Time-dependence of the radiocaesium contamination of roe deer: measurementand 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 s uperimposed periodic maxima in autumn which are correlated with the mushroo m 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 unavaila ble for green grazing plants with time. The additional transfer of Cs-137 i nto roe deer meat during the mushroom season depends on precipitation in Ju ly, August and September which also determines the yield of fungi in autumn . Our model confirms the assumption that fungi also have access to a fracti on 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 bindi ng of Cs-137 to organic matter in the peat bog. (C) 2001 Elsevier Science L td. All rights reserved.