137CS interactions between soil contamination and hydrosphere

In the contributed study the amount of 137Cs loss via surface water and transported sediments from catchments of different landscape characteristics and size was quantified. At the first investigation site (small semi-natural catchment (9.2 km2) in the Northern Granite Highlands of Austria, vegetation cover: forests and meadows, partly bog sites; soil pH < 5, loamy sands rich in organic matter; 137Cs inventory: 55.3 kBq/m2) the 137Cs concentration in small surface water flows amounted to 6.4 + 1.6 mBq/l in the dissolved phase and 3.5 ± 1.4 mBq/l (reference date: 1986-05-01) bound to suspended particles. Annual export rates in the observed subcatchments varied between 78-167 x 10-6 per year, seasonal variation of observed data was considerable. The second investigation site was situated in the Lake district of the Austrian Alps, the River Traun catchment (1492 km2, 50.8 kBq/m2 137CS soil contamination) agricultural land, meadows, calcareous landscape), it was divided into several subcatchments, where river water was sampled. Additionally, from some lakes (Traunsee, Hallstaedter See) sediment cores were taken to determine the 137Cs depth distribution and the radionuclide amount stored within lake bottom sediments. 137Cs concentration in surface waters of river Traun and its inflows was 0.41 ± 0.44 mBq/litre (dissolved phase) plus 1.28 ± 1.16 mBq/l in the suspended sediment. Derived export rates of 150 x 10-6 are comparable to the upland catchment, but the relation between sediment and dissolved transport was distinctly different. Results from Lake Traunsee sediment core analysis were used to calculate the sedimentation rate and the 137Cs input to the lake respectively.