Determination of (137)Cs in the water system of a pre-Alpine lake

The aim of this study was to measure the (137)Cs activity derived from the Chernobyl accident in the water system of Lake Wallersee, a pre-Alpine lake in Austria within an area highly contaminated by the Chernobyl fallout. For this purpose, water and sediment samples of the inflows and the outflow of Lake Wallersee and lake water at different depths were collected in 2005. The obtained (137)Cs activity depth profile in the water body shows an exponential increase of (137)Cs activity in the lake water with increasing depth. Inflow and outflow sediment analyses exhibit a clear negative correlation between particle size and specific activity for (137)Cs and (40)K in sediment samples following a power function. In a first approach it was tried to calculate the catchment run-off factor of (137)Cs during a period without heavy rainfalls. The result is in good agreement with run-off factors determined in other similar investigations in Austria.