Geziret El Nabatat Soil Geochemistry and Mineralogy: Geochemical Background Values Determination and Spatial Distribution Of Potentially Toxic Elements and Rare Earth Elements

Geziret El Nabatat (Aswan Botanic Garden) is one of the oldest gardens worldwide and one of the natural protectorates in Egypt. It has a vital scientific importance for documentation of knowledge about its plant species. The plants are affected by the mineralogy and geochemistry of soil. So, this work aims to through light on the mineralogical and geochemical composition of Geziret El Nabatat soil, for the first time. Mineralogically, the soils of Geziret El Nabatat consist of quartz, montmorillonite, kaolinite and calcian-albite, which nearly follow up the composition of the Nile Valley soil. The prevailing oxides in this soil are SiO2, Al2O3, Fe2O3 and CaO with mean concentration 49.04%, 13.62%, 13.02% and 5.57%, respectively. The mean concentration of potentially toxic elements (PTEs); Pb, Co, Cr, Cu, Ni and Zn was 13.64, 17.33, 42.89, 33.68, 49.65 and 63.48 mg/kg, respectively. The mean concentration of rare earth elements (REEs); La, Ce, Nd, Sm, Pr, Y and Sc was 15.7, 63.01, 16.28, 1.76, 8.83, 20.48 and 1.6 mg/kg, respectively. The calculated index of geoaccumulation and ecological risk factor of the recorded PTEs and REEs indicated the uncontamination of soil with these elements, with no ecological risk. The calculated enrichment factor of these elements indicated their natural geochemical background. Consequently, this result supports the possibility of using the mean concentration of the recorded REEs and PTEs in this soil as background value for the distribution of these elements in the Egyptian Nile floodplain soil.