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.

Determining the Chernobyl impact on sediments of a pre-Alpine lake with a very comprehensive set of data.

Man-made and natural radionuclides in Lake Wallersee were determined in the pre-Alpine environment at the northern slope of the Alps, which was heavily affected by the Chernobyl fallout in May 1986. The objective of this study was to get knowledge of location and quantity of man-made radionuclide input (especially (137)Cs) generated in the Chernobyl accident to lake sediments. Eleven sediment cores were sampled and activity depth profiles of (137)Cs and (210)Pb were determined with 5mm depth-resolution. The Chernobyl fallout produced an extreme (137)Cs peak in the sediment cores providing an excellent time marker. The chronological interpretation of deeper sediment layers was done by radiochemical analysis of (90)Sr and (239+240)Pu, which were released during atmospheric weapons' tests in the 1950s and 1960s. This allowed a complete chronological analysis of the sediment cores with a very compact set of data.