect against biofilms formed at liquid air and solid air interfaces. In vitro time kill assay showed a 3 log decline and a 6 log decline in K. pneumoniae colony counts, when phages were administered individually and in combination with streptomycin, respectively. In vivo injection of KpG phages revealed that it did not pose any toxicity to zebrafish as evidenced by liver/brain enzyme profiles and by histopathological analysis. The muscle tissue of zebrafish, infected with K. pneumoniae and treated with KpG phages alone and in combination with streptomycin showed a significant 77.7% and 97.2% decline in CFU/ml, respectively, relative to untreated control. Our study reveals that KpG phages has the potential to curtail plantonic and biofilm mode of growth in higher animal models.

Modeling regional-scale groundwater arsenic hazard in the transboundary Ganges River Delta, India and Bangladesh: Infusing physically-based model with machine learning.

For the last few decades, toxic levels of arsenic (As) in groundwater from the aquifers of the Ganges River delta, India and Bangladesh, have been known to cause serious public health concerns. Innumerable studies have advocated the control of geomorphologic, geologic, hydrogeologic, biogeochemical, and anthropogenic factors on arsenic mobilization, flow, and distribution patterns within the Ganges River delta. We have developed transboundary regional-scale models for computing the probability of groundwater As concentrations to exceed the WHO permissible thresholds for drinking water of 10 µg/L within the Ganges River delta as a function of the various geomorphologic-(hydro)geologic-hydrostratigraphic-anthropogenic controlling factors, using statistical methods and artificial intelligence (AI) [i.e., machine learning] techniques namely, Random Forest (RF), Boosted Regression Trees (BRT) and Logistic Regression (LR) algorithms, followed by probabilistic delineation the high As-hazard zones within the delta. A "hybrid multi-modeling approach" was adapted for this study, which involved the introduction of hydrostratigraphic parameters (aquifer connectivity and surficial aquitard thickness) derived from a high-resolution transboundary hydrostratigraphic model developed for the Ganges River delta aquifer system, as predictors for modeling groundwater As probabilities within the delta. The RF model outperforms the BRT and LR model in terms of model performance. Model outputs suggest the dominant influence of surficial aquitard thickness and groundwater-fed irrigated area (%) on groundwater As. While, the north-central and southern regions of the Ganges River delta show low As-hazard (<10 µg/L), the western and north-eastern regions demonstrate elevated hazard level (>10 µg/L). An estimated 30.3 million people are found to be exposed to elevated groundwater As within the study area. Thus, our study demonstrates that such hybrid, predictive models are not only helpful in delineating the regional-scale distribution of groundwater As-hazard zones in the areas with limited As data but is also useful in identifying the possible exogenous forcing that may have led to the worst, natural pollution in human history.

Factors affecting the persistence of endangered Ganges River dolphins (Platanista gangetica gangetica).

The Ganges-Brahmaputra-Meghna and Karnaphuli (GBMK) River Basin in Nepal, India, and Bangladesh is among the world's most biodiverse river basins. However, human-induced habitat modification processes threaten the ecological structure of this river basin. Among the GBMK's diverse flora and fauna of this freshwater ecosystem, the endemic Ganges River dolphin (Platanista gangetica gangetica; GRD) is one of the most charismatic species in this freshwater ecosystem. Though a >50% population size reduction has occurred since 1957, researchers and decision-makers often overlook the persistence (or evolutionary potential) of this species in the highly fragmented GBMK. We define the evolutionary potential as the ability of species/populations to adapt in a changing environment by maintaining their genetic diversity. Here, we review how evolutionary trap mechanisms affect the dynamics and viability of the GRD (hereafter Ganges dolphin) populations after rapid declines in their population size and distribution. We detected six potential trap mechanisms that might affect the Ganges dolphin populations discretely or in combination: (a) habitat modification; (b) occurrence of finite and geographically restricted local populations; (c) ratio of effective to estimate population size; (d) increasing risk of inbreeding depression in genetically isolated groups; (e) at-risk behavioral attributes; and (f) direct fisheries-dolphin interactions. Because evolutionary traps appear most significant during low water season, they adversely affect demographic parameters, which reduce evolutionary potential. These traps have already caused local extirpation events; therefore, we recommend translocation among populations, including restoring and preserving essential habitats as immediate conservation strategies. Integrative evolutionary potential information based on demographic, genetic, and environmental data is still lacking. Thus, we identify gaps in the knowledge and suggest integrative approaches to understand the future of Ganges dolphins in South Asian waterways.

Role of aquifer media in determining the fate of polycyclic aromatic hydrocarbons in the natural water and sediments along the lower Ganges river basin.

Groundwater-sourced drinking water quality in South Asia, specifically India, is extremely stressed, mostly from the presence of many pervasive and geogenic pollutants. The presence and behavior of anthropogenic pollutants like polycyclic aromatic hydrocarbons (PAHs) are poorly investigated on a regional or basin-wide scale. The present study provides one of the first documentation of the presence and behavior of PAH in the aquifer sediments in the Ganges river basin. Lower and medium molecular weight PAHs, e.g., naphthalene, phenanthrene, and fluoranthene were detected in 79, 36, and 13% of samples (n = 25). The PAH level in groundwater was approximately five times lower than river water. The sorption behavior of PAHs were studied in experiments in presence/absence of organic carbon and by simulating advective transport of low to medium molecular weight PAHs, e.g., naphthalene, phenanthrene, and fluoranthene in aquifer sediments collected from agricultural, peri-urban, and urban areas. Naphthalene and phenanthrene adsorbed on quartz and kaolinite, but not on clay minerals like kaolinite. Fluoranthene adsorbed more favorably on kaolinite. Numerical modeling of the advective transport of PAHs in aquifers suggest up to 25 times faster movement of pollutants from irrigation-induced pumping, indicating the strong control of hydraulics on the spatial distribution of PAHs in subsurface.

Health and ecological risk assessment of emerging contaminants (pharmaceuticals, personal care products, and artificial sweeteners) in surface and groundwater (drinking water) in the Ganges River Basin, India.

Pharmaceuticals, personal care products (PPCPs), and artificial sweeteners (ASWs) are contaminants of emerging concern commonly found in the aquatic environments. In India, studies reporting environmental occurrence of these contaminants are scarce. In this study, we investigated the occurrence and distribution of 15 PPCPs and five ASWs in the river and groundwater (used untreated as drinking water) at several sites along the Ganges River. Based on the measured groundwater concentrations, we estimated the life-long human health risk from exposure to PPCPs through drinking. In addition, we estimated the risk of exposure to PPCPs and ASWs in the river water for aquatic organisms. The sum of detected PPCPs in the river water ranged between 54.7-826 ng/L, with higher concentrations in the severely anthropogenically influenced middle and lower reaches of the Ganges. The highest concentration among the PPCPs in the river water was of caffeine (743 ng/L). The sum of detected ASWs in river water ranged between 0.2-102 ng/L. Similar to PPCPs, the sum of ASWs in the river water was higher in the middle and lower reaches of the Ganges. In groundwater, the sum of detected PPCPs ranged between 34-293 ng/L, whereas of ASWs ranged between 0.5-25 ng/L. Negligible risk for humans was estimated from PPCPs in the drinking groundwater sources along the Ganges River, whereas moderate risks to PPCPs and ASWs (namely: caffeine, sulfamethoxazole, triclocarban, triclosan, and sucralose) were estimated for aquatic organisms in the Ganges River.

Spatial gradients of polycyclic aromatic hydrocarbons (PAHs) in air, atmospheric deposition, and surface water of the Ganges River basin.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous semi-volatile organic pollutants. Their environmental occurrence is of global concern as some of them are carcinogens, mutagens, and teratogens. In this study, concentrations and distributions of 16 priority PAHs (∑PAHs) were measured in air, atmospheric deposition, and surface water at various locations in Himalayan, Middle, and Lower Reaches of the Ganges River, covering a spatial transect of 2500km, during two seasons (pre-monsoon and monsoon). The concentration of ∑PAHs ranged between 2.2 and 182.2ngm-3 in air, between 186 and 8810ngm-2day-1 in atmospheric deposition, and between 0.05 and 65.9ngL-1 in surface water. Air concentrations were strongly correlated with human population density. In the Middle and Lower Reaches of the Ganges River, atmospheric PAHs were mainly attributed to fossil fuel combustion sources. In the Himalayan Reach the influence of forest fire or biomass combustion was evident during the dry pre-monsoon season. Seasonality in concentrations of PAHs in river water was evident in the Himalayan Reach of the river, as a probable consequence of climate-modulated secondary source intensity (i.e. releases from glacier melting). Seasonality faded in the Middle and Lower Reaches of the Ganges where water contamination is expected to mainly reflect anthropogenic primary sources. Ambient air concentrations were used to calculate the probabilistic incremental lifetime cancer risk (ILCR). It was expectedly found to be higher in the Middle and Lower Reaches compared to the Himalayan Reach. The strong correlation between population density and air concentrations suggests population density may be used as a surrogate variable to assess human health risk in data-sparse regions such as the Ganges River basin.

Source, distribution and ecotoxicological assessment of multielements in superficial sediments of a tropical turbid estuarine environment: A multivariate approach.

The work examined the distribution, possible sources and ecotoxicological assessment of 51 trace elements covering 13 sampling stations in surface sediments of coastal regions of Sundarban mangrove wetland and adjacent Hugli river estuary. The element concentrations exhibited an increasing trend towards downstream of the estuary (except lanthanides) with maximum enrichment for 22 elements at Gangadharpur (Sundarban region). According to Sediment Quality Guidelines (SQGs), the concentrations of Cu, As, Cr and Cd exceeded the Effects-Range-Low values, while Ni at certain stations exceeded the Effects-Range-Medium suggesting adverse effects on the sediment-dwelling organisms. The geoaccumulation index revealed that the stations were unpolluted to moderately polluted. Risk Index (357.61) and Enrichment factor (11.42) depicted that Nimtala station (upstream) was at high ecological risk zone. The result of PCA endorsed that organic carbon and clay fraction play crucial role in accumulating the elements in sediments. This pilot study contributes to a better understanding of the geochemistry of this complex deltaic ecosystem.

Characterization of the artisanal fishing communities in Nepal and potential implications for the conservation and management of Ganges River Dolphin (Platanista gangetica gangetica).

The Ganges River dolphin (Platanista gangetica gangetica) (GRD) is classified as one of the most endangered of all cetaceans in the world and the second scarcest freshwater cetacean. The population is estimated to be less than 2,000 individuals. In Nepal's Narayani, Sapta Koshi, and Karnali river systems, survival of GRD continues to be threatened by various anthropogenic activities, such as dam construction and interactions with artisanal fisheries. A basic description of the geographic scope, economics, and types of gear used in these fisheries would help managers understand the fishery-dolphin interaction conflict and assist with developing potential solutions. The main goal was to provide new information on the artisanal fishing communities in Nepal. The specific objectives were to identify, compile, and investigate the demographics, economics, fishing characteristics, and perception of fishermen about GRD conservation in the Narayani, Sapta Koshi, and Karnali rivers so conservation managers can develop and implement a potential solution to the GRD-fishery interaction problem in Nepal. Based on 169 interviews, 79% of Nepalese fishermen indicated fishing was their primary form of income. Fishermen reported fishing effort was greater in summer than winter; greatest in the afternoon (14:30 hrs ± 0:27) and during low water level conditions; and gear was set 4.8 ± 0.2 days/week. Fishermen reported using eight different types of monofilament nets (gillnets and cast nets). Sixty percent used gillnets less than 10 m long, and nearly 30% preferred gillnets between 10 and 100 m long; a few used gillnets longer than 100 m. Most fishermen reported they believed education, awareness, and changing occupations were important for GRD conservation, but they indicated that alternative occupational options were currently limited in Nepal. Nepalese fishermen acknowledged that fisheries posed a risk to GRD, but they believed water pollution, and dam/irrigation developments were the greatest threats.

Perfluoroalkyl substances (PFAS) in river and ground/drinking water of the Ganges River basin: Emissions and implications for human exposure.

Many perfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants. They have been widely used in production processes and daily-use products or may result from degradation of precursor compounds in products or the environment. India, with its developing industrialization and population moving from traditional to contemporary lifestyles, represents an interesting case study to investigate PFAS emission and exposure along steep environmental and socioeconomic gradients. This study assesses PFAS concentrations in river and groundwater (used in this region as drinking water) from several locations along the Ganges River and estimates direct emissions, specifically for PFOS and PFOA. 15 PFAS were frequently detected in the river with the highest concentrations observed for PFHxA (0.4-4.7 ng L(-1)) and PFBS (