Disequilibrium between uranium and its progeny in the Lake Issyk-Kul system (Kyrgyzstan) under a combined effect of natural and manmade processes

The upper section of near-shore deposits was disturbed by currents, with 137Cs and 210Pbatm more or less uniformly distributed in this layer. Peaks of 226Ra and 210Pb occur at different depths from 5 to 20 cm below the sediment surface, with 238U/226Ra ratios 0.28-0.44. The presence of mullite in these sediments indicated that radioactive ash penetrated into the lake in the past. At present, 226Ra in the ash is buried under a non-radioactive cap.