Apparent non-linear relationship of radionuclide concentrations between crop and soil

In general radiological assessments, the radionuclide concentration in crops has been assumed to be linearly related to that in soil. For this assumption to be valid, the soil-to-plant transfer factor must be independent of the radionuclide concentration. The actual transfer from soil to plant, however, seems to be inversely related to the soil contamination level. The paper presents a numerical study which explains why the caesium concentration in crops appears to be non-linearly related to that in soil, and a new model describing soil-to-plant transfer is proposed. It is shown that the variation of the soil sorption characteristics among the sampled soils causes the apparent, inversely proportional relationship. (author). 13 refs, 5 figs, 1 tab