Arabian Journal of Geosciences (2017) 10: 530 https://doi.org/10.1007/s12517-017-3314-4

ORIGINAL PAPER

Understanding groundwater chemistry in Mediterranean semi-arid system using multivariate statistics techniques and GIS methods: case of Manouba aquifer (Northeastern Tunisia) Hajer Ferchichi 1,2 & Boutheina Farhat 1 & Mohamed F. Ben-Hamouda 2 & Abdallah Ben-Mammou 1 Received: 17 July 2017 / Accepted: 30 November 2017 / Published online: 9 December 2017 # Saudi Society for Geosciences 2017

Abstract The rapid urbanization and industrialization of the Manouba plain (Northeastern Tunisia), the extensive agricultural expansion and the succession of dry years during recent decades have exerted greatly load on the water needs and lead to groundwater quality degradation. The aim of this study is to evaluate the processes controlling the groundwater mineralization of the shallow aquifer for determining its suitability for drinking and agricultural purposes. For establishing that, we combine several geological, hydrological and hydrochemical data with geostatistical techniques. The samples were collected at 17 sites covering 230 km2 of the study area and analyzed for major and trace components. The total dissolved solid (TDS) content ranges from 1372 to 3999 mg/l. The results of Piper diagram indicate that Na+/Cl− and Ca2+ > Na+/SO42− were the main dominant water types localized in the sloping sides of the watershed and near the saline depression; the suitability for irrigation use was also evaluated. The high concentrations of nitrates and chlorides are indicators of anthropogenic pollution, like the agricultural over application of nitrogen fertilizers and the discharge of domestic and industrial wastewater. Saturation indexes calculated by using PHREEQC (USGS) program show that groundwaters are undersaturated with evaporitic minerals (halite, gypsum) and saturated with carbonates (calcite, aragonite). The use of principal component analysis and hierarchical cluster analysis has shown that two main factors accounting 67.13% of the information of variability within the dataset confirm the existence of dissolution of evaporitic minerals and the mechanisms of nitrate increasing the salinity of the Manouba groundwater. Keywords Groundwater salinization . Hydrogeochemistry . Statistics . Plio-Quaternary aquifer . Northern Tunisia

Introduction Prediction of pollution trend in groundwater is especially problematic for the reason that aquifer systems are heterogeneous and they have long response times and so difficult to characterize. The salinization of groundwaters becomes a major problem underlying the strategic importance of water resources in all the world, particularly in semi-arid and arid

* Hajer Ferchichi [email protected] 1

Faculty of Sciences of Tunis, Department of Geology, Mineral Resources and Environment Laboratory (LRME), University of Tunis El Manar, 2092 Tunis, Tunisia

2

CNSTN, UMTN, Isotope Hydrology and Geochemistry Unit, Technopark of Sidi Thabet, 2020 Sidi Thabet, Tunisia

regions, since it places a decisive factor of its use for domestic or agricultural purposes (Edmunds 2003; Saidi et al. 2010; Zghibi et al. 2012; Singaraja et al. 2013; Deepesh and Madan 2015; Choudhary et al. 2016; Gharbia et al. 2016; Raheli-Namin et al. 2016; Nagaraju et al. 2016). Therefore, the hydrochemical differentiation of the salinization processes can be difficult to identify considering that many processes can induce several chemical signatures of the groundwater. There is a great number of paper (Zouhri et al. 2008; Ketata et al. 2011; Dickson et al. 2011; Zghibi et al. 2012; Twana et al. 2016; Abuelaish and Camacho Olmedo 2016) dealing with the groundwater salinization processes, and also the origin of increased salinity in both coastal and non-coastal areas. Groundwater chemistry reflects whether inputs from the atmosphere, soil and water-rock interaction pathways (weathering) (Park et al. 2005) as well as from pollutant sources such as mining, evaporate dissolution (Sanchez Martos et al. 1998), agricultural return flows (Stigter et al.

530 Page 2 of 15

1998; Ledesma-Ruiz et al. 2015; Singh et al. 2015; Tarki et al. 2016), fertilizer uses (Anju et al. 2010; Farhat et al. 2010), nitrate contamination (Wick et al. 2012; Zghibi et al. 2013), domestic and industrial wastes (Babiker et al. 2007). The Manouba aquifer has been selected as the study area. It is an example of the contaminated aquifers in the south Mediterranean area. Recently, it is recognized by a rapid urban and industrial development and by intensive agricultural activities. Therefore, the groundwater resources are mostly exploited for domestic and irrigation uses, leading to its deterioration. Nevertheless, the processes that affect groundwater chemistry in this area are not well understood. Previous geochemical studies in Manouba area (Wedman 1964; Chattaoui 1972; Nacef 1988; Chouari 2013; Khadhraoui 2013; Added et al. 2015) provided preliminary indications on chemical water characterization. However, the spatial expansion of groundwater characterization was not reported in any study. Furthermore, a better evaluation of the origin and the spatial extent of groundwater quality in this area is of strategic importance for water management. In this study, we compile available geochemical data with multivariate statistical techniques, geophysical and

Arab J Geosci (2017) 10: 530

hydrodynamic techniques to the knowledge and prediction of the main factors and mechanisms controlling the quality of the Manouba shallow aquifer. The geographical information tool was also used to create the spatial distribution maps by overlaying available data. This geochemical evaluation furnish insights into how the Manouba aquifer can advance in response to accelerated pressures from the demand for groundwater and will help to protect this vital resource and improve water planning strategies.

Geographic and geologic settings Geographic setting The Manouba aquifer is located in Northeastern Tunisia in West of the city of Tunis. It covers an area of about 230 km2 as the form of an ellipsis where the greater axis is oriented substantially NW-SE (Fig. 1). It exhibits a Mediterranean arid to semi-arid climate with hot dry summer and mild wet winter. The average

Fig. 1 Map location of the study area (NE Tunisia) DEM in Shuttle Radar Topography Mission (SRTM) digital elevation data (resolution 30 m) (NAZA 2017)

Arab J Geosci (2017) 10: 530

annual precipitation and temperature values are, respectively, below 489 mm and 20 °C (INM 2012). The evaporation has a significant role, and its influence on the repartition of salts is an indirect one (Wedman 1964; Nacef 1988). The average annual evaporation is about 1370 mm (INM 2012). The topography is slightly undulated to the north and the west. The Manouba plain, extending over an area of 53 km2, forms a subsident depression bordered by the crest line of Jb. Ammar, Jb. Naheli, Jb. Ain el Krima, Jb. Sidi Salah, Jb. Nadour and by a chain of low-lying hills forming the so-called «Barrier of Tunis». To the south, Jb. Et Tella surrounds the endorheic depression BThe Sejoumi lagoon^ (altitude less than 10 m) extending over an area of about 30 km2. The drainage system consists of several intermittent rivers that join the lagoon. Gueriana River is the most significant river, draining water from the Oued Lil zone (the southern slopes of Jb. Ammar) towards the Sejoumi lagoon over 15 km flowing in the Manouba plain (Fig. 2). The role of this river is not limited to the recharge of the aquifer, the collection of surface runoff and discharge to the lagoon, but also it receives the urban and industrial wastewater, allowing a permanent flow (Chouari 2013).

Fig. 2 Hydrography and urban area map of Manouba watershed

Page 3 of 15 530

Geology settings Recently, several authors have described the regional geology of the Northern Tunisia (Boutib 1998; Kacem 2004; Melki 1997; Mejri 2012; Ouerghi 2014). The local geology is characterized by high lateral facies variability and tectonic activities (Fig. 3). In outcrops, the geological succession extends from the Triassic to the Quaternary. The Triassic series (at Jebel Ammar and Jebel Tella) (Fig. 4) are formed by barioled marl and gypsum with an abnormal contact with the limestone marly series of Barremian (Boutib 1998; Kacem 2004; Melki 1997). The Manouba plain is surrounded by several hills composed by a sedimentary succession series extending from the Cretaceous to the Quaternary (limestone, sandstone, marls and claystone series) dipping towards the center of the watershed. These sediments, belonging to the Cretaceous and the Eocene, are covered with continental deposits from the Mio-plio-quaternary. These layers are partly eroded on the surrounding hills and covered with fluvial Quaternary material (Wedman 1964; Pimenta 1959). In the axial area, the total thickness of the Mio-plioquaternary series and Quaternary sandy and sandy clayey deposits is more than 600 m (Fig. 5).

530 Page 4 of 15

Arab J Geosci (2017) 10: 530

Fig. 3 Geological map of the study area

Hydrogeology settings The geomorphological features represented by digital elevation model (DEM) and the active tectonic environment make the Manouba area a host for several aquifers. The groundwater resources are evaluated at 8.5 Mm3/year. More than 1212 wells equipped with motor-driven pumps and extracting about 5.7 M m3/year were registered in 2015. Geophysical investigations and boreholes recompleted recently have allowed several details to understand the hydrogeology context of the study area (Mejri 2012; Ouerghi 2014). The reservoir consists of clayey-sandy and clay-sand alluvial deposits from the Plio-

quaternary and Quaternary continental materials. According to Nacef (1988), these deposits lie the major part of the shallow aquifer. The substratum is recognized by marly and clayey Cretaceous series. The supply of the groundwater is ensured by the direct inputs (infiltration of precipitation) and by the reliefs that surrounded it. The Sejoumi lagoon is considered the only natural discharge system that receives the most of the flows. Hence, the groundwater converges towards the umbilicus of the lagoon where it evaporates. In order to trace the piezometric map of the Manouba aquifer (Fig. 6), a measurement campaign of the groundwater was

Fig. 4 Lithological cross section BCD^ of Jb. Tella structure (Boutib 1998), modified

Arab J Geosci (2017) 10: 530

Page 5 of 15 530

Fig. 5 Lithological cross section AB of Manouba structure (Pimenta 1959), modified

made in December 2014. The layout of this map reveals different domains and the isopiezometric curves following the form of the topography. From Jb. Ammar to Manouba plain, the piezometric values are decreasing and the isopiezometric curves are almost equidistant and parallels to the Gueriana river and generally show a high hydraulic gradient probably due to the clayey sandy reservoir rock. This river plays a decisive role for the drainage of the aquifer. We can assert that

Fig. 6 Piezometric map of the Manouba shallow aquifer (December, 2014)

the northeastern area is the essential recharge zone for the Manouba plain (water collection area). In the western region (Sidi Hsine-Sejoumi), the isopiezometric curves reflect a flow from Jb. Ain krima and Jb. Sidi Salah towards the Sejoumi lagoon with an average hydraulic gradient. In Fouchana plain, the isopiezometric curves generally follow the form of the lagoon from the hills of the southern recharge area from Mohamedia (Jb.

530 Page 6 of 15

Nadour and Jb. Tella) with a low hydraulic gradient. The eastern region (the Barrier of Tunis) shows a second groundwater discharge zone and represents a second piezometric downstream part. The groundwater essentially flow is towards the Sejoumi lagoon which represents the principal outflow of all the aquifer.

Materials and methods The base maps (hydrologic, topographic and geologic maps) of the study area were scanned and digitized in the scale of 1:50,000. ArcGIS 10.1 and Surfer 12 softwares were used to map and analyze the data for the evaluation of groundwater quality.

GIS analysis A software platform (ARCGIS 10.1) was developed to improve the sorting, analysis, calculations, visualizations and interpretations of hydrogeochemical data in a GIS environment. The GIS platform allows the generation of maps of the spatial distribution of parameters in this work. Spatial patterns of groundwater quality parameters, over the area, such as TDS, chloride, nitrate and sulfate concentrations, were carried out using the Kriging method. The Kriging method is the most important geostatistical procedure that generates an estimated surface from scattered points with z-values. Contrary to other interpolation methods, to use the Kriging tool implies an interactive investigation of the spatial behavior of the phenomenon represented by the zvalues before selecting the best estimation method for generating the output surface (ESRI 2017).

Sample analysis A total of 17 groundwater samples were collected during December 2014 and analyzed for chemical parameters using standard procedures. The selected wells are uniformly distributed over the study area (Fig. 5). At the time of sampling, the samples were collected after pumping for 10 min from open dug wells. The sampling bottles were thoroughly rinsed two to three times. This was done to remove groundwater stored in the well. Immediately after sampling, pH was measured in the field using a multi-parameter WTW (Thermo Russel Model pH meter); electrical conductivity (EC) and Temperature (T) were measured using a pH-T-EC meter. Water samples were collected in 1000-ml polyethylene bottles with poly-seal caps for major elements. The groundwater sampled bottles were labeled, tightly packed and transported immediately to the laboratory of Hydrology and Isotopic Geochemistry from the National Center for Nuclear Sciences and Technologies (CNSTN) of the Technological pole of Tunisia when they

Arab J Geosci (2017) 10: 530

were immediately filtered through 0.45-μm filters on acetate cellulose and stored at 4 °C for chemical analyses. Chloride (Cl−), sulfate (SO42−) and nitrate (NO3−) were analyzed by means of high-performance ion chromatography produced by DIONEX Co. Calcium (Ca2+) and magnesium (Mg2+) concentrations were determined titrimetrically using 0.02 N ethyl diamin tetra acetic (EDTA). Bicarbonate (HCO3−) concentrations were determined by titration with 0.1 N HCl acid. Concentrations of sodium (Na+) and potassium (K+) were measured by flame photometry.According to the Freeze and Cherry (1979) charge balance definition, the chemical analyses for charge balance were defined as follows: %Charge balance error ¼

∑z:mc −∑z:ma ⋅100% ∑z:mc þ ∑z:ma

z is the absolute value of the ionic valence, mc is the molality of the cationic species and ma is the molality of the anionic species. The value of the ionic balance error for the chemical analyses may be within the acceptable limit of ± 5% of all hydrochemical datasets. The suitability of groundwater for domestic or agricultural purposes was estimated by comparing the values of the groundwater quality constituents with those of the World Health Organization (WHO 2004). The adapted methodology in this study is summarized as follows (Fig. 7).

Results and discussions Mineralization of groundwater The reactions between groundwater and the mineral compositions of the rocks influence the groundwater’s chemistry and are useful in understanding the origin of the mineralization (Ledesma-Ruiz et al. 2015). Temperature of water samples varies in a range between 14.7 and 22.5 °C, close to the yearly average temperature 20 °C (Table 1). The pH values are all neutral and fall within the range of 7.15 to 7.8. The Table 1 illustrates that groundwater in most of the Manouba phreatic aquifer exceeds the WHO TDS permissible for drinking water (TDS < 1000 mg/L) (Davis and De Wiest 1967; WHO 2004). The total dissolved solid (TDS) values range from 1372 to 3999 mg/l with a mean value of 2066.07 mg/l. High concentration of TDS is registered in the southeastern part of the watershed (M17 with 3351 mg/l) due to leaching of salts from soil and also in the northwestern part (M1, M2, M3, respectively, 3999, 3112 and 3296 mg/l) where domestic sewage may percolate into the groundwater. The order of abundance of the major cations was Na+ > Ca2+ > Mg2+ > K+ with a means values, respectively, 339.41, 193.54, 79.77 and 12.41 mg/l, and all the samples exceeded the desirable limit of drinking water for Ca2+ (75 mg/l) and the majority exceed

Arab J Geosci (2017) 10: 530

Page 7 of 15 530

Fig. 7 Flowchart showing the adopted methodology

the limit for Mg2+ (50 mg/l) (WHO 2004). The concentration of Na+ ranges from 204.7 to 903.9 mg/l. The maximum permissible limit of sodium in drinking water is 200 g/l; it reveals that all the samples are exceeding the permissible limit of WHO.

The general dominance of the anions was in the order of SO42− > Cl− > HCO3− > NO3− in most of the samples. The means values are, respectively, 681.03, 412.62, 282.57 and 32.63 mg/l. Likewise, Na+, SO42−, Cl− and NO3− are highly variable with standard deviations larger than the mean.

Table 1

In situ measurements and geochemical data of shallow groundwaters of Manouba, December 2014

Nom

pH

T

PL

TDS

Ca2+

Mg2+

Na+

K+

SO42−

Cl−

NO3−

HCO3−

Error

M1 M2 M3

7.24 7.15 7.54

(°C) 17.5 20.2 18.6

(m) 20.1 25.4 18.1

(mg/l) 3999 3112 3296

(mg/l) 250.8 179.4 175

(mg/l) 123.36 86.64 73.68

(mg/l) 894.7 754.4 903.9

(mg/l) 27.69 21.06 11.7

(mg/l) 487.65 674.22 687.16

(mg/l) 1674.34 943.52 961.38

(mg/l) 66.5 65.34 61.3

(mg/l) 473.68 387.5 421.6

% 2.8 1.6 5.1

M4 M5

7.49 7.37

17.2 15.5

30.9 39.4

2363 2360

176 110

79.44 61.8

554.3 464.6

3.51 16.77

492.12 369

753.44 560.68

48.71 33.3

255.44 295.12

4.2 4.2

M6 M7 M8 M9 M10 M11 M12

7.8 7.3 7.45 7.32 7.71 7.62 7.18

14.7 20 21 19 20 20 22.5

32.1 25.8 24.4 53.8 59 41.9 65

2300 1975 1387 1372 1529 1941 1730

154.4 212.8 166.8 147.2 155.2 185.2 223.5

102.72 89.52 66.84 62.88 63.84 81.84 43.26

434.7 273.7 204.7 209.3 271.4 338.1 219.59

12.48 15.6 9.75 8.97 14.43 13.26 5.88

552.32 522 394 273 341.4 422.52 720

735.6

34.65

272.8

610.71 338.59 377.91 383.39 586 150.5

11.44 4.5 48.6 18.69 52.11 48.94

239.32 202.12 243.66 280.24 261.64 318.42

2.3 2.8 4.5 2.1 5.2 1.2 1.4

M13 M14 M15 M16 M17 min Max Mean SD

7.53 7.3 7.53 7.75 7.55 7.15 7.8

20.8 21.1 20.7 19.2 21.6 14.7 22.5

30 17 33 30 13

1460 2719 2365 2073 3351 1372 3999 2066.07 563.75

83.99 213.95 291.56 192.58 396.43 83.99 396.43 193.54 77.3

43.05 103.09 110 90.46 117.98 43.05 123.36 79.77 23.81

243.15 520.17 303.4 267.88 446.69 204.7 903.9 339.41 120.63

27.27 5.2 27.74 8.4 4.46 3.51 27.74 12.41 7.66

562 1166 976 1000 1744 273 1744 681.03 409.08

92.3 305.3 369.2 142 371 92.3 1674.34 412.62 211.03

10.72 45.27 48.94 49.99 1.01 1.01 66.5 32.63 19.23

397.72 359.9 237.9 322.08 269.62 202.12 473.68 282.57 52.28

SD standard deviation, PL piezometric level

4.6 3.2 3.1 3.0 2.0

530 Page 8 of 15

Both in the case of nitrate and chloride, the highest concentrations were found in the northern urban area (respectively, 66.5 and 1674.34 mg/l). The lowest were found in the natural mountainous area in Jb. Sidi Salah. The sulfate concentration in this study area ranges between 273 and 1744 mg/l with an average value of 681.03 mg/l which indicates that all the samples out the desirable limit for drinking water (150 mg/l). It should be noted that the geochemistry of the study area is not homogenous. The available carbonates and sulfates in the rocks of the Manouba area might have been dissolved and thus added to the groundwater system during rainfall infiltration, irrigation and groundwater movement.

Arab J Geosci (2017) 10: 530 Table 2 Hydrogeochemical facies of the groundwater samples (Manouba aquifer 2014) Hydrogeochemical facies

Sample numbers

% of samples

Na+: Cl− Mixed Na+ > Ca2+: ClMixed Na+ > Ca2+: Cl− > SO42− Na+: SO42−

M1 to M6 M7, M9, M11 M8, M10 M13, M14

35.29 17.64 11.74 11.74

Ca2+ > Na+: SO42−

M12, M15 to M17

23.52

SO42− facies have the SO42− as the dominant ion. The amount of dissolved sodium may be mostly influenced by the processes of cation exchange.

Hydrogeochemical facies Durov diagram Trilinear diagram (Piper diagram) The projection of the water sample results in the Piper trilinear diagram (Fig. 8a) and Durov plot highlights the presence of cation exchange and salinization process or softening water from Manouba basin (Appelo and Postma 1993). The groundwater quality in the study area can be classified into five hydrogeochemical facies taking the ionic percentages in the relative decreasing order of their abundances (Table 2). They are Na + : Cl − , Na + > Ca 2+ : Cl − , Na + > Ca 2+ : Cl− > SO 4 2− , Na + : SO42−, Ca2+ > Na+: SO42−. From the cationic and anionic triangular files of Piper diagram, the majority of the groundwater samples (approximately 35.3%) is represented by NaCl facies. Na + : Cl − and Na + > Ca 2+ : Cl−facies showing the Cl− as the abundant ion. The abundance of chloride in the area reflects the discharge zone. It is noted that the Na+: SO42− and Ca2+ > Na+:

Durov diagram is a composite plot consisting of two ternary diagrams where the milliequivalents percentages of the cations of interest were plotted against that of anions of interest: sides form a central rectangular, binary plot of the total cations vs. total anions concentrations (Ravikumar 2015). Durov diagram provides more information on the hydrochemical facies by helping to identify the water types, and it can display some possible geochemical processes that could help understanding the quality of groundwater and its evaluation (Ghoraba and Khan 2013). The Durov diagram for the major cations and anions was plotted using RockWorks 15 software as given in Fig. 8b. The Duorv plot for Manouba groundwater samples indicates that most of the samples are in the phase of mixing dissolution with few in reverse ion exchange. From the data plots, it is apparent that the

Fig. 8 a Piper and b Durov diagrams depicting geochemical processes in Manouba groundwater

Arab J Geosci (2017) 10: 530

Page 9 of 15 530

total hydrochemistry is dominated by the major ions Cl, Na and Ca while other ions, such as Mg, SO 4 and HCO3, are comparatively less represented.

Correlation coefficient matrix Correlation matrix was processed for all data sets by using the STATTISTICA 8 software. The data matrix is the matrix of data of dimension x*i, where Bx^ is the number of well sampling observed (x = 1.....17) and Bi^ is the number of variables (as TDS and major ions) measured in all samples. Table 3 displays the association between variables. From correlation matrix, we noticed significant correlations between salinity and mineral salts, especially sodium (r2 = 0, 88), magnesium (r2 = 0, 77) and chloride (r2 = 0, 7). Chloride is strongly correlated with sodium (r2 = 0.84). The correlations indicate that HCO3− is positively (but moderate) correlated with Na+ (r2 = 0.51), but negatively correlated with Ca2+ (r2 = − 0.19) and SO42− (r2 = − 0.03). This is consistent with solutes which are removed from solution gradually by a variety or combination of mechanisms, such as mineral precipitation and cation exchange (Eugster and Jones 1979). In this case study, the amount of dissolved sodium is most probably influenced by the processes of cation exchanges (Wedman 1964).

Geochemical stability Saturation index (IS) has helped us to evaluate the main processes controlling water-rock interaction and the evolution of water chemistry. A comparison of the activities in water samples (ion activity product) and activities at equilibrium (solubility product), which result in the saturation state, helps to assess the evolutionary stage of the groundwater sample and identify the controlling geochemical reactions (Farhat et al. 2010; Ben Hamouda et al. 2013; Ledesma-Ruiz et al. 2015). PHREEQC software was used to calculate the IS for the groundwater samples (Parkhurst and Appelo 2013).

Table 4 Statistics minerals saturation index (SI) of Manouba shallow groundwaters, December 2014 Mean

Minimum

Maximum

Std.Dev.

SI aragonite

− 0.19

− 0.46

0.22

0.17

SI calcite

− 0.04

− 0.31

0.36

0.16

SI dolomite SI gypsum

− 0.18 − 0.80

− 0.64 − 1.14

0.57 − 0.20

0.30 0.25

SI halite

− 5.44

− 6.28

− 4.50

0.48

SI anhydrite

− 1.03

− 1.39

− 0.43

0.25

Saturation index (IS) = log [ion activity product]/KT. KT = equilibrium constant at temperature T. The increase in TDS in the analyzed waters could arise from the dissolution of evaporate minerals such as halite, anhydrite and gypsum. Gypsum and anhydrite are quite abundant, particularly in the Manouba aquifer. The results (Table 4; Fig. 9) show that waters are undersaturated with respect to anhydrite and halite minerals. A clear trend with growing TDS suggests that the soluble components are not limited by the mineral equilibrium. Thus, the dissolution of these minerals may occur. The majority of groundwater samples are saturated to oversaturated with respect to the calcite and the dolomite which are slightly soluble minerals. Precipitation of CaCO3 is still supported by the generally positive saturation indices (SI) for calcite. Locally, carbonate oversaturation could be due to an input excess of Ca 2+ and Mg 2+ ions from silicate weathering processes. This has especially been the case in the Manouba plain and near the lagoon area, where the flow velocities are low and the clay content of the aquifer is elevated. The dissolution of the dolomite can be inferred from the latter (Iranmanesh et al. 2014). The Ca2+ ions provided from the dissolution of sulfate minerals should be recaptured by the calcite precipitation, which is in agreement with the calcite saturation values (Farhat et al. 2010).

Table 3 Correlation matrix of the analyzed parameters of the plioquaternary unconfined aquifer of Manouba (NE Tuisia)

TDS Ca Mg Na K SO4 Cl NO3 HCO3

NO3 HCO3

Mg

Na

K

1 0.54 0.77 0.88 0.09 0.44 0.70 0.41 0.44

1 0.51 0.03 0.48 0.48 0.25 0.13

1 0.15 0.05 0.84 0.45 0.51

1 − 0.26 1 0.33 − 0.32 1 − 0.08 − 0.06 0.37 1 0.00 − 0.03 0.34 0.58 1

1 0.59 0.13 − 0.07 0.71 0.08 0.00 − 0.19

SO4

Cl

TDS Ca

Fig. 9 Calculated saturation indices (IS) versus total dissolved solids (TDS). SI was computed with respect to some carbonate and evaporitic minerals

530 Page 10 of 15

Spatial analysis with GIS The degradation of the groundwater quality, from the north to the south, follows the general groundwater flow direction of the shallow aquifer (contaminant percolation). According to Wedman (1964), the SE part of the lagoon is underlain at a shallow depth of the Eocene limestone sub-aquifer. The dissolved salt content is so elevated near the lagoon considering the increase of evaporation in this area and groundwater that dispersed near the surface (at depths less than 5 m). The increase of salinity, in the Bejaoua area (in the southern slopes of Jb. Ammar), is accompanied by chlorides and nitrate concentration increase (Fig. 10a). This region is increasingly occupied by urbanization which confirms the anthropogenic sources of groundwater pollution like domestic and industrial waste discharges, municipal effluents… The increase of

Arab J Geosci (2017) 10: 530

chloride concentration in the water is ordinarily considered as a tracer for contamination and taken as an index of pollution (Loizidou and Kapetanios 1993). From WHO (2004), chloride originates from natural sources, likewise sewage and industrial effluents, urban runoff and saline intrusion. Water samples from shallow monitoring wells in Northwestern urban areas (From Djedaida to Manouba plain) had the highest concentrations of chloride, respectively, 1674.34, 943.52 and 961.38 mg/l. Increases in chloride loads in this area may be related to the heterogeneity of factors, including essentially the wastewater discharge increase and leachate from landfills. The concentrations of NO3− in the groundwater are observed between 1.01 and 52.28 mg/l (Table 1). The groundwater shows a very low content of nitrates along the northwest region. According to Mencio and Mas-Pla (2008), the nitrate has not a lithological source. In natural conditions, the

Fig. 10 Spatial distribution of TDS content (a), chloride (b), nitrates (c) and sulfates (d) of the study area

Arab J Geosci (2017) 10: 530 Table 5 Eigen values of factors extracted through PCA, difference between factors and proportion of variance explained by the factors

Page 11 of 15 530

Eigenvalue

% Total-variance

Cumulative-Eigenvalue

Cumulative-%

F1 F2

3.82 2.22

42.42 24.71

3.82 6.04

42.42 67.13

F3

1.29

14.30

7.33

81.43

F4 F5

0.64 0.50

7.14 5.60

7.97 8.48

88.57 94.17

F6

0.30

3.34

8.78

97.51

F7 F8

0.21 0.01

2.37 0.12

8.99 9.00

99.88 100.00

F9

0.00

0.00

9.00

100.00

concentration of NO3− does not exceed 10 mg/l in the water. Therefore, the increase of nitrate concentration, exceeding 10 mg/l, is an indication of anthropogenic pollution. In this study, all samples show high nitrate concentration (> 10 mg/l) mainly due to the influence of the crop fertilization and the human activities that deliver nitrate to groundwater. On the other hand, the increase of salt content is accompanied by an increase of sulfate in the Southern area (Fig. 10d). The highest SO42− content and the positive correlation between Ca2+ and SO42− (r2 = 0.96) in the groundwater samples suggest the dissolution of gypsum (Triassic outcrops in Jb. Tella). On the other hand, especially in the southern part of the lagoon (the Fouchana plain), the groundwater depth is very low with a significant evaporation in which it causes the dissolution of evaporates like anhydrite and gypsum (CaSO4·2H2O). The positive correlation between Mg2+ and SO42− (r2 = 0.48) and the contribution of MgSO4 fertilizers highlights the significant role of the return flow from irrigation water in these agricultural regions.

Principal component analysis BPCA^ and cluster analysis Multivariate statistical techniques were used for grouping individuals or objects into unknown groups. These techniques can be used to group the commonly collected water quality data, where each cluster indicates the water of a particular quality. Several studies used these techniques to successfully classify water samples such as USSL 1954, Belkhiri et al. (2010), Arnous and El-Rayes (2012), Iranmanesh et al. (2014), EBLIN et al. (2014), Corniello and Ducci (2014), Masoud 2014, Zghibi et al. (2014), Ravikumar and Somashekar (2015). Comparisons based on multiple parameters from groundwater dataset were made and the samples were grouped according to their Bsimilarity^ to each other. The hydrochemical results of all the samples are statistically analyzed employing STATISTICA 8 software. The variables (TDS, calcium, magnesium, sodium,

potassium, sulfate, chloride, nitrate and bicarbonate) and 17 well sampling were analyzed adopting multivariate statistical techniques. The results of the factor analysis using the principal components and varimax rotation are presented in Table 5. To view the relationships between different parameters, a principal component analysis BPCA^ was performed. The principal component analysis allowed the discrimination of two axes which combine already 67.13% of the information. The axis F1 explains 42.42% of the variability in the parameters. The axis F2 has 24.71% of the variability of the parameters (Fig. 10). From PCA, it reveals that TDS, Na+, Cl−, Mg2+, Ca2+ and SO42− are very near to the correlation circle and are very well represented on the mapping (Fig. 11a). This shows that these elements are strongly correlated, and therefore, they probably have a common origin. In contrast, HCO3−, NO3− and K+ indicate that the provenance of each variable is mainly independent of each other. The results of the factor analysis are similar to the results of the correlation analysis. Based on distance matrix, the dendrogram of cluster analysis between variables highlights that variables (Fig. 11b) gather into four different clusters. The first one (C1) formed by TDS, chloride and sodium. The remaining variables, bicarbonates, calcium, magnesium and sulfate have a moderate correlation with the first group, formed the second cluster (C2). Hydrolysis of evaporite rocks and dissolution of carbonate rocks can explain the dominance of Na+ and Mg2+ as cations and Cl− and SO42− as anions in groundwater. These ions are derived from the weathering of rocks and hydrolysis of evaporate and some carbonate minerals locally in the continental part of the watershed. The third cluster (C3) includes the nitrates, which have a very low correlation with the other ions. This cluster highlights a mixed groundwater with an anthropogenic source (agricultural activity using chemical fertilizers). It certainly proves an anthropogenic pollution. The fourth one (C4) including potassium which has the less correlation with the others. That can be reflecting that this ion does not play an important role in the mineralization of waters.

530 Page 12 of 15

Arab J Geosci (2017) 10: 530

Fig. 11 a Behavior of the variables with respect to the first two factors (F1 and F2) and b hierarchical clustering dendrogram of the major chemical components of the Manouba aquifer

Water suitability for irrigation use The sodium adsorption ratio (SAR) is a assessment of groundwater quality for poses. The calculate of the SAR has because surface water is not always Fig. 12 Suitability of groundwater for irrigation in US Salinity Laboratory Staff diagram (USSL 1954)

measure of the irrigation purbecome useful available and

irrigation wholly related on groundwater. Groundwater with elevated sodium content is not suitable for agricultural purpose as it tends to deteriorate the soil (Sarath Prasanth et al. 2012). Therefore, as regards groundwater irrigation suitability, United States Salinity Laboratory Staff (USSL 1954), the SAR diagram was used to rate

Arab J Geosci (2017) 10: 530

the samples. SAR is a measure of alkali/sodium hazard to crops and it was estimated by the following formula: SAR ¼ Na=½ðCa þ MgÞ=20:5 Sodium, calcium and magnesium are in meq/l. Irrigation water with high SAR values can apply a longterm soil change and damage, because the sodium in the water can displace the calcium and magnesium in the soil. This can cause a decrease in the water infiltration and problems in the permeability causing crop production problems. In this case study, the results show that the majority of the samples is found in C4S2 which are classified unsuitable for irrigation (Fig. 12). While, only four samples collected showed a C4S1 classification with low SAR permissible for irrigation and five sampling sites are found in C4S3 class with high salinity and high alkalinity hazards, respectively. These results reveal that the water near the mountains zones is permissible for irrigation while contamination occurs higher essentially in the south near the Sejoumi lagoon and in the northern area. This may be due to the extension of the agricultural activities and the excessive use of the chemical fertilizers for irrigation practices. For this, special management plan for groundwater chemistry control became necessary.

Conclusion Adopting several methods such as satellite data (SRTM data, 30 m resolution), conventional maps, hydrochemical data, Geographic Information System utilities and statistical techniques demonstrate the anthropogenic inputs and natural sources of groundwater mineralization processes. The Manouba shallow aquifer shows a centripetal groundwater flow and a gradual increase of its total salt content towards the central west of the basin, where evaporation balances the inflow. The distribution of the groundwater samples in Piper diagram reveals that all of the groundwater samples fall under the Na+: Cl−, Na+ > Ca2+: Cl−, Na+ > Ca2+: Cl− > SO42−, Na+: SO42− and Ca2+ > Na+: SO42− facies. Spatial maps of groundwater quality parameters (TDS, chloride, nitrate and sulfate concentrations) indicate the distribution of the most areas affected by salinization. The increase in groundwater quality from the northeast to the southeast areas following the general groundwater flow direction is attributed to the percolation of contaminants in the shallow aquifer. The increase of nitrate concentrations (1.01 < NO3− < 52.4 mg/l) exceeding 10 mg/l is an indication of anthropogenic pollution which is mainly due to the high use of fertilizers in the agricultural activities in Fouchana plain and to the discharge of domestic wastewater in the urban area. Increased salinity (TDS achieve 3350 mg/l) with excessive sodium content (204.7 < Na < 554.3 mg/l) in the groundwater makes it

Page 13 of 15 530

unsuitable for irrigation. The SAR diagram shows that the majority of the groundwater samples are characterized by doubtful to unsuitable for irrigation. The contribution of MgSO4 fertilizers highlights the significant role of the return flow from irrigation water in the agricultural regions. Factor analysis identified the water quality variables responsible for spatial variations of the aquifer and estimated their loads. Two main factors accounted for 67.13% of the information of variability within the dataset. Factor 1 accounts for 42.42% of the variability in parameters and factor 2 for 24.71%. The first factor is strongly loaded with the salinity enhancement resulting mostly from the dissolution of evaporites minerals specially near the lagoon and near the Triassic outcrops. The second one contains HCO3−, NO3− and K+ indicating that the origin of each variable is mainly independent of each other. The higher values of the dissolved anions and cations in the Manouba area are caused simultaneously by the influences of geogenic sources (ion exchanges, salt evaporation, mineral dissolutions etc.) and anthropogenic (domestic and industrial wastewaters and excessive use of chemical fertilizers) following the topographical, geological and water flow-path conditions. This situation was patterned after the rapidly urbanizing of Manouba plain in the northern area and the intensification of the agricultural practices in the southern area. Finally, we believe that this paper helps to improve our understanding of the Manouba shallow aquifer contamination origins and could help expedite areas for future sustainable groundwater development plans. Acknowledgements The authors are very grateful to the Director of National Nuclear Research Institute for making funds available for this work. We also thank all the Technicians of the Isotope Hydrology and Geochemistry Unit, Technopark Sidi Thabet, Tunisia, for helping us during the sampling campaigns as well as the analysis.

References Abuelaish B, Camacho Olmedo MT (2016) Scenario of land use and land cover change in the Gaza strip using remote sensing and GIS models. Arab J Geosci 9(4):9–274. https://doi.org/10.1007/ s12517-015-2292-7 Added A, Ben Mammou A, Fernex F, Rezzougc S, Bernatb M (2015) Distribution of uranium and radium isotopes in an aquifer of a semiarid region (Manouba-Essijoumi, northern Tunisia). J Environ Radioact 82(3):371–381. https://doi.org/10.1016/j.jenvrad.2005.02. 010 Anju A, Ravi SP, Bechan S (2010) Water pollution with special reference to pesticide contamination in India. J. Water Resour Prot 2(05):432– 448. https://doi.org/10.4236/jwarp.2010.25050 Appelo CAJ, Postma D (1993) Geochemistry, groundwater and pollution, 2nd edn. Taylor and Francis, Great Britain 536p Arnous MO, El-Rayes AE (2012) An integrated GIS and hydrochemical approach to assess groundwater contamination in West Ismailia area. Egypt Arab J Geosci 6(8):2829–2842. https://doi.org/10.1007/ s12517-012-0555-0

530 Page 14 of 15 Babiker IS, Mohamed AAM, Hiyama T (2007) Assessing groundwater quality using GIS. Water Resour Manag 21(4):699–715. https://doi. org/10.1007/s11269-006-9059-6 Belkhiri L, Boudoukha A, Mouni L, Baouz T (2010) Application of multivariate statistical methods and inverse geochemical modeling for characterization of groundwater - a case study: Ain Azel plain (Algeria). Geoderma 159(3-4):390–398. https://doi.org/10.1016/j. geoderma.2010.08.016 Ben Hamouda MF, Mamou A, Bejaoui J, Froehlich K (2013) Hydrochemical and isotopic study of groundwater in the north Djeffara aquifer, gulf of Gabès, southern Tunisia. Int J Geosci 4(08):1–10. https://doi.org/10.4236/ijg.2013.48A001 Boutib L (1998)Tectonique de la région du Grand Tunis : Evolution géométrique et cinématique des blocs structuraux du Mésozoique à l’actuel (Atlas nord oriental de la Tunisie). Ph.D. Dissertation, Université Tunis, 151 p Chattaoui H (1972) Etude hydrogéologique de la plaine de ManoubaSejoumi par prospection électrique. Ph.D. Dissertation Sciences de la Terre, Strasbourg Institut de Physique du globe Chouari W (2013) Problèmes d'environnement liés à l'urbanisation contemporaine dans le système endoreïque d'Essijoumi (Tunisie nord-orientale). Physio-Géo 7-1:111–138. https://doi.org/10.4000/ physio-geo.3493 Choudhary S, Ramteke S, Rajhans KP, Sahu PK, Chakradhari S, Patel KS, Matini L (2016) Assessment of groundwater quality in Central India. J Water Resour Prot 8(01):12–19. https://doi.org/10.4236/ jwarp.2016.81002 Corniello A, Ducci D (2014) Hydrogeochemical characterization of the main aquifer of the BLitorale Domizio-agro Aversano NIPS^ (Campania-southern Italy). J Geochem Explor 137:1–10. https:// doi.org/10.1016/j.gexplo.2013.10.016 Davis SN, RJM de Wiest (1967) Hydrogeology. Journal of Hydrology 5: 98 Deepesh M, Madan KJ (2015) Identifying sources of groundwater contamination in a hard-rock aquifer system using multivariate statistical analyses and GIS-based geostatistical modeling techniques. J Hydrol: Reg Stud 4:80–110. https://doi.org/10.1016/j.ejrh.2014.11. 005 Dickson A, Abass G, Tetteh TA, Richmond F, Piotr M (2011) Hydrogeochemical evolution and groundwater flow in the Densu River basin, Ghana. J Water Resour Prot 3(07):548–556. https:// doi.org/10.4236/jwarp.2011.37065 Eblin SG, Soro GM, Sombo AP, Aka N, Kambiré O, Soro N (2014) Hydrochimie des eaux souterraines de la région d’ADIAKÉ (SudEst côtier de la Côte d’Ivoire). Larhyss Journal, ISSN 1112–3680, n°17, pp. 193–214 Edmunds WM (2003) Renewable and non-renewable groundwater in semi-arid and arid regions. Dev Water Sci 50:265–280 ESRI (Environmental Systems Research Institute) (2017). http://www. esri.com/ Eugster HP, Jones BF (1979) Behaviour of major solutes during closedbasin brine evolution. Am J Sci 279(6):609–631. https://doi.org/10. 2475/ajs.279.6.609 Farhat B, Ben Mammou A, Kouzana L, Chenini I, Podda F, De Giudici G (2010) Groundwater chemistry of the Mornag aquifer system in NE Tunisia. Resour Geol 60(4):377–388. https://doi.org/10.1111/j. 1751-3928.2010.00142.x Freeze RA, Cherry JA (1979) Groundwater. Prentice Hall, Englewood Cliffs Gharbia AS, Gharbia SS, Abushbak T, Wafi H, Aish A, Zelenakova M, Pilla F (2016) Groundwater quality evaluation using GIS based geostatistical algorithms. J Geosci Environ Prot 4(02):89–103. https://doi.org/10.4236/gep.2016.42011 Ghoraba Sh M, Khan AD (2013) Hydrochemistry and groundwater quality assessment in Balochistan province, Pakistan. https://www. arpapress.com/Volumes/Vol17Issue2/IJRRAS_17_2_06. pdf

Arab J Geosci (2017) 10: 530 INM (Institut National de Métérrologie) (2012) Données climatiques sur le Nord Est de la Tunisie Iranmanesh A, Locke RA, Wimmer BT (2014) Multivariate statistical evaluation of groundwater compliance data from the Illinois Basin-Decatur project. Energy Procedia 63:3182–3194. http:// creativecommons.org/licenses/by-nc-nd/3.0/. https://doi.org/10. 1016/j.egypro.2014.11.343 Kacem J (2004) Etude sismotectonique et évaluation de l’aléa sismique régional du Nord-Est de Tunis : Apport de la sismique réflexion dans l’identification des sources sismogéniques. Ph.D. Dissertation, Université Tunis el Manar, 200p Ketata M, Hamzaoui F, Gueddari M, Bouhlila R, Ribeiro L (2011) Hydrochemical and statistical study of groundwaters in Gabessouth deep aquifer (south- eastern Tunisia). Phys Chem Earth A/B/ C 36(5–6):187–196. https://doi.org/10.1016/j.pce.2010.02.006 Khadhraoui N (2013) Effets de l’urbanisation sur les ressources en eau de la plaine de Manouba. Ph.D. dissertation, Faculty of Sciences of Tunis, university Tunis el Manar, 148p Ledesma-Ruiz R, Pastén-Zapata E, Parra R, Harter T, Mahlknecht J (2015) Investigation of the geochemical evolution of groundwater under agricultural land: a case study in northeastern Mexico. J Hydrol 521:410–423. https://doi.org/10.1016/j.jhydrol.2014.12.026 Loizidou M, Kapetanios EG (1993) Effect of leachate from landfills on underground quality. Sci Total Environ 128(1):69–81. https://doi. org/10.1016/0048-9697(93)90180E Masoud AA (2014) Groundwater quality assessment of the shallow aquifers west of the Nile Delta (Egypt) using multivariate statistical and geostatistical techniques. J Afr Earth Sci 95:123–137. https://doi. org/10.1016/j.jafrearsci.2014.03.006 Mejri L (2012) Tectonique Quaternaire, paléoseismicité et sources seismogéniques en Tunisie Nord-Orientale : Etude de la faille d’Utique. Ph.D. Dissertation, Université de Toulouse 3 Paul Sabattier, 193p Melki F (1997) Tectonique de l’extrémité nord-est de la Tunisie (BizerteMenzel Bourguiba-Mateur). Evolution tectonique de blocs structuraux du Crétacé supérieur au Quaternaire. Ph.D. Dissertation, Université Tunis II, 213p Mencio A, Mas-Pla J (2008) Assessment by multivariate analysis of groundwater –surface water interactions in urbanized Mediterranean streams. J Hydrol 352(3-4):355–366. https://doi. org/10.1016/j.jhydrol.2008.01.014 Nacef ML (1988) Effets de l’urbanisation sur la nappe de Manouba. Mémoire de diplôme d’études approfondies (DEA) en Sciences de la Terre, Université de Tunis, Faculté des Sciences, 53p Nagaraju A, Muralidhar P, Sreedhar Y (2016) Hydrogeochemistry and groundwater quality assessment of Rapur area, Andhra Pradesh, South India. J Geosci Environ Prot 2016(4):88–99. https://doi.org/ 10.4236/gep.2016.44012 NAZA (National Aeronautics and Space Administration) (2017) Digital Elevation Model in Shuttle Radar Topography Mission of Manouba area in Tunisia. http://opentopo.sdsc.edu/datasets Ouerghi S (2014) Intégration des données multisources (Géologiques, sismologiques, géophysiques et géomorphomètriques) dans un environnement SIG pour l’analyse structurale du Nord Est de la Tunisie. Ph.D. Dissertation, University of Sfax, Ecole Nationale d’Ingénieurs de Sfax, 271 p Park SC, Yun ST, Chae GT, Yoo IS, Shin KS, Heo CH, Lee SK (2005) Regional hydrochemical study on salinization of coastal aquifers, western coastal area of South Korea. J Hydrol 313(3-4):182–194. https://doi.org/10.1016/j.jhydrol.2005.03.001 Parkhurst DL, Appelo CAJ (2013) Description of input and examples for PHREEQC version 3-a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Techniques and Methods, Book 6, Chap. A43, 497 p

Arab J Geosci (2017) 10: 530 Pimenta J (1959) Le cycle pliocène-actuel dans les bassins paraliques de Tunis. Mém Soc Géol France 85:35–40 Raheli-Namin B, Mortazavi S, Mobinifar M, Adeli M (2016) Groundwater-quality probability mapping and assessment for domestic and irrigation purposes in Ghara-su Basin of Golestan Province. Iran J Mater Environ Sci 7(1):259–271 Ravikumar P (2015) A comparative study on usage of Durov and Piper diagrams to interpret hydrochemical processes in groundwater from SRLIS. https://www.researchgate.net/publication/273886861 Ravikumar P, Somashekar RK (2015) Principal component analysis and hydrochemical facies characterization to evaluate groundwater quality in Varahi river basin, Karnataka state. India Appl Water Sci 7(2): 745–755. https://doi.org/10.1007/s13201-015-0287-x Saidi S, Bouri S, Ben Dhia H (2010) Groundwater vulnerability and risk mapping of the Hajeb-jelma aquifer (Central Tunisia) using a GISbased DRASTIC model. Environ Earth Sci 59(7):1579–1588. https://doi.org/10.1007/s12665-009-0143-0 Sanchez Martos F, Pulido Bosch A, Calaforra JM (1998) Hydrogeochemical processes in arid region of Europe (Almeria, SE Spain). Appl Geochem 14:735–745 Sarath Prasanth SV, Magesh NS, Jitheshlal KV, Chandrasekar N, Gangadhar K (2012) Evaluation of groundwater quality and its suitability for drinking and agricultural use in the coastal stretch of Alappuzha District, Kerala. India Appl Water Sci 2(3):165–175. https://doi.org/10.1007/s13201-012-0042-5 Singaraja C, Chidambaram S, Anandhan P, Prasanna MV, Thivya C, Thilagavathi R, Sarathidasan J (2013) Hydrochemistry of groundwater in a coastal region and its repercussion on quality, a case study-Thoothukudi district, Tamilnadu India. Arab J Geosci 7(3): 939–950. https://doi.org/10.1007/s12517-012-0794-0 Singh S, Raju NJ, Ramakrishna C (2015) Evaluation of groundwater quality and its suitability for domestic and irrigation use in parts of the Chandauli-Varanasi region, Uttar Pradesh, India. J Water Resour Prot 7(07):572–587. https://doi.org/10.4236/jwarp.2015.77046 Stigter TY, Van Ooijen SPJ, Post VEA, Appelo CAJ, Carvalho Dill AMM (1998) A hydrogeological and hydrochemical explanation of the groundwater composition under irrigated land in a Mediterranean environment, Algarve, Portugal. J Hydrol 208(3–4):262–279. https://doi.org/10.1016/S0022-1694(98)00168-1

Page 15 of 15 530 Tarki M, Ben Hammadi M, El Mejri H, Dassi L (2016) Assessment of hydrochemical processes and groundwater hydrodynamics in a multilayer aquifer system under long-term irrigation condition: a case study of Nefzaoua basin, southern Tunisia. Appl Radiat Isot 110(56):138–149. https://doi.org/10.1016/j.pce.2010.03.039 Twana OA, Salahalddin SA, Nadhir AA (2016) Groundwater assessment of Halabja Saidsadiq Basin, Kurdistan region, NE of Iraq using vulnerability mapping. Arab J Geosci 9(3):9–223. https://doi.org/ 10.1007/s12517-015-2264-y USSL (United States Salinity Laboratory Staff) (1954) Diagnosis and Improvement of Saline and Alkali Soils. US Department of Agricultural Soils. US Department of Agricultural (USDA). Hand Book 60, Washington, 69-81p Wedman EJ (1964) Geohydrology of sebkra Sedjoumi (TUNISIA). Édit. AIHS Publication, n° 64, p 50–67 WHO (World Health Organization) (2004) Guidelines for drinking-water quality, vol 1, 3rd edn, recommendations edn. WHO, Geneva, pp 145–220 Wick K, Heumesser C, Schmid E (2012) Groundwater nitrate contamination: factors and indicators. J Environ Manag 111(3):178–186. https://doi.org/10.1016/j.jenvman.2012.06.030 Zghibi A, Zouhri L, Tarhouni J, Kouzana L. (2012) Groundwater mineralisation processes in Mediterranean semi-arid systems (CapBon, North east of Tunisia): hydrogeological and geochemical approaches. Hydrol. Process. Published online in Wiley Online Library (wileyonlinelibrary.com). https://doi.org/10.1002/hyp.9456 Zghibi A, Tarhouni J, Zouhri L (2013) Assessment of seawater intrusion and nitrate contamination on the groundwater quality in the Korba coastal plain of cap-bon (north-east of Tunisia). J Afr Earth Sci 87: 1–12. https://doi.org/10.1016/j.jafrearsci.2013.07.009 Zghibi A, Merzougui A, Zouhri L, Tarhouni J (2014) Understanding groundwater chemistry using multivariate statistics techniques to the study of contamination in the Korba unconfined aquifer system of cap-bon (north-east of Tunisia). J Afr Earth Sci 89:1–15. https:// doi.org/10.1016/j.jafrearsci.2013.09.004 Zouhri L, Carlier E, Ben Kabbour B, Toto EA, Gorini C, Louche B (2008) Groundwater interaction in the coastal environment: hydrochemical, electrical and seismic approaches. Bull Eng Geol Environ 67(1):123–128. https://doi.org/10.1007/s10064-007-01016