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341 results on '"HAYASHI, Seiji"'

19. Dynamics of radiocaesium within forests in Fukushima—results and analysis of a model inter-comparison

Author

Hashimoto, Shoji, Tanaka, Taku, Komatsu, Masabumi, Gonze, Marc-André, Sakashita, Wataru, Kurikami, Hiroshi, Nishina, Kazuya, Ota, Masakazu, Ohashi, Shinta, Calmon, Philippe, Coppin, Frederic, Imamura, Naohiro, Hayashi, Seiji, Hirai, Keizo, Hurtevent, Pierre, Koarashi, Jun, Manaka, Takuya, Miura, Satoru, Shinomiya, Yoshiki, Shaw, George, and Thiry, Yves

Published
2021
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24. Exploring simple ways to avoid collecting highly 137Cs-contaminated Aralia elata buds for the revival of local wild vegetable cultures

Author

Sakai, Masaru, primary, Watanabe, Mirai, additional, Kanao Koshikawa, Masami, additional, Tanaka, Asuka, additional, Takahashi, Akiko, additional, Takechi, Seiichi, additional, Takagi, Mai, additional, Tsuji, Takashi, additional, Tsuji, Hideki, additional, Takeda, Toshimasa, additional, Jo, Jaeick, additional, Tamaoki, Masanori, additional, and Hayashi, Seiji, additional

Published
2024
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25. Impact of the 2019 typhoons on sediment source contributions and radiocesium concentrations in rivers draining the Fukushima radioactive plume, Japan

Author

Evrard, Olivier, Durand, Roxanne, Nakao, Atsushi, Patrick Laceby, J., Lefèvre, Irène, Wakiyama, Yoshifumi, Hayashi, Seiji, Asanuma-Brice, Cécile, and Cerdan, Olivier

Subjects
Source tracing, Sediment fingerprinting, Nuclear accident, Catchment, Cesium-137 ($^{137}$Cs), Geophysics. Cosmic physics, QC801-809, Chemistry, QD1-999, Geology, QE1-996.5
Abstract

The Fukushima nuclear accident in March 2011 generated a 3000 km$^{2}$ plume of soils heavily contaminated with $^{137}$Cs. Decontamination was completed early in 2019. Typhoon Hagibis was the first extreme event that occurred in the region after decontamination. Its impact on sediment sources and sediment $^{137}$Cs contamination was investigated through the application of a sediment fingerprinting procedure using spectrocolorimetry and geochemical properties. Sediment deposits ($n=24$) were collected in the Mano and Niida River catchments after the 2019 typhoons, and their signature was compared to that of potential sources (e.g., cropland, forests, and subsurface; $n=57$). Results demonstrate the dominance of cropland as the main source of sediment (mean: 54%) followed by forests (41%) with much lower contributions of subsurface material (5%). Overall, $^{137}$Cs concentrations in sediment were on average 84%–93% lower than the levels recorded after the accident in 2011, which demonstrates the effectiveness of cropland decontamination.

Published
2020
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35. Evaluation of bioavailable 137Cs transfer from forest litter to Scarabaeidae beetle (Protaetia orientalis) through a breeding experiment in Fukuhshima.

Author

Jo, Jaeick, Ishii, Yumiko, Saito, Rie, Tanaka, Asuka, and Hayashi, Seiji

Subjects
NUCLEAR power plant accidents, FOREST litter, SCARABAEIDAE, SOIL invertebrates, CLAY soils
Abstract

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, most of the released 137Cs remained in the litter and surface soil of the adjacent forest floor. However, 137Cs absorption by large soil invertebrates near this site has not been estimated. The aim of this study was to understand the role of soil macroinvertebrates in 137Cs uptake from forest litter into forest ecosystems. Breeding experiments were conducted using scarab beetle larvae (Protaetia orientalis). Dissection experiments revealed that 85% of the total 137Cs was concentrated in the digestive tract of larvae, while a low proportion was absorbed into the skin and muscle tissues. The 137Cs absorption rate, indicating the transfer of 137Cs from consumed litter to larval tissue, was low (0.39%). 137Cs concentrations decreased to one-fourth from larva to imago, possibly due to excretion from the digestive tract and during eclosion. In the elimination experiment, biological half-lives were 0.26–0.64 and 0.11–0.47 days and 3.35–48.30 and 4.01–17.70 days for the digestive tract and muscle/skin tissues in the fast and slow components, respectively, corresponding to 137Cs discharge from the gastrointestinal tract and physiological clearance. In the sequential extraction experiment, litter digestion by flower chafer larvae significantly reduced the bioavailable fraction of 137Cs including water-soluble, exchangeable, oxidized, and organic forms, from 23.2% in litter to 17.7% in feces. Residual 137Cs was not reduced by digestion, probably because it was fixed in soil clay. Our study on breeding experiments of the Scarabaeidae beetle confirmed the low bioavailability of 137Cs in the litter in Fukushima. However, litter feeders may play an important role in transferring 137Cs to higher trophic levels in the forest ecosystem by extracting the bioavailable fraction of the vast stock of 137Cs on the forest floor. [ABSTRACT FROM AUTHOR]

Published
2024
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43. Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

Author

Kurihara, Momo, Yasutaka, Tetsuo, Aono, Tatsuo, Ashikawa, Nobuo, Ebina, Hiroyuki, Iijima, Takeshi, Ishimaru, Kei, Kanai, Ramon, Karube, Zin’ichi, Konnai, Yae, Kubota, Tomijiro, Maehara, Yuji, Maeyama, Takeshi, Okizawa, Yusuke, Ota, Hiroaki, Otosaka, Shigeyoshi, Sakaguchi, Aya, Tagomori, Hisaya, Taniguchi, Keisuke, Tomita, Masatoshi, Tsukada, Hirofumi, Hayashi, Seiji, Lee, Sangyoon, Miyazu, Susumu, Shin, Moono, Nakanishi, Takahiro, Nishikiori, Tatsuhiro, Onda, Yuichi, Shinano, Takuro, and Tsuji, Hideki

Published
2019
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46. Middle‒late Asselian conodonts discovered from the limestone body in the Chichibu Belt, Mikkabi, Hamamatsu, central Japan

Author

SUZUKI, Kazuhiro, HAYASHI, Seiji, and MIMURA, Kouichi

Abstract

We investigated the limestone body in Mikkabi, Hamamatsu, central Japan, one of the limestone bodies in the Chichibu Belt. It is widely known that the limestone body here contains very few fossils. Detailed information on the deposition age of the body is still limited, although the deposition age was determined as the Early Permian by fusulinid biostratigraphy. In this study, we intended to find conodonts from the limestone body and to confirm the deposition age by conodonts. From five block samples of the limestone body, we extracted intact and fragmented conodonts and at least three species were determined by comparison with previous studie--Mesogondolella dentiseparata (middle–late Asselian), Mesogondolella sp., Neogondolella sp. (late Carboniferous–late Triassic), and Streptognathodus sp. (late Carboniferous–Artinskian). Our results suggest that the limestone body in the Mikkabi area was at least partly deposited in the middle–late Asselian.

Published
2023

47. Exploring simple ways to avoid collecting highly 137Cs-contaminated Aralia elata buds for the revival of local wild vegetable cultures.

Author

Sakai, Masaru, Watanabe, Mirai, Kanao Koshikawa, Masami, Tanaka, Asuka, Takahashi, Akiko, Takechi, Seiichi, Takagi, Mai, Tsuji, Takashi, Tsuji, Hideki, Takeda, Toshimasa, Jo, Jaeick, Tamaoki, Masanori, and Hayashi, Seiji

Subjects
CESIUM, NUCLEAR power plant accidents, BUDS, SOIL depth
Abstract

Collection and cooking of wild vegetables have provided seasonal enjoyments for Japanese local people as provisioning and cultural ecosystem services. However, the Fukushima Daiichi Nuclear Power Plant accident in March 2011 caused extensive radiocesium contamination of wild vegetables. Restrictions on commercial shipments of wild vegetables have been in place for the last 10 years. Some species, including buds of Aralia elata, are currently showing radiocesium concentrations both above and below the Japanese reference level for food (100 Bq/kg), implying that there are factors decreasing and increasing the 137Cs concentration. Here, we evaluated easy-to-measure environmental variables (dose rate at the soil surface, organic soil layer thickness, slope steepness, and presence/absence of decontamination practices) and the 137Cs concentrations of 40 A. elata buds at 38 locations in Fukushima Prefecture to provide helpful information on avoiding collecting highly contaminated buds. The 137Cs concentrations in A. elata buds ranged from 1 to 6,280 Bq/kg fresh weight and increased significantly with increases in the dose rate at the soil surface (0.10–6.50 μSv/h). Meanwhile, the 137Cs concentration in A. elata buds were not reduced by decontamination practices. These findings suggest that measuring the latest dose rate at the soil surface at the base of A. elata plants is a helpful way to avoid collecting buds with higher 137Cs concentrations and aid in the management of species in polluted regions. [ABSTRACT FROM AUTHOR]

Published
2024
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