Analytical Sciences

Aging Effect of ¹³⁷Cs Obtained from ¹³⁷Cs in the Kanto Loam Layer from the Fukushima Nuclear Power Plant Accident and in the Nishiyama Loam Layer from the Nagasaki A-bomb Explosion

Tomoko OHTA,* Yasunori MAHARA,*,** Takumi KUBOTA,*** and Toshifumi IGARASHI*

*Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, N13W8, Sapporo, Hokkaido 060-8628, Japan
**Professor Emeritus, Kyoto University, Kyoto, Kyoto 606-8501, Japan
***Research Reactor Institute, Kyoto University, Sennangun, Osaka 590-0494, Japan

We measured ¹³⁴Cs and ¹³⁷Cs in the surface soil of the Kanto loam in the eastern Tokyo metropolitan area and the Nishiyama loam in Nagasaki, Japan. The observed ¹³⁷Cs deposition in the Kanto loam from the Fukushima nuclear power plant (NPP) accident ranged from 4.0 to 77 kBq m⁻², which corresponds to 0.3 – 5 times of that in the Nishiyama loam. The ¹³⁷Cs retardation factor in the Kanto loam obtained seven months after the Fukusima NPP accident and in the Nishiyama loam after 36 and 38 years from the detonation of the Pu atomic bomb (A-bomb) ranged from 180 to 260 and 2000 to 10000, respectively. This difference in the retardation factors is attributed to an aging effect that corresponds to seven months and 36 to 38 years after the deposition of ¹³⁷Cs occurred on the soil minerals.

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