Investigation of groundwater mineralization in the Hammamet–Nabeul unconfined aquifer, north-eastern Tunisia: geochemical and isotopic approach

Abstract

Detailed hydrogeochemical and isotopic data of groundwaters from the Hammamet-Nabeul unconfined aquifer are used to provide a better understanding of the natural and anthropogenic processes that control the groundwater mineralization as well as the sources of different groundwater bodies. It has been demonstrated that groundwaters, which show Na-Cl and Ca-SO 4 -Cl water facies, are mainly influenced by the dissolution of evaporates, the dedolomitization and the cation-exchange process; and supplementary by anthropogenic process in relation with return flow of irrigation waters. The isotopic signatures permit to classify the studied groundwaters into two different groups. Non-evaporated groundwaters that are characterized by depleted d 18 O and d 2 H contents highlighting the importance of modern recharge at higher altitude. Evaporated groundwaters with enriched contents reflecting the significance infiltration of return flow irrigation waters. Tritium data in the studied groundwaters lend support to the existence of pre-1950 and post-1960 recharge. Carbon-14 activities in shallow wells that provide evidence to the large contamination by organic 14 C corroborate the recent origin of the groundwaters in the study area.

Application of geochemical tracers for the investigations of groundwater resources in semi‐arid region (Central‐East Tunisia)

“…These samples define a straight red line ( R 2 2 = 0.878) with a slope of −0.986 (Figure 5b) and explained by a cation exchange process (type II) (Ma et al, 2009; Stigter et al, 1998). This process, which is characterized by the exchange of Ca 2+ and Mg 2+ in the waters with an earlier adsorbed of Na + on the surface of clay minerals in the aquifer matrix, is represented by the following equation (Guo & Wang, 2005, cited in Ben Moussa et al, 2010): $$$$ {\mathrm{Na}}_2-\mathrm{clay}\left(\mathrm{s}\right)+\left({\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}\right)\to \left({\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}\right)-\mathrm{clay}\left(\mathrm{s}\right)+{2\mathrm{Na}}^{+}. $$$$ …”

“…Different methodologies have been used to understand those processes. First, the hydrogeochemistry investigation, which is the famous one, is the subject of numerous studies (such as Ben Moussa et al, 2010; Charfi, Trabelsi, et al, 2013; Farid, Trabelsi, Zouari, & Beji, 2013; Kammoun et al, 2018; Re et al, 2017; Trabelsi et al, 2012, etc.). This methodology is based on the use of chemical and isotopic parameters of the studied water in order to define the origin of the groundwater salinization.…”

Incorporating the social dimension into hydrogeochemical investigations for rural development: the Bir Al-Nas approach for socio-hydrogeology

“…This area was chosen because it represents issues shared by most of the coastal aquifers in the Mediterranean Basin (i.e., aquifer pollution and salinization, water overexploitation, saline-water intrusion, and agricultural return flow). In addition, this area has been the subject of several national and international investigations and projects (e.g., Kouzana et al 2010;Ben Hamouda et al 2011;Ben Moussa et al 2010, 2011a, 2011b, 2012Cary et al 2013), which have resulted in a good knowledge of the baseline condition of the natural environment and well-established cooperation between the local institutions working in the region. This makes the area adequate for testing the new proposed methodology.…”

Influence of precipitation and deep saline groundwater on the hydrological systems of Mediterranean coastal plains: a general overview

“…Water in all deep-drilled wells in the central sectors of peri-Mediterranean coastal plains consistently shows increasing salinity with depth, indicating the ubiquitous presence of a deep saline brine (Issar 1968, Wright 1985, Wright and Burgess, 1992, Crampon et al 1996, Barazzuoli et al 1996, Taniguchi et al 2003, Edmunds et al 2003, Saad et al 2004, Weinthal et al 2005, Shagar et al 2006, Grassi et al 2007, Trabelsi et al 2009, Edmunds 2009, MacDonald et al 2009, Ben Moussa et al 2010. Depth profiles of sulphur, nitrogen and carbon dissolved compounds, as well as changes in earth-alkaline concentration, can be used to characterize processes typically determined by the bacterial processes of decomposition of organic matter.…”