Groundwater chemistry and radon-222 distribution in Jerba Island, Tunisia

The highest values were registered in the western coastal wells and near the fault of Guellala. However, the central and eastern wells showed low radon levels. Compared to 222Rn activity in some countries with the same lithology, radon concentrations in the Jerba unconfined aquifer have higher values influenced by the structure of the aquifer and by seawater inflow enriched with 222Rn resulting from the decay of uranium derived from phosphogypsum deposits in the gulf of Gabes. The EC and 222Rn spatial variability in the study area were mapped using ARC Map 10.3 software. Hydrochemical results in addition to geological data and radon activities confirm the existence of vertical communication between the Miocene aquifer and the unconfined Plio-Quaternary aquifer through fault system and a lateral communication with the sea via seawater intrusion.