**4.2. Water type**

**3. Sampling and analytical methods**

96 Aquifers - Matrix and Fluids

tion to the methyl orange endpoint.

**4.1. In situ measurements interpretation**

**Table 1.** In situ measurement and geochemical data of groundwater samples.

**4. Results and discussion**

respectively.

A total of 22 boreholes were sampled for chemical analysis, 15 samples collected from the BouHafna aquifer and 7 samples from the Haffouz aquifer. The physicochemical parameters such as Temperature (T°C), pH, and electrical conductivity (EC) were measured directly in situ using portable meters. Groundwater samples were analyzed for major ions in the laboratory of Radio-Analyses and Environment of the school of engineers of Sfax, Tunisia. Major cation concentrations were determined by Waters Ion chromatograph using IC-PakTM CM = D columns. Major anion concentrations were measured using a Metrohm ion chromatograph equipped with CI SUPER-SEP columns. The analysis of bicarbonate was undertaken by titra-

The physicochemical parameters and overall hydrochemical data of Haffouz and BouHafna groundwater samples are presented in **Table 1**. Groundwater temperature values are relatively homogenous and vary from 19.9 to 25.3°C. The pH measurements range between 7.39 and 7.73 for Haffouz aquifer and between 7.01 and 7.74 for BouHafna aquifer. This may indicate a neutral to slightly alkaline pH but suitable for drinking and agricultural purposes. Electrical conductivity (EC) values, which vary in a wide range between 422 and 1623 μS/cm, are probably related to the signification variation of the TDS values that range from 203 to 1188 mg/l, The data plotted in the Piper diagram [14] show that Haffouz and BouHafna groundwater samples have the same Ca-Mg-HCO<sup>3</sup> water-type, except for some samples collected from BouHafna aquifer, which are distinguished by Ca-Mg-SO<sup>4</sup> water-type (**Figure 5**).
