Eight years post-Fukushima: is forest decontamination still necessary?
Eight years post-Fukushima: is forest decontamination still necessary?
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福岛核事故八年后：森林净化工作还有必要吗？
DOI：
10.1093/jrr/rrz047
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发表时间：
2019
期刊：
影响因子：
2
通讯作者：
Takamura N.
中科院分区：
文献类型：
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作者：
Taira Y;Inadomi Y;Hirajou S;Fukumoto Y;Orita M;Yamada Y;Takamura N.
福岛第一核电站(FDNPS)核事故已经过去了八年，该核电站由东京电力公司运营。各种放射性核素从FDNPS释放到大气中，最终沉积在陆地和周围地区的海上[1]。事故发生后，FDNPS周围疏散秩序区域内的居民区、农田、森林(靠近居民区)和道路通过适当的方法进行了广泛的净化，除难以返回区外，整个地区的净化工作已于2018年3月19日完成[2]。尽管居民区及其周围的辐射剂量正在减少，但据报道，森林地区积累了福岛县大气137Cs总输入的72%[3]。另据报道，在福岛核电站事故发生后不久，放射性铯在树木和森林环境中的土壤表层有机层中明显积累，但这种污染迅速减少，导致放射性在福岛核电站事故后的头两年转移到矿物土壤[4]。由于物理衰变(137Cs的半衰期较长)导致的放射性铯数量减少与其从矿物土壤上方的土壤表面有机层迁移之间的平衡，矿物土壤的放射性铯库存没有显著减少[4]。此外，由于风化过程和生态系统等多种因素，林区的空气沉积密度在不同城市之间表现出显著的差异[3]。福岛县约68%的地区被森林覆盖，在FDNPS事故发生前，居民经常通过徒步旅行等户外活动享受大自然的祝福[5]。因此，福岛居民希望从林业恢复和环境保护的角度进一步净化森林[6]。事实上，需要净化的森林面积非常大，需要巨额预算[2]。因此，从成本效益和优先事项的角度来看，需要进一步讨论森林净化政策[7]。在本研究中，我们使用步行测量系统(RadiProbe®；千代田技术公司，日本东京)和个人剂量计(D-Shuttle®；千代田技术公司)测量了环境剂量当量率(空气剂量率)，并分析了人造放射性核素(主要是放射性铯)的光谱。[8-10]评价福岛县林区辐射外照射剂量和环境污染量[8-10]。
Eight years have passed since the nuclear accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS), which is operated by the Tokyo Electric Power Company. Various radionuclides were released from the FDNPS into the atmosphere, eventually being deposited on land and at sea in the surrounding areas [1]. Following the accident, the residential areas, farmlands, forests (close to residential areas), and roads within the evacuation order areas around the FDNPS were extensively decontaminated by suitable methods, and decontamination of the entire area, excluding the difficult-to-return zones, was completed on 19 March 2018 [2]. Although radiation doses are decreasing in and around residential areas, it has been reported that forest areas accumulated 72% of the total atmospheric input of 137Cs in Fukushima Prefecture [3]. It has also been reported that radiocesium clearly accumulated in trees and the soil surface organic layer in the forest environment when the fallout occurred immediately after the FDNPS accident, but that this contamination decreased rapidly, resulting in a transfer of radioactivity to the mineral soil in the first 2 years after the FDNPS accident [4]. The mineral soil radiocesium inventory has not decreased significantly as a result of the balance between the decrease in the amount of radiocesium due to physical decay (longer half-life of 137Cs) and its migration from the soil surface organic layer above the mineral soil [4]. Moreover, the aerial deposition density in forest areas showed significant variability between municipalities because of multiple factors such as weathering processes and ecosystems [3]. Approximately 68% of Fukushima Prefecture is covered by forests, and residents frequently enjoyed the blessings of nature through outdoor activities such as hiking before the FDNPS accident [5]. Therefore, Fukushima residents desire further decontamination of forests from the perspective of forestry recovery and environmental preservation [6]. Actually, the forest area needing decontamination is extremely large and will require a huge budget [2]. Thus, from the perspective of cost-effectiveness and priorities, further discussions about forest decontamination policies are needed [7]. In the present study, we measured ambient dose equivalent rates (air dose rates) and analyzed the spectra of artificial radionuclides (mainly radiocesium) using a walking survey system (Radiprobe®; Chiyoda Technology Corp., Tokyo, Japan) and personal dosimeter (D-Shuttle®; Chiyoda Technology Corp.) to evaluate the contributory exposure doses to radiation (external exposure doses) and amount of environmental contamination in forest areas in Fukushima Prefecture [8–10].