Investigations on the caesium-137 household of Lake Lugano, Switzerland

Sediment samples were taken from different basins of Lake Lugano, and the c aesium 137 inventory and vertical distribution was measured. In all samples , a distinct maximum at a depth of 5 to 10 cm can be attributed to the 1986 Chernobyl fallout. Relatively high specific activities of 500 to 1,000 Bq/ kg can still be found in the top layer of the sediment. 5 step extraction e xperiments on sediment samples resulted in percentages of extracted caesium which are a factor of 2 to 8 higher than those of Lake Constance, where ca esium is strongly bound to illites. The activity concentration of the water of 3 main tributaries, of the outflow, and of the lake water was in the or der of 5 to 10 mBq/l.