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‘Blue carbon’ has recently seized the attention of the scientific communities as they are believed to provide the benefits of climate change mitigation given its high potential to store carbon under unfavourable conditions. Keeping in mind the importance of the carbon storage capacity of mangroves, the present study has been carried out to determine the sedimentary organic carbon stock in Coringa mangroves. The value of total organic carbon (TOC) ranges from 0.63 to 2.76% with a mean value of 1.30±4.3%. The value of total nitrogen (TN) varies from 0.04 to 0.19% with an average value of 0.08±0.03%. Dry Bulk Density (DBD) ranges from 0.63 to 2.58 gm cm-3 with a mean value of 1.33±0.19 gm cm-3. The mean value of sedimentary carbon stock (SCS) in Coringa mangrove is 158±32.60 Mg C ha-1. This amounts to the below-ground sedimentary carbon stock being 1.86 Tg C and represents the equivalent CO2 emission of 579.9 Mg CO2e ha-1. The TOC, TN, DBD, and SCS show significant spatial variation among the different sites. The maximum carbon stock is found in densely vegetated Coringa mangroves, followed by moderately vegetated Gaderu mangroves and the least is found in the degraded forest of Matlapalem mangroves. Grain size parameters signify that there is no definite relationship between the organic carbon content and the abundance of finer sediments fractions in the Coringa mangrove. The higher carbon stock in Coringa mangroves reveals their importance in storing carbon and hence could have relevance on a national scale too and play an important role in climate change mitigation

Chandratal lake (32°28′30.65″ N 77°37′1.42″ E) located at the junction of Indian Summer Monsoon and Westerlies in the Northwestern Himalaya give an opportunity to reconstruct climate variability over the last ~6300 cal yr BP. Here, we used multi-proxy (Amino acids, Biogenic silica, grain size and total organic carbon) to link climate change and organic burial during the mid-Holocene period. The proxy records captured the changes in monsoon patterns, linking with Holocene climate optimum (HCO) during the ~6344- 5821 cal BP. The sediment profile begins with a wetter and moist climate mostly from the terrestrial environment inputs, corresponding to the warm Holocene Climate Optimum (HCO) period (~6344 - 5821 cal yr BP). A stable condition of the geochemical proxies during ~5821-3780 cal yr BP reveals a shifting of a moisture source, catchment stability and cold/dry climate in correspondence with reduced precipitation. The period from ~3780 to 2129 cal yr BP, follows a gradual increase of organic matter deposition and supported with an elevated atomic C/N ratio of 13.1 (mean value). Further association of organic matter with the coarser grain particles, suggesting a wetter climate from increasing runoff which is in correlation with the reinforcement of the precipitation during this time interval. From ~2129 to 696 cal yr BP, reduced precipitation/dry condition was observed with a shift in the autochthonous production of organic matter (C/N ratio of 8.91). Increase in BSi content suggests an ameliorated climate at this interval; however, the lower organic matter content (mean, 1.79%) and shift in the correlation of organic matter from coarse grains to finer grain size, suggesting little contributions from the terrestrial activities favouring the dry environment and abundant diatoms growth. The paleoenvironmental variations illustrate in the study is comparable to other findings recorded in the Himalayan region.

Himalayan glaciers are retreating, and glacial lakes are evolving and proliferating as a result of climate change. Glacier retreat marks in the formation and expansion, and sometimes outburst of moraine-dammed lakes. Lato Lake is one of the high-altitude and unexplored glacial lakes upstream of Gya-Miru village in the Leh-Ladakh region. This study is the first of its kind to assess hydrogeochemistry (HCO3−, SO42−, NO3−, Cl−, F−, Ca2+, Mg2+, Na+, and K+) and studying the dynamics of a moraine-dammed lake in the Ladakh Himalayas. We observed substantial expansion of Lato Lake over the past 50 years between 1969 and 2019, and the areas of the lake have increased while the glacier area is reduced by 16.4% and 4.15%, respectively. The pH values ranging from 7.6 to 8.1 show slightly alkaline. HCO3−, Ca2+, and SO42− were the most dominant ions during the study period 2018–19. The high (Ca2+ + Mg2+) and a low (Na+ + K+) ratio to the total cations show that Lato Lake receives ions from rock weathering, primarily from carbonate rocks. Gibbs and Na-Mixing plot also support the hydrogeochemistry of lake water was primarily controlled by rock weathering. HYSPILT backward trajectory model suggested that atmospheric input mainly originated from the seawater vapor transported by the summer monsoonal and westerly circulation systems. Results show that the lake has a substantial impact on the long-range transport of ocean water relative to local interferences.

This review manuscript addresses hydro-meteorological correlations of various glaciers situated in the Himalayan region. Meteorological parameters influence the discharge pattern of the glacier. A strong correlation has been observed between discharge and air temperature of the studied Himalayan glaciers. Whereas, other meteorological parameters such as wind speed and wind direction etc. were not significantly correlated with the meltwater runoff of different glaciers in this region. In general, variability (Cv) in discharge from the various Himalayan glaciers such as Chhota Shigri and Gangotri glaciers follow the variability (Cv) in the temperature of these glaciers. Maximum variability (Cv) in meltwater runoff from the Chhota Shigri glacier has been reported in the month of September, which might be due to the fast decline in stream runoff and air temperature of the study area during the month of September. A strong relationship has been observed between suspended sediment concentration and temperature of the majority of studied Himalayan glaciers. Such type of result shows that the suspended sediment concentration in the glacial meltwater has increased with rising air temperature in this region.

Glaciers act as natural indicators of climate response and natural buffers of the hydrological cycle. Hence, continuous monitoring of glaciers is very crucial for which remote sensing techniques have emerged as a powerful tool to understand the micro-level variation and dynamics of glaciers. Unfortunately, a database involving complete basin-level approach and an extensive temporal range is not available for the entire Chandra-Bhaga (CB) sub-basin. Thus, the present investigation attempts to account for the extent of deglaciation in the CB basin showing that 16.7 percent of the glaciated area has been lost during 1989-2019. Moreover, the last three decades have witnessed a rapid rate of loss for small and medium-sized glaciers as compared to larger glaciers. Adding to it, the basin has also shown an upwards shift of mean elevation in this period. Over the last decade, an increasing temperature in the western Himalayas and Hindu Kush regions, as asserted by previous studies, have led to spatio-temporal changes in the glaciated area. The extent of deglaciation alongwith the glacier-climate behaviour and response can also provide a link to measure the topographical parameters.

In the year 2013, the Northwestern Himalaya witnessed an extreme hydrological event that severely affected the upper Ganga Basin. The unexpected high sediment mobilisation in the basin affected the human population, infrastructure, and ecology in several reaches of the Ganga river and its tributaries. In an exceedingly affected reach, the Kedarnath valley, a considerable sediment volume (∼26243 × 104 m3) was mobilised during the 2013 extreme hydrological event. In the Srinagar valley, up to 50 × 104 m3 of legacy sediment was washed away during the same event. This sediment mobilisation generated sediment pulses in the affected region, which is assessed through remote sensing, field observations and existing literature, in the Kedarnath and Srinagar valleys. Results show that the evolution of translative, dispersive, and their combined sediment pulse pattern in both selected reaches of the upper Ganga Basin. The mountainous region of the upper Ganga basin has very few monitoring stations observing sediment movement, and data from such stations are mostly unavailable due to which our understanding of the sediment movement in the Himalaya remains very poor. Therefore, it is suggested that there is a need for detailed studies of the sediment transport mechanism in the Himalayan river basins especially during such extreme hydrological events when large volume of sediment is mobilised.

Phewa Lake in Nepal is a lake of international importance providing crucial ecological and economic services. However, increased urbanization, population growth and anthropogenic activities have resulted in degradation of the lake. Thus, understanding the lake hydro-geochemistry is crucial for identifying sources of elements. Preceding studies have mostly covered limnological and physico-chemical assessments which are not sufficient to explain the lake catchment characteristics. This study has assessed the major ions in relation to their hydro-geochemical processes in the catchment. To evaluate monsoonal impact, the rainwater was also analyzed. The major ions were determined by using standard methods. The results revealed significant seasonal variations in temperature, pH, TDS, EC, and most of the major ions. There was domination of the total anions (Tz-) over the total cations (Tz+) indicating possible ionic contribution through decomposition of organic compounds. The domination of Ca2+, Mg2+ and HCO3- elucidates influence of carbonate weathering. The high (>1) equivalent ratio for (Ca2++Mg2+)/(Na++K+), and (Ca2++Mg2+)/(Tz+) ratio ≈1 also suggest abundance of (Ca2++Mg2+) and prevalence of carbonate weathering. The low (

Ranau landslides mostly occur due to moisture content and soil properties. In this study, the effect of moisture content on soil strength was analyzed using Unconfined Compression Test. Five samples were taken around Kampung Lohan which two are Crocker Formation soil samples (K1 and K3) and three were ultrabasic soil samples (K2, K4 and K5). The term ‘Decrement Difference of Unconfined Compression Strength’ is used to define the percentage drop of shear strength difference of the manipulated oversaturated samples to its shear strength at optimum moisture. The highest drop was 90.18% in clayey soil (K2) because it is rich in minerals that are able to absorb and adsorb water while lowest drop of 50.32% by sandy clay with silt (K1). Thus, sand rich soils of Crocker Formation have higher compression strength than ultrabasic soils with expansive clay while the moisture effect on soil is directly proportional to thecompression strength.

Groundwater resources are increasingly important as the main supply of fresh water for household, industrial, and agricultural activities. However, overuse and depletion of these resources can lead to water scarcity and resource deterioration. Therefore, assessing groundwater availability is essential for sustainable water management. This study aims to identify potential groundwater zones in the Bilaspur district of Himachal Pradesh using the Multi Influencing Factor (MIF) technique, a modern decision-making method widely used in various sectors. Geospatial models were integrated with the MIF technique to evaluate prospective groundwater areas. Grid layouts of all underground water influencing variables were given a predetermined score and weight in this decision-making strategy. The potential groundwater areas were then statistically assessed using graded data maps of slope, lithology, land-use, lineament, aspect, elevation, soil, drainage, geomorphology, and rainfall. These maps were converted into raster data using the raster converter tool in ArcGIS software, utilizing Survey of India toposheets, SRTM DEM data, and Resourcesat-2A satellite imageries. The prospective groundwater zones obtained were classified into five categories: nil–very low, covering 0.34% of the total area; very low–low (51.64%); low–moderate (4.92%); moderate–high (18%) and high–very high (25%). Scholars and policymakers can collaborate to develop systematic exploration plans for future developments and implement preservative and protective strategies by identifying groundwater recharge zones to reduce groundwater levels. This study provides valuable insights for long-term planning and management of water resources in the region.

Warming-induced expansion in vegetation coverage and activity can accelerate the montane hydrological regimes. However, the climate impacts on ecohydrology of forested valleys of the Himalaya are uncertain. In this study, utilizing results of about three centuries of cellulose isotope chronologies (δ 13C and δ 18O) of dominant tree species, geo-chronological proxies, bio-geophysical dataset and simulations including satellite observations, we show an activation in the ecophysiological processes including evapotranspiration (ET) since the 1950s. Observation suggests rapid greening, while isotopic records indicate enhanced assimilation and transpiration in deciduous species vis-à-vis conifers post 1950s. Given strong vegetation-precipitation feedback and superimposed on the increasing trends of conducive atmospheric factors affecting valley-scale convective processes, intensification in forest ET is manifesting in a progressive enhancement in extreme rainfall events (EREs) since the last few decades. Results suggest that representation of ecophysiological processes and dynamics of seasonal moisture loading in observational and modelling framework is critical for understanding EREs under climate change.

This study presents a recent estimate (for year 2017) of ice thickness and volume of a small glacier called Patsio Glacier located in Western Himalayas. Also, the present study aims to examine whether the improvement in GlabTop2 based estimates obtained for Chhota Shigri Glacier through the use of relatively accurate and high-resolution Digital Elevation Model (DEM) and glacier specific model parameterisation is consistent and can be extended to other glaciers. The version of GlabTop2 model used in this study is GlabTop2_IITB (Glacier Bed Topography version 2_Indian Institute of Technology Bombay). For validation purpose, ground penetrating radar (GPR) survey-based ice thickness estimates available at four cross-section profiles collected during July 2017 was used. Root mean square error (RMSE) of the modelled ice thickness estimates is about 14 m. Average and the maximum thickness of the modelled glacier ice is about 45 and 129 m, respectively. The obtained results when compared with an earlier study carried out using velocity-based approach indicate a significant improvement in the modelling accuracy. Moreover, a 16 percentage points reduction in uncertainty of the estimated ice thickness is seen when compared with a previous study involving different version of GlabTop2 model for Himalaya–Karakoram region. This is perhaps due to the use of a relatively accurate and high-resolution DEM and model parameterisation scheme adopted in this study, thus confirming the consistency of the modelling approach for different glaciers. Based on the obtained ice thickness estimates, the modelled volume of the glacier stored ice was calculated to be 0.11198 ± 0.0162 km3 in 2017.

This study mainly focuses on the source identification of various ions in meltwater and estimation of CO2 consumption rate by chemical weathering in the Batal glacier basin on the basis of 2 years of study (2015 and 2017). The glacier meltwater has been monitored as slightly acidic in nature having mean pH value of 6.6. Ca2+ was observed as the most dominant cation contributing about 76% of TZ+ (total cations), whereas SO42− was observed as the most dominant anion contributing about 70% of TZ− (total anions) in the stream meltwater. High ratios of (Ca + Mg) versus TZ+ (mean value: 0.89 ± 0.02) and (Ca + Mg) versus (Na + K) (mean value: 8.51 ± 2.07) elucidate that stream water chemistry of the Batal glacier is largely controlled by carbonate weathering. Concentration of total dissolved solid in the glacial stream water was higher during the low-melt season (September) and lower during the high-melt period (July). The average value of daily mean TDS flux of the study area was calculated to be 12.4 t/day. The mean values of CWR (carbonate weathering rate) and SWR (silicate weathering rate) for the Batal glacier basin were calculated to be 97.4 and 22.8 t/km2/year, showing higher contribution of CWR as compared to SWR in the investigation area. CO2 consumption rate by the combined silicate and carbonate (chemical) weathering was estimated to be 11.1 × 105, 28.8 × 105 and 35.5 × 105 mol/km2/year during the study period September 2015, June 2017 and July 2017, respectively. The annual CO2 drawdown by the Batal glacier basin on the basis of CO2 consumption rate by chemical weathering is much lower as compared to the Gangotri glacier, which may be due to bigger size and higher meltwater runoff of the Gangotri glacier as compared to the Batal glacier.

The drill and blast technique have been widely used recently due to demand for natural building materials like rock aggregates. However, the intensity of blasting effects has been questioned on its validity towards the nearby residential areas. In this study, the blasting effects from Quarry A and B has been assessed based on constant location of the residential areas (Taman Pulai Hijauan and Taman Bandar Baru Kangkar Pulai, respectively) using the empirical formulations only. The blasting effects are highly dependent on the maximum instantaneous charge in blast holes (Q) which are dependent on parameters like number of blast holes, charge per column, Powder Factor and number of blast per delay. This study was able to show that with an increase of the independent variables, the Q value rises significantly. The average Q value from Quarry A (181.07 kg) was slightly higher than Quarry B (180.22 kg). The correlations made for each quarry showed that Quarry A had a better regression line with lower standard error due to the high number of blast data obtained during the monitoring period of about 1 year and 8 months. Meanwhile, the impact assessments showed higher PPV (Peak Particle Velocity) value at higher Q holding blast holes in Quarry A compared to Quarry B and decreases with increasing distance. The similar relationship was observed for the air blast assessments. Yet, all of the blasts produced are relatively within safe limits which are less than 5 mm/s Mineral & Geosciences Department (JMG) and less than 125 dBL United States Bureau of Mining (USBM). Thus, extra precaution can be taken by estimating the suitable Q value such as A (97.66 kg) and B (271.68 to 495.01 kg) to maintain safe blasting operations and prevent damages to the nearby residential areas.

The nature of groundwater recharge along the mountain front (MF) and riparian zone (RZ) was discerned by multiple tools involving rain/water level relationship, geophysical of subsurface, seasonal hydrochemistry and environmental isotopic signatures. The proposed study has been carried out in Courtallam Hills, the north-western part of Tirunelveli District, South India. The study area is a hilly terrain with narrow valleys endowed with steep slopes. The relationship between water-level fluctuation and precipitation were evaluated by observing daily water level in 8-h interval at three piezometer zones and regular rainfall data. It was inferred that the RZ played a role in storage zone and gets recharged from mountain block (MB) and lateral flow. The seasonal geochemistry of the groundwater was studied to determine the sources of recharge in MF and RZ. Geostatistical treatment of factor analysis revealed that weathering was the dominant recharge process along the foothill. The geophysical studies reveal good quality of groundwater observed in the northern part along with low conductance and high resistivity. The increased level of groundwater conductivity and lower resistivity was noted in southern part of the study area due to the irrigation activities. The isotopic tracers range from − 2.5 to − 12.6‰ for δ18O and from − 91.2 to − 15.5‰ for δ2H. Moreover, the groundwater recharge was evaluated by source of rainfall moisture. High-altitude recharge from MB along the MF was clearly indicated by depleted isotopic content of the water samples. It was also supported by hydrogeochemical and statistical evidences, showing that rainfall over both MB and MF zones provided the recharge to foothill aquifers, while the RZ zone was mainly recharged by local precipitation with less contribution from regional flows.

Glacier-wide mass balances and runoffs are reconstructed over 1969-2016 for Chhota Shigri Glacier catchment (India) applying a glacio-hydrological model. The model is forced using in-situ daily air-temperature and precipitation records from the meteorological stations at Bhuntar Observatory (1092 m a.s.l.), glacier base camp (3850 m a.s.l.) and glacier side moraine (4863 m a.s.l.). The modelled mean annual mass balance is -0.30 +/- 0.36m w.e.a(-1) (meter water equivalent per year), while the mean catchment-wide runoff is 1.56 +/- 0.23 m w.e.a(-1) over 1969-2016. Three periods are distinguished in the reconstructed mass balance and runoff series. Periods I (1969-1985) and III (2001-2016) show glacier mass wastage at rates of -0.36 and - 0.50 m w.e.a(-1), respectively, corresponding to catchment-wide runoffs of 1.51 and 1.65 m w.e.a(-1), respectively. Conversely, period II (1986-2000) exhibits steady-state conditions with average mass balances of -0.01 m w.e.a(-1), and corresponding runoff of 1.52m w.e.a(-1). The reduced ice melt (0.20m w.e.a(-1)) over period II, in agreement with steady-state conditions, is compensated by the increased snow melt (1.03 m w.e.a(-1)), providing almost similar catchment-wide runoffs for period I and II. The increased runoff after 2000 is mainly governed by increased ice melt (0.32m w.e.a(-1)) over period III. Snow accumulation in winter and summer seasons together control the glacier-wide mass balances as well as catchment-wide runoffs. Snow melt contributes the maximum to the total mean annual runoff with 63% share while glacier melt and rain contribute 17% and 20% respectively over the whole period.

Groundwater samples via tubewells were collected from the district Saharanpur, Uttar Pradesh (India). The study aimed to analyse groundwater quality and potential sources of trace metal contamination using the multivariate statistical tool, and the level of contamination by applying contamination index (Cd) and heavy metal pollution index (HPI). The groundwater was found to be enriched with Fe and contaminated with the trace and toxic elements like Al, As, B, Cu, Mn and Pb having mean values of 2786, 152, 9, 1033, 107, 199 and 15 µL respectively. Arsenic exceeded the WHO (2011) guidelines and BIS (2012) standard (10 µg/L) for 30% of the groundwater samples. For B, 46% of the samples were found having concentration higher than BIS (2012) permissible limit (1000 µg/L) and 3% to WHO (2011) guideline values (2400 µL). Lead level exceeded the BIS (2012) standard value and WHO (2011) guideline value in 46% of the samples. Multivariate analysis identified three factors responsible for data composition explaining 81% of the total variance in groundwater samples. Factor analysis (PCA and CA) allowed grouping of parameters according to the common features; Fe, Mn and Pb were associated with PC1 and controlled by the mixed origin such as geogenic sources as well as anthropogenic activities. Boron and Cu (PC2) were controlled by anthropogenic activities while As (PC3) was derived from the geogenic sources. The northern part of study area has higher Pb and Mn concentration than the southern part associated with small industrial activities. Degree of contamination and heavy metal pollution index supported the results and higher contamination was found to be in the vicinity of industrial setups. The overall quality (estimated using HPI values) of groundwater in the northern area is poor, and may cause potential health risk from the analyzed tubewells to the local population if the water is consumed for longer time.

This paper reports changes in different glaciers of Bhaga basin located in western Himalaya, from 1979 to 2017. Glacier boundaries were delineated through semi-automated approach using Landsat sate...

Long-term data (2003–2015) on meltwater chemistry, mass balance and discharge of a benchmark glacier (Chhota Shigri Glacier, India) were studied to determine any association between these variables...

COVID-19 positive patients can egest live SARS-CoV-2 virus and viral genome fragments through faecal matter and urine, raising concerns about viral transmission through faecal-oral route and/or contaminated aerosolized water. These worries are heightened in many low and middle income nations, where raw sewage is often dumped into surface waterways and open defecation betide. In this manuscript, we attempt to discern the presence of SARS-CoV-2 genetic material (ORF-1ab, N and S genes) in two urban cities of India viz., Ahmedabad, in western India with several WWTPs; and Guwahati in the north-eastern part of the country with no such treatment plants. The study was carried out to establish applicability of WBE for COVID-19 surveillance as a potential tool for public health monitoring at the community level. 25.8% and 20% of the surface water samples had detectable SARS-CoV-2 RNA load in Ahmedabad and Guwahati, respectively. The high concentration of gene (ORF-1ab - 800 copies/L for Sabarmati river, Ahmedabad and S-gene - 565 copies/L for Bharalu urban river, Guwahati) found in natural waters indicates WWTPs do not always completely remove the genetic material of the virus. The study shows the applicability of WBE surveillance of COVID-19 in cities with low sanitation as well as in rural areas. The method used in this study cannot detect the live viruses, hence further research is required to evaluate the transmission implication of COVID-19 via ambient water, if any. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/21258829v3_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@19a51dborg.highwire.dtl.DTLVardef@743707org.highwire.dtl.DTLVardef@1c8b608org.highwire.dtl.DTLVardef@26cd43_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LINatural urban waters show the presence of SARS-CoV-2 RNA. C_LIO_LILake water receiving runoff containing SARS-CoV-2 genes reflected positive sign early C_LIO_LIViral RNA in surface water reflects incomplete removal of gene fragments in WWTPs. C_LIO_LIResidence time and fate owing to viral RNA in natural waters needs further research. C_LI

COVID-19 positive patients can egest live SARS-CoV-2 virus and viral genome fragments through faecal matter and urine, raising concerns about viral transmission through the faecal-oral route and/or contaminated aerosolized water. These concerns are amplified in many low- and middle-income countries, where raw sewage is often discharged into surface waterways and open defecation is common. Nonetheless, there has been no evidence of COVID-19 transmission via ambient urban water, and the virus viability in such aquatic matrices is believed to be minimal and not a matter of concern. In this manuscript, we attempt to discern the presence of SARS-CoV-2 genetic material (ORF-1ab, N and S genes) in the urban water (lakes, rivers, and drains) of the two Indian cities viz., Ahmedabad (AMD), in western India with 9 wastewater treatment plants (WWTPs) and Guwahati (GHY), in the north-east of the country with no such treatment facilities. The present study was carried out to establish the applicability of environmental water surveillance (E-wat-Surveillance) of COVID-19 as a potential tool for public health monitoring at the community level. 25.8% and 20% of the urban water samples had detectable SARS-CoV-2 RNA load in AMD and GHY, respectively. N-gene > S-gene > ORF-1ab-gene were readily detected in the surface water of AMD, whereas no such observable trend was noticed in the case of GHY. The high concentrations of SARS-CoV-2 genes (e.g., ORF-1ab; 800 copies/L for Sabarmati River, AMD and S-gene; 565 copies/L for Bharalu urban river, GHY) found in urban waters suggest that WWTPs do not always completely remove the virus genetic material and that E-wat-Surveillance of COVID-19 in cities/rural areas with poor sanitation is possible., Graphical abstract Image 1

This chapter reviews blue carbon stock of different mangrove ecosystems across globe through published literature. It also tries to evaluate its dynamics with different land use and land cover changes. The study reveals that mangroves have a high potential to store carbon compared to other terrestrial and coastal ecosystems. Indian Sundarbans stores 160–360 tC/ha based on salinity and vegetation types. The emission of carbon from the degradation of above-ground biomass in Indian Sundarbans was 427,242 tons between 1975 and 2013. Deforestation of Bangladesh Sundarbans causes loss of 8500, 1800, 670, 290, 133, and 104 hectares of mangroves along Chakaria, Naf river estuary and offshore Island, Naf river, Maiskhali Island, Jaliardwip Island, and Matabar Island, respectively. There is a rapid decline in plantations (-58.2%), mangrove swamps (-49.3%), and mangrove forests (-21.3%) during 2000–2017 due to their conversion to aquaculture farms in Bangladesh. Along Indian coastlines, Andhra Pradesh is the most affected area and shows significant decrease in paddy fields due to their conversion to aquaculture farms between 1980–81 and 2000–01. It also indicates massive increase in shrimp production from 1990-2017. Bangladesh shows a dramatic rise in shrimp production from 56,569 to 75,274 tons from 2010-2011 to 2014-2015. Destruction of mangroves releases carbon dioxide in the atmosphere and can reverse mangroves’ role from a sink to source. Since aquaculture farming helps in high revenue generation but negatively affects the coastal ecosystem, it is essential to maintain a balance. Hence Integrated Multi-Trophic Aquaculture (IMTA) has been introduced along with mangrove forest restoration, and REDD+.

A comparative assessment of dissolved oxygen (DO) and biochemical oxygen demand (BOD) of river Ganga during prelockdown and lockdown periods was made through analysis of data generated from real-time water quality motoring systems. The concentration data for DO and BOD are examined for (i) prelockdown period (March 15–21, 2020) and (ii) lockdown period (March 22–April 15, 2020). The analysis results show 3%–20% decrease in DO concentration. The slight decrease in DO observed at all locations during the first week after lockdown which may be due to the increased levels of suspended solids and turbidity in the river water because of heavy rains. DO during fourth week of lockdown has shown a decreased value as compared to the prelockdown period at most of the locations. However, in West Bengal the DO has increased in lockdown. BOD value ranged between 1.13 mg/L and 5.56 mg/L during lockdown period, more or less similar to prelockdown range of 1.37–5.58 mg/L. This chapter further discusses the cause of water quality changes during the period of lockdown as compare to prelockdown period.

Global pandemic of SARS-CoV-2 has infected more than 53 million people in more than 190 countries. The major transmission routes of most of the infectious viruses’ including SARS-CoV-2 remain aerosols and droplets. The source of which remains coughing, sneezing, urinary, and intestinal excretions. This book chapter focuses on the latter two sources of water and wastewater contamination with RNA of these contagious viruses. There has been studies regarding the presence of viral RNA of COVID-19 in wastewater in few of the countries like USA, Australia, Netherland, and India. This mainly happens due to the discharge of untreated wastewater from health care facilities and sewage treatment plants. Improper management of the waste has led to the contamination of surface water bodies. Fecal shedding of the virus is common in 50% of the infected individual, and urinal shedding in just around 5%. The former shedding is of the order of 103–105 copies/mL. The wastewater surveillance for SARS-CoV-2 RNA in wastewater gives the figure of 102–106 copies/L. The surveillance already known to track down many diseases, drugs in past has been a boon to the countries, where clinical testing is at a slow pace. Therefore, wastewater-based epidemiology is needed to have a better understanding of the water and wastewater surveillances, for prior detection of SARS-CoV-2 and other pathogens, sought to occur in future. The chapter deals with the occurrences, transport pathways, persistence, and removal of most of the reported infectious viruses in water and wastewater, with a special emphasize on SARS-CoV-2. Developing a proper framework and methodology containing environment and human health risk assessments will help the researchers and policyholders to look up for the alternative options. Even after a number of researches detecting the presence of SARS-CoV-2 in wastewater, there has been a limited knowledge in the potential role of water and wastewater in the transmission of these infectious viruses. A well summarized review would surely help in the assessment of the likely fate of most of these contagious human viruses.

Increased concern has recently emerged pertaining to the occurrence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in aquatic environment during the current coronavirus disease 2019 (COVID-19) pandemic. While infectious SARS-CoV-2 has yet to be identified in the aquatic environment, the virus potentially enters the wastewater stream from patient excretions and a precautionary approach dictates evaluating transmission pathways to ensure public health and safety. Although enveloped viruses have presumed low persistence in water and are generally susceptible to inactivation by environmental stressors, previously identified enveloped viruses persist in the aqueous environment from days to several weeks. Our analysis suggests that not only the surface water, but also groundwater, represent SARS-CoV-2 control points through possible leaching and infiltrations of effluents from health care facilities, sewage, and drainage water. Most fecally transmitted viruses are highly persistent in the aquatic environment, and therefore, the persistence of SARS-CoV-2 in water is essential to inform its fate in water, wastewater and groundwater and subsequent human exposure.

Arsenic and uranium in the aquatic environment are recognized as a major catastrophic problem worldwide and have natural as well as human-made sources such as mining, industry and agriculture. The severity of this problem is further accelerated by in-situ physio-chemical factors in the fluvial environment which enhances the concentration of arsenic and uranium in groundwater that feeds millions of people in Central Gangetic Plain in India. This study aims to establish a better understanding of the processes responsible for the co-occurrence of arsenic and uranium along with the factors controlling their solubility and mobility in the groundwater of central Gangetic plain. This study is an attempt to bring out the (a) the spatial distribution pattern of arsenic and uranium, (b) insight into the hydrogeochemical characteristics of aquifers that are controlling their co-occurrence and provides (c) information of their source which are validated by statistical tools. Silicate weathering controls U mobilization and distribution whereas carbonate dissolution and ion exchange process controls As in groundwater. The land use and land cover pattern of the North-eastern (NE) part of the study area is agriculture dominated and is composed of Holocene older alluvium. However, the South and South-western areas which are closer to the river are formed by the deposition of river born newer alluvial. Newer alluvium in the SW part has unoxidized organic-rich clay that enhances arsenic mobilization by reductive dissolution of Fe-oxyhydroxide. In the NE region, the abundance of fertilizers in the subsurface oxidizing environment augments the solubility and mobility of uranium.

Two atmospheric circulation patterns, the Indian Summer Monsoon (ISM) and mid-latitude Westerlies control precipitation and thus glacier variability in the Himalaya. However, the role of the ISM and westerlies in controlling climate and thus past glacier variability in the Himalaya is poorly understood because of the paucity of the ice core records. In this article, we present a new Holocene paleorecord disentangling the presence of the ISM and mid-latitude westerlies and their effect on glacier fluctuations during the Holocene. Our new record is based on high-resolution multi-proxy analyses (δ18Oporewater, deuterium-excess, grain size analysis, permeability, and environmental magnetism) of lake sediments retrieved from Chandratal Lake, Western Himalaya. Our study provides new evidence that improves the current understanding of the forcing factor behind glacier advances and retreat in the Western Himalaya and identifies the 8.2 ka cold event using the aforementioned proxies. The results indicate that the ISM dominated precipitation ~ 21% of the time, whereas the mid-latitude westerlies dominated precipitation ~ 79% of the time during the last 11 ka cal BP. This is the first study that portrays the moisture sources by using the above proxies from the Himalayan region as an alternative of ice core records.

Integrated constructed wetland into activated sludge process has a potential in improving treated wastewater with high organic loading. However, biological activities on those processes will generate microbial by-products from substrate metabolism and cell lysis. The presence of those compounds in effluent of wastewater treatment causes problems in source water. This study combines fluorescence excitation emission matrices (FEEM) with high-performance size exclusion chromatography with fluorescence detector (HPSEC-FLD) to characterize molecular weight–based fluorescent of organic matter and its removal in combination of constructed wetland with activated sludge process. The results show that three components of fluorescence organic: fulvic acid–like (Ex/Em 250/440 nm), SMP-like (Ex/Em 280/350 nm), humic acid–like (Ex/Em 340/420 nm), have been identified in all samples by the FEEM. Further, the HPSEC-FLD, which was set up based on chosen fluorescence wavelength, revealed two different apparent molecular weight (AMW) fractions: high molecular weight (HMW)/biopolymer (50,000 Da) and medium molecular weight (MMW)/humic substance–like (3000–650 Da). Peak-fitting determines that the area of MMW is higher than the area of HMW of all fluorescence organic components, and the area of HMW of fluorescence fulvic acid–like is comparable with the area of SMP-like, and no HMW of humic acid–like detected. Humic acid–like and fulvic acid–like were removed during treatment, while metabolite by-product were released as shown by increasing fluorescence SMP-like and TOC concentration. This method gives new insight to characterize organic matter for assessing effluent of wastewater quality and determining the appropriate water treatment.

The hydrogeochemical study on glacial meltwater gives important information about the quality of meltwater and weathering processes controlling dissolved ions chemistry in the glacierized area. Anionic abundance in the Manimahesh Glacier meltwater shows a trend of HCO3− > SO42− > Cl− = NO3−, whereas cationic abundance in the meltwater shows a trend of Ca2+ > Mg2+ > K+ > Na+. On the basis of high equivalent ratios of (Ca + Mg) versus (Na + K) and (Ca + Mg) versus TZ+ (total cations) and low equivalent ratio of (Na + K) versus TZ+, carbonate-type weathering has been identified as a major hydrogeochemical process regulating solute chemistry of the Manimahesh Glacier meltwater followed by silicate weathering. About 80% of bicarbonate in the meltwater of investigation area was mainly generated from carbonate weathering, whereas 20% of bicarbonate was produced from silicate weathering. The result of statistical methods (correlation, principal component and cluster analysis) shows that meltwater quality of the Manimahesh Glacier is mainly governed by carbonate and silicate-type weathering, oxidation of pyrite, dissolution of sulphate minerals and atmospheric input. The average value of suspended sediment concentration (SSC) in the glacier meltwater was calculated to be 46 mg/l and 63 mg/l during the month of June and July 2014, respectively, showing higher concentration of SSC during the month of July (peak-flow period) followed by June (low-flow period).

Geochemical influences on arsenic (As) and other solutes along with regional groundwater flow path were inferred in parts of the central Gangetic Basin. The median concentration of As in groundwater was higher (0.046 mg/L) in Piedmont and (0.006 mg/L) in younger alluvium while very low (0.002 mg/L) in older alluvium. The median As concentrations in core sediments of Piedmont, older alluvium and younger alluvium were observed as 5.12, 11.2 and 11.6 mg/kg, respectively. Approximately 70% of the samples fell in As(OH)3 or As(III) field and 30% samples fell in HAsO 4 2 − or field of As(V) in Eh–pH plots. In contrast ∼60% of the samples fell in the FeOOH field and 40% in Fe(II) field in the Eh–pH plots. Cation exchange in Piedmont and older alluvium, while carbonate dissolution in younger alluvium controlling the groundwater major solute chemistry. The predictive outputs of inverse modelling congruence with predicted/ hypothetical groundwater flow directions. It was observed that geomorphology and the groundwater flow path also have substantial influence on solute chemistry and As distribution. Redox controlled adsorption/ desorption of Fe–Mn (oxyhydr)oxide was suggested as the probable mechanisms for As liberation in Piedmont, while multiple processes control the mobilization and presence of As in the younger alluvium. Study also concluded that the shallow aquifers of Piedmont and younger alluvium are contaminated with As while aquifers of older alluvium having low As contamination, could be the safe alternate for the residing people.