Browsing by Author "Singh, Laishram Premananda"
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Item Distribution of rare earth elements and stable isotopic constituents along the groundwater flow paths in the Quaternary deposits of Imphal valley in north-east India(John Wiley and Sons Ltd, 2021-09-22T00:00:00) Singh, Laishram Premananda; Kshetrimayum, Krishnakanta SinghGroundwater samples collected from three flow paths (the western, central, and eastern flows) in the shallow aquifers of the Imphal valley of north-east India were examined to study the variation in hydrochemical and rare earth element (REE) characteristics along these flow paths. Each flow path covers a length of around 45 km towards the down gradient. In the western flow, the hydrochemical facies evolved from Na-Cl-Ca to Ca-Na-Mg-Cl-HCO3; in the central flow, it varies from Ca-Mg-Na-Cl to Na-Ca-Cl-HCO3 and in the eastern flow, it changes from Na-Cl to Ca-Mg-HCO3 indicating the evolution of saline water type in the piedmont zone to fresh water type towards the discharge zones around the Loktak Lake. The REE concentration varies along the flow path as the total light REE (LREE) is more enriched than total heavy REE (HREE) in the western and central flows, while LREE is less than HREE in the eastern flow. North American Shale Composite (NASC)-normalized REE patterns in these flow types show significant convex-up NASC-normalized patterns with depleted LREEs. The redox condition in the flow paths is controlled by redox-sensitive elements such as Eh, pH, Fe, Mn, U, Er, Gd, and Nd which vary relatively along with these flows. REE fractionation depicted by (Er/Nd)SN ratios are high around the upgradient and decrease along the down gradient towards Loktak Lake. The isotopic constituents (?18O and ?D) exhibit fluctuations in their ratios along the groundwater flow paths. The residual hill and piedmont zones are characterized by depleted isotopic composition while the alluvial and flood plains show enriched isotopic composition. Thus, the present study elucidates the behavioural change in major hydrochemical parameters including REE and isotopic constituents, along with the groundwater flow, which will provide a holistic view in understanding the evolution of groundwater in terms of its quality, quantity, and origin in the study area. � 2021 John Wiley & Sons Ltd.Item Evaluation of spatial characteristics of groundwater hydrochemical constituents across different geomorphic units of the�Imphal Valley in Northeast India(Springer Science and Business Media Deutschland GmbH, 2021-07-05T00:00:00) Singh, Laishram Premananda; Kshetrimayum, K.S.The assessment of hydrochemical constituents across different geomorphic units of the Imphal valley of Northeastern India has been carried out. Geomorphologically, the valley is broadly demarcated as the�residual hill, piedmont zone, alluvial plain, and flood plain. The Scholler diagram and Box and Whisker plots suggest that the distribution of ions is characterized by dispersed concentrations owing to variation in the�lithologies in the�geomorphic units. The pH value ranges from 6.90 to 7.21 with a mean value of 7.04, indicating neutral water in the residual hill. In the piedmont zone, it ranges from slightly acidic (4.83) to neutral (7.40) with a mean of 6.58. In the alluvial and flood plains, the values range from 6.15 to 7.44, with a mean of 6.84 and 6.07 to 7.14 with an average of 6.73, respectively suggesting neutral water. TDS range shows slight reduction in the�alluvial plain and flood plain owing to effluent water supply from the�rivers whereas, oxidation�reduction potential (Eh) ranges from 8 to ?�19�mV with highest in the�residual hill, indicating reducing condition. Higher Ca2+ and Mg2+ in the�residual hill and piedmont zone are associated with the�cation-exchange process. Na+ and HCO3? are highest in the�alluvial and flood plains due to weathering of sodium-rich montmorillonite or dissolution of halite or nahcolite (NaHCO3) minerals from clay. The scatter plots indicate that the hydrogeochemical processes throughout the geomorphic units are mainly controlled by the�ion exchange, silicate weathering, carbonate weathering, and evaporate dissolution. The hydrochemical facies are characterized by (i) Na�K�Cl, (ii) Ca�Cl, and (iii) Na�K�Ca�Mg�Cl�SO4�HCO3. The residual hill and piedmont zones are dominated by Ca�Cl facies, implying recent meteoric water coupled with halite riched source of water. The alluvial plain is dominated by Na�K�Cl facies, while the flood plain is characterized by Na�K�Ca�Mg�Cl�SO4�HCO3 facies, suggesting the�mixed type resulted from the ion exchange process. These facies suggest that the groundwater belongs to the initial and intermediate stages of chemical evolution indicating fresh quality. � 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.