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;724:138097. doi: 10.1016/j.scitotenv.2020.138097. Epub 2020 Mar 21.
We systematically investigated the sorption and fixation behaviors of radiocesium (Cs) for sediments taken from the rivers of Ukedo and Odaka around the Fukushima Daiichi Nuclear Power Plant. By comparing the Cs sorption and sequential desorption results at various Cs concentrations, across a range of sediment properties, we were able to understand the different contributions at frayed edge sites (FESs) and regular exchange sites (RESs) of the clay minerals, and their relationships with the Cs concentrations and the contents of organic matter (OM). The Cs sorption and fixation were dominated by FESs at trace Cs concentrations, and by ion exchange at RES and the collapse of interlayers at higher Cs concentrations. The Cs sorption at lower Cs concentration was strongly related to radiocesium interception potential (RIP); however, Cs fixation was more related to clay mineralogy (i.e. contents of mica, vermiculite and hydroxy-interlayered vermiculite) rather than the RIP. The first-order kinetic constants for time-dependent Cs sorption at low Cs concentrations were correlated negatively to the ratio between the total organic carbon and RIP values. This implies that Cs access to FESs requires a relatively long duration that is dependent on the contents of the OM. From these results, the sorption and fixation mechanisms were confirmed to be significantly different at different Cs concentrations. Then, the prediction of Cs transport should be based on the key mechanisms that are dominant at the actual trace levels of Cs. A significant difference between the Cs fixation behaviors at the Ukedo River and Odaka River may be understood by considering the differences in their clay mineralogy, due to the different geological settings and weathering stages of both catchments.
我们系统地研究了福岛第一核电站周边上野川和恩田川河流沉积物中放射性铯（Cs）的吸附和固定行为。通过比较不同 Cs 浓度下、一系列不同沉积物性质条件下的 Cs 吸附和顺序解吸结果，我们能够了解粘土矿物的边缘断裂位（FES）和常规交换位（RES）的不同贡献，以及它们与 Cs 浓度和有机质（OM）含量的关系。在痕量 Cs 浓度下，Cs 的吸附和固定主要受 FES 控制，而在较高 Cs 浓度下则受 RES 和夹层坍塌的离子交换控制。较低 Cs 浓度下的 Cs 吸附与放射性铯截留潜力（RIP）密切相关；然而，Cs 的固定则与粘土矿物学（即云母、蛭石和羟基间层蛭石的含量）的关系更为密切，而不是 RIP。低 Cs 浓度下，随时间变化的 Cs 吸附的一级动力学常数与总有机碳与 RIP 值之比呈负相关。这意味着 Cs 进入 FES 需要一个相对较长的时间，这取决于 OM 的含量。根据这些结果，可以证实不同 Cs 浓度下的吸附和固定机制有显著差异。因此，Cs 迁移的预测应基于在实际痕量 Cs 水平下占主导地位的关键机制。上野川和恩田川的 Cs 固定行为的显著差异，可以通过考虑到两个流域的粘土矿物学的差异来理解，这是由于其不同的地质背景和风化阶段造成的。
