Institute of Environmental Radioactivity, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Fukushima, Japan.
Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba, Ibaraki, 305-8572, Japan.
Environ Pollut. 2020 Apr;259:113764. doi: 10.1016/j.envpol.2019.113764. Epub 2019 Dec 16.
Wildfires may play a role in redistributing radionuclides in the environment in combination with hydrological processes such as surface runoff and soil erosion. We investigated plot-scale radionuclide wash-off at forest sites affected by wildfires in the Chernobyl Exclusion Zone (CEZ). We also compared speciation of the washed-off radionuclides with those in previous studies conducted just after the accident in 1986. We observed the surface runoff and the radionuclide wash-off with a soil erosion plot at forest and post-fire sites during May-September 2018. In the post-fire site, 2.81 mm of surface runoff was observed in at least three flow events resulting from 285.8 mm total rainfall. The fluxes of dissolved and particulate Cs were estimated as 4.9 and 161 Bq m, respectively. The dissolved phase Sr flux was estimated as 214 Bq m. At the forest site, a single surface runoff (0.67 mm) event was generated by rainfall of 182.2 mm. The fluxes of dissolved and particulate Cs wash-off values were 6.2 and 8.6 Bq m, respectively. The flux of dissolved Sr wash-off from the forest was estimated as 45.1 Bq m. The distribution coefficient, which indicates the dissolved-particulate form of radionuclides, in the post-fire site was 30 times higher than that in the forest site, indicating the importance of particulate Cs wash-off after fire in the CEZ. The entrainment coefficients for dissolved and particulate Cs concentrations were around 50 times lower than those obtained in the corresponding position within the CEZ immediately after the accident in 1987. The effect of downward migration of Cs over 30 years led to decreased entrainment coefficients for dissolved and particulate Cs. The effect of downward migration of radionuclides was considered sufficient to indicate changes in normalized liquid and solid radionuclides wash-off entrainment coefficient and the distribution coefficient in this study.
野火可能与地表径流和土壤侵蚀等水文过程相结合，在环境中重新分配放射性核素。我们研究了切尔诺贝利隔离区（CEZ）受野火影响的森林地区的现场尺度放射性核素冲刷。我们还将冲刷下来的放射性核素的形态与 1986 年事故后进行的先前研究中的形态进行了比较。我们在 2018 年 5 月至 9 月期间，在森林和火灾后地点的土壤侵蚀场地上观察了地表径流和放射性核素冲刷。在火灾后地点，至少有三次地表径流事件，总降雨量为 285.8mm，总径流量为 2.81mm。溶解和颗粒态 Cs 的通量分别估计为 4.9 和 161 Bq m。Sr 的溶解相通量估计为 214 Bq m。在森林地点，总降雨量为 182.2mm，仅发生了一次地表径流（0.67mm）事件。溶解和颗粒态 Cs 的冲刷通量分别为 6.2 和 8.6 Bq m。从森林中冲刷出的溶解 Sr 通量估计为 45.1 Bq m。火灾后地点的分配系数（指示放射性核素的溶解-颗粒形式）比森林地点高 30 倍，表明火灾后 CEZ 中颗粒态 Cs 冲刷的重要性。溶解和颗粒态 Cs 浓度的夹带系数比 1987 年事故后同一地点的夹带系数低约 50 倍。Cs 向下迁移 30 多年，导致溶解和颗粒态 Cs 的夹带系数降低。考虑到放射性核素向下迁移的影响，足以表明本研究中归一化液体和固体放射性核素冲刷夹带系数和分配系数的变化。
