Sedimentation and distribution of gamma-emitting radionuclides in bottom sediments of southern Lake Päijänne, Finland, after the Chernobyl accident

The rates of sedimentation of fallout nuclides following the Chernobyl accident were determined using sediment traps in southern Paijanne lake, Finland during 1986-1989. The spatial distribution of the radionuclide content of the lake bottom was studied in 35 cores. Initially the sediment traps revealed caesium-137, caesium-134, rubidium-106, cerium-144, antimony-125, 110m-silver. The highest concentration of caesium-137 and caesium-134 were 194,000 and 91,000 Bq per kg, respectively. The concentrations decreased rapidly during the following months. The core indicated a considerable spatial variation in the content of the radionuclides on the lake bottom. Unexpectedly high concentrations on shallow erosion bottoms were explained by the direct adsorption of radiocaesium. Concentrations increased with depth. The role of sediment resuspension on the total flux of radionuclides is discussed. There are 44 references.