Time-dependence of the radiocaesium contamination of roe deer: measurement and modelling

In spruce forest and peat bog, the migration of Cs-137 from soil to plants, Fungi, roe deer and consumers has been surveyed. In spruce forest the (13)7Cs activity concentration in roe deer decreases slowly with time and has superimposed periodic maxima in autumn which are correlated with the mushroom season. The decrease with time can be described by an effective half-life of 3.5 yr caused by a fraction of the Cs-137 in the soil becoming unavailable for green grazing plants with time. The additional transfer of Cs-137 into roe deer meat during the mushroom season depends on precipitation in July, August and September which also determines the yield of fungi in autumn. Our model confirms the assumption that fungi also have access to a fraction of the Cs-137 in the soil which is unavailable for green plants. On peat bog the Cs-137 activity concentration in roe deer is higher than in spruce forest and its effective half-life is about 17 yr, due to reversible binding of Cs-137 to organic matter in the peat bog. (C) 2001 Elsevier Science Ltd. All rights reserved.