The study compared the pollution level of 16 priority polycyclic aromatic hydrocarbons (PAHs) in the superficial sediments of the low stretch of the Hooghly River, LSHR, with that of the Sundarbans wetland, SW. Mean total PAHs levels were concerning, with mean individual loads exceeding legal limits and literature references, indicating a worsening scenario compared to past surveys. The mean of ∑PAHs in LSHR was significantly higher than in the SW, 2,106 ng/g vs. 1179 ng/g, with a hot spot of 13,785 ng/g. Thus, it is especially in the river location that contaminants accumulate with five compounds concentrating at higher rates compared to the natural area, 103

This study presents the first data on a 2018–2021 campaign to monitor polycyclic aromatic hydrocarbon levels, PAHs, in the final stretch of the Hooghly River in West Bengal, India. The range of sedimentary PAHs was 0–47,366 ng/g, higher than the ranges given by the literature for comparable study areas. The assay reveals an outstanding level of PAHs contamination in the fine sediments of the Hooghly River and Sundarban wetland, where the dominance of 4–6 ring PAHs was 83% of the total. The diagnostic ratios based on molecular ratios of PAHs show that the pollution comes mainly from the combustion of petroleum. The ratio of anthracene relative to anthracene plus phenanthrene, ANT/(ANT + PHE), was >0.30, which is higher than the reference discriminant ratio of >0.10, suggesting that PAHs were from the combustion source. In the meantime, fluoranthene over the sum of fluoranthene plus pyrene, FLT/(FLT + PYR), was >0.5 and indicated coal combustion, in agreement with the literature. The mean level of carcinogenic hydrocarbons was at 18% of the total measured PAH, with a peak of 91%, revealing significant potential risk for humans and ecosystems. The toxicity equivalence factors, TEF, of the individual PAHs and the total BaP equivalent toxicity, TEQ, were adopted as a comparison reference of sediment quality. At most sites, toxic effect ranges were classified as high and very high. The results of this research call for public authorities to remedy a situation of severe ecological risk.

The sediments of Ganga estuary, Hooghly River in India, were assayed for the effect of monsoon season on heavy metal loads over 2014-2017, a time frame never investigated before. As, Co, Cr, Cu, Pb, Zn, correlated with Mn, r 0.70-0.83, and Fe, r 0.70-0.76, meaning bounding to amorphous and/or crystallized iron and manganese oxyhydroxides. Pb and U were highly correlated, r of 0.86, and this may be likely linked to the important presence of the fertilizer industry. Ni instead had a negative correlation with the other metals indicating a different provenience. During the monsoon season, it was observed a significant increase in the number of metals significantly correlated with Mn, Fe, and Al, r of 0.80-0.86, due likely to weathering of transported continental detritus. All metals, except Ni, were significantly correlated with silt, r 0.73-0.83, which together with Mn, Fe and Al, is responsible for the increased transport of metals under monsoon period. Temporal trends of metals and ecological risk indexes split over two periods after the 2015 monsoon. The geo-accumulation index of As decreased from 3.82 to 1.14 and that of Ni increased from 2.74 to 3.99. On the overall the geo-accumulation index, enrichment factor, and pollution load indexes were several folds higher than those from the literature. Ni was the most threatening element for the aquatic ecosystem being above TEL and ERM quality guidelines by 100 and 98.9 %.

Phytoremediation is an efficient, economical, solar-driven innovative technology employed in plant species to remediate contaminated soil, sediment, water, and air using energy from sunlight. The chapter illustrates the potential of 14 native mangrove species for absorption, accumulation and transport processes of nine trace metal(loid)s in plant organs inhabiting in Indian Sundarban mangrove wetland. The mangroves exhibited a wide range of variations between the species and between sampling sites experiencing diverse environmental stresses. Avicennia officinalis (Acanthaceae) proved to be the highly promising plant species acting as a hyperaccumulator by assimilating and tolerating high trace metal (TM) concentrations without showing any sign of injury or stunted growth. These results suggest that mangrove plants may be used in a synergistic way to remediate and restore the TM contaminated estuary.

The iconic Ganges River dolphin Platanista gangetica gangetica is endemic to the Indian subcontinent and has been classified as the most endangered cetacean due to sharp decline in the population size of this obligatory freshwater animal. The species is vulnerable to multiple anthropogenic activities such as habitat fragmentation caused by construction of structural barriers (dams and barrages) and dredging activities, reduced freshwater flow, huge siltation load, depletion of fish stock, use of vulnerable gears, and lack of public awareness. Geographical expansion of artisanal fishing, poaching for collection of their flesh (used as fish bait) and fat and oil (used as an ointment for joint pain and gout), injuries and mortalities due to entanglement with fishing gear are other threats for the species. In addition, they can bioaccumulate several hazardous and toxic chemical pollutants in their body tissues, which are detrimental for their sustenance. Due to the outbreak of novel coronavirus (2019—COVID) pandemic the positive and negative impacts have also been observed and discussed. The following precautionary measures should be undertaken for their conservation: ban fishing in the dolphin hotspot areas and sanctuaries; multispecies management along with law enforcement and sustainable fishing practices; dolphin-fishery interactions should be solved through fishing gear modifications (e.g., mesh size).

The first half of the chapter deals with two emerging trace organic micropollutants (OMPs), namely pharmaceutically active compounds (PhACs) and endocrine disrupting chemicals (EDCs). Their residues in the environment may pose greater ecological risks to aquatic biota as they are in direct contact with wastewater contaminants. The environmental behavior of both PhACs and EDCs has not been very much explored, especially in tropical coastal marine systems. There is an urgent need for interdisciplinary research involving point source emission locations, coastal hydrodynamics, and exposure risks of these OMPs in coastal environments. The second half illustrates the origin, characteristics, and concentrations of the priority pollutants such as hexachlorocyclohexane (HCH) isomers (HCHs), dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDTs), hexachlorobenzene, and congeners of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons in the intertidal sediments of the coastal regions of Indian Sundarban wetland. In addition, a class of organobromine compounds (polybrominated diphenyl ethers) and the organofluorine compound (perfluorinated compounds) has also been discussed along with their suitable and sustainable remedial strategies.

Mangrove is recognized as a potential niche of microbial repository. The microbes along with their associated activities are highly important in terms of detritus generation and direct involvement in biogeochemical cycling of the nutrients. The tidal halophytic Sundarban mangrove ecosystem provides favorable environmental conditions for the development of microbial communities. The bacterial assemblages are represented by the Phyla Proteobacteria, Bacteroidetes, Acidobacteria, Firmicutes, Actinobacteria, Nitrospirae, Cyanobacteria, Planctomycetes, and Fusobacteria group. The diversity of a large number of fungal communities inhabited in mangrove regions has been poorly documented, dominated mostly by marine fungi along with a small group of terrestrial fungi. They are classified into three groups such as saprophytic (forming the largest group), parasitic, and symbiotic fungi. Several standard and cost-effective cutting-edge molecular sequencing techniques such as 16S ribosomal RNA (rRNA) and internal transcribed spacer rRNA sequencing are currently employed for sound identification of microbes present in an environmental sample and establishment of their phylogenetic relationships. Studies on the microbial community structure should be given high priority in any mangrove restoration or rehabilitation project throughout the world.

The transboundary Sundarban mangrove wetland (89002′ to 89055′E and 210 30′ to 22030′N) is situated in the Ganges-Brahmaputra-Meghna (GBM) delta. It is shared by southern Bangladesh (62%) and southern part of West Bengal State, India (38%), covering an area of 9630 and 4230 km2 respectively. The wetland represents the largest, continuous tract of mangrove forest in the world and of significant ecological and socio-economic importance. A haven for rich biodiversity, Sundarban harbors several rare and globally threatened plants and animals, such as Sundari tree, Horseshoe Crab, River Terrapin, Estuarine Crocodile, Olive Ridley Turtle, Gangetic River Dolphin and Royal Bengal Tiger. The key threats for this fragile mangrove ecosystem are land use changes, overexploitation of natural resources, chemical pollution from point and diffusive sources, reduced freshwater supply and silt deposition. The disappearance of a cluster of low-lying islands in Sundarban is a matter of great concern. This vulnerable delta is highly susceptible to the impact of climate change in the context of sea level rise, recurrence of severe tropical cyclones and storm surges. Both India and Bangladesh should implement bilateral monitoring programs to resolve those emerging problems and formulate the management strategies to restore this diversified and iconic mangrove ecosystem.

The rapid increase of the usage of plastic products in the modern era and lack of adequate waste management policies has led to their accumulation in the rivers beds and oceans posing severe threat to wildlife and human food chain. Bay of Bengal is the largest marine ecosystem with rich fauna of marine inhabitants and is hugely exploited by the plastic litter draining through the rivers Ganga-Brahmaputra-Meghna flowing through both India and Bangladesh. The question to be answered in this region is how to tackle the issue of marine plastic pollution with the aid of apt scientific findings and policy frameworks. Possible answers to these questions are being attempted in the present work by reviewing and evaluating the existing knowledge in science and law in both the countries to curb the menace of plastic in the Gangetic Bay of Bengal region. The review critically analyses the ill-effects of plastics on marine organisms globally and individuals residing on the coastal areas adjoining Bay of Bengal region. Further, the study finds that implementation of stringent laws and strengthening legal measures, in-depth understanding of the marine litter (plastics), robust waste management strategies, and spontaneous public involvement are mandatory to minimize the adverse effects of land-based plastics in this region of both the countries. The study hints out at a number of probable opportunities for the policy makers, environmentalists and marine biologists to work on for solving the plastic litter problem by adopting a holistic approach. The review finally concludes with the extensive research efforts needs to be carried out by an interdisciplinary approach and implications towards consumer driven changes which can create a safer environment for human race and marine organisms to survive.

This study investigated sediment spatial and seasonal distribution of trace elements (TEs) (n = 16) and human health effects along the Hooghly River Estuary (India). The index of geo-accumulation (Igeo), enrichment factor (EF), hazard quotient (HQ), modified hazard quotient (mHQ) and toxic risk unit (TRI) were calculated to estimate sediment pollution level, while hazard index (HI) and lifetime cancer risk (LCR) were used to assess TEs enrichment vs. human health. The concentrations (µg/g dry weight) of TEs were: Cd (0.01–1.58), Cr (41.98–105.49), Cu (16.41–51.09), Ni (28.37–63.90), Fe (22075–47919), Mn (423–630), Co (11.43–23.11), Zn (48.82–105.81), V (63.92–138.92), Pb (25.01–43.27) and Ti (0.18–3.50); As (2.92–16.26), B (59.34–98.78), Si (11.52–98.78); Be (1.71–4.81), Ba (95.23–293.72). From Igeo and EF, Cd was the major contaminant, while Ni presented moderate/high contamination (HQ and TRI). Children were more exposed to carcinogenic and non-carcinogenic risks compared to adults. For non-carcinogenic substances, no significant risk was found to both children and adults (HIs < 1). The LCR for Cr (3.924 × 10−4 for children) and As (1.379 × 10−4 for children) was higher than the threshold limit value (TLV, 10−4 and 10−6) indicating significant carcinogenic risks to be managed.

The spatial distribution of trace elements in surface sediments of the Hooghly estuary was studied over the monsoons in 2014–2017. As, Cd, Ni, Pb and U were two- to sixteen-fold the crust means with increasing levels toward the estuary, with Ni peak during the post-monsoon. Pearson’s correlation matrix, cluster analysis, enrichment factors and pollution index revealed the anthropic source and association of trace elements with Fe, Mn and Al and of Pb with U. Geoaccumulation index revealed for Ni an extremely contaminated situation at the estuary water during monsoon and for Cd a heavily contaminated situation at freshwater location. The potential contamination index was >6; thus, sediments were very severely contaminated by As, Cd and Ni with worst situation for As and Cd at fresh and brackish water and during post-monsoon. The overall ecological risk was severe, 300≤RI<600 at all sites and seasons, especially after the monsoon, at fluvial and brackish locations.

The present study shows the potential of an extracellular polymeric substance (EPS) produced by Bacillus licheniformis strain KX657843 isolated from earthworm (Metaphire posthuma) gut in the sorption of Cu(II) and Zn(II) and in flocculation. After harvesting bacterial cells from sucrose supplemented denitrifying culture medium, the EPS was extracted following ethanolic extraction method. The Fourier Transform Infrared Spectroscopy (FTIR) and 1H and 13C Nuclear Magnetic Resonance (NMR) of EPS revealed its functional groups, electronegative constituents, unsaturated carbon, and carbonyl groups. The negatively charged functional groups of carbohydrates and protein moiety of the EPS endowed it with heavy metal binding capacity through electrostatic interactions. The highest flocculation activity (83%) of EPS was observed at 4 mg L−1 and pH 11. The metal sorption by EPS increased with increasing pH. At pH 8, the EPS was able to remove 86 and 81% Cu(II) and Zn(II), respectively, from a 25 mg L−1 metal solution. 94.8% of both the metals at 25 mg L−1 metal solutions were removed by EPS at EPS concentration of 100 mg L−1. From Langmuir isotherm model, the maximum sorption capacities of EPS were calculated to be 58.82 mg g−1 for Cu(II) and 52.45 mg g−1 for Zn(II). The bacterial EPS showed encouraging flocculating and metal sorption properties. The potential to remove Cu(II) and Zn(II) implies that the EPS obtained from the earthworm gut bacteria can be used as an effective agent for environmental remediation of heavy metals and in bioflocculation.

A study was performed on a 32 Km stretch of the River Hooghly as part of a project under the Airborne Visible Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) scheme between Indian Space Research Organization (ISRO) and National Aeronautics and Space Administration (NASA). It was governed by 33 water quality variables comprising physical, chemical, biological and ecological ones. The selected stations were within the tidal realm of the estuary, constituting the lower-middle stretch of the river that was severely affected by anthropogenic perturbations. Chief biotic components studied were phytoplankton population density, primary and auxiliary phytopigments, and productivity in addition to chromophoric dissolved organic matter (CDOM). Majority of the study sites were observed with very low concentrations of dissolved oxygen along with significant shifts in primary production. Overall prevalence of Cyanophyceae and Bacillariophyceae was indicative of significant eutrophication. Reverse phase high performance liquid chromatography (HPLC) and radiometry revealed the presence of a large array of algal taxonomic groups through the detection of various primary and auxiliary phytopigments. The data and the study itself is of paramount importance being part of the ground truth verification initiative which will be used to render remote sensing techniques more precise in the future to better monitor the estuarine system. (C) 2020 Elsevier B.V. All rights reserved.

The geochemical fractionation and potential mobilization of cadmium, chromium, copper, nickel and lead were studied in surficial sediments (top 0–10 cm; <63 μm grain-size) of the Hooghly (Ganges) River Estuary, eastern part of India, using a sequential extraction procedure. The risk assessment was evaluated at three specific levels; i.e., enrichment level (enrichment factor, geo-accumulation index), the availability level (elements bound to different fractions, risk assessment code, Individual and Global contamination factors) and biological toxicity level (Potential ecological risk index; sediment quality guidelines). Different geochemical phases indicated heterogeneities in TE distribution patterns as follows: (i) Cd was dominant in the exchangeable phase and significant proportion of Pb was bounded to the reducible fractions; (ii) the potential mobile fraction (ΣF1 − F3) in the sediments was higher for Cd and Pb (>46%), reflecting their adverse impact on benthic organisms as they are weakly bound to the sediment and can migrate to water; (iii) a minor fraction of Cu (<10%) was found in the oxidizable fraction suggesting less environmental risk to the aquatic biota and (iv) the dominance of the Ni, Cr and Cu in the residual fraction supports the assumption of their geogenic origin. Both Cd and Cu posed medium to high ecological risk values based on risk assessment code (RAC). Global Contamination Factor (GCF) values allowed to identify the “pollution hotspots” in the study area.

The present work represented first study of the spatio-seasonal distribution of the multi-elements in the suspended particulate matter (SPM) of the tropical Hooghly river estuary (HRE), eastern part of India. The high load of SPM (20–3460 mg/l) might have induced negative impact on the phytoplankton density. The relative abundance of the studied elements exhibited the following decreasing trend (concentration in μg/g and %): Si(26.44 ± 3.75%) > Al(7.94 ± 1.52%) > Fe(6.17 ± 1.9%) > K(3.05 ± 1.5%) > Ca(1.97 ± 1.11%) > Mg(1.57 ± 1.71%) > Na(1.45 ± 8.40%) > Mn(1273 ± 2003) > Zn(178.43 ± 130.95) > V(151.54 ± 27.13) > Cr(147.08 ± 32.21) > Cu(62.06 ± 14.03) > Ni(49.64 ± 12.09) > Pb(21.5 ± 10.45). The accumulation of Ni, Cr, Pb, and Cu is mainly controlled by the formation of Fe hydroxides along with particulate organic carbon (POC) and salinity. The average geo-accumulation index (Igeo) and enrichment factor (EF) endorsed the substantial input of Cr (Igeo = 0.037; EF = 1.61) and Zn (Igeo = 0.123; EF = 2.07) from diffused pollution sources. From ecotoxicological point of view, the quality guidelines (QGs) suggested that Cr and Ni might possess frequent adverse biological effects. However, the mean probable effect level (PEL) quotient values revealed 49% probability of toxicity to the aquatic biota for five toxic elements (Cr, Ni, Cu, Zn, and Pb). The geochemical approaches, pollution indices, and statistical evaluation together revealed low to moderate contamination in the estuary. This baseline data would be beneficial in adopting proper management strategies for sustainable utilization and restoration of the water resources. The authors strongly recommend continuous systematic monitoring and installation of treatment plants for management of this stressed estuary.

This study investigated the chromium (Cr) detoxification mechanism-induced changes in growth and antioxidant defence enzyme activities in Chrysopogon zizanioides. Plant growth decreased by 36.8% and 45.0% in the shoots and roots, respectively, in the 50 mg/L Cr treatment. Cr accumulation was higher in root (9807 μg/g DW) than in shoots (8730 μg/g DW). Photosynthetic pigments and malondialdehyde content increased up to the 30 mg/L Cr treatment, whereas they declined at higher doses. The activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) were increased significantly with increasing of Cr dose but slightly declined at higher doses. Isozyme banding patterns revealed the expression of multiple bands for SOD, CAT and POX enzymes, and the band intensity decreased at high doses of Cr exposure. These results indicate that higher Cr doses increased the oxidative stress by over production of reactive oxygen species (ROS) in vetiver that had potential tolerance mechanism to Cr as evidenced by enhanced level of antioxidative enzymes, photosynthetic pigments, MDA contents. Therefore, vetiver has evolved a mechanism for detoxification and accumulates higher concentration of toxic Cr. This study provides a better understanding of how vetiver detoxifies Cr.