Physiochemical processes affecting the geochemistry of carbonate aquifer of southeastern Al-Ain Area, United Arab Emirates (UAE)

Detailed hydrogeochemical analyses were carried out in order to delineate the physiochemical processes and paleohydrogeological regime of groundwater flow of southeastern Al-Ain area and its surrounding desert fringes. Groundwater composition and salinization could be a result of integrated cycles of successive physiochemical processes of mixing of seawater, salt dissolution, and flushing by recharge water from the infiltration of rainfall in the interdune areas and gravel plains and also from Jabal Hafit lying to the southeast, and sewage effluent water from the residence areas to the northwest. In addition to that, ion exchange upon flushing, salt sieving from deep aquifers, and evaporation and accumulation along the wetland zones are factors affecting the groundwater of the area. Human and anthropogenic activities might have negative impact on the quality of groundwater in the region. Both Zn and Fe are the most detectable heavy metals in the analyzed samples, and they reach as maximum as 2,277 μg/l and 2,902.6 μg/l for Zn and Fe, respectively, along the north western localities. The source of these metals is most probably due to contamination threats by the sewage effluent or industrial wastes in these localities. Reducing environment releases the toxic and heavy metals in soluble compounds in case of high organic matters. A strong relationship appears between Fe and Zn ion concentrations in groundwater and the type of well construction materials (casings and screens). Also, a positive correlation is observed between the concentrations of Zn in water wells and in plants surrounding the wells. The increase of chromium concentrations is observed in the north of the study area, and this increase might be ascribed to the weathering of olivine and pyroxence of Oman Mountain in the northeast and might be possibly due to using the manure or animal wastes for agriculture activities.