Concentration and specific activity of fallout ¹³⁷Cs in extracted and particle-size fractions of cultivated soils

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• 作者：Hirofumi Tsukada ; Akira Takeda ; Shun'ichi Hisamatsu ; Jiro Inaba
• 关键词：Fallout ¹³⁷Cs ; Stable Cs ; Specific activity ; Cultivated soil ; Exchangeable ; Organic bound ; Strongly bound ; Particle-size distribution
• 刊名：Journal of Environmental Radioactivity
• 出版年：2008
• 期刊代码：45_0265931x
• 类别：env
• 出版时间：June 2008
• 卷：99
• 期：6
• 页码：875-881
• 文件大小：287 K

摘要

Fallout ¹³⁷Cs and stable Cs in soils were separated with two extractants (1 M CH₃COONH₄ solution and 0.8 M CH₃COONH₄ in 5%HNO₃ solution after H₂O₂ oxidization). The residue remaining after removal of the oxidizable organic-bound fraction was separated into the particle-size fractions including clay, silt, fine sand and coarse sand with a sieving and sedimentation method. Then, the concentrations of ¹³⁷Cs and stable Cs in the extracted fractions and the particle-size fractions were determined. The ¹³⁷Cs contents in the exchangeable and organic-bound fractions in the soil were approximately 10 and 20%, respectively. The ¹³⁷Cs content in the strongly bound fraction was about 70%, and the concentration of ¹³⁷Cs in the clay was the richest among the particle-size fractions. The specific activity of ¹³⁷Cs (concentration ratio of fallout ¹³⁷Cs/stable Cs) decreased in the order exchangeable, organic-bound and strongly bound fractions. The data suggest that equilibrium between ¹³⁷Cs and stable Cs was not reached among those fractions, even though most of the ¹³⁷Cs that had been deposited on the soil was derived from fallout weapons tests that occurred several decades ago. The concentration of ¹³⁷Cs among the particle-size fractions in each soil was different, whereas the specific activity of ¹³⁷Cs in the particle-size fractions had a relatively similar value.