Microplastics and Aquatic Limnology: Conception of Biogeochemical Processes
Dash S., Kumar M., Mazumder P.
Book chapter, Occurrence, Detection, and Fate of Microplastics in Freshwater Ecosystems, 2025, DOI Link
View abstract ⏷
Microplastics (MPs) are emerging as contaminants posing serious environmental threats. Various types of MPs are being discharged into our water bodies, affecting the natural biogeochemical processes in the aquatic ecosystem, including modifications in carbon and nutrient cycling and imparting severe toxicity to flora and fauna. While several pieces of literature are available on the sources and types of MPs being discharged into various global water bodies, deep insights into the various biogeochemical processes affecting the environmental cycle still remain nascent. The present review highlights the key research avenues elucidating the governing mechanisms for changes in the biogeochemical cycle due to microplastic pollution. This includes different studies carried out on the impacts of MPs on the various environmental (carbon, nitrogen and phosphorus) cycles of the aquatic ecosystems. It also presents the toxicity aspects of MPs on the aquatic flora and fauna in different environments. Finally, we discuss the prospects that researchers need to focus on to provide a more comprehensive picture of the biogeochemical processes involved in MP pollution and to achieve sustainable solutions to abate MP contamination.
Microbial drivers of biogeochemical cycles in deep sediments of the Kathiawar Peninsula Gulfs of India
Mootapally C., Sharma P., Dash S., Kumar M., Sharma S., Kothari R., Nathani N.
Article, Science of the Total Environment, 2025, DOI Link
View abstract ⏷
Deep marine sediments are rich in microbial diversity, which holds metabolic repertoire to modulate biogeochemical cycles on a global scale. We undertook the environmental microbiome inhabiting the Gulf of Kathiawar Peninsula as a model system to understand the potential involvement of the deep marine sediment microbial community and as a cohort in the carbon, nitrogen, and sulfur biogeochemical cycles. These gulfs are characterized by dynamic tidal variations, diverse sediment textures, and nutrient-rich waters, driven by coastal processes and the interaction between natural coastal dynamics and anthropogenic inputs that shape its microbial community diversity. Our findings suggest that carbon fixation was carried out by Gamma-proteobacteria with CBB cycle-related genes or by microbial participants with Wood-Ljungdahl pathway-related genes. Microbial communities involved in nitrogen metabolism were observed to be rich and diverse, and most microbial communities potentially contribute to the nitrogen cycle via processing nitrogen oxides. Bacteria belonging to the KSB1 phylum were also found to fix nitrogen. The sulfur cycle was spread throughout, with Verrucomicrobiota phylum being a major contributor. The varying napAB genes, significantly lower in the Gulf of Kutch compared to the Gulf of Cambay and the Arabian Sea, mediated nitrate reduction. Dynamics between these pathways were mutually exclusive, and organic carbon oxidation was widespread across the microbial community. Finally, the proteobacteria phylum was highly versatile and conceivably contributed to biogeochemical flux with exceptionally high abundance and the ability to form metabolic networks to survive. The work highlights the importance of critical zones and microbial diversity therein, which needs further exploration.
Balancing Safety and Sustainability: Sustainable Approaches to Reducing Disinfection By-Products in Drinking Water
Koley S., Dash S., Khwairakpam M., Kalamdhad A.S.
Book chapter, ACS Symposium Series, 2025, DOI Link
View abstract ⏷
Conventional disinfection methods for drinking water are imperative in removing harmful pathogens. Then again, they often inadvertently give rise to disinfection by-products (DBPs) that are inherently carcinogenic, posing substantial health risks. Hence, exploring innovative and sustainable solutions to counter the side effects of these classical disinfection techniques is inevitable. This chapter thoroughly investigates the global challenges associated with DBPs in treated drinking water and provides a detailed overview of their prevalence globally. Emphasis has been placed on the prevalence and regulatory frameworks of trihalomethanes (THMs), the most predominant DBP species. Additionally, the chapter delves into examining different sustainable water management strategies aimed at reducing the formation of DBPs in treated drinking water, including source water protection, optimum use of disinfectants, and the implementation of advanced treatment technologies. Special attention is given to reducing THMs and their precursors, highlighting the effectiveness of membrane filtration, green adsorbents, and advanced oxidation processes (AOPs). The importance of integrating these strategies with robust monitoring systems and proactive policy measures to safeguard public health in the long term is also highlighted. Additionally, the chapter underscores the need for continuous research and development of innovative DBP control methods while advocating for a holistic and sustainable approach to drinking water management. Ultimately, this chapter aims to contribute to the ongoing dialogue on protecting public health and ensuring long-term water security by emphasizing sustainable DBP minimization strategies.
Green revolution to clinical burden: Connecting the dots between pesticide consumption and cancer incidents in India
Dash S., Gupta P., Kumar M.
Review, Current Opinion in Environmental Science and Health, 2025, DOI Link
View abstract ⏷
Pesticide poisoning through contaminated water, soil, or food is often linked to the widespread use of chemical pesticides in Indian agriculture. While many studies have reported the association between pesticide exposure and human health impacts, it has been challenging to disseminate this information to a broader population at state and national levels. Consequently, no state-level database exists correlating pesticide use with cancer rates in India. Here, we provide a comprehensive outlook focusing on the challenges of correlating these factors to develop a comprehensive geospatial database at the national level. A data-mining approach can help identify cancer hotspots, supporting informed policymaking.
Understanding the pathways, pollution and potential solutions pertaining to pesticides: Circular engineering for persistent chemicals
Kumar M., Dash S., Mahlknecht J., Kolok A., Dogra S., Kuroda K., Tobino T., Mora A., Kazmi A.A., Singh R., Mutiyar P.K., Dash R.R., Kurisu F.
Review, Current Opinion in Environmental Science and Health, 2025, DOI Link
View abstract ⏷
This paper offers a comprehensive examination of the global footprint of pesticides consumption, revealing the disproportionate usage in high-income countries and highlighting the severe environmental and health risks posed by chemicals such as organochlorines and organophosphates. While numerous studies have been conducted on assessing the fate and transport of pesticides in the natural environment in developed nations, however, there is pressing need for similar research in developing regions, within South-East Asia, Latin America, and the African Union. Due to the cumulative nature of pesticides and the duration of exposure, it was expected that biota would show higher average, minimum, and maximum concentrations, along with increased variability. Water appears to be slightly more contaminated than sediment, but the most concerning revelation is the prevalence of pesticides in the air. Emphasizing the urgency of sustainable practices, the paper proposes microcosmic understanding on the degradation of pesticides, their contribution to antimicrobial resistance, and the development of environmentally friendly alternatives.
Unlocking sustainability: Integrating omics for advanced wastewater treatment
Kumar M., Dogra S., Das N., Dash S., Sharma A., Jimenez A.K.R., Diaz-Lara A., Snyder S.A., Kurisu F.
Review, Journal of Environmental Chemical Engineering, 2025, DOI Link
View abstract ⏷
Owing to the urgent and escalating environmental crisis of water pollution through anthropogenic wastewater generated from various sources, the development of novel and innovative bioremediation strategies that are equally sustainable is highly necessitated. The present study embarks on an integrated omics-based exploration, complemented by a thorough literature synthesis, to critically evaluate and enhance hybrid algal-bacterial systems for effective wastewater treatment. Drawing on case studies and research from diverse geographic regions, we explore how these technologies inform the design and optimization of both engineered and natural treatment systems. The review emphasizes the integration of multi-omics data to support sustainable, targeted bioremediation strategies and underscores the cross-disciplinary convergence of environmental engineering, molecular biology, and systems ecology. This global and holistic perspective positions omics as a cornerstone for advancing the next generation of wastewater treatment solutions. Comprehensive analyses of the efficacies of different treatment methods used to remediate organic pollutants, heavy metals, nutrients, and contaminants of emerging concern (CECs), including antibiotic resistance genes (ARGs), were carried out, thus underscoring the pivotal role of microbial diversity and metabolic activity in the complex process of contaminant elimination. While prior research has predominantly focused on isolated components, the current study presents a holistic approach, merging state-of-the-art high-throughput metagenomics and transcriptomics techniques. This innovative combination illuminates the functional dynamics of microbial communities operating within the hybrid system under a range of operational conditions. The primary critical findings reveal significant shifts in microbial community structure and gene expression patterns, which are intricately linked to enhanced efficiencies in nutrient uptake and contaminant removal. In addition, the study also situates these findings within the expansive framework of omics-based bioremediation research, providing a clear and structured pathway for identifying prevailing knowledge gaps and directing future optimization efforts. Collectively, these contributions not only deepen our understanding of microbial community functions but also pave the way for designing next-generation bio-based wastewater treatment systems driven by the intricate interplay of microbial dynamics.
Spatio-temporal variation in the water cycle: Case studies of different geographical locations
Book chapter, Water Sustainability and Hydrological Extremes: Quantity, Quality, and Security, 2024, DOI Link
View abstract ⏷
Understanding the global water flux is vital to comprehend different hydrological components of the planet. The precise quantification of the global water budget is important to understand the global water cycle. While the first attempts in closing the global water budget date back to the early 1900s, we still have not been able to comprehensively understand the global water cycle. The past few decades have witnessed significant interests among the researchers worldwide in understanding the global water budget considering various ecological, hydrological, and climatic parameters and using data from various sources, such as ground observations or satellite information. However, a certain degree of uncertainty still prevails in the global or regional models developed till date. Here, we discuss some recent advances in this context, taking into account continent-wise analyses of the various significant attempts made by different researchers in varying geographical conditions, and using different tools. These findings will eventually lead to deeper understanding and advancements in the existing approaches aiding in the closure of the global water budget.
Influence of Fly Ash Leachate on the Hydraulic and Mechanical Behavior of Bentonites
Ray S., Dash S., Jana A., Mishra A.K., Kalamdhad A.S.
Conference paper, Geotechnical Special Publication, 2024, DOI Link
View abstract ⏷
The present study aims to investigate the influence of fly ash leachate (FL) on the hydraulic and mechanical behaviour of two Indian bentonites with discrete mineralogical and chemical compositions. The investigation revealed that both bentonites with different mineralogical and physical properties noticeably affected free swelling, Atterberg limits, swelling potential, swelling pressure, and hydraulic conductivity. However, a comparative assessment for both types of bentonites shows that swelling capability, liquid limit, cation exchange capacity, and the specific surface area experience a directly proportionate variation to the free swell (80% decline), liquid limit (74% decline), swelling potential (61% decline), and swelling pressure (59% decline) when permeated with FL. In addition, a rise in hydraulic conductivity (28 and 38 times rise at a void ratio of 1.1) was observed with leachate presence for both bentonites. The research findings would therefore prove constructive to engineers for deciding on bentonite types for liner application in landfills.
Perspectives and understanding on the occurrence, toxicity and abatement technologies of disinfection by-products in drinking water
Koley S., Dash S., Khwairakpam M., Kalamdhad A.S.
Review, Journal of Environmental Management, 2024, DOI Link
View abstract ⏷
Disinfection by-products (DBPs) are one of the significant emerging contaminants that have caught the attention of researchers worldwide due to their pervasiveness. Their presence in drinking water, even in shallow concentrations (in levels of parts per billion), poses considerable health risks. Therefore, it is crucial to understand their kinetics to understand better their formation and persistence in the water supply systems. This manuscript demonstrates different aspects of research carried out on DBPs in the past. A systematic approach was adopted for the bibliographical research that started with choosing appropriate keywords and identifying the most relevant manuscripts through the screening process. This follows a quantitative assessment of the extracted literature sample, which included the most productive and influential journal sources, the most widely used keywords, the most influential authors active in the research domain, the most cited articles, and the countries most actively engaged in the research field. Critical observations on the literature sample led to the qualitative assessment, wherein the past and current research trends were observed and reported. Finally, we identified the essential gaps in the available literature, which further led to recommending the course ahead in the research domain. This study will prove fruitful for young and established researchers who are or wish to work in this emerging field of research.
Long-Range Transport of Polycyclic Aromatic Hydrocarbons and Metals in High Altitude Lacustrine Environments of the Eastern Himalayas: Speciation, and Source Apportionment Perspectives
Deka J.P., Dash S., Sandil S., Chaminda T., Mahlknecht J., Kumar M.
Article, ACS ES and T Water, 2024, DOI Link
View abstract ⏷
We quantified polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in the sediments and aerosols of the Eastern Himalayan Lakes, collected over four years from three high altitude Lakes (HALs), i.e., Sungester Lake, P.T. Tso Lake, and Sela Lake. The focus was to carry out source apportionment using multivariate statistical analyses. PAH concentrations (∑PAHs) in the core sediment during the pre-monsoon were higher than the post-monsoon, suggesting an elevated sedimentation rate in the lakes. In general, low molecular weight PAHs (LMWPAHs) were more abundant than high molecular weight PAHs (HMWPAHs) in both pre- and post-monsoon seasons in surface and core sediment samples. The 4-ring PAHs were the most profuse among all samples, followed by the 5-ring, 3-ring, and 2-ring PAHs. The average diagnostic ratio indicated that PAHs sourced from pyrogenic coal combustion, fossil fuel and diesel emissions. Metal fractionation revealed the predominant presence of Fe in all the HALs, with the highest concentration in Lake P.T. Tso. The residual fraction was highest for all HMs, except Cd, where the exchangeable fraction was prominent. HYSPLIT model implied that long-range transported atmospheric pollution from the mid-Gangetic plains significantly impacts the sediment of lakes in the region.
Association of microplastics with heavy metals and antibiotic resistance bacteria/genes in natural ecosystems – A perspective through science mapping approach
Mazumder P., Dash S., Kumar M., Silori R., Tiwari A., Khwairakpam M., Kalamdhad A.S.
Review, Groundwater for Sustainable Development, 2023, DOI Link
View abstract ⏷
Micro and nano-plastics (MNPs) have been considered one of the major emerging contaminants that require immediate attention. Their potential impact on the natural ecosystems is yet to be understood, especially their associations with other contaminants like heavy metals and organisms essential for the sustenance of life, i.e., microbes. Microplastics (MPs) also act as sources and carriers of pollutants, similar to macro and mesoplastics, that leach harmful chemicals such as Polybrominated Diphenyl Ethers (PBDEs), Pharmaceutical and Personal Care Products (PPCPs), Endocrine Disruptive Chemicals (EDCs), etc. They also behave like super sponge materials which adsorb microbes such as antibiotic resistance bacteria (ARBs), and coronavirus, making their concentration much higher than the ambient environment. Among these microbes, heavy metal-resistance (MRGs) and antibiotic-resistance genes (ARGs) carry immense significance. The present study provides an in-depth review analysis of the works published related to the association of MPs to heavy metals and ARGs. 1526 articles were investigated after the dataset was subjected to a three-stage screening process. A scientometric analysis revealing details about the most productive and influential journals, co-authorship details, most influential publications, most cited keywords, and most active countries in the research domain was conducted. This provided significant information regarding various aspects of the published works of literature. Subsequently, a qualitative discussion was carried out wherein a detailed discussion with regard to the trends in research on sub-areas in the broad domain was conducted. This resulted in identifying the gaps in the available literature, which paved the way for providing a framework for future research. Through this study, it is expected that the readers will be exposed to a summary of the overall research that has been conducted to date, and the manuscript will act as a guide for future research.
Ecological and health risk assessment associated with translocation of heavy metals in Lycopersicum esculentum from farmland soil treated with different composts
Mazumder P., Dash S., Khwairakpam M., Kalamdhad A.S.
Article, Journal of Environmental Management, 2023, DOI Link
View abstract ⏷
To meet the United Nations' Sustainable Development Goals, agricultural soil which is a non-renewable natural resource must be carefully managed. Heavy metals present in agricultural soil may imperil food security and instigate extreme risks to human health. Organic wastes have been long known for valuable amendments to soil thereby, improving overall soil health. In the present study, Echhornia crassipes, Hydrilla verticillata, and vegetable waste, was utilized to prepare compost amendments. Lycopersicum esculentum was used to metal uptake from compost amended soils. 5%, 10%, 15%, 25%, and 35% compost: soil (w/w) were studied to understand metal translocation in plants. Potential Ecological risk indices showed that while the degree of risk was medium for the natural soil, it reduced to slight for the soil amended with WHC and VWC for all compositions. The non-carcinogenic risks associated with the human health reduced on application of the composts, however, they still remained substantial for Fe, As, and Pb for WHC, HVC, and VWC composts at higher application ratios, especially among children. On the other hand, the carcinogenic health index values which were calculated to estimate the risk associated with ingestion of L. esculentum, showed a decrease in risk for all the metals studied, upon soil amendment. Soil amended with HVC compost showed an increase in carcinogenic risk for As, Pb, and Cr. Finally, we conclude that biological soil remediation is economical and a sustainable land management strategy that may lead to green and clean remediation solutions for metal contaminated soil.
Preface
Haq I., Kalamdhad A.S., Dash S.
Editorial, Environmental Degradation: Monitoring, Assessment and Treatment Technologies, 2022,
Environmental Degradation: Monitoring, Assessment and Treatment Technologies
Haq I., Kalamdhad A.S., Dash S.
Book, Environmental Degradation: Monitoring, Assessment and Treatment Technologies, 2022, DOI Link
View abstract ⏷
This book focuses on municipal and industrial water and wastewater treatment technologies. The chapters provide detailed information about wastewaters' occurrence, source, characteristics, toxicity, and conventional and advanced treatment process. In addition, the book presents chapters relating to different monitoring methods adopted for water quality assessment in different water bodies. This book aims to boost the knowledge of students, researchers, scientists, professors, engineers and professionals who aspire to work in the field of environmental science, environmental biotechnology, environmental microbiology, civil/environmental engineering, eco-toxicology and other relevant areas of industrial waste management for the safety of the environment. The readers of the book will obtain valuable information related to various environmental problems and their solutions.
Steady and Unsteady Hydrodynamic Simulation of Pili River as a Potential Flood Warning System Using HEC-RAS
Dash S., Vijay R., Gupta R.
Conference paper, Lecture Notes in Civil Engineering, 2022, DOI Link
View abstract ⏷
In the present study, one-dimensional hydrodynamic simulation of the Pili River (Study Area) for the steady flow was carried out using ArcGIS and HEC-RAS considering floods of 5, 10, 25, 50 and 100 years return period under existing and modified river geometry. The results were transferred to Google Earth for the delineation of flood lines. Furthermore, one and two-dimensional unsteady-state simulations were carried out for floods of 25, 50 and 100 years return period using RAS Mapper, which provided a 2D visualization of the unsteady flow on Digital Elevation Model (DEM) and Google Earth. Validation of the model output results was carried out for the average dry weather flow, the depths of which were obtained from 14 different locations along the entire stretch of the study area. The validation results indicated the model having a correlation factor of 0.6447 with the actual on-site data obtained. Hence, the model was used to provide reliable information regarding the amount of submergence during an event of a flood. The flood lines obtained through the model will further help in providing a potential warning for floods and will also act as a guiding measure for the implementation of river training works such as dredging, slope stabilization and construction of levees for future riverbed planning and development activities along the river stretch.
Employing Multivariate Statistics as a Tool for Developing Water Quality Index (WQI) for the Assessment of Water Quality of Deepor Beel, Assam, India
Dash S., Borah S.S., Kalamdhad A.S.
Book chapter, Environmental Degradation: Monitoring, Assessment and Treatment Technologies, 2022, DOI Link
View abstract ⏷
The rapid growth of population has led to intense urbanisation in the city of Guwahati, which has caused the water bodies in the city to deteriorate (both quality as well as quantity wise) to a substantial extent (Das et al., 2003). Deepor Beel (a Ramsar site) is one such water body that has been continuously degraded owing to a sudden increase in the urban built-up of Guwahati city (Dash et al., 2018). Assessment of the water quality of a particular water body requires continuous monitoring and analyses of several parameters. This, in turn, contributes to the development of large and complex water quality datasets that are difficult to interpret. Traditionally, the water quality of a particular water body was assessed by comparing the observed values of some water quality parameters with their corresponding quality standard values (Pesce and Wunderlin, 2000). This, however, makes the sustainable management of water resources very challenging and sophisticated, as well as time-consuming (Sun et al., 2016; Wang et al., 2015). Quality indices have proved to be of immense help to water quality researchers around the globe for the past few decades. This is owed to their extreme simplicity of dataset interpretation. Water quality index (WQI) is a mathematical representation of the datasets for categorising the water quality in a more straightforward yet informative manner, thus assessing the pollution status of a particular water body. Numerous attempts have been carried out in developing WQIs, depending on various methodologies adopted by several researchers (Akter et al., 2016; Bora and Goswami, 2017; Liou et al., 2004; Ramakrishnaiah et al., 2009; Said et al., 2004; Şener et al., 2017; Vasanthavigar et al., 2010; Wu et al., 2018). It has been proved over the years that the WQI approach is the most practical and effective way of water quality representation of a particular waterbody, both spatially and temporally. It also facilitates in comparing various sampling locations based on their pollution levels and determining their trends (Sun et al., 2016).
Monitoring Heavy Metals Concentrations in a Natural Wetland and Aquatic Plant Eichhornia Crassipes for Assessment of Its Biomonitoring Potential
Dash S., Kalamdhad A.S.
Conference paper, Lecture Notes in Civil Engineering, 2022, DOI Link
View abstract ⏷
In the present study, seven heavy metals, i.e., Cr, Cd, Fe, Mn, Cu, Pb and Mg were used for estimation of heavy metal pollution and the bioconcentration and translocation factors corresponding to the plant Eichhornia crassipes in Deepor Beel, Assam, India. Sediment and water hyacinth (Eichhornia crassipes) samples were collected from three different zones of the wetland; zone I is proximate to the Boragaon landfill region, zone II is the central portion of the wetland and zone III constitutes the site in the industrial zone. It was observed that the heavy metal concentrations in the sediment column of the wetland are significantly higher compared to the water hyacinths. Furthermore, in the water hyacinth samples collected from the three zones, it was observed that the heavy metal concentrations were significantly higher in the roots as compared to the shoots. This indicated an insignificant translocation of heavy metals from the roots to the shoots, as a result of which, all the heavy metals are concentrated in the roots. This was verified by the translocation factor, whose values were found to be minimal and inconsequential. Also, the bioconcentration factor of the water hyacinth samples was estimated and found to be higher in the central and industrial region, which suggests that the metal availability was very low in the landfill region, despite having considerably higher concentrations of heavy metals in the sediments. The findings of the study would prove to be consequential in determining the adverse effects of eutrophication and heavy metal contamination in the wetland, which would thereby aid in undertaking necessary steps in curbing the pollution levels.
Sewage surveillance for SARS-CoV-2: Molecular detection, quantification, and normalization factors
Mazumder P., Dash S., Honda R., Sonne C., Kumar M.
Review, Current Opinion in Environmental Science and Health, 2022, DOI Link
View abstract ⏷
The presence of severe acute respiratory syndrome coronavirus–2 (SARS-CoV-2) in wastewater systems provides a primary indication of the coronavirus disease 2019 (COVID-19) spread throughout communities worldwide. Droplet digital polymerase chain reaction (dd-PCR) or reverse transcription-polymerase chain reaction (RT-PCR) administration of SARS-CoV-2 in wastewaters provides a reliable and efficient technology for gathering secondary local-level public health data. Often the accuracy of prevalence estimation is hampered by many methodological issues connected with wastewater surveillance. Still, more studies are needed to use and create efficient approaches for deciphering the actual SARS-CoV-2 indication from noise in the specimens/samples. Nearly 39–65% of positive patients and asymptomatic carriers expel the virus through their faeces however, only ∼6% of the infected hosts eject it through their urine. COVID-19 positive patients can shed the remnants of the SARS-CoV-2 RNA virus within the concentrations ∼103–108 copies/L. However, it can decrease up to 102 copies/L in wastewaters due to dilution. Environmental virology and microbiology laboratories play a significant role in the identification and analysis of SARS-CoV-2 ribonucleic acid (RNA) in waste and ambient waters worldwide. Virus extraction or recovery from the wastewater (However, due to lack of knowledge, established procedures, and integrated quality assurance/quality control (QA/QC) approaches, the novel coronavirus RNA investigation for estimating current illnesses and predicting future outbreaks is insufficient and/or conducted inadequately. The present manuscript is a technical review of the various methods and factors considered during the identification of SARS-CoV-2 genetic material in wastewaters and/or sludge, including tips and tricks to be taken care of during sampling, virus concentration, normalization, PCR inhibition, and trend line smoothening when compared with clinically active/positive cases.
Systematic bibliographic research on eutrophication-based ecological modelling of aquatic ecosystems through the lens of science mapping
Dash S., Kalamdhad A.S.
Review, Ecological Modelling, 2022, DOI Link
View abstract ⏷
The present study provides a scientific investigation of a detailed review of the published works in the domain of eutrophication-based ecological modelling till the year 2020. A total of 399 articles were extracted for final analyses, which were subjected to a three-step hierarchical procedure; Bibliographic examination, scientometric investigation, and qualitative assessment. The bibliographic test filtered 320 samples, based on which the article samples were subjected to several scientometric analyses, such as identifying the most influential and productive journals, researchers, articles, and countries. Keyword analysis revealed the most frequently used keywords in the research domain and amongst scholars around the world. The scientometric studies were followed by a qualitative assessment wherein the current trends in research were discussed. This was followed by identifying the critical gaps in research to provide future direction. Thus, this research offers a more comprehensive and holistic approach towards the critical review of the published literature, thereby providing essential insights to the researchers regarding the existing practices of developing eutrophication-based ecological models and the future prospects lying ahead.
Development of function-specific indices for assessing water quality based on the proposed modifications of the expected conflicts on existing information entropy weights
Dash S., Kalamdhad A.S.
Article, Environmental Monitoring and Assessment, 2022, DOI Link
View abstract ⏷
Water serves numerous purposes besides drinking, such as irrigation and industrial usage. Most water quality indices developed have primarily focused on drinking water quality. However, assessing other functionalities of water bodies is also equally essential. The present study proposes a novel technique to measure water quality for two highly specific water use, i.e., assessing heavy metal contamination and irrigation suitability. The ambiguities in the current practice of entropy weights were identified, and a novel method was proposed, considering a three-dimensional approach instead of the conventional two-dimensional procedure. Weights to different parameters were assigned based on the probability estimates obtained from the frequency of observed values within acceptable limits. The proposed method’s reliability, correctness, and applicability were tested using Deepor Beel’s water quality dataset. Results were highly consistent with the experimental values and correlated well with other established methods. The efficacy of the method was determined by employing sensitivity analyses. Both indices showed high reliability and correctness, as no single parameter was found to be highly sensitive compared to others. Therefore, the proposed methodology proved to be the most reasonable, incorporating all the factors required for a reliable water quality monitoring program.
Hydrochemical dynamics of water quality for irrigation use and introducing a new water quality index incorporating multivariate statistics
Dash S., Kalamdhad A.S.
Article, Environmental Earth Sciences, 2021, DOI Link
View abstract ⏷
Anthropogenic contamination, including the adaptation of sophisticated agricultural methodologies, has rendered a steep decline in the water and soil quality across the globe. This, in turn, has adversely affected the crop productivity. Hence, to utilize water from a source, a review assessment regarding the water suitability is essential. The present study proposes a new irrigation-based water quality index (IWQI), integrating statistics; hierarchical cluster analysis (HCA) and principal component analysis (PCA), to specific water use. Twenty-three sampling locations were chosen for analyses of 13 water quality parameters from October 2017 to February 2019 from Deepor Beel, Assam, to determine the efficacy of the proposed water quality index. HCA divided the 23 locations into 3 clusters, after which, PCA for each independent cluster provided component scores. These component scores were then used to estimate weights for each parameter for all the 23 locations. The IWQI categorized all the sampling locations as “Very Good”, thereby rendering them fit for irrigation. This was validated through the use of various irrigation parameters, such as sodium adsorption ratio (SAR), Kelly’s ratio (KR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), permeability index (PI), and magnesium adsorption ratio (MgR). USSL and Wilcox plots were also considered for the correlation. IWQI was observed to provide an excellent association with all the parameters. Thus, the study would prove fruitful in establishing long-term and extensive management plans to the conservation of natural water resources.
Science mapping approach to critical reviewing of published literature on water quality indexing
Dash S., Kalamdhad A.S.
Review, Ecological Indicators, 2021, DOI Link
View abstract ⏷
Water quality has always remained paramount when it comes to sustainable development. The most convenient method of determining the health of a particular water body is through water quality indexing. Based on the filtered 2049 articles published, the present review-based study was conducted for a science-based mapping to evaluate the research in the domain of water quality indexing until 2020. A three-stage sequential process; bibliometric examination, scientometric investigation, and qualitative valuation resulted in the identification of the most influential and productive journals, researchers, articles, and countries dynamic in the research field. Keyword analysis further revealed that groundwater quality assessment for drinking water has been the key focus of research among scholars. The scientometric analysis was followed by a qualitative discussion on the current topics of research; mainly categorized into four classes, i.e., specific indices, human intervention, performance assessment and emerging technologies, and also highlighting some of the significant research gaps. This was followed by presenting a research framework wherein, plausible future directives were proposed. This study thus provides a more comprehensive picture on the existing researches carried out in the domain of water quality indexing, identifying the primary gaps and thereby providing multi-disciplinary guidance for various researchers and practitioners linked to the current research to the future.
Heavy metal pollution and potential ecological risk assessment for surficial sediments of Deepor Beel, India
Dash S., Borah S.S., Kalamdhad A.S.
Article, Ecological Indicators, 2021, DOI Link
View abstract ⏷
The present study has been conducted for three objectives for the assessment of sediment pollution loadings and their ecological risk. Firstly, the hierarchical clustering of the raw sediment dataset was carried out, which categorized the sampling locations into three statistically significant clusters, depending on their similarities in behaviours. Clusters 1, 2, and 3 corresponded to high, moderate, and low pollution sites, respectively. The principal component analysis was then carried out on the dataset for three different seasons; pre-monsoon, monsoon and post-monsoon respectively, which showed significant temporal changes in the pollution sources. Various indices such as contamination factor, pollution load index, enrichment factor, and the geo-accumulation index showed that the wetland is most affected in the post-monsoon season as compared to other seasons. At the same time, monsoon remains the best. This was attributed to the significant increase in the wetland's water depth during the monsoon, coupled with the rise in precipitation capacity during the post-monsoon. Secondly, the potential ecological risk due to the contaminants displayed that the post-monsoon period has the greatest number of sites under the moderate risk category. In contrast, all the sites during the monsoon attributed to low risk. Also, Cd was found to be the primary contributor to ecological risk. Finally, chemical speciation analyses of all the heavy metals were conducted to determine their available forms in the sediment column. Cr, Mn, and Mg were observed to have a profoundly negative impact on aquatic ecology (available in F1 fraction in higher percentages). While Fe was predominant in reducible (F3) form, Cd was found to have equal contributions in reducible and oxidizable (F3 and F4, respectively) forms. Cu and Pb displayed typical complex characteristics of all the fractions in almost equal proportions. The results of the study indicated that although the anthropogenic interventions to the wetland have not been significant till yet, as far as the sediment contamination is concerned, it would be too late if swift and appropriate measures are not taken for restricting future probable contaminations.
Discussion on the existing methodology of entropy-weights in water quality indexing and proposal for a modification of the expected conflicts
Dash S., Kalamdhad A.S.
Article, Environmental Science and Pollution Research, 2021, DOI Link
View abstract ⏷
The present research focuses on addressing various ambiguities in the existing method of integrating information entropy and water quality, thereby presenting a novel approach for an entropy-weighted water quality index. A three-dimensional water quality dataset is considered in the proposed method, the third dimension being the sampling frequency factor. The probability of observed values adhering to desirable limits prescribed by a standard code is estimated, leading to the computation of information entropy and, eventually, entropy weights. These weights are then used for the computation of the Modified Entropy-weight Water Quality Index (MEWQI) values. To verify the proposed method’s applicability, the water quality dataset of Deepor Beel, India, was considered. IS 10500: 2012 was used for estimating MEWQI values. Results showed an excellent correlation with the observed dataset and their uncertainties of occurrence. The reliability and correctness of the proposed methodology were finally confirmed through both cluster analysis and sensitivity analysis. The cluster analysis showed remarkable associations with the computed MEWQI values, while the sensitivity analysis proved that no particular parameter was accountable for the contribution of MEWQI values; instead, all parameters exhibited equal contributions. The proposed methodology was thus found to be the most reasonable and reliable as it considered both factors, i.e., measured values concerning standard limits and the uncertainty, necessary for a consistent water quality monitoring program.
Understanding the dynamics of heavy metals in a freshwater ecosystem through their toxicity and bioavailability assay
Dash S., Kalamdhad A.S.
Article, Environment, Development and Sustainability, 2021, DOI Link
View abstract ⏷
The current study investigates on correlating the heavy metal contamination, its distribution, and the human health risk associated with all three components of an aquatic ecosystem. For this purpose, water, sediment, and fish samples (three species, notably Notopterus notopterus, Clarias batrachus, and Channa striata) from Deepor Beel were considered, and their heavy metal contamination and distribution were determined. The corresponding health risks were then evaluated for six different heavy metals; Cr, Cd, Fe, Mn, Cu, and Pb. Pb and Mn were found to significantly impact the non-carcinogenic human health risks for the water column. Simultaneously, Cd was considered to possess the highest potential for both carcinogenic and non-carcinogenic health effects in the sediment column. Cd also played a critical role in the fish samples' bioaccumulation factor, with the liver showing the maximum bioaccumulation potential. Furthermore, children were found to have considerably higher effects (both carcinogenic and non-carcinogenic) than adults. Finally, the sediment column was found to substantially contribute to the bioaccumulation factor in the fish biota, compared to the water column. The results of this investigation will thus prove consequential in designing, monitoring and restoring aquatic ecosystems.
Seasonal and spatial variation of DO and BOD for assessment of the water quality of brahmaputra river
Dash S., Borah S., Singh K.R., Kalamdhad A.S.
Book chapter, Lecture Notes in Civil Engineering, 2020, DOI Link
View abstract ⏷
In this study, an attempt has been made to monitor the water quality of the Brahmaputra river by analysing two major parameters, viz., DO and BOD by plotting various curves to determine the seasonal as well as the spatially variation of the parameters along the river stretch. The seasonal variation of DO in the Upper Assam region showed similar trends for the pre- and the post-monsoon period with a decreasing trend as the river flows from Kherghat to Dibrugarh and thereafter shows an increase of DO levels near Dhenuka paharh. A decreasing trend was again observed as the river passes through the Nimatighat region. Similarly, for the monsoon season the variation of DO showed an increasing trend as it passes through Dibrugarh and as the river progresses towards the downstream, discharges from various cities along the river stretch blend with the river water, thereby increasing its pollution levels and hence a decreasing trend was observed for the DO in the downstream portion of the Upper Assam region. As far as the variation of BOD along the river stretch is concerned, it was observed that it varies inversely as the DO, which can be seen as an appropriate co-relationship between the two parameters. Similarly, variations of the BOD and DO were obtained for the Lower Assam region. The spatial variation of the BOD and DO showed the map of the depicting the variation of the parameters along the entire river stretch. Proper visualisation of the maps obtained would thereby help in predicting the stretch most polluted so that proper river training works can be done to restore the water quality in the river.
Study of the limnology of wetlands through a one-dimensional model for assessing the eutrophication levels induced by various pollution sources
Dash S., Borah S.S., Kalamdhad A.S.
Article, Ecological Modelling, 2020, DOI Link
View abstract ⏷
Eutrophication of lakes and wetlands, resulting from the discharge of excess nutrients, has become a matter of primary concern. The entire ecology of a eutrophic wetland gets severely affected due to the substantial degradation of its water quality. Formulation of ecological models assists in determining the nutrient dynamics of a particular ecosystem, thereby providing an idea of the significant causative parameters aiding eutrophication. The present study aims at providing a suitable foundation for the development of an eutrophic-ecological model for Deepor Beel, India. Water, sediment, and water hyacinth samples were collected from various parts of the wetland and subjected to analyses on a continuous basis from Oct’ 2017 to Feb’ 2019. The collected samples were analysed for various physico-chemical parameters, quintessential for the development of a eutrophication based ecological model. A conceptual diagram was first constructed, and the corresponding differential equations about different functions were formulated. Subsequently, a code was developed in MATLAB based on the logic formulated through the conceptual diagram. Sensitivity analysis was first performed on various state variables, identifying the parameters most sensitive and thus, exhibiting maximum variability in the model. The model was then subjected to calibration for defining the rate constants based on which; it was subjected to further validation. Finally, the model was simulated for two plausible alternatives to verify the reduction of the eutrophication levels in Deepor Beel; (i) Harvesting of water hyacinths and (ii) Setting up of a treatment unit for nitrogen and phosphorus removal. The results obtained for both cases indicated that, harvesting of water hyacinths would not provide a suitable long-term and effective solution. However, setting up of a treatment unit for phosphorus and nitrogen removal can aid in a significant reduction in the nutrient levels in the wetland, thereby assisting in curbing the eutrophication levels. The results obtained through this study would provide significant assistance to the various government as well as private agencies and policymakers for carrying out effective solutions for the increasing eutrophication levels in Deepor Beel, which would thereby help in reviving the wetland.
Application of positive matrix factorization receptor model and elemental analysis for the assessment of sediment contamination and their source apportionment of Deepor Beel, Assam, India
Dash S., Borah S.S., Kalamdhad A.S.
Article, Ecological Indicators, 2020, DOI Link
View abstract ⏷
The present study is a first of its kind on the sediment contamination in Deepor Beel, which makes use of source apportionment receptor modelling technique {positive matrix factorization (PMF)} for determining and quantifying the sources’ contribution to the pollution of the sediment column of Deepor Beel, Assam. Sediment samples were collected and analysed for seven different heavy metals from 23 sampling locations for a period from October 2017 to February 2019. Polling the entire dataset to a single matrix and carrying out multiple iterations revealed that four factors were optimum and thus, was applied for the simulation of the model. It was observed that the factors 1, 2, 3 and 4 corresponded to the soil parent material, leaching from the Boragaon landfill, discharge of agricultural and domestic wastes, and effluents from the industries and traffic emissions respectively. The sediment samples were further subjected to elemental analysis; X-ray powder diffraction (XRD) followed by Scanning electron microscope - Energy Dispersive X-Ray Spectroscopy (SEM – EDS), to determine the elemental composition and forms of heavy metals present in the sediment columns from various parts of the wetland. Sediment sample collected from the proximity of the landfill site was observed to be affected the most, probably due to leaching effects, especially during the monsoon. The central zone, however, was found to be devoid of any anthropogenic contaminations, while the sediment column near the industrial complex was found to be contaminated to a moderate extent. The study indicates the quantum of sediment contamination in the wetland and the causative parameters responsible, thus proving to be of immense help to the various governmental bodies in the planning and management of resources for sediment remediation of Deepor Beel.
Application of environmetrics tools for geochemistry, water quality assessment and apportionment of pollution sources in Deepor beel, Assam, India
Dash S., Borah S.S., Kalamdhad A.S.
Article, Water Practice and Technology, 2020, DOI Link
View abstract ⏷
The present study uses four Environmetrics tools: hierarchical cluster analysis (HCA), discriminant analysis (DA), principal component analysis (PCA), and positive matrix factorization (PMF) for the assessment of water quality and geochemistry of Deepor Beel, Assam, India. The hierarchical clustering classified the 23 sampling locations into three clusters, classifying them as sites of high, low, and moderate contamination respectively. The DA of the water quality dataset resulted in 9 parameters (EC, TDS, TSS, PO34, Na+, Mg, Cd, Pb and OrgN), primarily respon-sible for the discrimination of the clusters. PCA was then employed on the normalized dataset for the identification of potential pollution sources. PCA yielded two significant principal components, describing anthro-pogenic and natural factors defining the water contamination. Finally, PMF was employed on the dataset matrix, with four pre-defined factors. Leaching from Boragaon landfill site, surface water runoff, discharge of effluents from the industries in the wetland and discharge from Basistha River were found to be the major contributors. The results of this study provide a comprehensive correlation between water quality parameters and their sources, which would thereby assist in better planning and management of wetland restoration.
A modified indexing approach for assessment of heavy metal contamination in Deepor Beel, India
Dash S., Borah S.S., Kalamdhad A.
Article, Ecological Indicators, 2019, DOI Link
View abstract ⏷
In the present study, spatial and temporal variability of the heavy metals were investigated for Deepor Beel, India and a modified indexing approach for heavy metal contamination was proposed based on the statistical analyses of the monitored values. Water samples from 23 monitoring stations were collected for a period of one year and subjected to analysis for 7 different heavy metals (Mg, Cr, Cd, Fe, Mn, Cu, and Pb). The observed water quality dataset was first subjected to hierarchical clustering (HCA), which categorized the 23 monitoring locations into 3 statistically independent clusters based on the site similarities i.e. Low pollution (LP), High pollution (HP)and Moderate pollution (MP)respectively. Principal component analysis (PCA)technique was then applied to the three independent clusters to obtain principal components (PCs). These PCs were employed for calculating the weights of each component, from which the proposed heavy metal index (HMI)was estimated. The overall HMI value for Deepor Beel was found to be 123.52, which classified the water in Deepor Beel as “Poor”. Leaching from the contaminated landfill in the proximity to the wetland was found to be a primary source of contamination with respect to heavy metals. The efficacy of HMI was verified by comparing it with the existing heavy metal pollution index (HPI), contamination index (CI)and heavy metal evaluation index (HEI). Results of this study indicate HMI to be a more effective and reliable tool for water quality assessment with respect to heavy metal contamination.
Monitoring and assessment of deepor beel water quality using multivariate statistical tools
Dash S., Borah S.S., Kalamdhad A.
Article, Water Practice and Technology, 2018, DOI Link
View abstract ⏷
The aim of this study was application of multivariate statistical techniques – e.g., hierarchical cluster analysis (HCA), principal component analysis (PCA) and discriminant analysis (DA) – to analyse significant sources affecting water quality in Deepor Beel. Laboratory analyses for 20 water quality parameters were carried out on samples collected from 23 monitoring stations. HCA was used on the raw data, categorising the 23 sampling locations into three clusters, i.e., sites of relatively high (HP), moderate (MP) and low pollution (LP), based on water quality similarities at the sampling locations. The HCA results were then used to carry out PCA, yielding different principal components (PCs) and providing information about the respective sites’ pollution factors/ sources. The PCA for HP sites resulted in the identification of six PCs accounting for more than 84% of the total cumulative variance. Similarly, the PCA for LP and MP sites resulted in two and five PCs, respectively, each accounting for 100% of total cumulative variance. Finally, the raw dataset was subjected to DA. Four parameters, i.e., BOD5, COD, TSS and SO2- 4 were shown to account for large spatial variations in the wetland’s water quality and exert the most influence.
