The transfer of Sr-90, Cs-137, Co-60 and Mn-54 from soils to plants - results from lysimeter experiments

Outdoor lysimeter experiments were undertaken to determine the transfer factors for the radionuclides 90Sr, 137Cs, 60Co and 54Mn. Two soils with different properties were used: parabrown earth and a podzolic soil. Lysimeters,1 m2,were filled with soil of the Ap-horizon (40 cm deep) and 0.25 m2 lysimeters were filled with undisturbed soil profiles (50 cm deep). As test plants the essential agricultural crops such as pastures grass mixture, potatoes, sugar beets, winter wheat, summer barley and red clover were grown. A clear difference was found in uptake for all nuclides between a simulated accident situation (uniform application of the radionuclides to the 0-1 cm topsoil layer) and permanent contamination with an assumed load of 40 years after which radionuclides were mixed into the arable topsoil layer (0-20 cm). While the transfer factors measured on the sandy podzol in the simulated accident situation are 3-10 times lower than after permanent contamination, on average they are 2-4 times lower in the parabrown earth, rich in clay and silt. The radionuclides are slightly displaced from the contaminated 0-1 cm topsoil layer in spite of heavy rainfall during the winter season. The influence of the soil type differences between the plants on the transfer factors is discussed. (H.K.)