(A) study on the distribution of $^{90}Sr, ^{137}Cs, ^{241}Am$ and Pu isotopes in surface soils of Korea

Abstract

$^{90}Sr$, $^{137}Cs$, $^{241}Am$ and Pu isotopes, long half-lived artificial radionuclides, as an important radionuclides to have radiation effect to human have been considered major radionuclides in aspects of environmental monitoring around nuclear facilities. A study has been accomplished on these radionuclides in Korea is, however, very rare so far, consequently background database for these radionuclides in Korean environment are deficient. In this study, the concentrations and activity ratios of $^{90}Sr$, $^{137}Cs$, $^{241} Am$, $^{239+240}Pu$, $^{238}Pu$ and $^{241}Pu$ in surface soils(0 - 5 cm) collected from 27 location were determined and analyzed. Additionally, relationship between soil characteristics and those of these radionuclides was studied. The concentrations were in the range of $1.10 - 13.5 Bq kg^{-1}$ for $^{90}Sr$, $7.86 - 70.1 Bq kg^{-1}$ for $^{137}Cs$, $0.09 - 0.67 Bq kg^{-1}$ for $^{241}Am$, $0.18 - 1.85 Bq kg^{-1}$ for $^{239+240}Pu$, $0.006 - 0.062 Bq kg^{-1}$ for $^{238}Pu$ and $1.30 - 8.29 Bq kg^{-1}$ for $^{241}Pu$. Mean activity ratios of $^{137}Cs$/$^{90}Sr$, $^{239+240}Pu/^{137}Cs, ^{241}Am$/$^{239+240}Pu$ and $^{238}Pu$/$^{239+240}Pu$ were 10.7, 0.024, 0.39 and 0.038, respectively. The concentrations and activity ratios also are very similar to those reported from neighboring countries and from other mid-latitude locations in the northern hemisphere. The atomic ratio of $^{240}Pu$/$^{239}Pu$ was determined to be 0.18, which is fallout level resulted from nuclear weapon testing. The concentrations of $^{137}Cs$, $^{239+240}Pu$ and $^{241}Am$ is strongly correlated each other. The distributions of $^{90}Sr$, $^{137}Cs$, $^{241}Am$ and Pu isotopes depend more strongly on organic matter content than clay content and soil acidity of soil characteristics. The results obtained in this study would be valuable and can be utilized as a reference data against potential nuclear accident as well as the assessment of environment around n...