During the development of a method using effective microorganisms (EM) to reduce the soil-to-plant transfer of 137Cs on land contaminated with radioactive Cs, an unexpected effect of EM on the reduction of the 137Cs activity in soil samples was observed. Laboratory experiments were then conducted to evaluate the impact of EM and fermented organic fertilizer (EM Bokashi) on the 137Cs activity in soil samples to investigate this observation. The experimental results indicate an increase in the 137Cs decay rate of up to 4 times the theoretical decay rate corresponding to the half-life of 137Cs, which is equal to 30.17 years. Our results suggest that EM accelerates the radioactive decay of 137Cs in soil.
