Fukushima Prefectural Centre for Environmental Creation, 10-2 Fukasaku, Miharu Town, Fukushima, 963-7700, Japan.
Fukushima Prefectural Centre for Environmental Creation, 10-2 Fukasaku, Miharu Town, Fukushima, 963-7700, Japan; Agricultural Radiation Research Center, Tohoku Agriculture Research Center, National Agriculture and Food Research Organization, 50 Harajukuminami, Arai, Fukushima City, Fukushima 960-2156, Japan.
J Environ Manage. 2023 Apr 15;332:117311. doi: 10.1016/j.jenvman.2023.117311. Epub 2023 Jan 30.
This study elucidated the impacts of typhoon events and remediation works on the spatiotemporal evolution of the air dose rate in riverside areas frequented by residents. Spatial distribution of the air dose rate and radiocesium concentration in the sediments were measured in two riverside parks located near each other in Fukushima Prefecture, Japan, for 2015-2020. The air dose rates measured by walk surveys were interpolated using ordinary kriging to generate air dose rate maps, to facilitate a comparison between the results at different points in time during the measurement campaigns. After the typhoons that occurred during 2015-2018, the air dose rate near the riverside in one park decreased, but not in the other, because the erosion and sediment deposition patterns differed between them. This could be due to the presence of a dam upstream, which serves a flood mitigation function. However, the extreme event of typhoon Hagibis in 2019 dropped the air dose rates near the riversides in both parks. In contrast to the typhoon events which affected the riverside areas, remediation works such as decontamination undertaken during 2015-2019 reduced the air dose rates around the garden and lawn areas which are frequently used as recreational sites. Modeling the temporal evolutions in the air dose rates for the entire area of the riverside parks revealed that 35% of the reduction was caused by physical decay of radiocesium on average, 14% by vertical migration of radiocesium in the soil through precipitation, and 51% by the three typhoons and remediation works during 2015-2019. The contribution of 20% from the strongest typhoon Hagibis highlights the fact that floods resulting from large typhoons are effective in causing natural attenuation of air dose rates in riverside parks.
本研究阐明了台风事件和整治工程对居民频繁光顾的河流沿岸地区空气剂量率时空演变的影响。在日本福岛县，两个临近的河边公园对空气剂量率和沉积物中放射性铯浓度进行了长达 2015-2020 年的测量。使用步行调查测量的空气剂量率通过普通克里金插值来生成空气剂量率图，以方便在测量期间的不同时间点之间进行结果比较。在 2015-2018 年发生的台风之后，一个公园河边的空气剂量率下降，但另一个公园的空气剂量率没有下降，因为它们的侵蚀和沉积模式不同。这可能是由于上游有一个大坝，起到了减轻洪水的作用。然而，2019 年的超强台风“哈吉比斯”却降低了两个公园河边的空气剂量率。与影响河流地区的台风事件不同，2015-2019 年期间进行的去污等整治工作降低了花园和草坪等经常用作娱乐场所的区域周围的空气剂量率。对河边公园整个区域的空气剂量率的时间演变进行建模表明，平均有 35%的减少是由于放射性铯的物理衰变造成的，14%是由于土壤中放射性铯通过降水的垂直迁移造成的，还有 51%是由于 2015-2019 年期间的三次台风和整治工作造成的。最强台风“哈吉比斯”贡献了 20%，这一事实突显了大型台风引发的洪水在导致河边公园空气剂量率自然衰减方面的有效性。
