[M-AG38_2AM1] 福島原発事故により放出された放射性核種の環境動態

[MAG38-04] つくばにおける福島事故後6ヶ月間の大気中の放射性セシウム担体に関する研究

*兼保 直樹¹、小暮 敏博²、向井 広樹²、大橋 英雄³、鈴木 芙美恵³、赤田 尚史⁴、奥田 知明⁵、池盛 文数⁶ (1.産業技術総合研究所、2.東京大学大学院理学研究科、3.東京海洋大学、4.核融合科学研究所、5.慶應義塾大学理工学部、6.名古屋市環境科学調査センター)

キーワード：放射性セシウム, 粒径分布, 再飛散, 電子顕微鏡, オートラジオグラフ

To obtain the knowledge on the physico-chemical properties of airborne radionuclides, we had been collected size-resolved aerosol in Tsukuba, Japan, since April 28, 2011, although the data obtained do not include the first radioactive plumes that reached to Tsukuba on March 15, 2011. From the initial result, we proposed a hypothesis that the sulfate aerosol was the potential carrier of the ¹³⁴Cs and ¹³⁷Cs that had undergone the middle- to long-range transport from the damaged reactor. We further inferred that re-suspended soil particles that attached radionuclides were not the major airborne radioactive substances from late April to May, 2011 (Kaneyasu et al., 2012). Nevertheless, there are some issues to be addressed on the nature of airborne radionuclides. Those are, a) until when the sulfate aerosol acted as a carrier of the radiocesium released from the reactor, or the other substances acted as carriers instead, and b) what is the carrier substance when the re-suspension or re-emission of became the dominant source in the airborne radiocesium.In this study, we address these subjects by analyzing the long-term aerosol samples collected later than those presented in the previous study. The temporal change in the activity size distribution of radiocesium for six month will be discussed. In addition, the carrier substance of radiocesium in the coarse mode size range aerosol is investigated by use of the autoradiograph and scanning electron microscope to the aerosol sample collected in 2011 summer.