Geochemical and statistical studies of Mio-Pliocene aquifer's mineralization in Jerba Island, South-eastern Tunisia

Abstract

Management of water resources is a major concern for arid and semi-arid regions mainly because of the high groundwater salinization which impacts water quality. Here, Hydrochemical data of major and minor ions such as (sodium (Na+), Calcium (Ca2+), Magnesium (Mg2+), potassium (K+), chloride (Cl−), bicarbonate (HCO3−) and sulfate (SO42−) were used to study the Mio-Pliocene (MP) aquifer of Jerba Island, southeastern Tunisia, whose groundwater resources are characterized by a high mineralization. Bromide (Br−), iron (Fe) and Hydrogen sulfide (H2S) measurements as well as statistical data were used to identify the main processes involved in the mineralization of this aquifer. The major hydrochemical facies in Jerba confined aquifer is NaClSO4. Multivariate statistics analysis was used to visualize similarities between variables, investigate the origin of anomaly in groundwater mineralization and determine the hypotheses that would be developed in the geochemical study. Rock-water interaction and dissolution/precipitation of halite, feldspar, gypsum and carbonate are responsible for the chemical constituents of groundwater. The iron concentrations were between 0 and 1.6 mg/l. These concentration values may be due to the leaching of a sand-salty sandstones unit, rich in red clay, where the deep aquifer is housed. The H2S map shows that the highest concentration of this gas is in the central part of the Island which may be due to the presence of faults systems and a petroleum well (Robbana).