Isotopic behavior and self-organizing maps for identifying groundwater salinization processes in Jerba Island, Tunisia

Abstract

The purpose of this study is to assess the groundwater evolution in Jerba Island. This paper also focuses on the relationship between mineralization and anthropogenic activities and the identification of processes controlling groundwater geochemistry. An approach combining the use of water dissolved chemical species, isotopic fingerprint, and the self-organizing maps has been used to understand the behavior of a unconfined aquifer system and to determine the origin of its different contamination sources. In the present work, a geochemical characterization of the coastal aquifer from the unconfined Jerba aquifer, Southeast Tunisia, was carried out, using hydrogeochemical and isotopic (2H and 18O) data, correlation matrix, and self-organizing maps. For this aim, 79 wells were sampled and analyzed. Geochemical modeling and isotopic data demonstrated that seawater intrusion, exchange reactions occurring within the aquifer matrix, and anthropogenic activities were the major processes controlling the groundwater contamination in the island. The isotopic tracers indicate that the increasing salinity in the shallow coastal aquifer is caused by seawater intrusion. The methodology appears as a valid tool applicable in other coastal areas to determine the main factors governing the groundwater mineralization.