Uranium speciation and spatial distribution in the bottom sediments along the Uzynbulak creek at the Semipalatinsk test site

Uranium concentrations in the water and bottom sediments along the Uzynbulak creek at the Semipalatinsk Test Site are high, possibly implying anthropogenic contamination. These concentrations were measured by ICP-MS and the environmental mobility of uranium was determined by sequential extraction. Activity concentration in bottom sediments ranged from 20 to 6000 Bq/kg with a median of 156 Bq/kg, while that of water did not exceed 0.4 Bq/l. Uranium accumulated in sedimentary environments, up to 73% of which was bound to Fe and Mn oxides and hydroxides, while isotopic compositions indicated natural uranium. Anthropogenic uranium was not observed in the samples. (author)