Accumulation of Chernobyl-Derived super(137)Cs in Bottom Sediments of Some Finnish Lakes

The vertical distribution and accumulation of cesium 137 derived from the April 1986 nuclear accident at Chernobyl, Ukraine, in bottom sediments of some Finnish lakes were determined. Sediment and surface water samples collected in 2000 and 2003 from 12 stations in nine lakes were assayed, and results were contrasted with those documented in similar surveys conducted in 1969, 1978, 1988, and 1990. Depth profiles of super(137)Cs in sediments displayed great variety in the lakes, and peak values were in the 1.5-46 kBq/kg range. The size and shape of the peak did not also correspond to the amount of deposition in the area but reflected differences in sedimentation processes. The total amounts of super(137)Cs in sediments were in the 15-170 kBq/m super(2) range, and concentrations increased slightly in two lakes since 1990 but declined in others.