Japan Atomic Energy Agency, 4-33 Muramatsu, Tokai, Ibaraki 319-1194, Japan.
Japan Atomic Energy Agency, 4-33 Muramatsu, Tokai, Ibaraki 319-1194, Japan.
Sci Total Environ. 2020 Jul 1;724:138098. doi: 10.1016/j.scitotenv.2020.138098. Epub 2020 Mar 21.
In order to elucidate the radiocesium transport behaviors in natural environment, we systematically investigated sediments from the highly contaminated rivers of Ukedo and Odaka around the Fukushima Daiichi Nuclear Power Plant. We focused on determining the key factors controlling the radiocesium sorption and fixation, such as variations in the particle size, clay mineralogy, and organic matter (OM). The distribution patterns of the Cs concentration and particle size fractions were found to be similar for the two rivers, indicating that both clay and silt fractions contributed almost equally to the Cs sorption. The clay mineralogical composition evaluated using X-ray diffraction analysis showed that the relative contents of micaceous minerals were higher in the Ukedo River samples, whereas the relative contents of smectite and kaolinite were higher in the Odaka River samples. This implies that the sediments in both rivers were likely at different weathering stages due to the different geological settings in both catchments. The effects of OM on the sediment properties were also investigated by comparing the cation exchange capacity (CEC) and the radiocesium interception potential (RIP) of the two samples both with and without OM present. The CEC values were controlled by both the clay minerals and OM, and the RIP values increased significantly in the absence of OM. Such trends were correlated to the total organic carbon values, which may be used to understand the direct and indirect roles of OM in the sorption and fixation of Cs. These key differences in river sediment were attributed to the differences in the geological settings and weathering stages. These properties may contribute to the different sorption and fixation behaviors of radiocesium. In the second part paper, we further examined these behaviors and identified key factors by investigating their relationship to the sediment properties of both rivers.
为了阐明天然环境中放射性铯的迁移行为，我们系统地研究了福岛第一核电站周围的乌居德河和网开户行这两条高度污染河流的沉积物。我们重点研究了控制放射性铯吸附和固定的关键因素，如粒径、粘土矿物和有机物（OM）的变化。这两条河的 Cs 浓度和粒径分布模式相似，表明粘土和粉土颗粒几乎对 Cs 吸附具有同等贡献。X 射线衍射分析评估的粘土矿物组成表明，乌居德河样品中云母类矿物的相对含量较高，而网开户行样品中蒙脱石和高岭石的相对含量较高。这意味着由于两个流域的地质背景不同，两条河流的沉积物可能处于不同的风化阶段。我们还通过比较两个样品中存在和不存在 OM 时的阳离子交换容量（CEC）和放射性铯截留潜力（RIP），研究了 OM 对沉积物性质的影响。CEC 值受到粘土矿物和 OM 的共同控制，而在没有 OM 的情况下，RIP 值显著增加。这些趋势与总有机碳值相关联，这可能有助于理解 OM 在 Cs 吸附和固定中的直接和间接作用。这些河流沉积物的关键差异归因于地质背景和风化阶段的差异。这些性质可能导致放射性铯的不同吸附和固定行为。在第二部分论文中，我们通过研究它们与两条河流沉积物性质的关系，进一步研究了这些行为并确定了关键因素。
