engleski

Radiocaesium in a brown bear population from the Croatian Dinarides: activity concentration in muscle tissue and transfer from forest soil to organism

Radiocaesium (137Cs) is a fission radionuclide that can easily bioaccumulate on all trophic levels due to its physicochemical properties and relatively long half-life. It is especially efficiently trapped by forest ecosystems where it can persist for a long time. Therefore, the detection of significantly higher contents of 137Cs in game animals, in comparison to domestic ones, is not uncommon. However, very few studies have been conducted on the presence of 137Cs in bears. This study determined the content of 137Cs in a brown bear (Ursus arctos) population that inhabitates the area of the Croatian Dinaric mountains. Activity concentrations of 137Cs were determined by gamma spectrometry in the muscle tissue of 65 animals collected in the period 2013- 2018. The measured activity concentrations ranged from 0.6-33 Bqkg-1 with a mean value of 6 ± 7 Bqkg-1. In comparison with literature data for a Swedish brown bear population and Asian black bears (Ursus thibetanus) from the Fukushima Prefecture in Japan, these results are up to two orders of magnitude lower. The results of the comparison could be a reflection of the differences in the athmospheric deposition of 137Cs in habitats of these bear populations following the Chernobyl and Fukushima accidents indicating 137Cs content in forest soil as a prevalent factor for the prediction of bear contamination on a population level. In order to estimate 137Cs transfer from forest soil to bear organism, concentration ratios (CRs) between 137Cs in bear samples and 137Cs in soil (literature data) were calculated. CRs ranged from 0.01 to 0.89, with a mean value of 0.13 ± 0.16. These CRs were one order of magnitude lower than the generic ones proposed by the International Atomic Energy Agency for omnivorous mammals and the same order of magnitude as the ones for carnivorous mammals.

radionuclide, brown bear, transfer, forest

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