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Qi, H., Ma, C., He, Z., Hu, X., & Gao, L. (2019). Lithium and its isotopes as tracers of groundwater salinization: A study in the southern coastal plain of Laizhou Bay, China. Sci Total Environ, 650(Pt 1), 878–890.
Abstract: In the southern coastal plain of Laizhou Bay, due to intensive exploitation of groundwater since the early 1970s, the shallow aquifer has been severely influenced by saltwater intrusion, which causes the extraction to shift from shallow to deeper aquifer changing the hydrogeological condition greatly. This study was conducted to investigate the groundwater salinization using hydrochemistry and H, O and Li isotope data. Dissolved Li shows a linear correlation with Cl and Br in seawater, brine and saline groundwater indicating the marine Li source, whereas the enrichment of Li in surface water, brackish and fresh groundwater is impacted by dissolution of silicate minerals. The analyses of hydrochemistry and isotopes (H, O and Li) indicate that brine originated from seawater evaporation, followed by mixing processes and some water-rock interactions; shallow saline groundwater originated from brine diluted with seawater and fresh groundwater; deep saline groundwater originated from seawater intrusion. The negative correlation of δ(7)Li and Li/Na in surface water, brackish and fresh groundwater is contrary to the general conclusion, indicating the slow weathering of silicate minerals and hydraulic interaction between surface water and shallow groundwater in this area. The analyses of hydrochemistry and isotopes (Li, H and O) can well identify the salinity sources and isotope fractionation in groundwater flow and mixing, especially groundwater with high TDS. As both mixing with saltwater and isotope fractionation can explain the combination of high δ(7)Li and low TDS in brackish groundwater, isotope fractionation may limit their use in recognizing salinity sources of groundwater with low TDS.
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Tulipano, L., Fidelibus, D. M., & Panagopoulos, A. (Eds.). (2005). Groundwater management of coastal karstic aquifers. EU.
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Rina, K., Datta, P. S., Singh, C. K., & Mukherjee, S. (2013). Isotopes and ion chemistry to identify salinization of coastal aquifers of Sabarmati River Basin. Current Science, 104(3), 335–344.
Abstract: The lower reaches of the Sabarmati River Basin in Gujarat have intense agricultural and industrial activities and this part is affected by problems of groundwater salinity. Here we attempt to assess the processes governing the causes of groundwater salinity in the coastal alluvial aquifer, employing δ18O and δD isotopes in integration with ionic ratio. The different hydrochemical facies such Na–Mg–HCO3–Cl, Na–Cl–SO4, Na–Mg–Cl–HCO3–SO4 and Na–Cl of groundwater show the occurrence of complex geochemical phenomenon in the study area. Ionic ratio (such as Mg2+/Ca2+, Na+/Cl−, SO24/Cl-, K+/Cl−) and isotopic composition (δ18O and δD) of groundwater indicate that while in coastal areas seawater intrusion is taking place, in inland areas various anthropogenic activities and overexploitation have induced salinity in groundwater. Over-pumping of groundwater has also induced lateral intermixing of highly saline water in the vicinity of coastal areas with relatively fresh/low saline groundwater along specific flow pathways.
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Han, D., Post, V. E. A., & Song, X. (2015). Groundwater salinization processes and reversibility of seawater intrusion in coastal carbonate aquifers. Journal of Hydrology, 531, 1067–1080.
Abstract: Seawater intrusion (SWI) has led to salinization of fresh groundwater reserves in coastal areas worldwide and has forced the closure of water supply wells. There is a paucity of well-documented studies that report on the reversal of SWI after the closure of a well field. This study presents data from the coastal carbonate aquifer in northeast China, where large-scale extraction has ceased since 2001 after salinization of the main well field. The physical flow and concomitant hydrogeochemical processes were investigated by analyzing water level and geochemical data, including major ion chemistry and stable water isotope data. Seasonal water table and salinity fluctuations, as well as changes of δ2H–δ18O values of groundwater between the wet and dry season, suggest local meteoric recharge with a pronounced seasonal regime. Historical monitoring testifies of the reversibility of SWI in the carbonate aquifer, as evidenced by a decrease of the Cl− concentrations in groundwater following restrictions on groundwater abstraction. This is attributed to the rapid flushing in this system where flow occurs preferentially along karst conduits, fractures and fault zones. The partially positive correlation between δ18O values and TDS concentrations of groundwater, as well as high NO3− concentrations (\textgreater39mg/L), suggest that irrigation return flow is a significant recharge component. Therefore, the present-day elevated salinities are more likely due to agricultural activities rather than SWI. Nevertheless, seawater mixing with fresh groundwater cannot be ruled out in particular where formerly intruded seawater may still reside in immobile zones of the carbonate aquifer. The massive expansion of fish farming in seawater ponds in the coastal zone poses a new risk of salinization. Cation exchange, carbonate dissolution, and fertilizer application are the dominant processes further modifying the groundwater composition, which is investigated quantitatively using hydrogeochemical models.
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Edmunds, W. M. (1996). Bromine geochemistry of british groundwaters. Mineralogical Magazine, 60(399), 275–284.
Abstract: \textlessp\textgreater The concentrations of Br in potable groundwaters in the United Kingdom range from 60 to 340 µg 1 \textlesssup\textgreater-1\textless/sup\textgreater . The occurrence of Br is described in terms of the Br/Cl weight ratio which enables small changes in bromide concentrations to be assessed in terms of salinity. Median values of Br/Cl in groundwaters range from 2.60 to 5.15 × 10 \textlesssup\textgreater−3\textless/sup\textgreater compared with a sea water ratio of 3.47× 10 \textlesssup\textgreater−3\textless/sup\textgreater . In recent shallow groundwaters the Br/Cl ratio is rather variable in response to a range of natural and anthropogenic inputs (marine and industrial aerosols, industrial and agricultural chemicals including road salt). Some slight enrichment in Br/Cl also occurs naturally during infiltration as a result of biogeochemical processes. \textless/p\textgreater
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