Affiliations 

  • 1 Water Research Centre, Kuwait Institute for Scientific Research, Safat, Kuwait; Department of Earth Sciences, Annamalai University, Tamilnadu 608002, India. Electronic address: sabarathinam.chidambaram@gmail.com
  • 2 Department of Earth Sciences, Annamalai University, Tamilnadu 608002, India. Electronic address: banajapanda1992@gmail.com
  • 3 Isotope and Radiation Application Division, Bhabha Atomic Research Centre, Mumbai 400 085, India; Homi Bhabha National Institute, DAE, Mumbai 400094, India. Electronic address: tirumal@barc.gov.in
  • 4 Department of Applied Geology, Faculty of Engineering and Science, Curtin University, Malaysia, CDT 250, 98009 Miri, Sarawak, Malaysia.. Electronic address: prasanna@curtin.edu.my
  • 5 Grass Roots Research and Creation India (P) Ltd., India
  • 6 School of Environmental Sciences, JNU, New Delhi, India. Electronic address: alrjnu@gmail.com
Mar Pollut Bull, 2022 Jan;174:113273.
PMID: 35090268 DOI: 10.1016/j.marpolbul.2021.113273

Abstract

The dynamics of the coastal aquifers are well-expressed by geochemical and isotopic signatures. Coastal regions often exhibit complex groundwater recharge pattern due to the influence of depression in the Bay of Bengal, tidal variations on surface waters, saline water intrusion and agricultural return flows. In this research, groundwater recharge processes occurring in coastal Tamil Nadu, South India were evaluated using major ion chemistry and environmental isotopes. A total of 170 groundwater samples were collected from shallow and deep aquifers during both post-monsoon (POM) and pre-monsoon (PRM) seasons. The isotopic results showed a wide variation in the shallow groundwater, suggesting contribution from multiple recharge sources. But, the deeper groundwater recharge is mainly from precipitation. The northern part of the study area showed more depleted isotopic values, which rapidly changed towards south from -6.8 to -4.4‰. Alternatively, central and southern parts exhibited relatively enriched isotopic content with variation from -0.58 to -2.7‰. Groundwater was discerned to be brackish to saline with chloride content, 600-2060 mgL-1 and δ18O ranging from -5.8 to -4.5‰, suggesting influence of the saline water sources. A minor influence of anthropogenic activities was also observed in the deeper groundwater during PRM, which was confirmed by tritium and Cl- trends. The old groundwater with depleted isotopic content infer recharged by distant sources while modern groundwater with enriched isotopes points to the influence of evaporated recharge.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.