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Gopinath, S., Srinivasamoorthy, K., Saravanan, K., & Prakash, R. (2019). Tracing groundwater salinization using geochemical and isotopic signature in Southeastern coastal Tamilnadu, India. Chemosphere, 236, 124305.
Abstract: Attempt has been made to discriminate groundwater salinity causes along the east coast of India. A total of 122 groundwater samples (61/season) were collected for two diverse seasons (Pre Monsoon and Post Monsoon) and analyzed for physical and chemical components along with stable isotopes. The Piper diagram proposes samples along the coast predisposed by saltwater incursion. Ionic ratio plots recommend groundwater discriminatory by changing geochemical signatures. The statistical correlation suggests impact of saltwater incursion, anthropogenic and rock water interaction as sources for dissolved constituents in groundwater. The thermodynamic stability plot suggests higher silicate dissolution, weathering and ion exchange prompting water chemistry nevertheless of seasons. The δ 18O and δ 2H increases towards the sea suggesting enrichment attributed to the sea water influence and rainfall influences along the southwestern parts of the study area.
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Zhao, Q., Su, X., Kang, B., Zhang, Y., Wu, X., & Liu, M. (2017). A hydrogeochemistry and multi-isotope (Sr, O, H, and C) study of groundwater salinity origin and hydrogeochemcial processes in the shallow confined aquifer of northern Yangtze River downstream coastal plain, China. Applied Geochemistry, 86, 49–58.
Abstract: Economically developed coastal areas have a high water demand, and their groundwater resources can be threatened by salinization. Many methods and tracers have been used to discriminate the source of salinization because a single method does not yield reliable results. In this paper, the shallow confined coastal plain aquifer, north of the downstream Yangtze River in China, is used as a case study to investigate the origin of the salinity and the relevant geochemical processes for this aquifer. Multiple environmental tracers of major ions, minor ions (Br−, I−), and isotopes (18O, 2H, 13C, 87Sr, 3H, 14C) were used so as to provide reliable conclusions. The TDS distribution of the aquifer has an increasing trend, from below 500 mg/L in the inland areas to more than 20,000 mg/L around the southeast coastline. The water chemical type evolves from HCO3-Ca to Cl-Na as the TDS increases. The results suggest that the groundwater salinity is influenced by seawater intrusion. The seawater proportions in the groundwater samples range from 0.07% to 94.41% and show the same spatial distribution pattern as TDS. The 3H and 14C values show that the highest salinity was mainly caused by a seawater transgression around 6000a B.P. The aquifer is also affected by other hydrogeochemical processes: base exchange has enriched Ca2+ and depleted K+ and Na+, sulfate reduction has reduced the concentration of SO42− and enriched HCO3−, and iodine-rich organic matter decomposition has enriched the concentration of I−. The iodine enrichment also suggests paleo-seawater intrusion. In addition, the precipitation of carbonate minerals has decreased the concentration of Ca2+, Mg2+, and HCO3−, albeit to a limited extent.
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