Application of 2-component model to the removal of 90Sr in paddy-field soil

The 2-component model was applied for the estimation of the removal of exchangeable 90Sr in paddy-field soil. The monitoring data of exchangeable 90Sr in paddy-field soil and global fallout 90Sr data from 1963 to 1995 at 11 sites in Japan were used for this analysis. From the results of nonlinear regression analyses, it is concluded that the 2-component model is more suitable for the estimation of the time-dependent concentration of exchangeable 90Sr in paddy-field soil than the 1-component model. The values of the environmental half-lives of rapid component and slow component, which are parameters of the 2-component model, were estimated as 2 y and 10 y, respectively. It was estimated that the ratio of rapid component changes from 0.81 to 0.98. (author)