日本地球惑星科学連合2014年大会

講演情報

口頭発表

セッション記号 M (領域外・複数領域) » M-TT 計測技術・研究手法

[M-TT42_2AM2] 地球化学の最前線:先端的手法から探る地球像

2014年5月2日(金) 11:00 〜 12:45 314 (3F)

コンビーナ:*横山 祐典(東京大学 大気海洋研究所 海洋底科学部門/地球表層圏変動研究センター)、鍵 裕之(東京大学大学院理学系研究科附属地殻化学実験施設)、橘 省吾(北海道大学大学院理学研究院自然史科学専攻地球惑星システム科学分野)、平田 岳史(京都大学大学院理学研究科地球惑星科学専攻)、角皆 潤(名古屋大学大学院環境学研究科)、鈴木 勝彦(独立行政法人海洋研究開発機構・地球内部ダイナミクス領域)、下田 玄(産業技術総合研究所地質調査総合センター)、角野 浩史(東京大学大学院理学系研究科附属地殻化学実験施設)、小畑 元(東京大学大気海洋研究所海洋化学部門海洋無機化学分野)、高橋 嘉夫(広島大学大学院理学研究科地球惑星システム学専攻)、横山 哲也(東京工業大学大学院理工学研究科地球惑星科学専攻)、座長:鍵 裕之(東京大学大学院理学系研究科附属地殻化学実験施設)、橘 省吾(北海道大学大学院理学研究院自然史科学専攻地球惑星システム科学分野)、横山 祐典(東京大学 大気海洋研究所 海洋底科学部門/地球表層圏変動研究センター)

11:45 〜 11:55

[MTT42-P03_PG] 放射性セシウムの固相吸着に与える有機物の阻害効果: チェルノブイリ市プリピャチ川の懸濁粒子分析

ポスター講演3分口頭発表枠

*菅 大暉1Fan Qiaohui1武市 泰男2田中 万也3近藤 宏壮1Kanivets Vladimir V4坂口 綾1井波 暢人2小野 寛太2高橋 嘉夫1 (1.広島大学理学研究科地球惑星システム学専攻、2.高エネルギー加速器研究機構物質構造科学研究所、3.広島大学サステナブル・ディベロップメント実践研究センター、4.ウクライナ水分気象学研究所)

キーワード:chernobyl, natural organic carbon, STXM

Radiocesium have been emitted to environment originated from nuclear weapon tests and nuclear accidents such as in Chernobyl and Fukushima. Among various sources, the nuclear accidents in Chernobyl and Fukushima have caused serious contaminations in land-surface around these areas due to the deposition of the radionuclides dispersed via. atmosphere as aerosols. Subsequently, radiocesium can be transported via rivers into oceans. In the soil- river-sediment system, radiocesium has high affinity for particulate matters, in particular for clay minerals. The high affinity has been shown to be the results of specific adsorption to frayed edge site (FES) and interlayer site in 2:1 phyllosilicate as inner-sphere (IS) complexes. However, it has been indicated that cesium adsorption to clay minerals can be blocked by natural organic matters (NOM) that adsorb on the mineral surface. NOM are ubiquitous and play various important roles on the adsorption of metal ions on particulate matters such as (i) promotion of adsorption of metal ions by the complexation with NOM and (ii) inhibition of adsorption by covering the particulate matters. High availability of Cs in soils with relatively high organic matter content was explained in terms of the blocking of access of cesium to specific adsorption sites (such as FES and interlayer site) of the clay mineral.
In river waters in Fukushima, it has been indicated that more than 70% of radiocesium is adsorbed on particulate matters. In contrast, Sansone et al. (1996) showed that more than 70% of radiocesium was in the dissolved fraction in Chernobyl. One critically important difference between the two sites is that peat, which contains large amount of NOM, is the main surface layer in the Chernobyl area. These NOM can be introduced into the Pripyat River that can coat on the particulate matters in river waters. Thus, it is possible that high content of NOM in rivers (e.g., Pripyat River) in Chernobyl can be responsible for the larger fraction of dissolved radiocesium compared with that in Fukushima due to the blocking effect by the NOM. In this study, therefore, adsorption of cesium on particulate matters collected in the Pripyat River with the characterization of the particulate matters have been conducted to study whether the blocking effect is affecting the adsorption behavior of cesium.
Here, we examined Cs LIII-edge extended x-ray absorption fine structure (EXAFS) to study the cesium species adsorbed on the particulate matters collected from Pripyat River and also on the particulate mattes after the removal of NOM by the treatment with hydrogen peroxide. To characterize the particulate matter, distribution image of organic substances on the particulate matter was analyzed by compact Scanning Transmission X-ray Microscope (cSTXM) newly developed in Photon Factory, KEK in Tsukuba, Japan. After the cSTXM imaging, characterization of NOM was conducted by near edge X-ray absorption fine structure (NEXAFS) at the C K-edge measured for the NOM by cSTXM.
From this study, blocking effect of cesium adsorption to clay minerals by humic acid was confirmed in natural particulate matter in Pripyat River, which might be related to the larger dissolved fraction of radiocesium around Chernobyl area, compared with that in rivers in Fukushima area.