137Cs-migration in soils and its transfer to roe deer in an Austrian forest stand

The depth distribution of 137Cs in an Austrian spruce forest stand was investigated in soil profiles sampled in thin layers (2 cm) and in pooled soil samples over an area of 200 ha. The 137Cs concentrations both from Chernobyl and global fallout decrease exponentially with depth. Forty-six percent of Chernobyl-derived caesium and 26% from global fallout are still to be found in the litter layer; <3% (for global fallout 6%) have reached layers deeper than 20 cm of mineral soil. Correlation analysis showed a significant dependence of 137Cs content in samples on organic matter as well as cation exchange capacity. Using a compartment model, average residence half-times of 5.3, 9.9, 1.78 and 0.8 years were calculated for the layers litter, 0-5 (Ah1), 5-10 (Ah2) and 10-20 cm (A/B) of mineral soil, respectively. Using the model predictions of soil contamination as a basis and considering the roe deer forage plants' rooting depths, the development of 137Cs contamination of roe deer (Capreolus capreolus) (1987-1993) was well described by applying an aggregated transfer factor.