Concentrations of thorium and uranium in freshwater samples collected in the former USSR

Approximately 100 freshwater samples were collected in Ukraine, Russia, and Belorussia with regard to the Chernobyl accident. Thorium and uranium were determined by both quantitative and semiquantitative analysis modes of inductively coupled plasma mass spectrometry (ICP-MS). Thorium-232 was detected in only a few samples. Uranium concentrations ranged from non-detectable to 1,000ng/ml. Mean and median concentrations of238U were found to be 30.7±139 and 0.7 ng/ml, respectively. The isotope ratio of234U/238U ranged from 4.6·10−5 to 4.4·10−4. Mean ratio of235U/238U was 0.00721±0.00006 (n=27).