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Holiaka D, Yoschenko V, Cherniaiev OR, Moskaliuk A, Lesnik O, Levchuk S, Holiaka M, Gumenuk V, Kovbasa Y, Borsuk O, Holik V, Nanba K, Kashparov V. Variability of activity concentrations and radial distributions of 137Cs and 90Sr in trunk wood of Scots pine and Silver birch. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2023; 263:107186. [PMID: 37087959 DOI: 10.1016/j.jenvrad.2023.107186] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/11/2023] [Accepted: 04/17/2023] [Indexed: 05/03/2023]
Abstract
This study analyzes the variability of 137Cs and 90Sr concentrations in wood and their radial distributions in the trunks of Scots pine and Silver birch trees in the small uniformly contaminated forest stands in the Chornobyl Exclusion Zone. Concentrations of both radionuclides follow a lognormal distribution with a large scatter of values measured in the trees within the stands (GSD ranges from 1.6 to 2.0). No correlation was found between the concentrations of the two radionuclides measured in individual trees, or between their concentrations and tree diameter. The average 137Cs and 90Sr Tag were 8.4 × 10-4 m2 kg-1 and 8.8 × 10-3 m2 kg-1 for pine, respectively, and 9.3 × 10-4 m2 kg-1 and 1.1 × 10-2 m2 kg-1 for birch, indicating a much higher availability of 90Sr for uptake by the studied species. For 137Cs, the Tag values are within the range recommended by the IAEA Handbook (IAEA, 2010), while the values for 90Sr exceed the recommended range for birch and are close to its upper value for pine. The highest concentrations of 137Cs in pine at the height of 1.3 m were measured in the youngest sapwood rings; they were lower in the rest of the sapwood and decreased further in the heartwood, but remained relatively high even in annual rings that were the heartwood at the time of deposition, suggesting sapwood-to-heartwood translocation of the radionuclide by diffusion and/or ray transport. In contrast, 90Sr concentrations increased through the sapwood from the trunk periphery in pine trees up to 80 years old and remained stable through the sapwood in older trees (except for higher concentrations in the young annual rings), but dropped to zero in physiologically inactive heartwood tissues. In most birch trees, regardless of age, 137Cs concentrations demonstrated an increasing trend from the trunk periphery towards the pith, while concentrations of 90Sr were relatively stable in the whole trunk except in the oldest annual rings, where they increased sharply, likely indicating active transport of the radionuclide to senescing tissues.
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Affiliation(s)
- D Holiaka
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine.
| | - V Yoschenko
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima Prefecture, 960-1296, Japan
| | - O R Cherniaiev
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - A Moskaliuk
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - O Lesnik
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - S Levchuk
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - M Holiaka
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - V Gumenuk
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - Y Kovbasa
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - O Borsuk
- Chornobyl Radiation and Ecological Biosphere Reserve, Tolochina str. 28, Ivankiv, Kyiv region, 07201, Ukraine
| | - V Holik
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - K Nanba
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima Prefecture, 960-1296, Japan
| | - V Kashparov
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
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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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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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Origin and hydrodynamics of xylem sap in tree stems, and relationship to root uptake of soil water. Sci Rep 2021; 11:8404. [PMID: 33863961 PMCID: PMC8052340 DOI: 10.1038/s41598-021-87397-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 03/25/2021] [Indexed: 11/11/2022] Open
Abstract
Although 10 years have passed since Japan’s Fukushima nuclear accident, the future radiation risk from 137Cs contamination of wood via root uptake is a serious concern. We estimated the depth at which the roots of evergreen coniferous sugi (Cryptomeria japonica) and broadleaf deciduous konara (Quercus serrata) trees actively take up soil water by using positive δD values from the artificial D2O tracer and seasonal changes in the δ18O values of soil water as a natural environmental tracer. We compared the tracer concentration changes in xylem sap with those in the soil water and ascertained that both tree species primarily took up water from a depth of 20 cm, though with mixing of water from other depths. Using sap hydrodynamics in tree stems, we found that water circulation was significantly slower in heartwood than in sapwood. Heartwood water was not supplied by direct root uptake of soil water. The measured diffusion coefficients for D2O, K+, Cs+, and I− in xylem stems were greater in sapwood than in heartwood, and their magnitude was inversely correlated with their molecular weights. The distribution of D2O and 137Cs concentrations along the radial stem could be explained by simulations using the simple advective diffusion model.
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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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Holiaka D, Yoschenko V, Levchuk S, Kashparov V. Distributions of 137Cs and 90Sr activity concentrations in trunk of Scots pine (Pinus sylvestris L.) in the Chernobyl zone. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 222:106319. [PMID: 32565416 DOI: 10.1016/j.jenvrad.2020.106319] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 05/25/2020] [Accepted: 05/25/2020] [Indexed: 06/11/2023]
Abstract
Possibility of the economical utilization of forests in the radioactive contaminated areas depends on compliance of the radionuclide activity concentrations in wood with the hygiene norms or national standards that are established by the governments or regulators. Since such regulations consider wood as a whole, development of the sampling methods for assessment of compliance of wood to the norms or standards requires the adequate addressing the issues related to heterogeneity of the radionuclide distributions within the tree trunks. In this paper we present spatial distributions of the 90Sr and 137Cs activity concentrations in the trunk wood of mature Scots pine (Pinus sylvestris L.) trees in the Chernobyl exclusion zone in the late stage (30 years) after the deposition. Four 52-53 year old model trees were sampled in the forest stand located in approximately 5 km from the accidental nuclear reactor. The radionuclide concentrations were measured in 156 wood samples collected from the wood disks cut off the tree trunks at the set of heights. To address variability of the tree sizes and radionuclide concentrations between the individual trees, we applied the corresponding relative indices enabling identification of the general patterns of the spatial distributions of 90Sr and 137Cs. We demonstrated significant differences in bioavailability and distribution trends between the studied radionuclides. 137Cs is translocated to the younger parts of the tree trunk, while the 90Sr concentrations are higher in heartwood and in senescing tissues, which is explained by the different chemical properties of Cs and Sr and by different physiological roles played in plant development by their chemical analogs and major plant nutrition elements, Ca and K respectively. In this reason, the principal distribution patterns of the studied radionuclides in the trunk wood do not significantly change with time, and the results of our study generally are in good agreement with those obtained in the earlier stage after the deposition. The above trends are clearly expressed in both radial and longitudinal directions and result in systematic deviation of the concentrations estimated based on core sampling from the average concentrations in the whole tree trunk.
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Affiliation(s)
- Dmytrii Holiaka
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine.
| | - Vasyl Yoschenko
- Institute of Environmental Radioactivity at Fukushima University, 1 Kanayagawa, Fukushima, Fukushima, Prefecture, 960-1296, Japan
| | - Sviatoslav Levchuk
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
| | - Valery Kashparov
- Ukrainian Institute of Agricultural Radiology of the National University of Life and Environmental Sciences of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv region, 08162, Ukraine
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7
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Yoschenko V, Takase T, Hinton TG, Nanba K, Onda Y, Konoplev A, Goto A, Yokoyama A, Keitoku K. Radioactive and stable cesium isotope distributions and dynamics in Japanese cedar forests. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 186:34-44. [PMID: 29029765 DOI: 10.1016/j.jenvrad.2017.09.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Revised: 09/26/2017] [Accepted: 09/26/2017] [Indexed: 06/07/2023]
Abstract
Dynamics of the Fukushima-derived radiocesium and distribution of the natural stable isotope 133Cs in Japanese cedar (Cryptomeria japonica D. Don) forest ecosystems were studied during 2014-2016. For the experimental site in Yamakiya, Fukushima Prefecture, we present the redistribution of radiocesium among ecosystem compartments during the entire observation period, while the results obtained at another two experimental site were used to demonstrate similarity of the main trends in the Japanese forest ecosystems. Our observations at the Yamakiya site revealed significant redistribution of radiocesium between the ecosystem compartments during 2014-2016. During this same period radionuclide inventories in the aboveground tree biomass were relatively stable, however, radiocesium in forest litter decreased from 20 ± 11% of the total deposition in 2014 to 4.6 ± 2.7% in 2016. Radiocesium in the soil profile accumulated in the 5-cm topsoil layers. In 2016, more than 80% of the total radionuclide deposition in the ecosystem resided in the 5-cm topsoil layer. The radiocesium distribution between the aboveground biomass compartments at Yamakiya during 2014-2016 was gradually approaching a quasi-equilibrium distribution with stable cesium. Strong correlations of radioactive and stable cesium isotope concentrations in all compartments of the ecosystem have not been reached yet. However, in some compartments the correlation is already strong. An increase of radiocesium concentrations in young foliage in 2016, compared to 2015, and an increase in 2015-2016 of the 137Cs/133Cs concentration ratio in the biomass compartments with strong correlations indicate an increase in root uptake of radiocesium from the soil profile. Mass balance of the radionuclide inventories, and accounting for radiocesium fluxes in litterfall, throughfall and stemflow, enabled a rough estimate of the annual radiocesium root uptake flux as 2 ± 1% of the total inventory in the ecosystem.
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Affiliation(s)
- Vasyl Yoschenko
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan.
| | - Tsugiko Takase
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Thomas G Hinton
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Kenji Nanba
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Yuichi Onda
- Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba, Ibaraki Prefecture, 305-8572, Japan
| | - Alexei Konoplev
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Azusa Goto
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Aya Yokoyama
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
| | - Koji Keitoku
- Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan
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Gonze MA, Calmon P. Meta-analysis of radiocesium contamination data in Japanese forest trees over the period 2011-2013. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 601-602:301-316. [PMID: 28570967 DOI: 10.1016/j.scitotenv.2017.05.175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/15/2017] [Accepted: 05/20/2017] [Indexed: 06/07/2023]
Abstract
The fate and dispersion of radiocesium in forests affected by the Fukushima atmospheric fallouts have been efficiently characterized by Japanese scientists thanks to monitoring surveys of radioactive contents in contaminated soil, water, and vegetation samples at numerous sites. In this paper, we carry out a meta-analysis of the field surveys conducted over the period 2011-2013 in evergreen coniferous and deciduous broadleaf forests of Fukushima or neighboring prefectures. The review focuses on contamination data acquired in tree vegetation - about 1500 spatio-temporal measurements of concentrations, inventories and depuration fluxes - with a particular interest for organs that were directly exposed to the atmospheric fallouts and subjected to depuration mechanisms (foliage, branches and outer bark). To reduce the spatial variability between the sites, radioactive data were normalized by the total deposit estimated at each site. Our analysis highlights the overall consistency of field observations despite the variety of experimental protocols, disparate sampling periods, differences in the forest stand characteristics and variability of the atmospheric deposition conditions. Assuming that the sites conformed to the same dynamics (within the range of residual variability), we then derive, discuss, and compare the mean representative evolutions of radiocesium contamination in the two categories of forest. Thanks to a simple mass balance approach, we finally demonstrate that: (i) about 90% of the radiocesium deposit was intercepted by evergreen coniferous vegetation, (ii) 80% of the deposit was gradually transferred to the forest floor in 3years, according to a well characterized depuration kinetics, and (iii) about 4% was readily absorbed by the foliage and translocated to internal organs (inner bark, stem wood and roots) at a rate of about 10-4d-1.
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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
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Ohashi S, Kuroda K, Takano T, Suzuki Y, Fujiwara T, Abe H, Kagawa A, Sugiyama M, Kubojima Y, Zhang C, Yamamoto K. Temporal trends in 137Cs concentrations in the bark, sapwood, heartwood, and whole wood of four tree species in Japanese forests from 2011 to 2016. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2017; 178-179:335-342. [PMID: 28965024 DOI: 10.1016/j.jenvrad.2017.09.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 09/05/2017] [Accepted: 09/13/2017] [Indexed: 06/07/2023]
Abstract
To understand the changes in radiocesium (137Cs) concentrations in stem woods after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, we investigated 137Cs concentrations in the bark, sapwood, heartwood, and whole wood of four major tree species at multiple sites with different levels of radiocesium deposition from the FDNPP accident since 2011 (since 2012 at some sites): Japanese cedar at four sites, hinoki cypress and Japanese konara oak at two sites, and Japanese red pine at one site. Our previous report on 137Cs concentrations in bark and whole wood samples collected from 2011 to 2015 suggested that temporal variations were different among sites even within the same species. In the present study, we provided data on bark and whole wood samples in 2016 and separately measured 137Cs concentrations in sapwood and heartwood samples from 2011 to 2016; we further discussed temporal trends in 137Cs concentrations in each part of tree stems, particularly those in 137Cs distributions between sapwood and heartwood, in relation to their species and site dependencies. Temporal trends in bark and whole wood samples collected from 2011 to 2016 were consistent with those reported in samples collected from 2011 to 2015. Temporal variations in 137Cs concentrations in barks showed either a decreasing trend or no clear trend, implying that 137Cs deposition in barks is inhomogeneous and that decontamination is relatively slow in some cases. Temporal trends in 137Cs concentrations in sapwood, heartwood, and whole wood were different among species and also among sites within the same species. Relatively common trends within the same species, which were increasing, were observed in cedar heartwood, and in oak sapwood and whole wood. On the other hand, the ratio of 137Cs concentration in heartwood to that in sapwood (fresh weight basis) was commonly increased to more than 2 in cedar, although distinct temporal trends were not found in the other species, for which the ratio was around 1 in cypress and pine and below 0.5 in oak, suggesting that 137Cs transfer from sapwood to heartwood shows species dependency. Consequently, the species dependency of 137Cs transfer within the tree appears easily, while that from the environment to the trees can be masked by various factors. Thus, prediction of 137Cs concentrations in stem wood should be carried out carefully as it still requires investigations at multiple sites with a larger sample size and an understanding of the species-specific 137Cs transfer mechanism.
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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; Center for Forest Restoration and Radioecology, 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
| | - Tsutomu Takano
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Center for Forest Restoration and Radioecology, 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
- 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
| | - Masaki Sugiyama
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Yoshitaka Kubojima
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Chunhua Zhang
- Department of Wood Properties and Processing, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Koichi Yamamoto
- Center for Forest Restoration and Radioecology, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
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Radiocaesium partitioning in Japanese cedar forests following the "early" phase of Fukushima fallout redistribution. Sci Rep 2016; 6:37618. [PMID: 27876870 PMCID: PMC5120304 DOI: 10.1038/srep37618] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 10/21/2016] [Indexed: 11/09/2022] Open
Abstract
Our study focused on radiocaesium (137Cs) partitioning in forests, three vegetation periods after the Fukushima Daiichi nuclear power plant accident. 137Cs distribution in forest components (organic and mineral soil layers as well as tree compartments: stem, bark, needles, branches and roots) was measured for two Japanese cedar stand ages (17 and 33 years old). The results showed that around 85% of the initial deposit was found in the forest floor and topsoil. For the youngest stand almost 70% of the deposit is present in the forest floor, whereas for the oldest stand 50% is present in the 0-3 cm mineral soil layer. For trees, old and perennial organs (including dead and living needles and branches, litter fall and outer bark) directly exposed to the fallout remained the most contaminated. The crown concentrated 61-69% of the total tree contamination. Surprisingly the dead organs concentrated 25 ± 9% (young cedars) to 36 ± 20% (mature cedar) of the trees' residual activity, highlighting the importance of that specific compartment in the early post-accident phase for Japanese cedar forests. Although the stem (including bark) represents the highest biomass pool, it only concentrates 3.3% and 4.6% of the initial 137Cs deposit for mature and young cedars, respectively.
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