Hydro-Geochemical Applications and Multivariate Analysis to Assess the Water-Rock Interaction in Arid Environments

Thirty groundwater samples were taken from Assiut's northern outskirts. The physicochemical properties of these samples were investigated. For the evaluation of water-rock interaction, the saturation index (SI), chloro-alkaline indices (CAI1 and CAI2), Gibbs ratios for cations and anions (GC and GA), principal component analysis (PCA), and hierarchical cluster analysis (HCA) were used. (1) With the exception of five samples that were supersaturated, the rest of the groundwater samples were under-saturated with carbonate mineral dissolution (calcite, dolomite, and aragonite) and evaporite mineral dissolution (anhydrite, gypsum, halite, and sylvite). (2) The presence of ion exchange between alkali elements (Na+ + K+) and earth alkaline elements (Ca2+ + Mg2+) is explained by the positive values of the chloro-alkaline indices. (3) In four groundwater samples, negative chloro-alkaline indices suggest reverse ion exchange and an increasing alkali element content. (4) The Gibbs diagram demonstrates that, with the exception of four samples that reflect saline groundwater, the majority of the groundwater samples are freshwater recharging from the fresh surface water in the research area. (5) Groundwater types include Ca-HCO3 (11%), Mg-HCO3 (48%), Na-HCO3 (23%), Mg-Cl (13%), and Na-Cl (3%). (6) The alkali, earth alkaline elements, and sulphate are the key controls on groundwater salinity, according to PCA and HCA. (7) The somewhat saline groundwater in the research area's western desert margins should not be used since it poses a health danger to people.

Automated summary

This study investigated the physicochemical properties of groundwater samples taken from the northern outskirts of Assiut. The results showed that most of the groundwater samples were under-saturated with carbonate and evaporite mineral dissolution. Ion exchange between alkali and earth alkaline elements was observed. The groundwater types were mainly Ca-HCO3 and Mg-HCO3, and the key factors influencing groundwater salinity were alkali, earth alkaline elements, and sulphate. It was also found that the slightly saline groundwater in the western desert margins posed a health risk.