Efficient solid- and solution-state emissive reusable solvatochromic fluorophores for colorimetric and fluorometric detection of CN.

In this work, a novel organic receptor, CPI [(E)-3-(4-(9H-carbazol-9-yl)phenyl)-2-(1H-benzo[d]imidazol-2-yl)acrylonitrile], was rationally designed and successfully fabricated for selective and sole recognition of CN- ions over other competitive anions through an obvious chromogenic and ratiometric emission change in DMSO. The distinct and prominent color change upon the addition of CN- can be attributed to the typical ICT process, which is induced by the deprotonation of acidic NH protons in the imidazole moiety. The sensor displayed strong solvatochromic effects in commonly used organic solvents such as n-hexane, toluene, diethyl ether, DCM, THF, DMF and DMSO. The chemical structure of the sensor was characterized by single-crystal X-ray diffraction, 1HNMR, 13CNMR, IR and mass spectroscopy. Significantly, the probe can function as a fluorescence-based sensor for the efficient detection of low-level water in organic solvents. The solid-state emission properties of CPI were successfully applied to recognise cyanide in a solid-state platform with naked eye-visualized distinct color change. The probe can be made reusable by adding TFA into the CN- treated probe solution. The detection limit of CPI towards CN- was determined to be 4.48 × 10-8 M. More importantly, the sensor is capable of detecting CN- in food samples and has been employed for wastewater treatment. Besides, easy-to-prepare CPI-coated test strips provide a simple, reusable and easy-to-handle protocol for the qualitative identification of CN- conveniently. Finally, density functional theory and time-dependent density functional theory were performed to verify the experimental outcomes theoretically.

Adsorptive remediation of aqueous inorganic mercury with surfactant enhanced bismuth sulfide nanoparticles.

Heavy metal contamination in water is a growing threat, endangering the environmental stability. Mercury (Hg) is one of the most lethal heavy metals damaging the immune and nervous system irreversibly. A novel synthetic route to prepare bismuth sulfide (Bi2S3) nanoparticles in presence of the surfactant Pluronic (P123) was illustrated in this work. The sorption of Hg (II) by the nanoparticles was investigated. The surfactant assisted nanoparticles showed enhanced surface area and potential compared to the unmodified ones. The effects of adsorbent dose, pH, initial concentration, and temperature were investigated. The maximum Hg (II) adsorption capacity for the surfactant enhanced Bi2S3 was 832 mg/g at 303 K and pH 5. The distribution coefficient (Kd) of the order ∼106 ml/g indicated high selectivity of the synthesized adsorbent toward mercury ions. Chemisorption was identified to be the dominant mechanism of adsorption. The adsorbent also showed excellent reusability (>95%) after 5 cycles. The transport parameters involved in the adsorption, the effective pore diffusivity (Dp: 7.36 × 10-12 m2/s) and the mass transfer coefficient (kf: 1.52 × 10-6 m/s) were estimated from a first principle-based model.

Decoding and analysis of organelle genomes of Indian tea (Camellia assamica) for phylogenetic confirmation.

The NCBI database has >15 chloroplast (cp) genome sequences available for different Camellia species but none for C. assamica. There is no report of any mitochondrial (mt) genome in the Camellia genus or Theaceae family. With the strong believes that these organelle genomes can play a great tool for taxonomic and phylogenetic analysis, we successfully assembled and analyzed cp and mt genome of C. assamica. We assembled the complete mt genome of C. assamica in a single circular contig of 707,441 bp length comprising of a total of 66 annotated genes, including 35 protein-coding genes, 29 tRNAs and two rRNAs. The first ever cp genome of C. assamica resulted in a circular contig of 157,353 bp length with a typical quadripartite structure. Phylogenetic analysis based on these organelle genomes showed that C. assamica was closely related to C. sinensis and C. leptophylla. It also supports Caryophyllales as Superasterids.

Significant impacts of COVID-19 lockdown on urban air pollution in Kolkata (India) and amelioration of environmental health.

The fatal novel coronavirus (COVID-19) pandemic disease smashes the normal tempo of global socio-economic and cultural livelihood. Most of the countries impose a lockdown system with social distancing measures to arrest the rapid transmission of this virus into the human body. The objective of this study is to examine the status of air quality during and pre-COVID-19 lockdown and to recommend some long-term sustainable environmental management plan. The pollution data like PM10, PM2.5, O3, SO2, NO2 and CO have been obtained from State Pollution Control Board under Govt. of West Bengal. Similarly, various land surface temperature (LST) maps have been prepared using LANDSAT-8 OLI and LANDSAT-7 ETM + images of USGS. The maps of NO2 and aerosol concentration over Indian subcontinent have been taken from ESA and NASA. The digital thematic maps and diagrams have been depicted by Grapher 13 and Arc GIS 10.3 platforms. The result shows that the pollutants like CO, NO2 and SO2 are significantly decreased, while the average level of O3 has been slightly increased in 2020 during the lockdown due to close-down of all industrial and transport activities. Meanwhile, around 17.5% was the mean reduction of PM10 and PM2.5 during lockdown compared with previous years owing to complete stop of vehicles movement, burning of biomass and dust particles from the construction works. This study recommends some air pollution-tolerant plant species (in urban vacant spaces and roof tops) for long-term cohabitation among environment, society and development.

Cleaning the river Damodar (India): impact of COVID-19 lockdown on water quality and future rejuvenation strategies.

Globally, it is established that the partial lockdown system assists to improve the health of the total environment due to inadequate anthropogenic actions in different economic sectors. The ample research on fitness of environment has been proved that the strict imposition of lockdown was the blessings of environment. The river Damodar has historical significance and lifeline for huge population of Jharkhand and West Bengal state of India but in the recent years the water quality has been deteriorated due to untreated industrial effluents and urban sewage. The main objective of this study is to examine the water quality of river Damodar during and prelockdown phase for domestic use and restoration of river ecosystem. A total of eleven (11) effluent discharge sites were selected in prelockdown and during lockdown phase. A new approach of water quality assessment, i.e., water pollution index (WPI) has been applied in this study. WPI is weightage free, unbiased method to analysis of water quality. The result shows that the physical, chemical and heavy elements were found beyond the standard limit in prelockdown period. The cation and anion were arranged in an order of Na2+ > K+ > Ca2+ > Mg2+ and Cl- > So4 - > No3 - > F- in both the sessions. WPI of prelockdown showed that about 100% water samples are of highly polluted. WPI of lockdown period showed that around 90.90% samples improved to 'good quality' and 9.10% of samples are of 'moderately polluted.' Hypothesis testing by 't' test proved that there was a significant difference (ρ = 0.05%) in values of each parameter between two periods. Null hypothesis was rejected and indicated the improvement of river water quality statistically. Spatial mapping using Arc GIS 10.4 interpolation (IDW) helps to understand spatial intensity of pollution load in two periods. This research study should be helpful for further management and spatial diagnosis of water resource of river Damodar.

Retraction Note to: Antioxidants and ROS scavenging ability in ten Darjeeling tea clones may serve as markers for selection of potentially adapted clones against abiotic stress.

[This retracts the article DOI: 10.1007/s12298-013-0187-1.].

Antimutagenic and anticancer activity of Darjeeling tea in multiple test systems.

BACKGROUND: Darjeeling tea, a most popular variety of black tea, though consumed by the people in different parts of world but its beneficial health effects have not been investigated in details. In this study, the antimutagenic and anticancer effect of Darjeeling tea extract (DTE) has been evaluated. METHODS: Antimutagenic activity of the DTE was carried out in two different strains of Salmonella typhimurium by AMES test against a known mutagen benzo[a]pyrene (B[a]P) with S9 activation. Moreover, anticlastogenic property of DTE was also measured by micronuclei formation (MN) against B[a]P with S9 activation in human lymphocytes. The anticancer activity of the same was studied on U937 cell line. Here, Human PBMCs were used as the normal cell control to identify selective anticancer activity of the extract against U937 cells. RESULTS: The results showed significant antimutagenic activity on bacterial strains. A significant decrease in MN was also observed in the DTE treated human lymphocyte cultures pretreated with B[a]P when compared with B[a]P treated cultures alone. The study clearly exhibited anticancer activity of the extract on U937 cell line. Further studies also revealed that apoptosis induction is an important mechanism behind the anticancer effect of DTE. CONCLUSION: Overall, this study indicates that DTE has significant antimutagenic and anticancer activities on bacterial and mammalian cells respectively.

Fabrication of thiosemicarbazone-based Pd(II) complexes: structural elucidations, catalytic activity towards Suzuki-Miyaura coupling reaction and antitumor activity against TNBC cells.

Currently, there are many uses of metal complexes, especially in the fields of medicinal chemistry and catalysis. Thus, fabrication of new complexes which perform as a catalyst and chemotherapeutic drug is always a beneficial addition to the literature. Herein, we report three heterocyclic thiosemicarbazone-based Pd(II) complexes [Pd(HL1)Cl] (C1), [Pd(L2)(PPh3)] (C2) and [Pd(L3)(PPh3)]Cl (C3) having coligands Cl and PPh3. Thiosemicarbazone ligands (H2L1, H2L2 and HL3) and the complexes (C1-C3) were characterized methodically using several spectroscopic techniques. Single-crystal X-ray diffraction methods reveal that the structural environment around the metal center of C2 is square planar, while for C1 and C3 it is a slighty distorted square plane. The supramolecular network of compounds was built via hydrogen bonds, C-H⋯π and π⋯π interactions. Density functional theory (DFT) study of the structure of the complexes supports experimental findings. The application of these complexes as catalysts toward Suzuki-Miyaura coupling reactions has been examined with various aryl halides and phenyl boronic acid in PEG 400 solvent. The complexes displayed good biomolecular interactions with DNA/protein, with a binding constant value of the order of 105 M-1. C3 showed greater binding efficacy toward these biomolecules than the other complexes, which might be due to the cationic nature of C3. Furthermore, antitumor activity of the complexes was studied against the human triple-negative breast cancer (TNBC) cell line MDA-MB-231. It was found that C3 was more toxic (IC50 = 10 ± 2.90 µM) toward MDA-MB-231 cells than the other complexes. A known chemotherapeutic drug, 5-fluorouracil, was included as positive control. The programmed cell death mechanism of C3 was confirmed. Additionally, complex-induced apoptosis was confirmed and occurred via a mitochondria-dependent (intrinsic) pathway.

Antioxidants and ROS scavenging ability in ten Darjeeling tea clones may serve as markers for selection of potentially adapted clones against abiotic stress.

Ten Darjeeling tea clones (BT15/263, RR17/144, B777, T253, B157, Sundaram, HV39, AV2, K1/1 and TTV1) were collected from the experimental garden of Darjeeling Tea Research and Development Centre, Kurseong. Total phenol, flavonoids and two antioxidating enzymes (peroxidase and superoxide dismutase) were estimated. The total phenol ranged between 241 and 28 GAE mg g(-1) of leaf dry weight. The highest amount obtained in four clones, B15/263 (241.47), RR17/144 (221.2), B777 (154.54) and B157 (140.23 mg g(-1)). Flavonoids were estimated as Catechin equivalent (CE) and ranged between 56.88 and 20.81 CE mg g(-1) leaf dry weight. Higher amounts occurred in BT15/263 (56.88 mg g(-1)), B777 (56.69) and RR17/144 (48.63). Antioxidant activities were measured following DPPH and ABTS free radicle scavenging procedures and the results were well according to total polyphenol content among the clones (in total phenols, ranges of correlation in DPPH assay were r (2) = 0.990-0.989, p ≤ 0.05; in flavonoids r (2) = 0.954, p ≤ 0.01-0.987, p ≤ 0.05). Similarly, ABTS percent scavenging results were quiet significant. The IC50 values were determined for both DPPH and ABTS assay. PAGE expressions of isoforms in two antioxidative enzymes and quantification of them also varied much among the investigated clones. The incidence of total phenols, flavonoids, PRX and SOD and ROS scavenging assay in in-situ condition, might be used as biochemical markers towards the superior adaptability against abiotic stress. In the present work, four clones (B15/263, B777, RR17/144 and B157) would be designated as comparatively better suited to the predicted abiotic stress.

A chemodosimetric approach for the visual detection of nerve agent simulant diethyl chlorophosphate (DCP) in liquid and vapour phase.

In this work, a novel fluorescent ratiometric switch, 8-((6-(1H-benzo[d]imidazol-2-yl)pyridin-2-yl)methoxy)quinoline (BIPQ), has been introduced for sensing an organophosphorus (OP) chemical vapor threat, diethyl chlorophosphate (DCP), the low-toxic mimic of the real nerve agent sarin (GB). BIPQ is efficient at detecting DCP in both solution and gaseous phase and has potential practical application with high sensitivity and selectivity. The probe shows significant ratiometric emission in the presence of DCP along with a distinct color change from blue to cyan under UV light. The sensing mechanism of the chemodosimeter is based on the generation of a new adduct, BIPQ-DCP, through a nucleophilic substitution reaction with DCP followed by a ring-closure process to form the final product. The detection limit of BIPQ for DCP was determined to be in the order of 10-8 (M) in the liquid state. DFT and TDDFT computational techniques were carried out in order to interpret the electronic properties theoretically.

Facile synthesis of novel NNO-tethered copper(II) complexes: characterization details, theoretical studies, promising enzyme-like activities, and biomolecular interactions.

Given the ubiquitous and multifaceted role of copper ions in various biological processes, we report herein the one-pot facile synthesis, X-ray structure, Hirshfeld surface analysis, enzyme-like activities, and biomolecular interactions of three mononuclear copper(II) complexes, [Cu(L)(X)] (1-3) with a tridentate quinoline-based salicylaldimine Schiff base (LH) having an N2O donor set where X denotes NCS, N3, and NO3 for complexes 1, 2, and 3, respectively. Single-crystal X-ray study, spectroscopic techniques, DFT, and TD-DFT calculations were all used to fully characterize the complexes. The bio-inspired catalytic activities of the synthesized complexes were spectrophotometrically evaluated for the aerial oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-aminophenol (OAPH) in acetonitrile. The results of ESI mass spectrometry, EPR analysis of the reaction mixture, and DFT computations established that the aforementioned oxidation is metal-mediated and radical-driven, leading us to propose a viable mechanistic scheme. In complex 3, coordinated nitrate probably confers greater lability, allowing it to be the most effective enzyme for catecholase and phenoxazane-synthase activities. The biological activity of complexes 1-3 and the ligand LH towards calf thymus DNA and proteins (bovine serum albumin (BSA)) was explored using absorption and fluorescence spectral titrations, which affirmed that the compounds underwent avid binding with DNA, with high binding affinities (Kb) of approximately 104-105 M-1. The observed DNA binding constants and viscosity measurement data suggested an intercalative mode of DNA binding with the copper(II) complexes. Spectral evidence also supports the high binding propensity (on the order of approximately 105 M-1) of the complexes with the protein. They actively suppressed the protein's intrinsic fluorescence in a static quenching mode, as further determined by fluorescence lifetime titration of protein with the complexes. Circular dichroism and synchronous spectroscopic experiments supported the protein's conformational alterations mediated by copper(II) complexes (1-3) in the microenvironment of the tryptophan residue of the protein. The typical binding distance between BSA and complexes was also computed using fluorescence resonance energy transfer. Of the three complexes (1-3), complex 3 stands out as the most efficacious.

Changes of growth, photosynthesis and alteration of leaf antioxidative defence system of tea [Camellia sinensis (L.) O. Kuntze] seedlings under aluminum stress.

Tea [Camellia sinensis (L.) O. Kuntze] is an aluminum (Al) hyperaccumulator plant and is commercially important due to its high content of antioxidants. Although Al induced growth is well-known for the plants growing in acid soil, yet the cause underlying the stimulatory effect of Al has not been fully understood. To investigate the possible role of Al in growth induction, we studied morphological, physiological as well as biochemical changes of tea plant under different Al concentrations (0-4,000 µM). In hydroponics, Al (15 µM), enhanced shoot and root growth, but at higher concentrations, it caused oxidative damage which culminated in a cascade of biochemical changes, Al content increased concurrently with the maturity of the leaf as well as stem tissues than their younger counterparts. Hematoxylin staining indicated that Al accumulation started after 6 h of exposure in the tips of young roots and accumulation was dose dependent. The physiological parameters such as pigments, photosynthetic rate, transpiration and stomatal conductance were declined due to Al toxicity. Alteration in activated oxygen metabolism was also evidenced by increasing lipid peroxidation, membrane injury, evolution of superoxide anions and accumulation of H(2)O(2). Contents of phenols initially exhibited an acceleration which gradually plummeted at higher levels whereas total sugar and starch contents decimated beyond 15 µM of Al concentration. Activities of antioxidant defense enzymes were increased with the elevated concentration of Al. Expression of citrate synthase gene was up-regulated in the mature leaves, young as well as old roots simultaneously with increased concentration of Al in those parts; indicating the formation of Al-citrate complex. These results cooperatively specified that Al concentration at lower level promoted growth but turned out to be a stressor at elevated stages indicating the sensitivity of the cultivar (T-78) to Al.

Variation and dispersal of PM10 and PM2.5 during COVID-19 lockdown over Kolkata metropolitan city, India investigated through HYSPLIT model.

The higher concentration of PM10 and PM2.5 in the lower atmosphere is severely harmful for human health and it also makes visibility diminution along with weather and climate modifications. The main objective is to find out the spatiotemporal variation and dispersal of PM10 and PM2.5 along with COVID-19 infection in the dusty city Kolkata. The consecutive two years PM10 and PM2.5 data of different stations have been obtained from State Pollution Control Board, Govt. of West Bengal. Forward trajectory analysis has been done through HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model to find the path and direction of air particles. The result showed that the various meteorological or environmental factors (such as temperature, relative humidity, wind, wind speed, pressure and gusty wind) and geographical location regulate the spatiotemporal variation of PM10 and PM2.5. These factors like high temperature with relative humidity and strong wind influence to disperse the particulate matters from north to south direction from city to outside during summer in Kolkata metropolitan city. During summer (both pre and lockdown years), the height of particles is extended up to 1000 m owing to active atmospheric ventilation whereas in winter it is confined within 100 m. The HYSPLIT model clearly specified that the particles dispersed from south, south-west to north and north east direction due to strong wind. The constant magnification of PM10 and PM2.5 in the lower atmosphere leads to greater frequency of COVID-19 infections and deaths. In Kolkata, the one of the crucial reasons of high infection and deaths (COVID-19) is co-morbidity of people.

Assessment of household water consumption during COVID-19 pandemic: a cross-sectional web-based study in India.

The fatal novel COVID-19 creates precarious threats to humans through speedy diffusion. This virus not only disrupts human health but also makes multidirectional loss and slowdown of modern earth. Almost all countries strictly imposed lockdown and social distancing norms to prevent the infection of COVID-19 virus. In almost all parts of the world, people are using more water for washing, cleaning, bathing and hand washing practices. As a result, per capita water demand along with expenditure have been significantly increased. The principal objective of this study is to evaluate the household level water consumption status and to improve the water security with management for future. The current study has been conducted among the general population of India to assess household level water consumption through internet E-Surveys Google form from August 18 to September 8, 2020. Around 1850 respondents have sent their comments from different sites (rural and urban areas in various climatic regions) of Indian subcontinent. The results show the tremendous increase of water usage along with electrical consumption and expenditure during COVID-19 pandemic situation. Our results revels that 10%, 15% and 17% of higher water consumption per day in rural, urban and peri-urban residential respectively. We hypothesize that the reasons for the increasing water demand and household consumption per day may be found in changed behavioral routines through bathing, washing clothes, and hand washing practices. This web-based study also suggests that few alternative and dependable management techniques i.e. rain water harvesting can be installed to fight the crisis and for the sustainable future. Subsequently, research and development are highly required for long-term management of water resources or reuse of water.

Enhanced photodegradation of reactive dyes in textile effluent with CoFe2O4/g-CN heterostructure-mediated peroxymonosulphate activation.

Graphitic carbon nitride (g-C3N4) was employed as a sacrificial substructure and two-dimensional support to develop magnetic cobalt ferrite-carbon nitride (CoFe2O4/g-CN) composite via a one-step solid combustion method. The catalyst activated peroxymonosulphate (PMS), through the interconversion of Co2 + /3+|surf. and Fe2 + /3+|surf. on its surface for degradation of reactive dyes (RDs). Excellent ferromagnetic nature (44.15 emu g-1) of the catalyst led to its efficient magnetic separation. With an optimum catalyst and PMS dose of 0.4 g L-1 and 1.5 g L-1, 99% RD removal was achieved for textile effluent (pH 9.5-10), under UV irradiation (48 W). In-depth radical scavenging experiments and EPR analysis confirmed the dominance of radical-based degradation process. Plausible degradation and mineralization pathways of RDs were proposed through identification of intermediates by LCMS/MS analysis. In brief, this study elucidates an exclusive strategy towards the use of g-C3N4 as fuel for facile synthesis of magnetic CoFe2O4/g-CN as a remarkable photocatalyst for activation of PMS towards mineralization of various industrially relevant RDs.

Evaluation of wetland ecosystem health using geospatial technology: evidence from the lower Gangetic flood plain in India.

The floodplain wetland habitat in the lower Gangetic plains of West Bengal played a significant role in protecting from environmental degradation like pollution, lowering groundwater table, natural hazards, and others as well as supports for human wellbeing. Thus, it is needed to investigate the health status of wetlands and suggest restoration strategies to protect the livelihood patterns dependent on wetlands. This paper presents the health of the wetland ecosystem by comprising the wetland ecosystem health index (WHI) in 2011 and 2018 at the block level of Malda district, as a part of the lower Gangetic flood plain using the pressure-state-response model (PSR model) and AHP method. A total number of six Landsat satellite images and statistical census data were used to determine the wetland health. Wetlands are classified as very healthy (2.81-3.33), healthy (2.41-2.80), sub-healthy (2.01-2.40), unhealthy (1.61-2.00), and sick (0-1.60) category on the basis of the wetland ecosystem health index score. The results of this study showed that the wetlands located surrounding English Bazar, Manikchak, Ratua-II, and Kaliachak-II blocks have a sub-healthy to very healthy condition in 2011 but changed to unhealthy to sick category in 2018 due to the increase of rapid urbanization, population density, and development activities. These areas have belonged to the sub-healthy to sick category in the year 2011 as well as 2018 due to high wetland pressure. Our observation reveals that the ecosystem service value provided by wetlands decreased by 62.51% and 20.46 in the observed period. Management of WEH should emphasize on large (>100 ha) and medium (51-100 ha) sizes of wetlands in the Diara region of West Bengal. Developing local-level institutions and setting restoration goals are useful strategies to manage wetland resources, and protecting biodiversity should be guided by the Government organization and NGOs.

Variation and correlation between ultraviolet index and tropospheric ozone during COVID-19 lockdown over megacities of India.

Worldwide spread out of COVID-19 in a short-time has brought a significant decline of road traffic, tourist flow and industrial ventures. During this emergency period, the restricted human dealings with nature have appeared as blessing for health of the total environment. The variation of atmospheric O3 may modulate the range of UV index (UVI) at any region of the earth. The objective of the study is to examine the variation of UV index over the megacities of India with respect to tropospheric O3 level modification during COVID-19 lockdown. The meteorological or environmental data (temperature in °C, gust in km/h, wind speed km/h, relative humidity in %, air pressure in mb and cloud cover in okta) of four selective megacities of India (Kolkata, Chennai, Delhi, Mumbai) during and pre lockdown period have been obtained to comprehend about the variation of UV index and tropospheric O3. The descriptive statistical applications i.e. standard deviation, standard errors and K-means clustering have been done through standard statistical software. In the present study, t-test has been used to understand level of significance of surface O3 and UVI during pre-lockdown (2019) and lockdown (2020) phase. The result shows that the four major megacities in India namely New Delhi, Mumbai, Kolkata and Chennai have experienced the vibrant diminution in terms of the concentration of UV index with slightly increasing the tropospheric O3 level during the lockdown phase. The higher accumulation of O3 during the lockdown in the lower atmosphere of four megacities does not exceed the permissible limit. The excess amount of O3 has remarkably contributed to trap the harmful UV radiation which has lowered the UVI in these worst polluted megacities of India. In the meantime, the prominent reduction of NOx during the lockdown period decreases the titration impact to O3 and this mechanism helps to revitalize the ozone concentration level. The uniqueness of the current study is highlighted the ground reality regarding reduction of UV index and amplification of tropospheric O3 concentration during lockdown phase. This study definitely assists to make new environmental policy, act and law for recover the health of the total environment.

Significant reduction of carbon stocks and changes of ecosystem service valuation of Indian Sundarban.

The Sundarban mangrove or tidal influenced natural ecosystem is extremely productive and providing multiple goods and services to millions of people. In the last few decades, the quality and quantity of mangrove ecosystem are being deteriorated. The main objectives of this current research are (i) to investigate the ecosystem service values (ESVs) using a time series satellite data (1975, 2000 and 2020) and different unit values (ii) to analyze the dynamic pattern of carbon sequestration through InVEST model and (iii) determination of ESVs change hotspots by Getis-Ord Gi* method. Here, mangrove forest has the highest ecosystem service value and highest carbon sinker. The total loss of ESVs was estimated 3310.79 million USD during last 45 years in Sundarban Biosphere Reserve (SBR) due to high natural and anthropogenic adversities. InVEST model also revealed that the total static carbon storage over the study area was 48.87, 46.65 and 43.33 Tg for the year 1975, 2000 and 2020 respectively. Total 6313944 mg/6.31Tg loss of carbon has been observed in the case of mangrove forest during the overall study period (1975-2020). So, illegal human encroachment should be strictly (through law and regulations) restricted within Sundarban mangrove ecosystem for the benefits of people.

Effects of COVID-19 lockdown and unlock on the health of tropical large river with associated human health risk.

River Damodar (India) is one of the most significant tropical large rivers and this river is carrying predominantly industrial effluents, urban sewage, and non-degradable chemical agricultural fertilizers. Several industries, cities, and townships directly depend on this important river throughout the year. It is highly essential to evaluate its surface water quality, characteristics, and improvement status during the COVID-19 lockdown and unlock phases. The major objectives of the present study are to analyse changing nature of heavy metals (Zn, Cd, Pb, Ni, Cr, and Fe) and microbial load (TVC, TC, and FC) of river water and to identify heavy metals impact on water quality and human health in pre, during, and after unlocking of COVID-19 lockdown. Here, a total of 33 water samples have been collected in the pre-lockdown, lockdown, and unlock phases. The results showed that decreasing trend of the microbial load was found in the lockdown phase. Heavy metal pollution index (HPI) illustrated that all samples are highly polluted (HPI > 150) during the pre-lockdown phase, while during the lockdown phase; HPI showed that around 54.54% of samples have been positively changed (low pollution level). During the unlock phase, 45.45% of samples were again amplified to the high pollution level. Pearson's correlation coefficient and hierarchical cluster analysis indicated strong relation among heavy metals with faecal coliform at a 0.05% level of significance. Noncarcinogenic hazard index (HI) shows the higher possibility of health risk (HI > 1) particularly for children in all the phases and during the lockdown phase, 36.36% of samples showed no possible health risk for adults (HI < 1). However, HI of dermal contact showed no possible health risk for children and adults in the assessment periods. This applied research can definitely assist planners and administrators in making effective solutions regarding public health.

PM2.5 concentration prediction during COVID-19 lockdown over Kolkata metropolitan city, India using MLR and ANN models.

Kolkata is the third densely populated city of India and Kolkata stands in the World's 25 most polluted cities along with 10 worse polluted cities in India. The relevant study claims that due to the imposition of lockdown during COVID-19 pandemic, the atmospheric pollution level has been significantly reduced over the metropolitan city Kolkata like other cities of the world. The main objective of this study is to predict the concentration of PM2.5 using multiple linear regression (MLR) and artificial neural network (ANN) models and similarly, to compare the accuracy level of two models. The concentration of PM2.5 data has been obtained from state pollution control board, Govt. of West Bengal and daily meteorological data have been collected from the world weather website. The results show that non-linear artificial neural network model is more rational compared with multiple linear regression model due to its high precision and accuracy level (in respect to RMSE, MAE and R2). In this research artificial neural network (ANN) model exhibited higher accuracy during the training and testing phases (root mean square error (RMSE), mean absolute error (MAE) and R2 indicate 3.74, 1.14 and 0.91 respectively in training phase and 2.55, 4.32 and 0.69 in testing phase respectively). This model (ANN)) can be applied to predict the concentration of PM2.5 during the execution of urban air quality management plan.