Hydrogeochemical characteristics and evolution of ground water at the Ras Sudr-Abu Zenima area, Southwest Sinai, Egypt

الملخص EN

The hydrogeochemical and isotopic data of groundwaters of the different aquifers of the Ras Sudr-Abu Zenima area, southwest Sinai, Egypt were examined to determine the main factors controlling the groundwater chemistry and salinity as well as its hydrogeochemical evolution.

Groundwater occurs in different water bearing formations belonging to Quaternary, Neogene, Upper Cretaceous, and Paleozoic.

Different geochemical interpretation methods were used to identify the geochemical characteristics.

Groundwater of the coastal Quaternary alluvial aquifer has the highest salinity values (2739-7040 mg / l) in the study area due to the impact of seawater and agricultural activities.

Piper diagram showed that Cl and SO4 are the dominant anions, whereas Na is the most dominant cation, where it is sometimes replaced by Ca and / or Mg in the hydrochemical facies of the groundwaters.

Durov diagram plot revealed that the groundwater has been evolved from Ca-HCO3 recharge water through mixing with the pre-existing groundwater to give mixed water of Mg- SO4 and Mg-Cl types that eventually reached a final stage of evolution represented by a Na-Cl water type.

Different ionic ratios revealed the impact of seawater and marine aerosols on the hydrochemical composition of groundwater of the Quaternary aquifer.

Dissolution of carbonate and sulfate minerals in the aquifer matrices and recharge areas as well as cation exchange are shown to modify the concentration of ions in groundwater.

Groundwater-mineral equilibria showed the prevailing dissolution-precipitation reactions in the groundwater.

The groundwaters are depleted in 2H and 18O and displayed an isotopic signature close to that of meteoric water with dexcess values indicating present-day precipitation over the region and reflect the contribution of vapour masses from Mediterranean origin.

The isotopic features suggest that most of the groundwaters at the study area result from mixing between recent recharge and an older component recharged under climatic conditions cooler than at present.

Moreover, groundwaters from the Cambrian and Carboniferous waterbearing formations show d-excess values of 13.9 and 10.96‰, respectively, which indicates that older component of recharge is prevailing than the recent one.

Isotopic signature of groundwater from the Quaternary aquifer indicated seawater contribution.