On 137Cs migration in water systems of Eastern Fennoscandia

The rate of natural removal of ¹³⁷Cs from water bodies in Eastern Fennoscandia is evaluated. The half-time T of water purification from global ¹³⁷Cs in lake–river systems was ~6.5 years and that for river systems was 6.5–10 years. For the 15- and 20-year exposure of ¹³⁷Cs in watershed soils, its annual input in rivers was 0.021–0.120 and 0.017–0.070% of its reserve. The period of May–December 1986 showed maximal export of ¹³⁷Cs, i.e., 1.1% of its reserve. ¹³⁷Cs export into rivers decreased in the region from north to south because of changes in landscape and climate conditions that affect ¹³⁷Cs migration on watersheds.