The influence of fungi on the long-term behaviour of radiocaesium in Norwegian sheep

Results from 11 years of live monitoring of sheep from a grazing area in Norway formed the basis for a study of the importance of ingested fungal fruit bodies in determining radiocaesium activity concentrations in sheep grazing freely on mountain pasture. The 137Cs activity concentration due to ingested vegetation decreased with an estimated effective ecological half-life of 7.0 +/- 2.6 years. The contribution from ingested fungal fruit bodies to radiocaesium activity concentrations in the sheep was up to 75-85% in the years when fruit bodies were most abundant. The study demonstrates that using a simple exponential function in assessments of long-term consequences of radiocaesium fallout for grazing sheep may be inappropriate.