Mobility and Risk Assessment of Uranium and Associated Heavy Metals in Uranium Mill Tailings

摘要

To explore the geochemical dispersion of uranium and its associated toxic metals in uranium mill tailings, samples were collected from a uranium mill tailing pond in northwest China and characterized by X-ray diffraction, X-ray fluorescence and inductively coupled plasma mass spectrometry. Sequential extraction was applied to study the chemical form of uranium and its associated toxic metals in uranium mill tailings. Results showed that the geochemical distribution of the U, Sr, Pb, and Mn were mainly present in the inert residue fraction. Among the non-residue fraction, U preferentially occurred in Fe/Mn oxide fraction. Sr was primarily associated with water-soluble and exchangeable fraction. Pb was principally related to Fe/Mn oxide fraction. Mn was mostly in water-soluble, exchangeable and Fe/Mn oxide fraction. The radar chart of ecological risk assessment indicated the potential mobility decreased in the order Mn > Sr > U > Pb, and the biggest ecological risk metal was U. This study suggested that more attention should be paid to the management of uranium mill tailings.