Hydrogeochemical characterization and suitability of groundwater for drinking and irrigation in Menzel Bourguiba aquifers (Northeastern Tunisia).

Abstract

The aquifer system of Menzel Bourguiba, located in northeastern Tunisia, is an important groundwater resource that, for the last decades, has been a subject of excessive use by agricultural and industrial activities leading to the degradation of its water quality. To better understand the hydrochemistry of these aquifers, identify the main factors controlling their mineralization, and assess their suitability for drinking and agricultural purposes, 35 groundwater samples collected during the campaign of October 2019 were analyzed by different physicochemical methods. The results showed that the hydrochemical facies of the study area is characterized by two major types SO4-Cl-Ca and Na-Cl. The total dissolved solids (TDS) values range from 0.5 to 1.9g/L in the shallow aquifer and from 0.6 to 2g/L in the deep aquifer. The high rates are recognized downstream of the studied basin. The interpretation of multivariate statistical analysis and geochemical approaches revealed that rock-water interaction, dissolution and precipitation process, ionic exchange mechanisms, water irrigation return, and marine intrusion are the main factors controlling the mineralization of the study area groundwater. The comparison of the analytical data to the Tunisian and World Health Organization (WHO) standards unveiled that the majority of groundwater samples are unsuitable for drinking because of high nitrate contents, elevated electrical conductivity (EC), TDS values, and high concentrations of some chemical parameters. In addition, the sodium absorption ratio and the sodium percent parameters indicated that most of the analyzed samples are inappropriate for irrigation uses.