Geochemical and isotopic study of paleogroundwater salinization in southeastern Tunisia (Sfax basin)

Salinization is a common environmental problem of groundwater contamination, particularly in developed coastal aquifers. The Sfax basin is located on the Mediterranean coast, southeastern Tunisia, and is dominated by industrial activities. The problem of groundwater mineralization in the south part of this aquifer has long been attributed to the marine influence. In this study, a combined hydrogeological and isotopic survey using chemical tracers was conducted in addition to discharge and groundwater level measurements. The results preclude seawater intrusion as an origin of groundwater mineralization. It seems that the main source of groundwater mineralization is due to the mixture with salty water lodged in the C/T (Cenomanian-Turonian) aquifer. This mixture process is carried out by the simultaneous effect of (1) a lateral flow of saline water coming from C/T aquifer in the southwest (Menzel Habib) and (2) a local vertical leakage from the same C/T formation which forms the basement of the studied aquifer. The depleted isotope signature of the majority of groundwater is characteristic of old recharge occurring during the late Pleistocene-Holocene, with the exception of some local recent refill areas. (C) 2011 Elsevier Ltd and INQUA. All rights reserved.