Uranium series radionuclides in surface waters from the Shu river (Kazakhstan)

Abstract

The concentrations of (238)U, (234)U, (226)Ra, (210)Po and (210)Pb have been determined in surface waters collected along the course of the Shu River, lying on the border between Kazakhstan and Kyrgyzstan. In the study area, the river runs through some of the largest uranium deposits worldwide, which were actively exploited during the nuclear weapons and nuclear energy programmes of the former Soviet Union. The data show an increasing trend in uranium concentrations downstream the river from the city of Tokmak to the city of Shu, with good correlation between total uranium concentrations and total dissolved solids. Data on uranium isotopes disequilibrium show the presence of technogenic uranium inputs into the Shu River downstream from the city of Karasu, evidenced by a decrease in the measured (234)U/(238)U isotopic ratio from 1.63 in uncontaminated sites to 1.29 in sites affected by past mining activities.

Uranium isotopes as tracers of groundwater evolution in the Complexe Terminal aquifer of southern Tunisia

“…Our data from the Senonian limestone aquifer are thus interesting in two main aspects: first they confirm the isotopic disequilibrium of uranium dissolved from calcareous formations, showing that α-recoil processes are also significant in such facies even though water-rock interaction mainly occurs as congruent dissolution. Second, we do not observe the decreasing trend of 234 U/ 238 U with increasing uranium content which was described in several studies (Kronfeld and Adams, 1974;Osmond and Coward, 1976;Burkitbayev et al, 2012). This inverse trend is generally interpreted as reflecting progressive dampening of the 234 U fractionation due to alpha recoil by the increase in uranium at secular equilibrium released as weathering increases.…”

Species of uranium of the Kamyshanovskoe deposit (Kyrgyzstan)

“…In all filtrates natural uranium isotopes were measured by a high resolution alpha-spectrometer ("Alpha-analyst", Canberra) after appropriate radiochemical preparation, consisting of co-precipitation of radionuclides with iron hydroxide, extraction by 30% tributyl phosphate (TBP) in toluene and electrodeposition on a steel disk with a mixture of 25% solution of NH 4 Cl and saturated solution of (NH 4 ) 2 C 2 O 4 as electrolyte solution [8].…”