Search

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.

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.

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.

Groundwater chemistry of mining region of East Singhbhum district having complex contaminant sources were investigated based on heavy metals loads and other hydrochemical constituents. This study aimed to identify the degree of heavy metals exposure and their potential health risk to local population. The results of hydrochemical analysis showed that Na+, K+, and Ca2+ ions are the dominant cations in the groundwater, while HCO3−, F− and Cl− ions dominate the anionic part of the groundwater. The weathering process was considered the dominant factor to determine the major ionic composition in the study area. Compositional analysis for heavy metal has identified that groundwater of the study area is contaminated by Cd, Pb and Cr elements. Source of these metals have been identified as an anthropogenic inputs from mining activities and mineral processing units. Health risk analysis of individual heavy metal for chronic daily intake (CDI) and hazard quotient (HQ) was found in the order of Cr > As > Cd > Pb which is indicating high health risk for the population. In addition, Hazard Index (HI) analysis for heavy metals was found significantly high (>1) which is considered as a threat for human population because they have the tendency to accumulate in the body and cause variety of diseases like kidney problem, dysfunction of liver and renal cortex as well as cancer.

Spatiotemporal variations of dissolved nutrients were studied along Gautami-Godavari mangrove ecosystem to delineate their sources and fate. Average values of nitrate (NO3-), dissolved silica (DSi) and phosphate (PO43-) is 2.09 mg/l, 12.7 mg/l and 0.16 mg/l in wet season and 0.47 mg/l, 6.96 mg/l and 0.29 mg/l in dry season respectively. In wet season river discharge has significant influence on NO3- and DSi. In dry season, NO3- and PO43- are controlled by groundwater discharge, benthic exchange and various in situ processes owing to sediment redox condition. Mixing model shows net addition of phosphate in Coringa mangroves (95%) and Lower estuary (13%) and net removal of nitrate (24.79%) in Coringa mangrove and in estuary (58.9%). Thus present mangrove acts as net source for phosphate and net sink for nitrate and DSi. Nutrient ratio shows seasonal switching between potential Phosphorus and Nitrogen limitation in wet and dry season respectively.

Comparative study of trace metals distribution in the surface sediment of Sundarban mangrove ecosystem in India and Bangladesh is one of the primary baseline study done so far. Trace metal distribution assessment covering lower salinity zone to higher salinity zone was done along Matla River (tidal river) in Indian side and freshwater zone to higher salinity zone along Passur River in Bangladesh side of Sundarban; representing anthropogenic influenced area, agricultural area, tourist site and pristine area. Trace metals distribution in the surface sediments of Sundarban mangrove ecosystem shows relatively higher value of trace metals, Co, Cr, Cu, Fe, Ni, Pb and Zn in Indian part when compared to Bangladesh. Enrichment factor shows the highest enrichment of Pb in both parts of Sundarban mangroves. Co, Cr, Cu, Pb and Zn show EF>1 indicates sediment contamination from anthropogenic activities. Cr, Ni and Pb were found to have moderate accumulation in geoaccumulation index with Fe showing high accumulation. Normalized data of trace metals shows 87.5% from Indian site and 80% of Bangladesh site as outlier, indicating anthropogenic influence. Out of total sampling site 50% of Indian and 40% of Bangladesh site show trace metal values enriched more than predicted value of trace metals indicating Indian part have more polluted sites than Bangladesh side of Sundarban, which is also confirmed by enrichment factor, I-geo and normalization values in both the sides.

The present study aims at the assessment of environmental quality of the most polluted stretch of river Yamuna along the megacity of Delhi. The study was conducted in order to examine toxicity and health hazards associated with persistent pollutants present in the fluvial ecosystem. Eighty four sediment and 56 vegetable samples from same locations were collected from the Delhi segment of river Yamuna flood plain in order to examine 20 organochlorine pesticides (OCPs) and 9 heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn). Both the organic and inorganic groups of persistent toxic substances were monitored and analysed for the extent of eco-toxicological as well as dietary health risks posed to the local population. Eco-toxicological assessment was done based on sediment quality guidelines, enrichment factor, geo-accumulation index, degree of contamination and Pollution Load Index. The dietary-risk was assessed with the help of translocation factors (TF) of these pollutants in vegetables. Carcinogenic and non-carcinogenic health risks from consumption of vegetables were also investigated. The level of concern for heavy metals was greater than that of OCPs as per the sediment quality guidelines. DDT, Cd, Pb and Zn had maximum concentrations corresponding to level 3 of concern, while Cr and Ni reached up to the highest i.e., 4th level of concern. Sediment samples were found to be enriched and contaminated significantly with Cd and moderately with Pb, as represented respectively by enrichment factors and contamination factors (CF). CF for metals lied in order Zn > Cd > Cr Ni > Pb Cu. Pollution load index was highest at the location lying on the exit point of Yamuna in Delhi. TF values greater than 1 were observed in majority of samples analysed for Ni, Cr, Cu and Zn. Spinach topped among vegetables in terms of metal contamination. Cd, Ni and Pb accumulated more in the roots, as against Mn, Zn, Cu and Cr which had higher accumulation in the shoots. Translocation factors were substantially high in vegetables for most of the OCPs, clearly indicating bioaccumulation and potential health risk to the consumers. Health risk to humans was assessed for non-carcinogenic and carcinogenic potentials from ingestion of vegetables. Hazard Quotient (HQ) > 1 due to radish (roots and leaves) and cauliflower consumption in children indicated non-carcinogenic risk. Hazard Index (HI) beyond 1 for all the vegetables (except onion leaves) confirmed substantial cumulative risk. Lifetime cancer risk (LCR) revealed moderate (spinach, radish, beet root and cauliflower) to low (all the others) levels of carcinogenic risk to humans. Cancer risks from γ-HCH, β- HCH, Hept, Hept Ep, Ald, p,p’-DDT, and Cr exposure through the food chain could be well established.

The Sutlej River basin of the western Himalaya (study area), owing to its unique geographical disposition, receives precipitation from both the Indian summer monsoon (ISM) and the Westerlies. The characteristic timing and intensity of the ISM and Westerlies, leaves a distinct footprint on the sediment load of the River. Analysis with the last forty years data, shows an increasing trend for temperature. While for precipitation during the same period, the Spiti watershed on the west has highest monthly accumulated precipitation with long term declining trend, in contrast to the other areas where an increasing trend has been observed. Thus, to probe the hydrological variability and the seasonal attributes, governed by the Westerlies and ISM in the study area, we analyzed precipitation, temperature, snow cover area (in % ), discharge, suspended sediment concentration (SSC) and suspended sediment load (SSL) for the period 2004 - 2008 . To accomplish the task, we used the available data of five hydrological stations located in the study area. Inter-annual shift in peak discharge during the monsoon period is controlled by the variation in precipitation, snow melt, glacier melt and temperature. Besides seasonal variability has been observed in generation of the sediments and its delivery to the river. Our analysis indicates, dominance of the Westerlies footprints in the hydrological parameters of the Spiti region, towards western part of the study area. While, it is observed that the hydrology of the Khab towards eastern part of the study area shows dominance of ISM. Further downstream, the hydrology of Nathpa station also shows dominance of ISM. It also emerged out that the snowmelt contribution to the River flow is mostly during the initial part, at the onset of the monsoon, while for rest and major part of the summer monsoon season, the River flow is augmented by the precipitation, glacial melt and some snow melt. We observed, that the SSC increases exponentially in response to increase in temperature and correlates positively with River discharge. The average daily SSL in the summer monsoon is many times more than that in the winter monsoon. The downstream decrease in steepness of the sediment rating curve is attributed to either a change in the River-sediment dynamics or on account of the anthropogenic forcing. The top 1 % of the extreme summer monsoon events (only 4 events) in our study area contribute up to 45 % of SSL to the total sediment load budget. It has also been observed that the River-sediment dynamics in the upstream catchments are more vulnerable and sensitive to the extreme events in comparison to the downstream catchments. The present study for the first time gives a holistic insight in to the complex dynamics of the hydrological processes operational in the study area. The research findings would be crucial for managing the water resources of the region and the linked water and food security.

An attempt has been made to study the subsurface groundwater discharge (SGD) in the coastal Cuddalore region of south east India. Measurement for Radon, water level, Electrical Conductivity (EC) and pH in surface water for a total of twenty hours by hourly interval has been attempted and further correlated with tidal values calculated by WX Tide 32 software. The SGD measurements were made by using a modified seepage meter. The study reveals a match with water level variation and tide with minor variation due to influx of surface water. Saline discharges, fresh groundwater discharges and surface water mixing processes were identified along the coast. Lower SGD (37.24–79.16 cm/day) was observed during fresh groundwater discharge.

The diverse habitat of the mangrove ecosystems all over the globe are under continuous threat of conversion for immediate and/or short-term economic benefits. Nonetheless, the emission of climatically relevant greenhouse gases increases with the disturbance of the mangrove sediment −this might undermine the credible reservoir of carbon within the sediment. This article attempts to estimate the environmental (carbon emission) and economic consequences of converting mangrove to cropland (especially rice paddy) based on field-scale study at three different sites (Khola, Gupti and Damra) within the Bhitarkanika mangrove for two consecutive years. The study suggests that the cumulative methane (CH4) emission was significantly higher from the rice paddy (211.3 kg ha−1) compared to the mangrove sediment (50.8 kg ha−1), while the average nitrous oxide (N2O) emission was significantly higher from the later (2.1 kg ha−1). Multivariate statistical analysis suggests that the land use was the prime controlling factor for variation in CH4 and N2O emission. Total carbon equivalent emission (CEETOT) from the rice paddy was significantly higher than mangrove during the study period. The study suggests that the economic value of the mangrove ecosystem was several folds higher than that of the rice paddy. The CEETOT of the Bhitarkanika mangrove has increased approximately 212 Gg over last few decades due to the conversion of the mangrove area to the rice paddy. Such studies are imperative in developing effective regional climate change adaptation strategies. The study advocates urgent need to educate and aware people about the benefits of the mangrove compared to the cropland.

This paper presents a review of Late Quaternary climatic changes and glacier variability in the Himalaya and East Africa, focusing on the role of Indian Summer Monsoon (ISM), East African monsoon, and Westerlies monsoons. Multi-proxy studies which are based on five different archives (lakes, peat bogs, speleothems, marine sediments, and ice cores) including sixty-six records from India and nearby regions, particularly in the Himalaya and in addition to six archives from the equatorial Eastern part of Africa encompasses with high-resolution published and unpublished records for the last 50 ka BP. The proxy data is discussed towards REMO-ESM model Coupled Model Intercomprasion Project phase 5 (CMIP5 Project) results. Our results indicate that both Western Himalaya and East Africa had undergone mega-droughts from ~17.0–15.0 ka BP, and precipitation had increased during the Early Holocene (10.0–7.0 Ka BP) during the time span when the Westerlies dominated regions. The model results suggest that the Westerlies monsoon has significantly contributed to the Northwestern Himalaya and somewhat to a lesser degree to the Western Himalaya and lower solar insolation in the winters did support the glacier advance during the LGM. The time series from the proxy data are compared with glacier fluctuations in different valleys to understand the response of the aforementioned monsoon system including other forcing factors which drive these variabilities. The review results indicate that the Westerlies was the main driver of the climate and glacier fluctuations in Northwestern Himalaya during the Late Quaternary. The Early and Late Holocene glacier fluctuation was mainly controlled by Westerlies precipitation in Northwestern Himalaya and the ISM controlled the glacier fluctuations in the Western Himalaya during Late Quaternary.

Concentrations of inorganic forms [arsenite, As(III) and arsenate, As(V) of arsenic (As) present in groundwater, agricultural soils and subsurface sediments located in the middle Gangetic plain of Bihar, India were determined. Approximately 73% of the groundwater samples (n = 19) show As(III) as the dominant species while 27% reveals As(V) was the dominant species. The concentration of As(III) in agricultural soil samples varies from not detectable to 40 μg/kg and As(V) was observed as the major species (ranging from 1050 to 6835 μg/kg) while the total As concentration varied from 3528 to 14,690 μg/kg. Total extracted concentration of As was higher in the subsurface sediments (range 9119–20,056 μg/kg in Methrapur and 4788–19,681 μg/kg in Harail Chapar) than the agricultural soil, indicating the subsurface sediment as a source of As. Results of X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) revealed the presence of hematite and goethite throughout the vertical section below while magnetite was observed only in the upper oxidized layer at Methrapur and Harail Chapar. Alteration of Fe-oxides and presence of fibrous goethite indicating presence of diagenetic sediment. Siderite plays a crucial role as sinks to the As in subsurface sediments. The study also concluded that decomposition of organic matter present in dark and grey sections promote the redox conditions and trigger mobilization of As into groundwater.

The problem of salinization in the Delhi aquifer, that currently exhibits rapid landuse change, is conspicuous and severe. Salinization may be caused either by a single process, or a combination of different processes; including anthropogenic related activities, water logging and evaporative concentration of salts, influx of natural saline water, upconing of brines from the deeper parts of the aquifer, and airborne salts depositions. However, there is a lack of well-proven theory that can explain the salinity of the order of 5000 μS/cm in the deeper aquifers of Delhi. This work identifies inconclusiveness in the previous theories of marine ingression, evaporation enrichment and subsequent leaching of salt. Further, the study depicts a conceptual understanding of the origin of salinity in groundwater based on the integrated investigations of groundwater quality, age and stable isotopic fingerprinting as well as GIS based mapping of geomorphic features. In order to explain the salinity observed in groundwater of NCT Delhi, a phenomenological scenario is illustrated and supported by additional evidences. The highest average EC value was for the shallow aquifer and is strongly symptomatic of anthropogenic influences on groundwater chemistry. Piper diagram showed heterogeneous water type and sufficient recharge/mixing of the groundwater from different aquifers. The relationship between Cl − /Br − ratios vs. Cl − indicated dissolution of salt deposits containing evaporative fraction present in the unsaturated zones or in the sediments of deeper aquifers and leaching of evaporative minerals from dunes of the adjacent Thar Desert. Cl − /SO 4 2− ratio suggested the presence of connate seawater, halite dissolution and concentration of dissolved salts by evapo-transpiration of river water diverted for irrigation. The results show, that the closed inland marine conditions developed and buried with the active sedimentation in the geological past in this region, and further intensive exploitation of groundwater, and enhanced evaporation have together resulted in saline playa condition in some part of the region. The scenario was further verified by matching the required condition for the formation of salt pan or playa with the existing geo-morphological conditions of the area. Isotopic results indicate that salinity flushing is possible and proceeds in the areas of freshwater recharge.

Study region Arsenic enriched groundwater regime within low-industrialized Brahmaputra floodplains in Assam, NE India. Study focus We examined the origin, distribution and processes of As release by investigating the salient groundwater chemistry and subsurface sedimentological characteristics. Besides collection of groundwater samples from domestic and public water supply wells, sediment samples from boreholes were investigated for textural and colour linkages. New hydrological insights for the region Arsenic concentrations above the WHO guideline value of 10 μg/L were present in 33 wells and above the previous Indian national drinking standard of 50 μg/L were present in 15 wells. The green-olive colour sediments were more likely to yield As-enriched groundwater. The supersaturation of groundwater with respect to Fe(II) minerals, such as siderite and vivianite, explained the poor correlation between dissolved As and Fe. The result reinforced the phenomenon of reductive dissolution of Fe(III) oxyhydroxides releasing As to groundwater. This study throws light on the processes and mechanisms involved with As release in groundwater. The homogenous floodplain terrain makes the hydrological As imprint unambiguous and the hydrogeological signatures untarnished. Considering the absence of anthropogenic sources in the study area, the conclusions on the nature and causes for As release to groundwater looked dependable although the final contamination at specific subsurface sites would be influenced by advection–dispersion of groundwater flow accompanied by retardation, ion exchange, surface complexation and possible biodegradation.

The nature and distribution of lipid biomarkers (n-alkanes, n-alkanols, sterols and triterpenols) were investigated in five dated sediment cores from the Pichavaram mangrove–estuarine complex in order to: 1) identify the organic matter (OM) sources and its preservation and 2) trace recent changes associated with coastal processes and anthropogenic activities. The mangrove sediment extracts have higher biomarker concentration (22.6 ± 13.3 μg/g dry weight) than the estuarine extracts (6.42 ± 4.92 μg/g dry weight). Triterpenols are dominant biomarkers in both estuarine and mangrove sediments, and constitute > 50% of the total lipid extracts. The presence of n-alkanols (n-C26,28,30) and abundance of phytosterols (stigmasterol and β-sitosterol) and triterpenols (taraxerol, β-amyrin, germanicol, and lupeol) indicate that mangrove vegetation is the primary source of sedimentary OM. The high abundance and unimodal distribution of the long-chain n-alkanes (mainly n-C25,27,29), and high values of Terrestrial Aquatic Ratio (TAR 2.4 to 41) and Carbon Preference Index (CPI > 8) indicate dominance (and better preservation) of higher plant derived immature OM in mangrove sediments. In contrast, the weak dominance of high molecular weight n-alkanes, low CPI (0.75 to 0.90) and TAR (1.9 to 5.7) values, and the presence of high C27 and C28 sterols indicate that phytoplankton/algal derived OM is more pronounced in estuarine sediments. Diagenetic changes in sedimentary OM indicate that some of the lipid fractions are reactive, and as a result, they degrade more rapidly than bulk OM. These compounds follow first order decay kinetics, and concur with the downcore diagenetic changes in coastal areas. Resistance to degradation among the different lipid classes show the trend: n-alkane > sterol > triterpenol > n-alkanol. Finally, the study indicates that less freshwater discharge from the Coleroon River is causing a gradual change in mangrove vegetation. There is less input of OM derived from mangrove vegetation into recent sediments. Biomarker trends also indicate that less salt tolerant Rhizophora spp. are gradually replaced by more salt tolerant vegetation consisting of Sueda spp. and Aviccenia spp.

We have studied the seasonal and tidal variation of methane (CH 4 ) and nitrous oxide (N 2 O) emission from the intertidal sediment of Bhitarkanika mangrove in the east coast of India. Seasonal variability study was conducted at five sites (three replicate of each site) inside the core area of the national park during three different seasons (summer, monsoon and winter) whereas tidal variation was studied at three different sites outside the core area during monsoon and winter season. Both CH 4 and N 2 O emission from the intertidal sediment were significantly higher under the low tide condition during the winter season. During the study period CH 4 emission from five different sites was ranged between 0.08 and 2.30 mg m −2 h −1 and the N 2 O emission was ranged between 9.0 and 187.58 μg m −2 h −1 . Average seasonal N 2 O emission (μg m −2 h −1 ) from five different sites followed the order: winter (115.60 ± 21.90) > summer (45.29 ± 7.78) > monsoon (16.98 ± 2.54). CH 4 and N 2 O emission was also recorded significantly higher during the winter season over the tidal cycle of three sampling locations. The CH 4 emission was negatively correlated with sediment salinity (r = −0.91, P 4 –2 (r = −0.89, P 2 O emission was positively correlated with sediment salinity (r = 0.48) and NO 3 − –N (r = 0.88, P 2 O emission with the sediment NO 3 − –N indicates possible influence of upstream anthropogenic activities on N 2 O emission from the mangrove sediment. In general, methylamine utilizing methanogen and denitrifying bacterial population was significantly higher during winter season in the mangrove sediment. The study concludes that the CH 4 and N 2 O emission from the sediment at different sites during different seasons are influenced by allochthonous carbon and nitrogenous materials.

A systematic study on the seasonal variation of major cations and anions was carried out to understand the source of dissolved ions as well as the geochemical weathering processes controlling the meltwater chemistry of Gangotri glacier. Calcium and magnesium are the major cations while sulphate is the dominant anion followed by bicarbonate. The high ratios of (Ca + Mg)/(Na + K), Ca/Na, Mg/Na, HCO3/Na and low ratio of (Na + K)/TZ+ for pre-monsoon, monsoon and post-monsoon seasons indicate the dominance of carbonate weathering, which is a major source of the dissolved ions in the meltwater of Gangotri glacier followed by silicate weathering. High equivalent ratios of Na/Cl and K/Cl as compared to sea water indicate relatively lesser contribution from atmospheric input to the chemical composition of meltwater. Correlation matrix and factor analysis were used to identify various factors controlling the major ion chemistry. Marked seasonal and diurnal variations were observed in the dissolved ions and suspended sediment concentration. Daily mean suspended sediment concentration for pre-monsoon, monsoon and post-monsoon was observed as 1719, 3281 and 445 mgl−1, respectively. Highest suspended sediment load was observed in monsoon season followed by pre-monsoon and post-monsoon seasons. The cation denudation rates of Gangotri glacier meltwater were calculated to be 42.2, 46.5 and 15.9 t km−2 y−1 for pre-monsoon (June only), monsoon and post-monsoon respectively. These values are higher than that of other Himalayan glaciers. Whereas physical weathering rate of the Gangotri glacier catchment was observed to be 7056, 15,344 and 588 t km−2 y−1 for pre-monsoon (June only), monsoon and post-monsoon respectively, much higher than the Indian and world averages of river.

Despite its limited aerial extent, the National Capital Territory (NCT) Delhi, India, has diversified geological and topographical setup. A geochemical assessment of prevailing conditions of aquifer underlying the NCT was attempted and further classified into different hydrogeochemical zones on the basis of statistical and analyses and its correlation with land use, geological and climatic setting. Mineral phase study and isotopic analyses were used for the verification of performed clustering. Saturation indices (SI) calculated using the geochemical modelling code PHREEQC were used to distinguish the characteristics of four zones, as saturation states of the water does not change abruptly. Four different hydrogeochemical zones were statistically identified in the area: (1) intermediate (land-use-change-impacted) recharge zone, (2) discharge (agriculture-impacted) zone, (3) recharge (ridge) zone, and (4) recharge floodplain (untreated-discharge-impacted) zone. The distinctiveness of hydro-geochemical zones was further verified using stable isotopic (H-2 and O-18) signature of these waters. GIS-based flow regime in association with long-term geochemical evidences implied that these zones are being affected by different problems; thus, it necessitates separate environmental measures for their management and conservation. The study suggested that in a diversified urban setup where the complex interactions between anthropogenic activities and normal geochemical processes are functioning, hydrogeochmical zoning based on the integration of various techniques could be the first step towards sketching out the groundwater management plan.

In order to identify the hydrogeochemical process controlling the quality of groundwater, an extensive study was carried out in Imphal and Thoubal district of Manipur, India. The objectives of the studies were to delineate the spatial and temporal variability in groundwater quality and understand its suitability for human uses. In the study area groundwater samples from 45 location have been collected during the pre-monsoon, monsoon and post-monsoon seasons and analyzed for the major ions such as Ca2+, Mg2+, Na+, K+, HCO 3 - , Cl−, SO 4 2 - , NO 3 - , PO 4 3 - , F−, Fe and silica. The water quality of both districts was good for domestic and agricultural uses except for few samples. These saline samples were localized and were due to the inherent lithology of the study area. Three major hydrochemical facies (Ca–HCO3 type, mixed Ca–Na–HCO3 and Ca–Mg–Cl types in Imphal district and Ca–HCO3, mixed Ca–Mg–Cl and Ca–Cl type in Thoubal district) were identified. The mineral stability diagrams indicated that the groundwater is in equilibrium with kaolinite and Ca-montmorillonite whereas Gibbs plot showed that the chemical composition of ground water in both districts is controlled by the natural weathering processes irrespective of seasons. Among the chemical weathering processes, silicate weathering was dominant. The results were supported by Wilcox plot and USSL diagrams. The study reflected the overall suitability of groundwater for anthropogenic use.

The Pichavaram mangrove ecosystem is located between the Vellar and Coleroon Estuaries in south-eastern India. To document the spatial-depth-based variabilities in organic matter (OM) input and cycling, five sediment cores were collected. A comparative study was carried out of grain-size composition, pore water salinity, dissolved organic C (DOC), loss-on-ignition (LOI), elemental ratios (C/N and H/C), pigments (Chl a, Chl b, and total carotenoids), and humification indices. Sand is the major fraction in these cores ranging from 60% to 99% followed by silt and clay; cores from the estuarine margin have high sand content. In mangrove forests, pore-water DOC concentrations are high (32 +/- 14 mg L(-1)), whereas salinity levels are low (50 +/- 5.5 parts per thousand). Likewise, LOI, organic C and N, and pigment concentrations are high in mangroves. OM is mainly derived from upstream terrestrial matter and/or mangrove litter, and marine OM. The humification indices do not vary significantly with depth because of rapid OM turnover. The bulk parameters indicate that the Vellar and Coleroon Estuaries are more affected by anthropogenic processes than mangrove forests. Finally, greater variability and sometimes lack of specific trends in bulk parameters implies that the 2004 tsunami caused extensive mixing in sediments. (C) 2010 Elsevier Ltd. All rights reserved.

Groundwater with high geogenic arsenic (As) is extensively present in the Holocene alluvial aquifers of Ghazipur District in the middle Gangetic Plain, India. A shift in the climatic conditions, weathering of carbonate and silicate minerals, surface water interactions, ion exchange, redox processes, and anthropogenic activities are responsible for high concentrations of cations, anions and As in the groundwater. The spatial and temporal variations for As concentrations were greater in the pre-monsoon (6.4-259.5 mu g/L) when compared to the post-monsoon period (5.1-205.5 mu g/L). The As enrichment was encountered in the sampling sites that were close to the Ganges River (i.e. south and southeast part of Ghazipur district). The depth profile of As revealed that low concentrations of NO3- are associated with high concentration of As and that As depleted with increasing depth. The poor relationship between As and Fe indicates the As release into the groundwater, depends on several processes such as mineral weathering, O-2 consumption, and NO3- reduction and is de-coupled from Fe cycling. Correlation matrix and factor analysis were used to identify various factors influencing the gradual As enrichment in the middle Gangetic Plain. Groundwater is generally supersaturated with respect to calcite and dolomite in post-monsoon period, but not in pre-monsoon period. Saturation in both periods is reached for crystalline Fe phases such as goethite, but not with respect to poorly crystalline Fe phases and any As-bearing phase. The results indicate release of arsenic in redox processes in dry period and dilution of arsenic concentration by recharge during monsoon. Increased concentrations of bicarbonate after monsoon are caused by intense flushing of unsaturated zone, where CO2 is formed by decomposition of organic matter and reactions with carbonate minerals in solid phase. The present study is vital considering the fact that groundwater is an exclusive source of drinking water in the region which not only makes situation alarming but also calls for the immediate attention.

Kanpur city has large number of small-scale industries (SSIs), primarily comprising of textile and leather industries. This study inventorises the presence of heavy metals in the samples collected from Panki and Jajmau Industrial Areas of Kanpur city. The bulk concentration of heavy metals found in solid waste samples was Fe as 1885 and 2340 mg/kg, Mn 173 and 445 mg/kg, Zn 233 and 132 mg/kg, Cu 20 and 28 mg/kg, Cd 1.4 and 1.1 mg/kg, Ni 26 and 397 mg/kg, Pb 107 and 19 mg/kg, Cr 1323 and 734 mg/kg, respectively. Heavy metal concentration was also found to be high in soil and road dust samples viz. Ni and Pb were in higher concentration in few samples, whereas Cr was found in higher concentration in all samples than the recommended values of USEPA and specifications for compost quality contained in the Indian Municipal Solid Wastes (Management and Handling) Rules, 2000. The heavy metal pollution so detected is indicative of contamination in ground and surface water and food chain. This raises concerns pertaining to adverse consequences to environment and human health.

In order to characterize the sources and fate of organic matter (OM) in the Pichavaram estuarine-mangrove ecosystem (east coast of India), stable isotope (δ 13 C and δ 15 N) ratios and molecular lignin analyses were conducted in plant litter, benthic algae, sediment, particulate matter and in a variety of benthic invertebrate species. The δ 13 C signature of plant litter ranges from −29.75‰ to −27.64‰ suggesting that mangrove trees follow the C 3 photosynthetic pathway. Sedimentary δ 13 C signature (−28.92‰ to −25.34‰) demonstrates the greater influence of plant litter organic matter on sedimentary organic matter. Suspended particulate organic pool was influenced by terrestrial source and also seems to be influenced by the marine phytoplankton. Enriched signature of δ 15 N in surface sediments (4.66–8.01‰; avg. 6.69‰) suggesting the influence of anthropogenic nitrogen from agricultural fields and human settlements. Spatial chemical variability in availability of nitrogen and plant associated microbial interactions demonstrate variability in δ 15 N signature in mangrove plant litter. Two (lower and higher) trophic levels of invertebrates were identified with and observed >4‰ gradient in δ 13 C signal between these two trophic groups. The observed δ 13 C values suggest that the lower level invertebrates feed on phytoplankton and higher level organisms have a mixed source of diet, phytoplankton, sediment and particulate organic matter. Lignin phenol analyses explain that the benthic surface layer was almost free of lignin. The ratio between syringyl phenols to vanillyl phenols (S/V) is 1.14–1.32 (avg. 1.23) and cinnamyl phenols to vanillyl phenols (C/V) is 0.17–0.31 (avg. 0.24), demonstrate non-woody angiosperm tissues was the major sources of lignin to this ecosystem, while aldehyde to acid ratios (Ad/Al) describe diagenetic nature of sediment and is moderately to less degraded. A two-end-member mixing model indicate that the terrigenous OM was dominant in the estuarine zones, while in the mangrove zone terrigenous supply accounts for 60% and marine input accounts for 40%.

Mangrove sediments play a pivotal role in the nutrient biogeochemical processes by behaving as both source and sink for nutrients and other materials. Surface and core sediments were collected from various locations of the Pichavaram mangrove (India) and analyzed for grain size distribution, nutrients and stable N isotope (δ15N) signatures in order to understand the spatial and vertical distribution of nutrients and biogeochemical processes of the C, N, P and S in this ecosystem. Sand is the dominant fraction followed by silt and clay. Spatial distribution of nutrients is controlled by the external and internal loadings, whereas vertical distribution is largely driven by the in situ microbial activities. Interior mangrove sediments contain higher concentrations of organic carbon (OC) than the estuarine sediments reflecting high rates of organic matter retention. Finer fractions of sediment hold ∼60% OC due to high surface area. At some sampling points, moderately high δ15N signatures were observed and this may be because of agricultural runoff and aquaculture effluents.

A pot-culture experiment was conducted to observe the effects of acidic sludge addition to the soils on bioavailability and uptake of heavy metals in different parts of pea plant as well as its influence on the growth of that plant. It is observed from our result the abundances of total and bio-available heavy metals in sludge vary as follows: Fe > Mn > Cr > Ni > Cu > Pb > Zn > Cd and Fe > Ni > Mn > Cr > Cu > Zn > Pb > Cd. Sludge applications increased both the total metals, DTPA-extractable metals and total N in the soils. On the other hand lime application has decreased the bioavailability of heavy metals with no change in total N in sludge amended soils. Organic carbon showed positive correlation with all metals except Zn, Cr and Pb. CEC also showed a strong positive correlation ( R 2 > 0.7) with the low translocation efficiency of pea plants. The value of translocation factor from shoot to seed was found to be smaller than root to shoot of pea plants. Our study thus shows that pea plants were found to be well adapted to the soil amended with 10% sludge with 0.5% lime treatment, minimizing most of the all metal uptake in the shoot of that plant. So, on the basis of the present study, possible treatment may be recommended for the secure disposal of acidic electroplating sludge.

Typha angustata L. is a wetland plant commonly found in the marshy land or flood planes of the Ganges riverine system. A field study was taken on T. angustata L. to evaluate the uptake and transport of heavy metals (Mn, Cu, Zn, Cr, Ni and Pb) in different parts of plants grown on waste amended soils in water logged condition for 3 months. T. angustata L. accumulated Mn, Cu, Zn, Cr, Ni and Pb up to 119.21 ± 5.8 µg g− 1, 4.18 ± 0.5 µg g− 1, 5.72 ± 1.1 µg g− 1, 15.4 ± 1.9 µg g− 1, 5.3 ± 0.8 µg g− 1 and 7.21 ± 0.9 µg g− 1 in below ground organ (BL) respectively. Whereas, the maximum metal contents in above ground organ (AG) were 43.86 ± 3.2 µg g− 1, 1.73 ± 0.04 µg g− 1, 2.11 ± 0.07 µg g− 1, 6.31 ± 0.3 µg g− 1, 1.8 ± 0.04 µg g− 1 and 2.75 ± 0.03 µg g− 1 respectively. The plant also retained the tissue nitrogen up to 6.1 ± 0.38% in BL and 9.82 ± 0.54% in AG. It accumulated the maximum concentration of phosphorus 0.25 ± 0.02% in BL and 0.41 ± 0.02% in AG. Metals in both BL and AG were enriched with exposure, but the translocation factor was higher in BL in all amendments. Metal translocation factor was higher in BL/soil than AG/soil to a large extent. The translocation factor of metal from water to below ground organ was higher than water to above ground organ with a maximum value for Cr. There is a strong positive correlation of metal contents in plant tissue with soil organic matter (OM), and phosphorus contents in plant tissue. There is no significant correlation between metal uptake and nitrogen contents in plant tissue. This study reveals that T. angustata L. can be used for remediation of heavy metals containing waste when used in 25% waste amendment.

The fractionation of P in Pandoh Lake surface sediments has been investigated for the first time in order to understand its environmental availability and sources, and the eutrophication status of this lake. Inorganic-P is present mainly as authigenic-P (step-III). The authigenic P concentration is higher in winter relative to the summer and monsoon seasons and ranged from 35.9 to 46.9 μg/g. The loosely sorbed or exchangeable-P (step-I), Fe(III)-bound-P (step-II) and detrital inorganic-P (step-IV) were higher in the monsoon season and varied from 3.70 to 11.1 μg/g, 16.9 to 32.0 μg/g and 9.89 to 17.0 μg/g, respectively. Organic-P reached a maximum in the summer season and ranged from 8.00 to 14.9 μg/g. Authigenic-P and detrital inorganic-P show seasonal changes, as pH influences the interaction between P and CaCO 3 in the water column. In the winter season, phosphate is precipitated out of the water column and fixed in the sediments as a result of an increase in pH. Calcite-bound-P in the sediments may be redissolved by decreasing pH in the summer season. Relatively high rates of mineralization during the monsoon results in the seasonal pattern of organic-P fractionation to sediment as follows: monsoon = winter

Pandoh is a beautiful Lake surrounded by Shivalik sequences (Lesser Himalaya) in the Mandi District of Himachal Pradesh. A comprehensive and systematic study on the seasonal pattern of major ions (Cl−, PO 4 3 - , HCO 3 - , NO 3 - , SO 4 2 - , Na+, K+, Ca2+, Mg2+) and SiO2 was carried out to understand the geochemical processes controlling water quality. There is marked seasonal variation for almost all ions. Carbonate weathering and atmospheric precipitation are strong factors controlling the chemistry of major ion such as Ca2+, Mg2+ and HCO 3 - in the winter and summer seasons. In the monsoon season, relatively low concentrations of all the ions were observed due to dilution effects. Ca2+, Mg2+ and HCO 3 - generally account for about 70% of the total ions throughout the year. The ratios Ca2+ + Mg2+/Na+ + Cl−, HCO 3 - /(Ca2+ + Mg2+), (Ca2+ + Mg2+)/ T z + , ( Na + + K + ) / T z + indicate that carbonate weathering is the main control on water chemistry in contrast to other Himalayan lakes. The low concentrations of Na+ and K+ indicate a minimal contribution from the weathering of silicate minerals to Pandoh Lake. Correlation matrix and principal component analysis were used to identify various factors influencing the ionic strength of Pandoh Lake waters. The overall water quality variation (in space and time) as well as comparison with the quality of other Himalayan lake water indicates that this lake is non polluted, however there are indications of possible enrichment of nutrients (eutrophication) in the near future in the Himalayan region of the Indian subcontinent. Hence Pandoh Lake deserves further detailed attention for management of the water resource to preserve its eco-hydrological status.

The nature of solute transport in the Cauvery river was studied during a 5 year period (1985–1989). On the basis of our analytical results, the discharge weighted average chemical composition of the Cauvery river has been computed and compared with major rivers of India and the world. The chemical composition of Cauvery river water is dominated by Na and HCO 3 . The river water chemistry strongly reflects the dominance of continental weathering and impact by atmospheric precipitation. The river water composition is increasingly dominated by Na and Cl in the downstream region of the river, indicating the influence of airborne salts with oceanic affinities. The observed chemical data of the Cauvery river water was used to predict the mineral assemblages in the carbonate and alumino-silicate system and compared with observed mineralogical composition of suspended sediments. Over 90% of the material transported in the Cauvery river is transported in dissolved form. The total dissolved material transported from the Cauvery to the Bay of Bengal accounts for 14% of the annual flux of dissolved load from Indian rivers to the neighboring seas.

During the monsoon period, 75% of the annual rainfall, 73% of the annual water discharge and 85% of the annual sediment transport takes place in the Cauvery River. Basin geology and river water discharge are the major natural factors controlling the sediment transport. Sediment transport in the Cauvery River is greatly influenced by the presence of two major dams built across the river. An examination of the particle-size distribution of the suspended sediments shows that the less than 20 μm fraction accounts for nearly 60% of the total sediment transported by the river. At dam sites, coarse sediments are selectively removed from the suspended load. The suspended mineralogy is dominated by quartz and feldspar, followed by clay minerals and carbonates. Clay minerals average about 30% and are dominated by the montmorillonite type. The results of our study also demonstrate the importance of such sediment characteristics as particle size and mineralogy in controlling the trace metal distribution in sediments.