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      https://www.ias.ac.in/article/fulltext/jess/130/0098

    • Keywords

       

      Delhi; India; fluoride pollution; major ions chemistry; sediment groundwater interaction; chemical weathering; isotopic fractionation; evaporative enrichment.

    • Abstract

       

      Fluoride (F$^{-}$ ) pollution in groundwater of the Older Alluvial Plain (OAP) of Delhi has been reported as a major problem. About 34% of the groundwater samples collected for this study had F$^{-}$ level beyond the permissible limit; with F$^{-}$ concentration in the range of 0.14–3.15 mg/L (average 1.20 mg/L). In this context, this article for the first time attempts on the genesis of major ions chemistry and F$^{-}$ pollution in groundwater of OAP Delhi by going beyond the statistical analysis to sediment geochemistry, chemical weathering processes and understanding of the processes using stable environmental isotopes ($^{2}$H and $^{18}$O). The XRD of the OAP sediments revealed the dominance of fluor-biotite, albite, calcite, quartz, and chlorite. Whereas, the separated clay revealed the dominance of chlorite, kaolinite, and illite minerals. The saturation index (SI) values indicated that the groundwater chemistry is in the process of further F$^{-}$ enrichment by way of sediment groundwater interaction. With the given mineralogy of the sediments, the dominance of major ions like Na$^{+}$), K$^{+}$, Mg$^{2+}$, Ca$^{2+}$, Cl$^{-}$ and F$^{-}$ has been attributed to chemical weathering of biotites, phlogopites, albite, and calcite during sediment–water interaction. While the dominance of SO$_{4}$ $^{2-}$ has been attributed to anthropogenic sources and confirmed by its association with heavier stable isotopes of hydrogen ($\delta^{2}$H: −50.44 to −40.02 per thousand) and oxygen ($\delta^{18}$O: −7.19 to −5.62 per thousand) indicating evaporative enrichment during isotopic fractionation.

    • Author Affiliations

       

      SHAKIR ALI ALI1 SHASHANK SHEKHAR1 TRUPTI CHANDRASEKHAR2 AKHILESH KUMAR YADAV1 NARESH KUMAR ARORA3 CHANDRASHEKHAR AZAD KASHYAP2 PROSUN BHATTACHARYA4 S P RAI5 PRABHA PANDE6 DORNADULLA CHANDRASEKHARAM7

      1. Department of Geology, University of Delhi, Delhi 110 007, India.
      2. Department of Earth Sciences, IIT Bombay, Mumbai 400 076, India.
      3. Central Soil Salinity Research Institute, Karnal, Haryana 132 001, India.
      4. KTH-International Groundwater Arsenic Research Group, Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
      5. Department of Geology, Banaras Hindu University, Varanasi 221 005, India.
      6. Department of Geology, Ram Lal Anand College, New Delhi 110 021, India.
      7. Department of Civil Engineering, IIT Hyderabad, Sangareddy 502 285, India.
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  • Journal of Earth System Science | News

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