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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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Cladonia verticillaris (lichen) can exhibit defense mechanisms against Rn-222 under controlled conditions. J Radioanal Nucl Chem 2022. [DOI: 10.1007/s10967-022-08430-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Dohi T, Iijima K, Machida M, Suno H, Ohmura Y, Fujiwara K, Kimura S, Kanno F. Accumulation mechanisms of radiocaesium within lichen thallus tissues determined by means of in situ microscale localisation observation. PLoS One 2022; 17:e0271035. [PMID: 35802691 PMCID: PMC9269901 DOI: 10.1371/journal.pone.0271035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 06/22/2022] [Indexed: 11/19/2022] Open
Abstract
Many lichens are well known to accumulate radiocaesium and, thus acting as biomonitors of contamination levels. However, the actual localisation and chemical forms of radiocaesium in contaminated lichens have not yet been elucidated because, despite their high radioactivity, these forms are present in trace amounts as chemical entities. Here, we use autoradiography and demonstrate for the first time in situ microscale localisation of radiocaesium within thallus tissues to investigate the radiocaesium forms and their accumulation mechanism. Radiocaesium distributions showed similar trends in lichen tissues collected two and six years after the Fukushima nuclear accident. The radiocaesium was localised in the brown pigmented parts i.e., melanin-like substances, in the lower cortex of lichen thallus. Quantum chemical calculations showed that functional group of melanin-like substances can chelate Cs+ ion, which indicates that the Cs+ ions form complexes with the substances. Based on these findings, we suggest that radiocaesium ions may be retained stably in melanin-like substances for long periods (two to six years) due to steric factors, such as those seen in porphyrin-like structures and via multimer formation in the lower cortex. In addition, electron microscopy and autoradiography were used to observe radiocaesium-bearing microparticles (CsMPs) on/in the upper cortex and around the medullary layer. Micron-sized particles appeared to adhere to the surface tissue of the thallus, as shown by electron microscopy, suggesting that the particles were trapped by development of an adhesive layer; that is, CsMPs were trapped both physically and physiologically. These findings provide information on in situ localisation of two chemical forms of radiocaesium, cations and particles, in lichen thallus tissues and their accumulation mechanisms.
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Affiliation(s)
- Terumi Dohi
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, Miharu-town, Fukushima, Japan
- * E-mail:
| | - Kazuki Iijima
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, Miharu-town, Fukushima, Japan
| | - Masahiko Machida
- Center for Computational Science & e-Systems (CCSE), Japan Atomic Energy Agency, Kashiwa-city, Chiba, Japan
| | - Hiroya Suno
- Center for Computational Science & e-Systems (CCSE), Japan Atomic Energy Agency, Kashiwa-city, Chiba, Japan
| | - Yoshihito Ohmura
- Department of Botany, National Museum of Nature and Science, Tsukuba-city, Ibaraki, Japan
| | - Kenso Fujiwara
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, Miharu-town, Fukushima, Japan
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Anderson J, Lévesque N, Caron F, Beckett P, Spiers GA. A review on the use of lichens as a biomonitoring tool for environmental radioactivity. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 243:106797. [PMID: 34968948 DOI: 10.1016/j.jenvrad.2021.106797] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 12/10/2021] [Accepted: 12/11/2021] [Indexed: 06/14/2023]
Abstract
Lichens have been widely used as a biomonitoring tool to record the distribution and concentration of airborne radioactivity and pollutants such as metals. There are limitations, however: although pollutants can be preserved in lichen tissues for long periods of time, not all radioactive and inert elements behave similarly. The chemical species of elements at the source, once captured, and the mode of storage within lichens play a role in this biomonitoring tool. Lichens are a symbiotic association of an algal or cyanobacterial partner (photobiont) with a fungal host (mycobiont). Lichens grow independently of the host substrates, including rocks, soils, trees and human-made structures. Lacking a root system, lichen nutrient or contaminant uptake is mostly through direct atmospheric inputs, mainly as wet and dry deposition. As lichens grow in a large variety of environments and are resilient in harsh climates, they are adapted to capture and retain nutrients from airborne sources. The context of this review partially relates to future deployment of small modular reactors (SMRs) and mining in remote areas of Canada. SMRs have been identified as a future source of energy (electricity and heat) for remote off-grid mines, potentially replacing diesel fuel generation facilities. For licensing purposes, SMR deployment and mine development requires capabilities to monitor background contaminants (natural radioactivity and metals) before, during and after deployment, including for decommissioning and removal. Key aspects reviewed herein include: (1) how lichens have been used in the past to monitor radioactivity; (2) radiocontaminants capture and storage in lichens; (3) longevity of radiocontaminant storage in lichen tissues; and (4) limitations of lichens use for monitoring radiocontaminants and selected metals.
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Affiliation(s)
- J Anderson
- Mirarco Mining Innovation and Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada; Harquail School of Earth Sciences, Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada
| | - N Lévesque
- Mirarco Mining Innovation and Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada; School of Biological, Chemical & Forensic Sciences, Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada
| | - F Caron
- Mirarco Mining Innovation and Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada.
| | - P Beckett
- Vale Living with Lakes Centre, Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada
| | - G A Spiers
- Harquail School of Earth Sciences, Laurentian University, 935 Ramsey Lake Rd., Sudbury, ON, P3E 2C6, Canada
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