PERSISTENCE AND PREDICTION OF RADIOCESIUM LEVELS IN ANIMALS GRAZING SEMINATURAL ENVIRONMENTS

In vivo monitoring of radiocaesium levels in a flock of mountain sheep grazing a heather-dominant peatland ecosystem was undertaken over a 3 -year period from 1989 to 199 1. Highest values were observed during s ummer and autumn and measurable radiocaesium activities were present t hroughout the year. Comparably high mean and maximum values recorded i n November 1989 are thought to be a result of fungi consumption. Analy sis of variance indicated that an increase of 4% occurred in radiocaes ium levels in muscle between 1989 and 1990 followed by an overall decr ease of 35% between 1990 and 1991. In order to test an existing model to predict radiocaesium levels in muscle from measured activities in f aeces, an independent data set was produced. The radiocaesium content of faecal samples collected from the grazing range of a sheep flock wa s compared with the results of in vivo measurements on the same animal s. The correlation over time between the predicted and observed flock mean and maximum values was found to be significant, thereby confirmin g the value of faeces sampling as an inexpensive and rapid means of as sessing the distribution of radiocaesium activities in sheep flocks gr azing semi-natural ecosystems.