Honda Maki, Matsuzaki Hiroyuki, Miyake Yasuto, Maejima Yuji, Yamagata Takeyasu, Nagai Hisao
Graduate School of Integrated Basic Sciences, Nihon University, 3-25-40 Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan.
Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Environ Radioact. 2015 Aug;146:35-43. doi: 10.1016/j.jenvrad.2015.03.029. Epub 2015 Apr 22.
The (129)I derived from the FDNPP accident were clearly identified near the surface and showed a trend of rapid decrease with depth. The FDNPP (129)I and (137)Cs was 51.6 ± 1.7 mBq cm(-2) and 88.2 ± 27.1 kBq cm(-2) (average of four cores inventory) respectively. On average, 91% of the FDNPP (129)I existed within the top 5 g cm(-2) and 98% within the top 10 g cm(-2) and average of 100% of the FDNPP (137)Cs existed within the top 5 g cm(-2). From the observation of the temporal variation of depth profiles from the same upland field (Kawauchi village, 20 km away from the FDNPP to the southwest direction), downward migration rates of 0.81 ± 0.32 g cm(-2) yr(-1) for the FDNPP (129)I and 0.19 ± 0.17 g cm(-2) yr(-1) for the FDNPP (137)Cs were estimated. A simple diffusion model was introduced to evaluate the downward mobility of the FDNPP-derived (129)I and (137)Cs. The apparent diffusion coefficients D of 0.0086 ± 0.0034 and 0.0011 ± 0.0010 g(2) cm(-)(4) d(-)(1) were obtained for (129)I and (137)Cs, respectively. These values might be representative for Haplic Gray lowland soils in near the steady state under humid temperate climate.
福岛第一核电站事故产生的碘-129在地表附近被清晰识别，且呈现出随深度迅速下降的趋势。福岛第一核电站的碘-129和铯-137含量分别为51.6±1.7毫贝克勒尔/平方厘米和88.2±27.1千贝克勒尔/平方厘米（四个岩芯总量的平均值）。平均而言，福岛第一核电站91%的碘-129存在于顶部5克/平方厘米范围内，98%存在于顶部10克/平方厘米范围内，而福岛第一核电站100%的铯-137平均都存在于顶部5克/平方厘米范围内。通过对同一高地（位于福岛第一核电站西南方向20公里处的川内村）深度剖面的时间变化观察，估算出福岛第一核电站碘-129的向下迁移速率为0.81±0.32克/平方厘米·年，铯-137的向下迁移速率为0.19±0.17克/平方厘米·年。引入了一个简单的扩散模型来评估福岛第一核电站产生的碘-129和铯-137的向下迁移能力。碘-129和铯-137的表观扩散系数D分别为0.0086±0.0034和0.0011±0.0010克²/平方厘米⁻⁴·天⁻¹。这些数值可能代表了湿润温带气候下接近稳态的简育灰色低地土壤的情况。
