Salinization Risk Assessment of Soil and Groundwater: a Case Study in Sidi El Hani Basin (Central-Eastern Tunisia)

European Journal of Scientific Research ISSN 1450-216X / 1450-202X Vol. 147 No 4 November, 2017, pp. 412-425 http://www. europeanjournalofscientificresearch.com

Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia)

M’nassri Soumaia Département du Génie des Systèmes Horticoles et du Milieu Naturel Université de Sousse, Institut Supérieur Agronomique de Chott Mariem BP 47, 4042 Chott Mariem, Tunisie E-mail: [email protected] Tel: +21696714748

El Amri Asma Département du Génie des Systèmes Horticoles et du Milieu Naturel Université de Sousse, Institut Supérieur Agronomique de Chott Mariem BP 47, 4042 Chott Mariem, Tunisie E-mail: [email protected]

Dridi Lotfi Département du Génie des Systèmes Horticoles et du Milieu Naturel Université de Sousse, Institut Supérieur Agronomique de Chott Mariem BP 47, 4042 Chott Mariem, Tunisie E-mail: [email protected]

Tagorti Mohamed Département des Sciences Biologiques Institut Supérieur de Biotechnologie de Monastir, BP 56, 5000 Monsatir, Tunisie E-mail: [email protected]

Hachicha Mohamed Laboratoire de Valorisation des Eaux Non Conventionnelles Institut National de Recherches en Génie Rural, Eaux et Forêts, BP 10, 2080 Ariana, Tunisie E-mail: [email protected]

Majdoub Rajouene Département du Génie des Systèmes Horticoles et du Milieu Naturel Université de Sousse, Institut Supérieur Agronomique de Chott Mariem BP 47, 4042 Chott Mariem, Tunisie E-mail: [email protected]

Abstract

The aquifer of Sidi El Hani, located in the central-eastern part of Tunisia, is the main source for irrigation activities. However, in the last decades, it is largely threatened by salinization. Therefore, a campaign of groundwater samples was carried out in the Ouled Chamekh plain. A campaign of soil samplings was also performed in a parcel located in the study area. A 27 soil samples were collected with a total depth reached 30 m. In addition to the experimental approach, we used statistical and hydrochemical analysis to assess the Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia) 413

major processes of salinization of soil and groundwater. The results show that the degradation of the groundwater quality mainly results from natural factors such as rock weathering and anthropogenic factors associated with the irrigation water return. Moreover, based on the generalized Residual Alkalinity (RA) concept, calcite and gypsum have a tendency to precipitate when the soil solution gets concentrated under evaporation. This is in agreement with the saturation index. Furthermore, the RA reveals that the soil solution follows a neutral saline pathway.

Keywords: soil degradation, groundwater salinization, residual alkalinity, concentration factor, Sidi El Hani..

Introduction Nowadays, groundwater salinization is considered as a common chanllange faced by many countries all over the world. This problem is most severe in arid and semi-arid regions where freshwater resources tend to be scarce. The groundwater salinization is largely caused by natural processes that can be accelerated by the anthropogenic activities. Indeed, the salinization of groundwater can be due to evaporation, water-rock interaction (Risacher and Fritz, 2009; Lucas et al ., 2010), seawater intrusion (Fadili et al., 2016), upconing of saline waters from deep layers (Zammouri et al., 2007) and irrigation return flow (Jiang et al., 2009; Najib et al., 2017). Saline groundwaters used in irrigation, particularity in arid and semi-arid regions (Bouarfa et al., 2009), affect the soil as well as the crop yields (Louati et al., 2015). The most harmful effects associated to its use are sodification, salinization and alkalinization, which may alter soil structure (Hachicha et al., 2010). The unconfined aquifer of Sidi El Hani, located in the central-eastern part of Tunisia, constitutes the only water table resource available for agricultural use. This is, especially attributed to the scarcity of surface water, which is limited to the sabkhas and wadi Cherita. In these last decades, this aquifer suffers from an increasing vulnerability to salinization due to an ever increasing population and irrigation needs. As a consequence, the water salinity varies between 4 and 8 g/l (Majdoub et al., 2012). Therefore, the irrigated lands of this region are characterized by a progressive salinization (Louati et al., 2015), which may lead, in the medium term, to a reduction in agricultural land and to a future economic instability of the area. Furthermore, it is more important to understand the relation between the groundwater quality and soil processes in order to help farmers to adopt the appropriate soil and water management strategies and integrate the sustainable management of groundwater resources. The current study aims to assess the major processes of soil and groundwater salinization using a combination of physical, chemical and mineralogical analysis, in sequence to obtain a general understanding on the soluble salts availability in the system soil-groundwater.

2. Material and Methods 2.1 Study Area The study area is the Ouled Chamekh plain located in center-east of Tunisia. It is surrounded by the mountain chains of El Guessat and Ktitir that barely reach more than 100 m of altitude in the western part. The eastern and southern parts are occupied by the endorheic depression of the sabkhas of Sidi El Hani and Cherita (Fig. 1). It is characterized also by an undeveloped hydrographic network (Essefi et al., 2013). The study area is classified as a semi-arid area with an annual average precipitation of 270 mm. January and February are considered as the coldest months of the year, where the average maximum temperature is 16°C and the minimum is 8°C. August is considered as the hottest month 414 M’nassri Soumaia, El Amri Asma, Dridi Lotfi, Tagorti Mohamed, Hachicha Mohamed and Majdoub Rajouene with an average temperature of 30°C. The average annual relative humidity is around 71 and 50%, respectively, in November and July.

Figure 1: Location map of the Ouled Chamekh plain

According to the geological setting, the study area is extended from the lower Pleistocene to Holocene Fig. 2. The Pleistocene is mainly composed of detrital formations, limestone, marls and a lenticular of gypsum that are outcropped in the El Guessat and Ktitir mountains (Tagorti et al., 2013; Essefi et al., 2014). The Holocene is the dominant formation in the study area. It is characterized by sands, silts, clays, and gypsum. The structural framework is characterized by the presence of several synclines and anticlines. In this plain, two anticlines were detected such as the El Guessat and Ktitir anticlines. These structures are separated by a vast plain which take place within a collapsed zone with a synclinal form. They were occupied by the sabkhas of Sidi El Hani and Cherita, which are composed of salt with evaporate deposits of halite and gypsum. According to the tectonic network, the structure of the study area is strongly controlled by the outcrops of the Mio-Plio-Quaternary such as the faults of Ktitir, Hajeb Layoun and Sidi El Hani. The fault line of Sidi El Hani causes the subsidence of the sabkha of Sidi El Hani in the eastern boundary of the study area. The direction of groundwater flow of Sidi El Hani aquifer is mainly from the west to the sabka of Sidi El Hani in the north-east and to the sabkha of Cherita in the south with a velocity ranging between 29 10 -6 and 49 10 -6 m/s. Referring to a previous piezometric surface map (Dridi et al., 2014), the thickness of Sidi El Hani aquifer varies from 3 m, at the eastern part of the basin, up to 50 m, in the center. The hydraulic head varies between 35 and 80 m NGT (Tunisian General leveling System). Irregularities of the water table contours indicate high variation of the hydraulic conductivity of the alluvial aquifer from the west to the south and east due to the heterogeneity of sediments. The transmissivity varies between 2×10 -4 and 5×10 -3 m2/s and the hydraulic gradients are in the order of 0.3 to 0.45%.

Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia) 415

Figure 2: Geological setting of Ouled Chamekh plain

(ONM, 1985: Echelle 1:50000)

2.2 Sampling and Analytical Techniques For this study, 49 water samples were collected in March and April 2015 from different wells that are used for irrigation. The static levels of the wells vary between 5 and 26 m (Fig. 3a). All sampling water was taken after pumping water for around 15 to 20 min. In addition to the groundwater, a campaign of soil samplings was also performed in a parcel located in the study area (Fig. 3b). The 27 soil sampled depth reached 30 m. various techniques, depending on the lithology, were used for extracting soil samples. Core drilling was suitable for clayey layers, whereas a rotary drilling using a tri-cone roller bit was performed in sandy layers.

Figure 3: Location of the water samples (a) and the parcel of soil samples (b).

416 M’nassri Soumaia, El Amri Asma, Dridi Lotfi, Tagorti Mohamed, Hachicha Mohamed and Majdoub Rajouene

2.2.1 Ground Water and Soil Physio-Chemical Analysis Water temperature, pH and electrical conductivity (EC) were measured in situ. The collected groundwater samples were analyzed in the laboratory. For total dissolved salts (TDS), cations (Ca 2+ , 2+ + + - - 2- Mg , K and Na ) and anions (Cl , HCO 3 and SO 4 ), the standard methods suggested by the American Public Health Association were used (APHA, 2005). TDS were measured by evaporating a pre-filtered sample to dryness, K + and Na + were determined by flame atomic absorption 2+ 2+ - - spectrophotometry. In the case of Ca , Mg , Cl and HCO 3 , they were analyzed by volumetric 2- methods. Whilst, SO 4 were determined by the calorimetric spectrophotometry. All the acquired data were incorporated into hydrochemical database in order to highlight the processes that influenced the actual chemical composition of groundwater. For the soil samples, the texture was determined using particle size analysis. The granular fractions were measured using Robinson method. Then soils were classified according to the USDA classification using the free software Triangle. The EC e and major 2+ 2+ + + - - 2- ions (Ca , Mg , K , Na , Cl , HCO 3 and SO 4 ) were determined on saturated soil pastes extracted by the same technique used in the case of groundwater analysis (Roades et al., 1999). The accuracy of the chemical analyses was carefully studied using a repeated analysis of the water samples and by calculating the percent charge balance error (% CBE). The results of the analysis were judged to be acceptable when the CBE does not exceed ±5%.

2.2.2 X-Ray Diffraction Analysis The mineralogical analysis of the soil was done by X-ray diffraction (XRD) to identify the clay, the primary and the secondary minerals. This technique has been more and more undertaken in various studies to identify the precipitated salts (Abdelfattah et al., 2009). The methodology for preparing the samples consists of grinding a small amount of soil until a very fine powder is obtained. The resulting powder was then analyzed by a diffractometer. The mineralogical analysis of the clay fraction (<2 μm) was determined on aggregates using a PHILIPS PW 1050/25.

2.2.3 Statistical Analysis Statistical analyses based on principal components analysis (PCA) and the Pearson correlation coefficients were carried out using the Statistical Package for the Social Sciences (SPSS, software version 18). The Kolmogorov Smirnov test was performed to examine the frequency distribution of the dataset of the major element concentrations in the groundwater. After a log transformation in order to achieve a normal and homogeneity distribution, PCA were rotated using the Varimax rotation method and eigenvalues greater than 1. This was confirmed by the index of KMO higher than 0.5 and by the test of sphericity of Bartlett with a value lower than 0.001, suggesting that PCA was successful in dimension reduction.

2.3.4 Geochemical Characterization Several hydrochemical tools have been used in this study such as correlations between different major elements and Wilcox diagram in order to characterize the physical and chemical process of soil and groundwater salinization. In addition, the activity of each species of soil samples was calculated with PHREEQC (Parkhurst and Appelo, 1999). A concentration factor (CF) was done using the chlorides as references to appreciate the concentration level of each soil samples, The chlorides are well thought- out as tracers as they are not involved in salinization processes such as dissolution, precipitation and exchange cations (Nezli et al., 2007). The CF was calculated as follows: CF = ( ) (1) Cli: chloride concentrations of the samples (me/l) and Cl0: chloride concentrations of the soil samples with lowest chloride concentrations (me/l).

Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia) 417

Furthermore, a generalized concept of residual alkalinity (RA) was calculated to evaluate the successive precipitation of the minerals in the soil. This concept was calculated as follows (Droubi et al., 1976): 2+ 2- RAcalicte + gypsum = Alk − [Ca ] – [Mg ] + [SO 4 ] (2) 2+ 2+ 2- Alk, [Ca ], [Mg ] and [SO 4 ] are in (me/l). 2+ 2+ 2- When RA is negative: alkalinity decrease, [Ca ] and [Mg ] increase, [SO 4 ] decrease and the solution follows the neutral saline with the dominant of the chlorides pathway. In the opposite case, the solution follows the neutral alkaline with the dominant of the gypsum pathway.

3. Results and Discussion 3.1 Physico-Chemical Characteristics of Ground Water Table 1 shows some descriptive statistics for the 11 physico-chemcial parameters deduced from the 49 groundwater samples. The temperature of groundwater samples ranges between 18 and 29°C with an estimated average of 24°C. The pH values vary from 6.88 to 8.50 with a mean value of 7.64. The EC ranges from 3.75 to 12.00 dS/m corresponding to TDS varying between 2400 and 8413 mg/l with a mean of 4707 mg/l. Concentrations of Ca 2+ range from 4.33 to 35.0 me/l with an average of 17.39 me/l, while concentrations of Mg 2+ are between a minimum of 5.0 me/l and a maximum of 38.0 with a mean value of 18.35 me/l. In addition, Na + concentrations range from 17.86 to 63.56 me/l with an average of 37.06 me/l. Whereas, the K + concentrations are comprised between a minimum of 0.36 me/l and a maximum of 1.80 me/l. The Na +, Mg 2+ and Ca 2+ seem to be the dominant cations. Regarding to the anions, the Cl - concentrations vary between 20.46 and 75.12 me/l with a mean value of 40.94 me/l. - 2- However, the concentrations of HCO 3 range from 2 to 8 me/l, while the SO 4 concentrations are - 2- comprised between 13.28 and 57.00 me/l. As a consequence, the Cl and SO 4 are the dominant anions in the groundwater, which could be associated mainly to the lithological heterogeneities.

Table 1: Descriptive statistics of chemical composition of groundwater in Sidi El Hani basin (N=49).

Mean Min. Max. SD T (°C) 24.00 18.00 29.00 2.14 pH 7.64 6.88 8.50 0.36 EC (dS/m) 6.46 3.75 12.00 1.96 TDS (mg/l) 4707 2400 8413 1493 Ca 2+ (me/l) 17.39 4.33 35.0 5.87 Mg 2+ (me/l) 18.65 5.00 38.00 8.38 Na + (me/l) 37.06 17.86 63.56 11.88 K+ (me/l) 0.71 0.36 1.80 0.27 Cl - (me/l) 40.94 20.46 75.12 13.15 - HCO 3 (me/l) 4.92 2.0 8.0 1.78 2- SO 4 (me/l) 29.11 13.28 57.0 9.56

Table 1 reflects in addition a low to high concentration variability (standard deviation) within - + 2- 2+ water samples. The highest observed variability corresponds to Cl followed by Na , SO 4 and Mg , which reflects the spatial variation of groundwater quality in Sidi El Hani basin. Therefore, the hydrochemical facies of groundwater in the study area vary broadly from Cl-Na to Cl-Na-SO4-Ca-Mg types (M’nassri et al., 2016).

3.2 Geochemical Processes of Groundwater Salinization The statistical analysis results based on ACP analysis highlight two major factors F1 and F2 responsible for the groundwater salinization of the study area. Factor F1 represents the most important factor, it accounts for about 42.6% of the total variance. The soluble salts associated with this F1, such 418 M’nassri Soumaia, El Amri Asma, Dridi Lotfi, Tagorti Mohamed, Hachicha Mohamed and Majdoub Rajouene

- + 2- as Cl (>80%), Na (>80%) and SO 4 (>60%) reveal that F1 can be considered as a possible path for natural salinization (Figure 4), because these elements in groundwater mainly come from the dissolution of evaporites such as halite and gypsum (Qin et al., 2013; Askri et al., 2016). However, Factor F2 accounts for about 15.9% of the total variance. Among this factor, Ca 2+ (80%) and K +(60%) are the dominant elements. Most studies argued that those elements are generated from the anthropogenic processes such as agricultural fertilizers leaching through water irrigation surplus (Jabal et al., 2014; Najib et al., 2017).

Figure 4: Distribution of soluble salts in two factors based on their level. F1 bound to water-rock interaction, F2 bound to anthropogenic activities

Moreover, the aquifer litology and anthropogenic activities contribution in groundwater salinization can be identified by referring to Cl+SO 4 vs Na+K and Ca+Mg vs SO4+HCO3 graphs (Figure 5). A linear relationship between Cl+SO 4 and Na+K with slope 1, is obtained for the majority of groundwater samples (Fig. 5a). This suggests that the dissolution of gypsiferous and halite minerals contributes to the salinization of the aquifer (Fadili et al., 2015). In contrast, samples suggest the dominance of Cl and SO 4 (Fig. 5a). According to Najib et al. (2017), this dominance could be attributed to the anthropogenic activities leaching from the topsoil under rain and irrigation water.

Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia) 419

Furthermore, the relationship between (Ca+Mg) and (HCO 3+SO 4) highlights that a part of samples are above the line 1:1 (Fig. 5b), suggesting the contribution of ion exchange process to the Ca+Mg enrichment with respect to HCO 3+SO 4 (Ledesma-Ruiz et al., 2015). However, a second part is aligned to straight line (1:1), confirming that those chemical elements are mainly derived from the dissolution of the gypsum (Najib et al., 2016).

Figure 5: Graphs of Cl+SO4 vs Na+K (a) and Ca+Mg vs HCO3+SO4 (b).

3.3 Physico-Chemical and Mineralogical Characteristics of Soil The textural soil classification shows that the texture of layers between (0-20 m) of collected soil samples varies from loamy sand to loam (Fig. 6). Thus, this soil is characterized by a high leaching and small cation exchange. As a consequence, the soils of the study area are less affected by salinity which can offer a higher tolerable level of irrigation with brakish water. However, the vadose zone allows the transfer of several minerals towards the aquifer, under rainfall and irrigation water conditions. However, the layers located at a 20 m of depth present a clayey texture which is associated to a higher percentage of exchange cations.

Figure 6: Textural classification of soil samples (0-30 m)

420 M’nassri Soumaia, El Amri Asma, Dridi Lotfi, Tagorti Mohamed, Hachicha Mohamed and Majdoub Rajouene

The chemical analyses applied on the soil samples reveal that the cations are classified as + 2+ 2+ + - 2- - follow: Na > Mg > Ca > K and anions as follows Cl > SO 4 > HCO 3 . Based on the profiles of - + 2- 2+ 2+ the EC measurements and the major elements (Cl , Na , SO 4 , Ca and Mg ), shown in Fig. 7, the soil samples located in the first layers (0-7 m) are characterized by the lowest concentrations in the case of all the solutes. The soluble salts concentration expressed by the EC varies from 7 dS/m, near the soil surface to 34 dS/m, at the depth of 23 m. In addition, all profiles present peaks of high concentrations located, mainly in the layers in the vicinity of the aquifer. This sudden increase is a result of the leaching process acting in salts that were accumulated on topsoil, under irrigation water and rainfall conditions.

Figure 7: CE and major elements profiles measured in soil samples

Indeed, the concentration diagram of Na + increases at the same rate as Cl - concentrations. This suggests that the concentrations of both ions are strongly influenced by the dissolution of halite (Eq. 3).

Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia) 421

2- 2+ However, SO 4 and Ca concentrations increase at lower layers located between 15 and 20 m, indicating respectively gypsum and calcite dissolution, corresponding to the chemical reactions as follows (Appelo and Postma, 1993; Risacher and Fritz, 2009): Halite NaCl () → Na () + Cl () (3) Gypsum CaSO 2 HO() → Ca () + SO () + 2 HO (4) Calcite CaHCO () → Ca () + 2HCO () (5) These observations are clearly confirmed by the Saturation Index (SI), presented in Fig. 8. The different depth profiles of Saturation Index (SI) of gypsum, halite and calcite as a function of dissolved concentration of chemical elements reveal that the most of soil solution are undersaturated with regards to Halite. Moreover, all soil solution samples are quite close to saturated or over saturated state of calcite and gypsum.

Figure 8: Saturation Index of different minerals as function of dissolved concentration of major elements.

Saturation Index (SI) -6 -4 -2 0 2 0

15 Depth (m) 20

30 Gyspum Calcite Halite 35

According to Visconti et al. (2010), calcite and gypsum are the two most abundant minerals in areas under semi-arid climate. This statement is in agreement with the XRD analysis where the quartz is the abundant mineral followed by calcite and gypsum. Therefore, the soil contains an amount of halite and dolomite. However, dominant clay mineral is illite, kaolinite and muscovite (Table 2). The successions of depletion and enrichment of chemical elements through their transfer from topsoil to groundwater are the results of precipitation/dissolution and soil leaching under rain and irrigation return flow processes that contribute widely to the salinization of the shallow aquifer of Sidi El Hani.

Table 2: Mineral soil compositions

Mineral Structural formula Volume fraction (%) Illite (K,H3O)(Al,Mg,Fe)2(Si,Al) 4O10 [(OH)2,(H2O)] 53 Kaolinite Al 2Si 2O5(OH) 4 32 Muscovite KAl 2(AlSi 3O10 )(OH, F )2 30 Quartz SiO 2 57 Dolomite Ca Mg (HCO 3)2 3 422 M’nassri Soumaia, El Amri Asma, Dridi Lotfi, Tagorti Mohamed, Hachicha Mohamed and Majdoub Rajouene

Mineral Structural formula Volume fraction (%) Calcite CaCO 3 14 Gypsum Ca SO 4.2H 2O 10 Anhydrite CaSO 4 3 Halite NaCl 4

3.4 Assessment of the Salinization Trends of the Soil To evaluate the soluble salts salinization level in the irrigation that originated from the groundwater in Sidi El Hani basin, the total concentration of water and soil samples were assessed using the Wilcox diagram (Figures 9a and 9b). The diagram indicates that 35 wells present a medium risk of sodicity. However, 14 wells that are mainly located near sebkha Sidi El Hani, reveal a high risk of sodicity. In addition, all the samples show a high risk of salinization (C4 and C5). In fact, the use of brackish water irrigation can present a serious problem for both soil and crop yield (Sparks, 2003). This observation can be confirmed by the Wilcox diagram for the soil samples (Fig. 89b). It reveals that soil samples are classified from medium to high and from high to very high regarding the sodicity and salinity hazard, respectively. Moreover, many soil samples with EC exceeding 10 4 µS/cm are plotted outside Wilcox diagram. This is a direct consequence of the decreasing crop yields in the study area.

Figure 9: Wilcox diagram for salinity and sodium hazard for groundwater (a) and soil samples (b)

The concentration factor diagram applied for the soil samples reveal that Na concentrations increase at the same rate as chlorides except for the most dilute solutions. Therefore this element is 2+ 2- involving for the exchange cations. Inversely, Ca and SO 4 concentrations increase at a lower rate of the chloride suggesting the precipitation of the calcite and gypsum. However, the alkalinity is stable and even tends to decrease confirming to the hypothesis of calcite precipitation (Figure 10). This statement is consistent with the RAcalcite and gypsum calculated for the soil samples, which is negative. Hence, soil solution is following a neutral saline trend and does not present a risk of alkalinization. It also conforms to the mineralogical analyzes of different soil samples taken.

Salinization Risk Assessment of Soil and Groundwater: A Case Study in Sidi El Hani Basin (Central-Eastern Tunisia) 423

Figure 10: Concentrations diagram of chemical elements

3.0 Cl Na Ca Mg SO4 HCO3 K 2.5

2.0

1.5

1.0

Log (molality) Log 0.5

0.0

-0.5

-1.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Log (FC)

4. Conclusion To evaluate the salinization risk of soil and aquifer of Sidi El Hani (center-eastern Tunisia), the - + 2- 2+ concentration of chemical elements were measured. The results show a high Cl , Na , SO 4 and Mg concentrations. The statistical and hydrochemical tools revealed that the increase in element concentrations is primarily due to the water-rock interactions as well as anthropogenic activities such the excessive use of fertilizers and pesticides. Therefore, the use of this groundwater in irrigation presents a serious problem for soil and crops yields. According to results plotted on the Wilcox diagram, the soil is characterized by a medium to high risk of sodicity and high to very high risk of salinity. The light textured characteristic of the studied soil allows for an important leaching of soluble salts, that were accumulated on topsoil, under irrigation water and rainfall conditions. Thus, through this transfer, the solution gets to concentrate. Two minerals precipitate according the sequence calcite > gypsum. The RA analyses show that the solutions follow a neutral saline pathway. Consequently, despite the considerably high natural concentration of certain chemical elements in some cases, the soils are not considered to have a negative effect to the agricultural sector. However, the salts-leaching form potential stocks of contaminant, may threaten the long-term groundwater quality. Therefore, more thorough database knowledge is required to better assess the groundwater quality.

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