Evaluation of contribution rate of the infiltrated water collected using zero-tension lysimeter to the downward migration of 137Cs derived from the FDNPP accident in a cedar forest soil
Evaluation of contribution rate of the infiltrated water collected using zero-tension lysimeter to the downward migration of 137Cs derived from the FDNPP accident in a cedar forest soil
复制标题
零张力渗漏仪收集的渗透水对FDNPP事故中137Cs在雪松林土壤中向下迁移的贡献率评估
DOI：
10.1016/j.scitotenv.2021.151983
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发表时间：
2022
影响因子：
9.8
通讯作者：
Onda Yuichi
中科院分区：
文献类型：
--
作者：
Takahashi Junko;Hihara Daichi;Sasaki Takuya;Onda Yuichi
137 Cs在森林土壤中的垂直分布对于预测大气剂量率和森林生态系统未来循环具有重要意义。然而，关于其向下迁移的机制有许多无法解释的问题。在这项研究中，从2017年8月开始，使用零张力蒸渗仪在成熟的雪松林中观测了3年的降雨入渗137 Cs通量，自2011年以来一直在监测137 Cs的垂直分布。结果表明，凋落物层、5 cm和10 cm处入渗水中137 Cs浓度在夏季有较高的趋势，而20 cm处的浓度没有明显的季节变化。尽管凋落物层中137 Cs的储量呈指数下降趋势，但3年来凋落物层入渗水中137 Cs的年通量基本相同，约为137 Cs沉积密度的0.14-0.17%。将这些137 Cs通量与根据137 Cs垂直分布变化估算的137 Cs表观向下迁移量进行比较，计算出入渗水对137 Cs从枯落物向下迁移到土壤的贡献率为8.5- 17.7%。同样地，在实测基础上计算出矿质土层的贡献率为0.6-0.8%，在校正收集水量后估计为3.0 ± 0.2%，这是零张力蒸渗仪的问题。这表明降雨入渗可以解释一小部分137 Cs的向下迁移，因此需要进一步研究以阐明其余机制的贡献率，如对流扩散、胶体运输、物理混合、生物扰动和植物根系的生长和死亡。
The vertical distribution of137Cs in forest soil is important for predicting air dose rates and future cycling in forest ecosystems. However, there are many unexplained questions about the mechanisms of its downward migration. In this study, the137Cs flux by rainfall infiltration was observed for three years from August 2017 using zero-tension lysimeters in a mature cedar forest where monitoring of the vertical distribution of137Cs has been conducted since 2011. As a result, the137Cs concentration in infiltrated water through the litter layer, 5 cm and 10 cm showed a tendency to be high in summer, but no such seasonal variation was found at 20 cm. Although the137Cs inventory in the litter layer has been exponentially decreasing, the annual137Cs fluxes in infiltrated water through the litter layer were almost the same in three years, and about 0.14–0.17% of the deposition density of137Cs. Comparing these137Cs fluxes with the apparent amounts of downward migration of137Cs estimated from the change in the vertical distribution of137Cs, the contribution rate of the infiltrated water to downward migration of137Cs from litter to soil was calculated to be 8.5–17.7%. Similarly, the contribution rate in mineral soil layers was calculated to be 0.6–0.8% on a measured basis and estimated to be 3.0 ± 0.2% after correcting the amount of collected water, which is a problem with zero-tension lysimeter. It indicates that rainfall infiltration can explain a small part of the downward migration of137Cs, thus further studies are required to clarify the contribution rate of remaining mechanisms such as advection-diffusion, colloidal transport, physical mixing, bioturbation, and growth and death of plant roots.