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Characterization of Natural and Affected Environments
Temporal variation of radionuclides contamination of marine plants on the Fukushima coast after the East Japan nuclear disaster Yu Shigeoka, Hiroshi Myouse, Seiji Akiyama, Akira Matsumoto, Naoto Hirakawa, Hideo Ohashi, Ken Higuchi, and Hisayuki ARAKAWA Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.9b01987 • Publication Date (Web): 16 Jul 2019 Downloaded from pubs.acs.org on July 21, 2019
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Environmental Science & Technology
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Title: Temporal variation of radionuclides contamination of marine plants on the Fukushima
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coast after the East Japan nuclear disaster.
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Authors: Yu Shigeoka†Ⅱ, Hiroshi Myose†, Seiji Akiyama†, Akira Matsumoto‡, Naoto
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Hirakawa§, Hideo Ohashi†, Ken Higuchi†, and Hisayuki Arakawa*†
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†Tokyo
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108-8477, Japan
University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo
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‡Soma
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Soma, Fukushima 976-0022, Japan
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§Fukushima
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Fukushima 970-0316, Japan
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Branch, Fukushima Prefectural Fisheries Experimental Station, 18-2 Oikawa, Obama,
Prefectural Fisheries Experimental Station, 13-2 Shimokajiro, Onahama, Iwaki,
Tokyo Kyuei Co. Ltd., 1-15, Nihonbashi-3, Chuo, Tokyo 103-0027, Japan.
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*Corresponding author; Hisayuki Arakawa,
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e-mail:
[email protected] 18 19 20
KEYWORDS: concentration factor · ecological half-life · Fukushima Daiichi Nuclear
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Power Plant · marine plants · 110mAg · 134Cs · 137Cs
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ABSTRACT As a result of the Great East Japan Earthquake and associated tsunami in March 2011, the
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Fukushima Daiichi Nuclear Power Plant (FDNPP) released a large amount of radioactive
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materials into the environment, resulting in contamination of many marine organisms. In this
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study, 15 marine algal and a seagrass species were collected from the sublittoral zone of the
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Iwaki Coast of Fukushima Prefecture from May 2012 to June 2015 and analysed for
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variations in 110mAg, 134Cs, and 137Cs with time. The results indicated that (1) 110mAg, 134Cs,
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and 137Cs were present in all marine plants collected in May 2012; (2) the concentration of
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110mAg
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ecological half-life of 110mAg in P. iwatensis was longer at locations closer to the FDNPP;
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and (3) the 110mAg/137Cs radioactivity ratio of P. iwatensis was remarkably high until 2015,
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indicating that detectable 110mAg was present in the coastal environment 4 years after the
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accident. The concentration of 110mAg in P. iwatensis was higher than those in other marine
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algae, demonstrating a species-specific mechanism of accumulation.
in the seagrass Phyllospadix iwatensis decreased significantly with time, while the
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Environmental Science & Technology
INTRODUCTION
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Large earthquakes and an associated tsunami in March 2011 resulted in an accident at
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the Fukushima Daiichi Nuclear Power Plant (FDNPP). Immediately after the accident, a high
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amount of radioactive materials was released into the atmosphere from the FDNPP, a large
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portion of which was deposited into the ocean1-3. In addition, a large amount of radioactive
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materials (e.g. 3.5–5.5 PBq in
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resulting in a high level of radiocaesium entering the sea4-9.
137Cs)
was released directly from the FDNPP into the ocean,
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Many marine organisms were contaminated by radioactive materials in direct inflow
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water from the FDNPP; therefore, monitoring of the radionuclides concentration of marine
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biota was started10-13. The main nuclides monitored were radioactive iodine (131I),
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radiocaesium (134Cs and
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were indeed detected in most marine organisms collected from the Fukushima coast
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immediately after the accident10. The levels of radiocaesium in fish and invertebrates
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decreased with time;14, 15 however, several independent studies have been conducted to study
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their concentrations in marine plants since the accident13, 14, 16, 17, 18, 19.
137Cs),
and radio silver (110mAg), and high levels of these materials
According to the Tokyo Electric Power Company (TEPCO)19, in addition to 134Cs and
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137Cs, 110mAg
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investigation of radioactive materials in coastal marine organisms following the accident. The
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110mAg
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and fish10, 11, 19; however, reports of these compounds were fragmentary and did not discuss
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changes in levels after the accident in detail.
was also detected in invertebrates and marine plants collected during
that originated from the FDNPP accident was also detected in other marine organisms
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Marine plants are important primary producers; accordingly, it is important to clarify
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the concentrations of radionuclides in marine plants and their changes because of the
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potential for plants to transfer radioactive materials in ecosystems. Therefore, in this study,
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the temporal changes and behaviour of radioactive materials concentrations of 110mAg, 134Cs, 3 ACS Paragon Plus Environment
Environmental Science & Technology
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and 137Cs in marine plants were investigated.
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MATERIALS AND METHODS
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Marine plants were collected from the sublittoral zones of Yotsukura coast (37.112°N,
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140.995°E; depth ca. 1 m) and Ena coast (36.971°N, 140.958°E; depth ca. 5 m) along the
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coastline of Iwaki in Fukushima Prefecture (Fig. 1), which are 35 km and 50 km south of the
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FDNPP (37.421°N, 141.034°E), respectively. The samples from Yotsukura were collected
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425 (May 2012), 496 (July 2012), 593 (October 2012), 639 (December 2012), 716 (February
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2013), 803 (May 2013), 940 (October 2013), 1041 (January 2014), 1172 (May 2014), and
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1557 (June 2015) days after the accident. Samples from Ena were collected 424 (May 2012),
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495 (July 2012), 593 (October 2012), 640 (December 2012), 717 (February 2013), 803 (May
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2013), 964 (October 2013), 1046 (January 2014), and 1174 (May 2014) days after the
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accident. The survey in June of 2015 was only conducted in Yotsukura. We randomly
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collected 2–6 species of marine plants in each survey and an amount sufficient for analysis.
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Overall, there were a total of 16 species (brown algae, 8 species: Ecklonia bicyclis,
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Sargassum
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siliquastrum, Sargassum horneri, Sargassum fulvellum, Sargassum miyabei; red algae, 7
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species: Gelidium elegans, Gloiopeltis furcata, Marginisporum aberrans, Grateloupia
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elliptica, Myelophycus simplex, Grateloupia turuturu, Ahnfeltiopsis paradoxa; seagrass, 1
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species: Phyllospadix iwatensis) represented by 83 samples.
micracanthum,
Undaria
pinnatifida,
Saccharina
japonica,
Sargassum
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The collected marine plants were immediately brought back to our laboratory and
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washed with artificial seawater (Instant Ocean, Napqo Ltd., Tokyo, Japan). Holdfasts of algae,
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and rhizoids and roots of seagrass were then removed from the sample. The samples were
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subsequently dried in an automatic oven at 60°C for 72 h, crushed, and then stored in a
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container until the concentrations of
110mAg, 134Cs,
and
137Cs
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were measured using a Ge
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Environmental Science & Technology
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semiconductor detector (GEM20-70 or GEM20, SEIKO EG&G Co. Ltd., Tokyo, Japan,
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GC4020 or GCW5323, CANBERRA Industries Inc., Meriden, CT, USA,
