Tropical rivers are widely recognized as major sources of CO2 efflux, driven by a combination of natural processes and human-induced activities, a pattern expected to hold true for tropical biodiversity hotspots as well. This study provides baseline data for one of the world's most densely populated biodiversity hotspots, the Western Ghats (WG), through conventional sampling and analysis of small-scale rivers across the region and data driven approach. Results reveal persistent supersaturation of partial pressure of CO2 (pCO(2)) along with enriched stable isotopic composition of dissolved inorganic carbon (delta C-13(DIC); ranging -6.42 parts per thousand to -14.85 parts per thousand and -4.49 parts per thousand to -11.54 parts per thousand during monsoon and post-monsoon, periods). The consistently enrichment of delta C-13(DIC) (>-18 parts per thousand) indicating that diffusion of atmospheric CO2 into surface soils is the dominant source for DIC and driving intense chemical weathering in WG catchments, irrespective of season. The WG's strong chemical weathering potential, coupled with substantial CO2 uptake from its dense tropical forests, makes it one of India's most important regions for natural carbon sequestration. These findings highlight the urgent need for comprehensive assessments of CO2 sources and sinks, while emphasizing the importance of advancing research on enhanced chemical weathering and conserving this pristine yet densely populated biodiversity hotspot.

In this study, naturally occurring jarosite samples from Kachchh India (considered to be Martian analogue) were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Cathodoluminescence- Energy Dispersive X-ray Spectroscopy (CL-EDXS) and luminescence (thermoluminescence (TL), blue and infrared stimulated luminescence (BSL and IRSL) methods. FTIR and CL-EDXS studies suggested that jarosite preserves its luminescence characteristics even after annealing the samples to 450°C. This facilitated luminescence studies (TL/BSL/IRSL) to assess the potential use of luminescence-dating methods to establish chronology of jarosite formation or its transport. Jarosite exhibited TL, BSL and IRSL signals with varied sensitivities. The TL glow curve of jarosite comprises peaks at 100, 150, 300 and 350°C, reproducible under multiple readout cycles. The least bleachable peak at 350°C reduced to (1/e)th of its peak intensity (i.e. 36%) with ~100 minutes of exposure under a sun lamp. BSL and IRSL optical decay signals comprised three components. The signal exhibited athermal fading of g ~ 6 %/decade, but pIRIR signal at 225°C showed a near zero fading. The saturation doses ranged from 700 Gy to 2600 Gy for different signals, which suggest a dating range of 25 ka using a reported Martian total dose rate of 65 Gy/ka primarily due to cosmic rays. Multiple TL peaks and their widely differing stability also offer promise to discern changes in cosmic ray fluxes over century to millennia time scale through inverse modelling and laboratory experiments

The Kota-Pawalgarh Dun is a Half-Dun structure shaped by spatial variation in active deformation partitioning within the Main Boundary Thrust (MBT)-Himalayan Frontal Thrust (HFT) wedge in the Central Kumaun Himalayan front. The post-Siwalik Piedmont fans consist of Dun gravels and provide a geomorphic and stratigraphic constraint on the deformation partitioning on the Dun. Though the fans were mapped, the lack of ages failed to constrain the definition of their stratigraphic and structural significance in the Late Quaternary evolution of the Dun. We present the new mapping results using field and remote sensing data with chronological constraints from the Optically Stimulated Luminescence (OSL) dating of river terraces and alluvial fans across the Dun valley. These new OSL ages of the fan and terrace sediments, in addition to published dates, reveal multiple phases of fan aggradation since > 90 ka until similar to 19 ka and incision during the Holocene with differential uplift, fan truncation, and fluvial reorganization, driven by ongoing tectonic activity. These findings offer valuable insight into the neotectonic development of the Kota Dun valley and contribute to a better understanding of the deformation processes in the mountain front in the Himalaya Central Seismic Gap region.

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This study examined the influence of fireworks on atmospheric aerosols over the Southern Indian city of Hyderabad during festival of Diwali using mass closure, stable carbon isotopes and the EPA-PMF model. Identification of chemical species in day and night time aerosol samples for 2019 and 2020 Diwali weeks showed increased concentrations of NH4+, NO3-, SO42-, K+, organic carbon (OC), Ba, Pb and Li, which were considered as tracers for fireworks. PM10 source apportionment was done using inorganic (trace elements, major ions) and carbonaceous (organic and elemental carbon; OC & EC) constituents, along with stable isotopic compositions of TC and EC. K+/Na+ ∼1 and K+nss/OC > 0.5 indicated contribution from fireworks. High NO3-, NH4+, Na+, Cl- and SO42- suggested the presence of deliquescent salts NaCl, NH4NO3 and (NH4)2SO4. TAE/TCE >1 suggested H+ exclusion, indicating possible presence of H2SO4 and NH4HSO4 in the aerosols. Ba, Pb, Sb, Sr and Fe increased by 305 (87), 12 (11), 12 (3), 3 (2) and 3 (4) times on Diwali nights, compared to pre-Diwali of 2019 (2020), and are considered as metallic tracers of fireworks. δ13CTC and δ13CEC in aerosols closely resembled that of diesel and C3 plant burning emissions, with meagre contribution from firecrackers during Diwali period. The δ13CEC was relatively depleted than δ13CTC and δ13COC. For both years, δ13COC-EC (δ13COC - δ13CEC) were positive, suggesting photochemical aging of aerosols during long-range transport, while for pre-Diwali 2019 and post-Diwali 2020, δ13COC-EC were negative with high OC/EC ratio, implying secondary organic aerosols formation. High toluene during Diwali week contributed to fresh SOA formation, which reacted with precursor 12C, leading to 13C depletions. Eight-factored EPA-PMF source apportionment indicated highest contribution from residue/waste burning, followed by marine/dust soil and fireworks, while least was contributed from solid fuel/coal combustion.

In this study, the distribution of dissolved inorganic nitrogen (DIN), phosphorus (DIP), and silicate (DSi) in surface waters of 70 coastal rivers in India's Western Ghats (WG) has been determined. The nutrient concentrations in individual rivers appear to be influenced by catchment geology, land use, and climate. The entire WG region contributes 0.31 Tg of DIN, 0.03 Tg of DIP, and 5.65 Tg of DSi annually to the coastal Arabian Sea. The annual ratios of N:P, Si:N, and Si:P suggest that most of these rivers are limited by P rather than N, and there is an excess supply of Si, primarily from natural sources. P limitation is severe during monsoon periods, while N limitation is observed in the Deccan Traps region. The annual export of 0.31 Tg of DIN from WG rivers could support 2.05 Tg of carbon (new production) on the Arabian Sea coast, indicating that the riverine export of DIN can significantly remove atmospheric CO2 through biological pumps in the Arabian Sea. The study also confirms that the excess input of Si from natural processes relative to the anthropogenic supply of limited P and N further supports the idea that riverine nutrient inputs from small west-flowing tropical mountainous rivers do not contribute to coastal eutrophication along the Eastern Arabian Sea coast.

Surajkund Formation of Central Narmada Basin exhibits fining upward sequences of pebbly conglomerate, coarse-fine grained sandstone, siltstone and association of seven lithofacies, namely massive pebbly conglomerate, coarse-medium grained sandstone with large scale tabular cross bedding, massive coarse grained sandstone, coarse to medium grained sandstone with horizontal parallel bedding, fine grained sandstone with parallel lamination, fine grained sandstone with ripple lamination and siltstone, indicates their deposition in mixed load meandering river. Granulometric studies of Surajkund sediments also support the fluvial depositional environment. Soft sediment deformation structures documented in the siltstones suggest sediment liquification due to earthquake shocks. Abundant development of nodular, bedded calcretes and rhizoliths within these sediments are indicative of semi-arid climate and related subaerial exposure. These sediments are prominently lithic arenites, and clay mineralogy as well as geochemistry indicate deposition in the proximity of source, short distance of transport and mixed provenance of a variety of pre-Quaternary rocks such as Precambrian metamorphic rocks and granites, Vindhyan and Gondwana Supergroups, Deccan Trap basalt and laterite. Evidences of fresh water phreatic as well as vadose zone diagenesis linked to the semi-arid climatic conditions, together with subaerial exposure of these sediments, are seen in thin sections, which are supported by δ13C (av. −5.67

This paper describes the existence of high salinity in an inland aquifer system of a limited extent located in the granitic terrain of south India. Salinity levels observed in 55 water samples collected pre- and post-monsoon are discussed. Limited repeat sampling during the two seasons shows no significant change in hydrochemistry, probably due to the prevailing drought conditions during the study period (2017–18). As per the salinity classification based on total dissolved solids (TDS), only one sample indicates freshwater while 40

This study is carried out to understand the degree of soil pollution, transport mechanism, and distribution pattern of potentially toxic elements (PTEs), including the exposure effects on human health. Towards this, topsoil samples were collected from the Saman wetland and surrounding agricultural fields in the Gangetic plain, India. The results show that the mean concentration of Cu, Hg, Zn, Pb, Th, As, U, and Cd of both soil types exceed the natural background values. The multivariate analysis suggests the soils are moderately contaminated with As, Cd, Zn, Pb, and Hg (possibly from anthropogenic sources) and heavily contaminated with Th and U, likely ascended from geogenic sources. The GIS-based geostatistical plots coupled with principal component analysis (PCA) and hierarchical cluster analysis (HCA) apportion the sources of these toxic elements, which vary greatly and are closely correlated to the geogenic processes and local anthropogenic sources like pesticides and agrochemicals. The health risk assessment revealed that the cumulative hazard index ( HI ) values of PTEs are lower than the safe level, suggesting no significant noncarcinogenic effect for adults and children. However, excess cancer risk ( ECR ) values exceed the permissible limit (1 × 10 −6 ), signifying that exposure to the toxic element concentration may cause cancer in the exposed population, most probably in the children subpopulation. Thus, this study highlights the importance of local compliance, ensuring the quality checks and management policies in using pesticides and other agrochemicals containing PTEs to control the imposed cancer risks.

In the Precambrian granitic terrain, the occurrence of a multi-aquifer system is common. This study has examined the inter-communications between the shallow and deep aquifers using the hydrochemical and isotopic methods. The obtained results indicate distinct hydrochemical characters of the groundwater from shallow (~ 100 m) and deep (~ 400 m) wells, signifying their independent and unconnected nature initially. Hydrochemistry of deep groundwater is approximately constant (either Ca–Na–Cl or Ca–Na–Cl–SO4 type of water) from January 2015 to June 2016. Repeated measurements of the 14C activity in these deep groundwater samples during this period show 35.41 ± 0.48 to 85.01 ± 0.8 pMC (residence time of ~ 3 to 8 ky BP). However, as a result of excess rainfall during 2016, hydrochemical facies of the deep groundwater changed initially to Na–Ca–SO4–Cl. Subsequently, they stabilised at Ca–Na–HCO3–Cl type with a significant reduction in Cl− and increased HCO3− and NO3− concentrations, while the 14C activity changed to 100 pMC (modern age). These changes are attributed to the ingression of fresh water into the deep aquifer after paleo-groundwater in the deep aquifer is depleted due to the over-exploitation of the limited potential aquifer during the drought. The over-exploitation of deep aquifer possibly improved the migration potential of fresh water to the deep aquifer and led to enhancing the groundwater recharge during the excess rainfall years. It brings a new perspective to the hydrogeological dynamics between shallow and deep aquifers. Further, it also suggests that, under climate-driven drought conditions, deep aquifers could act as an emergent groundwater resource to meet the water demands. A conceptual model has been proposed to explain the observed phenomenon of deep and shallow aquifer communication.

Abstract This study is conducted in the Precambrian granitic terrain, to demonstrate the presence of the multi-aquifer system and examine the inter-communications between them. Distinct hydrochemical characters of the groundwater from shallow (~ 100 m) and deep (~ 400 m) wells, signifies their independent and unconnected nature initially. Hydrochemistry of deep groundwater is approximately constant (either Ca-Na-Cl or Ca-Na-Cl-SO4 type of water) during January 2015 to June 2016. Repeated carbon-14 measurements during the same period show the 14C activity of about 35 to 85 pMC (residence time about 3 to 8 ky BP). However, as a result of excess rainfall during 2016, hydrochemical facies of deep groundwater changed initially to Na-Ca-SO4-Cl and subsequently stabilised at Ca-Na-HCO3-Cl type with a drastic reduction in Cl and increased HCO3 and NO3 concentrations, while the 14C activity turned out to be to 100 pMC (modern age). These changes are attributed to ingression of fresh water into the deep aquifer, after paleo-groundwater depleted due to prolonged drought conditions along with the over-exploitation of limited potential deep aquifer. These drought and over-exploitation situations potentially improved the migration potential of fresh water to the deep aquifer and led to enhancing the groundwater recharge during the excess rainfall years. This brings a new perspective to the hydrogeological dynamics between shallow and deep groundwater. A conceptual model is proposed to explain the observed phenomenon. This study also suggests that, under climate driven drought conditions, deep aquifers could act as emergent groundwater resource to meet the water demands amid population growth.

CSIR-NGRI has developed pioneering facilty of the 14C and expertises to pursue paleoseismic and neotectonic studies aimed at building earthquake chronology from earthquake-prone regions in India. We present some academic accomplishments and a glimpse of some ongoing programs on the subject at CSIR-NGRI. The quest resulted in developing the paleo-earthquake catalog based on coseismic liquefaction studies from the Shillong region, which experienced the largest intra-plate (1897) earthquake in the Indian subcontinent. The exploration in other earthquake-affected areas brought comprehension to distinguish coseismic deformation features and processes in saturated sedimentary records to the aseismic structures. The paucity of datable samples for estimating the past earthquakes chronology led to improvising other techniques like paleomagnetic dating, the Optically stimulated luminescence (OSL) dating protocol for poorly bleached samples, and constraint from the archaeology have been incorporated. The effect of recurrent primary rupture in shaping the landscape and defining deformation partitioning using tectonic-geomorphology and earth surface process modeling are other evolving disciplines being pursued at CSIR-NGRI.

The present study provides surface water types and water quality indices (WQI) for 70 large coastal rivers of the Western Ghats (WG). Irrespective of seasons and lithology, concentration of cations (Ca2+ > Na+ > Mg2+ > K+) and anions (HCO3- > Cl− >SO42- > NO3- > PO43-) follow a typical trend all along the coast. The WG rivers can broadly be classified as calcium-bicarbonate-chloride (Ca2+-HCO3--Cl-) type. Pearson correlation analysis of major ions demonstrates natural sources influence on the riverine water composition across the WG region. Gibbs plot suggests water composition of these rivers is the result of the interaction of rock and precipitation. It means that ionic contributions from precipitation and chemical weathering of rock-forming minerals largely determine surface water quality. This biodiversity hotspot is facing high population pressure and anthropogenic activities. Despite it, quantitatively, all the physical parameters and chemical constituents are within the permissible limits of the World Health Organization (WHO) and Bureau of Indian Standards (BIS), thus making it suitable for drinking and domestic purposes. About 86% of the surface water samples are found to be suitable for irrigation (KR < 1) in non-monsoon seasons. Rivers near to Goa coast are only found unsuitable (KR > 1) for irrigation exclusively during non-monsoon seasons. From the majority of the calculated indices, it may be inferred that the river waters draining from the WG region are suitable for irrigation. Overall, the calculated WQI for studied rivers showed excellent to good water quality for drinking, agriculture, and aquatic life in monsoon seasons, which are then ranked from good to marginal in non-monsoon seasons.

Transport of organic carbon by small mountainous rivers is essential, but the poorly constrained component of the global carbon cycle. In the current research, we sampled and analyzed particulate organic carbon (POC) contents from 70 sizeable tropical coastal rivers, draining the Western Ghats (WG) of India. This study aimed to investigate the spatiotemporal variability in POC contents, to estimate flux and to identify environmental controls on POC sources and transport characteristics across the region. The averaged value of organic carbon (OC) in the particulate samples is 3.24%, and the mean POC concentration is 2.86 mg l(-1). We classified the samples based on total suspended matter (TSM) classes for source appropriation. Litter/riparian (42.5%) pools are the largest source of organic matter, followed by autochthonous (36%) and soil (21.5%) for the WG region. However, locally autochthonous sources contribute exceptionally to POC pools, indicating a favorable environmental condition for the growth of algae and phytoplankton. Land-use & land-cover, climate, topography, and sediment erosion seems to be determining the local variability in sources to POC pools and fluxes. The POC export rates suggest that within the region, the POC yields of the Deccan Trap (DT) and the Western Dharwar Craton (WDC) blocks are about two times higher than that of the Southern Granulite Terrain (SGT) region. With POC yield of 7.0 g m(-2) yr(-1), this region exports 0.79 Tg C (similar to 0.5% of the global POC) to the Arabian Sea annually. The POC flux of the WG region (covering 0.25% of Asia's land area) is approximately 1.0% of Asia's riverine POC flux to the ocean. (C) 2020 Elsevier B.V. All rights reserved.

Earth and Space Science Open Archive PosterOpen AccessYou are viewing the latest version by default [v1]Natural and Anthropogenic Influences on Nutrient Export from Tropical Mountainous Rivers into the Arabian SeaAuthorsKiran Kumar ReddyShiligireddyiDHarishGuptaDontireddyVenkatiDRama MohanKurakalvaiDDevenderKumariDSee all authors Kiran Kumar Reddy ShiligireddyiDCorresponding Author• Submitting AuthorNational Geophysical Research InstituteiDhttps://orcid.org/0000-0002-7209-0936view email addressThe email was not providedcopy email addressHarish GuptaOsmania Universityview email addressThe email was not providedcopy email addressDontireddy VenkatiDNational Geophysical Research InstituteiDhttps://orcid.org/0000-0001-8926-7868view email addressThe email was not providedcopy email addressRama Mohan KurakalvaiDNational Geophysical Research InstituteiDhttps://orcid.org/0000-0001-7199-7475view email addressThe email was not providedcopy email addressDevender KumariDNational Geophysical Research InstituteiDhttps://orcid.org/0000-0003-1634-808Xview email addressThe email was not providedcopy email address

The Ongole coastal dunefield (OCD) is about 20 km long and 2.5 to 3 km wide, and is located to the east of Ongole town between the mouth of the Paleru river in the south and a small creek in the north. Much of the dunefield lies 3–5 m above sea level with some large dune ridges reaching 10–12 m. The area landward of the dune field consists of an extensive marsh. Optically stimulated luminescence (OSL) dating of 12 sub-surface sediments from three sites near the western edge of the dunefield gives almost concurrent age of 5.1±0.4 ka. Radiocarbon dating of one shell from a similar location also corroborates the OSL age while the age of another shell taken closer from the modern shoreline gives a date of 3.29±0.5 ka. The age of the deposits and morphology of the dunefield indicate that it was probably initiated on some form of barrier system at the end of the Holocene transgression.

Baneta Formation, comprising of fining upward sequences of pebbly conglomerate, sandstone and siltstone, exhibits development of five distinct lithofacies, viz., massive pebbly conglomerate, large scale tabular cross bedded sandstone, horizontal parallel bedded coarse-grained sandstone, parallel laminated fine-grained yellowish sandstone and siltstone; representing channel lag, point bar and overbank flood plain deposits of mixed load meandering river. In these sediments, development of nodular, buckled bedded calcrete, rhizoliths and tepee is noticed. Granulometric studies of these sediments revealed presence of wide range of grain size classes, polymodal grain size distribution, moderate to very poor sorting, positive skewness and leptokurtic nature, supporting fluvial environment of deposition. Lithic arenitic nature, heavy mineral assemblage with dominance of augite and low ZTR index of these sediments indicate mineralogical immaturity and presence of illite, kaolinite and montmorllionite together with geochemical composition indicate their derivation from mixed provenance of Precambrian granite, metapelites, Vindhyan Supergroup, Gondwana Supergroup, Deccan trap basalt, and laterite. The thin sections studies reveal signatures of meteoric phreatic and vadose zone diagenesis related with semi-arid climate and subaerial exposure. The δ 13 C and δ 18 O content of calcretes indicate their pedogenic and/or shallow groundwater origin under semi-arid climatic conditions, and C3–C4 mixed vegetation with dominance of C4 vegetation. OSL and 14 C dates of the samples from Baneta Formation suggest deposition of these sediments in Late Pleistocene.

CSIR-National Geophysical Research Institute (CSIR-NGRI), a constituent research laboratory of the Council of Scientific and Industrial Research, was established in the year 1961. Over the years, it has nurtured, expertized and established highly specialized facilities for all the major disciplines of geosciences under one roof (https://www.ngri.org.in/facilities.php). The multidisciplinary research of the institute is intended to comprehend the complex surface and subsurface structures and processes of the Earth system for refining the knowledge base, and its innovative applications for the betterment of the human society through development of strategies for sustainable management of natural resources like water, energy, and minerals and improve preparedness as well as resilience to geological hazards. With the plausible necessity to synergize science, technology, and innovation to translate identified research leads for the social and industrial benefits and significant modifications in the government planning and funding, the science plans have been re-formulated at CSIRNGRI. The new scientific projects including the Fast Track Translational projects, have been interwoven with the reorganized structure of the Institute to optimize resources and synergize them for taking geoscience research to a newer height.

Koyna-Warna region of western India is an active seismic zone due to the Reservoir Triggered Seismicity (RTS). Earthquake precursor studies are carried out monitoring hydrochemical and stable isotope signatures in the groundwater from 15 bore wells since January 2005, for more than 12 years (January 2005 to February 2017). Depth of these boreholes ranges from 100 to 250 m. Cyclic or temporal variation in hydrochemistry is observed in few sensitive wells in Koyna region. The Govare well in Koyna is found to be most sensitive and the observed hydrochemical cycle is closely associated with local earthquakes of M > 5. The earthquakes M <5 occurring either in Warna cluster or close to the observation wells, did not generate hydrochemical precursory changes. The increase in hydrochemistry is hypothesized as mixing of two aquifer waters with different hydrochemistry. It is noted that a precursory hydrochemical cycle is observed during first quarter of 2015, but no earthquake M > 5.0 occurred till date. The cyclic changes in hydrochemistry, however, indicate on-going earthquake processes and an impending earthquake of M > 5 in the region.