Relationship between time-series changes of 129I, 137Cs in Japanese macaques and its depth in soil

Abstract

As of 2023, radioactive nuclides released due to the Fukushima nuclear accident still persist in the environment. In this study, an example of the dynamics of radioactive nuclides in a terrestrial ecosystem was investigated by measuring the ¹²⁹I and ¹³⁷Cs concentrations in captured Japanese macaques and soil in Fukushima Prefecture. Soil samples were measured at different depths, and the relationship between the half-life of radioactive nuclides in the soil surface and the ecological half-life of radioactive nuclides in Japanese macaques was examined. The results showed that the ¹²⁹I/¹²⁷I ratio in the Japanese macaques decreased as the capture date became more recent, and the rate of decrease was similar to that of ¹²⁹I in the surface soil. Furthermore, when comparing the ¹²⁹I/¹²⁷I ratio in individual macaques with the ¹²⁹I/¹²⁷I ratio in soil samples closest to their capture locations, a positive correlation between the two was observed. Overall, the amount of ¹²⁹I in the Japanese macaques appears to reflect the decay and contamination levels of ¹²⁹I in the surface soil.