Groundwater salinization and seawater intrusion tracing based on Lithium concentration in the shallow aquifer of Jerba Island, southeastern Tunisia

The objective of this study was to identify groundwater salinization origins and develop a new geochemical approach based on Lithium and major element concentrations to understand the processes associated to seawater intrusion into the shallow aquifer of Jerba Island, Southeast of Tunisia. An integrated application of geochemical modeling and statistical approaches (Principal Component Analysis and Hierarchical Cluster Analysis)based on a major and trace ions from the Jerba unconfined aquifer was used. The hydrochemistry and the statistical investigations revealed that the groundwater geochemical behavior is controlled by seawater intrusion, rock-water interaction and anthropogenic impact. Seawater intrusion is the mechanism controlling groundwater abnormal salinization and the interaction between groundwater and aquifer materials. In areas where seawater intrudes a fresh coastal aquifer, cation exchange reactions influence groundwater chemistry and Li+ ions released into the solution resulting in a Li+ concentration increase. This result proves that seawater intrusion activates Li+ leaching to groundwater. Taken together, these results suggest Li+ as a groundwater salinization tracer.