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Takahashi J, Iguchi S, Sasaki T, Onda Y. Downward migration of 137Cs promotes self-cleaning of forest ecosystem by reducing root uptake of Japanese cedar in Fukushima. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 945:174010. [PMID: 38880141 DOI: 10.1016/j.scitotenv.2024.174010] [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: 03/15/2024] [Revised: 06/13/2024] [Accepted: 06/13/2024] [Indexed: 06/18/2024]
Abstract
Approximately 70 % of the area highly 137Cs-contaminated by the Fukushima Daiichi Nuclear Power Plant accident is forested. Decontamination works in most of these forests have not progressed, and the forestry industry remains stagnant. Although the long-term dynamics of 137Cs in the forest ecosystem will be controlled by the amount of 137Cs absorbed by roots in the future, temporal changes in 137Cs of tree roots have rarely been reported. In the present study, we monitored the depth distribution of 137Cs in the soil and absorptive very fine (VF) roots of 0.5 mm or less in a Japanese cedar forest from 2011 to 2023. As a result, the 137Cs inventory in the mineral soil increased over time due to the migration from the forest canopy and litter layers, whereas that in the VF roots tended to decrease since 2020, although there was a large variation. Temporal decrease in the exchangeable 137Cs fraction with fixation and temporal increase in VF root biomass with their growth were not clearly observed, the 137Cs concentration in the VF roots at 0-2 cm decreased with the decrease in 137Cs concentration in the litter layers. Although the 137Cs concentration in the VF roots below 2 cm tended to increase with increasing 137Cs concentration in the soil at the same depth, the downward migration of 137Cs within the soil can reduce the amount of 137Cs absorbed by roots because the VF root biomass decreases exponentially with depth. In other words, 137Cs can be removed from the long-term active cycles of forest ecosystems as they migrate deeper into the soil. This natural migration process can be regarded as a "self-cleaning" of the forest ecosystem, the green and sustainable remediation using such self-cleaning should be actively adopted for the future forest management.
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Affiliation(s)
- Junko Takahashi
- Center for Research in Radiation, Isotopes, and Earth System Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
| | - Satoshi Iguchi
- Master's Program in Geosciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
| | - Takuya Sasaki
- College of Geoscience, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
| | - Yuichi Onda
- Center for Research in Radiation, Isotopes, and Earth System Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
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Jo J, Ishii Y, Saito R, Tanaka A, Hayashi S. Evaluation of bioavailable 137Cs transfer from forest litter to Scarabaeidae beetle (Protaetia orientalis) through a breeding experiment in Fukuhshima. PLoS One 2024; 19:e0310088. [PMID: 39240953 PMCID: PMC11379175 DOI: 10.1371/journal.pone.0310088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 08/24/2024] [Indexed: 09/08/2024] Open
Abstract
Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, most of the released 137Cs remained in the litter and surface soil of the adjacent forest floor. However, 137Cs absorption by large soil invertebrates near this site has not been estimated. The aim of this study was to understand the role of soil macroinvertebrates in 137Cs uptake from forest litter into forest ecosystems. Breeding experiments were conducted using scarab beetle larvae (Protaetia orientalis). Dissection experiments revealed that 85% of the total 137Cs was concentrated in the digestive tract of larvae, while a low proportion was absorbed into the skin and muscle tissues. The 137Cs absorption rate, indicating the transfer of 137Cs from consumed litter to larval tissue, was low (0.39%). 137Cs concentrations decreased to one-fourth from larva to imago, possibly due to excretion from the digestive tract and during eclosion. In the elimination experiment, biological half-lives were 0.26-0.64 and 0.11-0.47 days and 3.35-48.30 and 4.01-17.70 days for the digestive tract and muscle/skin tissues in the fast and slow components, respectively, corresponding to 137Cs discharge from the gastrointestinal tract and physiological clearance. In the sequential extraction experiment, litter digestion by flower chafer larvae significantly reduced the bioavailable fraction of 137Cs including water-soluble, exchangeable, oxidized, and organic forms, from 23.2% in litter to 17.7% in feces. Residual 137Cs was not reduced by digestion, probably because it was fixed in soil clay. Our study on breeding experiments of the Scarabaeidae beetle confirmed the low bioavailability of 137Cs in the litter in Fukushima. However, litter feeders may play an important role in transferring 137Cs to higher trophic levels in the forest ecosystem by extracting the bioavailable fraction of the vast stock of 137Cs on the forest floor.
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Affiliation(s)
- Jaeick Jo
- Environmental Impact Assessment Section, Fukushima Branch, National Institute for Environmental Studies, Miharu, Fukushima, Japan
| | - Yumiko Ishii
- Environmental Impact Assessment Section, Fukushima Branch, National Institute for Environmental Studies, Miharu, Fukushima, Japan
| | - Rie Saito
- Environmental Impact Assessment Section, Fukushima Branch, National Institute for Environmental Studies, Miharu, Fukushima, Japan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, United States of America
- Department of Animal Science, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
| | - Asuka Tanaka
- Environmental Impact Assessment Section, Fukushima Branch, National Institute for Environmental Studies, Miharu, Fukushima, Japan
| | - Seiji Hayashi
- Environmental Impact Assessment Section, Fukushima Branch, National Institute for Environmental Studies, Miharu, Fukushima, Japan
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Manaka T, Araki MG, Ohashi S, Imamura N, Sakashita W, Ogo S, Komatsu M, Sakata T, Shinomiya Y. Radiocesium mobility in different parts of the two major tree species in Fukushima. Sci Rep 2023; 13:9144. [PMID: 37277410 DOI: 10.1038/s41598-023-35852-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 05/24/2023] [Indexed: 06/07/2023] Open
Abstract
Radiocesium (137Cs) released in the Fukushima Dai-ichi Nuclear Power Plant accident is still cycling in the forest ecosystem. We examined the mobility of 137Cs in the external parts-leaves/needles, branches, and bark-of the two major tree species in Fukushima, Japanese cedar (Cryptomeria japonica) and konara oak (Quercus serrata). This variable mobility will likely lead to spatial heterogeneity of 137Cs and difficulty in predicting its dynamics for decades. We conducted leaching experiments on these samples by using ultrapure water and ammonium acetate. In Japanese cedar, the 137Cs percentage leached from current-year needles was 26-45% (ultrapure water) and 27-60% (ammonium acetate)-similar to those from old needles and branches. In konara oak, the 137Cs percentage leached from leaves was 47-72% (ultrapure water) and 70-100% (ammonium acetate)-comparable to those from current-year and old branches. Relatively poor 137Cs mobility was observed in the outer bark of Japanese cedar and in organic layer samples from both species. Comparison of the results from corresponding parts revealed greater 137Cs mobility in konara oak than in Japanese cedar. We suggest that more active cycling of 137Cs occurs in konara oak.
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Affiliation(s)
- Takuya Manaka
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan.
| | - Masatake G Araki
- Extension and Protection Division, Private Forest Department, Forestry Agency, Chiyoda, Tokyo, 100-8952, Japan
| | - Shinta Ohashi
- Department of Wood Properties and Processing, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Naohiro Imamura
- Hokkaido Research Center, FFPRI, Sapporo, Hokkaido, 062-8516, Japan
| | - Wataru Sakashita
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Sumika Ogo
- Department of Mushroom Science and Forest Microbiology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Masabumi Komatsu
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
- Department of Mushroom Science and Forest Microbiology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Tadashi Sakata
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Yoshiki Shinomiya
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
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Yoschenko V, Nanba K, Wada T, Johnson TE, Zhang J, Workman D, Nagata H. Late phase radiocesium dynamics in Fukushima forests post deposition. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 251-252:106947. [PMID: 35732077 DOI: 10.1016/j.jenvrad.2022.106947] [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: 02/13/2022] [Revised: 06/14/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
The long term dynamics of radiocesium in typical forest ecosystems was studied in the radioactive contaminated areas in Fukushima Prefecture. Six observations sites located in Yamakiya Village (Kawamata Town; since 2014), Tsushima Village (Namie Town, since 2015), and Tomioka Town (since 2017) were monitored. The forests consisted of artificial plantations of Japanese cedar (Cryptomeria japonica) at Yamakiya Village, Tsushima Village, and Tomioka Town. Tsushima Village also had a natural mixed forest dominated by Japanese red pine (Pinus densiflora), and Tomioka Town had a young and a mature artificial plantation of Japanese cypress (Chamaecyparis obtuse). Concentrations of 137Cs were monitored in the samples collected from the main aboveground biomass compartments, fresh litterfall, forest litter, and soil. Concentrations of exchangeable forms of 137Cs and stable K were measured in soil samples. During the observation period, the litter radiocesium inventories at all sites decreased significantly to approximately 1% or less of the total ground deposition. Approximately 80% of the total radiocesium inventory is localized in the upper 5-cm layer of soil and there is little downward migration of radiocesium. At the sites with the longest monitoring series (Yamakiya and Tsushima), the radiocesium expectation depths and expectation mass depths were relatively constant at 2-3 cm and 5-6 kg m-2, respectively. Aboveground biomass compartments showed similar decreasing trends in radiocesium aggregated transfer factors, Tag, in the compartments that were exposed to atmospheric fallout in March 2011 (old foliage, small branches, and outer bark). The mean Tag in cedar stand compartments currently are in the range of 10-3-10-2 m2 kg-1 dw. However, the mean Tag and their dynamic trend significantly differed in the wood compartments of the cedar stands, which may indicate root uptake differences of orders of magnitude between observation sites. The difference in radiocesium concentration in wood between the sites becomes less pronounced when normalized by the ratio of exchangeable 137Cs/K in the soils.
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Affiliation(s)
- Vasyl Yoschenko
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan.
| | - Kenji Nanba
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Toshihiro Wada
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Thomas E Johnson
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, United States
| | - Jian Zhang
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, United States
| | - Daniel Workman
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, United States
| | - Hiroko Nagata
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
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Manaka T, Komatsu M, Sakashita W, Imamura N, Hashimoto S, Hirai K, Miura S, Kaneko S, Sakata T, Shinomiya Y. Ten-year trends in vertical distribution of radiocesium in Fukushima forest soils, Japan. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 251-252:106967. [PMID: 35930867 DOI: 10.1016/j.jenvrad.2022.106967] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 07/08/2022] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
To elucidate interannual changes in the vertical distribution of 137Cs in forest ecosystems contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident, we investigated 137Cs inventories in forest soils (both organic and mineral soil horizons) at 10 sampling plots with different 137Cs deposition levels and dominant species for up to 10 years after the accident. We examined the temporal variation of the 137Cs inventories by depth with exponential regression models (assuming that the transition and partitioning of 137Cs are still active) and exponential offset regression models (assuming a shift to a stable 137Cs distribution, defined as the "quasi-equilibrium steady-state" in the Chernobyl accident). In the organic horizon, the 137Cs inventories were exponentially decreasing, and it might take more time to converge in the quasi-equilibrium steady-state at most plots. In the mineral soil horizon, most of 137Cs was found in the surface layer of the mineral soil horizon (0-5 cm). In this layer, the inventories first increased and then become relatively constant, and the exponential offset model was selected at most plots, suggesting entry into the quasi-equilibrium steady-state over the observation period. Although we also observed exponentially increasing trends in a lower layer (5-10 cm) of the mineral soil horizon, there was no clear increasing or decreasing trend of 137Cs inventory in the deeper mineral soil layers (10-15 and 15-20 cm). Our calculation of the relaxation depth and migration center revealed that downward migration of 137Cs is not significant in terms of the overall 137Cs distribution in the mineral soil horizon over 10 years.
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Affiliation(s)
- Takuya Manaka
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan.
| | - Masabumi Komatsu
- Department of Mushroom Science and Forest Microbiology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan; Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Wataru Sakashita
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan; Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Naohiro Imamura
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan
| | - Shoji Hashimoto
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan
| | - Keizo Hirai
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan
| | - Satoru Miura
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Shinji Kaneko
- Kansai Research Center, FFPRI, Kyoto, Kyoto, 612-0855, Japan
| | - Tadashi Sakata
- Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan; Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
| | - Yoshiki Shinomiya
- Center for Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, 305-8687, Japan
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De Marco A, Sicard P, Feng Z, Agathokleous E, Alonso R, Araminiene V, Augustatis A, Badea O, Beasley JC, Branquinho C, Bruckman VJ, Collalti A, David‐Schwartz R, Domingos M, Du E, Garcia Gomez H, Hashimoto S, Hoshika Y, Jakovljevic T, McNulty S, Oksanen E, Omidi Khaniabadi Y, Prescher A, Saitanis CJ, Sase H, Schmitz A, Voigt G, Watanabe M, Wood MD, Kozlov MV, Paoletti E. Strategic roadmap to assess forest vulnerability under air pollution and climate change. GLOBAL CHANGE BIOLOGY 2022; 28:5062-5085. [PMID: 35642454 PMCID: PMC9541114 DOI: 10.1111/gcb.16278] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 03/02/2022] [Accepted: 05/18/2022] [Indexed: 05/13/2023]
Abstract
Although it is an integral part of global change, most of the research addressing the effects of climate change on forests have overlooked the role of environmental pollution. Similarly, most studies investigating the effects of air pollutants on forests have generally neglected the impacts of climate change. We review the current knowledge on combined air pollution and climate change effects on global forest ecosystems and identify several key research priorities as a roadmap for the future. Specifically, we recommend (1) the establishment of much denser array of monitoring sites, particularly in the South Hemisphere; (2) further integration of ground and satellite monitoring; (3) generation of flux-based standards and critical levels taking into account the sensitivity of dominant forest tree species; (4) long-term monitoring of N, S, P cycles and base cations deposition together at global scale; (5) intensification of experimental studies, addressing the combined effects of different abiotic factors on forests by assuring a better representation of taxonomic and functional diversity across the ~73,000 tree species on Earth; (6) more experimental focus on phenomics and genomics; (7) improved knowledge on key processes regulating the dynamics of radionuclides in forest systems; and (8) development of models integrating air pollution and climate change data from long-term monitoring programs.
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Affiliation(s)
| | | | - Zhaozhong Feng
- Key Laboratory of Agro‐Meteorology of Jiangsu Province, School of Applied MeteorologyNanjing University of Information Science & TechnologyNanjingChina
| | - Evgenios Agathokleous
- Key Laboratory of Agro‐Meteorology of Jiangsu Province, School of Applied MeteorologyNanjing University of Information Science & TechnologyNanjingChina
| | - Rocio Alonso
- Ecotoxicology of Air Pollution, CIEMATMadridSpain
| | - Valda Araminiene
- Lithuanian Research Centre for Agriculture and ForestryKaunasLithuania
| | - Algirdas Augustatis
- Faculty of Forest Sciences and EcologyVytautas Magnus UniversityKaunasLithuania
| | - Ovidiu Badea
- “Marin Drăcea” National Institute for Research and Development in ForestryVoluntariRomania
- Faculty of Silviculture and Forest Engineering“Transilvania” UniversityBraşovRomania
| | - James C. Beasley
- Savannah River Ecology Laboratory and Warnell School of Forestry and Natural ResourcesUniversity of GeorgiaAikenSouth CarolinaUSA
| | - Cristina Branquinho
- Centre for Ecology, Evolution and Environmental Changes, Faculdade de CiênciasUniversidade de LisboaLisbonPortugal
| | - Viktor J. Bruckman
- Commission for Interdisciplinary Ecological StudiesAustrian Academy of SciencesViennaAustria
| | | | | | - Marisa Domingos
- Instituto de BotanicaNucleo de Pesquisa em EcologiaSao PauloBrazil
| | - Enzai Du
- Faculty of Geographical ScienceBeijing Normal UniversityBeijingChina
| | | | - Shoji Hashimoto
- Department of Forest SoilsForestry and Forest Products Research InstituteTsukubaJapan
| | | | | | | | - Elina Oksanen
- Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland
| | - Yusef Omidi Khaniabadi
- Department of Environmental Health EngineeringIndustrial Medial and Health, Petroleum Industry Health Organization (PIHO)AhvazIran
| | | | - Costas J. Saitanis
- Lab of Ecology and Environmental ScienceAgricultural University of AthensAthensGreece
| | - Hiroyuki Sase
- Ecological Impact Research DepartmentAsia Center for Air Pollution Research (ACAP)NiigataJapan
| | - Andreas Schmitz
- State Agency for Nature, Environment and Consumer Protection of North Rhine‐WestphaliaRecklinghausenGermany
| | | | - Makoto Watanabe
- Institute of AgricultureTokyo University of Agriculture and Technology (TUAT)FuchuJapan
| | - Michael D. Wood
- School of Science, Engineering and EnvironmentUniversity of SalfordSalfordUK
| | | | - Elena Paoletti
- Department of Forest SoilsForestry and Forest Products Research InstituteTsukubaJapan
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Li P, Gong Y, Lu W, Sakagami N, Mo Z, Komatsuzaki M. Radiocesium distribution caused by tillage inversion affects the soil-to-crop transfer factor and translocation in agroecosystems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 831:154897. [PMID: 35367255 DOI: 10.1016/j.scitotenv.2022.154897] [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: 01/31/2022] [Revised: 03/23/2022] [Accepted: 03/25/2022] [Indexed: 06/14/2023]
Abstract
This study reports the translocation of cesium-137 (137Cs) into deep soil layers, and the 137Cs transfer from soil to soybean in farmland under three tillage (no tillage, NT; rotary cultivation, RC; moldboard plow; MP) treatments and an undisturbed grassland (GL) at eight years after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on 11 March 2011 in Japan. Tillage influences the 137Cs distribution in the 0-30 cm of soil; the distribution of 137Cs in the soil was uniform under RC and MP treatments, while in the grassland, most 137Cs was concentrated on the soil surface (0-2.5 cm). The center of vertical 137Cs radioactivity concentration (the thickness of the soil from surface which containing half of the 137Cs inventory) in GL was 5.5 cm, which was shallower than that in farmland (9.5 cm in NT, 13.6 cm in RC and 15.2 cm in MP). Hence, the total translocation distance of 137Cs 8 years after FDNPP accident showed the following trend: GL (2.4 cm) < NT (7.0 cm) < RC (10.0 cm) < MP (12.3 cm). Meanwhile, a significant positive correlation was observed between 137Cs radioactivity concentration and organic carbon and nitrogen content in the soil. However, the 137Cs radioactivity concentration in soybean grains was negatively correlated with the center of vertical 137Cs radioactivity concentration but positively correlated with the ratio of exchangeable 137Cs (ExCs) and K content in the soil. The ExCs/K and 137Cs distributions in the soil were combined into a statistical model to predict the 137Cs radioactivity concentration in soybean grain. The results revealed the magnitude of the impact of 137Cs distribution on the 137Cs transfer from soil to crop. The addition of the 137Cs distribution dramatically improved the accuracy of the prediction model of 137Cs radioactivity concentration in soybean.
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Affiliation(s)
- Peiran Li
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo 183-8509, Japan
| | - Yingting Gong
- Institute of Agricultural Resources and Environment, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China
| | - Wenyi Lu
- College of Agriculture, Ibaraki University, 3-21-1, Chuuo, Ami, Inashiki, Ibaraki 300-0393, Japan
| | - Nobuo Sakagami
- College of Agriculture, Ibaraki University, 3-21-1, Chuuo, Ami, Inashiki, Ibaraki 300-0393, Japan
| | - Zhaowen Mo
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Agriculture, South China Agricultural University, Guangzhou 510642, China
| | - Masakazu Komatsuzaki
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo 183-8509, Japan; Center for International Field Agriculture Research & Education, Ibaraki University, 3-21-1, Ami, Inashiki, Ibaraki 300-0393, Japan.
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8
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Ohashi S, Kuroda K, Abe H, Kagawa A, Komatsu M, Sugiyama M, Suzuki Y, Fujiwara T, Takano T. Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident. Sci Rep 2022; 12:11243. [PMID: 35788621 PMCID: PMC9253084 DOI: 10.1038/s41598-022-14576-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 06/09/2022] [Indexed: 11/13/2022] Open
Abstract
Understanding the actual situation of radiocesium (137Cs) contamination of trees caused by the Fukushima nuclear accident is essential for predicting the future contamination of wood. Particularly important is determining whether the 137Cs dynamics within forests and trees have reached apparent steady state. We conducted a monitoring survey of four major tree species (Japanese cedar, Japanese cypress, konara oak, and Japanese red pine) at multiple sites. Using a dynamic linear model, we analyzed the temporal trends in 137Cs activity concentrations in the bark (whole), outer bark, inner bark, wood (whole), sapwood, and heartwood during the 2011-2020 period. The activity concentrations were decay-corrected to September 1, 2020, to exclude the decrease due to the radioactive decay. The 137Cs concentrations in the whole and outer bark samples showed an exponential decrease in most plots but a flat trend in one plot, where 137Cs root uptake is considered to be high. The 137Cs concentration ratio (CR) of inner bark/sapwood showed a flat trend but the CR of heartwood/sapwood increased in many plots, indicating that the 137Cs dynamics reached apparent steady state within one year in the biologically active parts (inner bark and sapwood) and after several to more than 10 years in the inactive part (heartwood). The 137Cs concentration in the whole wood showed an increasing trend in six plots. In four of these plots, the increasing trend shifted to a flat or decreasing trend. Overall, the results show that the 137Cs dynamics within forests and trees have reached apparent steady state in many plots, although the amount of 137Cs root uptake in some plots is possibly still increasing 10 years after the accident. Clarifying the mechanisms and key factors determining the amount of 137Cs root uptake will be crucial for predicting wood contamination.
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Affiliation(s)
- Shinta Ohashi
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan.
| | - Katsushi Kuroda
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Hisashi Abe
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Akira Kagawa
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Masabumi Komatsu
- Department of Mushroom Science and Forest Microbiology, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Masaki Sugiyama
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Youki Suzuki
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Takeshi Fujiwara
- Hokkaido Research Center, FFPRI, 7 Hitsujigaoka, Toyohira, Sapporo , Hokkaido, 062-8516, Japan
| | - Tsutomu Takano
- Center for Forest Restoration and Radioecology, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
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Ota M, Koarashi J. Contamination processes of tree components in Japanese forest ecosystems affected by the Fukushima Daiichi Nuclear Power Plant accident 137Cs fallout. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 816:151587. [PMID: 34838924 DOI: 10.1016/j.scitotenv.2021.151587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 10/30/2021] [Accepted: 11/06/2021] [Indexed: 06/13/2023]
Abstract
In forests affected by the Fukushima Daiichi Nuclear Power Plant accident, trees became contaminated with 137Cs. However, 137Cs transfer processes determining tree contamination (particularly for stem wood, a prominent commercial resource) remain insufficiently understood. We propose a model for simulating dynamic behavior of 137Cs in a forest tree-litter-soil system and applied it to contaminated forests of cedar plantation and natural oak stand in Fukushima to elucidate relative impact of distinct 137Cs transfer processes determining the tree contamination. The transfer of 137Cs to the trees occurred mostly (>99%) through surface uptake of 137Cs trapped by needles and bark during the fallout. Root uptake of soil 137Cs was several orders of magnitude lower than the surface uptake over a 50-year period following the accident. As a result, internal contamination of the trees proceeded through an enduring recycling (translocation) of 137Cs absorbed on the tree surface. A significant surface uptake of 137Cs through bark was suggested, contributing to 100% (leafless oak tree) and 30% (foliated cedar tree; the remaining uptake occurred at needles) of the total uptake by the trees, although that pathway still needs to be evaluated by experimental evidence. It was suggested that the activity concentration of 137Cs in stem wood of the trees at these sites are currently (as of 2021) decreasing by ~3% per year, mainly through radioactive decay of 137Cs and partly through dilution effect from tree growth. Although further refinement of the model is recommended, for example by including tree species specific 137Cs transportation in stem, these findings provide vital information for planning of forestry reactivation in Fukushima; e.g., removal of forest floor organic layer will not reduce the tree contamination for a long term because of the 137Cs absorption via the tree surface substantially greater than root uptake of 137Cs deposited to the floor.
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Affiliation(s)
- Masakazu Ota
- Research Group for Environmental Science, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Ibaraki 319-1195, Japan.
| | - Jun Koarashi
- Research Group for Environmental Science, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Ibaraki 319-1195, Japan
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10
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Komatsu M, Hashimoto S, Matsuura T. Effects of species and geo-information on the 137Cs concentrations in edible wild mushrooms and plants collected by residents after the Fukushima nuclear accident. Sci Rep 2021; 11:22470. [PMID: 34789824 PMCID: PMC8599460 DOI: 10.1038/s41598-021-01816-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 11/03/2021] [Indexed: 11/16/2022] Open
Abstract
After the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP), much of the wild and edible mushrooms and plants in the surrounding areas were contaminated with radiocesium (137Cs). To elucidate their concentration characteristics, we analyzed 137Cs radioactivity data in edible forest products brought in for food inspection by the residents of Kawauchi Village, 12-30 km away from the FDNPP, from 2012 to 2019. A Bayesian model to estimate 137Cs concentration was constructed. Parameters of the normalized concentration of species (NCsp) for mushrooms were similar to those of the same species obtained in a previous study. Although NCsp values were highly varied among species, mycorrhizal mushrooms tended to have high NCsp values, followed by saprotrophic mushrooms, and wild edible plants values were low. Also, half of mycorrhizal mushroom species (8 of 16) showed an increasing trend in concentration with time; however, saprotrophic mushrooms and wild plants generally demonstrated a decreasing trend (22 of 24). The model considering the sub-village location information decreased the error of individual samples by 40% compared to the model not considering any location information, indicating that the detailed geo-information improved estimation accuracy. Our results indicate that the radioactivity data from samples collected by local residents can be used to accurately assess internal exposure to radiation due to self-consumption of contaminated wild mushrooms and plants.
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Affiliation(s)
- Masabumi Komatsu
- Department of Mushroom Science and Forest Microbiology, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan.
| | - Shoji Hashimoto
- Department of Forest Soils, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan
| | - Toshiya Matsuura
- Tohoku Research Center, Forestry and Forest Products Research Institute, Morioka, Iwate, 020-0123, Japan
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11
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Chaif H, Coppin F, Bahi A, Garcia-Sanchez L. Influence of non-equilibrium sorption on the vertical migration of 137Cs in forest mineral soils of Fukushima Prefecture. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 232:106567. [PMID: 33689934 DOI: 10.1016/j.jenvrad.2021.106567] [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: 11/06/2020] [Revised: 02/12/2021] [Accepted: 02/21/2021] [Indexed: 06/12/2023]
Abstract
Sorption hypotheses and models are required for the prediction of 137Cs migration in soils contaminated after nuclear reactor accidents and nuclear weapons tests. In assessment models, the Kd (distribution coefficient) hypothesis for sorption, which assumes that sorption is instantaneous, linear and reversible, has often been coupled with the convection-diffusion equation (CDE) to model 137Cs migration. However, it fails to describe 137Cs migration velocities which often decrease with time. Alternative equilibrium-kinetic (EK) hypotheses of 137Cs sorption/desorption have been suggested by laboratory experiments but have not been fully validated in field conditions. This work addressed the influence and magnitude of non-equilibrium 137Cs sorption in field conditions by reinterpreting, with an inverse approach, series of 137Cs profiles measured in mineral soils of forest plots located in Fukushima Prefecture (2013-2018). Our results show that the inclusion of non-equilibrium sorption significantly improves, compared to the equilibrium hypothesis, the realism of simulated 137Cs profiles. Fitted sorption parameters suggest a fast sorption kinetic (half-time of 1-7 h) and a pseudo-irreversible desorption rate (half-time of 3.2 × 100-3.4 × 106 years), whereas equilibrium sorption (4.0 × 10-3 L kg-1 on average) only affects a negligible portion of 137Cs inventory. By June 2011, such EK parameters fitted on our plots realistically reproduced profiles measured in the same forest study site (Takahashi et al., 2015). Predictive modeling of 137Cs profiles in soil suggests a strong persistence of the surface 137Cs contamination by 2030, with exponential profiles consistent with those reported after the Chernobyl accident. This study demonstrates that hypotheses and parameters of 137Cs sorption can be partially inferred from in situ measurements. However, further experiments in controlled conditions are required to better estimate the sorption parameters and to identify the processes behind non-equilibrium sorption.
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Affiliation(s)
- Hamza Chaif
- Institute of Radiological Protection and Nuclear Safety (IRSN), PSE-ENV, SRTE, LR2T, CE Cadarache, 13115, Saint Paul les Durance Cedex, France.
| | - Frédéric Coppin
- Institute of Radiological Protection and Nuclear Safety (IRSN), PSE-ENV, SRTE, LR2T, CE Cadarache, 13115, Saint Paul les Durance Cedex, France.
| | - Aya Bahi
- Institute of Radiological Protection and Nuclear Safety (IRSN), PSE-ENV, SRTE, LR2T, CE Cadarache, 13115, Saint Paul les Durance Cedex, France.
| | - Laurent Garcia-Sanchez
- Institute of Radiological Protection and Nuclear Safety (IRSN), PSE-ENV, SRTE, LR2T, CE Cadarache, 13115, Saint Paul les Durance Cedex, France.
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12
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Manaka T, Ohashi S, Ogo S, Otsuka Y, Furusawa H. Sorption and desorption experiments using stable cesium: considerations for radiocesium retention by fresh plant residues in Fukushima forest soils. J Radioanal Nucl Chem 2021. [DOI: 10.1007/s10967-021-07749-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
AbstractWe conducted sorption experiments with stable cesium (133Cs) solution in different organic matter samples, aiming to understand the sorption of radiocesium (134Cs and 137Cs) in the initial throughfall by fresh plant residues (e.g., needles, wood, and bark from Japanese cedar trees) in the Oi horizon in forests in Fukushima. Among the organic matter samples, bark and wattle tannin sorbed relatively large amounts of Cs, whereas wood and cellulose powder sorbed small amounts. In contrast, samples containing clay minerals showed much higher Cs sorption. We also conducted desorption experiments, and suggested that Cs on the organic matter samples were relatively mobile.
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13
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Imamura N, Watanabe M, Manaka T. Estimation of the rate of 137Cs root uptake into stemwood of Japanese cedar using an isotopic approach. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 755:142478. [PMID: 33045609 DOI: 10.1016/j.scitotenv.2020.142478] [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: 05/12/2020] [Revised: 09/16/2020] [Accepted: 09/16/2020] [Indexed: 06/11/2023]
Abstract
Japanese cedar (Cryptomeria japonica) is the main timber species in Japan. The prediction of the temporal changes in the 137Cs concentration in the stemwood of Japanese cedar after the Fukushima nuclear accident is essential for optimizing forest management in contaminated areas. However, it is difficult to estimate the respective contributions of root and foliar uptake to 137Cs accumulation in stemwood from simple field measurements, especially in trees that contain the residue of initially-deposited 137Cs. In this study, we devised a method for estimating the rate of 137Cs root uptake into stemwood using the 133Cs content in stemwood and the 137Cs/133Cs ratio in the exchangeable fraction of soil. As a trial, the method was applied to a cedar stand in Fukushima Prefecture, using available monitoring data from prior studies over 5 years from August 2011 to August 2016. The mean annual rate of 137Cs root uptake into stemwood over this period was estimated as 53 ± 20 Bq m-2 yr-1. We note that our method likely provided a maximum estimate, because it is based on the assumptions that 133Cs in wood is exclusively supplied by root uptake, and that Cs isotopes are taken up by roots in the top 5 cm of mineral soil. Moreover, the mean annual increase of the 137Cs inventory in stemwood during the study period was measured as 108 Bq m-2 yr-1, although this value was associated with considerable uncertainty (95% confidence interval from -109 to 324 Bq m-2 yr-1). As a result, the maximum estimated rate of 137Cs root uptake into stemwood accounted for around half of the measured rate of 137Cs accumulation in stemwood. Our results show that the Cs isotopic approach has potential to distinguish the main pathway of stemwood contamination (i.e., root vs. foliar uptake) following radioactive fallout.
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Affiliation(s)
- Naohiro Imamura
- Department of Forest Soils, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Mirai Watanabe
- Center for Regional Environmental Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
| | - Takuya Manaka
- Department of Forest Soils, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
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14
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Sakuma K, Yoshimura K, Nakanishi T. Leaching characteristics of 137Cs for forest floor affected by the Fukushima nuclear accident: A litterbag experiment. CHEMOSPHERE 2021; 264:128480. [PMID: 33032218 DOI: 10.1016/j.chemosphere.2020.128480] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 09/09/2020] [Accepted: 09/27/2020] [Indexed: 06/11/2023]
Abstract
In forest ecosystems, forest litter is considered an active medium for radiocesium (137Cs). To understand discharge mechanisms of highly bioavailable dissolved 137Cs from forests to river systems, we investigated the characteristics of 137Cs leaching from forest litter as observed from litterbag experiments. Leaching experiments with conifer needle and deciduous broadleaf litters were then conducted. After soaking conifer needles and broadleaf litters for 20 min, 140 min, and 1 day, the mean values of the 137Cs leaching ratios were 0.13-2.0% and 0.81-6.6%, respectively, indicating that 137Cs leaching ratios are different between forest litter types. To elucidate the factors affecting 137Cs leaching from forest litter, a multi-regression analysis of 137Cs leaching ratios was conducted against antecedent mean precipitation and temperature before sampling the litterbag and accumulated temperature during the litterbag experiments. The 137Cs leaching ratios showed a negative correlation to the antecedent mean precipitation for both litters and the accumulated temperature for broadleaf litters, whereas it exhibited a positive correlation with the antecedent mean temperature for both litters and the accumulated temperature for conifer needle litters. It was proposed that the fraction of 137Cs in labile sites in forest litter increased/decreased due to litter decomposition by antecedent/accumulated temperature, and that this fraction can be washed off by the antecedent precipitation. The different effects of accumulated temperature on 137Cs leaching from conifer needles and broadleaf litters could be due to their different decomposition rates. Our results contribute further the understanding of the mechanisms associated with dissolved 137Cs discharge from forested catchments.
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Affiliation(s)
- Kazuyuki Sakuma
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan.
| | - Kazuya Yoshimura
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan
| | - Takahiro Nakanishi
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, Fukushima, 963-7700, Japan
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15
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Malins A, Imamura N, Niizato T, Takahashi J, Kim M, Sakuma K, Shinomiya Y, Miura S, Machida M. Calculations for ambient dose equivalent rates in nine forests in eastern Japan from 134Cs and 137Cs radioactivity measurements. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 226:106456. [PMID: 33217723 DOI: 10.1016/j.jenvrad.2020.106456] [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: 08/19/2020] [Revised: 10/29/2020] [Accepted: 11/04/2020] [Indexed: 06/11/2023]
Abstract
Understanding the relationship between the distribution of radioactive 134Cs and 137Cs in forests and ambient dose equivalent rates (H˙∗(10)) in the air is important for researching forests in eastern Japan affected by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This study used a large number of measurements from forest samples, including 134Cs and 137Cs radioactivity concentrations, densities and moisture contents, to perform Monte Carlo radiation transport simulations for H˙∗(10) between 2011 and 2017. Calculated H˙∗(10) at 0.1 and 1 m above the ground had mean residual errors of 19% and 16%, respectively, from measurements taken with handheld NaI(Tl) scintillator survey meters. Setting aside the contributions from natural background radiation, 134Cs and 137Cs in the organic layer and the top 5 cm of forest soil generally made the largest contributions to calculated H˙∗(10). The contributions from 134Cs and 137Cs in the forest canopy were calculated to be largest in the first two years following the accident. Uncertainties were evaluated in the simulation results due to the measurement uncertainties in the model inputs by assuming Gaussian measurement errors. The mean uncertainty (relative standard deviation) of the simulated H˙∗(10) at 1 m height was 11%. The main contributors to the total uncertainty in the simulation results were the accuracies to which the 134Cs and 137Cs radioactivities of the organic layer and top 5 cm of soil, and the vertical distribution of 134Cs and 137Cs within the 5 cm soil layers, were known. Radioactive cesium located in the top 5 cm of soil was the main contributor to H˙∗(10) at 1 m by 2016 or 2017 in the calculation results for all sites. Studies on the 137Cs distribution within forest soil will therefore help explain radiation levels henceforth in forests affected by the FDNPP accident. The merits of this study are that it modelled multiple forests for a long time period, with the important model inputs being informed by field measurements, and it quantified how the measurement uncertainties in these inputs affected the calculation results.
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Affiliation(s)
- Alex Malins
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba, 277-0871, Japan.
| | - Naohiro Imamura
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Tadafumi Niizato
- Japan Atomic Energy Agency, Collaborative Laboratories for Advanced Decommissioning Science (CLADS) Environmental Research Group, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Junko Takahashi
- Center for Research in Isotopes and Environmental Dynamic, University of Tsukuba, Tennodai 1-1-1, Tsukuba-shi, Ibaraki, 305-8572, Japan
| | - Minsik Kim
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba, 277-0871, Japan
| | - Kazuyuki Sakuma
- Japan Atomic Energy Agency, Collaborative Laboratories for Advanced Decommissioning Science (CLADS) Environmental Research Group, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Yoshiki Shinomiya
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Satoru Miura
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Masahiko Machida
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba, 277-0871, Japan
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16
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Gonze MA, Calmon P, Hurtevent P, Coppin F. Meta-analysis of radiocesium contamination data in Japanese cedar and cypress forests over the period 2011-2017. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 750:142311. [PMID: 33182179 DOI: 10.1016/j.scitotenv.2020.142311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/07/2020] [Accepted: 09/07/2020] [Indexed: 06/11/2023]
Abstract
Since Fukushima accident, dozens of field studies have been conducted in order to quantify and understand the behaviour of atmospheric radiocesium (137Cs) fallouts in contaminated forests of Fukushima and neighbouring prefectures. In this paper, we carry out a detailed review of data acquired over 2011-2017 in Japanese cedar and cypress plantations, focusing on aerial tree organs, soil layers and tree-to-soil depuration fluxes. To enable comparison and reinforce the consistency between sites, radiological measurements were normalized by the deposit and interpolated onto the same spatio-temporal frame. Despite some (poorly explained) residual variability, we derived a "mean" pattern by log-averaging data among sites. These "mean" results were analysed with the help of a simple mass-balance approach and discussed in the light of post-Fukushima literature. We demonstrated that the activity levels and dynamics in all compartments were consistent and generally well reproduced by the mass balance approach, for values of the interception fraction between 0.7 and 0.85. The analysis indicated that about 5% of the initial deposit remained in the aerial vegetation after 6 years, more than two thirds of intercepted 137Cs being transferred to the soil due to throughfall. The simulations indicated that foliar uptake might have contributed between 40% and 100% to the activity transferred to stem wood. The activity concentration in canopy organs rapidly decreased in the first few months then more slowly, according to an effective half-life of about 1.6 years. The activity level in the organic layer peaked in summer 2011 then decreased according to an effective half-life of 2.2 years. After a rapid increase in 2011, the contamination of mineral horizons continued to increase more slowly, 85% of 137Cs incoming through the organic layer being retained in the 0-5 cm layer according to a mean residence time longer than in the upper layer (7 against 1.5 years).
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Affiliation(s)
- M-A Gonze
- Institute of Radiation Protection and Nuclear Safety, CE Cadarache-Bat 153, BP3, 13115 St-Paul-lez-Durance cedex, France.
| | - P Calmon
- Institute of Radiation Protection and Nuclear Safety, CE Cadarache-Bat 153, BP3, 13115 St-Paul-lez-Durance cedex, France
| | - P Hurtevent
- Institute of Radiation Protection and Nuclear Safety, CE Cadarache-Bat 153, BP3, 13115 St-Paul-lez-Durance cedex, France
| | - F Coppin
- Institute of Radiation Protection and Nuclear Safety, CE Cadarache-Bat 153, BP3, 13115 St-Paul-lez-Durance cedex, France
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17
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Komatsu M, Suzuki N, Ogawa S, Ota Y. Spatial distribution of 137Cs concentrations in mushrooms (Boletus hiratsukae) and their relationship with soil exchangeable cation contents. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 222:106364. [PMID: 32791375 DOI: 10.1016/j.jenvrad.2020.106364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 07/19/2020] [Accepted: 07/19/2020] [Indexed: 06/11/2023]
Abstract
The activity concentrations of radiocesium (137Cs) in wild mushrooms are reported to vary according to species, genus or ecological types. In addition, the concentration fluctuates among the same species collected within the same area. Therefore, we investigated whether the 137Cs concentration of wild mushrooms would be (1) spatially biased, or (2) influenced by the 137Cs or exchangeable potassium concentrations in the soils below. We set two survey plots 300 m apart in a Himalayan cedar forest in Tsukuba, Japan, where ca. 30 kBq/m2 of 137Cs was deposited after the Fukushima Nuclear Power Plant accident. From these plots, we collected fruit-bodies (fungal structures for spore production) of co-occurring Boletus hiratsukae, a mycorrhizal species, as well as from the soil below. The mean 137Cs concentrations in the fruit-bodies were significantly different between the two plots, but no difference was observed in the soil 137Cs concentration between the plots. Significant spatial autocorrelation was observed in the 137Cs concentration in the organic layer for both sites, but no significant spatial autocorrelation was observed in the 137Cs of fruit-bodies. Therefore, the variation in the 137Cs concentrations of co-occurred B. hiratsukae was not explained by spatial bias or radioactivity in the below soil. In contrast, the exchangeable potassium concentration in the soil was negatively correlated with the 137Cs in the fruit-bodies. Our results suggest that the 137Cs absorption of wild mushrooms would be suppressed by the competitive effect of exchangeable potassium in the surrounding soils.
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Affiliation(s)
- Masabumi Komatsu
- Department of Mushroom Science and Forest Microbiology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan.
| | - Narimi Suzuki
- Department of Forest Science and Resources, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
| | - Shuta Ogawa
- Department of Forest Science and Resources, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan; Nara Zoen Corporation, 1-13-3 Shinyokohama, Kohoku, Yokohama, Kanagawa, 222-0033, Japan
| | - Yuko Ota
- Department of Forest Science and Resources, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa, 252-0880, Japan
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18
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Manaka T, Ono K, Furusawa H, Ogo S, Miura S. Chemical sequential extraction of O horizon samples from Fukushima forests: Assessment for degradability and radiocesium retention capacity of organic matters. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 220-221:106306. [PMID: 32658642 DOI: 10.1016/j.jenvrad.2020.106306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 05/08/2020] [Accepted: 05/08/2020] [Indexed: 06/11/2023]
Abstract
To investigate how radiocesium (137Cs) is retained in the O horizon via interactions with organic matter, we collected O horizon samples in Japanese cedar (Cryptomeria japonica) and konara oak (Quercus serrata) forest sites in Fukushima during the 8 years following the Fukushima Dai-ichi Nuclear Power Plant accident. To assess degradability and 137Cs retention capacity of organic matter, we conducted chemical sequential extraction with organic solvent and sulfuric acid, collecting the following fractions: organic solvent extractives (Fraction 1), acid-soluble carbohydrates (Fraction 3), and acid-insoluble residue (Fraction 4). In all samples, across sampling years and sites, 137Cs content in Fractions 1, 3, and 4, as a proportion of the total 137Cs content, was 0.0-23.6%, 18.4-42.9%, and 44.8-76.0%, respectively. Generally, 137Cs is considered to be electrostatically bound to organic matter and relatively mobile, making it easily extractable by sulfuric acid treatment. However, we observed a relatively high proportion of 137Cs in Fraction 4, suggesting strong retention of 137Cs and their immobility in the O horizon. Complex organic matter such as lignin or tannin may contribute this retention. We also noted that some part of 137Cs may be also retained by clay minerals in the O horizon. Although organic matter in Fractions 1 and 3 is considered to decompose faster than that in Fraction 4, over the observation period the 137Cs proportion and net rate of decrease in 137Cs content (in total and in each fraction) remained nearly constant. This result implies that decomposition of organic matter and the consequent release of bound 137Cs may be partly compensated by additional input of 137Cs from the canopy and 137Cs recycling by soil microorganisms. Our study highlights the potential role of organic matter in the O horizon as a temporary reservoir of 137Cs and a driver of the 137Cs cycle in forest ecosystems.
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Affiliation(s)
- Takuya Manaka
- Department of Forest Soils, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan.
| | - Kenji Ono
- Tohoku Research Center, Forestry and Forest Products Research Institute, 92-25 Nabeyashiki, Shimokuriyagawa, Morioka, Iwate, 020-0123, Japan
| | - Hitomi Furusawa
- Department of Forest Soils, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Sumika Ogo
- Department of Mushroom Science and Forest Microbiology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Satoru Miura
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
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19
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Wakabayashi S, Takahashi S, Matsunami H, Hamamatsu S, Hachinohe M, Kihou N, Yamaguchi N. Evaluation of 137Cs ageing by dynamics of 137Cs/ 133Cs ratio in Andosol paddy fields with/without potassium fertilizer application. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 218:106252. [PMID: 32421576 DOI: 10.1016/j.jenvrad.2020.106252] [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: 08/19/2019] [Revised: 02/25/2020] [Accepted: 03/15/2020] [Indexed: 06/11/2023]
Abstract
The mobility of 137Cs in soil decreases with time owing to fixation by micaceous minerals. Such ageing is a critical parameter for estimating and predicting annual change in 137Cs contamination risk of agricultural products. The decrease in the exchangeable fraction of 137Cs has traditionally been used as an index of the 137Cs ageing. Under field conditions, however, exchangeable 137Cs is influenced by several environmental factors. In this study, we propose a new index to evaluate the 137Cs ageing with minimum influence of environmental factors. The ratio of the exchangeable 137Cs fraction to exchangeable fraction of 133Cs ((137Cs/133Cs)exch) eliminates the influence of environmental factors on exchangeable 137Cs. We assessed the applicability of the (137Cs/133Cs)exch index, using a four-year field study of a rice paddy in allophanic Andosol, starting 200 days after the Fukushima Dai-ichi Nuclear Power Plant accident. The influence of K fertilization was also investigated. The 137Cs and 133Cs exchangeable fractions varied together, indicating that both were similarly controlled by environmental factors. The values of (137Cs/133Cs)exch decreased with time, reflecting 137Cs fixation by the ageing. The half-time of the (137Cs/133Cs)exch decline was 6.6-17.7 years. Relative to K fertilization, the lack of K fertilization seemed to affect the 137Cs ageing in two ways: the early 137Cs fixation progressed more rapidly, probably because fewer competing K+ ions were present, and the long-term ageing process was occasionally hampered, probably by the release of reserve K from micaceous minerals. The (137Cs/133Cs)exch values were similar to the ratio of the 137Cs to 133Cs transfer factor of the rice straw. Thus, we conclude that the (137Cs/133Cs)exch index is reliable for evaluating the 137Cs ageing, decrease in 137Cs mobility caused by the diffusion into micaceous mineral interlayer, in the field.
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Affiliation(s)
- Shokichi Wakabayashi
- Tohoku Agricultural Research Center, NARO (National Agriculture and Food Research Organization), 50 Harajukuminami, Arai, Fukushima, Fukushima, 960-2156, Japan.
| | - Shigeru Takahashi
- Central Region Agricultural Research Center, NARO, 2-1-18 Kannondai, Tsukuba, Ibaraki, 305-8666, Japan.
| | - Hisaya Matsunami
- Tohoku Agricultural Research Center, NARO (National Agriculture and Food Research Organization), 50 Harajukuminami, Arai, Fukushima, Fukushima, 960-2156, Japan.
| | - Shioka Hamamatsu
- Headquarters, NARO, 3-1-1 Kannondai, Tsukuba, Ibaraki, 305-8517, Japan.
| | - Mayumi Hachinohe
- Food Research Institute, NARO, 2-1-12 Kannondai, Tsukuba, Ibaraki, 305-8642, Japan.
| | - Nobuharu Kihou
- Institute for Agro-Environmental Sciences, NARO, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan.
| | - Noriko Yamaguchi
- Institute for Agro-Environmental Sciences, NARO, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan.
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Cui L, Taira Y, Matsuo M, Orita M, Yamada Y, Takamura N. Environmental Remediation of the difficult-to-return zone in Tomioka Town, Fukushima Prefecture. Sci Rep 2020; 10:10165. [PMID: 32576864 PMCID: PMC7311413 DOI: 10.1038/s41598-020-66726-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 05/26/2020] [Indexed: 11/17/2022] Open
Abstract
Temporal variations in ambient dose rates in a restricted area designated as "difficult-to-return" for residents of Tomioka Town, Fukushima Prefecture were evaluated in a car-borne survey during 2018-2019. The median dose rates in the "Decontaminated area" in the difficult-to-return zone decreased rapidly from 1.0 μSv/h to 0.32 μSv/h; however, the median dose rates in the "Non-decontaminated area" and "Radioactive waste storage area" fluctuated between 1.1-1.4 μSv/h and 0.46-0.61 μSv/h, respectively. The detected rate of the cesium-137 (137Cs) (137Cs-detected points per all measuring points) in the "Decontaminated area" also decreased rapidly from 64% to 6.7%, accompany with decreasing in ambient dose rates. On the other hand, the detection of 137Cs in the "Radioactive waste storage area" and "Non-decontaminated area" decreased from 53% to 17% and 93% to 88%, respectively. We confirmed that the dose rates in the Decontaminated area dramatically decreased due to decontamination work aiming to help residents return home. Moreover, the estimated external exposure dose of workers during the present survey was 0.66 mSv/y in the Decontaminated area and 0.55 mSv/y in the Radioactive waste storage area, respectively. This case of Tomioka Town within the "difficult-to-return zone" may be the first reconstruction model for evaluating environmental contamination and radiation exposure dose rates due to artificial radionuclides derived from the nuclear disaster.
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Affiliation(s)
- Limeng Cui
- Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki City, Nagasaki Prefecture, 852-8523, Japan
| | - Yasuyuki Taira
- Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki City, Nagasaki Prefecture, 852-8523, Japan.
| | - Masahiko Matsuo
- Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki City, Nagasaki Prefecture, 852-8523, Japan
| | - Makiko Orita
- Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki City, Nagasaki Prefecture, 852-8523, Japan
| | - Yumiko Yamada
- Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki City, Nagasaki Prefecture, 852-8523, Japan
| | - Noboru Takamura
- Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki City, Nagasaki Prefecture, 852-8523, Japan
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21
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Koarashi J, Atarashi-Andoh M, Nishimura S, Muto K. Effectiveness of decontamination by litter removal in Japanese forest ecosystems affected by the Fukushima nuclear accident. Sci Rep 2020; 10:6614. [PMID: 32313049 PMCID: PMC7171154 DOI: 10.1038/s41598-020-63520-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 03/31/2020] [Indexed: 11/09/2022] Open
Abstract
The Fukushima Daiichi nuclear power plant accident caused serious radiocesium (137Cs) contamination of forest ecosystems over a wide area. The removal of the forest floor litter layer has been considered a potential method for forest decontamination; however, its effectiveness remains largely unknown. We conducted a pilot-scale decontamination study in a deciduous broadleaved forest in Fukushima. The entire forest was decontaminated by removing the litter layer in July 2014, approximately 3.3 years after the accident, with the exception of two untreated plots. For three years after decontamination, we quantified 137Cs contamination levels in the litter and topsoil layers and in the tree leaves, in the untreated and decontaminated areas. The decreased inventories of litter materials and the litter-associated 137Cs in the decontaminated areas were observed only in the first year after decontamination. Generally, no decontamination effects were observed on the 137Cs transfer in tree leaves. The primary reason for this was the rapid shift in the main reservoir of 137Cs from litter layers to the underlying mineral soil, which differs from the observations in post-Chernobyl studies of European forest ecosystems. The results suggest that litter-removal decontamination can only be successful if it is implemented more quickly (within 1-2 years after the accident) for Japanese forest ecosystems.
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Affiliation(s)
- Jun Koarashi
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
| | - Mariko Atarashi-Andoh
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan
| | - Syusaku Nishimura
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan
| | - Kotomi Muto
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan
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22
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Kubo K, Kobayashi H, Nitta M, Takenaka S, Nasuda S, Fujimura S, Takagi K, Nagata O, Ota T, Shinano T. Variations in radioactive cesium accumulation in wheat germplasm from fields affected by the 2011 Fukushima nuclear power plant accident. Sci Rep 2020; 10:3744. [PMID: 32111908 PMCID: PMC7048790 DOI: 10.1038/s41598-020-60716-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 02/11/2020] [Indexed: 11/09/2022] Open
Abstract
Decreasing the transfer of radioactive cesium (RCs) from soil to crops has been important since the deposition of RCs in agricultural soil owing to the Fukushima nuclear power plant accident of 2011. We investigated the genotypic variation in RCs accumulation in 234 and 198 hexaploid wheat (Triticum spp.) varieties in an affected field in 2012 and 2013, respectively. The effects of soil exchangeable potassium (ExK) content to RCs accumulation in wheat varieties were also evaluated. A test field showed fourfold differences in soil ExK contents based on location, and the wheat varieties grown in areas with lower soil ExK contents tended to have higher grain RCs concentrations. RCs concentrations of shoots, when corrected by the soil ExK content, were positively significantly correlated between years, and RCs concentrations of shoots were significantly correlated with the grain RCs concentration corrected by the soil ExK content. These results indicated that there were genotypic variations in RCs accumulation. The grain to shoot ratio of RCs also showed significant genotypic variation. Wheat varieties with low RCs accumulations were identified. They could contribute to the research and breeding of low RCs accumulating wheat and to agricultural production in the area affected by RCs deposition.
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Affiliation(s)
- Katashi Kubo
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan.
| | - Hiroyuki Kobayashi
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan
- Biodiversity Division, Institute for Agro-Environmental Sciences, NARO, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan
| | - Miyuki Nitta
- Laboratory of Plant Genetics, Graduate School of Agriculture, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Shotaro Takenaka
- Laboratory of Plant Genetics, Graduate School of Agriculture, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
- Faculty of Agriculture, Ryukoku University, 1-5 Yokotani, Setaoe-cho, Otsu, Shiga, 520-2194, Japan
| | - Shuhei Nasuda
- Laboratory of Plant Genetics, Graduate School of Agriculture, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Shigeto Fujimura
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan
| | - Kyoko Takagi
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan
| | - Osamu Nagata
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan
| | - Takeshi Ota
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan
- Bio-oriented Technology Research Advancement Institution, NARO, 8 Higashida-cho, Kawasaki, Kanagawa, 210-0005, Japan
| | - Takuro Shinano
- Agricultural Radiation Research Center, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 50 Harajukuminami, Arai, Fukushima, 960-2156, Japan
- Laboratory of Plant Nutrition, Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, Hokkaido, 060-8589, Japan
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23
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Hashimoto S, Imamura N, Kaneko S, Komatsu M, Matsuura T, Nishina K, Ohashi S. New predictions of 137Cs dynamics in forests after the Fukushima nuclear accident. Sci Rep 2020; 10:29. [PMID: 31913315 PMCID: PMC6949301 DOI: 10.1038/s41598-019-56800-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 10/30/2019] [Indexed: 11/13/2022] Open
Abstract
Most of the area contaminated by the Fukushima Daiichi Nuclear Power Plant accident is covered by forest. In this paper, we updated model predictions of temporal changes in the 137Cs dynamics using the latest observation data and newly provided maps of the predicted 137Cs activity concentration for wood, which is the most commercially important part of the tree body. Overall, the previous prediction and latest observation data were in very good agreement. However, further validation revealed that the migration from the soil surface organic layer to the mineral soil was overestimated for evergreen needleleaf forests. The new prediction of the 137Cs inventory showed that although the 137Cs distribution within forests differed among forest types in the first 5 years, the difference diminished in the later phase. Besides, the prediction of the wood 137Cs activity concentrations reproduced the different trends of the 137Cs activity concentrations for cedar, oak, and pine trees. Our simulation suggests that the changes of the wood 137Cs activity concentration over time will slow down after 5–10 years. Although the model uncertainty should be considered and monitoring and model updating must continue, the study provides helpful information on the 137Cs dynamics within forest ecosystems and the changes in wood contamination.
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Affiliation(s)
- Shoji Hashimoto
- Department of Forest Soils, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan. .,Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8657, Japan.
| | - Naohiro Imamura
- Department of Forest Soils, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan
| | - Shinji Kaneko
- Kansai Research Center, Forestry and Forest Products Research Institute, Fushimi, Kyoto, 612-0855, Japan
| | - Masabumi Komatsu
- Department of Mushroom Science and Forest Microbiology, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan
| | - Toshiya Matsuura
- Department of Forest Management, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan
| | - Kazuya Nishina
- Center for Regional Environmental Research, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan
| | - Shinta Ohashi
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan
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