Caesium-137 in perch in Swedish lakes after Chernobyl -present situation, relationships and trends

The Chernobyl accident, and the general acidification of Swedish water systems, form the base for this project. The aims of the work have been to present results on the linkage between the concentration of Cs-137 in fish, lake load of Cs and lake characteristics, to give a preliminary prognosis on the recovery, and to put the results within a wider framework of environmental hazard analysis. A broad set of data on limnology, morphometry and drainage area conditions from 41 lakes were collected during 1986 and 1987. Cs-137 was determined in 1+perch (Cs-pe, 1-year-old perch), water, material collected by sediment traps and from surficial sediments. The main results are as follows. The average value of Cs-pe for all lakes has dropped from 9800Bq kg-1 (wet) to 5040 between the 2 years. Generally, the decrease is between 5 and 90%. The concentrations of Cs in sediment traps have, on average, decreased by 80%. Very high correlations exist between Cs-pe and the caesium load as determined from the sediment traps. (author)