Koarashi Jun, Atarashi-Andoh Mariko, Nishimura Syusaku
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
Ecotoxicol Environ Saf. 2023 Jun 21;262:115177. doi: 10.1016/j.ecoenv.2023.115177.
Understanding the fate of the vertical distribution of radiocesium (Cs) in Japanese forest soils is key to assessing the radioecological consequences of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The Cs behavior in mineral soil is known to be primarily governed by interaction with clay minerals; however, some observations suggest the role of soil organic matter (SOM) in enhancing the mobility of Cs. Here we hypothesized that soil organic carbon (SOC) concentration profile determines the ultimate vertical pattern of Cs distribution in Japanese forest soils. In testing this hypothesis, we obtained soil samples that were collected before the FDNPP accident at four forest sites with varying SOC concentration profiles and quantified the detailed vertical profile of Cs inventory in the soils roughly half a century after global fallout in the early 1960 s. Results showed that the higher the SOC concentration in the soil profile, the deeper the Cs downward penetration. On the basis of the data for surface soils (0-10 cm), the Cs retention ratio for each of the 2-cm thick layers was evaluated as the ratio of Cs inventory in the target soil layer to the total Cs inventory in and below the soil layer. A negative correlation was found between the ratio and SOC concentration of the layer across all soils and depths. This indicates that the ultimate fate of Cs vertical distribution can be predicted as a function of SOC concentration for Japanese forest soils, and provides further evidence for SOM effects on the mobility and bioavailability of Cs in soils.
了解日本森林土壤中放射性铯（Cs）垂直分布的归宿是评估福岛第一核电站（FDNPP）事故放射性生态后果的关键。已知矿物土壤中铯的行为主要受与粘土矿物相互作用的控制；然而，一些观察结果表明土壤有机质（SOM）在增强铯的迁移性方面发挥了作用。在此，我们假设土壤有机碳（SOC）浓度剖面决定了日本森林土壤中铯分布的最终垂直模式。在验证这一假设时，我们获取了在FDNPP事故之前于四个具有不同SOC浓度剖面的森林地点采集的土壤样本，并对20世纪60年代初全球沉降大约半个世纪后土壤中铯存量的详细垂直剖面进行了量化。结果表明，土壤剖面中SOC浓度越高，铯向下渗透得越深。根据表层土壤（0 - 10厘米）的数据，将每个2厘米厚土层的铯保留率评估为目标土层中铯存量与该土层及其以下总铯存量的比率。在所有土壤和深度的该比率与土层的SOC浓度之间发现了负相关。这表明对于日本森林土壤，铯垂直分布的最终归宿可以作为SOC浓度的函数进行预测，并为SOM对土壤中铯的迁移性和生物有效性的影响提供了进一步的证据。
