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Sakauchi K, Otaki JM. Imaging Plate Autoradiography for Ingested Anthropogenic Cesium-137 in Butterfly Bodies: Implications for the Biological Impacts of the Fukushima Nuclear Accident. Life (Basel) 2023; 13:life13051211. [PMID: 37240856 DOI: 10.3390/life13051211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/12/2023] [Accepted: 05/16/2023] [Indexed: 05/28/2023] Open
Abstract
The Fukushima nuclear accident in March 2011 caused biological impacts on the pale grass blue butterfly Zizeeria maha. At least some of the impacts are likely mediated by the host plant, resulting in "field effects". However, to obtain the whole picture of the impacts, direct exposure effects should also be evaluated. Here, we examined the distribution of experimentally ingested anthropogenic cesium-137 (137Cs) in adult butterfly bodies using imaging plate autoradiography. We showed that 137Cs ingested by larvae was incorporated into adult bodies and was biased to females, although the majority of ingested 137Cs was excreted in the pupal cuticle and excretory material during eclosion. 137Cs accumulation in adult bodies was the highest in the abdomen, followed by the thorax and other organs. These results suggest that 137Cs accumulation in reproductive organs may cause adverse transgenerational or maternal effects mediated by reactive oxygen species (ROS) on germ cells. 137Cs accumulation was detected in field individuals collected in September 2011 and September 2016 but not in May 2011, which is consistent with the abnormality dynamics known from previous studies. Taken together, these results contribute to an integrative understanding of the multifaceted biological effects of the Fukushima nuclear accident in the field.
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Affiliation(s)
- Ko Sakauchi
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara 903-0213, Okinawa, Japan
| | - Joji M Otaki
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara 903-0213, Okinawa, Japan
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Fuciarelli TM, Rollo CD. Ionizing radiation alters male Acheta domesticus courtship songs that are critical for mating success. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.06.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Kim TY, Lee SH, Lee SY. Two newly identified Haematococcus strains efficiently accumulated radioactive cesium over higher astaxanthin production. ENVIRONMENTAL RESEARCH 2021; 199:111301. [PMID: 33984306 DOI: 10.1016/j.envres.2021.111301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 05/05/2021] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
In this study, we investigated the morphological, genomic and bioaccumulation characteristics of two isolated Haematococcus strains (namely Goyang and Sogang), which were newly discovered in South Korea. Morphological analysis revealed that the isolated strains were unicellular and bi-flagellated green microalgae that formed thickened walls at the palmelloid or red-cyst phase. Phylogenetic analysis of 18S rRNA and rbcL gDNA sequences demonstrated that both strains were taxonomically related to the genus Haematococcus. The two strains showed growth pattern that was similar to a typical Haematococcus strain, and accumulated astaxanthin within 48 h of exposure to intensive light. Both red-cyst cells effectively removed radioactive cesium to more than 50% within 48 h from low-level cesium-contaminated water of 5 Bq/ml concentration. The cesium-accumulation mechanism is largely associated with the replacement of cellular potassium in thick cell walls during biouptake, and the cesium-removal rate highly depends on the corresponding astaxanthin accumulation involving the potassium-transporting protein (P-type ATPase).
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Affiliation(s)
- Tae Yoon Kim
- Department of Biomedical Engineering, Sogang University, Baekbeom-ro 35, Mapo-gu, Seoul, Republic of Korea
| | - Sang-Hyo Lee
- Department of Biomedical Engineering, Sogang University, Baekbeom-ro 35, Mapo-gu, Seoul, Republic of Korea
| | - Seung-Yop Lee
- Department of Biomedical Engineering, Sogang University, Baekbeom-ro 35, Mapo-gu, Seoul, Republic of Korea; Department of Mechanical Engineering, Sogang University, Baekbeom-ro 35, Mapo-gu, Seoul, Republic of Korea.
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Tanaka S, Kakinuma H, Adati T, Atarashi-Andoh M, Koarashi J. Transfer of 137Cs to web-building spiders, Nephila clavata, and its pathways: a preliminary study using stable carbon and nitrogen isotope analyses. J NUCL SCI TECHNOL 2021. [DOI: 10.1080/00223131.2021.1894255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Sota Tanaka
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan
| | - Hotaru Kakinuma
- Department of International Agricultural Development, Faculty of International Agriculture and Food Studies, Tokyo University of Agriculture, Tokyo, Japan
| | - Tarô Adati
- Department of International Agricultural Development, Faculty of International Agriculture and Food Studies, Tokyo University of Agriculture, Tokyo, Japan
| | - Mariko Atarashi-Andoh
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan
| | - Jun Koarashi
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan
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Nutrient Imbalance of the Host Plant for Larvae of the Pale Grass Blue Butterfly May Mediate the Field Effect of Low-Dose Radiation Exposure in Fukushima: Dose-Dependent Changes in the Sodium Content. INSECTS 2021; 12:insects12020149. [PMID: 33572324 PMCID: PMC7916146 DOI: 10.3390/insects12020149] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 01/27/2021] [Accepted: 02/05/2021] [Indexed: 12/21/2022]
Abstract
The pale grass blue butterfly Zizeeria maha is sensitive to low-dose radioactive pollution from the Fukushima nuclear accident in the field but is also highly tolerant to radioactive cesium (137Cs) in an artificial diet in laboratory experiments. To resolve this field-laboratory paradox, we hypothesize that the butterfly shows vulnerability in the field through biochemical changes in the larval host plant, the creeping wood sorrel Oxalis corniculata, in response to radiation stress. To test this field-effect hypothesis, we examined nutrient contents in the host plant leaves from Tohoku (mostly polluted areas including Fukushima), Niigata, and Kyushu, Japan. Leaves from Tohoku showed significantly lower sodium and lipid contents than those from Niigata. In the Tohoku samples, the sodium content (but not the lipid content) was significantly negatively correlated with the radioactivity concentration of cesium (137Cs) in leaves and with the ground radiation dose. The sodium content was also correlated with other nutrient factors. These results suggest that the sodium imbalance of the plant may be caused by radiation stress and that this nutrient imbalance may be one of the reasons that this monophagous butterfly showed high mortality and morphological abnormalities in the field shortly after the accident in Fukushima.
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Anderson D, Beresford NA, Ishiniwa H, Onuma M, Nanba K, Hinton TG. Radiocesium concentration ratios and radiation dose to wild rodents in Fukushima Prefecture. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 226:106457. [PMID: 33227677 DOI: 10.1016/j.jenvrad.2020.106457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 10/04/2020] [Accepted: 11/04/2020] [Indexed: 06/11/2023]
Abstract
Radiocesium was dispersed from the Fukushima Dai-ichi disaster in March 2011, causing comparatively high radioactive contamination in nearby environments. Radionuclide concentrations in wild rodents (Apodemus argenteus, and Apodemus speciosus) within these areas were monitored from 2012 to 2016. However, whole-organism to soil transfer parameters (i.e., concentration ratio, CRwo-soil) for wild rodents at Fukushima were not determined and hence were lacking from the international transfer databases. We augmented the 2012-2016 data by collecting soil activity concentrations (Bq kg-1, dry mass) from five rodent sampling sites in Fukushima Prefecture, and developed corresponding CRwo-soil values for radiocesium (134Cs and 137Cs) based on rodent radioactivity concentrations (Bq kg-1, fresh mass). The CRwo-soil were added to the Wildlife Transfer Database (WTD; http://www.wildlifetransferdatabase.org/), supporting the development of the International Commission on Radiological Protection's (ICRP) environmental protection framework, and increasing the WTD from 84 to 477 entries for cesium and Muridae ('Reference Rat'). Significant variation occurred in CRwo-soil values between study sites within Fukushima Prefecture. The geometric mean CRwo-soil, in this paper, was higher than that reported for Muridae species for Chernobyl. Radiocaesium absorbed dose rates were also estimated for wild rodents inhabiting the five Fukushima study sites and ranged from 1.3 to 33 μGy h-1. Absorbed dose rates decreased by a factor of two from 2012 to 2016. Dose rates in highly contaminated areas were within the ICRP derived consideration reference level for Reference Rat (0.1-1 mGy d-1), suggesting the possible occurrence of deleterious effects and need for radiological effect studies in the Fukushima area.
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Affiliation(s)
- Donovan Anderson
- Symbiotic Systems Science and Technology, Fukushima University, Fukushima, Fukushima City, Kanayagawa, 960-1248, Japan.
| | - Nicholas A Beresford
- UK Centre for Ecology & Hydrology, Lancaster Environment Center, Library Av., Bailrigg, Lancaster, LA1 4AP, UK
| | - Hiroko Ishiniwa
- Institute of Environmental Radioactivity, Fukushima University, Fukushima, Fukushima City, Kanayagawa, 960-1248, Japan
| | - Manabu Onuma
- Ecological Risk Assessment and Control Section, Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Ibaraki, 305-0053, Japan
| | - Kenji Nanba
- Symbiotic Systems Science and Technology, Fukushima University, Fukushima, Fukushima City, Kanayagawa, 960-1248, Japan; Institute of Environmental Radioactivity, Fukushima University, Fukushima, Fukushima City, Kanayagawa, 960-1248, Japan
| | - Thomas G Hinton
- Institute of Environmental Radioactivity, Fukushima University, Fukushima, Fukushima City, Kanayagawa, 960-1248, Japan; Centre for Environmental Radioactivity, CoE, Norwegian University of Life Sciences, Faculty for Environmental Sciences and Nature Research Management, 1430, Åas, Norway
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Iwasa M, Nakaya F, Kabeya H, Sato K, Ishikawa SI, Takahashi T. Radiocesium concentrations in invertebrates and their environmental media at two distances from the Fukushima Dai-ichi Nuclear Power Plant during 3-6 years after the 2011 accident. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 267:115657. [PMID: 33254726 DOI: 10.1016/j.envpol.2020.115657] [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: 05/16/2020] [Revised: 07/24/2020] [Accepted: 09/13/2020] [Indexed: 06/12/2023]
Abstract
Activity concentrations of the radioactive cesium (134Cs and 137Cs) were investigated in invertebrates at two sites of moderately high and higher air radiation dose rates, 14 km and 11 km distances, respectively, from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) from 2013 to 2016. At a14-km point, the 134+137Cs concentrations of soils in coniferous and broadleaf forests increased from 2013 to 2014, and thereafter declined until 2016. The 134+137Cs concentrations of the phytophagous beetle Anomala cuprea (Hope) rapidly decreased by 76.1% from 2013 to 2014, reflecting reduction in those of broadleaves. The 134+137Cs concentration levels of the carnivorous beetle Dolichus halensis (Schaller) showed a relatively low levels. The 137Cs concentrations of the necrophagous beetle Eusilpha japonica (Motshulsky) and coprophagous beetle Onthophagus lenzii (Harold) remained constant without reduction from 2013 to 2016. Average 134+137Cs concentrations throughout four years were the highest in the geophagous crustacean (Armadillidium vulgare Latreille), followed by necrophagous beetle and coprophagus beetle. The 134+137Cs concentrations in earthworms with gut contents were significantly correlated with those in soils at each habitat from 2014 to 2015 at a14-km point, and the concentration levels at an 11-km point in 2015 were remarkably high (898 kBq kg-1). Transfer factors (TFs) in earthworms ranged from 1.02 to 2.66 at a 14-km point and 0.66 to 5.0 at an11-km point. The transfer and chronological changes of radiocesium in invertebrates were discussed in relation to food habits through trophic levels in woodlands and pasturelands.
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Affiliation(s)
- Mitsuhiro Iwasa
- Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
| | - Fumiya Nakaya
- Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
| | - Hideyuki Kabeya
- Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
| | - Kosuke Sato
- Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
| | - Shin-Ichiro Ishikawa
- Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
| | - Teppei Takahashi
- Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
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Overwintering States of the Pale Grass Blue Butterfly Zizeeria maha (Lepidoptera: Lycaenidae) at the Time of the Fukushima Nuclear Accident in March 2011. INSECTS 2019; 10:insects10110389. [PMID: 31690046 PMCID: PMC6920751 DOI: 10.3390/insects10110389] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 10/31/2019] [Accepted: 11/01/2019] [Indexed: 01/02/2023]
Abstract
The Fukushima nuclear accident in March 2011 caused the massive release of anthropogenic radioactive materials from the Fukushima Dai-ichi Nuclear Power Plant to its surrounding environment. Its biological effects have been studied using the pale grass blue butterfly, Zizeeria maha (Lepidoptera: Lycaenidae), but the overwintering states of this butterfly remain elusive. Here, we conducted a series of field surveys in March 2018, March 2019, and April 2019 in Fukushima and its vicinity to clarify the overwintering states of this butterfly at the time of the Fukushima nuclear accident. We discovered overwintering individuals in situ associated with the host plant Oxalis corniculata under natural straw mulch as first-instar to fourth-instar larvae in March 2018 and 2019. No other developmental stages were found. The body length and width were reasonably correlated with the accumulated temperature. On the basis of a linear regression equation between body size and accumulated temperature, together with other data, we deduced that the pale grass blue butterfly occurred as fourth-instar larvae in Fukushima and its vicinity at the time of the accident. This study paves the way for subsequent dosimetric analyses that determine the radiation doses absorbed by the butterfly after the accident.
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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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Hu J, Chen S, Zhang N, Wang Z, Shi J, Guo Y, Deng T. Porous composite CMC–KCuFC–PEG spheres for efficient cesium removal from wastewater. NEW J CHEM 2019. [DOI: 10.1039/c9nj01697j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Highly stable porous composite CMC–KCuFC–PEG was used for Cs+ recovery from wastewater, and showed excellent adsorption performance.
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Affiliation(s)
- Jiayin Hu
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
| | - Shangqing Chen
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
| | - Ningluo Zhang
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
| | - Zheng Wang
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
| | - Jian Shi
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
| | - Yafei Guo
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
| | - Tianlong Deng
- Tianjin Key Laboratory of Marine Resources and Chemistry
- College of Chemical Engineering and Materials Science
- Tianjin University of Science and Technology
- Tianjin
- China
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Tanaka S, Adati T, Takahashi T, Fujiwara K, Takahashi S. Concentrations and biological half-life of radioactive cesium in epigeic earthworms after the Fukushima Dai-ichi Nuclear Power Plant accident. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 192:227-232. [PMID: 29986314 DOI: 10.1016/j.jenvrad.2018.06.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/08/2018] [Accepted: 06/26/2018] [Indexed: 06/08/2023]
Abstract
To understand the long-term behavior of radiocesium in the biological processes of a forest ecosystem, its concentration in Japanese epigeic earthworms (Megascolecidae), litter, and soil, and the ambient dose equivalent rates, were investigated after the Fukushima Dai-ichi Nuclear Power Plant accident. The metabolism of radiocesium in the earthworms was also investigated in the laboratory, and its biological half-life (Tb) was estimated. The concentration of 137Cs in the habitat soil and litter changed from 2014 to 2016, with levels in the litter going from 44.9 Bq/g dw (in 2014) to 45.3 Bq/g dw (2015) and 10.7 Bq/g dw (2016); in soil, these values were 9.79 Bq/g dw, 7.14 Bq/g dw and 18.0 Bq/g dw, respectively. By contrast, no significant changes were observed in the concentrations in the earthworms, which were 4.87 Bq/g fw, 5.30 Bq/g fw and 4.67 Bq/g fw in 2014, 2015, and 2016, respectively. The ambient dose equivalent rates at the sampling site declined significantly over these three years, going from 2.15 μSv/h to 1.68 μSv/h and 1.35 μSv/h, mostly corresponding to physical decay of radiocesium. The majority (95%) of the 137Cs in the earthworms, observed via autoradiography, was concentrated primarily in the intestine. The clearance of 137Cs from the earthworms was described by dual exponential functions: the half-life in the rapid loss due to gut clearance was 0.10 days and a second slower loss due to physiological clearance was 27.4 days.
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Affiliation(s)
- S Tanaka
- Kyoto University Graduate School of Agriculture, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
| | - T Adati
- Department of International Agricultural Development, Faculty of International Agriculture and Food Studies, Tokyo University of Agriculture, Sakuragaoka, Setagaya, 156-8502 Tokyo, Japan
| | - T Takahashi
- Kyoto University Graduate School of Agriculture, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; Division of Radiation Safety and Control, The Institute for Integrated Radiation and Nuclear Science, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - K Fujiwara
- Technical Staff Office, The Institute for Integrated Radiation and Nuclear Science, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - S Takahashi
- Division of Radiation Safety and Control, The Institute for Integrated Radiation and Nuclear Science, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
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