Fractionation of Uranium forms as affected by spiked soil treatment and soil type

To evaluate the effect of different soil factors on uranium distribution fraction in soil, a U-fractionation experiment was conducted. Different Uranium forms were compared in two soil types (clayey soil from Mostourd area and sandy soil collected from El-Gabal Al-Asfar area). Also, the variation of Uranium forms due to soil treatment (spiking) were studied. In case of Mostorud clayey soil the initial Uraniumfractions were 45.63 % as residual form, 20.69 % organically bound 16.36 % Manganese iron oxides and iron oxides bound, 9.76% Carbonate form, 7.41 % exchangeable fractions and 0.15% water soluble fractions. These fractions varied significantly when the soil was spiked with 200 mg Uranium / Kg soil to 46.88 %, 23.19 %, 9.97 %, 16.07 %, 3.79% and 0.10% for residual, organically, Manganese iron oxide, carbonate, exchangeable and water soluble fractions respectively. These result showed significant reduction in Uranium-ex fraction forms and Manganese - iron bound forms with significant increase in Uranium-carbonate form due to Uranium application. In case of the untreated sandy soil, the main Uranium-fractions were 57.42% as residual form (relatively higher residual – Uranium form in the clayey soil) 16.10 % organically bound, 13.78% Manganese and iron oxides bound, 7.22 % Carbonate form, 5.23 % exchangeable fractions and 0.25 % water soluble fractions The application of 200 mg Uranium/Kg soil resulted in a significant changes in Uranium-Fractions distribution as follows : 59.26 % , 11.27 % , 19.59 % , 6.84 % , 2.90 % and 0.14 % for residual , organic , Manganese –iron oxides , carbonate, exchangeable and water soluble fractions , respectively. It could be concluded that the solubility of soil uranium depends upon the soil’s physicochemical, mineralogical and micromorphological properties; the nature of the uranium association; and the mineralogical, morphological, and compositional characteristics of the uranium-bearing phases.