Distributions of 137Cs and 90Sr in the Soil of Uljin, South Korea

Title & Authors
Distributions of 137Cs and 90Sr in the Soil of Uljin, South Korea
Song, JiYeon; Kim, Wan; Maeng, Seongjin; Lee, Sang Hoon;

Abstract
Background: For the purpose of baseline data collection and enhancement of environmental monitoring the distribution studies of $\small{^{137}Cs}$ and $\small{^{90}Sr}$ in the soil of Uljin province was performed and the relation between surface soil activities and soil properties (pH, TOC and median of the surface soil) was analyzed. Materials and Methods: For 14 spots within 10 km from the NPP surface soil samples were collected and soils for depth profile were sampled for 3 spots in April 2011. Using $\small{{\gamma}}$-ray spectrometry with HPGe detector, the concentrations of $\small{^{137}Cs}$ were determined and the concentrations of $\small{^{90}Sr}$ were measured by counting $\small{{\beta}}$-activity of $\small{^{90}Y}$ (in equilibrium with $\small{^{90}Sr}$) in a gas flow proportional counter. Results and Discussion: The concentration ranges of $\small{^{137}Cs}$ and $\small{^{90}Sr}$ were $\small{}$<$\small{0.479-39.6Bq{\cdot}(kg-dry)^{-1}}$ (avg. $\small{7.51Bq{\cdot}(kg-dry)^{-1}}$) and $\small{0.209-1.85Bq{\cdot}(kg-dry)^{-1}}$ (avg. $\small{0.74Bq{\cdot}(kg-dry)^{-1}}$) which were similar to the reported values from other regions in Korea. The activity ratio of $\small{^{137}Cs}$ to $\small{^{90}Sr}$ in surface soils was around 9.67, which is much bigger than the initial value of 1.75 for worldwide fallouts because of faster downward movement of $\small{^{90}Sr}$ after fallout than that of $\small{^{137}Cs}$. For depth profile studies soils were collected down to 40 cm depth for the locations of Deokgu, Hujeong and Maehwa. The $\small{^{137}Cs}$ concentration distribution of the first two showed maximum values at top soils and decreased rapidly in exponential manner, while $\small{^{90}Sr}$ showed two local maximum values for soils near top and about 30 cm depth. Through linear fittings between the $\small{^{137}Cs}$ and $\small{^{90}Sr}$ concentrations of surface soil and pH, TOC and median of the surface soil, the only probable relationship obtained was between $\small{^{137}Cs}$ and TOC (determination coefficient $R^2 Keywords Environmental radioactivity;$\small{^{137}Cs}$;$\small{^{90}Sr}$;Soil;Uljin; Language Korean Cited by References 1. Korea Institute of Nuclear Safety. The annual report on the environmental radiological surveillance and assessment around the nuclear facilities. KINS/AR-140. Daejeon, Republic of Korea. 2010;46-51. 2. KNS Committee on the Fukushima Accident. Final report on Fukushima NPP accident analysis. Korean Nuclear Society. 2013;60-69. 3. Cooper JR, Randle K, Sokhi RS. Radioactive releases in the environment. 1st Ed. John Wiley & Sons. 2003;1-24. 4. Cha HJ, et al. Vertical distribution of$^{137}Cs$and$^{90}Sr$activities in the soils of Korea. Journal of Radiation Protection and Research. 2004;29(3):197-204. 5. Willard HH, Goodspeed EW. Separation of strontium, barium, and lead from calcium and other metals - by precipitation as nitrates. Ind. Eng. Chem. 1936;8(6):414-418. 6. Korea Institute of Nuclear Safety. Environmental radioactivity survey in Korea. KINS/ER-028. Daejeon, Republic of Korea. 2011;85-86. 7. Kirchner TB, Whicker FW, Otis MD. PATHWAY: A simulation model of radionuclide-transport through agricultural food chains. Third International Conference on State-of-the Art in Ecological Modeling, Colorado State Univ. Ft. Collins, CO. 1982 May 24-28;10. 8. Thornthwaite CW, Mather JR, Nakamura JK. Movement of radiostrontium in soils. Science. 1960;131(3406):1015-1019. 9. Russell RS. Deposition of$^{90}Sr$and its content in vegetation and in human diet in the United Kingdom. Nature. 1958;182:834-839. 10. He Q, Walling DE. Interpreting particle size effects in the adsorption of$^{137}Cs$and unsupported$^{210}Pb\$ by mineral soils and sediments. J. Environ. Radioact. 1996;30(2):117-137.