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Smart concrete is capable of self-assessing its state of stress and strain. It is produced by tailoring the electrical conductivity of concrete with the addition of conductive materials such as carbon fiber. This paper aims at determining the electrical conductivity of smart concrete materials with randomly dispersed carbon fibers. It unravels the conduction mechanism and establishes a theoretical basis of the percolation threshold for conduction. A numerical model for concrete with carbon fiber is developed. The electrical conduction through the concrete is calculated by solving the governing equations based on Kirchhoff's reformulation of Ohm's Law. More than ten thousand cases with varying fiber topologies, fiber fraction ratios and aspect ratios have been generated to account for the randomness of distribution and their electrical properties are evaluated. By analyzing those results, the mechanism behind the percolation threshold is explained. Finally, an algebraic relationship is posited to determine the percolation threshold has been evaluated. The relationship has been validated with experimental results. The results are extremely valuable for the design of self-sensing smart concrete. [ABSTRACT FROM AUTHOR]

Although geogenic Arsenic (As) contamination is well-recognized in northern Chile, it is not restricted to this part of the country, as the geological conditions favoring As release to the human environment exist across the country as well, although not at the same level, based on comparatively fewer studies in central and southern Chile. The present work provides a critical evaluation of As sources, pathways, and controls with reports and case studies from across the country based on an exhaustive bibliographic review of its reported geogenic sources and processes that affect its occurrence, systematization, and critical revision of this information. Arc magmatism and associated geothermal activities, identified as the primary As sources, are present across the Chilean Andes, except for the Pampean Flat Slab and Patagonian Volcanic Gap. Metal sulfide ore zones, extending from the country's far north to the south-central part, are the second most important geogenic As source. While natural leaching of As-rich mineral deposits contaminates the water in contact, associated mining, and metallurgical activities result in additional As release into the human environment through mining waste and tailings. Moreover, crustal thickness has been suggested as a principal controlling factor for As release, whose southward decrease has been correlated with lower As values. [ABSTRACT FROM AUTHOR]

The Ganges River delta complex contains a transboundary aquifer system shared between India and Bangladesh. Although it serves as the main freshwater source for the population inhabiting the delta, the aquifer system is severely contaminated with arsenic (As). This study aimed to determine the control of the delta hydrostratigraphy on the regional-scale depth distribution of As within the aquifer system. We developed the first high-resolution, regional-scale, transboundary hydrostratigraphic model of the Ganges River delta and analyzed the patterns of As distribution as a function of the hydrostratigraphy. Model results indicate that, despite the presence of a single aquifer system across the delta, the hydrostratigraphy is spatially variable and can be architecturally divided into three distinct aquifer subsystems from northwest to southeast: a single, thick continuous aquifer (type I); a vertically segregated, semiconfined aquifer subsystem (type II); and a multilayered, nearly confined aquifer subsystem (type III). Results indicate that the spatial distribution of As is characteristically different in each subsystem. In the type I aquifer, As concentrations tend to be homogeneous at all depths, while in type II and type III aquifers, As concentrations sharply decrease with depth. The intervening aquitards in the type II and type III aquifer subsystems appear to act as natural barriers to infiltration of surficial As or organic matter-rich water to the deeper aquifer zones. This delineation of the regional-scale hydrostratigraphic architecture and resulting understanding of its plausible controls on the depth-distribution of As within the delta should significantly aid in the systematic framing of sustainable management plans for the As-safe aquifers within the Ganges River delta aquifer system. [ABSTRACT FROM AUTHOR]

Introduction: During the refining and packing of tea, a very fine dust is formed which is called the tea fluff. Exposure to this fluff has been reported to cause ventilatory defects on chronic exposure. Objective: To determine the association between air quality of the different work sections of tea gardens and the ventilatory functions of the workers. Methodology: An observational analytical study with cross sectional design was conducted on 400 apparently healthy individuals working in different sections of 4 tea gardens. Data on sociodemographic characters of the population, particulate matter (PM) and air quality (AQI) was recorded. All participants underwent spirometric evaluation. Results: The mean (SD) age of the study population was 37.8 (8) years. Most (67%) of the study participants were females. The participants were engaged in the job for a mean (SD) of 4.7 (2.7) years. The median distribution of PM2.5, PM 10 and AQI are progressively higher from the garden section to the dry section. A significant correlation between FVC and PM2.5 and PM10 is seen. FEV1 and FEV1/FVC shows a significant correlation with all air quality parameters while FEF25-75 is correlated to none of them. Comparison of the three models to predict the spirometric variables show that even after adjustments, the FEV1 is significantly associated with air quality parameters, FEV1/FVC is significantly associated with the air quality parameters and age while the FEF25-75% is dependent on the age of the participant. Conclusion: There is a strong correlation between the ventilatory parameters and the cumulative exposure of PM2.5, PM10 and AQI, which persists even after adjustment for confounders. [ABSTRACT FROM AUTHOR]

Background: Properly constructed single best-answer multiple choice questions (MCQs) or items assess higher-order cognitive processing of Bloom's taxonomy and accurately discriminate between high and low achievers. However, guidelines for writing good test items are rarely followed, leading to generation and application of faulty MCQs. Materials and Methods: During lockdown period in 2020, internal assessment was taken through online mode using Google Forms. There were 60 'single response type' MCQs, each consisting of single stem and four options including one correct answer and three distractors. Each item was analyzed for difficulty index (Dif I), discrimination index (DI), and distractor efficiency (DE). Results: The mean of achieved marks was 42.92± (standard deviation [SD], 5.07). Dif I, DI, and DE were 47.95± (SD 16.39) in percentage, 0.12± (SD 0.10), and 18.42± (SD 15.35), respectively. 46.67% of the items were easy and 21.66% were of acceptable discrimination. Very weak negative correlation was found between Dif I and DI. Out of total 180 distractors, 51.66% were nonfunctional one. Conclusion: Item analysis and storage of MCQs with their indices provides opportunity for an examiner to select MCQs of appropriate difficulty level as per the need of assessment and decide their placement in the question paper. [ABSTRACT FROM AUTHOR]

Ultrasonic wave–based imaging is a popular nondestructive tool used to inspect RC structures. The inherent heterogeneity of concrete poses a great challenge for imaging incipient damage to concrete. This paper presents an algorithm for improving the quality of images obtained from a considerably reduced data set. A set of RC samples was prepared. The reflections of ultrasonic waves were recorded by placing a transmitter and a receiver on the surface of the concrete. The signals were processed to create an image of a section of the specimens, and the images were enhanced through a set of three-step cascading filters. The spatial apodization (SA) filter is first applied to control the spatial directivity of the ultrasonic transducers. At the second level, a contrast improvement (CI) filter is applied to further reduce ghosting. The third filter is the moving average–based reflection localization filter. Images produced by the algorithm are compared with those produced via conventional techniques in terms of clarity and contrast. It is demonstrated that the cascading filters produce a clearer image with a considerably smaller data set. [ABSTRACT FROM AUTHOR]

Top-bar defects in reinforced concrete are voids that are observed below the reinforcing bars that are at an elevation of more than 300 mm. The authors have demonstrated a new ultrasonic guided wave technique to non-destructively detect top-bar defect (Wang, Mukherjee et al., 2021). It has been reported that bars with top-bar defect corrode is faster than other bars. The corrosion also manifests in a different manner in these bars. This paper proposes a guided ultrasonic wave-based non-destructive method for monitoring corrosion in reinforced concrete with top-bar defect. Concrete wall samples with bars of various extents of top-bar defect were subjected to accelerated corrosion. Simultaneously, the bars have been monitored with guided ultrasonics. The investigation revealed that top-bar defect has a significant influence on the corrosion process. The destructive tests performed at the end of corrosion exposure revealed that the top-bar specimens had a significant loss of strength than the bars with a good bond. The proposed non-destructive has been calibrated to assess the residual capacities of corroded bars in presence of top-bar defect. [ABSTRACT FROM AUTHOR]

Background: Appropriateness of admissions and inpatient length of stay (LOS) are important factors controlling health-care expenditure. The current study was conducted to assess the proportion of appropriate admissions among 29-day to 12-year--old aged patients admitted to pediatric wards of a tertiary health-care center in one month and evaluate inappropriate LOS among them. Materials and Methods: An observational longitudinal study was carried out for two months among patients admitted to the pediatric inpatient department using Pediatric Appropriateness Evaluation Protocol (PAEP)-II tool. All patients admitted to the institution during the study period were included in the study. Results: Among 495 children, 438 (88.5%) were appropriately admitted. Inappropriate admission was mostly found in children aged 1 to 5 years (29, 16.6%), those who lived >5 km from the hospital (45, 15.2%), and those who presented with other systemic illnesses (13, 31.7%). Among the appropriately admitted children, 333 (76%) met the criteria of appropriate LOS during their hospital stays. Multivariable logistic regression showed that the age of the children (AOR = 0.99; 95% CI = 0.98, 0.99), age-appropriate feeding (AOR = 2.12;95% CI = 1.30,3.47), and hematological disorder (AOR = 0.16; 95% CI = 0.05, 0.52) were found to be associated with the children being kept at the hospital inappropriately. Conclusions: The current study observed a high proportion of appropriate admission in children. However, a higher proportion of inappropriate LOS among them was seen. The younger age group, age-appropriate feeding, and type of illness were found as the primary predictors for inappropriate LOS. [ABSTRACT FROM AUTHOR]

• Top-bar effect induces a much earlier corrosion initiation but postpones the crack initiation in reinforced concrete. • Top-bar effect changes the pattern of corrosion which can mislead the interpretation of ultrasonic results. • The combined electrochemical and ultrasonic method enables comprehensive evaluation and monitoring of concrete corrosion. • Discerns the patterns of corrosion of reinforced concrete with and without the top-bar effect. Top-bar defect in reinforced concrete (RC) leads to the formation of interfacial voids underneath the reinforcements at an elevation of 300 mm or more. Rebars with top-bar defects show earlier corrosion initiation, faster corrosion rate and a different pattern of corrosion, compared to those without. This paper proposes combined electrochemical and ultrasonic methods for monitoring incipient corrosion in RC. An RC wall structure is cast vertically aiming to create top-bar defect. The specimens were subjected to accelerated chloride-induced corrosion. Simultaneously, they have been monitored with half-cell potential method (HCP), linear polarisation resistance method (LPR), ultrasonic guided waves (GW) and ultrasonic imaging (UI). The pros and cons of the four techniques are determined and discussed. The results are correlated and calibrated with the state of corrosion. Key milestones of the corrosion mechanism such as corrosion initiation and crack initiation can be successfully identified and the progression of bar deterioration, steel-concrete interfacial debonding and cracking propagation have been traced. [ABSTRACT FROM AUTHOR]

Agriculture-sourced, non-point groundwater contamination (e.g., nitrate) is a serious concern from the drinking water crisis aspect across the agrarian world. India is one of the largest consumers of nitrogen fertilizers in South-Asia as well as in the world but groundwater nitrate lacks critical attention as a wide-scale drinking water pollutant in the country. Our study provides the first documentation of the distribution of groundwater nitrate and the extent of elevated nitrate contamination across India, along with the delineation of the temporal trends and the natural and anthropogenic factors that influence such occurrence of groundwater nitrate. High resolution, annual-scale spatio-temporal variability of groundwater nitrate concentration and consequent contamination was delineated using groundwater nitrate measurements from ~3 million drinking water wells spread across 7038 administrative blocks between 2010 and 2017 in India. An average 8% of the studied blocks were found affected by elevated groundwater nitrate (> 45 mg/L). Depth-dependent trend demonstrated that nitrate concentrations were about 14% higher in shallow water wells (≤ 35 m) than deep wells (>35 m). The overall temporal trend of groundwater nitrate concentration was decreasing slightly nationwide in the study period. The correlation tests and causality test results indicated that the spatial distribution of groundwater nitrate was significantly associated with agricultural N-fertilizer usage, whereas the decreasing temporal trend corresponded with the overall reduced N-fertilizer usage during the study period. Spatial autocorrelation analysis identified the clustering of high nitrate areas in central, north, and southern India, specifically in areas with higher fertilizer usage. We estimate about 71 million Indians possibly exposed to elevated groundwater nitrate concentrations and the majority of them reside in rural areas. Thus, this study provides the previously unrecognized, wide-scale, anthropogenic, diffused groundwater nitrate contamination across India. [Display omitted] • Groundwater nitrate pollution is delineated using ~3 million drinking-water wells. • Spatio-temporal trends of groundwater nitrate are analyzed for 2010–2017 in India. • Depth-dependence of groundwater nitrate concentration in the aquifer is delineated. • Rural and urban population exposed to groundwater nitrate pollution is estimated. [ABSTRACT FROM AUTHOR]

Existing studies on automated construction equipment monitoring have focused mainly on activity recognition rather than fault detection. This paper proposes a novel equipment activity recognition and fault detection framework called hybrid unsupervised and supervised machine learning (HUS‐ML). HUS‐ML first identifies normal operations and known faulty conditions through supervised learning. Then, an anomaly detection algorithm is applied to spot any unseen faulty conditions. The framework is tested using acceleration measurements from a low‐rise automated construction system prototype. HUS‐ML outperformed the conventional machine learning approach in activity recognition and fault detection with an average F1 score of 86.6%. The conventional approach failed to detect unseen faulty operations. HUS‐ML identified known faulty operations and unseen faulty operations with F1 scores of 98.11% and 76.19%, respectively. The generalizability of the framework is demonstrated by validating it on an independent benchmark dataset with good results. [ABSTRACT FROM AUTHOR]

[Display omitted] • A selective fluorescence sensing of 1f, 1 h, 1i by ctDNA has been developed. • The thermodynamic parameters revealed the involvement of non-covalent interaction of 1f, 1 h, 1i with ctDNA. • Denaturations, comparative displacement assays, ionic strength, CD also reveal the groove binding nature of the 1f, 1 h, 1i. • The compounds 1f, 1 h, 1i were showed potent anticancer and antimicrobial activity against the cancer cell and model bacteria. The present study aims to elucidate the anti-cancer, antimicrobial activity of synthesized halogenated chalcones (1f, 1h, 1i) and their molecular interaction with calf thymus DNA. All the three compounds were characterized using different spectroscopic tools like FTIR, NMR. DFT and TDDFT computation were performed to support the structural and electronic parameter of the compounds. UV–vis absorbance, steady-state fluorescence, time-resolved fluorescence, circular dichroism, helix melting, molecular docking study reveals that the compounds (1f, 1h, 1i) actively interact with ctDNA via groove binding mode. The binding constants (K b) were calculated to be 1.29 × 104, 0.54 × 104 and 0.45 × 104 M−1 respectively for compounds 1f, 1h, 1i. The compounds were cytotoxic to almost every cell line (PC3, HeLa, A549, HCT116) tested, having minimal toxicity in normal NKE cell line, among which PC3 cells were more sensitive with an IC 50 value of 10 μM. The values were determined using dose response curve and found between 10 and 49 μM for cancer cells and 70 μM for normal cell. Compounds also cause apoptosis in PC3 cells, which was confirmed by Annexin V-FITC/PI assay. Results showed that 1f, 1h, 1i target DNA, to persuade DNA damage mediated cancer cell death. The inhibition zone was formed in the screening test indicating the anti-bacterial activity of 1f, 1h & 1i against model pathogenic bacteria. So the present communication provides quantitative insight of halo-chalcone based anti-cancerous and antimicrobial molecule involving relevant target nucleic acid, which holds future promise in the development of new therapeutic agents. [ABSTRACT FROM AUTHOR]

Background: Various adjuvants are added to local anesthetics to increase the duration of block during supraclavicular brachial plexus (SCBP) block. Dexmedetomidine, a newer and potent alpha2 receptor agonist, has 10 times higher selectivity than clonidine. Many studies have already evaluated the efficacy of clonidine and dexmedetomidine as perineural adjuvants and have reported wide variations in the prolongation of post-operative analgesia. Some studies have reported the absence of adjuvant’s effect while a few have not focused all the facets of block characteristics. Aims and Objectives: The aim of the study was to compare the efficacy of clonidine and dexmedetomidine as adjuvant to ropivacaine during SCBP block for the upper limb surgeries, in terms of duration of post-operative analgesia (Primary outcome). The onset and duration of sensory and motor block, and adverse effects, if any, were observed. Materials and Methods: Ninety patients, aged between 40 and 60 years of either sex, undergoing upper limb surgery, were randomly allocated in to three groups to receive either 30 ml of 0.5% ropivacaine and 2 ml saline (Group R, n=30) or 30 ml 0.5% ropivacaine plus clonidine (1 mcg/kg) plus saline to make a total volume 32 ml (Group C, n=30), or 30 ml 0.5% ropivacaine and dexmedetomidine (1 mcg/kg) plus saline to make a total volume 32 ml (Group D, n=30). The duration of post-operative analgesia, other block characteristics, and adverse events, if any, was assessed. Results: Mean duration of post-operative analgesia was found to be considerably higher in dexmedetomidine group compared with clonidine group and ropivacaine alone group (664.13 vs. 551.77 vs. 465.47, respectively, P<0.001). The duration of sensory and motor block was considerably longer in dexmedetomidine group compared with clonidine and control group. Adverse events were comparable among the three groups. Conclusion: Dexmedetomidine appears to be a better alternative to clonidine as adjuvant in terms of prolonged post-operative analgesia and comparable adverse events. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation (MICP)/Biocementation has emerged as a promising technique for soil engineering applications. There are chiefly two methods by which MICP is applied for field applications including biostimulation and bioaugmentation. Although bioaugmentation strategy using efficient ureolytic biocementing culture of Sporosarcina pasteurii is widely practiced, the impact of native ureolytic microbial communities (NUMC) on CaCO3 mineralisation via S. pasteurii has not been explored. In this paper, we investigated the effect of different concentrations of NUMC on MICP kinetics and biomineral properties in the presence and absence of S. pasteurii. Kinetic analysis showed that the biocementation potential of S. pasteurii is sixfold higher than NUMC and is not significantly impacted even when the concentration of the NUMC is eight times higher. Micrographic results revealed a quick rate of CaCO3 precipitation by S. pasteurii leading to generation of smaller CaCO3 crystals (5–40 µm), while slow rate of CaCO3 precipitation by NUMC led to creation of larger CaCO3 crystals (35–100 µm). Mineralogical results showed the predominance of calcite phase in both sets. The outcome of current study is crucial for tailor-made applications of MICP. [ABSTRACT FROM AUTHOR]

Riverbank erosion is a global problem with significant socio-economic impacts. Microbially induced calcite precipitation (MICP) has recently emerged as a promising technology for improving the mechanical properties of soils. The present study investigates the potential of selectively enriched native calcifying bacterial community and its supplementation into the riverbank soil of the Brahmaputra river for reducing the erodibility of the soil. The ureolytic and calcium carbonate cementation abilities of the enriched cultures were investigated with reference to the standard calcifying culture of Sporosarcina pasteurii (ATCC 11859). 16S rRNA analysis revealed Firmicutes to be the most predominant calcifying class with Sporosarcina pasteurii and Pseudogracilibacillus auburnensis as the prevalent strains. The morphological and mineralogical characterization of carbonate crystals confirmed the calcite precipitation potential of these communities. The erodibility of soil treated with native calcifying communities was examined via needle penetration and lab-scale hydraulic flume test. We found a substantial reduction in soil erosion in the biocemented sample with a calcite content of 7.3% and needle penetration index of 16 N/mm. We report the cementation potential of biostimulated ureolytic cultures for minimum intervention to riparian biodiversity for an environmentally conscious alternative to current erosion mitigation practices. [ABSTRACT FROM AUTHOR]

Riverbank erosion is a global problem with significant socio-economic impacts. Microbially induced calcite precipitation (MICP) has recently emerged as a promising technology for improving the mechanical properties of soils. The present study investigates the potential of selectively enriched native calcifying bacterial community and its supplementation into the riverbank soil of the Brahmaputra river for reducing the erodibility of the soil. The ureolytic and calcium carbonate cementation abilities of the enriched cultures were investigated with reference to the standard calcifying culture of Sporosarcina pasteurii (ATCC 11859). 16S rRNA analysis revealed Firmicutes to be the most predominant calcifying class with Sporosarcina pasteurii and Pseudogracilibacillus auburnensis as the prevalent strains. The morphological and mineralogical characterization of carbonate crystals confirmed the calcite precipitation potential of these communities. The erodibility of soil treated with native calcifying communities was examined via needle penetration and lab-scale hydraulic flume test. We found a substantial reduction in soil erosion in the biocemented sample with a calcite content of 7.3% and needle penetration index of 16 N/mm. We report the cementation potential of biostimulated ureolytic cultures for minimum intervention to riparian biodiversity for an environmentally conscious alternative to current erosion mitigation practices. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation (MICP) process utilising the biogeochemical reactions for low energy cementation has recently emerged as a potential technology for numerous engineering applications. The design and development of an efficient MICP process depends upon several physicochemical and biological variables; amongst which the initial bacterial cell concentration is a major factor. The goal of this study is to assess the impact of initial bacterial cell concentration on ureolysis and carbonate precipitation kinetics along with its influence on the calcium carbonate crystal properties; as all these factors determine the efficacy of this process for specific engineering applications. We have also investigated the role of subsequent cell recharge in calcium carbonate precipitation kinetics for the first time. Experimental results showed that the kinetics of ureolysis and calcium carbonate precipitation are well-fitted by an exponential logistic equation for cell concentrations between optical density range of 0.1 OD to 0.4 OD. This equation is highly applicable for designing the optimal processes for microbially cemented soil stabilization applications using native or augmented bacterial cultures. Multiple recharge kinetics study revealed that the addition of fresh bacterial cells is an essential step to keep the fast rate of precipitation, as desirable in certain applications. Our results of calcium carbonate crystal morphology and mineralogy via scanning electron micrography, energy dispersive X-ray spectroscopy and X-ray diffraction analysis exhibited a notable impact of cell number and extracellular urease concentration on the properties of carbonate crystals. Lower cell numbers led to formation of larger crystals compared to high cell numbers and these crystals transform from vaterite phase to the calcite phase over time. This study has demonstrated the significance of kinetic models for designing large-scale MICP applications. [ABSTRACT FROM AUTHOR]

Bacterial biocementation has been shown to have the unique capability of healing cracks in concrete. However, there is a concern that the materials used in biocement may cause corrosion. This paper reports the performance of bacterially healed reinforced concrete when exposed to chloride-induced reinforcement corrosion. Cracks in reinforced concrete specimens were healed using two different calcium sources. After healing, the samples were subjected to 3.5% sodium chloride exposure to salt water for 120 days. The state of corrosion was assessed through standard electrochemical techniques such as half-cell and linear polarization methods as well as ultrasonic-guided waves. After the exposure period, the bars were extracted from concrete, and mass loss and tensile tests were conducted. It was found that electrochemical measurements indicated corrosion activity in the cracked specimens, but the uncracked specimen did not indicate corrosion during the entire exposure period. The presence of electrolytes in the healing fluid seems to have influenced the electrochemical measurements and gave a misleading indication of corrosion. The ultrasonic-guided waves that assess both effects of corrosion, loss of metal and bar-concrete interfacial debonding, were found to realistically assess the state of corrosion in all the samples. The rate of corrosion had slowed down significantly as a result of healing. [ABSTRACT FROM AUTHOR]

Improving our understanding of groundwater quality threats to human health and the environment is essential to protect and manage groundwater resources effectively. This essay highlights some global groundwater quality challenges, describes key contaminant groups and threats of emerging concern, including antimicrobial resistance, and discusses novel approaches to assessing groundwater quality. Groundwater quality monitoring needs to improve significantly in order to effectively identify and mitigate threats to groundwater from historical, current and future pollution. [ABSTRACT FROM AUTHOR]

Increased frequency of extreme weather events has made the conservation of riverbanks and coastlines a global concern. Soil stabilisation via microbially induced calcite precipitation (MICP) is one of the most eco-suitable candidates for improving resilience against erosion. In this study, the erosion characteristics of soil treated with various levels of biocementation are investigated. The samples were subjected to hydraulic flow in both tangential and perpendicular directions in a flume to simulate riverbank and coastal situations. Soil mass loss, eroded volume, and cumulative erosion rates of the treated soil against the applied hydraulic energy density have been reported. Post erosion exposure, the residual soil has been assessed for its properties using needle penetration resistance, precipitated calcium carbonate content and microstructure. It was observed that soil erosion declined exponentially with the increase in calcium carbonate content against the perpendicular waves. However, biocementation leads to brittle fracture beyond a threshold, limiting its efficacy, especially against the tangential waves. Additional composite treatment with a biopolymer was found to improve the resilience of the soil specimens against erosion. The composite treatment required half of the quantity of the biocementing reagents in comparison to the equally erosion-resistant plain biocemented sample. Therefore, stoichiometrically the composite treatment is likely to yield 50% lesser ammonia than plain biocement treatment. This investigation unravels a promising soil conservation technique via the composite effect of biocement and biopolymer. [ABSTRACT FROM AUTHOR]

• The study provides a comprehensive effort of understanding the role of multiple factors driving seasonal As mobilization in shallow groundwater. • Increasing anoxia and dissolved As concentration is prominent in shallow GSA groundwater during dry pre-monsoon period than in post-monsoon time. • Magnitude of seasonal changes in groundwater As concentrations (Δ As = As PRM – As POM) vary over years due to variable hydrological conditions. • Variable rainfall, excess groundwater withdrawal, mixing, surface water infiltration, and local lithology are marked as probable seasonal redox drivers for As mobilization in shallow aquifer. • Excess withdrawal in pre-monsoon time acts as a conduit for organic-rich surface water infiltration or aquifer intercalated clay-pore water expulsion by compaction and mixing in the adjoining groundwater; promotes high As release. Arsenic (As) mobilization in groundwater is linked to the dissimilatory reductive dissolution of As(V) coated Fe(III)-oxy-hydroxides from the aquifer sediment coupled with the degradation of available dissolved organic carbon (DOC) due to the presence of anaerobic microbes under anoxic conditions. Understanding the seasonal pattern of As mobilization in the shallow groundwater of the Bengal Basin remains a challenging task due to the heterogeneous character of the shallow aquifers and the involvement of multiple factors. To resolve this issue, in the present study, we showcased a comprehensive effort to advance understanding of the seasonal As mobilization process in the shallow groundwater, utilizing multiple geochemical tracers (i.e., the abundance of dissolved total As, Fe, Mn, NO 3 –, SO 4 2-, DOC, Cl-, and δ18O, δ2H, δ13C-DOC isotopic tracers) between post-monsoon and pre-monsoon periods over multiple years from Nadia district, West Bengal, India. We quantified and explained the seasonal variation of dissolved total As concentrations in the groundwaters with the nature of the aquifer lithology (i.e., grey sand aquifer or 'GSA' and brown sand aquifer or 'BSA'). The present study reported elevated dissolved total As concentrations in the shallow groundwater samples during dry pre-monsoon ('PRM') periods compared to post-monsoon ('POM') time. However, the magnitude of such seasonal changes in groundwater As concentrations (denoted as Δ As = As PRM -As POM) varied between years depending on the extent of rainfall, surface water infiltration, mixing, and groundwater withdrawal. Our current findings are different from the past studies that reported elevated As concentrations in the shallow groundwater during the monsoon and post-monsoon periods compared to the dry pre-monsoon periods. However, the limitations of the past findings are that most of the previous studies were carried out between seasonal intervals over a single annual cycle without reinvestigating the seasonal trends over different years under variable hydrological conditions. We proposed that the excess groundwater withdrawal during the dry pre-monsoon period drive draw-down and, therefore, trigger infiltration of surface-derived deep pond water into the shallow aquifer. Such surface water infiltration introduces fresh labile organic matter into the shallow aquifer, promoting high As mobilization during the dry pre-monsoon period. A viable alternative approach of 'squeezing' of aquifer intercalated clay-peat sedimentary lenses and mixing of organic-rich pore water in the adjoining groundwater can also enhance high As mobilization during the dry time, as examined in this study. This process is triggered by the excessive groundwater withdrawal practices and drawdown encountered during dry time, driving the aquifer intercalated clay-pockets compaction. [ABSTRACT FROM AUTHOR]

• The study provides a comprehensive effort of understanding the role of multiple factors driving seasonal As mobilization in shallow groundwater. • Increasing anoxia and dissolved As concentration is prominent in shallow GSA groundwater during dry pre-monsoon period than in post-monsoon time. • Magnitude of seasonal changes in groundwater As concentrations (Δ As = As PRM – As POM) vary over years due to variable hydrological conditions. • Variable rainfall, excess groundwater withdrawal, mixing, surface water infiltration, and local lithology are marked as probable seasonal redox drivers for As mobilization in shallow aquifer. • Excess withdrawal in pre-monsoon time acts as a conduit for organic-rich surface water infiltration or aquifer intercalated clay-pore water expulsion by compaction and mixing in the adjoining groundwater; promotes high As release. Arsenic (As) mobilization in groundwater is linked to the dissimilatory reductive dissolution of As(V) coated Fe(III)-oxy-hydroxides from the aquifer sediment coupled with the degradation of available dissolved organic carbon (DOC) due to the presence of anaerobic microbes under anoxic conditions. Understanding the seasonal pattern of As mobilization in the shallow groundwater of the Bengal Basin remains a challenging task due to the heterogeneous character of the shallow aquifers and the involvement of multiple factors. To resolve this issue, in the present study, we showcased a comprehensive effort to advance understanding of the seasonal As mobilization process in the shallow groundwater, utilizing multiple geochemical tracers (i.e., the abundance of dissolved total As, Fe, Mn, NO 3 –, SO 4 2-, DOC, Cl-, and δ18O, δ2H, δ13C-DOC isotopic tracers) between post-monsoon and pre-monsoon periods over multiple years from Nadia district, West Bengal, India. We quantified and explained the seasonal variation of dissolved total As concentrations in the groundwaters with the nature of the aquifer lithology (i.e., grey sand aquifer or 'GSA' and brown sand aquifer or 'BSA'). The present study reported elevated dissolved total As concentrations in the shallow groundwater samples during dry pre-monsoon ('PRM') periods compared to post-monsoon ('POM') time. However, the magnitude of such seasonal changes in groundwater As concentrations (denoted as Δ As = As PRM -As POM) varied between years depending on the extent of rainfall, surface water infiltration, mixing, and groundwater withdrawal. Our current findings are different from the past studies that reported elevated As concentrations in the shallow groundwater during the monsoon and post-monsoon periods compared to the dry pre-monsoon periods. However, the limitations of the past findings are that most of the previous studies were carried out between seasonal intervals over a single annual cycle without reinvestigating the seasonal trends over different years under variable hydrological conditions. We proposed that the excess groundwater withdrawal during the dry pre-monsoon period drive draw-down and, therefore, trigger infiltration of surface-derived deep pond water into the shallow aquifer. Such surface water infiltration introduces fresh labile organic matter into the shallow aquifer, promoting high As mobilization during the dry pre-monsoon period. A viable alternative approach of 'squeezing' of aquifer intercalated clay-peat sedimentary lenses and mixing of organic-rich pore water in the adjoining groundwater can also enhance high As mobilization during the dry time, as examined in this study. This process is triggered by the excessive groundwater withdrawal practices and drawdown encountered during dry time, driving the aquifer intercalated clay-pockets compaction. [ABSTRACT FROM AUTHOR]

Non-destructive evaluation using ultrasonic pulse velocity (Vp) testing has extensive applications in the concrete industry. With advances in construction technology, the use of ground granulated blast furnace slag (GGBFS) as a partial replacement to cement in a concrete mix is growing in popularity primarily because it reduces the initial capital cost of raw materials and the associated energy costs. This paper investigates the effect of the water-to-cement (wc) ratio and the cement content replaced by GGBFS on the development with time of the ultimate compressive strength ( f c ′ ) and the compression wave velocity (Vp) of mortar. The results showed that in the case of mortar with higher percentages of GGBFS replacement (where nucleation surfaces are more abundant), increasing wc can increase f c ′ but cause a decrease in Vp. The posterior hydration process is highly dependent upon the water particles in the mixture after the first stage of hydration. After 7 days of curing, experimental results show that the f c ′ of slag blended cement mix design wc ratio of 0.6 surpassed the f c ′ value of an Ordinary Portland cement. A regression model correlating the f c ′ and Vp of slag blended mortar is developed, which can be used to predict f c ′ at concrete ages ranging from 1 day to 28 days for mixes with GGBFS percentage replacement values ranging from 15% to 45%. [ABSTRACT FROM AUTHOR]

This article discusses the development of smart soil nails that can monitor the condition of grout in real-time. Grouted soil nails are commonly used for stabilizing soil slopes and tunnel linings, but they are susceptible to pullout failure due to grout deterioration. The smart nails use ultrasonic wave packets to inspect the grout surrounding them and offer insights into the structural integrity of the soil nails. The article suggests that these smart nails have the potential to be used in various geotechnical engineering applications, but further experiments are needed to correlate the pullout capacity with the deterioration index. [Extracted from the article]

• 3D printable cementitious composite with enhanced sensing capability was developed. • The 3D printed cementitious composites exhibited distinct mechanical anisotropy. • 3DP can orientate the fibre and contribute to the conductive path formation. • Fibre alignment improves the linearity and repeatability of the piezoresistivity. This paper explores the potential of fabricating self-sensing cementitious composites using the 3D printing technology. In this study, carbon fibre (CF) and activated carbon powder (ACP) were studied at various concentrations as functional fillers. An extrusion-based 3D printer was used for 3D printed samples preparation and the mould cast samples were fabricated as a direct comparison. The mechanical properties, electrical resistivity and piezoresistive performance in two directions were measured. The results indicate that 3D printing technology can achieve fibre alignment within the printed filament and, consequently, result in anisotropic behaviour of the 3D printed composites. The optimal mechanical strength with compressive strength of 74.9 MPa and flexural strength of 16.4 MPa were achieved by 3D printed composite with hybrid CF at 0.7 wt% and ACP at 0.25 wt%. The optimal 3D printed composite shows an excellent piezoresistive response with improved linearity, repeatability and signal quality when the loading direction is perpendicular to the printing direction, demonstrating a strong fit with the predicted equation. On the microstructural level, scanning electron microscopy images indicated the fibre alignment and enhanced fibre–matrix bonding of 3D printed composites. [ABSTRACT FROM AUTHOR]

Introduction: Exposure to high levels of noise is a problem among tea factory workers worldwide, but it is poorly studied in India. Aims: This study aimed to assess noise generation in various parts of a black tea factory and find out prevalence of occupational noise-induced hearing loss (ONIHL) and its determinants among employees. Materials and Methods: An observational cross-sectional study was performed in a black tea processing factory of Darjeeling District. Noise levels and exposure data at different parts of the factory were measured using a sound level meter. Participant characteristics were obtained using a questionnaire and noise-induced hearing loss data obtained by audiometry. A sound map was generated based on noise exposure data and a multivariable logistic regression performed to assess determinants of ONIHL. Results: Sound pressure levels ranged from 58.7 to 90.3 dBA, with the highest levels in the crushing--tearing--curling (CTC) room. Noise exposure of workers was the highest during curling process and the lowest during packaging in the packing room. The prevalence of ONIHL was found to be 28.3%, most of which were of moderate degree, and the highest prevalence was among CTC room workers. Multivariable analysis showed significant association only between daily noise exposure and the presence of ONIHL (AOR 1.68, P value = 0.018). None of the study participants used any hearing protection equipment during work. Conclusions: Generation of high levels of noise is a pertinent problem in the black tea factory, which, coupled with non-use of personal protective equipment, led to a high risk and prevalence of ONIHL. [ABSTRACT FROM AUTHOR]

Summary: Deep terrestrial subsurface represents a huge repository of global prokaryotic biomass. Given its vastness and importance, microbial life within the deep subsurface continental crust remains under‐represented in global studies. We characterize the microbial communities of deep, extreme and oligotrophic realm hosted by crystalline Archaean granitic rocks underneath the Deccan Traps, through sampling via 3000 m deep scientific borehole at Koyna, India through metagenomics, amplicon sequencing and cultivation‐based analyses. Gene sequences 16S rRNA (7.37 × 106) show considerable bacterial diversity and the existence of a core microbiome (5724 operational taxonomic units conserved out of a total 118,064 OTUs) across the depths. Relative abundance of different taxa of core microbiome varies with depth in response to prevailing lithology and geochemistry. Co‐occurrence network analysis and cultivation attempt to elucidate close interactions among autotrophic and organotrophic bacteria. Shotgun metagenomics reveals a major role of autotrophic carbon fixation via the Wood–Ljungdahl pathway and genes responsible for energy and carbon metabolism. Deeper analysis suggests the existence of an 'acetate switch', coordinating biosynthesis and cellular homeostasis. We conclude that the microbial life in the nutrient‐ and energy‐limited deep granitic crust is constrained by the depth and managed by a few core members via a close interplay between autotrophy and organotrophy. [ABSTRACT FROM AUTHOR]

Introduction: Despite efforts to motivate all reproductive age women to avail cervical cancer screening services, many still do not utilise them. Most researchers have universally identified barriers like the lack of knowledge and lack of accessibility as the reason for not availing services. However, additional barriers also prevent women from making use of these screening services. Aim: To explore the barriers to and facilitating factors for cervical cancer screening beyond the lack of knowledge and accessibility of services. Materials and Methods: This qualitative research was conducted among tribal women residing in the Kiranchandra Tea Estate and Atal Tea Estate (two tea gardens in the rural Naxalbari Block) West Bengal, India, from July 2018 to February 2019. Women aged 30-59 years, living in the garden for at least the last 5 years, not suffering from obstetrics/gynaecological disease during last two years and willing to participate in the study were included, based on a purposive sampling method. Information Education Campaign (IEC) on cervical cancer and screening were undertaken and screening services arranged in the gardens on garden holidays for two consecutive weeks. Four (4) Focus Group Discussion (FGDs) in each garden were conducted, with each FGD consisting of 5 to 6 participants (N=49). Data obtained was recorded and logged with the participants' permission and consent. A manifest content analysis was used to explore the perceived barriers and facilitators of cervical screening. Results: The major barriers identified were lack of support, burden of responsibility and the lack of felt need. The facilitators found most frequently were provision of information, social motivation, easy accessibility and affordability of screening services. Conclusion: This study revealed that there are various actual and perceived barriers to cervical cancer screening among tribal women in tea garden areas. Even after imparting knowledge and increasing availably and accessibility of a free program, familial support, burden of responsibility and lack of felt needs hinder increased uptake of the services. [ABSTRACT FROM AUTHOR]

The groundwater within the aquifers of the Ganges River delta exhibits significant spatial variability in concentrations of redox-sensitive solutes [e.g., arsenic (As), iron (Fe), manganese (Mn)]. The groundwater As and Mn concentrations show conspicuous contrasting distribution on the opposite banks of the Bhagirathi-Hooghly (B-H) River, the Indian distributary of the Ganges River. Here, we investigate the differences in hydrostratigraphic framework and groundwater evolutionary pathways across the B-H River that might have resulted in such variations. We developed a hydrostratigraphic model for the region and also used inverse reaction-path modeling along three hypothesized end-member flow paths to understand the dominant processes that might control As and Mn cycling within the aquifers. Our results indicate that the variability of As and Mn across the B-H River is a function of a complex interplay between the aquifer architecture, groundwater chemistry, and redox conditions. • Heterogeneity of groundwater arsenic incites the processes involved in the contaminant mobilization. • Contrasting groundwater As and Mn concentrations on opposite banks of Ganges river, India. • Geology and hydrogeology influence contrasting arsenic concentrations. • Inverse flow path modeling delineates the water-sediment interactions. [ABSTRACT FROM AUTHOR]

• Ocean wave surge effects on groundwater levels during tides and storms. • Delineation shallow and deeper aquifers sourced drinking water vulnerability due to wave surge. • Quantification of groundwater response to wave during extreme climate condition. Groundwater level (GWL) of coastal aquifers are strongly influenced by the ocean tide at sub-daily to seasonal scale. Similarly, GWL are influenced by storm induced ocean wave surge lasting few hours to a day. There has not been a detailed study on the conjunctive impact of such tidal and storm waves on coastal groundwater and its vulnerability. Through our coastal and field-laboratory observations at one of the world's most extreme climate affected regions, the Ganges river mega-delta, we delineate the influence of ocean wave surge impacts on the shallow (<24 m below ground level [m bgl]) and deep (115 m bgl) aquifers GWL. Our study on the multi-layered delta-front aquifers, adjoining the tropical BoB shows that the high-temporal resolution GWL fluctuation due to wave surges are instantaneous, rapid and synchronous at all depths of the aquifers. The potential rise of ocean waves caused by tropical cyclone Bulbul (November 2019) significantly increases the GWL, both in shallow and deeper aquifer. Using multivariate statistics and machine learning techniques, we have attempted to quantify the rise of GWL during each of the ocean wave surge event. The model shows good predictability for deeper groundwater, however it is unable to quantify the shallower GWL of each of the ocean wave surge during storm events. Such phenomenon indicates aquifer vulnerability, thereby posing an emerging threat to drinking water availability to millions of groundwater-dependent inhabitants in coastal areas, globally, which may rapidly intensify with increasing rates of tropical cyclones and sea level rise in recent times and impending future. [ABSTRACT FROM AUTHOR]

• Strengthening of RCA via cement slurry and biocement treatment was performed. • Both the control and treated aggregates are characterised for its possible use. • A novel method of fabricating concrete cubes with one aggregate has been developed. • Micromechanical property using nanoindentation was assessed at concrete interface. • RCA can be used to replace the NCA without compromising its performance. Variable quality of recycled aggregates especially attached mortars leading to weak interfaces is a primary drawback of recycled coarse aggregate (RCA). This investigation explores strengthening of such aggregates by biocement treatment and compares it with the conventional cement slurry treatment. The effect of the treatments on the aggregates has been recorded in terms of water absorption and mechanical properties. To study the concrete-aggregate interface, a novel method of fabricating concrete cubes with one aggregate has been developed. Damage evolution at the interfaces has been recorded with advanced monitoring techniques. Microstructural behaviour and elemental composition in the interface were also recorded. The test results show that the biocement treatment reduces the water absorption of RCA by about 71%. A microstructural study demonstrates that biocement, due to its considerably low viscosity, is able to penetrate the porous interfacial mortar within RCA and densify it. The micromechanical properties using nanoindentation provides more insights in improving of interfacial transition zones. The treatment improves the aggregates to a level that it can be used to replace the natural aggregates without compromising its performance. [ABSTRACT FROM AUTHOR]

• Mechanical & microstructural properties of GFNS incorporated HSSCC are examined as a function of temperature. • SEM, XRD, UPV, and TGA tests were performed to examine the residual behaviour. • Specimens undergo continuous mass reduction with temperature rise. • HSSCC incorporating GFNS shows higher residual compressive strength up to 400 °C in comparison to control specimen. • Cracks and changes in microstructures occurred as a result of high temperatures. Fire safety is a vital parameter for any structure as fire can accidentally occur at any time. This study presents the experimental results on residual strength and deterioration behaviour after high-temperature exposure of high-strength self-compacting concrete (HSSCC) produced using ferronickel slag (FNS). Four HSSCC mixtures were studied using up to 50 % ground FNS (GFNS) as cement replacement and 40 % raw FNS as sand replacement. Cylinder specimens were exposed to 200, 400, and 600 °C for two hours in a furnace. Cracking, change of colour, mass loss, residual compressive strength, thermogravimetric analysis, and ultrasonic behaviour of the specimens were studied. Morphological changes were examined by scanning electron microscopy (SEM), and phase detection was carried out by X-ray diffraction (XRD). The highest mass loss of 8 % was observed in the specimens containing 50 % GFNS, at 600 °C. At 400 °C, compressive strength decreased by about 45 % for the control mixture. In contrast, strength loss for the mixtures containing 20–50 % GFNS was in the range of 17–27 %. However, at 600 °C, compressive strength for all the mixes reduced drastically, by more than 50 %. This is considered to be mainly due to the occurrence of cracks, which was evidenced by the increased travel time of the ultrasonic waves through the specimens. Network of fine cracks were also observed on the surface of all the specimens. The SEM images and XRD results showed the distinct morphological changes at different temperatures for different mixes that correlated with the compressive strength results. Thus, the use of raw and ground FNS offers a wide and viable window of opportunity in production of HSSCC with resistance against high temperature exposure. [ABSTRACT FROM AUTHOR]

Microbial cement production based on microbially induced calcium carbonate precipitation (MICP) is a technology with high potential but is economically limited. Lower medium costs are expected to improve the economic attractiveness of microbial cement production. We report the effect of an important medium parameter, the carbon-to-nitrogen (C/N) ratio (2, 5, 10, 15, and 20) on the intracellular urease activity (IUA) of ureolytic bacteria, Sporosarcina pasteurii (ATCC 11859) through experiments and analysis of a relevant genome-scale metabolic model (GSMM). A positive correlation was observed between IUA and C/N ratio until an optimal C/N ratio of 15. At a C/N ratio of 15, the IUA was 29.5 U/(g dry-cell-weight). Further, the ammonium (nitrogen waste) generation decreased by 7.7-fold at the optimal C/N ratio of 15 compared to that at 2, which is environmentally significant. Despite the decrease in initial urea concentration with an increasing C/N ratio, no decline in the biomass was observed, which is advantageous. Analysis of the GSMM provided the insights that the optimal C/N ratio of 15 also ensures an efficient bio-mineralization process and that increasing the ratio beyond 15 may negatively impact bio-mineralization. The results will be of significance while selecting a low-cost medium for field-scale MICP applications. [Display omitted] • Specific intracellular urease activity (IUA) of Sporosarcina pasteurii increased with C/N ratio. • The optimal C/N ratio (C/N) for IUA was 15. • The optimal urea concentration for IUA was 16.66 mM. • Ammonium ion generation rate at optimal C/N = 15 was 7.7–fold lower than at C/N = 2. • Insight from genome scale metabolic model: C/N above 15 hinders biomineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface water-groundwater interaction determines discharge from a coastal aquifer. • Geophysical signatures indicate hydraulic connectivity across vertical depths. • Seasonal control on the movement of the fresh water/saline water wedge. • Groundwater abstraction may lead to salinization via vertical solute transport. The groundwater of the coastal aquifers, the primary source of drinking water for the community around it, is under stress due to changing climatic conditions, extreme climate events, over-exploitation, and natural/anthropogenic interferences. To sustain coastal groundwater, it is essential to understand the hydrogeological control on the distribution of salinity and submarine groundwater discharge (SGD) in various spatial and temporal scales at different depths. This study is focused to delineate the SGD and salinity distribution for shallow surficial and deep aquifers by application of the hydrogeochemical and geophysical approach in an intertidal zone. The resistivity [Electrical Resistivity Tomography (ERT), Vertical Electrical Sounding (VES)] and Ground Penetrating Radar (GPR) data show surficial aquifers have (up to 1.5 m below ground level (m bgl)) have higher freshwater discharge at the post-monsoon season and recirculation of infiltrated brackish water with increasing offshore distances. The re-circulated seawater in distant offshore was also predominant for intermediate (>1.5 up to 100 m bgl) (brackish water-saturated) and deeper depths (>100 m bgl) (fresh groundwater), which is observed from the distinct resistivity contrasts from VES. The interaction process for all the depths with seawater has been induced by the coastal hydrodynamics, meteoric recharge, and fluctuation of groundwater levels. However, variations of resistivity and sounding data delineate that the groundwater resources underneath the shallow depth brackish water are physically vertically disconnected from the surficial aquifer, but spatial variation in sounding data shows the hydraulic connectivity, which would lead to a serious concern for fresh groundwater resources, where density-dependent transportation of solute is plausible, both vertically and horizontally. [ABSTRACT FROM AUTHOR]

The present study dealt with understanding hydrogeochemical evolution, ascertaining distribution, fate and spatio-temporal variation of arsenic along with comprehending recharge processes and quantification of recharge rate in the central Gangetic plain, India. The arsenic enriched area was observed mostly in the fluvial deposits with younger alluvium. The depth to water levels maps for 1996 and 2016 showed marked spatio-temporal variation and the groundwater recharge rate was estimated to be varied between 0.05 m/year and 0.07 m/year in the study area. The elevated arsenic concentration was noticed in the region, having declined groundwater recharge. A total of 147 water samples were collected from hand pumps (n = 141) and rivers (n = 6) during the pre-monsoon period (May 2016). In addition, about 81 groundwater samples were collected from 27 locations during the pre-monsoon, monsoon and winter 2019 for studying seasonal variability in the hydrogeochemical parameters and isotopic composition of water. Arsenic concentration was found more in the area where deposits of coarser sediment of the Quaternary period was present along the rivers Ganga and Ghaghra. The arsenic concentration was observed higher in the pre-monsoon (maxm. As 641 μg/L), followed by the post-monsoon (425 μg/L) and monsoon season (375 μg/L). The depleted isotopic value and higher D-excess values in groundwater suggested active recharge conditions with precipitation as the major source of recharge in the study area. It is hypothesized that rainwater induced oxygenated water into the aquifer by the process of recharge, which may prompted various biogeochemical reactions due to change in redox conditions and endorsed arsenic sorption in the monsoon season. Thereafter, anoxic conditions prevailed in the post-monsoon season, and finally, in the pre-monsoon season, reducing conditions continued and arsenic released at a rapid rate, which was justified with the seasonal variation of arsenic concentration. [Display omitted] • Depth to water level maps show marked spatio-temporal variation in the study area from year 1996–2016. • GW decline at rate of 0.07 m/yr in the SE region of the study area where elevated arsenic concentration is noticed. • Based on ORP values, reducing conditions exist in the pre-monsoon season and arsenic release at a rapid rate. • Depleted δ18O and higher D-excess values suggest active recharge conditions, and precipitation is the major source. [ABSTRACT FROM AUTHOR]