Effects of ageing on the occurrence form of uranium in vertical soil layers near an uranium tailing reservoir

Abstract

Uranium contamination due to mining and metallurgical operations is a serious problem worldwide. Upon entering an ecosystem, uranium poses a high potential threat to humans and other organisms. A better understanding of the distribution and speciation of uranium in contaminated soil is therefore necessary over relevant time scales. In this study, we collected uncontaminated soil samples, including eluvial (E), illuvial (B), and parent-material (C) horizons, from a soil profile near a uranium tailing reservoir in southern China. Four columns were filled with the E, B, and C horizons and three types of mixed soil samples to simulate the behavior of uranium in soil near an uranium tailing reservoir. The atomic-scale mechanisms were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, and other characterization methods. The results show that air, clay minerals, iron and manganese oxides, and other soil properties exert important effects on the forms and mobility of uranium in soil, and that ageing leads to a rearrangement and chemical fractionation of uranium in soil.