Relationship between radiocaesium in muscle and physicochemical fractions of radiocaesium in the stomach of wild boar.

After the accident at the TEPCO Fukushima Daiichi Nuclear Power Plant in 2011, it became important to study radiation dynamics, assess internal radiation exposure and specify factors affecting radionuclide variation in wildlife. Therefore, it is necessary to investigate which physicochemical fractions of radiocaesium (137Cs) are absorbed from ingested material in species with high activity concentrations of 137Cs, such as wild boar. This study analysed the physicochemical fractions of 137Cs in the stomach contents of wild boar to evaluate the transfer from ingested food to muscle. The 137Cs activity concentration in muscle showed a significantly positive relationship with the 137Cs activity concentration in the exchangeable fraction, and the sum of the 137Cs activity concentrations in the exchangeable and bound to organic matter fractions. Seasonal variations were also found in the 137Cs activity concentration in the exchangeable fraction, and the sum of the 137Cs activity concentrations in the exchangeable and bound to organic matter fractions. These findings suggest that the proportions of the physicochemical fractions of 137Cs in the exchangeable and bound to organic matter fractions in the stomach contents are important factors affecting the increases and seasonal dynamics of the activity concentrations of 137Cs in wild boar muscle.