Cesium-137 of Chernobyl Origin in Lake-River Systems of Eastern Fennoscandia: 30 Years after the Accident

摘要

Contamination of waters of lake-river systems after many-year migration of ~(137)Cs in water bodies was studied. In lakes with the ~(137)Cs fallout density lower than 8 kBq m~(-2), the radionuclide concentrations in water after 24-29 years did not exceed 2-3 Bq m~(-3), and at a fallout level of 37 kBq m~(-2) it was in the range 11-34 Bq m~(-3). The natural half-clearance time T of lake waters from ~(137)Cs was 6-7 years at the exposure of up to 20 years. The ~(137)Cs migration in the lake-river systems that occurred during ～30 years did not lead to structural changes in the water contamination: The initially low ~(137)Cs level in lake waters did not become high, and vice versa. Among rivers feeding Lake Ladoga, the ~(137)Cs level in the Vuoksa River is ～3 times higher than in waters of the Volkhov and Svir rivers. During the period 1988-2015, 21.3 TBq of ~(137)Cs was supplied to Lake Ladoga with Vuoksa waters. The Vuoksa source from the Saima lake system with increased contamination with ~(137)Cs of Chernobyl origin leads to long-term supply of this radionuclide to Lake Ladoga.