129I concentrations of mammalian thyroids in Taiwan

Abstract The 129 I and 129 I 127 I ratios in mammalian thyroids were determined by neutron activation analysis to estimate the 129 I concentrations in the biosphere due to fallout accumulation during the past decades in this island. The average 129 I 127 I ratio in thyroids of grazing animals, bovine and ovine, is about 1 × 10 −9 , three times higher than that of hosg. The 129 I 127 I ratio in rain water collected during the same period was found to be as high as 1.7 × 10 −8 and it is supposed to be the predominant source of 129 I in the biosphere. The 129 I concentrations in these mammalian thyroids are similar to those of non-direct contamination areas of the world, where the terrestrial 129 I contents are influenced by the global fallout.