Jayant K. Tripathi

Geochemistry of the loessic sediments on Delhi ridge, eastern Thar desert, Rajasthan: implications for exogenic processes

Abstract Quartzite ridges in the Delhi region include in their local depressions thick piles of unconsolidated, unstratified, yellowish brown, homogenous loamy sediments. These Delhi ridge sediments (DRS) have textural, mineralogical and geochemical characteristics similar to those of loess sediments. Geochemically, DRS, just as other loess sediments, are similar to average exposed upper continental crust of Taylor and McLennan [Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell, London, 311 pp.]. The calculated chemical index of alteration [Nesbitt, H.W., Young, G.M., 1984. Prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations. Geochim. Cosmochim. Acta 54, 1523–1534; Nesbitt, H.W., Young, G. M., 1989. Formation and diagenesis of weathering profiles. J. Geol. 97, 129–147.] and other chemical parameters suggest a provenance of chemically less weathered rocks. During the process of wind transport and deposition, not only the dilution effect of silica on the REE abundance was counterbalanced but also the REE pattern was kept similar to the UCC and PAAS by the appropriate concentration and mixing of the REE bearing phases. The immediate source to these sediments is likely to be mechanically ground sediments of glacial origin. The last phase of the upliftment of the Himalayas, accompanied by Pleistocene glaciation could have provided a vast glacio–fluvial outwash plain. The aeolian processes associated with prevailing W to SW winds in the hot arid condition seem to have been selectively transporting fertile silt materials leaving behind infertile desert sands.

A unique Ni2+ -dependent and methylglyoxal-inducible rice glyoxalase I possesses a single active site and functions in abiotic stress response.

The glyoxalase system constitutes the major pathway for the detoxification of metabolically produced cytotoxin methylglyoxal (MG) into a non-toxic metabolite D-lactate. Glyoxalase I (GLY I) is an evolutionarily conserved metalloenzyme requiring divalent metal ions for its activity: Zn(2+) in the case of eukaryotes or Ni(2+) for enzymes of prokaryotic origin. Plant GLY I proteins are part of a multimember family; however, not much is known about their physiological function, structure and metal dependency. In this study, we report a unique GLY I (OsGLYI-11.2) from Oryza sativa (rice) that requires Ni(2+) for its activity. Its biochemical, structural and functional characterization revealed it to be a monomeric enzyme, possessing a single Ni(2+) coordination site despite containing two GLY I domains. The requirement of Ni(2+) as a cofactor by an enzyme involved in cellular detoxification suggests an essential role for this otherwise toxic heavy metal in the stress response. Intriguingly, the expression of OsGLYI-11.2 was found to be highly substrate inducible, suggesting an important mode of regulation for its cellular levels. Heterologous expression of OsGLYI-11.2 in Escherichia coli and model plant Nicotiana tabacum (tobacco) resulted in improved adaptation to various abiotic stresses caused by increased scavenging of MG, lower Na(+) /K(+) ratio and maintenance of reduced glutathione levels. Together, our results suggest interesting links between MG cellular levels, its detoxification by GLY I, and Ni(2+) - the heavy metal cofactor of OsGLYI-11.2, in relation to stress response and adaptation in plants.

Feasibility of the Sar Technique on Quartz Sand of Terraces of NW Himalaya: A Case Study from Devprayag

Feasibility of the Sar Technique on Quartz Sand of Terraces of NW Himalaya: A Case Study from Devprayag Optically Stimulated Luminescence (OSL) dating technique based on the Single Aliquot Regenerative dose (SAR) protocol is being used increasingly as a means of establishing sediment burial age in the late Quaternary studies. Thermal transfer, low and changing luminescence sensitivity of quartz grains of young sedimentary belts of the New Zealand Alps and the north-east Himalaya poses problems in using SAR protocol. Records of active tectonics and signatures of palaeo-climate are preserved in the Quaternary - Holocene terrace sediments. Therefore, to unfold the history of successive tectonic and palaeo-climate events, robust chronological technique is needed. Palaeoflood deposits in NW Lesser Himalayan region receive quartz from the weathering of various rock types such as quartzite and phyllite in the Alaknanda Basin. A series of tests e.g. dose recovery, preheat plateau, thermal recuperation and change in sensitivity, were performed to check the suitability of quartz grains collected from the terrace sediment of Devprayag of the NW Himalaya, for OSL studies. Inferences were drawn regarding the source of the quartz grains on the basis of the geochemistry and luminescence intensity of the terrace sediment. The study shows that though quartz from the North West Himalaya are low in luminescence intensity but the reproducibility of De value makes the quartz sand suitable for SAR dating technique. Relation between luminescence intensity with CIA values help to predict the provenance of quartz sand. Tests show that the quartz from NW Himalaya is suitable for SAR protocol in OSL.

Major ion chemistry of the Son River, India: Weathering processes, dissolved fluxes and water quality assessment

River Son, draining diverse lithologies in the subtropical climate of the peninsular sub-basin of the Ganga basin, is one of the major tributaries of the Ganga River. The chemistry of major ions in the surface water of the Son River was studied in detail to determine various source(s) and processes controlling its water chemistry, seasonal and spatial variations in water chemistry, dissolved fluxes and chemical denudation rate (CDR). The study shows that Ca2+, Mg2+ and HCO3−

A nuclear‐localized rice glyoxalase I enzyme, OsGLYI‐8, functions in the detoxification of methylglyoxal in the nucleus

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The Son, A Vindhyan River

are major ionic species in the river water. Most of the measured parameters exhibit a relatively lower concentration in the post-monsoon as compared to pre-monsoon season. The water chemistry highlights the influence of continental weathering aided by secondary contributions from ground water, saline/alkaline soils and anthropogenic activities in the catchment. Results also reflect the dominance of carbonate weathering over silicate weathering in controlling water composition. The Son River delivers about 4.2 million tons of dissolved loads annually to the Ganga River, which accounts for ∼6% of the total annual load carried by the Ganga River to the Bay of Bengal. The average CDR of the Son River is 59.5 tons km −2 yr −1, which is less than the reported 72 tons km −2 yr −1 of the Ganga River and higher than the global average of 36 tons km −2 yr −1. The water chemistry for the pre-monsoon and post-monsoon periods shows a strong seasonal control on solute flux and CDR values. The water chemistry indicates that the Son River water is good to excellent in quality for irrigation and also suitable for drinking purposes.

Recent insights into the dissolved and particulate fluxes from the Himalayan tributaries to the Ganga River

&NA; The cellular levels of methylglyoxal (MG), a toxic byproduct of glycolysis, rise under various abiotic stresses in plants. Detoxification of MG is primarily through the glyoxalase pathway. The first enzyme of the pathway, glyoxalase I (GLYI), is a cytosolic metalloenzyme requiring either Ni2+ or Zn2+ for its activity. Plants possess multiple GLYI genes, of which only some have been partially characterized; hence, the precise molecular mechanism, subcellular localization and physiological relevance of these diverse isoforms remain enigmatic. Here, we report the biochemical properties and physiological role of a putative chloroplast‐localized GLYI enzyme, OsGLYI‐8, from rice, which is strikingly different from all hitherto studied GLYI enzymes in terms of its intracellular localization, metal dependency and kinetics. In contrast to its predicted localization, OsGLYI‐8 was found to localize in the nucleus along with its substrate, MG. Further, OsGLYI‐8 does not show a strict requirement for metal ions for its activity, is functional as a dimer and exhibits unusual biphasic steady‐state kinetics with a low‐affinity and a high‐affinity substrate‐binding component. Loss of AtGLYI‐2, the closest Arabidopsis ortholog of OsGLYI‐8, results in severe germination defects in the presence of MG and growth retardation under salinity stress conditions. These defects were rescued upon complementation with AtGLYI‐2 or OsGLYI‐8. Our findings thus provide evidence for the presence of a GLYI enzyme and MG detoxification in the nucleus. Significance Statement Methylglyoxal, a toxic byproduct of glycolysis, increases under abiotic stress and is detoxified primarily by glyoxalases. Previously studied glyoxalase I (GLYI) enzymes are cytoplasmic metalloproteins. Here, we demonstrate a nucleus‐localized rice glyoxalase I, OsGLYI‐8, that detoxifies methylglyoxal in a metal‐independent but Zn2+/Mn2+‐stimulated manner. As Arabidopsis mutant of its homolog exhibits severe growth retardation in the presence of methylglyoxal or salinity stress, we suggest that nuclear detoxification of methylglyoxal might protect DNA from damage, especially under stress conditions.

Hydrochemistry and Quality Assessment of Groundwater in Naini Industrial Area, Allahabad District, Uttar Pradesh

The Son River originates in the Amarkantak hills of Maikal range at an elevation of ~600 m in Madhya Pradesh and then flows through the north of Kaimur plateau of Vindhya ranges. This river is an important tributary of the Ganga River, and after flowing through the parts of Madhya Pradesh, Uttar Pradesh, Jharkhand and Bihar states, it joins the Ganga River on its southern bank near Patna. The major tributaries of the Son River emerge in the highlands and flow in a northward direction to join the main river. The major tributaries of the river are the Rihand, North Koel, Gopad, Banas and Kanhar rivers. The Son River drains through the Gondwana and Vindhyan Supergroups, Mahakoshal Group, Central Granitic Complex (CGC) and Quaternary alluvium. Five widespread alluvial formations have been proposed by others in the Son River valley, namely the Sihawal, Khunteli, Patpura, Baghor and Khetaunhi, in the oldest to youngest sequence. The Son River water has been found good to excellent in quality for irrigation and also suitable for drinking purposes. Many dams, reservoirs and hydropower generation plants occur on the Son River and its tributaries; these resources are serving for irrigation and electricity generation in the Son River valley. It has been reported that the hydropower generation has been decreasing in the last three decades for the Son River valley.

Is river Ghaggar, Saraswati? Geochemical constraints

The Ganga River plays a major role in the transfer of materials from the Indian sub-continent to the Bay of Bengal, both in dissolved and particulate forms. To understand the present elemental dynamics of the Ganga River system, it is important to assess the hydrogeochemical contribution of its tributaries. In this paper, we present an updated database on dissolved and particulate fluxes and denudation rates of the Himalayan tributaries of the Ganga River (Ramganga, Ghaghara, Gandak and Kosi). Dissolved trace element concentrations, their fluxes and suspended sediment-associated elemental fluxes of the Himalayan tributaries have been reported for the first time. Total dissolved flux of the Ramganga, Ghaghara, Gandak and Kosi was estimated as 4, 19.1, 10.3 and 8.8 million tons year−1 accounting for ~ 5.7, ~ 27.3, ~ 14.7 and ~ 12.6%, respectively, of the total annual dissolved load carried by the Ganga River. The total particulate flux of the Ramganga, Ghaghara, Gandak and Kosi was computed as 8.2, 81.6, 30.9 and 19.5 million tons year−1, respectively. Compared to earlier studies, we have found a significant increase in the total dissolved flux and chemical denudation rate of the studied tributaries. The estimated particulate fluxes were found to be low in comparison to the previous studies. We suggest that a significant increase in the dissolved fluxes and a decrease in the particulate fluxes are an indication of the increasing anthropogenic disturbances in the catchment of these tributaries.