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      https://www.ias.ac.in/article/fulltext/jess/129/0205

    • Keywords

       

      Environmental isotopes; trace metals; quality indices; HFE diagram; geochemical evolution; coastal zone; Andhra Pradesh

    • Abstract

       

      This paper elaborates the hydrochemical and environmental isotope ($\delta^{2}$H and $\delta^{18}$O) inferences obtained from Uddanam region, Andhra Pradesh, India. Groundwater samples collected during pre-monsoon (June 2019) showed that the quality is fresh (EC < 1539 $\mu$S/cm) and contaminants like fluoride (<1.6 mg/L) and nitrate (<49 mg/L) are present within permissible limits. The composite water quality indices for drinking (DWQI: 14.1–92.5) and irrigation (IWQI: 2.8–20.2) are found to be satisfactory. The major water types are found to be Ca–Na–HCO$_{3}$, Na–Ca–HCO$_{3}$, Na–Mg–HCO$_{3}$–Cl, Ca–Mg–HCO$_{3}$–Cl and Na–HCO$_{3}$. Three geochemical pathways are found signifying evaporite dissolution, contribution of silicate mineral weathering and base-exchange process, which is supported by estimated chloro-alkaline indices (CAI-1: −4.3 to −0.2, CAI-2: −1.03 to −0.08). Trace metal data clearly suggest that groundwater is free from any metal pollution. Dissolved silica (SiO$_{2}$) levels range from 34 to 131 mg/L and do not show any particular spatial trend. Isotope data infer that groundwater is recharged by rainwater after undergoing evaporation ($\delta^{18}$O: −6.0 per thousand), which matches with that of the combined isotope signature ($\delta^{18}$O: −5.5 per thousand) of SW and NE monsoon rainfall. $\delta^{18}$O–TDS correlations and hydrochemical facies evolution (HFE) diagram do not infer any seawater intrusion into these coastal aquifers.

      $\bf{Highlights}$

      $\bullet$ The composite water quality indices infer good to excellent category for drinking and agriculture.

      $\bullet$ Mineral weathering, evaporite dissolution and base-exchange reactions are the main geochemical processes.

      $\bullet$ Dissolved silica occurrence in groundwater is sporadic.

      $\bullet$ Isotope indicators show the signature of both SW and NE monsoons recharge to groundwater.

      $\bullet$ Observed brackishness in groundwater is due to water – rock interaction and not due to sea water intrusion.

    • Author Affiliations

       

      TIRUMALESH KEESARI1 2 ANNDASANKAR ROY1 2 DIKSHA PANT1 2 UDAY KUMAR SINHA1 NAGENDRA KUMAR P V3 L VAIKUNTA RAO4

      1. Isotope Hydrology Section, Isotope and Radiation Application Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
      2. Homi Bhabha National Institute, Anushakti Nagar, Mumbai, India.
      3. Department of Chemistry, School of Science, GITAM University, Hyderabad, India.
      4. Department of Chemistry, School of Science, GITAM University, Visakhapatnam, Andhra Pradesh, India.
    • Dates

       
  • Journal of Earth System Science | News

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