Radiocaesium transfer to roe deer and moose - a comparative study

The Swedish Radiation Protection Institute, 17116 Stockholm, Sweden

Abstract

The paper describes the results of a comparative study of the seasonal and long-term dynamics of the levels of ¹³⁷Cs in roe deer and moose harvested in a relatively small area (100 km²) of central Sweden. Samples of roe deer (N=1084) and moose (N=1922) were collected in 1988-1997 mainly during the hunting seasons. It is shown that the long-term decrease of ¹³⁷Cs levels in roe deer and moose is dominated by ¹³⁷Cs radioactive disintegration. Any other possible long-term trend of ¹³⁷Cs levels in these game animals is obscured by large and non-systematic between-years variations. A significant correlation between the levels in roe deer in August-September and the levels of ¹³⁷Cs in moose in October was observed. This correlation can explain 70 % of the between-years variation of the levels of ¹³⁷Cs in moose. The presented data indicate that there is a strong relationship between ingestion of fungi and the levels of ¹³⁷Cs levels in roe deer and moose during the summer-autumn period. This seems to be the main cause for the seasonal variations of ¹³⁷Cs levels in roe deer and the between-years variations in ¹³⁷Cs levels in roe deer in August-September and in moose in October observed in the study area. A significant correlation between the levels of ¹³⁷Cs in moose and the amount of rain in July-September was observed, which supports this conclusion. The number of fruit bodies of Suillus variegatus counted in six experimental plots located in the study area also confirms the important role of the ingestion of mushrooms. Estimations of the mushroom contribution to the total daily ingestion of food by roe deer and moose are provided.