Elevated rice 137Cs concentrations near the water inlet in paddy fields after the Fukushima nuclear accident

The reasons why rice 137 Cs concentrations increase near the water inlet were investigated using rectangular experimental plots settled in paddy fields. The 137 Cs concentrations in brown rice and rice straw were highest at 1 m from the inlet and decreased gradually with increasing distance, showing a negative correlation with soil exchangeable potassium content (Ex-K). The 137 Cs concentration in brown rice was negatively and positively correlated with yield and sterility rate, respectively. These results suggest that soil Ex-K reduction and rice anomalies occurred near the water inlet and could contribute to the local elevation of 137 Cs concentrations in rice.