Physical-chemical characterization of uranium containing sediments

Abstract

The presented paper is intended to study the chemical behaviour of combined geogenicanthropogenic uranium content in specific stream sediments. The sampling points have been chosen with respect to the natural conditions in the locality of groundwater outflow from a former uranium mine adit in Považský Inovec mountain range, near Kálnica village. Besides the total uranium determination and physical-chemical characterization of the relevant water- and sediment samples we carried out modified Tessier type sequential fractionation extractions of natural- and artificially contaminated sediment samples after time dependent agitation in air and in the atmosphere of argon. The obtained results have been compared with those fulfilled with montmorillonite K-10. The total uranium concentrations of the relevant groundwater samples as well as of stream sediments have been determined by ICP-MS using HP 4500. The determinations of uranium in extracts have been accomplished according STN757614, utilizing arsenazo III as a selective complex forming reagent for spectrophotometric determination of uranyl-ions at 650 nm. The total uranium concentration of the groundwater outflow and in the sediment taken in its immediate vicinity has been 31.75±0.35 μg dm-3 and 38.0±2.7 μg g-1 respectively. Unlike montmorillonit K-10, in which the carbonate-bound fraction of uranium after 1 week aeration and agitation in argon atmosphere represents 22.8% and 18.6% respectively, uranium in investigated sediments has been present predominantly in carbonate-bound fraction-reaching under similar conditions 38.6% and 26.6%, respectively.

Assessment of 226Ra and U colloidal transport in a mining environment

“…Uranium is particularly mobile under oxidizing conditions, where it occurs as the hexavalent UO2 2+ uranyl species, and also in the presence of inorganic complexing agents such as sulfates or carbonates which increase its aqueous mobility (Závodsḱa et al, 2008;Langmuir and Riese, 1985). However, as a trace element, uranium mobility can be affected by sorption reactions on the surface of minerals.…”