東日本放射線セシウムに汚染された土地利用別土壌特性の影響 李敏 1 箭田佐依子 2 江口定夫 2 高橋純子 3 田村憲司 3 浅野眞希 3 恩田裕一 3 世良耕一郎 4 1 筑波大学生命環境科学研究科 305-8572 茨城県つくば市天王台 1-1-1 2 農業環境技術研究所 305-8604 茨城県つくば市観音台 3-1-3 3 筑波大学生命環境系 305-8572 茨城県つくば市天王台 1-1-1 4 岩手医科大学サイクロトロンセンター 020-0603 岩手県滝沢市留が森 348-58 要旨福島第一原発の事件で 放射性セシウム 特にセシウム 137 Cs は非常に長い半減期のため環境に最も深刻な影響を及ぼすと思われている セシウムは粘土鉱物と関連している 放射性セシウム捕捉 ( ほそく ) ポテンシャル ( 以下 RIP) は選択的に放射性セシウムを吸着する能力の点またはミネラルを分類するために使用することができる固有の土壌パラメータである Si Al 等の元素の量は PIXE で測定した 今回は土地利用別の土壌の RIP と元素量との関係について報告する 139
The effect of different land use types on 137 Cs contaminated soil of northern Japan Min Li 1, Saeko Yada 2, Sadao Eguchi 2, Junko Takahashi 3, Kenji Tamura 3, Maki Asano 3, Yuichi Onda 3 and Koichiro Sera 4 1 Graduate School of Life and Environmental Sciences, University of Tsukuba 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan 2 National Institute for Agro-Environmental Sciences 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan 3 Faculty of Life and Environmental Sciences, University of Tsukuba 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan 4 Cyclotron Research Center, Iwate Medical University 348-58 Tomegamori, Takizawa, Iwate 020-0603, Japan Radioactive cesium, especially 137 Cs is deemed to the most important contributor to environmental contamination because of its long half- life period released by the explosion of Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in 2011. The Radiocaesium Interception Potential(RIP) has been researched in past works. It has been well established that cesium is tightly bound by the clay minerals of the soil, The RIP is an intrinsic soil parameter which can be used to categorize soils or minerals in terms of their capacity to selectively adsorb radiocesium, and for analyzing the content of clay minerals, the elements was determined by Particle-induced X-ray emission (PIXE) because of the quantity of samples and the high sensibility of PIXE. The soil samples were from different provinces around the FDNPP and were taken 0.5cm of surface. The relevance of RIP and elements under different land use types will be showed in this report. 1 Introduction In the earthquake of Mar. 11st 2011, the explosion of Fukushima Dai-ichi NPP made the rounding environment contaminated, 137 Cs is deemed to the most important contributor to environmental contamination because of its long half- life period. It has been well established that cesium is so tightly 140
bound by the clay minerals of the soil, the radioceasium ion can exchange with the clay minerals 1. In previous work the immobilization of Cs and the Radiocaesium Interception Potential(RIP) have been researched. The RIP is an intrinsic soil parameter which can be used to categorize soils or minerals in terms of their capacity to selectively adsorb radiocaesium 2, Cs keeps the selection of Siloxane Ditrigonal Cavity on the clay particle and Frayed Edge site 3. The content of elements(si, Al) were determined by Particle-induced X-ray emission (PIXE), The objective of this work is to show the relevance of RIP and Si & Al in different land use type soils, and the relationship between RIP and content of C&N. 2 Method and Materials 2.1 Sampling sites and material The samples were from the fukushima radiation monitoring of water soil and entrainment team, and were taken from top 0~0.5cm. 2.2 Methods 2.2.1 For RIP: The solution of the container with the dialysis bag was changed 10 times during 7 days. During equilibration, the containers were agitated for 2 h more than each 12 h. Each dialysis bag was then transferred in a new container filled with 94 ml of the KCl-CaCl2 equilibration solution labeled with carrier-free 137 CsCl. These bags were again agitated for 2 h each 12 h. After 5 days, aliquots of 10 ml were taken and 137 Cs activity of the equilibrium solution was measured by gamma-counting 4,5. 2.2.2 For PIXE: Fill about 1g soil sample to the bottles which weighted and fill in about 5ml water and standing. Take the supernatant and weight, and take about 0.95 suspended solid and 5ml In standard to make a 50ppm mixture. Take 7ul mixture to the holder and dry and elemental analysis. 3 Results In different region, RIP values of samples from Fukushima are 241.705~2142.136mmol/ kg; RIP of samples from Miyagi are 225.418~1104.083 mmol/ kg; RIP of samples from Ibaraki are 213.464~778.265 mmol/ kg; RIP of samples from Tochigi are 172.489~694.824 mmol/ kg, and then the results were showed in different land type uses (Figure 3.2), and there are no obvious relationship between Si and RIP or Al and RIP in residence sites or farmland (Figure 3.3.1, Figure 3.3.2). The content of C are 0.20%~15.80%, content of N are 2%~1.2%. From histogram of RIP (Figure 3.4), 3 high groups were chosen for comparing the relationship between RIP and C&N, they are all showed positive trend (Figure 3.5.1, Figure 3.5.2). 141
Concentration(Bq/kg) 45000 40000 35000 30000 25000 20000 15000 10000 5000 0 Consentration of 137 Cs in 0~0.5cm 1 3 5 7 9 111315171921232527293133353739414345474951535557596163656769 Figure 3.1 consentration of 137 Cs in 0~0.5cm 25000 Values of RIP 20000 15000 10000 5000 00 070N040-1 Figure 3.2 RIP values of soil samples in different sites Sites Si and RIP in residence Si and RIP in farmland 20000 15000 10000 5000 00 y = 0.2362x + 676.77 R² = 088 0 200 400 600 800 12000 10000 8000 6000 4000 2000 00 y = 0.4392x + 871.66 R² = 0.1414 0 100 200 300 400 500 Figure 3.3.1 Relationship between Si and RIP in residence and farmland 142
Al and RIP in residence Al and RIP in farmland 20000 15000 y = 0.5822x + 704.26 R² = 25 12000 10000 8000 y = 0.9597x + 890.23 R² = 0.1568 10000 6000 5000 4000 2000 00 0 100 200 300 400 500 00 0 50 100 150 200 Figure 3.3.2 Relationship between Al and RIP in residence and farmland RIP frequency 25 20 1.2 1 15 10 5 frequency 0.8 0.6 0.4 0.2 0 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 其他 0 Figure 3.4 Histogram of values of RIP 143
200 150 100 50 C-RIP(1) 0 2.00 4.00 6.00 y = 206.6x + 391.6 R² = 0.81 C(%) 100 80 60 40 20 C-RIP(2) y = 24.393x + 620.56 R² = 0.9177 0 2.00 4.00 6.00 8.00 C(%) 60 40 C-RIP(3) y = 33.139x + 353.52 R² = 0.734 20 C(%) 0 2.00 4.00 6.00 Figure 3.5.1 Relationship between C and RIP N-RIP(1) 150 y = 515.17x + 884.84 R² = 0.8298 100 50 N(%) 0 0.50 1.00 100 80 60 40 20 N-RIP(2) y = 368.32x + 593.27 R² = 0.6081 N(%) 0 0.20 0.40 0.60 60 50 40 30 20 N-RIP(3) y = 211.39x + 404.52 R² = 0.5296 10 N(%) 0 0.20 0.40 0.60 Figure 3.5.2 Relationship between N and RIP 144
4 conclusion In land use types, the RIP of farmland, forest, grazing land are higher than RIP of resident region, there is no obvious relationship between Si and RIP,Al and RIP, and there are positive relationships between C and RIP,N and RIP in 3 chosen groups, the clarification of influnces of different clay minerals will be considered in future work. Reference 1. T. Kogure, K. Morimoto, k. Tamura, H. Sato and A. Yamagishi, XRD and HRTEM Evidences for fixation of Cesium Ions in Vermiculite Clay. Chemistry Letters. 2012. 41, 380-382. 2. Louis Vandebroek, May Van Hees, Bruno Delvaux, Otto Spaargaren, Yves Thiry, Relevance of Radiocaesium Interception Potential (RIP) on a worldwide scale to assess soil vulnerability to 137 Cs contamination. Journal of Environmental Radioactivity, 2012. 104, 87-93. 3. 中尾淳山口紀子放射性物質の土壌中での動き 2012 4. A. Cremers, A. Elsen, P. De preter and A. Maes, Quantitative-analysis of radiocesium retention in soils. Nature. 1988, 355, 247-249 5. J. Wauters, A. Elsen, A. Cremers, A. V. Konoplev, A. A. Bulgakov and R. N. J. Comans. Prediction of solid/liquid distribution coefficients of radiocaesium in soils and sediments. 1. A simplified procedure for the solid phase characterisation. Applied Geochemistry 1996, 11, 589-594 145