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Yoshihara T, Kurita K, Matsumura H, Yoschenko V, Kawachi N, Hashida SN, Konoplev A, Yoshida H. Assessment of gamma radiation from a limited area of forest floor using a cumulative personal dosimeter. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 204:95-103. [PMID: 30991205 DOI: 10.1016/j.jenvrad.2019.03.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 03/22/2019] [Accepted: 03/22/2019] [Indexed: 06/09/2023]
Abstract
To elucidate long term changes in gamma radiation from a limited region of interest of the forest floor, a simple monitoring procedure using a cumulative personal dosimeter (D-shuttle) was examined from 2016 to 2017. The test site was in a small forest in Abiko, Japan, where the initial radiocesium contamination from the Fukushima Dai-ichi Nuclear Power Plant was 60-100 kBq m-2. Three experimental plots basically containing a set of two 5 × 5 m2 observation areas were arranged at the site. The litterfall and decomposing organic layer of one area (D: decontaminated) were fully eliminated before the monitoring, whereas the other area (N: natural) was left unchanged. Five D-shuttle sets (i.e., D-shuttle, lead shield, and holder) per area were set up. One D-shuttle set could monitor the specific gamma radiation from radiocesium distributed within a limited area of ground (0.5 m radius of circle = ca. 0.8 m2 area of flat ground). The results indicated significant differences in the accumulated doses among each of the plots and areas, reflecting their soil radiocesium inventories. Interestingly, every index decreased with time, but the decreases were slower than the theoretical decay of radiocesium (134Cs and 137Cs). In addition, the accumulated dose decreased during heavy rainfall events. One possible explanation for these changes of the accumulated dose is a combination of meteorological and tree phenological phenomena, such as radiocesium from the forest canopy being newly added to the floor primarily by litterfall and soil moisture content disturbing radiation emitted from soils. This simple procedure enables long-term observation of gamma radiation from a limited area of forest floor non-invasively and semi-quantitatively.
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Affiliation(s)
- Toshihiro Yoshihara
- Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Abiko, Chiba, 270-1194, Japan.
| | - Keisuke Kurita
- Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology (QST), 1233 Watanuki, Takasaki, Gunma, 370-1292, Japan
| | - Hideyuki Matsumura
- Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Abiko, Chiba, 270-1194, Japan
| | - Vasyl Yoschenko
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan
| | - Naoki Kawachi
- Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology (QST), 1233 Watanuki, Takasaki, Gunma, 370-1292, Japan
| | - Shin-Nosuke Hashida
- Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Abiko, Chiba, 270-1194, Japan
| | - Alexei Konoplev
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan
| | - Hirohisa Yoshida
- Urban Environmental Sciences, Tokyo Metropolitan University (TMU), 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
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