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Banerjee A. Conceptualization of the comprehensive phyto-radiotoxicity incurred by radiocesium and strategies to expunge the metal using biotechnological and phytoremediative approaches. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2024; 207:108330. [PMID: 38181642 DOI: 10.1016/j.plaphy.2023.108330] [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: 09/01/2023] [Revised: 10/27/2023] [Accepted: 12/31/2023] [Indexed: 01/07/2024]
Abstract
Agricultural pollution with 137Cs is an ecological threat due to its sustained half-life and radioactivity. Release of radiocesium isotopes after major nuclear power plant accidents like the Fukushima Dai-ichi and the Chernobyl nuclear power plant disasters have severely affected the surrounding growth of agricultural crops and vegetables cultivated across extensive areas. Even years after the nuclear accidents, biosafety in these agricultural fields is still questionable. Due to similarity in charge and ionic radius between radiocesium and K+, the radionuclides are promiscuously uptaken via K+ channels expressed in plants. Bioaccumulation of radiocesium reportedly promotes physiological and anatomical anomalies in crops due to radiation and also affects the rhizospheric architecture. Due to radiation hazard, the ecological balance and quality are compromised and ingestion of such contaminated food results in irreversible health hazards. Recently, strategies like exogenous supplementation of K+ or genetic engineering of K+ channels were able to reduce radiocesium bioaccumulation in plants taking the advantage of competition between radiocesium and K+ translocation. Furthermore, bioremediation strategies like phycoremediation, mycoremediation, phytoremediation and rhizofiltration have also showed promising results for removing radiocesium from polluted sites. It has been proposed that these eco-friendly ways can be adopted to de-pollute the contaminated sites prior to subsequent cultivation of crops and vegetables. Hence it is essential to: 1) understand the basic radiotoxic effects of radiocesium on agricultural crops and surrounding vegetation and, 2) design sustainable ameliorative strategies to promote radiocesium tolerance for ensuring food and social security of the affected population.
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Affiliation(s)
- Aditya Banerjee
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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2
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Noda Y, Yoshihara T, Suzui N, Yin YG, Miyoshi Y, Enomoto K, Kawachi N. Visualization of the initial radiocesium dynamics after penetration in living apple trees with bark removal using a positron-emitting 127Cs tracer. Appl Radiat Isot 2023; 198:110859. [PMID: 37267714 DOI: 10.1016/j.apradiso.2023.110859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 05/14/2023] [Accepted: 05/17/2023] [Indexed: 06/04/2023]
Abstract
Following the Fukushima nuclear accident in March 2011, radiocesium (rCs) contamination in deciduous trees remains over 10 years later even though the trees were leafless at the time of the accident. This phenomenon is considered to be the result of repeated retranslocation of rCs that initially penetrated the bark into the internal tissues. To implement effective measures after a possible accident in the future, it is necessary to clarify how rCs is translocated in the tree after penetration. In this study, rCs translocation was dynamically visualized using a positron-emitting tracer imaging system (PETIS) and autoradiography after the bark of apple branches was removed. The PETIS results showed the translocation of 127Cs from the branch to young shoots and the main stem in apple trees under controlled spring growing conditions. The transport velocity of rCs in the branch was faster than that in the main stem. The transport of rCs, which was either acropetal or basipetal, in the main stem through the branch junction favored basipetal movement. Autoradiography of transverse sections of the main stem indicated that basipetal translocation was due to transport in the phloem. This study demonstrated the initial translocation responses of rCs similar to previous field research, which indicates that rCs transport to the young shoots tends to be higher under controlled conditions. Our laboratory-based experimental system may be useful to gain an improved understanding of rCs dynamics in deciduous trees.
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Affiliation(s)
- Yusaku Noda
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan
| | - Toshihiro Yoshihara
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan; Faculty of Bioscience and Applied Chemistry, Hosei University, Tokyo, 184-8584, Japan
| | - Nobuo Suzui
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan.
| | - Yong-Gen Yin
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan
| | - Yuta Miyoshi
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan
| | - Kazuyuki Enomoto
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan
| | - Naoki Kawachi
- Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology (QST), Gunma, 370-1292, Japan
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3
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Tanaka T, Thiry Y. How dynamic transfer models can complement an equilibrium-based approach: Case studies of radiocesium transfer to forest trees following accidental atmospheric release. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 884:163715. [PMID: 37137358 DOI: 10.1016/j.scitotenv.2023.163715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 04/18/2023] [Accepted: 04/20/2023] [Indexed: 05/05/2023]
Abstract
Accidental release of radionuclides caused by nuclear accidents like those in Fukushima and Chernobyl can result in pulses of radioactivity entering the forest environment. Due to intense recycling in the forest, equilibrium between radioactivity concentrations in trees and in soil may not be reached during the period of severe short-term radionuclide transport following the accident. Another question arises as to whether the equilibrium hypothesis using empirical concentration ratios (CRs) can be applied to the long-term period. Using two atmospheric 137Cs fallout scenarios in the Fukushima and Chernobyl sites, this study investigated whether the CR approach could provide conservative predictions of 137Cs levels in trees following 137Cs fallout events by comparing predictions from the CR approach using data gathered for trees by the IAEA to those from dynamic transfer models and actual measured data. The inter-comparisons also aimed to investigate whether the CR approach could account for the variability of 137Cs levels across different tree organs. The results showed that caution may be necessary when using the CR approach, which relies on the IAEA dataset, to estimate 137Cs accumulation in forest trees in the short - and long term following atmospheric 137Cs fallout events. A calculation by TRIPS 2.0 demonstrated the importance of considering the distribution within tree organs for in-depth analysis of radiological impact of forest trees. Our findings suggest that it may be preferable to use CR values based on site-specific data rather than generic data collected from various sites. This is particularly relevant when studying the sites where the bioavailability of 137Cs for trees and thus possible exposures are higher. This study also showed that dynamic modeling approaches could offer an alternative means of estimating CR values of the entire tree or specific tree organs in situations where empirically derived values are not available.
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Affiliation(s)
- Taku Tanaka
- EDF R&D, LNHE, 6 Quai Watier, 78400 Chatou, France.
| | - Yves Thiry
- French National Radioactive Waste Management Agency (Andra) - Research and Development Division, 92298 Chatenay-Malabry, France
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4
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Niu A, Lin C. Managing soils of environmental significance: A critical review. JOURNAL OF HAZARDOUS MATERIALS 2021; 417:125990. [PMID: 34229372 DOI: 10.1016/j.jhazmat.2021.125990] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/20/2021] [Accepted: 04/23/2021] [Indexed: 06/13/2023]
Abstract
Globally, environmentally significant soils (ESSs) mainly include acid sulfate, heavy metal(loid)-contaminated, petroleum hydrocarbon-contaminated, pesticide-contaminated, and radionuclide-contaminated soils. These soils are interrelated and have many common characteristics from an environmental management perspective. In this review, we critically evaluate the available literature on individual ESSs, aiming to identify common problems related to environmental quality/risk assessment, remediation approaches, and environmental regulation for these soils. Based on these findings, we highlight the challenges to, and possible solutions for sustainable ESS management. Contaminated land has been rapidly expanding since the first industrial revolution from the industrialized Western countries to the emerging industrialized Asia and other parts of the world. Clean-up of contaminated lands and slowdown of their expansion require concerted international efforts to develop advanced cleaner production and cost-effective soil remediation technologies in addition to improvement of environmental legislation, regulatory enforcement, financial instruments, and stakeholder involvement to create enabling environments. Two particular areas require further action and research efforts: developing a universal system for assessing ESS quality and improving the cost-effectiveness of remediation technologies. We propose an integrated framework for deriving ESS quality indicators and make suggestions for future research directions to improve the performance of soil remediation technologies.
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Affiliation(s)
- Anyi Niu
- School of Geography, South China Normal University, Guangzhou 510631, China
| | - Chuxia Lin
- Faculty of Science, Engineering and Built Environment, Deakin University, Burwood, VIC 3125, Australia.
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Yamashita H, Nishina Y, Komori N, Kamoshita M, Oya Y, Okuno K, Morita A, Ikka T. Cesium uptake and translocation from tea cutting roots (Camellia sinensis L.). JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 235-236:106655. [PMID: 34034207 DOI: 10.1016/j.jenvrad.2021.106655] [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: 12/24/2020] [Revised: 05/13/2021] [Accepted: 05/15/2021] [Indexed: 06/12/2023]
Abstract
To estimate the uptake of radiocesium (137Cs) by tea plant roots, 1-year-old rooted tea cuttings (Camellia sinensis L. cv. Yabukita) at the time of bud opening were cultivated hydroponically for 27 days in pots containing nutrient solutions with or without 137CsCl (600 Bq mL-1). Total 137Cs radioactivity of whole tea plants were 6.1 kBq g-1 dry weight. The plant/solution 137Cs transfer factors of different tissues were in the range of 2.6 (in mature leaves) to 28.2 mL g-1 dry weight (in roots), which were lower than those reported in wheat and spinach. In total, 69% of 137Cs remained in roots and 31% was transported from roots to shoots. The results indicated that 137Cs was preferentially translocated to new shoots, which are used for manufacturing tea, over mature leaves.
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Affiliation(s)
- Hiroto Yamashita
- Laboratory of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan; United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagito, Gifu, 501-1193, Japan
| | - Yoshifumi Nishina
- Laboratory of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan
| | - Naho Komori
- Laboratory of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan
| | - Mizuho Kamoshita
- Laboratory of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan
| | - Yasuhisa Oya
- Radioscience Research Laboratory, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan
| | - Kenji Okuno
- Radioscience Research Laboratory, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan
| | - Akio Morita
- Laboratory of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan; Institute for Tea Science, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan
| | - Takashi Ikka
- Laboratory of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan; Institute for Tea Science, Shizuoka University, 836 Ohya, Shizuoka, Shizuoka, 422-8529, Japan.
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6
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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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7
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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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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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Kenzo T, Saito S, Miura S, Kajimoto T, Kobayashi NI, Tanoi K. Seasonal changes in radiocesium and potassium concentrations in current-year shoots of saplings of three tree species in Fukushima, Japan. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 223-224:106409. [PMID: 32920309 DOI: 10.1016/j.jenvrad.2020.106409] [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: 03/27/2020] [Revised: 08/28/2020] [Accepted: 08/29/2020] [Indexed: 06/11/2023]
Abstract
We studied seasonal changes in radiocesium (137Cs) activity and potassium concentrations in current-year leaves and branches of Pinus densiflora (naturally regenerated saplings), Cryptomeria japonica (planted saplings) and Quercus serrata (planted saplings and coppice shoots) in Fukushima, Japan. We collected current-year shoots from 10 individuals of each species over two growing seasons at intervals of 1-4 months, between June 2016 and December 2017. For the deciduous species Q. serrata, we also collected dead leaves that remained attached to branches in December to investigate reabsorption of 137Cs. All collected shoots were divided into leaves and branches, oven-dried, and ground; dry weights of each sample were recorded. 137Cs activity concentrations were measured using a germanium semiconductor detector. Potassium concentrations were quantified using inductively coupled plasma optical emission spectrometry (ICP-OES). Increases in dry weight were observed in both leaves and branches between May/June and August; growth then slowed considerably and virtually ceased after October. Clear seasonal changes in 137Cs activity concentrations were observed in both 2016 and 2017, regardless of tree species. Concentrations were higher in young leaves and branches during May and June, then decreased and changed relatively little from August to winter. Reduced 137Cs activity concentrations in dead leaves of Q. serrata were observed only in December 2017 (approximately 15% lower than in October). This reduction may indicate reabsorption of 137Cs in leaves prior to shedding. The changes in potassium concentrations were similar to those in 137Cs in both years. Potassium concentrations were higher in young leaves than in mature leaf and branch samples collected later in the year. A reduction of about 50% in the potassium concentrations in dead leaves of Q. serrata was also observed in December. A positive relationship between 137Cs and potassium concentrations in leaves and branches was observed in all species, except for planted Q. serrata. This relationship may indicate that 137Cs moves in tree shoots with potassium. Leaf and branch weight correlated negatively with 137Cs and potassium concentrations. Reduced concentrations may indicate dilution of these elements as a result of biomass increases over the growing season. Our results imply that irrespective of species, 137Cs exhibits seasonal variations resulting from dilution; these variations correspond with trends in potassium, with higher levels in young organs and decreased levels in older organs.
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Affiliation(s)
- Tanaka Kenzo
- Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan.
| | - Satoshi Saito
- Kansai Research Center, Forestry and Forest Products Research Institute, Kyoto, 612-0855, Japan
| | - Satoru Miura
- Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, 305-8687, Japan
| | - Takuya Kajimoto
- Tohoku Research Center, Forestry and Forest Products Research Institute, Morioka, 020-0123, Japan
| | - Natsuko I Kobayashi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-0032, Japan
| | - Keitaro Tanoi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-0032, Japan
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Sakashita W, Miura S, Akama A, Ohashi S, Ikeda S, Saitoh T, Komatsu M, Shinomiya Y, Kaneko S. Assessment of vertical radiocesium transfer in soil via roots. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 222:106369. [PMID: 32801027 DOI: 10.1016/j.jenvrad.2020.106369] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 07/22/2020] [Accepted: 07/22/2020] [Indexed: 06/11/2023]
Abstract
Several years after the Fukushima Daiichi Nuclear Power Plant accident, the surface mineral soil layer is believed to be the main reservoir of radiocesium (137Cs) in forest ecosystems in Japan. Dissolved 137Cs combines with clay minerals in the soil, and hence, it is not expected to easily infiltrate over time. However, previous studies have indicated that 137Cs derived from the older global fallout migrated deeper than that of the Chernobyl accident, and this cannot be explained by only the dissolved 137Cs vertical migration in the soil. Considering the carbon and nutrient dynamics in the forest floor, the 137Cs transfer process in soil via roots may alter its vertical distribution on a decadal scale. Therefore, in this study, we investigated the 137Cs activity concentrations in both roots and soil matrix, by considering four (0-20 cm) or six (0-30 cm) mineral soil layers taken at every 5 cm at seven study sites dominated by one of the six plant species (three coniferous forests, one deciduous forest, two deciduous forests covered by Sasa, and one bamboo forest) in eastern Japan in 2013. Comparing the results of 137Cs activity concentrations between roots and soil matrix taken at the same soil layer, roots at the surface (0-5 cm) layer often showed lower values than the soil matrix. However, roots deeper than 5 cm had higher activity concentrations than the soil matrix, conversely. The 137Cs inventories ratio of roots to soil matrix are about 1% at the 0-5 and 5-10 cm soil layer, and about 2% at the soil layers deeper than 10 cm. These results suggest that decomposition of root litter little affect the short-term vertical migration of 137Cs in the forest soil. However, it indicates that continuous production and mortality of roots with relatively high 137Cs activity concentrations have an important role for changing the vertical distribution of 137Cs on time scale of decades, particularly at deeper soil layers.
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Affiliation(s)
- Wataru Sakashita
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan; Department of Forest Soils, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan.
| | - Satoru Miura
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Akio Akama
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Shinta Ohashi
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan; Department of Wood Properties and Processing, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Shigeto Ikeda
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan; Department of Forest Soils, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Tomoyuki Saitoh
- Tohoku Research Center, FFPRI, 92-25 Nabeyashiki, Shimokuriyagawa, Morioka, Iwate, 020-0123, Japan
| | - Masabumi Komatsu
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan; Department of Mushroom Science and Forest Microbiology, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Yoshiki Shinomiya
- Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan; Department of Forest Soils, FFPRI, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Shinji Kaneko
- Kansai Research Center, FFPRI, 68 Nagaikyutaroh, Momoyama, Fushimi, Kyoto, 612-0855, Japan
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11
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Kanasashi T, Miura S, Hirai K, Nagakura J, Itô H. Relationship between the activity concentration of 137Cs in the growing shoots of Quercus serrata and soil 137Cs, exchangeable cations, and pH in Fukushima, Japan. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 220-221:106276. [PMID: 32560880 DOI: 10.1016/j.jenvrad.2020.106276] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 04/15/2020] [Accepted: 04/15/2020] [Indexed: 06/11/2023]
Abstract
Incorporation of radiocesium by plants via root uptake appears to be affected by some of the exchangeable cations in the soil and/or pH of the soil. However, few studies have examined the relationship between 137Cs in trees and soil properties in the area surrounding the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) after the accident in March 2011. To elucidate the relationships between the root uptake of 137Cs by deciduous broadleaved trees and soil properties, we measured the activity concentration of 137Cs in the growing shoots of coppiced konara oak (Quercus serrata) grown after the FDNPP accident and the amounts of total 137Cs; exchangeable (ex-) 137Cs, ex-K, ex-Mg, and ex-Ca; and pH (H2O) in soils collected from 34 forest stands in Fukushima between December 2016 and May 2017. Ex-137Cs showed a positive linear relationship with the activity concentration of 137Cs in the growing konara oak shoots, whereas ln-transformed ex-K, ex-Mg, ex-Ca, and pH (H2O) showed negative linear relationships with ln-transformed 137Cs activity concentrations in the growing shoots. However, only ex-137Cs and ex-K were identified as significant factors determining the activity concentration of 137Cs in konara oak according to multiple regression methods and a model selection using Akaike information criterion; ex-K had a stronger influence on the activity concentration of 137Cs in konara oak than ex-137Cs. In the present study, we demonstrated that soil ex-K negatively and non-linearly alters 137Cs activity concentration in deciduous broadleaved trees. We also noted that the relationship between 137Cs in deciduous broadleaved trees and soil ex-K in forests without K fertilization was similar to the relationships between 137Cs in other plants and ex-K in K-fertilized lands reported in previous studies of the FDNPP accident.
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Affiliation(s)
- Tsutomu Kanasashi
- Department of Forest Soils, 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.
| | - Keizo Hirai
- Department of Forest Soils, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Junko Nagakura
- Department of Forest Soils, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Hiroki Itô
- Hokkaido Research Center, Forestry and Forest Products Research Institute, 7 Hitsujigaoka, Toyohira, Sapporo, Hokkaido, 062-8516, Japan
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12
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Thiry Y, Tanaka T, Dvornik AA, Dvornik AM. TRIPS 2.0: Toward more comprehensive modeling of radiocaesium cycling in forest. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 214-215:106171. [PMID: 32063289 DOI: 10.1016/j.jenvrad.2020.106171] [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: 12/05/2019] [Revised: 01/14/2020] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
Because internal transfers can play a key role in radiocaesium persistence in trees, a reliable representation of radiocaesium recycling between tree organs in forest models is important for long-term simulations after radioactive fallout in Chernobyl and Fukushima. We developed an upgraded 2.0 version of the initial TRIPS ("Transfer of Radionuclides In Perennial vegetation System") model involving explicit differentiation between tree organs (i.e., foliage, branches, stemwood and bark). The quality of TRIPS 2.0 was evaluated by testing model outputs against independent datasets for pine stands in Belarus and Ukraine. Scenarios involving "hot particle" deposits in forest remained challenging, but in all other scenarios generally positive verification results for soil and tree compartments indicated that the TRIPS 2.0 model adequately combines the major relevant processes. Interestingly, the response of stemwood contamination to changes in radiocaesium availability in soil, as determined by soil conditions, was shown to be more sensitive than for other tree compartments. We recommend the conceptual tree discretization of TRIPS 2.0 for generic forest modeling for two reasons: 1) regardless of different soil conditions, there was concurrent good agreement between simulations and data for individual tree compartments (foliage, branches, stemwood and bark), and 2) the measurements necessary to estimate internal tree transfers are easily accessible to usual field monitoring in forest biogeochemistry (for details, see Goor, F. & Thiry, Y., 2004. Science of the total environment, 325(1-3), 163-180).
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Affiliation(s)
- Y Thiry
- French National Radioactive Waste Management Agency (Andra) - Research and Development Division, 92298, Chatenay-Malabry, France.
| | - T Tanaka
- EDF R&D, LNHE, 6 Quai Watier, 78400, Chatou, France.
| | - A A Dvornik
- Institute of Radiobiology of National Academy of Sciences of Belarus, 4, Fedjuninskogo Str., 246007, Gomel, Belarus.
| | - A M Dvornik
- Gomel State University, Sovetskaya St.104, 246019, Gomel, Belarus.
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13
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Tagami K, Uchida S, Shinano T, Pröhl G. Comparisons of effective half-lives of radiocesium in Japanese tea plants after two nuclear accidents, Chernobyl and Fukushima. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 213:106109. [PMID: 31756642 DOI: 10.1016/j.jenvrad.2019.106109] [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: 09/06/2019] [Revised: 11/12/2019] [Accepted: 11/13/2019] [Indexed: 06/10/2023]
Abstract
The time-dependence of 137Cs in new shoots of tea (Camellia sinensis (L.) Kuntze) following a137Cs-deposition was analyzed and quantified in terms of effective half-lives. The underlying monitoring studies were performed after the accidents in the Chernobyl and the Fukushima Daiichi nuclear power plants for tea plants growing in Japan. The major transfer route for atmospherically deposited radiocaesium to the first new shoots sampled after the accidents were different: for the Fukushima accident, it was mainly translocation of radiocaesium deposited onto old leaves and twigs to the new growth, while direct deposition on the new leaves was the major source after the Chernobyl accident. The effective half-lives in new tea leaves representing the fast and slow components of the decline did not significantly differ between these accidents. Geometric means (ranges) of fast and slow effective half-lives of 137Cs after the Chernobyl accident were 66 d (25-125 d) and 902 d (342-15900 d), respectively, and those after the Fukushima accident were 50 d (26-105 d) and 416 d (222-1540 d), respectively. From these results, 137Cs declines in new tea leaves were similar although contamination conditions were different for these two accidents.
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Affiliation(s)
- Keiko Tagami
- National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-shi, Chiba, 263-8555, Japan.
| | - Shigeo Uchida
- National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-shi, Chiba, 263-8555, Japan
| | - Takuro Shinano
- Research Faculty of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo-shi, Hokkaido, 060-8589, Japan
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14
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Translocation of cesium in the branches of Japanese cedar (Cryptomeria japonica) and Konara oak (Quercus serrata). J Radioanal Nucl Chem 2019. [DOI: 10.1007/s10967-019-06996-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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15
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Muto K, Atarashi-Andoh M, Matsunaga T, Koarashi J. Characterizing vertical migration of 137Cs in organic layer and mineral soil in Japanese forests: Four-year observation and model analysis. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 208-209:106040. [PMID: 31518883 DOI: 10.1016/j.jenvrad.2019.106040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 06/20/2019] [Accepted: 08/27/2019] [Indexed: 06/10/2023]
Abstract
Because of the Fukushima Dai-ichi Nuclear Power Plant accident, forest ecosystems in wide areas were contaminated with 137Cs. It is important to characterize the behavior of 137Cs after its deposition onto forest surface environments for evaluating and preventing long-term radiation risks. In the present study, 137Cs vertical distributions in the soil profile were observed repeatedly at five forest sites with different vegetation types for 4.4 years after the accident in 2011, and 137Cs migration in the organic layer and mineral soil was analyzed based on a comparison of models and observations. Cesium-137 migration from the organic layer to the underlying mineral soil was represented by a two-component exponential model. Cesium-137 migration from the organic layer was faster than that observed in European forests, suggesting that the mobility and bioavailability of 137Cs could be suppressed rapidly in Japanese forests. At all sites, 137Cs transfer in mineral soil could be reproduced by a simple diffusion equation model with continuous 137Cs supply from the organic layer. The diffusion coefficients of 137Cs in the mineral soil were estimated to be 0.042-0.55 cm2 y-1, which were roughly comparable with those of European forest soils affected by the Chernobyl Nuclear Power Plant accident. Model predictions using the determined model parameters indicated that 10 years after the accident, more than 70% of the deposited 137Cs will migrate to the mineral soil but only less than 10% of the total 137Cs inventory will penetrate deeper than 10 cm in the mineral soil across all sites. The results of the present study suggest that the 137Cs deposited onto Japanese forest ecosystems will be retained in the surface layers of mineral soil for a long time.
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Affiliation(s)
- Kotomi Muto
- 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
| | - Takeshi Matsunaga
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan
| | - Jun Koarashi
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
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Ayabe Y, Yoshida T, Kanasashi T, Hayashi A, Fukushi A, Hijii N, Takenaka C. Web-building spider Nephila clavata (Nephilidae: Arachnida) can represent 137Cs contamination of arthropod communities and bioavailable 137Cs in forest soils at Fukushima, Japan. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 687:1176-1185. [PMID: 31412453 DOI: 10.1016/j.scitotenv.2019.06.158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/22/2019] [Accepted: 06/10/2019] [Indexed: 06/10/2023]
Abstract
Large areas of Fukushima's forests were contaminated with radiocesium (137Cs) after the Fukushima Dai-ichi Nuclear Power Plant accident. Most of the contaminated forests have not been decontaminated, and bioavailable 137Cs is likely to circulate within the forest environment's food web. Nephila clavata (Nephilidae: Arachnida) is a top predator in the forest arthropod community, and this web-building spider potentially consumes many arthropod species presented in the grazing and detrital food chains. We tested whether 137Cs in the spider could serve as a proxy for 137Cs contamination of these arthropod communities. We also examined whether N. clavata could serve as a proxy for soil bioavailable 137Cs. Nephila clavata was similarly or more contaminated with 137Cs compared with lower-trophic-level arthropods such as herbivores and other predators at the same trophic level. Thus, the 137Cs activity of N. clavata could represent the extent to which the arthropod community was contaminated with 137Cs. Data from nine 137Cs-contaminated sites in Fukushima showed a significant positive correlation between soil bioavailable 137Cs and N. clavata's 137Cs activity05 but the coefficient of determination was only moderate (R2 = 0.43), suggesting that N. clavata is only a weak proxy of soil bioavailable 137Cs. Our results also showed that the bioavailable fraction of 137Cs in Fukushima was strongly correlated with the total inventory and that the K and Na contents of the soil determined the soil-to-spider transfer factor for 137Cs and the 137Cs activity in N. clavata, respectively. These results improve our understanding of 137Cs transfer from the soil to arthropod species.
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Affiliation(s)
- Yoshiko Ayabe
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Tomohiro Yoshida
- Field Science Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan.
| | - Tsutomu Kanasashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Akane Hayashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Akihisa Fukushi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Naoki Hijii
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Chisato Takenaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
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Yoshihara T, Yoschenko V, Watanabe K, Keitoku K. A through year behavior of 137Cs in a Japanese flowering cherry tree in relation to that of potassium. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 202:32-40. [PMID: 30776701 DOI: 10.1016/j.jenvrad.2019.01.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/09/2019] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
To understand the transfer of radiocesium (137Cs) in inside of deciduous trees, changes in 137Cs activity concentrations, primarily derived from the Fukushima accident in March 2011, were observed in the upper parts of a Japanese flowering cherry tree (Prunus x yedoensis cv. Somei-Yoshino) between 2015 and 2018. The sampling of the foliar parts occurred over the entire leaf life span from winter bud to litterfall and those of the branches were distinguished based on emergence years (2017, 2016, 2015, 2014-2011, and 2010/before). First, every tissue demonstrated a clear seasonal variation in 137Cs activity concentration. Second, a synchrony of seasonal variations in 137Cs activity concentration with those in the biological analogue of K concentration was observed in foliar parts during their growth season, but not in branches nor during the other seasons. With respect to the timing of changes in each tissue with tree phenology, it is possible that K and 137Cs alternate between leaves and branches via the same translocation mechanisms. The resorption efficiencies (i.e., 1 - [the concentrations in the last litterfall]/[the maximum concentrations in green leaves]) of K and 137Cs were 76% and 46% in average, respectively. In addition, both leaf buds and branches played an important role as reservoirs during dormancy. The buds storage ratio before and after bud burst (i.e., [the inventories in buds at the end of defoliation]/[those before and after bud burst]) for K were 0.57 and 0.10 in median, respectively, and those for and 137Cs were 1.14 and 0.14 in median, respectively. Consequently, the transfer of 137Cs in inside of trees was still visible seven years after deposition, even though the annual reduction in 137Cs activity concentration was apparent in each tissue.
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Affiliation(s)
- Toshihiro Yoshihara
- Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba, 270-1194, Japan.
| | - Vasyl Yoschenko
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan
| | - Kenji Watanabe
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan
| | - Koji Keitoku
- Institute of Environmental Radioactivity of Fukushima University (IER), 1 Kanayagawa, Fukushima, Fukushima, 960-1296, Japan; Minamisoma City Hall, Odaka Ward Community Promotion Division, 2-28 Moto-machi Odaka, Minami Soma, Fukushima, 979-2195, Japan
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18
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Low 137Cs retention capability of organic layers in Japanese forest ecosystems affected by the Fukushima nuclear accident. J Radioanal Nucl Chem 2019. [DOI: 10.1007/s10967-019-06435-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Zehringer M, Kammerer F, Wagmann M. Radionuclides in tea and their behaviour in the brewing process. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 192:75-80. [PMID: 29890360 DOI: 10.1016/j.jenvrad.2018.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/31/2018] [Accepted: 06/02/2018] [Indexed: 06/08/2023]
Abstract
Tea plantations may be strongly affected by radioactive fallout. Tea plantations on the Turkish coast of the Black Sea were heavily contaminated by the fallout from the reactor fire at the Chernobyl nuclear power plant in 1986. Two years later, the contamination level was reduced by about 90%. When tea is brewed, the original contamination in the tea leaves is more or less leached into the tea water. While most of the radiocaesium (60-80%) is washed out by brewing, most of the radiostrontium remains in the leaves (70-80%). In food laws, a dilution factor of 40-50 is considered for tea brewing. Most laws only define limit values for radiocaesium. Radiostrontium is not specially regulated, even though its dose coefficients for ingestion are higher than the corresponding coefficients for radiocaesium. Radiostrontium in tea occurs primarily from global fallout (bomb tests from 1945-1965).
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Affiliation(s)
- Markus Zehringer
- State-Laboratory Basel-City, Kannenfeldstrasse 2, CH-4056 Basel, Switzerland.
| | - Franziska Kammerer
- State-Laboratory Basel-City, Kannenfeldstrasse 2, CH-4056 Basel, Switzerland
| | - Michael Wagmann
- State-Laboratory Basel-City, Kannenfeldstrasse 2, CH-4056 Basel, Switzerland
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20
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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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Koarashi J, Atarashi-Andoh M, Matsunaga T, Sanada Y. Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident. Sci Rep 2016; 6:38591. [PMID: 27974832 PMCID: PMC5156898 DOI: 10.1038/srep38591] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 11/08/2016] [Indexed: 11/16/2022] Open
Abstract
The Fukushima Daiichi nuclear power plant disaster caused serious radiocesium (137Cs) contamination of forest ecosystems over a wide area. Forest-floor organic layers play a key role in controlling the overall bioavailability of 137Cs in forest ecosystems; however, there is still an insufficient understanding of how forest types influence the retention capability of 137Cs in organic layers in Japanese forest ecosystems. Here we conducted plot-scale investigations on the retention of 137Cs in organic layers at two contrasting forest sites in Fukushima. In a deciduous broad-leaved forest, approximately 80% of the deposited 137Cs migrated to mineral soil located below the organic layers within two years after the accident, with an ecological half-life of approximately one year. Conversely, in an evergreen coniferous forest, more than half of the deposited 137Cs remained in the organic layers, with an ecological half-life of 2.1 years. The observed retention behavior can be well explained by the tree phenology and accumulation of 137Cs associated with litter materials with different degrees of degradation in the organic layers. Spatial and temporal patterns of gamma-ray dose rates depended on the retention capability. Our results demonstrate that enhanced radiation risks last longer in evergreen coniferous forests than in deciduous broad-leaved forests.
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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
| | - Takeshi Matsunaga
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan
| | - Yukihisa Sanada
- Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima 975-0036, Japan
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Danchenko M, Klubicova K, Krivohizha MV, Berezhna VV, Sakada VI, Hajduch M, Rashydov NM. Systems biology is an efficient tool for investigation of low-dose chronic irradiation influence on plants in the Chernobyl zone. CYTOL GENET+ 2016. [DOI: 10.3103/s0095452716060050] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Yoshihara T, Matsumura H, Hashida SN, Nakaya K. Radiocesium contamination in living and dead foliar parts of Japanese cedar during 2011-2015. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 164:291-299. [PMID: 27537824 DOI: 10.1016/j.jenvrad.2016.08.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 07/27/2016] [Accepted: 08/07/2016] [Indexed: 06/06/2023]
Abstract
Radiocesium (137Cs) activity concentrations, mainly derived from the Fukushima accident of March 2011, were measured in green foliar parts without separation by age (bulk green foliar parts; GL) and litterfall (LF) of Japanese cedar (Cryptomeria japonica) from 2011 to 2015. In all samples, 137Cs concentrations decreased exponentially over time, but were always higher in LF (7.36-0.58 Bq g-DW-1) than in GL (2.10-0.06 Bq g-DW-1). The difference in the decreasing rate between GL and LF would reflect a difference in the dominant factor of the decrease between living and dead tissues (i.e., internal translocation and weathering, respectively). Over this same timeframe, potassium (K) concentrations in both GL and LF experienced repetitive periodical changes within a certain range (0.38-3.0 mg g-DW-1 for LF and 2.08-4.77 mg g-DW-1 for GL, respectively). Thus, there was no specific correlation between 137Cs and K concentrations in LF and GL. However, analyses of the age classified green foliar parts (GL-S) and dead foliar parts still retained on trees (DL) could indicate another view. The annual changes in residual rates of both 137Cs and K concentrations in GL-S demonstrated very similar two-phase reductions (i.e., a faster reduction in each expansion year than in the following years) and an obvious linear correlation between each other. Radiocesium concentration in DL were always higher than in any part of GL-S sampled at the same timing, but K concentrations showed the reverse relation. It is probable that 137Cs is basically translocated from older parts to the developing parts (as long as the former are alive) via a seasonal nutritional flow of K; however, a part of 137Cs translocation would cease considerably earlier than the cessation of K translocation.
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Affiliation(s)
- Toshihiro Yoshihara
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
| | - Hideyuki Matsumura
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Shin-Nosuke Hashida
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Ko Nakaya
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
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Hashida SN, Yoshihara T. Disparate radiocesium leaching from two woody species by acceleration of litter decomposition using microbial inoculation. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 162-163:319-327. [PMID: 27323212 DOI: 10.1016/j.jenvrad.2016.06.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 06/10/2016] [Accepted: 06/12/2016] [Indexed: 06/06/2023]
Abstract
Studies focusing on the migration of radionuclides in the forest floor have demonstrated that the ecological half-life of radiocesium on organic layer containing the debris of plant litter with various fungi and microorganisms is shorter than that in the deeper soil zone, suggesting that the litter decomposition affects radiocesium mobilization. Here, we showed the involvement of lignin, one of the major cell wall components of plant litter, in the fate of contaminated radiocesium during the process of fungal litter decomposition. In this study, litter decomposition of two different woody species, broadleaf deciduous Japanese cherry consisted of hardwood lignin and coniferous evergreen Japanese cedar with softwood lignin, were accelerated by in vitro fungal inoculation. In vitro inoculation exhibited 1.93- to 2.59-times faster decomposition than field experiment. Then, the cherry litter lost approximately 25% of initially contaminated radiocesium within 1 month of in vitro decomposition, whereas the cedar litter kept initial level at least for 6 month. The retention of radiocesium correlated with thioglycolate lignin content in cedar litter but not in cherry litter. Consequently, the behavior of radiocesium contaminated in litter fall may vary depending on the contamination pathway or the manner of nutrient mobilization at the stage of abscission between evergreen and deciduous trees.
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Affiliation(s)
- Shin-Nosuke Hashida
- Plant Molecular Biology, Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), Abiko 1646, Abiko-shi, Chiba, Japan.
| | - Toshihiro Yoshihara
- Plant Molecular Biology, Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), Abiko 1646, Abiko-shi, Chiba, Japan
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26
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Komatsu M, Kaneko S, Ohashi S, Kuroda K, Sano T, Ikeda S, Saito S, Kiyono Y, Tonosaki M, Miura S, Akama A, Kajimoto T, Takahashi M. Characteristics of initial deposition and behavior of radiocesium in forest ecosystems of different locations and species affected by the Fukushima Daiichi Nuclear Power Plant accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 161:2-10. [PMID: 26432062 DOI: 10.1016/j.jenvrad.2015.09.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 08/15/2015] [Accepted: 09/15/2015] [Indexed: 06/05/2023]
Abstract
After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, information about stand-level spatial patterns of radiocesium initially deposited in the surrounding forests was essential for predicting the future dynamics of radiocesium and suggesting a management plan for contaminated forests. In the first summer (approximately 6 months after the accident), we separately estimated the amounts of radiocesium ((134)Cs and (137)Cs; Bq m(-2)) in the major components (trees, organic layers, and soils) in forests of three sites with different contamination levels. For a Japanese cedar (Cryptomeria japonica) forest studied at each of the three sites, the radiocesium concentration greatly differed among the components, with the needle and organic layer having the highest concentrations. For these cedar forests, the proportion of the (137)Cs stock in the aboveground tree biomass varied from 22% to 44% of the total (137)Cs stock; it was 44% in highly contaminated sites (7.0 × 10(5) Bq m(-2)) but reduced to 22% in less contaminated sites (1.1 × 10(4) Bq m(-2)). In the intermediate contaminated site (5.0-5.8 × 10(4) Bq m(-2)), 34% of radiocesium was observed in the aboveground tree biomass of the Japanese cedar stand. However, this proportion was considerably smaller (18-19%) in the nearby mixed forests of the Japanese red pine (Pinus densiflora) and deciduous broad-leaved trees. Non-negligible amounts of (134)Cs and (137)Cs were detected in both the sapwood and heartwood of all the studied tree species. This finding suggested that the uptake or translocation of radiocesium had already started within 6 months after the accident. The belowground compartments were mostly present in the organic layer and the uppermost (0-5 cm deep) mineral soil layer at all the study sites. We discussed the initial transfer process of radiocesium deposited in the forest and inferred that the type of initial deposition (i.e., dry versus wet radiocesium deposition), the amount of rainfall after the accident, and the leaf biomass by the tree species may influence differences in the spatial pattern of radiocesium by study plots. The results of the present study and further studies of the spatial pattern of radiocesium are important for modeling future radiocesium distribution in contaminated forest ecosystems.
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Affiliation(s)
- Masabumi Komatsu
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
| | - Shinji Kaneko
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Shinta Ohashi
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Katsushi Kuroda
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Tetsuya Sano
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Department of Environment and Energy, Tohoku Institute of Technology, 35-1 Yagiyamakasumi-cho, Taihaku-ku, Sendai, Miyagi 982-8577, Japan
| | - Shigeto Ikeda
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Satoshi Saito
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Yoshiyuki Kiyono
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Mario Tonosaki
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Shikoku Research Center, Forestry and Forest Products Research Institute, 2-915 Asakuranishimachi, Kochi, Kochi 780-8077, Japan
| | - Satoru Miura
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Laboratory of Radioplant Physiology, the University of Tokyo, 1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Akio Akama
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Takuya Kajimoto
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Masamichi Takahashi
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
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27
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Thiry Y, Garcia-Sanchez L, Hurtevent P. Experimental quantification of radiocesium recycling in a coniferous tree after aerial contamination: Field loss dynamics, translocation and final partitioning. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 161:42-50. [PMID: 26774824 DOI: 10.1016/j.jenvrad.2015.12.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 12/18/2015] [Accepted: 12/19/2015] [Indexed: 06/05/2023]
Abstract
After foliar interception of radioactive atmospheric fallout by forest trees, the short-term recycling dynamics of radiocesium from the tree to the soil as well as within the tree is a primary area of uncertainty in the modeling of the overall cycle. The partitioning of radiocesium transfers in a spruce tree exposed to aerial deposits was investigated during one growth season to reveal the dynamics and significance of underlying processes. The rate of radiocesium loss resulting from foliage leaching (wash-off) was shown to have a functional dependence on the frequency of rainy episodes in a first early stage (weathering 60% of initial contamination during 70 days) and on the amount of precipitation in a second stage (weathering 10% of initial deposits during the following 80 days). A classical single exponential decay model with offset and continuous time as predictor lead to a removal half-life t1/2 of intercepted radiocesium of 25 days. During the growth season, the similar pattern of the internal (134)Cs content in new shoots and initially contaminated foliage confirmed that radiocesium was readily absorbed from needle surfaces and efficiently translocated to growing organs. In the crown, a pool of non-leachable (134)Cs (15-30%) was associated with the abiotic layer covering the twigs and needle surfaces. At the end of the growth season, 30% of the initial deposits were relocated to different tree parts, including organs like stemwood (5%) and roots (6%) not directly exposed to deposition. At the scale of the tree, 84% of the residual activity was assimilated by living tissues which corresponds to a foliar absorption rate coefficient of 0.25 year(-1) for modeling purposes. According to the significant amount of radiocesium which can be incorporated in tree through foliar uptake, our results support the hypothesis that further internal transfers could supply the tree internal cycle of radiocesium extensively, and possibly mask the contribution of root uptake for a long time.
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Affiliation(s)
- Y Thiry
- National Radioactive Waste Management Agency (Andra), Scientific Division, 1-7, rue Jean Monnet, 92298 Châtenay-Malabry Cedex, France.
| | - L Garcia-Sanchez
- French Institute for Radiological Protection and Nuclear Safety (IRSN), PRP-ENV/SERIS/L2BT, CE Cadarache bt 183, BP 3, 13115 Saint-Paul-lez-Durance, France.
| | - P Hurtevent
- French Institute for Radiological Protection and Nuclear Safety (IRSN), PRP-ENV/SERIS/L2BT, CE Cadarache bt 183, BP 3, 13115 Saint-Paul-lez-Durance, France.
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28
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Sugiura Y, Shibata M, Ogata Y, Ozawa H, Kanasashi T, Takenaka C. Evaluation of radiocesium concentrations in new leaves of wild plants two years after the Fukushima Dai-ichi Nuclear Power Plant accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 160:8-24. [PMID: 27116401 DOI: 10.1016/j.jenvrad.2016.04.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 04/12/2016] [Accepted: 04/15/2016] [Indexed: 06/05/2023]
Abstract
Radiocesium ((137)Cs) transfer to plants immediately after the Fukushima Dai-ichi Nuclear Power Plant accident was investigated by collecting newly emerged leaf and soil samples between May 2011 and November 2012 from 20 sites in the Fukushima prefecture. Radiocesium concentrations in leaf and soil samples were measured to calculate concentration ratios (CR). Woody plants exhibited high CR values because (137)Cs deposited on stems and/or leaves were transferred to newly emerging tissues. The CR values in 2012 declined as compared to that in 2011. Exchangeable (137)Cs rates in soil (extraction rate) samples were measured at five sites. These rates decreased at four sites in 2012 and depended on environmental conditions and soil type. Both CR values and extraction rates decreased in 2012. However, CR values reflected the changes in extraction rates and characteristics of each species. Amaranthaceae, Chenopodiaceae, and Polygonaceae, which had been identified as Cs accumulators, presented no clear (137)Cs accumulation ability. In 2012, the perennial plant Houttuynia cordata and deciduous trees Chengiopanax sciadophylloides and Acer crataegifolium displayed high CR values, indicating that these species are (137)Cs accumulators and may be considered as potential species for phytoremediation.
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Affiliation(s)
- Yuki Sugiura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan.
| | - Michihiro Shibata
- Radioisotope Research Center, Nagoya University, Nagoya, Aichi 464-8602, Japan.
| | - Yoshimune Ogata
- Graduate School of Medicine, Nagoya University, Nagoya, Aichi 466-8550, Japan.
| | - Hajime Ozawa
- Fukushima Prefectural Forestry Research Centre, Koriyama, Fukushima 963-0112, Japan.
| | - Tsutomu Kanasashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan.
| | - Chisato Takenaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan.
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29
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Okuda M, Akao T, Sumihiro M, Mizuno M, Goto-Yamamoto N. Transfer of caesium and potassium from Japanese apricot (Prunus mume Sieb.et Zucc.) to Japanese apricot liqueur (Umeliqueur). JOURNAL OF THE INSTITUTE OF BREWING 2016. [DOI: 10.1002/jib.346] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Masaki Okuda
- National Research Institute of Brewing; Higashihiroshima Japan
| | - Takeshi Akao
- National Research Institute of Brewing; Higashihiroshima Japan
| | | | - Megumi Mizuno
- National Research Institute of Brewing; Higashihiroshima Japan
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30
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Kanasashi T, Takenaka C, Sugiura Y. Inferring the chemical form of 137Cs deposited by the Fukushima Dai-ichi Nuclear Power Plant accident by measuring (137)Cs incorporated into needle leaves and male cones of Japanese cedar trees. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 553:643-649. [PMID: 26990074 DOI: 10.1016/j.scitotenv.2016.02.118] [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: 10/18/2015] [Revised: 02/17/2016] [Accepted: 02/17/2016] [Indexed: 06/05/2023]
Abstract
We hypothesized that the water-soluble (ionic) and water-insoluble (stable) radiocesium from the initial fallout of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident was distributed in various proportions in the surrounding areas and that this distribution was reflected in the trees that suffered deposition from the initial fallout. This study attempted to evaluate local variations in the chemical form of (137)Cs derived from the initial fallout of the FDNPP accident and whether its chemical form affected the radiocesium concentration in the tissues currently growing in trees, even after the initial fallout ceased. For these estimations, the ratio between the (137)Cs concentration in Cryptomeria japonica needle leaves in the tree crown, which existed before the FDNPP accident and subsequently directly exposed to the initial fallout ((137)Cs pre-accident N), and the amount of (137)Cs in the initial fallout itself ((137)Cs fallout) was determined ((137)Cs pre-accident N/(137)Cs fallout) at 66 sites. In addition, the (137)Cs ratios between the male cones produced in 2012 ((137)Cs male cone) and needle leaves that had elongated in the spring of 2011 ((137)Cs 2011N) was determined at 82 sites ((137)Cs male cone/(137) Cs 2011N). Most of the sites with lower (137)Cs pre-accident N /(137)Cs fallout ratios were distributed in eastern Fukushima, relatively close to the Pacific Ocean coastline. Lower (137)Cs pre-accident N/(137)Cs fallout and higher (137)Cs malecone/(137)Cs 2011N were found to be associated with higher proportions of (137)Cs in ionic forms. These observations are consistent with the hypothesis, and likely reflect regional variations in the chemical form of the deposited radiocesium.
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Affiliation(s)
- Tsutomu Kanasashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan.
| | - Chisato Takenaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
| | - Yuki Sugiura
- Japan Atomic Energy Agency, 765-1 Funaishikawa, Tokai-mura, Naka-gun, Ibaraki 319-1184, Japan
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31
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Xu S, Cook GT, Cresswell AJ, Dunbar E, Freeman SPHT, Hou X, Kinch H, Naysmith P, Sanderson DWC, Zhang L. Carbon, cesium and iodine isotopes in Japanese cedar leaves from Iwaki, Fukushima. J Radioanal Nucl Chem 2016; 310:927-934. [PMID: 27746518 PMCID: PMC5042993 DOI: 10.1007/s10967-016-4830-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Indexed: 11/17/2022]
Abstract
Japanese cedar leaves from Iwaki, Fukushima were analyzed for carbon, cesium and iodine isotopic compositions before and after the 2011 nuclear accident. The Δ14C values reflect ambient atmospheric 14C concentrations during the year the leaves were sampled/defoliated, and also previous year(s). The elevated 129I and 134,137Cs concentrations are attributed to direct exposure to the radioactive fallout for the pre-fallout-expended leaves and to internal translocation from older parts of the tree for post-fallout-expended leaves. 134Cs/137Cs and 129I/137Cs activity ratios suggest insignificant isotopic and elemental fractionation during translocation. However, fractionation between radioiodine and radiocesium is significant during transportation from the source.
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Affiliation(s)
- Sheng Xu
- Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF UK
- Fukushima University, Fukushima, 960-1296 Japan
| | - Gordon T. Cook
- Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF UK
| | - Alan J. Cresswell
- Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF UK
- Fukushima University, Fukushima, 960-1296 Japan
| | - Elaine Dunbar
- Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF UK
| | | | - Xiaolin Hou
- Center for Nuclear Technologies, Technical University of Denmark, 4000 Roskilde, Denmark
| | - Helen Kinch
- Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF UK
| | - Philip Naysmith
- Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF UK
| | | | - Luyuan Zhang
- Center for Nuclear Technologies, Technical University of Denmark, 4000 Roskilde, Denmark
- Xi’an AMS Center, SKLLQG, Institute of Earth Environment, CAS, Xi’an, 710061 China
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32
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Hirono Y, Nonaka K. Time series changes in radiocaesium distribution in tea plants (Camellia sinensis (L.)) after the Fukushima Dai-ichi Nuclear Power Plant accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 152:119-126. [PMID: 26695880 DOI: 10.1016/j.jenvrad.2015.10.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 10/14/2015] [Accepted: 10/15/2015] [Indexed: 06/05/2023]
Abstract
Radiocaesium ((134)Cs and (137)Cs) release following the accident at the Fukushima Dai-ichi Nuclear Power Plant, belonging to the Tokyo Electric Power Company caused severe contamination of new tea plant (Camellia sinensis (L.)) shoots by radiocaesium in many prefectures in eastern Japan. Because tea plants are perennial crops, there is the fear that the contamination might last for a long time. The objectives of this study were to reveal time series changes in the distribution of radiocaesium in tea plants after radioactive fallout and to evaluate the effect of pruning on reduction of radiocaesium concentrations in new shoots growing next year. The experimental tea field was located in Shizuoka, Japan, approximately 400 km away from the Fukushima Dai-ichi Nuclear Power Plant in a southwest direction. Time series changes in radiocaesium concentrations in unrefined tea, a tea product primarily produced for making Japanese green tea, from May 2011 to June 2013 and distribution of radiocaesium in tea plants from May 2011 to May 2012 were monitored. The radiocaesium concentrations in unrefined tea exponentially decreased; the effective half-lives for (134)Cs and (137)Cs were 0.30 and 0.36 y during the first 2 y after the accident, respectively. With time, the highest concentrations of (137)Cs moved from the upper to the lower parts of plants. Medium pruning 2-3 months after the accident reduced the concentration of (137)Cs in new shoots harvested in the first crop season of the following year by 56% compared with unpruned tea plants; thus, pruning is an effective measure for reducing radiocaesium concentration in tea.
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Affiliation(s)
- Yuhei Hirono
- National Agriculture and Food Research Organization (NARO), 2769, Kanaya-Shishidoi, Shimada, Shizuoka 428-8501, Japan.
| | - Kunihiko Nonaka
- National Agriculture and Food Research Organization (NARO), 2769, Kanaya-Shishidoi, Shimada, Shizuoka 428-8501, Japan
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33
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Sugiura Y, Kanasashi T, Ogata Y, Ozawa H, Takenaka C. Radiocesium accumulation properties of Chengiopanax sciadophylloides. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 151 Pt 1:250-257. [PMID: 26536624 DOI: 10.1016/j.jenvrad.2015.10.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 10/20/2015] [Accepted: 10/22/2015] [Indexed: 06/05/2023]
Abstract
Through the assessments of radioactive contamination after the Fukushima Dai-ichi Nuclear Power Plant (F1NPP) accident, it has been reported that some sprouts of Chengiopanax sciadophylloides (Franch. et Sav.) at the site contained radiocesium (((134),)(137)Cs) at higher concentrations than the other plants. To assess the phytoremediation properties of C. sciadophylloides for (137)Cs decontamination, we aimed to quantify the (137)Cs accumulation in C. sciadophylloides. We measured the (137)Cs concentrations in various organs of C. sciadophylloides collected from the forest in the town of Kawamata, Fukushima prefecture, together with the concentrations of other elements [potassium (K), rubidium, (133)Cs, calcium, strontium, and manganese] present. In addition, we compared the foliar concentrations of these elements in C. sciadophylloides with those in four different deciduous tree species. The mean of foliar (137)Cs concentration in C. sciadophylloides was 28.1 kBq kg(-1) DW, one order of magnitude higher than that found in the other species. The (137)Cs concentrations were in the order of leaves > bark > wood. The wood of the treetop, leaf scars, and roots contained higher amounts of (137)Cs than that of the trunk. From the distribution of (137)Cs in C. sciadophylloides, we confirmed that (137)Cs tends to accumulate in the young growing parts. The difference in the distribution of (137)Cs and (133)Cs indicated that surface uptake of (137)Cs occurs. A significant correlation between K and (137)Cs concentrations in each organ was found, which suggested that (137)Cs in the plant body is transferred through the same pathway as K. On the other hand, there was no correlation between foliar K and (137)Cs concentrations, implying that the uptake ratio of K to (137)Cs was different for each individual. To determine the factors driving specific (137)Cs accumulation and/or the variability of the ratio between K and (137)Cs, the distribution of (137)Cs and the root in soil, the difference of the expression of transporter, and the existence of mycorrhizal fungi should be considered. However, further research is required.
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Affiliation(s)
- Yuki Sugiura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan.
| | - Tsutomu Kanasashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan.
| | - Yoshimune Ogata
- Graduate School of Medicine, Nagoya University, Nagoya, Aichi 461-8673, Japan.
| | - Hajime Ozawa
- Fukushima Prefectural Forestry Research Centre, Koriyama, Fukushima 963-0112, Japan.
| | - Chisato Takenaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan.
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34
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Endo I, Ohte N, Iseda K, Tanoi K, Hirose A, Kobayashi NI, Murakami M, Tokuchi N, Ohashi M. Estimation of radioactive 137-cesium transportation by litterfall, stemflow and throughfall in the forests of Fukushima. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2015; 149:176-185. [PMID: 26330021 DOI: 10.1016/j.jenvrad.2015.07.027] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/10/2015] [Accepted: 07/26/2015] [Indexed: 06/05/2023]
Abstract
Since the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011, large areas of the forests around Fukushima have become highly contaminated by radioactive nuclides. To predict the future dynamics of radioactive cesium ((137)Cs) in the forest catchment, it is important to measure each component of its movement within the forest. Two years after the accident, we estimated the annual transportation of (137)Cs from the forest canopy to the floor by litterfall, throughfall and stemflow. Seasonal variations in (137)Cs transportation and differences between forests types were also determined. The total amount of (137)Cs transported from the canopy to the floor in two deciduous and cedar plantation forests ranged between 3.9 and 11.0 kBq m(-2) year(-1). We also observed that (137)Cs transportation with litterfall increased in the defoliation period, simply because of the increased amount of litterfall. (137)Cs transportation with throughfall and stemflow increased in the rainy season, and (137)Cs flux by litterfall was higher in cedar plantation compared with that of mixed deciduous forest, while the opposite result was obtained for stemflow.
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Affiliation(s)
- Izuki Endo
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
| | - Nobuhito Ohte
- Graduate School of Informatics, Kyoto University, 36-1 Hon-cho, Yoshida Sakyo-ku, Kyoto, 606-8501, Japan
| | - Kohei Iseda
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Keitaro Tanoi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Atsushi Hirose
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Natsuko I Kobayashi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Masashi Murakami
- Department of Biology, Faculty of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba City, 263-8522, Japan
| | - Naoko Tokuchi
- Field Science Education and Research Center, Kyoto University, Ashiu Forest Research Station, Ashiu, Miyama-cho, Nantan City, Kyoto, 601-0703, Japan
| | - Mizue Ohashi
- School of Human Science and Environment, University of Hyogo, 1-1-12 Shinzaike-honcho, Himeji City, Hyogo, 670-0092, Japan
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35
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Tagami K, Uchida S. Effective half-lives of ¹³⁷Cs from persimmon tree tissue parts in Japan after Fukushima Dai-ichi Nuclear Power Plant accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2015; 141:8-13. [PMID: 25500061 DOI: 10.1016/j.jenvrad.2014.11.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 11/19/2014] [Accepted: 11/27/2014] [Indexed: 06/04/2023]
Abstract
To estimate the radiocesium decreasing rates from persimmon trees during a period of about 3 y following the accident at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant (FDNPP), we conducted measurements of tree tissue parts collected in 2011-2013. The sampling was carried out in Chiba, 220 km south of FDNPP; radioactive fallouts discharged from FDNPP had mainly been observed in March-April 2011 on the sampling site. We measured (137)Cs concentrations in the tree tissue parts, i.e., fruits (flesh, skin and seeds), leaves and newly emerged branches, and then the effective half-lives (T(eff)) of (137)Cs were calculated. Leaf samples were classified into two types by sampling months according to the growing stages, that is, immature (April-May) and mature (June-November) leaves. All these parts showed exponential declines in (137)Cs concentration with good adjusted contribution ratios of higher than ca. 0.7. The calculated T(eff) values from all tissue parts were similar with the average of 229 d (range: 216-243 d). From these results, we concluded that each tree tissue was representative for the calculation of Teff. For comparison to these observation results, open source food monitoring data from 2011 to 2013 including (137)Cs data for persimmon fruits collected in Fukushima Prefecture were used to calculate T(eff) for persimmon trees. Values of Teff were obtained for persimmon fruits grown in each local government area in Fukushima Prefecture and they ranged from 303 to 475 d.
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Affiliation(s)
- Keiko Tagami
- Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-7444, Japan.
| | - Shigeo Uchida
- Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-7444, Japan
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36
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Wróbel Ł, Dołhańczuk-Śródka A, Kłos A, Ziembik Z. The activity concentration of post-Chernobyl ¹³⁷Cs in the area of the Opole Anomaly (southern Poland). ENVIRONMENTAL MONITORING AND ASSESSMENT 2015; 187:4084. [PMID: 25389020 DOI: 10.1007/s10661-014-4084-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 10/28/2014] [Indexed: 06/04/2023]
Abstract
During the years 2007 and 2010, the activity concentration of (137)Cs accumulated in soil, mosses Pleurozium schreberi and lichens Hypogymnia physodes was measured. The studies covered the areas of the so-called Opole Anomaly. In consequence of the Chernobyl nuclear power plant breakdown in 1986, relatively large amounts of this radionuclide were deposited in this area. In some areas of the Anomaly, over 100 times higher surface activity of (137)Cs was detected, compared to the lowest values registered in Poland. Currently, (137)Cs is still present in woodlands and wastelands. As at 2 April 2013, the surface activity concentration of (137)Cs in soil on the tested area was from 0.34 to 67.5 kBq m(-2). In comparison, the surface activity concentration of (137)Cs as at 1 June 1986, soon after deposition, was from 2.08 to over 125 kBq m(-2). The maximum specific activity concentrations of (137)Cs in mosses and lichens sampled for testing in 2010 were respectively 1234 and 959 Bq kg(-1). It was also proven that the changes in activity concentration of (137)Cs in the area of the Anomaly are mainly the consequence of the radioactive decay of this radionuclide.
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Affiliation(s)
- Łukasz Wróbel
- Biotechnology and Molecular Biology, Opole University, ul. kard. B. Kominka 6, 45-035, Opole, Poland,
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Nishikiori T, Watanabe M, Koshikawa MK, Takamatsu T, Ishii Y, Ito S, Takenaka A, Watanabe K, Hayashi S. Uptake and translocation of radiocesium in cedar leaves following the Fukushima nuclear accident. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 502:611-616. [PMID: 25302448 DOI: 10.1016/j.scitotenv.2014.09.063] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/19/2014] [Accepted: 09/19/2014] [Indexed: 06/04/2023]
Abstract
Cryptomeria japonica trees in the area surrounding Fukushima, Japan, intercepted (137)Cs present in atmospheric deposits soon after the Fukushima nuclear accident in March 2011. To study the uptake and translocation of (137)Cs in C. japonica leaves, we analyzed activity concentrations of (137)Cs and the concentration ratios of (137)Cs to (133)Cs ((137)Cs/(133)Cs) in old and new leaves of C. japonica collected from a forest on Mount Tsukuba between 9 and 15 months after the accident. Both isotopes were also analyzed in throughfall, bulk precipitation and soil extracts. Water of atmospheric and soil origin were used as proxies for deciphering the absorption from leaf surfaces and root systems, respectively. Results indicate that 20-40% of foliar (137)Cs existed inside the leaf, while 60-80% adhered to the leaf surface. The (137)Cs/(133)Cs ratios inside leaves that had sprouted before the accident were considerably higher than that of the soil extract and lower than that of throughfall and bulk precipitation. Additionally, more than 80% of (137)Cs in throughfall and bulk precipitation was present in the dissolved form, which is available for foliar uptake, indicating that a portion of the (137)Cs inside old leaves was presumably absorbed from the leaf surface. New leaves that sprouted after the accident had similar (137)Cs/(133)Cs ratios to that of the old leaves, suggesting that internal (137)Cs was translocated from old to new leaves. For 17 species of woody plants other than C. japonica, new leaves that sprouted after the accident also contained (137)Cs, and their (137)Cs/(133)Cs ratios were equal to or higher than that of the soil extract. These results suggested that foliar uptake and further translocation of (137)Cs is an important vector of contamination in various tree species during or just after radioactive fallout.
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Affiliation(s)
- Tatsuhiro Nishikiori
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Mirai Watanabe
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
| | - Masami K Koshikawa
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Takejiro Takamatsu
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Yumiko Ishii
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Shoko Ito
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Akio Takenaka
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Keiji Watanabe
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan; Center for Environmental Science in Saitama, 914 Kamitanadare, Kazo, Saitama 347-0115, Japan
| | - Seiji Hayashi
- Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
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Yoshihara T, Matsumura H, Tsuzaki M, Wakamatsu T, Kobayashi T, Hashida SN, Nagaoka T, Goto F. Changes in radiocesium contamination from Fukushima in foliar parts of 10 common tree species in Japan between 2011 and 2013. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 138:220-226. [PMID: 25261868 DOI: 10.1016/j.jenvrad.2014.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 08/26/2014] [Accepted: 09/03/2014] [Indexed: 06/03/2023]
Abstract
Yearly changes in radiocesium ((137)Cs) contamination, primarily due to the Fukushima accident of March 2011, were observed in the foliar parts of 10 common woody species in Japan (Chamaecyparis obtusa, Cedrus deodara, Pinus densiflora, Cryptomeria japonica, Phyllostachys pubescens, Cinnamomum camphora, Metasequoia glyptostroboides, Prunus × yedoensis, Acer buergerianum, and Aesculus hippocastanum). The samples were obtained from Abiko (approximately 200 km SSW of the Fukushima Dai-ichi Nuclear Power Plant) during each growing season between 2011 and 2013, and the foliar parts were examined based on their year of expansion and location in each trees. The radiocesium concentrations generally decreased with time; however, the concentrations and rates of decrease varied among species, age of foliar parts, and locations. The radiocesium concentrations in the 2012 current-year foliar parts were 29%-220% of those from 2011, while those from 2013 fell to between 14% and 42% of the 2011 values. The net decontamination in the foliage was higher in evergreen species than in deciduous species. The radiocesium concentrations in the upper foliar parts were higher than those in the lower parts particularly in C. japonica. In addition, the radiocesium concentrations were higher in the current-year foliar parts than in the 1-year-old foliar parts, particularly in 2013. Thus, the influence of the direct deposition of the fallout was reduced with time, and the translocation ability of radiocesium from old to new tissues became more influential. Similar to the behavior of potassium in trees, Cs redistribution probably occurred primarily due to internal nutrient translocation mechanisms.
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Affiliation(s)
- Toshihiro Yoshihara
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
| | - Hideyuki Matsumura
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Masaharu Tsuzaki
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Takashi Wakamatsu
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Takuya Kobayashi
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Shin-Nosuke Hashida
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Toru Nagaoka
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Fumiyuki Goto
- Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
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Bolsunovsky A, Dementyev D. Radioactive contamination of pine (Pinus sylvestris) in Krasnoyarsk (Russia) following fallout from the Fukushima accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 138:87-91. [PMID: 25201085 DOI: 10.1016/j.jenvrad.2014.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 08/05/2014] [Accepted: 08/07/2014] [Indexed: 06/03/2023]
Abstract
Following the Fukushima accident in March 2011, samples of pine trees (Pinus sylvestris) were collected from three sites near the city of Krasnoyarsk (Siberia, Russia) during 2011-2012 and analyzed for artificial radionuclides. Concentrations of Fukushima-derived radionuclides in the samples of pine needles in April 2011 reached 5.51 ± 0.52 Bq kg(-1)(131)I, 0.92 ± 0.04 Bq kg(-1)(134)Cs, and 1.51 ± 0.07 Bq kg(-1)(137)Cs. An important finding was the detection of (134)Cs from the Fukushima accident not only in the pine needles and branches but also in the new shoots in 2012, which suggested a transfer of Fukushima cesium isotopes from branches to shoots. In 2011 and 2012, the (137)Cs/(134)Cs ratio for pine needles and branches collected in sampling areas Krasnoyarsk-1 and Krasnoyarsk-2 was greater than 1 (varying within a range of 1.2-2.6), suggesting the presence of "older", pre-Fukushima accident (137)Cs. Calculations showed that for pine samples growing in areas of the Krasnoyarskii Krai unaffected by contamination from the nuclear facility, the activity of the Fukushima-derived cesium isotopes was two-three times higher than the activity of the pre-accident (137)Cs.
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Affiliation(s)
- A Bolsunovsky
- Institute of Biophysics, Siberian Branch of Russian Academy of Sciences, 50-50 Akademgorodok, Krasnoyarsk 660036, Russia.
| | - D Dementyev
- Institute of Biophysics, Siberian Branch of Russian Academy of Sciences, 50-50 Akademgorodok, Krasnoyarsk 660036, Russia
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40
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Nakai W, Okada N, Ohashi S, Tanaka A. Evaluation of 137Cs accumulation by mushrooms and trees based on the aggregated transfer factor. J Radioanal Nucl Chem 2014. [DOI: 10.1007/s10967-014-3729-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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41
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Koarashi J, Atarashi-Andoh M, Takeuchi E, Nishimura S. Topographic heterogeneity effect on the accumulation of Fukushima-derived radiocesium on forest floor driven by biologically mediated processes. Sci Rep 2014; 4:6853. [PMID: 25358420 PMCID: PMC4215300 DOI: 10.1038/srep06853] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 10/10/2014] [Indexed: 11/19/2022] Open
Abstract
The accident at the Fukushima Daiichi nuclear power plant caused serious radiocesium (137Cs) contamination of forest ecosystems located in mountainous and hilly regions with steep terrain. To understand topographic effects on the redistribution and accumulation of 137Cs on forest floor, we investigated the distribution of Fukushima-derived 137Cs in forest-floor litter layers on a steep hillslope in a Japanese deciduous forest in August 2013 (29 months after the accident). Both leaf-litter materials and litter-associated 137Cs were accumulated in large amounts at the bottom of the hillslope. At the bottom, a significant fraction (65%) of the 137Cs inventory was observed to be associated with newly shed and less degraded leaf-litter materials, with estimated mean ages of 0.5–1.5 years, added via litterfall after the accident. Newly emerged leaves were contaminated with Fukushima-derived 137Cs in May 2011 (two months after the accident) and 137Cs concentration in them decreased with time. However, the concentrations were still two orders of magnitude higher than the pre-accident level in 2013 and 2014. These observations are the first to show that 137Cs redistribution on a forested hillslope is strongly controlled by biologically mediated processes and continues to supply 137Cs to the bottom via litterfall at a reduced rate.
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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
| | - Erina Takeuchi
- 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
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42
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Oya Y, Uchimura H, Toda K, Ikka T, Morita A, Okuno K. Dissolution behavior of 137Cs absorbed on the green tea leaves. J Radioanal Nucl Chem 2014. [DOI: 10.1007/s10967-014-3549-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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43
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Taira W, Nohara C, Hiyama A, Otaki JM. Fukushima's Biological Impacts: The Case of the Pale Grass Blue Butterfly. J Hered 2014; 105:710-22. [DOI: 10.1093/jhered/esu013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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44
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Ohashi S, Okada N, Tanaka A, Nakai W, Takano S. Radial and vertical distributions of radiocesium in tree stems of Pinus densiflora and Quercus serrata 1.5 y after the Fukushima nuclear disaster. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 134:54-60. [PMID: 24661964 DOI: 10.1016/j.jenvrad.2014.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 03/04/2014] [Accepted: 03/04/2014] [Indexed: 06/03/2023]
Abstract
The radial and vertical distributions of radiocesium in tree stems were investigated to understand radiocesium transfer to trees at an early stage of massive contamination from the Fukushima nuclear disaster. A conifer species (Japanese red pine) and a broad-leaved species (Japanese konara oak) were selected to determine whether the radiocesium contamination pattern differs between species. Stem disks were collected at several heights and separated into outer bark, inner bark, and wood. The radiocesium concentration was the highest in the outer bark, followed by that in the inner bark and wood. The vertical distribution of the radiocesium concentration at each stem part differed between the species. The difference between species in radiocesium concentration of the outer bark could be explained by presence or absence of leaves at the time of the disaster. However, the reasons for the differences between species in the radiocesium concentration of the inner bark and wood are unclear. The radial distribution in the wood of the studied species showed a common pattern across stem disk heights and species. However, the radiocesium concentration ratio between sapwood and inner bark was significantly different between species. Although the radial contamination pattern in the wood was similar in the studied species during the early stage of contamination, the radiocesium transport pathway and allocation would be different between the species, and the contamination pattern will likely be different between the species at later stages. Continued investigations are important for understanding the radiocesium cycle and the accumulation of radiocesium in the tree stems of each species.
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Affiliation(s)
- Shinta Ohashi
- Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
| | - Naoki Okada
- Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Kyoto 606-8501, Japan
| | - Atsushi Tanaka
- Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Kyoto 606-8501, Japan
| | - Wataru Nakai
- Department of Forest and Biomaterials Science, Faculty of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Shigeyoshi Takano
- Department of Forest and Biomaterials Science, Faculty of Agriculture, Kyoto University, Kyoto 606-8502, Japan
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45
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Higaki T, Higaki S, Hirota M, Hasezawa S. Radiocesium distribution in bamboo shoots after the Fukushima nuclear accident. PLoS One 2014; 9:e97659. [PMID: 24831096 PMCID: PMC4022665 DOI: 10.1371/journal.pone.0097659] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 04/21/2014] [Indexed: 11/18/2022] Open
Abstract
The distribution of radiocesium was examined in bamboo shoots, Phyllostachys pubescens, collected from 10 sites located some 41 to 1140 km from the Fukushima Daiichi nuclear power plant, Japan, in the Spring of 2012, 1 year after the Fukushima nuclear accident. Maximum activity concentrations for radiocesium ¹³⁴Cs and ¹³⁷Cs in the edible bamboo shoot parts, 41 km away from the Fukushima Daiichi plant, were in excess of 15.3 and 21.8 kBq/kg (dry weight basis; 1.34 and 1.92 kBq/kg, fresh weight), respectively. In the radiocesium-contaminated samples, the radiocesium activities were higher in the inner tip parts, including the upper edible parts and the apical culm sheath, than in the hardened culm sheath and underground basal parts. The radiocesium/potassium ratios also tended to be higher in the inner tip parts. The radiocesium activities increased with bamboo shoot length in another bamboo species, Phyllostachys bambusoides, suggesting that radiocesium accumulated in the inner tip parts during growth of the shoots.
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Affiliation(s)
- Takumi Higaki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba, Japan
- * E-mail:
| | - Shogo Higaki
- Radioisotope Center, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, Japan
| | - Masahiro Hirota
- Research Center for Human and Environmental Sciences, Shinshu University, Matsumoto, Nagano, Japan
| | - Seiichiro Hasezawa
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba, Japan
- Advanced Measurement and Analysis, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo, Japan
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46
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Nohara C, Hiyama A, Taira W, Tanahara A, Otaki JM. The biological impacts of ingested radioactive materials on the pale grass blue butterfly. Sci Rep 2014; 4:4946. [PMID: 24844938 PMCID: PMC4027884 DOI: 10.1038/srep04946] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 04/22/2014] [Indexed: 11/25/2022] Open
Abstract
A massive amount of radioactive materials has been released into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident, but its biological impacts have rarely been examined. Here, we have quantitatively evaluated the relationship between the dose of ingested radioactive cesium and mortality and abnormality rates using the pale grass blue butterfly, Zizeeria maha. When larvae from Okinawa, which is likely the least polluted locality in Japan, were fed leaves collected from polluted localities, mortality and abnormality rates increased sharply at low doses in response to the ingested cesium dose. This dose-response relationship was best fitted by power function models, which indicated that the half lethal and abnormal doses were 1.9 and 0.76 Bq per larva, corresponding to 54,000 and 22,000 Bq per kilogram body weight, respectively. Both the retention of radioactive cesium in a pupa relative to the ingested dose throughout the larval stage and the accumulation of radioactive cesium in a pupa relative to the activity concentration in a diet were highest at the lowest level of cesium ingested. We conclude that the risk of ingesting a polluted diet is realistic, at least for this butterfly, and likely for certain other organisms living in the polluted area.
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Affiliation(s)
- Chiyo Nohara
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science
| | - Atsuki Hiyama
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science
| | - Wataru Taira
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science
| | - Akira Tanahara
- Instrumental Research Center, University of the Ryukyus, Okinawa 903-0213, Japan
| | - Joji M. Otaki
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science
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47
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Nakajima H, Fujiwara M, Tanihata I, Saito T, Matsuda N, Todo T. Imaging plant leaves to determine changes in radioactive contamination status in Fukushima, Japan. HEALTH PHYSICS 2014; 106:565-570. [PMID: 24670905 DOI: 10.1097/hp.0000000000000020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The chemical composition of plant leaves often reflects environmental contamination. The authors analyzed images of plant leaves to investigate the regional radioactivity ecology resulting from the 2011 accident at the Fukushima No. 1 nuclear power plant, Japan. The present study is not an evaluation of the macro radiation dose per weight, which has been performed previously, but rather an image analysis of the radioactive dose per leaf, allowing the capture of various gradual changes in radioactive contamination as a function of elapsed time. In addition, the leaf analysis method has potential applications in the decontamination of food plants or other materials.
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Affiliation(s)
- Hiroo Nakajima
- *Department of Radiation Biology and Medical Genetics, Graduate School of Medicine; †Research Center for Nuclear Physics; ‡Radioisotope Research Center, Osaka University; §Headquarters of Fukushima Partnership Operations, Japan Atomic Energy Agency
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48
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Hashimoto S, Matsuura T, Nanko K, Linkov I, Shaw G, Kaneko S. Predicted spatio-temporal dynamics of radiocesium deposited onto forests following the Fukushima nuclear accident. Sci Rep 2014; 3:2564. [PMID: 23995073 PMCID: PMC3759142 DOI: 10.1038/srep02564] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 08/13/2013] [Indexed: 11/25/2022] Open
Abstract
The majority of the area contaminated by the Fukushima Dai-ichi nuclear power plant accident is covered by forest. To facilitate effective countermeasure strategies to mitigate forest contamination, we simulated the spatio-temporal dynamics of radiocesium deposited into Japanese forest ecosystems in 2011 using a model that was developed after the Chernobyl accident in 1986. The simulation revealed that the radiocesium inventories in tree and soil surface organic layer components drop rapidly during the first two years after the fallout. Over a period of one to two years, the radiocesium is predicted to move from the tree and surface organic soil to the mineral soil, which eventually becomes the largest radiocesium reservoir within forest ecosystems. Although the uncertainty of our simulations should be considered, the results provide a basis for understanding and anticipating the future dynamics of radiocesium in Japanese forests following the Fukushima accident.
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Affiliation(s)
- Shoji Hashimoto
- Department of Forest Site Environment, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, Japan.
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Yoshihara T, Hashida SN, Abe K, Ajito H. A time dependent behavior of radiocesium from the Fukushima-fallout in litterfalls of Japanese flowering cherry trees. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 127:34-39. [PMID: 24125903 DOI: 10.1016/j.jenvrad.2013.09.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 09/19/2013] [Accepted: 09/20/2013] [Indexed: 06/02/2023]
Abstract
Radiocesium ((134)Cs + (137)Cs) concentrations, primarily derived from the Fukushima accident in March 2011, were measured in litterfalls and green leaves of Japanese flowering cherry trees (Prunus x yedoensis cv. Somei-Yoshino). The sampling was performed mainly during the defoliation season in 2011 and 2012 using traps to collect litterfalls before contact with the ground. The average radiocesium concentration in litterfalls in 2012 fell to one-third of that in 2011 (0.43 and 1.2 kBq kg-DW(-1), respectively). Interestingly, the concentrations in litterfalls collected in late autumn in both 2011 and 2012 (0.68 and 0.19 kBq kg-DW(-1), respectively) were significantly lower than those in litterfalls collected in the early autumn (1.7 and 1.1 kBq kg-DW(-1), respectively). In addition, the reductions in radiocesium concentrations in the litterfall were nearly synchronous with those in potassium concentrations (p ≤ 0.05). On the contrary, radiocesium concentrations in green leaves were also correlated with potassium concentrations; however, the slopes of the regression lines between the radiocesium and potassium concentrations were very similar in the 2011 litterfalls and the 2012 litterfalls, while the slopes were significantly different between these litterfalls and the green leaves. Consequently, the correlation between potassium and radiocesium was clear but independently observable in each of the litterfalls and the green leaves. It is possible that the reduction in radiocesium concentration occurred as a part of physiological demand, a translocation of potassium from the leaves to the body/twigs.
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Affiliation(s)
- Toshihiro Yoshihara
- Plant Molecular Biology, Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
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Mimura T, Mimura M, Kobayashi D, Komiyama C, Sekimoto H, Miyamoto M, Kitamura A. Radioactive pollution and accumulation of radionuclides in wild plants in Fukushima. JOURNAL OF PLANT RESEARCH 2014; 127:5-10. [PMID: 24317752 DOI: 10.1007/s10265-013-0599-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 09/03/2013] [Indexed: 05/23/2023]
Abstract
The radionuclide status of wild plants and soil in the Fukushima area was investigated during the period May 2011 to October 2012, using an imaging plate (autoradiograms) or a high purity germanium detector. Analyses of autoradiograms showed that wild plants grown in March 2011 were strongly polluted with fallout released from the Fukushima 1 Nuclear Power Plant. The radioactivity was mostly due to fallout adsorbed on the surface of the plants. On the other hand, a number of herbaceous plants were regularly collected in the Fukushima area and their radionuclide concentrations were measured with a high-purity germanium detector. Plants grown in March 2011 showed very high levels of ¹³⁴Cs and ¹³⁷Cs, but these radioactivity levels decreased rapidly after July 2011 and eventually became lower than that of endogenous ⁴⁰K. During this period, the radioactivity of the soil remained high. We therefore suppose that a significant proportion of the radioactivity detected from plants harvested after July 2011 was most likely derived from soil dust attached on the plant surface. Autoradiograms of rice plants were virtually identical between plants cultivated in Fukushima and Osaka area, reflecting the background radiation due to ⁴⁰K.
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Affiliation(s)
- Tetsuro Mimura
- Department of Biology, Graduate School of Science, Kobe University, Rokkodai, Nada, Kobe, 657-8501, Japan,
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