Distribution and characteristics of 239,240Pu and 137Cs in the soil of Korea

The concentrations of 239,240Pu and 137Cs were determined in undisturbed surface soil (0–4 cm) in Korea. They were in the range of 0.24˜1.1 Bq kg−1 and 12.4˜55.6 Bq kg−1, respectively. The mean activity ratio of 239,240Pu/137Cs in soil was 0.0224, which is very similar to the estimated value (0.0211) commonly attributed to the atmospheric nuclear test. The influence of rainfall on the deposition of 239,240Pu and 137Cs, and the effect of organic matter content, clay content and pH on the relative adsorption of the two radionuclides on the surface soil were studied using the field method. Among parameters affecting the cumulative deposition of the radionuclides, the organic matter content plays the most important role in the retention and relative mobility of 239,240Pu and 137Cs in the soil. The other parameters such as rainfall, clay content and pH were of less significance.