Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages

Soil blocks from 18 paddy fields around three Korean nuclear power plant sites were put into lysimeters. Greenhouse experiments were carried out to investigate the (137)Cs transfer from these paddy soils to rice plants for its deposition at different growth stages. A solution of (137)Cs was applied to the flooded lysimeters at 2-3 different stages. The applied (137)Cs was mixed with the topsoil only at the pre-transplanting application. The transfer was quantified with a transfer factor based on the unit-area deposition (TF(a), m(2)kg(-1)-dry). The TF(a) in the pre-transplanting application showed a remarkable variation with the soils. However, the differences in the mean values among the study sites were not statistically significant. The straw TF(a) was 2-3 times higher than the corresponding seed value. The early-tillering stage and booting stage applications resulted in a higher transfer than the pre-transplanting application by factors of, on an average, 2 and 16 for the straws, and 3 and 25 for the hulled seeds, respectively. The (137)Cs transfer was found to correlate negatively with the soil pH and positively with the organic matter content. Based on the present results, the representative (137)Cs TF(a) values for the rice are proposed for use in the whole of Korea for the deposition at three different growth stages.