Evaluation of groundwater salinization and pollution level on Favignana Island, Italy

Fifty-six groundwater samples were taken from the island of Favignana to evaluate the interaction between the groundwater and seawater, as well as the deterioration factors for the aquifers, using the combined hydrogeochemical and multivariate statistical approaches. Results show that the order of the groundwater chemistry in the study area was Na⁺> Ca²⁺>Mg²⁺>K⁺ and Cl^->HCO₃^->SO₄^2->NO₃^-. The groundwater samples were in the moderate saline zone to highly saline zone and indicate that the groundwater of the island of Favignana was recharged with seawater. The spatial distribution maps of Cl^- and NO₃^- show that most of the groundwater samples had high concentrations of Cl^- and NO₃^- in the study area. The ionic ratio diagrams, such as Na⁺/Cl^- versus Cl^-, Mg²⁺/Ca²⁺ versus Cl^- and Ca²⁺/HCO₃^- versus Cl^-, and other hydrogeochemical plots reveal that the groundwater chemistry of the study was primarily controlled by the seawater intrusion and reverse ion exchange process, with a small contribution from carbonate dissolution. Additionally, the NO₃^-/Cl^- versus Cl^- diagram and principal component analysis (PCA) show that the contamination of nitrate in the study area was due to human activities (i.e. agriculture and domestic sewage disposal). The outcome of the present research could be helpful for groundwater resource management in coastal environments.