Vol.:(0123456789) 1 3 Environmental Earth Sciences (2018) 77:557 https://doi.org/10.1007/s12665-018-7716-8 ORIGINAL ARTICLE Hydrochemical characterization and geospatial analysis of groundwater quality in Cap Bon region, northeastern Tunisia Abdelaziz Sebei 1  · Tarek Slama 1  · Mohamed Amine Helali 1 Received: 10 March 2018 / Accepted: 7 July 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract The hydrogeochemical characteristics of shallow groundwater in the Grombalia region, northeastern Tunisia, were inves- tigated to evaluate suitability for irrigation and other uses and to determine the main processes that control its chemical composition. A total of 21 groundwater samples were collected from existing wells in January–February 2015 and were analyzed for the major cations and anions concentrations. Conductivity, pH, T°, O 2 and salinity were also measured. Interre- lationships between chemical parameters were determined by using the scatter matrix method. The suitability of groundwater for irrigation and other uses was assessed by determining the sodium adsorption ratio, soluble-sodium percentage, total dis- solved solids, total hardness, Kelly’s index and permeability index values of water samples. The spatial distribution of key parameters was assessed using a GIS-based spatial gridding technique. This analysis indicated that the chemical composi- tion of groundwater in the study area is of Cl–SO 4 –Na–Ca mixed facies with concentrations of many chemical constituents exceeding known guideline values for irrigation. The salinity of groundwater is controlled by most dominant cation and anion (Na–Cl). A correlation analysis shows that Na + is the dominant cation and that reverse ion exchange is a dominant process that controls the hydrogeochemical evolution of groundwater in the area. Geospatial mapping of hydrochemical parameters and indices analyzed with the USSL and Wilcox diagrams show distinctive areas of irrigation suitability. In contrast, 76.2% of samples fall in the highly doubtful to unsuitable category and indicate that the central and north-eastern parts of the study area are unsuitable for irrigation due to a high salinity and alkalinity. Keywords Hydrochemistry · Scatter matrix analysis · Geospatial zoning · Water quality · Grombalia aquifer Introduction In arid and semi-arid areas, groundwater is often the domi- nant resource used for agricultural and industrial water sup- plies. During recent decades, it has been observed that the over-pumping and increasing land use activities are posing great threat to the availability of groundwater and to its qual- ity all over the world (Mor et al. 2006). These issues have also been reported in the Cap Bon, an agricultural area with various industrial activities in north- eastern Tunisia (Fig. 1). Large volumes of groundwater in this region are pumped from the Grombalia basin (GB) for agricultural, industrial and domestic purposes. The increased industrial and agricultural development of this region has also greatly increased the demand for water which has adversely afected the quality of both surface and groundwa- ter resources in the region (Ben Moussa et al. 2009; Bouksila et al. 2013; Ameur et al. 2016). Moreover, with the absence of a management plan and signifcant groundwater manage- ment policies, groundwater use in some parts of the basin exceeds natural recharge rates (DGRE 1998; Sebei et al. 2004). In addition, the GB aquifer is considered to be the most vulnerable aquifer in the region since it is a shallow near- coastal aquifers system that is highly vulnerable to contam- ination. These conditions impose signifcant management challenges and there is a need for rigorous policies to protect * Abdelaziz Sebei abdelaziz.sebei@fst.utm.tn Tarek Slama trslama@gmail.com Mohamed Amine Helali he.amine@gmail.com 1 Faculty of Sciences of Tunis, Department of Geology, University of Tunis El Manar, El Manar II, 2092 Tunis, Tunisia