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Spatial variation and radiocesium flux of litterfall in hardwood-pine mixed forest and cedar plantations based on long-term monitoring data. J Radioanal Nucl Chem 2020. [DOI: 10.1007/s10967-020-07433-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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2
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Translocation of cesium in the branches of Japanese cedar (Cryptomeria japonica) and Konara oak (Quercus serrata). J Radioanal Nucl Chem 2019. [DOI: 10.1007/s10967-019-06996-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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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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Yoshihara T, Yoschenko V, Watanabe K, Keitoku K. A through year behavior of 137Cs in a Japanese flowering cherry tree in relation to that of potassium. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 202:32-40. [PMID: 30776701 DOI: 10.1016/j.jenvrad.2019.01.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/09/2019] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
To understand the transfer of radiocesium (137Cs) in inside of deciduous trees, changes in 137Cs activity concentrations, primarily derived from the Fukushima accident in March 2011, were observed in the upper parts of a Japanese flowering cherry tree (Prunus x yedoensis cv. Somei-Yoshino) between 2015 and 2018. The sampling of the foliar parts occurred over the entire leaf life span from winter bud to litterfall and those of the branches were distinguished based on emergence years (2017, 2016, 2015, 2014-2011, and 2010/before). First, every tissue demonstrated a clear seasonal variation in 137Cs activity concentration. Second, a synchrony of seasonal variations in 137Cs activity concentration with those in the biological analogue of K concentration was observed in foliar parts during their growth season, but not in branches nor during the other seasons. With respect to the timing of changes in each tissue with tree phenology, it is possible that K and 137Cs alternate between leaves and branches via the same translocation mechanisms. The resorption efficiencies (i.e., 1 - [the concentrations in the last litterfall]/[the maximum concentrations in green leaves]) of K and 137Cs were 76% and 46% in average, respectively. In addition, both leaf buds and branches played an important role as reservoirs during dormancy. The buds storage ratio before and after bud burst (i.e., [the inventories in buds at the end of defoliation]/[those before and after bud burst]) for K were 0.57 and 0.10 in median, respectively, and those for and 137Cs were 1.14 and 0.14 in median, respectively. Consequently, the transfer of 137Cs in inside of trees was still visible seven years after deposition, even though the annual reduction in 137Cs activity concentration was apparent in each tissue.
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Affiliation(s)
- Toshihiro Yoshihara
- Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba, 270-1194, Japan.
| | - Vasyl Yoschenko
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan
| | - Kenji Watanabe
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan
| | - Koji Keitoku
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan; Minamisoma City Hall, Odaka Ward Community Promotion Division, 2-28 Moto-machi Odaka, Minami Soma, Fukushima, 979-2195, Japan
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Ayabe Y, Hijii N, Takenaka C. Effects of local-scale decontamination in a secondary forest contaminated after the Fukushima nuclear power plant accident. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 228:344-353. [PMID: 28551564 DOI: 10.1016/j.envpol.2017.05.041] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 05/11/2017] [Accepted: 05/17/2017] [Indexed: 06/07/2023]
Abstract
We investigated whether local-scale decontamination (removal of the litter layer, superficial soil layer, and understory) in a secondary forest contaminated by the Fukushima nuclear power plant accident reduced 137Cs contamination of the soil and litter. We also measured 137Cs concentrations in plants and in the web-building spider Nephila clavata (Nephilidae: Arachnida), as an indicator species, to examine 137Cs contamination in arthropods. One month after decontamination, the total 137Cs contamination (soil + litter) was reduced by 20% (100 kBq·m-2) relative to that in an adjacent untreated (i.e., contaminated) area, which was however not statistically significant. Four months after decontamination, 137Cs in the decontaminated area had increased to a level similar to those in the untreated area, and the air radiation dose in the decontaminated area was about 2.1 μSv·h-1, significantly higher than that in the untreated area (1.9 μSv·h-1). This may have been attributed to a torrential rain event. Although no statistically significant reduction was observed, most spiders had a lower 137Cs contamination than that before the decontamination. This implied that the decontamination may have reduced 137Cs transfer from soil via litter to N. clavata through the detrital food chains, but may not have reduced the amount of 137Cs transfer through grazing food chains because the concentration of 137Cs in living tree leaves was not reduced by the decontamination. In autumn, about 2 kBq·m-2 of 137Cs was supplied from foliage to the ground by litterfall. The results suggested that removal of the litter and superficial soil layers in a contaminated forest may be ineffective. The present study suggests that the local-scale decontamination in a secondary forest had no effect on the reduction of 137Cs contamination in the treated area.
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Affiliation(s)
- Yoshiko Ayabe
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Naoki Hijii
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Chisato Takenaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
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Yoshihara T, Matsumura H, Hashida SN, Nakaya K. Radiocesium contamination in living and dead foliar parts of Japanese cedar during 2011-2015. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 164:291-299. [PMID: 27537824 DOI: 10.1016/j.jenvrad.2016.08.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 07/27/2016] [Accepted: 08/07/2016] [Indexed: 06/06/2023]
Abstract
Radiocesium (137Cs) activity concentrations, mainly derived from the Fukushima accident of March 2011, were measured in green foliar parts without separation by age (bulk green foliar parts; GL) and litterfall (LF) of Japanese cedar (Cryptomeria japonica) from 2011 to 2015. In all samples, 137Cs concentrations decreased exponentially over time, but were always higher in LF (7.36-0.58 Bq g-DW-1) than in GL (2.10-0.06 Bq g-DW-1). The difference in the decreasing rate between GL and LF would reflect a difference in the dominant factor of the decrease between living and dead tissues (i.e., internal translocation and weathering, respectively). Over this same timeframe, potassium (K) concentrations in both GL and LF experienced repetitive periodical changes within a certain range (0.38-3.0 mg g-DW-1 for LF and 2.08-4.77 mg g-DW-1 for GL, respectively). Thus, there was no specific correlation between 137Cs and K concentrations in LF and GL. However, analyses of the age classified green foliar parts (GL-S) and dead foliar parts still retained on trees (DL) could indicate another view. The annual changes in residual rates of both 137Cs and K concentrations in GL-S demonstrated very similar two-phase reductions (i.e., a faster reduction in each expansion year than in the following years) and an obvious linear correlation between each other. Radiocesium concentration in DL were always higher than in any part of GL-S sampled at the same timing, but K concentrations showed the reverse relation. It is probable that 137Cs is basically translocated from older parts to the developing parts (as long as the former are alive) via a seasonal nutritional flow of K; however, a part of 137Cs translocation would cease considerably earlier than the cessation of K translocation.
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Affiliation(s)
- Toshihiro Yoshihara
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
| | - Hideyuki Matsumura
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Shin-Nosuke Hashida
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Ko Nakaya
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
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Hashida SN, Yoshihara T. Disparate radiocesium leaching from two woody species by acceleration of litter decomposition using microbial inoculation. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 162-163:319-327. [PMID: 27323212 DOI: 10.1016/j.jenvrad.2016.06.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 06/10/2016] [Accepted: 06/12/2016] [Indexed: 06/06/2023]
Abstract
Studies focusing on the migration of radionuclides in the forest floor have demonstrated that the ecological half-life of radiocesium on organic layer containing the debris of plant litter with various fungi and microorganisms is shorter than that in the deeper soil zone, suggesting that the litter decomposition affects radiocesium mobilization. Here, we showed the involvement of lignin, one of the major cell wall components of plant litter, in the fate of contaminated radiocesium during the process of fungal litter decomposition. In this study, litter decomposition of two different woody species, broadleaf deciduous Japanese cherry consisted of hardwood lignin and coniferous evergreen Japanese cedar with softwood lignin, were accelerated by in vitro fungal inoculation. In vitro inoculation exhibited 1.93- to 2.59-times faster decomposition than field experiment. Then, the cherry litter lost approximately 25% of initially contaminated radiocesium within 1 month of in vitro decomposition, whereas the cedar litter kept initial level at least for 6 month. The retention of radiocesium correlated with thioglycolate lignin content in cedar litter but not in cherry litter. Consequently, the behavior of radiocesium contaminated in litter fall may vary depending on the contamination pathway or the manner of nutrient mobilization at the stage of abscission between evergreen and deciduous trees.
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Affiliation(s)
- Shin-Nosuke Hashida
- Plant Molecular Biology, Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), Abiko 1646, Abiko-shi, Chiba, Japan.
| | - Toshihiro Yoshihara
- Plant Molecular Biology, Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), Abiko 1646, Abiko-shi, Chiba, Japan
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Evrard O, Laceby JP, Lepage H, Onda Y, Cerdan O, Ayrault S. Radiocesium transfer from hillslopes to the Pacific Ocean after the Fukushima Nuclear Power Plant accident: A review. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2015; 148:92-110. [PMID: 26142817 DOI: 10.1016/j.jenvrad.2015.06.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 06/11/2015] [Accepted: 06/22/2015] [Indexed: 06/04/2023]
Abstract
The devastating tsunami triggered by the Great East Japan Earthquake on March 11, 2011 inundated the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) resulting in a loss of cooling and a series of explosions releasing the largest quantity of radioactive material into the atmosphere since the Chernobyl nuclear accident. Although 80% of the radionuclides from this accidental release were transported over the Pacific Ocean, 20% were deposited over Japanese coastal catchments that are subject to frequent typhoons. Among the radioisotopes released during the FDNPP accident, radiocesium ((134)Cs and (137)Cs) is considered the most serious current and future health risk for the local population. The goal of this review is to synthesize research relevant to the transfer of FDNPP derived radiocesium from hillslopes to the Pacific Ocean. After radiocesium fallout deposition on vegetation and soils, the contamination may remain stored in forest canopies, in vegetative litter on the ground, or in the soil. Once radiocesium contacts soil, it is quickly and almost irreversibly bound to fine soil particles. The kinetic energy of raindrops instigates the displacement of soil particles, and their bound radiocesium, which may be mobilized and transported with overland flow. Soil erosion is one of the main processes transferring particle-bound radiocesium from hillslopes through rivers and streams, and ultimately to the Pacific Ocean. Accordingly this review will summarize results regarding the fundamental processes and dynamics that govern radiocesium transfer from hillslopes to the Pacific Ocean published in the literature within the first four years after the FDNPP accident. The majority of radiocesium is reported to be transported in the particulate fraction, attached to fine particles. The contribution of the dissolved fraction to radiocesium migration is only relevant in base flows and is hypothesized to decline over time. Owing to the hydro-meteorological context of the Fukushima region, the most significant transfer of particulate-bound radiocesium occurs during major rainfall and runoff events (e.g. typhoons and spring snowmelt). There may be radiocesium storage within catchments in forests, floodplains and even within hillslopes that may be remobilized and contaminate downstream areas, even areas that did not receive fallout or may have been decontaminated. Overall this review demonstrates that characterizing the different mechanisms and factors driving radiocesium transfer is important. In particular, the review determined that quantifying the remaining catchment radiocesium inventory allows for a relative comparison of radiocesium transfer research from hillslope to catchment scales. Further, owing to the variety of mechanisms and factors, a transdisciplinary approach is required involving geomorphologists, hydrologists, soil and forestry scientists, and mathematical modellers to comprehensively quantify radiocesium transfers and dynamics. Characterizing radiocesium transfers from hillslopes to the Pacific Ocean is necessary for ongoing decontamination and management interventions with the objective of reducing the gamma radiation exposure to the local population.
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Affiliation(s)
- Olivier Evrard
- Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Unité Mixte de Recherche 8212 (CEA-CNRS-UVSQ/IPSL), Gif-sur-Yvette, France.
| | - J Patrick Laceby
- Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Unité Mixte de Recherche 8212 (CEA-CNRS-UVSQ/IPSL), Gif-sur-Yvette, France
| | - Hugo Lepage
- Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Unité Mixte de Recherche 8212 (CEA-CNRS-UVSQ/IPSL), Gif-sur-Yvette, France
| | - Yuichi Onda
- Graduate School of Life and Environmental Sciences, Center for Research in Isotopes and Environmental Dynamics (CRIED), University of Tsukuba, Tsukuba, Japan
| | - Olivier Cerdan
- Bureau de Recherches Géologiques et Minières, Orléans, France
| | - Sophie Ayrault
- Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Unité Mixte de Recherche 8212 (CEA-CNRS-UVSQ/IPSL), Gif-sur-Yvette, France
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Nishikiori T, Watanabe M, Koshikawa MK, Takamatsu T, Ishii Y, Ito S, Takenaka A, Watanabe K, Hayashi S. Uptake and translocation of radiocesium in cedar leaves following the Fukushima nuclear accident. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 502:611-616. [PMID: 25302448 DOI: 10.1016/j.scitotenv.2014.09.063] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/19/2014] [Accepted: 09/19/2014] [Indexed: 06/04/2023]
Abstract
Cryptomeria japonica trees in the area surrounding Fukushima, Japan, intercepted (137)Cs present in atmospheric deposits soon after the Fukushima nuclear accident in March 2011. To study the uptake and translocation of (137)Cs in C. japonica leaves, we analyzed activity concentrations of (137)Cs and the concentration ratios of (137)Cs to (133)Cs ((137)Cs/(133)Cs) in old and new leaves of C. japonica collected from a forest on Mount Tsukuba between 9 and 15 months after the accident. Both isotopes were also analyzed in throughfall, bulk precipitation and soil extracts. Water of atmospheric and soil origin were used as proxies for deciphering the absorption from leaf surfaces and root systems, respectively. Results indicate that 20-40% of foliar (137)Cs existed inside the leaf, while 60-80% adhered to the leaf surface. The (137)Cs/(133)Cs ratios inside leaves that had sprouted before the accident were considerably higher than that of the soil extract and lower than that of throughfall and bulk precipitation. Additionally, more than 80% of (137)Cs in throughfall and bulk precipitation was present in the dissolved form, which is available for foliar uptake, indicating that a portion of the (137)Cs inside old leaves was presumably absorbed from the leaf surface. New leaves that sprouted after the accident had similar (137)Cs/(133)Cs ratios to that of the old leaves, suggesting that internal (137)Cs was translocated from old to new leaves. For 17 species of woody plants other than C. japonica, new leaves that sprouted after the accident also contained (137)Cs, and their (137)Cs/(133)Cs ratios were equal to or higher than that of the soil extract. These results suggested that foliar uptake and further translocation of (137)Cs is an important vector of contamination in various tree species during or just after radioactive fallout.
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Affiliation(s)
- Tatsuhiro Nishikiori
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Mirai Watanabe
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
| | - Masami K Koshikawa
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Takejiro Takamatsu
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Yumiko Ishii
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Shoko Ito
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Akio Takenaka
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Keiji Watanabe
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan; Center for Environmental Science in Saitama, 914 Kamitanadare, Kazo, Saitama 347-0115, Japan
| | - Seiji Hayashi
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
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Yoshihara T, Matsumura H, Tsuzaki M, Wakamatsu T, Kobayashi T, Hashida SN, Nagaoka T, Goto F. Changes in radiocesium contamination from Fukushima in foliar parts of 10 common tree species in Japan between 2011 and 2013. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 138:220-226. [PMID: 25261868 DOI: 10.1016/j.jenvrad.2014.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 08/26/2014] [Accepted: 09/03/2014] [Indexed: 06/03/2023]
Abstract
Yearly changes in radiocesium ((137)Cs) contamination, primarily due to the Fukushima accident of March 2011, were observed in the foliar parts of 10 common woody species in Japan (Chamaecyparis obtusa, Cedrus deodara, Pinus densiflora, Cryptomeria japonica, Phyllostachys pubescens, Cinnamomum camphora, Metasequoia glyptostroboides, Prunus × yedoensis, Acer buergerianum, and Aesculus hippocastanum). The samples were obtained from Abiko (approximately 200 km SSW of the Fukushima Dai-ichi Nuclear Power Plant) during each growing season between 2011 and 2013, and the foliar parts were examined based on their year of expansion and location in each trees. The radiocesium concentrations generally decreased with time; however, the concentrations and rates of decrease varied among species, age of foliar parts, and locations. The radiocesium concentrations in the 2012 current-year foliar parts were 29%-220% of those from 2011, while those from 2013 fell to between 14% and 42% of the 2011 values. The net decontamination in the foliage was higher in evergreen species than in deciduous species. The radiocesium concentrations in the upper foliar parts were higher than those in the lower parts particularly in C. japonica. In addition, the radiocesium concentrations were higher in the current-year foliar parts than in the 1-year-old foliar parts, particularly in 2013. Thus, the influence of the direct deposition of the fallout was reduced with time, and the translocation ability of radiocesium from old to new tissues became more influential. Similar to the behavior of potassium in trees, Cs redistribution probably occurred primarily due to internal nutrient translocation mechanisms.
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Affiliation(s)
- Toshihiro Yoshihara
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
| | - Hideyuki Matsumura
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Masaharu Tsuzaki
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Takashi Wakamatsu
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Takuya Kobayashi
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Shin-Nosuke Hashida
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Toru Nagaoka
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Fumiyuki Goto
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
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