Research papersDelineating the source and mechanism of groundwater salinization in crucial declining aquifer using multi-chemo-isotopes approaches
Introduction
The term “groundwater salinization” is used to specify an increase in overall chemical content over background levels in groundwater (van Weert et al., 2009). Numerous summits and conferences are held every year around the world to deal with the problem of aquifers salinization, especially coastal aquifers. The most important meeting on the influx of salt water intrusion (SWIMs) into groundwater systems was established in 1968 (Mirzavand, 2018). Recently, the SWIMs are more discussed about modeling of water resources, and hydrogeology, hydrogeochemistry and isotopic studies of the groundwaters. Also, a special group in Cartagena was established since 2001 which called salt water intrusion in coastal aquifers (SWICA) to investigate the issue of saltwater intrusion on a global scale (Mirzavand, 2018). Obviously, the issue of groundwater salinization is a global concern (Vengosh et al., 2002a, Vengosh et al., 2002b, van Weert et al., 2009), and a serious problem especially in arid and semi-arid areas, where the ground water is a vital resource (Mirzavand et al., 2020).
Proper management of accessible groundwater resources is impossible without knowledge of the distribution of fresh and saline groundwater and the processes that lead to salinization (Clark, 2015). Salt water intrusion is a long-term process that could degrade groundwater system and restrict the availability of useable water for drinking, irrigation and industry (Vengosh, 2014). Proximity of groundwater system to seawater, salt lake, mineral dissolution, and anthropogenic activity (such as over pumping) in coastal aquifer could destroy freshwater resources (Vengosh, 2014, Vengosh, 2003). Chemical composition of groundwater in a coastal aquifer is a function of the rate of fresh/salt water mixing from different salinity sources such as water–rock interaction, cation exchange, redox reaction, carbonate and evaporate mineral dissolution, old salty water tapped in the aquifer, seawater/ salt lake intrusion (Bagheri et al., 2014, Clark, 2015, Mirzavand et al., 2018, Nadri et al., 2014, Vengosh, 2003). For the effective management of groundwater resources, policies are dependent on understanding the sources and mechanism of groundwater system salinization (Bagheri et al., 2019, Clark, 2015) and on the degree and rate of salinization (Bagheri et al., 2019). The causes for groundwater salinization can be unclear (Larsen et al., 2017), but geochemical approaches as ionic to chloride ratios and trace elements may be useful in tracing the origin of salinity (Vengosh et al., 1999, Vengosh et al., 2002b, Mirnejad et al., 2011, Monjerezi, 2012, Trabelsi et al., 2012, Bagheri et al., 2013; Condomines and Seidel, 2017; Sridharan and Senthil Nathan, 2017). However, the multiple sources of salinity and the influence of geochemical reactions and groundwater mixing brings a high degree of complexity to the task of identifying the origin and mechanism of salinization (Vengosh, 2003).
Evaluations of major ion chemistry alone are often inconclusive or vague. The integration of isotopic tracers (e.g. isotopes of 2H and 18O) is sometimes necessary to determine origin and mechanism of salinity (Ayadi et al., 2016, Bagheri et al., 2013, Clark, 2015, Farid et al., 2015, Han et al., 2014, Hogan and Blum, 2003, Isawi, 2016, Li et al., 2019; Avner Vengosh et al., 2002; Zarei et al., 2013). Many researchers used chemical and isotopic data (e.g. isotopes of 2H and 18O) for delineation of the origin and mechanism of salinization in groundwater system (Bagheri et al., 2019, Ibrahim and Lyons, 2017).
In this study, the processes of salinization of groundwater in the Kashan Plain Aquifer (KPA) in central Iran has been investigated. KPA has experienced a significant decline in groundwater quality over the past decades due to salinization (average of EC in KPA in 1965 to 2017 has changed from 5600 to 26,000 μS/cm, respectively). Kashan is one of the major cities in central of Iran next to Great Kavir. The main source of water for all uses in the Kashan area is groundwater. The KPA suffers from over pumping of water since 1965, and it has water table drawdown close to 1 m/y (Mirzavand and Ghazavi, 2014).
Previous studies of groundwater in this region (KPA) focused on hydrogeological techniques and physiochemical characters of the aquifer (Mahjouri et al., 2005, Heydari et al., 2013) and suggested that the salt lake was the main origin of salinity in KPA (Jamshidzadeh and Mirbagheri, 2011, Vali-khodjeini, 1995). Nevertheless, due to the presence of multiplicity of sources of salinity (salt dome, evaporation, mineral dissolution, upconing, and salt lake intrusion) in KPA, other sources and mechanisms of salinization must be considered, by integration of hydrogeochemical and isotopic techniques. The overall purposes of this study are to: (1) identify the origin of salinity in the alluvial KPA, (2) determine the mechanism of salinity and deterioration of groundwater in the KPA, (3) determine the mixing ratio between the saltwater and fresh water, and (4) assess the groundwater ages in KPA.
Section snippets
Geological and hydrogeological setting
The KPA (longitude: 51°32′to 51°03′E, latitude: 33°27′to 34°13′N) is located in Isfahan Province, central Iran, occupying an area of 2403 km2 (Fig. 1) (Mirzavand and Ghazavi, 2014). Substratum of the aquifer is represented by evaporites deposits of the Miocene Marl and Upper Red Formation, which is overlain by low-level piedmont fan, and valley terrace deposits (350 m) that are mixture of, fine silt, coarse silt, clay, sand, gravel, boulder, and conglomerate (Fig. 2). The KPA is overlain by a
Sampling and methods
In July 2017, 42 water samples were collected from Qanats, deep and shallow wells (productive and monitoring wells), dug wells, the salt lake and from the saltpan (Fig. 1 and Table 1). These wells are designed for water supply and are connecting shallow and deep aquifer zones. The depths of wells are presented in Table 1. Before sampling, the bottles were rinsed with distilled water. Water samples were collected in 250 mL PVC bottles for anions, cations, trace elements, 2H, 18O, and Tritium,
Results and discussion
The geochemistry of samples from the KPA provides insights into the origin of groundwater and salinity source in the study area. While groundwater in the KPA is considered to be of local meteoric water from the greater catchment in the higher terrain surrounding the aquifer, the salinity has a range of possible origins and mechanisms for incorporation into the KPA. These include halite dissolution from the Nasr Abad buried salt dome (NBSD), intrusion of brine from the Salt Lake, leaching of
Conclusion
Salinization of groundwaters as major source of water in KPA in an arid and semi-arid region is a serious problem for which identifying the origin and mechanism of salinization is imperative for better management of this precious source of water. The integration of geophysics, hydrogeological, hydrogeochemical and isotopic methods, especially in regions with multiple potential sources of salinity is vital. For this purpose, these data were combined to make a conceptual model of salinization of
CRediT authorship contribution statement
Mohammad Mirzavand: Conceptualization, Formal analysis, Investigation, Methodology, Project administration, Software, Validation, Visualization, Writing - original draft, Writing - review & editing. Hoda Ghasemieh: Data curation, Project administration, Supervision, Writing - review & editing. Seyyed Javad Sadatinejad: Funding acquisition, Supervision. Rahim Bagheri: Investigation, Methodology, Supervision, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
We thank the Iran Water Resources Management Company, for their financial support of this project (WRE1-94008). Also, we thank Dr. Ian D Clark and the staff of Geochemistry, Jan Veizer Stable Isotope Laboratory and the A.E.Lalonde AMS Laboratory of the Advanced Research Complex (ARC) of University of Ottawa, Canada; Nimal De Silva, Smita Mohanty, Monika Wilk, Paul Middlestead, Kerry Klassen, Wendy Abdi, Wickham Patricia, and Sara Murseli for their support during lab work.
References (51)
- et al.
Overexploitation hazards and salinization risks in crucial declining aquifers, chemo-isotopic approaches
Hazard. Mater.
(2019) - et al.
Inter-comparison of salt e ff ect correction for δ 18 O and δ 2 H measurements in seawater by CRDS and IRMS using the gas-H 2 O equilibration method
Mar. Chem.
(2017) - et al.
Origin of the groundwater salinity and geochemical processes in detrital and carbonate aquifers: case of Chougafiya basin (Central Tunisia)
J. Hydrol.
(2015) - et al.
Chemical and isotopic constraints on evolution of groundwater salinization in the coastal plain aquifer of Laizhou Bay, China
J. Hydrol.
(2014) - et al.
Boron and lithium isotopes as groundwater tracers: a study at the Fresh Kills landfill, Staten Island, New York, USA
Appl. Geochem.
(2003) - et al.
Evaluation of groundwater quantity and quality in the Kashan Basin, Central Iran
Desalination
(2011) - et al.
The isotope composition of evaporating brines: effect of the isotopic activity ratio in saline solutions
Earth Planet. Sci. Lett.
(1975) The age of groundwater – definitions, models and why we do not need this term
Appl. Geochem.
(2014)- et al.
Stable isotopic evolutions of ground ice in permafrost of the Hoh Xil regions on the Qinghai-Tibet Plateau
Quat. Int.
(2017) - et al.
Geochemistry, Groundwater and Pollution
(2005)
determination of the Origin and recharge rates of the Sfax aquifer system (southeastern Tunisia) using isotope tracers
Env. Earth Sci.
Origin of brine in the Kangan gasfield: isotopic and hydrogeochemical approaches
Env. Earth Sci.
Chemical evolution of a gas-capped deep aquifer, southwest of Iran
Environ. Earth Sci.
Environmental Isotopes in Hydrogeology
Groundwater Geochemistry and Isotopes
Stable isotopes in precipitation
Tellus
An excel macro to plot the HFE – diagram to identify seawater intrusion phases
Ground Water
Effects of groundwater withdrawal on land subsidence in Kashan Plain, Iran
Bull. Eng. Geol. Environ.
Correlation study and regression analysis of drinking water quality in Kashan City
Iran
Assessment of the hydrogeochemical processes affecting groundwater quality in the eocene limestone aquifer at the desert fringes of El Minia Governorate, Egypt
Aquat. Geochem.
Integrated geochemistry, isotopes, and geostatistical techniques to investigate groundwater sources and salinization origin in the Sharm EL-Shiekh Area, South Sina, Egypt
Water Air Soil Pollut.
Deep Fluids in the Continents: I. Sedimentary Basins
Supp Material: Groundwater salinity influenced by Holocene seawater trapped in incised valleys in the Red River delta plain
Nat. Geosci.
Isotopic and geochemical interpretation of groundwater under the influences of anthropogenic activities
J. Hydrol.
Cited by (31)
Salinization of shallow groundwater in the Jiaokou Irrigation District and associated secondary environmental challenges
2024, Science of the Total EnvironmentBehavior of Sb and As in the hydrogeochemistry of adjacent karst underground river systems and the responses of such systems to mining activities
2023, Science of the Total EnvironmentDelineation of highland saline groundwater sources in Ba'kelalan region of NE Borneo to improve the salt-making production using geochemical and geophysical approaches
2022, ChemosphereCitation Excerpt :The relationship between δ18O, δ2H and salinity was used to identify salinization pathways, transport and origin of solutes in groundwater (Liu et al., 2016; Han et al., 2018; Mattos et al., 2018a; Xiang et al., 2019). The δD – δ18O relationships had been used for calculating the mixing ratio between freshwater and saline or brine, investigation of seawater evaporation and up coning processes (Thivya et al., 2016; Mirzavand et al., 2020b; Duan et al., 2022; Zhang et al., 2022). Chloride isotopes are commonly used to define salinity sources, mixing of different waters, and water-rock interaction (Du et al., 2016; Thivya et al., 2016; Sherif et al., 2019; Ercan et al., 2019; Awaleh et al., 2020).