Flood hazard assessment and heavy metal distributions around Um Gheig mine area, Eastern Desert, Egypt

Abstract

This study focuses on wadi Um Gheig and its associated Pb-Zn mine to quantify the possible dispersion pathways of heavy metals to the surrounding environment. The morphometric drainage system parameters were specified by ArcGIS 9.3. A total of 21 samples were collected and analyzed using XRF, XRD, ICP-OES and SEM. Different enrichment indices were applied to specify the degree and source of contaminations in the area upon transport mainly by flooding events. The wadi Um Gheig basin is characterized by dendritic to sub-dendritic drainage pattern with a moderate degree of hazardousness. Five groups of metal sources were identified by chemical and mineralogical patterns. Group I reflects the anthropogenic impact from the mine site by Pb, Zn, Cd, Ba, Sr, Mo, Sn, W, U, As, S, Cl, part of Mn and Fe, as well as from host rock minerals namely gypsum/anhydrite, calcite and dolomite. Group II covers the lithological background of the drainage system with schists, source of Cu, Co, Ni and Cr, part of Ti, and Fe, and granitoids represented by REE, Y, Nb, and Ta, and finally quartz from sands and sandstone acting as a dilutant. Group III comprises moderate to strong enrichment of heavy minerals from Group I and II. Moderate groundwater recharge promotes metal dissolution from the mine and continuous evaporation causes a slight enrichment due to capillary transport downstream (Group IV). Finally the sea water influence (Group V) enhances dilution of heavy metal carriers and enrichment due to efflorescence. The contamination factor, enrichment factor and the geoaccumulation index show a very strong contamination degree close to the mine site by Cd, Pb and Zn. Without suitable mine site rehabilitation strategies the Pb-Zn wastes along the Red Sea coast will suffer severe erosion, transport and contribute to the contamination of the sea environment.