Hydrogeochemical characteristics of groundwater in the Mediterranean region: A meta-analysis

The Mediterranean region is a water-stressed environment where groundwater, as main water source, is under a lot of anthropogenic pressure. This study aims to evaluate the baseline hydrogeochemical characteristics and water quality of groundwater in the region. For this purpose, 123 hydrogeochemical studies conducted in the area were examined. Information concerning the studies and concentrations of major, minor ions and isotopes were extracted. The data was divided into 3 major aquifers types: Quaternary, Jurassic and Cretaceous, and Tertiary. The data was analyzed qualitatively to identify the major topics of research and quantitatively using classical hydrogeochemical methods and multivariate analysis. The results show a disparity in the distribution of study topics across the region with minor ions and isotopes studies mostly concentrated in Europe. Moreover, the dominant hydro-chemical facies are Ca-Cl and Na-Cl in the Quaternary, Ca-HCO3 and mixed in the Jurassic and Cretaceous and Ca-HCO3 dominate the Tertiary aquifers. Furthermore, the major water forming process is the evaporation in the Quaternary and Tertiary aquifers, and rock-water interaction in the Jurassic and Cretaceous aquifers. Finally, nitrate pollution is found in 29% of aquifers while 15.3% of aquifers with minor ions data show high concentrations of at least one minor ion. The majority of aquifers with pollution problems are Quaternary. Indeed, these aquifers are highly affected by anthropogenic impact and seawater intrusion. Finally, this work is a preliminary assessment of groundwater characteristics in the region. Further works are needed to investigate specific aspects of Mediterranean region aquifers' groundwater hydrogeochemistry.