Hydrochemistry of Umm Er Radhuma Groundwater

Umm Er Radhuma Aquifer (UER) is the most important groundwater aquifer in Saudi Arabia, extending over 1.6 M·km2 eastern part of Arabian Peninsula, forming main throughout Rub’ Al-Khali (RAK). Groundwater salinity increased from west to east, reaching more than 27,000 mg/L near border with United Arab Emirates, where a Na+-Ca2+Clˉ- water type dominated. Gibbs diagrams indicated that dissolution/precipitation carbonates and evaporation/precipitation minerals, especially anhydrite, gypsum, halite account for solutes groundwater. Most samples plot above 1:1 line (Ca2+ + Mg2+) against , indicating other sources Ca2+ Mg2+ along dolomite calcium carbonate minerals. Phreeqc model clay minerals are kaolinite gibbsite which had major effect on cation exchange process as by Chloro-Alkaline index (CAI), values greater zero occurrence reverse ion between its host aquifer. The Na+-Ca2+Clˉ-dominated anaerobic conditions prevailed reduction sulphate took place.