Natural radioactivity and groundwater quality assessment in the northern area of the Western Desert of Egypt

The chemical composition and natural radioactivity of the northern area of the western desert groundwater were determined to evaluate hydrogeochemical facies and assess groundwater quality for different uses. Many the groundwater samples belong to the Na⁺- Cl⁻, Na₂SO₄⁻ type, followed by Ca²⁺- Mg²⁺- Cl⁻ type. Only a few samples are of the Na⁺- HCO₃⁻ type. The spatial distributions of the major ions describe similar anomalies, with the highest concentrations found at the extreme northeastern margin of the oasis, as well as in its northern and northwestern parts. Fe is the most abundant toxic metal, followed by Cu and Mn. Anomalies of Cr, Ni and Zn are also detected. Rock/water interactions strongly affect the chemical composition of the groundwater. Dissolution and cation exchange are the main processes controlling the hydrogeochemistry. Most of the irrigation groundwater problems in the study area may be resolved using an effective drainage system. The estimated total annual dose due to ingestion of ²³⁸U, ²³²Th and ⁴⁰K in groundwater samples reveals that the groundwater is safe for human consumption. However, the toxic metal content of the Bahariya groundwater exceeds the permissible levels for both irrigation and consumption, and the water must be filtered through suitable membranes to exclude these toxic metals. Regular monitoring of the quality of this water for drinking is strictly required.