Measurement and estimation of radiocesium discharge rate from paddy field during land preparation and mid-summer drainage

In this research, we evaluated the range of 137Cs discharge rates from paddy fields during land preparation and mid-summer drainage. First, we investigated 137Cs discharge loads during land preparation and mid-summer drainage and their ratio to the 137Cs inventory of paddy field soil. We found that total discharge rates were 0.003-0.028% during land preparation and 0.001-0.011% during mid-summer drainage. Next, we validated the range of obtained total discharge of 137Cs from the paddy fields using a simplified equation and literature review. As a result, we conclude that the range of total outflow loads of suspended solids for the investigated paddy field was generally representative of paddy fields in Japan. Moreover, the 137Cs discharge ratio had a wide range, but was extremely small relative to 137Cs present in paddy field soil before irrigation.