Assessment of groundwater hydrogeochemical characteristics and salinization intrusion in coastal arid area (South Gabes, South-East Tunisia)

Abstract

In the southern region of Gabes, groundwater is experiencing a quality deterioration in relation to the increase in demand to meet the various sectors of economic and agricultural activities. Indeed, the degradation of quality generally results in high concentrations of total dissolved solids, ranging from 2.44 to 13.68 g/L, and waters contamination by nitrates. The determination of the groundwater salinity origin from Gabes, largely influenced by tectonics, was approached from the study of the evolution in the space of major chemical elements and by statistical treatment. Based on these methods, this work aims to demonstrate that the high waters’ salinity in this aquifer is explained by an interaction between its waters and the evaporitic levels of the aquifer formation, by the marine intrusion around the El Hajel Wadi, and by the return of irrigation water to the Mareth-Arram region. The hypothesis of marine intrusion is justified by the high chloride content due to the presence of reverse reactions of cation exchange. Geochemical interactions (reverse basic exchanges and precipitation/dissolution phenomena of minerals from the aquifer formation) show that these waters have poor to bad quality.