Search

Water pollution is a major concern for a decaying river. Polluted water reduces ecosystem services and human use of rivers. Therefore, the present study aims to assess the irrigation suitability of the Jalangi River water. A total of 34 pre-selected water samples were gathered from the source to the sink of the Jalangi River with an interval of 10 km and one secondary station's data from February 2012 to January 2022 were used for this purpose. The Piper diagram exhibits that the Jalangi River water is Na+–HCO3− types, and the alkaline earth (Ca2+ + Mg2+) outperforms alkalises (Na+ + K+) and weak acids (HCO3− + CO32−) outperform strong acids (Cl− + SO42−). SAR values ranging from 0.35 to 0.64 show that water is suitable for irrigation and poses no sodicity risks. The %Na results show that 91.18% of water samples are good and acceptable for irrigation. RSC levels indicate a significant alkalinity hazard, with 94.12% of samples considered inappropriate for irrigation. PI findings show that 91.18% of water samples are suitable for irrigation. Apart from the spatial water samples, seasonal water samples exhibit a wide variations as per the nature of irrigation hazards. Gibbs plot demonstrates that the weathering of rocks determined the hydro-chemical evolution of Jalangi River water. This study identifies very little evaporation dominance for pre- and post-monsoon water. The analysis of variance (ANOVA) test illustrates that there are no spatial variations in water quality while seasonal variations are widely noted (p < 0.05). The results also revealed that river water for irrigation during monsoon is suitable compared to the pre-monsoon season. Anthropogenic interventions including riverbed agriculture, and the discharge of untreated sewage from urban areas are playing a crucial role in deteriorating the water quality of the river, which needs substantial attention from the various stakeholders in a participatory, and sustainable manner. [ABSTRACT FROM AUTHOR]

The present study is conducted to assess the radiological and hydrogeochemical quality of earthly bore potable water in Haridwar, Uttarakhand, India. Radon activity concentrations in water samples ranged from 0.59 ± 0.04 to 57.32 ± 4.39 Bq/L. The average activity concentration of radon is estimated as 10.46 ± 1.05 Bq/L. Annual Effective Inhalation dose to humans ranged from 1.48 μSv/Y to 144.45 μSv/Y with an average value of 26.36 μSv/Y. Ca2+ > Na+ > Mg2+ > K+ and HCO3− > CaCO3− > SO42− > Cl− > NO3− > F− were the concentration orders of the primary cations and anions. The majority of tests contained acceptable levels of ions and TDS, indicating that the region's groundwater is safe for consumption. For irrigation purposes, the sodium absorption rate, sodium percentage, and magnesium risks were examined. The weathering of rocks was discovered to be the key factor influencing the chemistry of the groundwater in the region. The spatial patterns of observed fluctuations were investigated using the collected data set. [ABSTRACT FROM AUTHOR]

For the US-India bilateral relationship, the first four months of 2024 were a repeat of the last three years: the differences in attitudes toward Cold-War era partnerships resurfaced and made difficult maintaining the calm in bilateral relations. There were significant strides in the economic and trade front. The security relationship, however, was marred by the dispute over the killing of Khalistan separatist, designated as a terrorist by India. Washington diplomatically backed India vis-a-vis China's belligerent actions such as renaming Indian towns by publicly speaking out against it and top military brass made visits to India in a show of support for the growing security cooperation between the two democracies. The election hysteria in India, the heated rhetoric, and polemical statements in the election campaigns of major India political parties provided fodder for the Western press to raise concerns about the supposed "values-based" partnership with India. While not as hyperbolic in nature, US election campaigning dragged India into the mud, with President Biden lumping Japan and India in with Russia and China in a reference to nations that were "xenophobic" and restrictive to immigrants. [ABSTRACT FROM AUTHOR]

The study determines the major ion chemistry of the Teesta River catchment in the Eastern Himalayan region and evaluates hydrochemical processes controlling water composition of the catchment area. Water of the Teesta River basin was in neutral to alkaline condition. HCO3−, Ca2+, Na+, Mg2+ and SO42- were identified as the dominant ionic species in the Teesta catchment water composition and Ca-Mg-HCO3 as the dominant hydrochemical facies. Higher contribution of (Ca2++Mg2+) and HCO3− towards the TZ+ and TZ−, high ionic ratios of (Ca2++Mg2+)/(Na++K+), HCO3−/(Cl−+SO42-) and low (Na++K+)/TZ+ ratio suggest carbonate weathering as a major contributor of dissolved ions in the Teesta basin water. Under-saturation with respect to both carbonate and sulphate phase minerals suggests that water can dissolve these minerals during water-rock interaction. Concentration of the analysed water quality parameters were well below the specified drinking and irrigation water limits. [ABSTRACT FROM AUTHOR]

Microplastics have become a serious concern in the contemporary world due to their widespread and hazardous nature. This study investigates microplastic distribution in one of the largest brackish water lagoons in the world (Chilika Lake, India) to bridge the knowledge gap in a transitional environment. Sediment and water samples were investigated to estimate microplastic count and were categorized based on their shape, color, size, and polymer type. The overall abundance of microplastic in sediment and water sample from Chilika Lake varied from 25.2 ± 9.8 items/kg to 7 ± 2.2 items/kg and 110.7 ± 35.6 items/100L to 26 ± 8.1 items/100L, respectively. Anthropogenic activities such as extensive fishing activities and tourism were attributed to be the major source of microplastic besides upstream loads through inflowing rivers. Fragments and foams were the most commonly occurring microplastic shapes in sediment and water samples, respectively. Sediment samples were found to be highly abundant in microplastic particle size <1 mm. Water samples were dominated by white-color foams in 2–5 mm size range of microplastics. Ten different types of microplastic polymers were identified, of which polypropylene and polystyrene were the most dominant microplastic in sediment and water samples. Microplastic morphology showed surface features that can be attributed to their weathering. The study provides baseline information on microplastics in Chilika Lake to develop an insight into the associated environmental and health risks. [ABSTRACT FROM AUTHOR]

The geochemical signatures of recent stream sediments in the study area revealed an old recycled sedimentary source and weak to moderate chemical weathering. The sediments exhibit a positive correlation of large ion lithophile elements (Ba, Sr, and Rb), transition trace elements (Co, Cr, Cu, Ni, Sc, and V), and REE with Al2O3 and associated immobile oxides, indicating affinity with phyllosilicate sedimentary rocks of Semri Group of Vindhyan basin. The La–Th–Sc and Th–Sc–Zr/10 ternary plots show mixed sediment sources of clays, silts, and sands. Positive correlations of LREE with Th, Zr, Al2O3, and TiO2 and negative correlations with Y and P2O5 suggests the cumulative influence of Ti-bearing minerals and clay minerals. The high Zr/Sc ratio (mean 30.8), strong LREE/HREE enrichment (mean 8.1), prominent negative Eu anomalies (mean 0.57) and flat HREE suggest input from the recycled sedimentary source. The mean chemical index of alteration (69.17), plagioclase index of alteration (74.94), chemical index of weathering (93.08), and ACNK indicate weak to moderate weathering with the presence of minor K-feldspar mixed in illite dominated mud. This is also supported by a high Rb/Sr ratio (mean 1.09) and K/Rb ratio (0.018). A higher K/Al than Na/Al ratio points to higher illite content. The presence of illite, minor feldspar, and less SiO2/Al2O3 ratio (mean 4.98) suggests low textural and compositional maturity, attributed to the mixing of sediments by significant physical weathering. The positive correlation between Th/Sc (mean 0.6) and Zr/Sc (30.8) indicates less fractionation, low to moderate hydraulic sorting, and sufficient sediment recycling in Kurheri sediments. [ABSTRACT FROM AUTHOR]

This study presents the probable environment from petrographical, mineralogical and geochemical analyses of representative samples from Bamhantara block, Kabirdham district, Chhattisgarh, India using EPMA and SEMEDS for petrological study, and XRF and ICP-MS for geochemical inference. Microscopic study revealed the dominance of boehmite minerals that specify the synenvironmental depositional condition, while circular/ well-rounded pisolitic texture indicated autochthonous deposits. The geochemical study determined the progressive changes in major, trace and REE concentrations from precursor rock to bauxite during weathering. Bamhantara bauxite has been formed under oxidizing (positive Ce anomalies; Ce/Ce*, 0.92–2.15) and near alkaline to alkaline ((La/Yb)N and La/Y ratio > 1) conditions. The analogous trend of REE for bauxite/laterite and precursor rock indicates that lateritic bauxite had an autochthonous origin and is a chemical disintegration product of Deccan Trap basalt under tropical to subtropical climates. The geochemical behaviour of REE revealed that bauxite/laterite was generated from type-2 basalt characterized by positive Ce, Eu and Dy anomaly. The low concentration of kaolinite indicates desilication under a hot tropical climate. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate and analyse the water quality in the Tulsishyam region in terms of corrosive and scaling properties. Thermal water samples (TWS), groundwater samples (GWS), and riverwater samples (RWS) were collected and analysed for a variety of geochemical parameters in various locations throughout the Tulsishyam region. The pH of such thermal springs ranges between 7.1 and 7.4, suggesting that they are neutral, and the temperature ranges between 39 and 42 °C. To determine the corrosive and scaling properties of water, various indices such as the Langelier Saturation Index (LSI), the Puckorius Scaling Index (PSI), the Ryznar Stability Index (RSI), and the Larson Index (LaI) are used. According to the indices described previously, all water samples are extremely corrosive to intolerably corrosive with a significant abrasion rate. The chemical composition of the fluids is also investigated in relation to the weathering processes. Sulphate has a significant negative link with chlorine and a weak correlation with bicarbonate, whereas chlorine has a moderate correlation with bicarbonate, according to multivariate analysis. Industrial usage of water samples from the study area should be limited due to the aggressive nature of the water samples. [ABSTRACT FROM AUTHOR]

To ascertain weathering, provenance, and paleoclimate of the last ca. 29 ka in mainland Gujarat, western India, a sedimentary profile of ~7.5 m was measured, described, and sampled at Pratappura and a multiproxy analysis was conducted. To determine weathering, siltysand and sandy-silt facies were analyzed, and log Na2O/K2O versus log SiO2/Al2O3 was plotted, which shows clustering in the quartz arenite and sub-litharenite categories, indicating low to moderate weathering. The chemical index of alteration (CIA) is 55-74, and was plotted versus the index of chemical variability (ICV) of 1.50, with samples clustered mainly between subalkali basalt and picrite, indicating the dominance of a mafic component. While depleted chondrite normalized light rare earth element (REE) (La/Yb <1) levels suggest the prevalence of a mafic source in the catchment, identical chondrite normalized REE patterns indicate that sediments were well homogenized. Using multiple proxies, the measured profile was subdivided into five paleoclimatic zones. Zone-I (29-18 ka) exhibits decreasing moisture, Corg, χlf, Al2O3, TiO2, and Fe2O3 trends, while higher values of CO3-2 and δ13C indicate a change from a warm-humid to semiarid climate. Zone-II (18-11 ka) shows signs of the beginning of aridity ca. 18 ka during the Last Glacial Maximum (LGM). Several proxies in zone-III show wetter climatic conditions from the early Holocene (ca. 11-4 ka) due to the onset of the SW monsoon, with the trend continuing in zone-IV (4-2 ka). In zone-V, the climate appears to have been similar to the modern conditions in the area from 2 ka-present. [ABSTRACT FROM AUTHOR]

This study presents a slope stability assessment of Siwalik rocks formations along an old, unpaved road connecting Dehradun to Thangaon village via Dunga village located in the Himalayan foothills. This road is a part of the proposed major road connecting Dehradun-Mussoorie. Hard rocks in the study area are medium-grained, massive sandstones composed of ∼100% quartz and less prone to weathering, while soft rocks are quartz-rich with ∼10% micaceous/argillaceous minerals, fine-grained, relatively laminated sandstones that are more prone to weathering. Joints are prominent in the hard and massive sandstones. Joint openings range from 0.5–1 mm to 2–3 cm. Rock mass rating and slope mass rating criteria along with kinematic analysis reveal that bedding, natural joint, and excavation faces are oriented such that ∼50% of locations have chances of wedge failure. Roads oriented in the NNW-SSE directions with ridges to the left are the most vulnerable to rock slides as evidenced by slope assessment. Natural joint orientations with respect to bedding strikes are unpredictable, as bed strike-parallel, strike-perpendicular, and strike-oblique joints are present at various locations. Most rock fall incidents happening during the monsoon implies extra water from the rains acts as failure catalyst. Based on the field observations, select remedial measures were suggested. [ABSTRACT FROM AUTHOR]

The Deccan basalts have been undergoing intense weathering in the tropical conditions since the passage of India through the equator. This study is on the basalts' weathering from central India's present-day semiarid climate. Two weathering profiles from the districts of Indore and Dhar, Madhya Pradesh, have been studied using mineralogy and geochemistry. The profiles show incipient weathering with low to medium Chemical Index of Alteration (CIA) and Mafic Index of Alteration-oxidising (MIA(O)) values. The presence of smectite in weathered zones, mineralogically attests to incipient weathering. The pyroxene and plagioclase-rich zones have produced smectite clays in the basalts. The rare earth elements (REE) and, to a greater extent, the heavy (H) REE show mobility during incipient weathering, which appears to be due to differential retention of REE in the clay minerals. The smectites seem to retain light (L) REE more significantly than HREE. The ancient terrain showing currently incipient weathering indicates recent exposure of the profiles by the erosion under neotectonic activity. In this fashion, the frequent exposures of new weathering surfaces on the basalts may have played a significant role in the uninterrupted consumption of CO2 by silicate weathering since around 50 Ma. [ABSTRACT FROM AUTHOR]

The main aim of this research is to assess the consequences of natural and anthropogenic processes on the groundwater quality of 65 deep aquifers of Nagpur city, Maharashtra Province, India, using a unified multivariate statistical approach. The dominant groundwater type recognized is Ca–HCO3 (recharge waters) in 43.1 and 38.5% of groundwater samples of pre- and post-monsoon seasons, followed by mixed water types. The seasonal distribution of physicochemical parameters shows increase in the concentration of EC, TDS, TH, Mg2+, SO42−, and NO3− signifying the high mineralization and anthropogenic loading from pre- and post-monsoon season respectively. The entropy-weight water quality index categorizes the 84.6% and 75.4% of total samples from pre- and post-monsoon seasons into moderate quality. The multiple linear regression and PCA analysis reveal the masking of rock weathering mechanism by anthropogenic activities. The % of PCA Variance varies from 79 to 83.7% from pre- to post-monsoon season. The high contributions of EC (0.76, 0.72), TDS (0.79, 0.73), TH (0.97, 0.962), Ca2+ (0.84, 0.78), Mg2+ (0.79, 0.83), Cl− (0.73, 0.75), and NO3− (0.78, 0.68) in PC1 components expose high salinity and hardness in urban groundwater that signifies the consequences of urbanization on the groundwater regime. About 55.4 and 70.8% of children population as compared to the adult female (53.8%, 69.2%) and male (32.3%, 46.1%) population in PRM and POM respectively were at high non-carcinogenic health threat of NO3−-enriched groundwater. The study is beneficial for understanding the variation in groundwater composition due to unplanned urbanization and is very useful for protecting groundwater resources in urban areas. [ABSTRACT FROM AUTHOR]

This study aims to determine variations in the terrigenous influx, the intensity of chemical weathering, pedogenic activity, and provenance of Shantisagara lake sediments in southern India for the past 11,000 years reconstructed using geochemical and magnetic susceptibility data. The results showed that K/Al, Fe/Al, Ti/Al, and Zn/Al ratios exhibited significant down‐core variations, whereas P/Al, Pb/Al, Na/Al, Cu/Al, and Ba/Al display steady values. The sediments have resulted from moderate to intense degree of chemical weathering and show high compositional maturity. The discrimination function diagrams, Al2O3/TiO2 and K2O/Na2O values, point towards a change from an intermediate source during the Early‐ and Mid‐Holocene to a felsic one during the Late Holocene. The similar LREE‐enriched chondrite‐normalized REE patterns indicate no significant change. The Early Holocene phase was characterized by a moderate influx of fine detrital fraction with a peak around 10,500 cal. Years B.P. The pedogenesis was strong in the catchment area during this period, with oxic conditions prevailing in the lake. The catchment area experienced moderate to high rainfall during this period. A fluctuating trend of terrigenous influx and chemical weathering is documented during ~8,000–4,000 cal. Years B.P. period in response to variable rainfall. Decreasing rainfall trends are observed during 4,000–2,000 cal. Years B.P., with a slight increase from 2,000 cal. Years B.P. to the Present. Anoxic conditions were present in the lake during the Middle‐ and Late Holocene with low pedogenic activity in the catchment. [ABSTRACT FROM AUTHOR]

Detrital mineralogy, major oxides, trace, and rare earth elements (REE) were examined in the Middle Jurassic Fort Member Sandstone (FMS) of the Jaisalmer Formation in Western India to understand palaeoweathering, provenance of sediments, and to decipher the tectonic setting. The sandstones are classified as arkose to sub‐litharenite types according to their relative percentages of quartz, feldspar, and lithic fragments, and major elemental ratios. The values of Chemical Index of Alteration (67–85), Plagioclase Index of Alteration (78–97) and Chemical Index of Weathering (83–97) along with A‐CN‐K diagram suggest moderate to intense chemical weathering in the source region. Presence of fresh feldspars and dominance of monocrystalline quartz, showing both parallel and undulose extinction, indicate plutonic and volcanic felsic igneous provenance. Contribution from metamorphic orogen sources is indicated by the lithic fragment population. Various geochemical parameters such as Th/Sc, Cr/Th, Ti/Zr, and Eu/Eu* support a dominant felsic provenance. Higher Zr/Sc ratios relative to the magmatic Zr/Sc‐Th/Sc trend, higher Zr and Hf concentrations in the FMS indicate some extent of sedimentary recycling and zircon sorting. LREE enrichment, flat HREE pattern, negative Eu anomaly and trace element ratios, in conjunction with palaeocurrent data, indicate a likely sediment contribution from basement source terrains including Erinpura‐Mount Abu‐Sirohi granites, Malani Igneous Suite, and Aravalli‐Delhi orogens. The major and trace element tectonic setting discrimination diagrams for the FMS indicate a passive margin setting. [ABSTRACT FROM AUTHOR]

The coastal deposits along the eastern part of the Indian Peninsula are known for the high abundance of heavy minerals. The present study, as discussed here, has been undertaken along the south-western coastal part of Odisha, India, adjoining the charnockite–migmatite zone of the Eastern Ghat Mobile Belt (EGMB). The composition of the placers along the study area is primarily controlled by the detritus from the proximal hinterland rock type(s). The weathering index has been established based on the grain morphology, major element concentration and radioelement ratios. Petrological characteristics and grain morphology of monazite, zircon, ilmenite and rutile have been presented respectively, and their implications are discussed. The provenance study of these coastal placers is based on the abundance of rare earth elements (REE) and radioactive elements in the placer sands and the rock types in the study area. The tectonic implications are based on the major element abundance of the beach sands. [ABSTRACT FROM AUTHOR]

The present study investigates the chemical composition of weathering profiles developed on two contrasting parent rocks (granite-gneiss and amphibolite) from Bomdila area, NE Lesser Himalaya, northern India. Granite-gneiss section of around 5 m thickness is physically divided into soil and saprolite zone, whereas the amphibolite section of around 20 m thickness is mesoscopically divided into soil, saprolite and saprock. The chemical index of alternation (CIA) and other indices for measuring the degree of alteration indicate incipient to moderate weathering intensities. Relative mobility calculations reveal some dramatic differences in elemental behaviour between the two profiles. The variation in the enrichment and depletion of certain major oxides indicate that the mobility of elements within the profiles seems to have distinct controls. The concentration of Ba, Sr and Y is increased relative to the parent rock, indicating adsorption by secondary minerals. In the case of amphibolite profile, Ba is retained, whereas Sr and Y are removed from the profile. The Rare Earth Elements (REEs) abundance shows a pronounced depletion from both the profiles when compared to bedrock. Moreover, La/Yb ratio along with Eu/Eu* and Ce/Ce* anomalies indicate low pH and prevalence of reducing climatic conditions. When a statistical test (t-test) is applied for these two profiles along with other profiles having almost the same parent rocks and from different geographical elevations across the globe, it is observed that the geographical elevation (which implies differences in weathering environment), as well as outcrop-scale factors (such as presence of fractures, redox conditions) could surpass parent rock composition in finalizing chemistry of weathering profile. Research highlights: Weathering intensity in both profiles range between incipient to moderate intensity. Elements distribution in the two weathering profiles is almost similar, although these profiles have contrast parent rocks. Geographical elevation and climate condition are the primarily factors controlling elemental mobility. Outcrop-scale factors (such as biological activities, fracture patterns, redox conditions etc.), significantly influence elements distribution within profiles. [ABSTRACT FROM AUTHOR]

Groundwater chemistry is mainly governed by lithological variations, space and resident time. In addition, hydrogeochemical characteristics of groundwater in the lithological contact zones are too complex. Hence, Cretaceous–Tertiary (KT) boundary from Ariyalur district, Tamilnadu, India, was selected for this study to identify the hydrogeochemistry of groundwater. This study includes 284 groundwater samples from four different seasons (pre-monsoon, post-monsoon, southwest monsoon and northeast monsoon). Groundwater samples were collected and analysed for major cations and anions, including physical parameters using standard procedures. High electrical conductivity (EC) showed the longer residence time of groundwater in hard rock region at the central and southern part of the study area. Ca2+, Na+, Cl− and HCO3− are the dominant ions in all the four seasons. The seasonal composition migration was observed from Na–Ca–Cl–HCO3 type to Na–Mg–Cl–HCO3 type, and Ca-HCO3 is the predominant water type in piper plot. Interpretation of data reveals that the groundwater quality was unsuitable for domestic and irrigation purposes during pre- and southwest monsoon seasons. Rock–water interaction and dissolution of minerals are the main sources of groundwater chemistry. Agriculture activities during monsoonal seasons also play a role in controlling the hydrogeochemistry of groundwater in this region. [ABSTRACT FROM AUTHOR]

The petrography and geochemistry of clastic rocks from the Upper Cretaceous Terani Formation of the Cauvery Basin were studied to decipher their intensity of weathering, provenance, and tectonic history. Texturally, the Terani sandstones are moderately sorted with sub-angular and sub-rounded grains, indicating short transport and low maturity. The average Quartz-Feldspar-Rock fragment (Q-F-R) ratio of the Terani sandstone is Q89-F3-R8. Geochemically, the Terani clastic rocks are classified as sublitharenites, Fe-sand, shale, and Fe-shale types. The chemical index of alteration (CIA), plagioclase index of alteration (PIA), and chemical index of weathering (CIW) suggested moderate to high intensity of weathering in the source area. The enrichment of rare earth element (REE) contents in the Terani clastic rocks relative to UCC (Upper Continental Crust) indicates a higher concentration of heavy minerals. Likewise, the average values of Eu/Eu* (0.16), La/Sc (2.94), La/Co (2.15), Th/Sc (1.08), Th/Co (0.79), Th/Cr (0.12), and Cr/Th (8.39) revealed that the Terani clastic rocks were derived from a combination of felsic and intermediate source rocks. The chondrite normalized REE patterns of clastic rocks are characterized by a relatively flat HREE (Gdcn/Ybcn = 1.71), enriched LREE (Lacn/Smcn = 4.15), and negative Eu anomaly (Eu/Eu* = 0.16), which suggest the contribution of sediments with less HREE depleted source rocks from the Archaean group. A comparison of the REE pattern and Eu anomalies from this study with potential source rocks infers that the Terani Formation received a major contribution of sediments from the Dharwar Craton. [ABSTRACT FROM AUTHOR]

Hot and humid subtropical plateau regions are susceptible to land degradation in the form of weathering and gully erosion. Here, we investigate chemical weathering, gully erosion and cohesiveness through field-based measurements with a view to understand the controlling factors of potential land degradation, in complex river basin of the Chotanagpur plateau region in Eastern India. The layers of controlling factors of gully erosion were developed and prioritized considering boosted regression tree (BRT), alternative decision tree (ADT), particle swarm optimization (PSO) and random forest (RF) algorithms in the R software, and the results of these methods were also validated using receiver operating characteristic (ROC) curves. The spectroscopic analysis was carried out of collected soil samples to measure the degree of chemical weathering and cohesiveness. Furthermore, the climatic elements like temperature and rainfall were also considered for estimating the chemical weathering. The results of the gully erosion models (i.e., BRT, ADT, PSO and RF) show remarkable accuracy with ROC values of 0.93, 0.89, 0.91 and 0.84, respectively. An advanced decision tree model was integrated with the results of degree of chemical weathering and cohesiveness in geographical information system platform. The land degradation map developed from this approach shows that 10.53% of the study area is highly affected, whereas 17.36% area is moderately affected and the rest of the 73.85% area is less affected by land degradation. Our results provide essential information for policy makers in adopting measures for minimizing and controlling the land degradation. Our novel approach is significant to assess land degradation to a large scale. [ABSTRACT FROM AUTHOR]

Kedarnath temple is situated on the Garhwal Himalayan range near River Mandakini in Rudraprayag, Uttarakhand, India. The temple (more than 1200 years old) was badly affected by devastating floods and landslides during 13-16 June 2013. To protect the aesthetic value of this ancient temple, a systematic scientific conservation has been carried out. The present study describes the geochemical character of the rocks mounted on the temple. It also evaluates weathering trend of the rocks by studying petrography and the analysis of major oxides, using optical microscopy, Xray fluorescence and X-ray diffraction. Petrography and discrimination clusters analysis show that the rock is granitic gneisses in composition and is peraluminous in nature, while the new rock KDN2 sample shows paralkaline character. [ABSTRACT FROM AUTHOR]

India has one of the largest concentrations of rock-art sites. However, these rock shelters have deteriorated due to natural agencies. The present study was carried out in one such site in Central India, which is hosted by argillaceous and ferruginous sandstones, showing prominent chemical, biological and mechanical weathering. The results based on field investigations, petrography, XRD, FE-SEM-EDS and FTIR measurements have indicated that chemical weathering is caused due to infiltration of hydrothermal fluids through innumerable zones of weaknesses formed due to neotectonic activities in the Satpura Lineament Zone, especially along Gawilgarh and Salbardi Faults in this region. [ABSTRACT FROM AUTHOR]

Geochemical and isotopic investigations were carried out in the Tapi Valley geothermal area in India to determine the principal factors that are responsible for the geochemical evolution of the thermal and non-thermal waters in the study area. The impact of thermal water discharges on the surrounding potable water resources had also been assessed. It was found that thermal water did not contain any toxic elements (mercury, antimony, arsenic) which are detrimental to human consumption. Thermal waters were found to be less mineralized compared to the non-thermal ground waters. The water types of the thermal and non-thermal waters were found to be mostly Na–Cl–HCO3 and Ca–Mg–HCO3, respectively. Silicate weathering and ion-exchange processes were found to be main factors that determined the dissolved solute concentration in the study area. Stable isotopic (δ18O, δ2H) analysis unequivocally established the meteoric origin of the thermal waters. Thermal waters in Unapdeo, Anekdev, Kundwa and Ratanpura were found to have distinct isotopic compositions signifying that separate reservoirs were feeding these hot springs. The application of chemical geothermometers showed a wide variation in the estimation of reservoir temperature. The quartz geothermometer produced the most reliable reservoir temperature estimate of 110 ± 12 °C. Multicomponent geothermometry was found to better constrain the reservoir temperature. This modelling result indicated that the thermal water in this region had attained simultaneous equilibrium with respect to quartz, aragonite, stilbite, calcite, enstatite, heulandite, diopside minerals in the temperature range of 120 ± 5 °C which could be taken as the subsurface reservoir temperature. [ABSTRACT FROM AUTHOR]

Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi‐arid and sub‐humid climates, due to the difficulty of estimating hydro‐geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro‐geochemical dataset acquired at the Mule Hole catchment (4.1 km2), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long‐term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community. [ABSTRACT FROM AUTHOR]

[Display omitted] • The study analyzes weathering profiles across three distinct regions in India. • Weathering intensities show minimal variation, despite climate differences. • Trace elements distribution is influenced by the site-specific conditions. • Statistical analysis highlights local factors' role in soil chemistry. • The study emphasizes the intricate influence of local factors on weathering processes. In an attempt to constrain the micro-scale factors during weathering, large number of samples from four weathering profiles developed on granite and basalt rocks under different climatic conditions from western (Gujarat, GJ) and central (Bundelkhand, BK) India are reported in this study and compared these profiles with profiles from north eastern (Arunachal Pradesh, Lesser Himalaya, AP) India. In granitic profiles, the chemical index of alteration (CIA) values ranges from 50 to 85 whereas 42–90 CIA values are observed for basalt profiles. This highlights the significance of climate conditions (i.e., precipitation) over lithology in controlling weathering advancement. The results of the mass-transfer coefficient (τ) of major oxides significantly vary among the three granite and basalt profiles. The trace elements distribution in weathering profiles seems to be strongly controlled by the degree of weathering and formation of secondary minerals. Regardless of the nature of parent rocks, HFSEs (high field strength elements) tend to be enriched in the upper portion of all the weathering profiles; whereas REEs (rare earth elements) display variable behavior in each profile. The principal component analysis (PCA) reveals that three components are accounted for 89.14% of the variance. PC1 is attributed to weathering intensity and formation of secondary minerals, PC2 can be related to the lithology of parent material, and PC3 might be a location-specific factors. The present study shows that the geochemical characteristics of weathering profiles cannot be explained by the influence of a single weathering agent rather, there seems to be a significant role of local (or micro-scale) factors that controls the weathering and soil formation. [ABSTRACT FROM AUTHOR]

Uranium (U) is formed by the interaction of groundwater in aquifer and the surrounding rocks. The area chosen for this study is a hard rock terrain of various lithology in South India, which releases U in groundwater and affect the groundwater quality. Hence, this study was conducted to understand the geochemistry and temporal variations of U in groundwater with respect to saturation state of minerals for different seasons namely Pre-monsoon (PRM), Northeast monsoon (NEM), Southwest monsoon (SWM) and Post-monsoon (POM). A total of 216 groundwater samples were collected, representing various lithology (Fissile hornblende biotite gneiss, Charnockite, Quartzite, Granite and Flood Plain Alluvium) in the study area. The collected samples were analyzed for physical parameters such as Electrical conductivity, Total dissolved solids, pH and major ions. U was measured using Laser Fluorimeter. The study infers that weathering in SWM, ion exchange in PRM and POM and anthropogenic process in NEM were the three major processes that could dominate the hydrogeochemistry of U. The higher concentration of U has been highlighted, and the water–rock interaction has been studied to know the sources of origin and it has been plotted through bivariate and ternary diagrams. The saturation index study was made and calculated for uranium, carbonate, sulfate, silicate and phosphate minerals using PHREEQC Programme. Uraninite and Coffinite are the dominant saturated states of U minerals which tend to attain near saturation to saturation state irrespective of seasons. With the increase in U concentration irrespective of seasons, it was noticed that the saturation state of minerals is also increasing. Overall, the weathering process and the lithological impact are the sources for higher concentration of U and their minerals occurring in the study area. The outcome of the study will help the policy makers for sustainable management to safeguard the groundwater resource in this region. [ABSTRACT FROM AUTHOR]

In order to observe severe weather conditions during cyclones, thunderstorms, etc., IMAGER instruments on-board INSAT3D/3DR have been built with a flexible scanning feature known as 'rapid scan mode'. Using this feature, the number of scan lines over a given coverage region and the number of repetitions of the selected region can be programmed for scanning. Therefore, to understand the physical processes involved in convective clouds associated with severe weather phenomena, rapid scan of INSAT3DR mode is attempted. It has very high temporal resolution of approximately 4 min and 30 sec. The present study will help in better understanding of the physical processes of severe weather phenomena and in nowcasting. It will also help to improve the accuracy in the NWP model forecast through assimilation of radiances and atmospheric motion wind determined using rapid scan mode. [ABSTRACT FROM AUTHOR]

Present study aims to understand the hydrochemical changes in proglacial meltwater stream emerging from the termini of Dokriani Glacier, central Himalaya, India. The major ion concentration of melt water between the years 1994–2015 has been reassessed to infer the glacial/subglacial weathering induced ionic release from Dokriani glacier system. The results from meltwater data collected during post-monsoon period (October 2015) shows that Ca2+ is more dominant cation followed by Mg2+, K+, Na+ and SO42− is most dominant anion followed by HCO3− and Cl−. Scatter plot between Ca2+ + Mg2+ vs total cations shows the overall dominance of carbonate weathering whereas Na++K+ vs total anions shows high positive relation suggesting domination of both carbonate and silicate weathering. By comparison, the ionic concentration for the year 2015 suggests a significant increase since 1994; however, the discharge weighted concentrations could provide more detailed estimates. An increasing trend in major cations viz. calcium (Ca2+) and magnesium (Mg2+) while the bicarbonate (HCO3−), sulphate (SO42−) and nitrogen (NO3−) has been observed as major anion. Further, the source of Cl−, NH4+, and NO3− in the meltwater stream is mainly derived from the atmospheric precipitation, anthropogenic, and weathering process. The process of carbonate weathering and dissolution of rock is ascertained as the one which regulates the melt water chemistry. [ABSTRACT FROM AUTHOR]

This study examines the catchment and source morphodynamics of the Palar River, Southern Peninsular India. Here, we applied a multidisciplinary approach (Remote sensing Techniques, Lineament Analysis, Geochemistry and Ground Penetration Radar) for a better understanding of its evolution during Holocene times. The lineaments present in the Palar River basin are showing dominantly NE-SW trend. There are five major faults identified in the Palar River basin. Fault F1 (strike slip fault) occurs in the upper part of the Palar River following the NE-SW trend. Other major faults F2 and F3 occurs in the middle reaches with a transition zone where frequent smaller magnitude earthquake occured and fault F4 traverses in parallel to the Cheyyar River. Fault F-5 nearer to the east coast indicates a passive tectonic activity regime. The after-effects of tectonic activity in the basin is further implicit from the GPR Profile. The sediments of active Palar River are dominantly litharenite, arkose, wacke; while, the paleochannels are shale in composition. Weathering proxies such as CIA, PIA, elemental ratios along with A–CN–K plot indicate a post-depositional intense weathering due to climatic variability for paleochannel sediments. Due to ongoing tectonic activity in the sources region along with subsequent aggradation and degradation in fluvial regimes, the sediments of active Palar River shows low to moderate weathering. Moreover, the geochemical data also reveals that the sediments from the Palar River and paleochannels are predominately from active continental and passive continental margins respectively. Moreover, the Major Oxide, Trace Elements and REE elements data indicate that Palar River sediments are from a felsic source while paleochannels are from mafic source. Hence, our study suggests that the catchment area of the Palar River has been shifted to the southward during the Holocene period due to tectonic uplift. Subsequently, the sediments of the paleochannels have undergone post-depositional weathering. Due to ongoing tectonic activity and intense precipitation in the region, enhances rapid erosion in the catchment area results in the deposition of the huge thickness of sediments from the middle to lower reaches of active Palar River. [ABSTRACT FROM AUTHOR]

Major and trace elements, including rare earth elements (REEs) geochemistry of bed sediments from the lower reaches of Krishna river suggest their origin mainly from weathering of Deccan basalts and Precambrian rocks of the southern India. The elemental compositions indicate evidence of sedimentary sorting during weathering, transportation and deposition. Highly depleted Na2O and high values of Chemical Index of Alteration (CIA) are suggestive of moderate to strong chemical weathering environment in lower reaches of Krishna river. Major, trace and REE concentrations of bulk sediments suggest marginal variations in relative contribution from mafic and felsic minerals. The bed sediments contain significantly low concentrations of trace elements like Ba, Sr, La, Ce and Nd and moderately low concentrations of V, Zr, Rb, Zn, Ni and Cr relative to upper continental crust (UCC) composition. Most of the other trace elements and REEs are almost similar to UCC indicating their origin from weathering of mixed rock types in catchment areas of Krishna river. Strong relationships of ΣREEs with Ti and Zr in bed sediments suggest that REEs are mainly controlled by heavy minerals such as titanite and zircon. A marked increase in REEs in clay fractions of sediments indicates their adsorption and/or substitution on clay lattice. [ABSTRACT FROM AUTHOR]

The shear strength of rock joints plays a key role in controlling rock mass behaviors. As the ongoing process of weathering in nature brings about intricate changes to rocks, shear behavior of rock joints is also influenced by the degree of weathering of the joint surface materials. However, efficiencies of the common and simple JRC-JCS models existing in the literature in predicting the shear strength with reference to weathering grades of rock joints does not seem to have been evaluated. In this study, a modification of the JRC-JCS model was proposed based on a total of 119 direct shear tests performed on natural, planner, unfilled and weathered (i.e. grades II and III) joints of granite and quartzite from India. Subsequently, the efficacies of the proposed criterion and three other apparently useful JRC-JCS models including Barton's model were evaluated in estimating the peak shear strength of rock joints with reference to a particular weathering grade as well as in regard to different weathering grades considered together. For such evaluation, the peak shear strength values with reference to weathering grades of the joint surfaces obtained from the direct shear tests of this study were considered. Additionally, the peak shear strength data for weathered non-planar granitic joints (i.e. grades I, II and III) existing in the literature was also taken into account. From the statistical comparison, it became evident that the shear strength criterion proposed in this study is significantly more efficient than the other considered criteria. The apparent superiority of the proposed criterion over the three other considered JRC-JCS models could be attributed to very different types of joint surfaces investigated in this study with reference to weathering grades and rock types. [ABSTRACT FROM AUTHOR]

We present stable calcium isotopic compositions (δ44/40Ca) of the Godavari River, the largest river in peninsular India, from the upper 750 km of its course, where it primarily drains the Deccan basalts. In addition to river water samples collected during the pre-monsoon and monsoon seasons, we also present δ44/40Ca values of groundwater, bedrock Deccan basalts, suspended and bedload sediments, and carbonate nodules from the Godavari Basin as well as zeolites and hydrothermal calcite from several locations within the Deccan Traps. The δ44/40Ca values (reported relative to NIST SRM 915a) of the dissolved load of the Godavari River main channel display large variability during both the pre-monsoon (0.73–1.64 ‰) and the monsoon (0.56–1.28 ‰) seasons. In the upper reaches (within 160 km of the source), the river water samples during both seasons show δ44/40Ca values (0.56–0.89 ‰) and Sr/Ca (mmol/mol) ratios (1.47–2.86), which are in the same range as that of the bedrock Deccan basalts (0.53–0.78 ‰ and 1.1–5.19 mmol/mol, respectively), suggesting control of water chemistry by basalt weathering. In contrast, in the middle reaches of the river (beyond 160 km from the source), the riverine δ44/40Ca values (0.99–1.64 ‰) are much higher than δ44/40Ca of bedrock basalt, but similar to that of groundwater in the middle reaches. We conclude that groundwater discharge to the river during the low-flow period has a significant control on the observed high δ44/40Ca values of the Godavari River. Additionally, the positive correlation between δ44/40Ca values versus Sr/Ca ratios and weak positive correlation of δ44/40Ca values versus saturation index of calcite suggests that carbonate precipitation from the river water impacts the δ44/40Ca values of the Godavari River in the middle reaches; this conclusion is consistent with the low δ44/40Ca of acetic-acid leached carbonate nodules (0.52–0.56‰) collected from the Godavari riverbed. The δ44/40Ca values of zeolites exhibit a large range from −0.72‰ (heulandite) to 1.67‰ (apophyllite) while the δ44/40Ca values of leached hydrothermal calcite samples range from 0.75‰ to 0.92‰. These values indicate that weathering of these Ca-bearing minerals has limited contribution to the calcium isotopic composition of the Godavari River, which contrasts with observations from relatively smaller rivers draining basalt in Iceland. The δ44/40Ca values of the dissolved load of the basalt-draining Godavari River is significantly higher than the estimated global riverine input to the oceans (0.88‰); given the high weatherability of basalts, the high δ44/40Ca values of basalt-draining rivers suggests that the estimate of the δ44/40Ca value of the average continental flux to the oceans may have been underestimated. The results of this study also demonstrate distinct differences in geochemical and Ca isotopic compositions of basalt-draining rivers from Iceland and India, which reflects fundamental differences in the weathering process in very different climatic regions. [ABSTRACT FROM AUTHOR]

Geostatistical modelling for a part of a ferruginous bauxite deposit in Eastern India has been carried out for estimation of mineral inventory and grade-tonnage relationships. Resource estimation of the bauxite deposit carried out by different agencies previously were on the basis of drill hole spacing employing fundamentally conventional cross-sectional techniques and in a limited way geostatistics. The conventional methods have limitation to specify the confidence limits (+/−) or, in other words, the percent accuracy of the estimated mean. One normally relies on approximation without any mathematical basis. However, no integrated mineral deposit modelling has been carried out combining deposit geology with geostatistics for development of mineral inventory and estimation of grade-tonnage relationships. An understanding of formation of bauxite by the process of residual weathering and lateritization of Archean khondalite and charnokite, when incorporated in population modelling and semivariography and integrated with appropriate geostatistical evaluation process provided a means to improved geocharacterization of the bauxite deposit. The integrated geostatistical modelling led to the quantification of the individual population characteristics and spatial relationships of the geo-variables. Spatial correlation modelling of the sample values through semivariography revealed a moderate to high nugget-to-sill ratio with moderate range of influence, characterizing the spatial variability of the ferruginous bauxite deposit. Geostatistical estimation employing 3D block kriging led to the generation of slice-wise block kriged estimates and kriging variances. Resulting block estimates, when stacked slice-wise one below the other, provided a 3D mineral inventory of 29.87 mt of bauxite averaging 42.04% Al2O3 and 2.88% SiO2. Spatial distribution maps of kriging variance aid in reflecting zones of uncertainty of varying magnitude associated with block estimates. [ABSTRACT FROM AUTHOR]

The Palaeo to Mesoproterozoic Dalma volcano-sedimentary basin (DVSB) is a typical greenstone belt sequence within the North Singhbhum Mobile Belt (NSMB) of Singhbhum Crustal Province (SCP), eastern India. The volcano-sedimentary belt is situated in the central portion of NSMB and separates the Chaibasa and Dhalbhum formation lying at its south from the Chandil Formation at its north. The metasedimentary unit comprises carbonaceous phyllite, carbonaceous cherty quartzite, quartz mica schist and quartzite. In the present work, the Au-rich carbonaceous metasedimentary rocks were studied to understand the source rocks characteristic, paleoweathering history and possible tectonic set-up. Geochemical classification diagrams based on the major oxide data indicates that these units belong to arkose to wacke field and the protolith underwent moderate to high degree of chemical weathering. Based on critical elemental ratios, it is inferred that the sediments were subjected to moderate degree of physical weathering, associated with sediment sorting and recycling. A fractionated REE pattern coupled with prominent negative Eu anomaly and elevated Th/Sc ratios indicate a felsic provenance for these metasedimentary units. The data further suggests that the sediments were deposited in a passive margin tectonic setting, during a prolonged period of upliftment and erosion of the Archean Singhbhum granite complex. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Detailed hydrogeochemical study is carried out in the Mahanadi river basin. • Chemical weathering rate in the basin is similar to that of the global average. • CO 2 consumption rate is higher than most of major global major rivers. • CO 2 consumption in the basin is about 0.41% of the global annual consumption. • Runoff and lithology are the major controlling factors of chemical weathering. Abstract Chemical weathering of continents is one of the major geochemical processes which consumes atmospheric CO 2 and exerts a strong impact on the global climate. The major ion chemistry of the Mahanadi river basin, one of the largest river basins in India, is determined to investigate the sources of major ions and their spatio-temporal variability, chemical weathering rates and associated CO 2 consumption in the basin. The results reveal that the ions in the basin are dominated by Ca and HCO 3. The total dissolved solids (215 mg L−1 in monsoon and 270 mg L−1 in pre-monsoon) and total cation concentration (2367 µEq in monsoon and 3214 µEq in pre-monsoon) in the basin are relatively higher than the global average. The dissolved loads in the basin are dominantly controlled by rock weathering particularly chemical weathering of silicates and carbonates. The estimated chemical weathering rates based on the forward model are 44.94 t km−2 yr−1 in monsoon and 2.45 t km−2 yr−1 in pre-monsoon with annual average chemical weathering rate of 23.7 t km−2 yr−1. The contribution of silicate weathering rates in the basin is 32 and 1.55 t km−2 y−1 during monsoon and pre-monsoon period respectively. The estimated CO 2 consumption rate associated with chemical weathering in the basin is 13.3 × 105 mol km−2 yr−1 during monsoon and 0.66 × 105 mol km−2 yr−1 during pre-monsoon period with an average annual rate of 6.9 × 105 mol km−2 yr−1 which is higher than the global average. The net rate of CO 2 consumption by silicate weathering is estimated to be approximately 4.78 × 105 mol km−2 yr−1. It is observed that the runoff and lithology are the major factors influencing chemical weathering in the basin. However, the basin elevation has a good negative correlation with chemical weathering rate. [ABSTRACT FROM AUTHOR]

Chemico-mineralogical attributes of authigenic clays associated with the altered volcanic tuffs that occur in the Palaeoproterozoic Porcellanite Formation contain evidences of hydrothermal alteration and diagenetic processes in a marine environment. Previous sedimentological and geochemical studies on Porcellanite Formation were restricted to the Chopan area, but, the details related to provenance, nature and source of volcanism archived in these clays have not been ascertained. In order to understand these aspects, present study on these authigenic clays were carried out. Clay minerals represent dominance of illite with subordinate amount of montmorillonite. Moreover, low abundance of kaolinite is also noticed. The illite fibers and plates associated with the kaolinite indicate illitization. The kaolinite to illite transformation is favoured by incorporation of K+ ions, derived from the K-feldspar dissolution and its overgrowth. Major oxide contents of these clays and their ratios when plotted over diagrams marked with standard illite, kaolinite, smectite and chlorite compositional fields show clustering within or close to the illite field. Thermodynamic components calculated for these clays when plotted over AR 2 3+AlSi 3 O 10 (OH) 2 − R 2 3+Si 4 O 10 (OH) 2 − AR2+R3+Si 4 O 10 (OH) 2 ternary diagram, data plots lie within the illite, mixed layer I/S and smectite fields. Binary major oxide data plots between bulk rock and authigenic clay compositions showed felsic affinity. Montmorillonite and illite predominated in the eastern and western marginal areas of the Vindhyan Basin, respectively. However, former resulted from the hydrothermal alteration of volcanic glass associated with the ferruginous breccia and altered tuffs and remnants of the volcanic vents, whereas, later is associated with the tuffaceous beds. Owing to the adsorption, Ba, Rb and Sr is enriched in clays comparing to the bulk rock composition. Low (< 15 ppm) Sc values suggested major contribution from the felsic component. Also, low Rb/Sr and Th/U values revealed moderate insitu weathering. The dominance of K-feldspar alteration and insitu weathering is also evident from clustering of clay data plots in the A-CN-K ternary diagram. Pronounced negative Eu anomaly together with higher LREE/HREE values associated with these clay minerals implied proximity to source and their possible derivation from the silicified felsic tuffs available in the provenance. [ABSTRACT FROM AUTHOR]

A study has been carried out in KT (Cretaceous-Tertiary) boundary along the contact zones of hard rock, limestone and sedimentary formations to discern the geochemical processes governing the groundwater chemistry. A total of sixty-three groundwater samples were collected from the handpumps covering the entire study area and measured for hydrochemical species. Principal component analysis of the hydrochemical data inferred three major processes governing the geochemistry of the groundwater of the region as leaching, ion exchange and weathering. It was also inferred that there are few samples depicting the mixtures of these processes (what are they mention it) and few samples not representing any of these processes with adequate statistical significance. Hence, in order to know the geochemical behaviour of the samples representing each process, their combinations along with the samples which are not- representative samples of these processes were inferred using various standards plots to get an insight into their geochemical characteristics and affinity. This also inferred the samples representing different processes have a significant signature of geochemical facies. The major ions and the stable isotopes of groundwater were used to understand these processes. The carbonate and sulphate saturation states of these samples were calculated by PHREEQC and compared with major variations with the identified three geochemical processes. The state of saturation of Halite, Anhydrite, Gypsum, Aragonite, Dolomite, Calcite, Talc and Chrysolite were determined in all the samples. Inverse modeling was carried out considering the non-representative samples as initial solution and the samples representing each factor as final solution to understand the phase mole transfer in each process. An attempt was also made in this study to compare the geochemical behaviour of groundwaters from different KT boundaries. The samples representing these processes were plotted on an integrated map representing lithology, lineaments, drainage and elevation to determine their interrelationships. The study groups the samples into anthropogenic or geogenic. The leaching process is controlled by lithology and landuse, ion exchange processes is influenced by lithology and drainage patterns whereas weathering processes were controlled by lithology, drainage and lineaments. Non representation of samples (NRS) were mainly controlled by drainage and lineaments of the region. [ABSTRACT FROM AUTHOR]

Highlights • First attempt to identify the PETM in a NW Himalayan section (basal Subathu Group). • Key results include 3.4‰ CIE, abundance of Apectodinium , and dissolution of foraminiferids. • Increase in quartz and phyllosilicates and decrease in carbonates noted across the probable PETM. • Intense weathering, 85-89% CIA, <1% TOC, siliciclastic influx, and REE enrichment. • Dataset very close to the PETM and even reflects its probable onset and peak phases. Abstract The Paleocene–Eocene Thermal Maximum (PETM) is one of the most pronounced and widely documented global warming events in the geological history that occurred at the beginning of the Eocene (∼56 Ma) causing substantial changes in biota and geochemistry. It is marked worldwide by a negative isotopic excursion of δ13C. The biotic changes associated with the PETM in marine realm include bloom of the dinoflagellate Apectodinium , turnover of larger foraminiferids, diversification of planktic foraminiferids, and carbonate dissolution of calcareous test shells, etc. while the geochemical changes include decrease in carbonates and increase in abundance of silicates and phyllosilicates, etc. Conspicuously, there has been no attempt to identify the PETM in the Himalaya even though some Himalayan sections are known to have Paleocene–Eocene transition beds. To fill this lacuna, we investigated the basal part of the late Paleocene–middle Eocene Subathu Group exposed at the village Kurla near Subathu in Himachal Pradesh (NW sub-Himalaya) for biotic, mineralogical, and geochemical signatures of this abrupt warming event. The significant results of this study include carbon isotope excursion (CIE) of 3.4‰, occurrence of index dinoflagellate genus Apectodinium , and carbonate dissolution of the larger benthic foraminiferids. The mineralogical changes noted across the Paleocene − Eocene transition include increase in quartz and phyllosilicates and decrease in carbonates. The geochemical changes include (i) increase in SiO 2, Al 2 O 3 , K 2 O, and Fe 2 O 3 , (ii) decrease in CaCO 3 , (iii) decreasing trend of Si/Al, Fe/Al, and Mg/Al ratios, (iv) increasing trend of K/Al, Ti/Al, and Zr/Al ratios, (v) changes in trace element abundance, (vi) maximum chemical index of alteration (CIA) of 85–89%, and (vii) increase in abundance of rare earth elements. The aforementioned dataset is clearly very close to the PETM and even reflects its probable onset and peak phases, however, it is insufficient to definitively identify the PETM in the studied section. Nevertheless, since this study is the first from a Himalayan section and brings out considerable new information, all results and interpretations are presented and discussed here. [ABSTRACT FROM AUTHOR]

The present study is an attempt to investigate the regional topography and drainage dynamics of the Khurar River, central India, along with the textural, mineralogical, and geochemical behaviour of the bedload sediments. The morphometric analysis was carried out using SRTM data with the help of ArcGIS 10 software. The area of the basin is 309.57 km2 with its perimeter 83.24 km and maximum length 32.06 km. Drainage patterns are dendritic to subdendritic with stream orders ranging from first to third order. Drainage density is 0.34 per km2, while the bifurcation ratio is 4.5 for the river. The Khurar River Basin is an elongated basin of small size showing ENE‐WSW trend analogous to the Son lineament. This basin might have originated during the Quaternary Period as a result of major tectonic activities in the region. The textural analysis indicates that the samples are bimodal to polymodal in nature ranging from very coarse to coarse grained and poorly to moderately well sorted in all the geomorphic units. The skewness value suggests coarse to fine‐skewed values, while kurtosis value shows platykurtic to very leptokurtic nature of the sediments. The quartz, microcline, and albite are the chief minerals in the sediment samples with negligible variation from source to confluence of the river. The major oxide geochemistry of the sediments indicate that the dominant oxide is SiO2 followed by Al2O3 and other oxides that suggests felsic‐dominated source for the sediments. The chemical index of alteration (CIA), plagioclase index of alteration (PIA), chemical index of weathering (CIW), weathering index of Parker (WIP), Vogt S. residual index (V), Ruxton ratio (R), and silica‐titania index (STI) reveal moderate weathering conditions and immature nature of the sediments in the basin. These suggest that the sediments experienced a moderate amount of weathering in the river catchment under subhumid climatic conditions. [ABSTRACT FROM AUTHOR]

Detailed reconstruction of Indian summer monsoons is necessary to better understand the late Quaternary climate history of the Bay of Bengal and Indian peninsula. We established a chronostratigraphy for a sediment core from Hole 19B in the western Bay of Bengal, extending to approximately 80 kyr BP and examined major and trace element compositions and clay mineral components of the sediments. Higher δ18O values, lower TiO2 contents, and weaker weathering in the sediment source area during marine isotope stages (MIS) 2 and 4 compared to MIS 1, 3, and 5 are explained by increased Indian summer monsoonal precipitation and river discharge around the western Bay of Bengal. Clay mineral and chemical components indicate a felsic sediment source, suggesting the Precambrian gneissic complex of the eastern Indian peninsula as the dominant sediment source at this site since 80 kyr. Trace element ratios (Cr/Th, Th/Sc, Th/Co, La/Cr, and Eu/Eu*) indicate increased sediment contributions from mafic rocks during MIS 2 and 4. We interpret these results as reflecting the changing influences of the eastern and western branches of the Indian summer monsoon and a greater decrease in rainfall in the eastern and northeastern parts of the Indian peninsula than in the western part during MIS 2 and 4. Key Points: The sedimentation rate was estimated for a sediment core from Hole 19B in the western Bay of Bengal, extending to approximately 80 kyr BPIndian monsoonal fluctuations on glacial‐interglacial time scale implied from chemical and mineral propertiesTrace element ratios reflect changing in influences of the eastern and western branches of the Indian summer monsoon [ABSTRACT FROM AUTHOR]

• Studied forests in Western Ghats had weathered and mature profiles of Ultisols. • Abundance of 2:1 and mixed layer minerals in natural forests than plantation. • Co-dominance of gibbsite with 2:1 minerals discounts the antigibbsite hypothesis. • Losses of SiO 2 in the non-clay fractions indicate active weathering in all horizons. • Clay formation assessments provide insights into ecosystem regulated pedogenesis. Clay minerals formed during soil formation are imprints of ecosystem functioning and pedogenic processes in landscapes. The study evaluated the variations in taxonomy, soil weathering and pedogenic changes in contrasting forest soils in the Southern Western Ghats, India. Three different forest systems with comparable soil-forming factors vis-a-vis evergreen, moist deciduous and a man-made system (rubber plantation) were evaluated for physical, chemical, morphological, and pedogenic characteristics of the related soils. Soil profiles were dug up to 1.50 m in the selected ecosystems and horizon-wise soil samples were collected. All the pedons were classified in the soil order of Ultisols and subclassified as Ustic Palehumult (evergreen forest), Ustic Haplohumult (moist deciduous forest) and Typic Haplustult (rubber plantation), respectively. The soil pH was found to be acidic in all the ecosystems ranging from 4.6 to 5.8. Chlorite, hydroxyl interlayered vermiculite (HIV), mica, kaolinite, feldspars, gibbsite and quartz dominated the mineral assemblages in the clay fractions of soils of natural forest systems. The losses of SiO 2 in the non-clay fraction and corresponding enrichment of the component in the clay-sized fraction in all horizons indicated an active continuous weathering process in all the systems of this region. Clay accumulation by way of formation and translocation was highest in the lower horizons of the soils of evergreen (Bt2 at a depth range of 28–57 cm) and moist deciduous (Bt3C at a depth range of 23–150 cm) forest, whereas it was highest at Bt1 at a depth range of 15–28 cm in the plantation soil. The depth variations in the clay formations in natural and manmade forest systems provide insights into ecosystems regulated profile development under natural and man-made systems in the humid tropics, a vital information gap hitherto in soil pedogenesis of the humid tropics. Such pedogenic assessments along with the factors responsible for such modifications would provide important inputs in developing soil health management strategies in the humid tropics. [ABSTRACT FROM AUTHOR]

Recently published findings indicate that the Ordovician period has been much more dynamic than previously anticipated thus making this period significant in geological time. The Ordovician of India can best be studied in the Spiti region because the Spiti basin records the complete uninterrupted history of excellent marine sedimentary rocks starting from Cambrian to Paleogene which were deposited along the northern margin of India. Due to these reasons the geochemical data on the Ordovician rocks from the Spiti region is uncommon. The present geochemical study on the Ordovician Thango Formation (Sanugba Group) is mainly aimed to understand the provenance and the paleoclimatic conditions. The sandstones are the dominant lithology of the Thango Formation with intercalations of minor amount of shales. Detailed petrographic and sedimentological analysis of these rocks suggest that three major depositional environments, viz., fluvial, transitional and marine prevailed in the basin representing transgressive and regressive phases. The major and trace element ratios such as SiO2/Al2O3, K2O/Na2O and La-Th- Sc discrimination diagram suggest that these rocks were deposited in passive margin tectonic settings. Various geochemical discriminants and elemental ratios such as K 2 O/Na 2 O, Al 2 O 3 /TiO 2 , La/Sc, Th/Sc, Cr/Th, Zr/Sc, (Gd/Yb) N and pronounced negative Eu anomalies indicate the rocks to be the product of weathering of post-Archean granites. The striking similarities of the multi-elemental spider diagrams of the studied sediments and the Himalayan granitoids indicate that sediments are sourced from the Proterozoic orogenic belts of the Himalayan region. Chemical index of alteration (CIA) values of the studied sediments (55–72) suggest that the source rocks underwent low to moderate degree of chemical weathering. The span of the CIA values (55–72) recorded in the sediments from the Spiti region may have resulted from varying degrees of weathering conditions in the source area. This, in turn, reflects variable climatic conditions prevailing during the Ordovician period, which is consistent with the global studies. The high CIA values observed by numerous studies on siliciclastic sediments may imply warm paleoclimate attributed to an increase in atmospheric carbon dioxide and/or methane levels inducing an acidic weathering environment and enhanced silicate weathering. While the low CIA values indicates prevalence of arid-glacial conditions where negligible chemical alteration is possible. This study documents the noteworthy events like fluctuating (rise and fall) atmospheric CO 2 and sea levels during the Ordovician period, a conclusion which is consistent with the other such studies on the Phanerozoic glaciation (or mass extinction) events on Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

This study assessed the fluoride (F−) pollution in groundwater samples (n = 170) of tribal regions around Bailadila Iron Ore Mines [BIOM] Complex of Dantewada District, India. Weathering of carbonate and silicate clays were important geogenic sources of dissolved ions. A Piper diagram showed a Ca–HCO3 water type, with positive chloro-alkaline indices illustrating the occurrence of direct base-exchange reactions. The F− concentrations varied from 0.08 to 1.95 mg L−1 with a mean value of 0.9 ± 0.3 mg L−1. Only two groundwater samples showed F− concentrations > 1.5 mg L−1, the drinking water guideline established by the World Health Organization (WHO) and Bureau of Indian Standards (BIS). Factor analysis showed high loadings of HCO3− and F−, indicating alkaline conditions, favoring the dissolution of F− in the groundwater. The Kfluor value is less than 10−10.6, indicating that the dissociation of fluorite is very slow. As a result, groundwater locations were under-saturated with respect to fluorite. [ABSTRACT FROM AUTHOR]

Abstract: It is crucial to understand lateral differences in paleoclimate and weathering in order to fully understand the evolution of the Himalayan mountain belt. While many studies have focused on the western and central Himalaya, the eastern Himalaya remains poorly studied with regard to paleoclimate and past weathering history. Here, we present a multi‐proxy study on the Mio‐Pliocene sedimentary foreland‐basin section along the Kameng River in Arunachal Pradesh, northeast India, in order to obtain better insight in the weathering history of the eastern Himalaya. We analysed a continuous sedimentary record over the last 13 Ma. Heavy‐mineral and petrography data give insight into diagenesis and provenance, showing that the older part of the section is influenced by diagenesis and that sediments were not only deposited by a large Trans‐Himalayan river and the palaeo‐Kameng river, but also by smaller local tributaries. By taking into account changes in diagenesis and provenance, results of clay mineralogy and major element analysis show an overall increase in weathering intensity over time, with a remarkable change between ca. 10 and ca. 8 Ma. [ABSTRACT FROM AUTHOR]

We study the silicon biogeochemical cycle and its associated parameters in 24 and 18 Indian estuaries during dry and wet periods respectively. We focus more specifically on dissolved Si (DSi), amorphous Si (ASi,) lithogenic Si (LSi), Particulate Organic Carbon (POC), Total Suspended Material (TSM), Dissolved Inorganic Nitrogen (DIN), salinity and fucoxanthin, a marker pigment for diatoms. Overall, we show that the estuaries have strong inter and intra variability of their biogeochemical parameters both seasonally and along salinity gradients. Based on Principal Component Analysis and clustering of categorised (upper and lower) estuaries, we discuss the four major processes controlling the Si variability of Indian estuaries: 1) lithogenic supply, 2) diatom uptake, 3) mixing of sea water and, 4) land use. The influence of lithogenic control is significantly higher during the wet period than during the dry period, due to a higher particle supply through monsoonal discharge. A significant diatom uptake is only identified in the estuaries during dry period. By taking into account the non-conservative nature of Si and by extrapolating our results, we estimate the fluxes from the Indian subcontinent of DSi, ASi, LSi to the Bay of Bengal (211 ± 32, 10 ± 4.7, 2028 ± 317 Gmol) and Arabian Sea (80 ± 15, 7 ± 1.1, 1717 ± 932 Gmol). We show the impact of land use in watersheds with higher levels of agricultural activity amplifies the supply of Si to the coastal Bay of Bengal during the wet season. In contrast, forest cover and steep slopes cause less Si supply to the Arabian Sea by restricting erosion when entering the estuary. Finally, Si:N ratios show that nitrogen is always in deficit relative to silicon for diatom growth, these high Si:N ratios likely contribute to the prevention of eutrophication in the Indian estuaries and coastal sea. [ABSTRACT FROM AUTHOR]

The 1967 M6.3 earthquake near the Koyna dam produced a surface rupture zone following a NNE-SSW structural trend. The rupture zone is documented in a report by the officers of the Geological Survey of India (GSI, 1968). The surface expressions of the rupture comprising fissures, en-echelon fractures, oblique or diagonal tensional cracks and mole tracks, termed here as the Koyna Fissure Zone (KFZ), were reported over a limited area, about 1000m in length and 200 m in width, located to the southeast of the Koyna dam between Donichawadi and Kadoli. The Koyna region was revisited recently for investigating the fissures, to help in locating potential sites for scientific deep drilling. Most of the reported surface deformation features are obliterated due to intense weathering and laterization of the exposed basalt surface during the past 48 years. However, careful field investigations in the Donichawadi-Kadoli area as well as in the surrounding region show that fissures and fractures are still preserved at several locations. The fissures trend between N30°W to N50°E, similar to that reported previously. The mean orientation of these fissures is 25°/89°-E. Transposition of one set of fissures by another set provide strong evidence for repeated brittle deformation in the area. Physical and microstructural studies on core samples of granite-gneiss basement rock underlying Deccan basalt in the area, obtained from a 1522 m deep borehole at Rasati, confirm the extension of the surface fissures to depth. Occurrences of secondary mineralization along these fissures indicate the percolation of water through fractures within basement granitoids. The evidences for water channelization may have direct implications for the occurrence of reservoir triggered earthquakes in the Koyna region for the past five decades. [ABSTRACT FROM AUTHOR]

The bar-top sediments at the Tons river deposited mainly from the suspension current during waning stage condition of river are collected to study their provenance on the basis of clay mineralogy, heavy minerals and magnetic properties. The clay mineral assemblages in samples predominantly consist of illite, with minor amounts of kaolinite, smectite and chlorite. The clay minerals are contributed due to (i) weathering and decomposition of shales, argillaceous limestones and pyroclastic deposits of upper Vindhyan Groups and (ii) weathering and erosion of Banda plain of Gangetic alluvium. The low ZTR index for the studied samples indicates poor sediment maturity, rapid erosion in the source region and short transportation of detritus. The transparent heavy mineral assemblages in the sediment samples predominantly consist of garnet, with minor amounts of tourmaline, zircon, hornblende, enstatite, hypersthene, rutile, tremolite, kyanite, sillimanite, andalusite, chlorite, epidote, wollastonite, and staurolite. The heavy minerals are dominantly angular to sub-angular with some rounded to sub-rounded grains. The rounded grains indicate multicyclicity and derivation fromVindhyan sandstones. The angular grains are either contributed due to erosion of primary rocks of Bundelkhand gneissic complex and or various Gangetic alluviums. The magnetic properties from sediment samples indicate that the antiferromagnetic minerals (illite, chlorite and smectite) are more concentrated in clay sized particles and it also indicated mixed source rocks for the bar-top sediment of Tons river. [ABSTRACT FROM AUTHOR]

More and more primary metal production and processing units are being shifted away from the developed countries to the developing countries. India is poised to become one of the largest producers of metals after China. This poses its own challenges in terms of solid waste management. As far as the production of primary metals are concerned, steel industries produce the largest amount of solid wastes. India has rich deposits of haematite. Because of high alumina content and inferior coke quality, approximately 1.6 tons of solid wastes are generated per ton of the steel produced. Most of the Blast Furnace slag is granulated and is used for manufacturing cement. However, steel making slag that contains high amounts of Fe poses challenges. This paper discusses the issues pertaining to solid waste generation from iron and steel making processes in terms of volumes, challenges and efforts towards recycling and utilization. [ABSTRACT FROM PUBLISHER]

The Kukkal basin, Tamil Nadu, India, receives most of its rain from the southwest monsoon (SWM). A sediment core from Kukkal Lake preserves a continuous sediment record from the early-Holocene to present (9000 yr BP to present). The present lake is situated at an elevation of ~1887 m a.s.l., in a small basin that appears to have alternated between a and wetland depositional environment. Climate proxies, including sediment texture, total organic carbon (TOC), total nitrogen (TN), C/N, pollen and geochemical composition indicate a steady progression to wetter conditions, with two stepwise changes at about 8000, and between 3200 and 1800 yr BP. The change at 8000 yr BP appears to correspond to a brief (100–150 years) dry spell recorded elsewhere in India. The change at 3200–1800 yr BP consisted in a rapid intensification of the SWM, and may correlate with the initiation of the ‘Roman Warm Period’. There is no clear evidence of changes at the times of the ‘Medieval Warm Period’ (‘MWP’) and the ‘Little Ice Age’ (‘LIA’). The C/N ratio of the sediments ranges from 14.02 to 8.31, indicating that the organic matter originated from a mixture of lacustrine algae, vascular and terrestrial plants. Chemical weathering indices (Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA)) are consistent with extreme silicate weathering. Pollen data show a development from savanna vegetation prior to about 8000 yr BP, followed by grassland with palms, the appearance of ferns just prior to 3200 yr BP and the establishment of the tropical humid forest between 3200 and about 1800 yr BP. [ABSTRACT FROM AUTHOR]

Physico-chemical groundwater (GW) parameters were evaluated to understand the hydrogeochemical processes in the Siwalik plains of Jammu and Kashmir, India. During the 2012-2013 post-monsoon (POM) and pre-monsoon (PRM) seasons, GW samples ( n = 207) from deep bore wells and shallow open wells were chemically analysed. Cations (Ca, Mg, Na, K and Fe) and anions (HCO , Cl, SO and F) showed a wide spatio-temporal variation. Results suggest that weathering and dissolution of carbonates and silicate rocks is the main source of water mineralization. The major hydrochemical facies is characterized by Ca-Mg-HCO and Ca-HCO during the PRM and POM seasons respectively. The presence of sulphate-bearing water in a large number of the samples indicates a significant role of gypsum dissolution and anthropogenic contamination of the GW. Factor analysis (FA) and hierarchical cluster analysis (HCA) revealed that the variability of hydrochemistry is mainly related to rock-water interaction, dissolution of carbonates and other lithological units as well as the influence of anthropogenic activities in the area. Overall, it was found that the GW quality is within the limits of human consumption. The higher concentration of a few chemicals indicates an increasing trend of industrial contamination of the GW. For sustainable development of the portable GW in Siwaliks, it is necessary to minimize the adverse impacts of the anthropogenic and industrial contamination on the GW resources through best management practices and prevent its further contamination to a level that could make GW unsuitable for human uses. [ABSTRACT FROM AUTHOR]

The Ganges river system is responsible for the transportation of a large flux of dissolved materials derived from Himalayan weathering to the oceans. Silicate weathering-driven cooling resulting from uplift of the Himalayas has been proposed to be a key player in Cenozoic climate variation. This study has analysed Li isotope (δ 7 Li) ratios from over 50 Ganges river waters and sediments, in order to trace silicate weathering processes. Sediments have δ 7 Li of ∼0‰, identical to bulk continental crust, however suspended sediment depth profiles do not display variations associated with grain size that have been observed in other large river systems. Dissolved δ 7 Li are low (∼11‰) in the Ganges headwaters, but reach a constant value of 21 ± 1.6‰ within a relatively short distance downstream, which is then maintained for almost 2000 km to the Ganges mouth. Given that Li isotopes are controlled by the ratio of primary mineral dissolution to secondary mineral formation, this suggests that the Ganges floodplain is at steady-state in terms of these processes for most of its length. Low δ 7 Li in the mountainous regions suggest silicate weathering is therefore at its most congruent where uplift and fresh silicate exposure rates are high. However, there is no correlation between δ 7 Li and the silicate weathering rate in these rivers, suggesting that Li isotopes cannot be used as a weathering-rate tracer, although they do inform on weathering congruency and intensity. The close-to-constant δ 7 Li values for the final 2000 km of Ganges flow also suggest that once the size of the alluvial plain reached more than ∼500 km (the flow distance after which riverine δ 7 Li stops varying), the Ganges exerted little influence on the changing Cenozoic seawater δ 7 Li, because riverine δ 7 Li attained a near steady-state composition. [ABSTRACT FROM AUTHOR]