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Journal Articles

Mechanism of long-term radiocaesium accumulation in lichens

Dohi, Terumi

Raiken, 21(3), p.29 - 36, 2021/09

no abstracts in English

Journal Articles

Radiocaesium accumulation capacity of epiphytic lichens and adjacent barks collected at the perimeter boundary site of the Fukushima Dai-ichi Nuclear Power Station

Dohi, Terumi; Omura, Yoshihito*; Yoshimura, Kazuya; Sasaki, Takayuki*; Fujiwara, Kenso; Kanaizuka, Seiichi*; Nakama, Shigeo; Iijima, Kazuki

PLOS ONE (Internet), 16(5), p.e0251828_1 - e0251828_16, 2021/05

 Times Cited Count:1 Percentile:0(Multidisciplinary Sciences)

Journal Articles

Quantum chemical calculation studies toward microscopic understanding of retention mechanism of Cs radioisotopes and other alkali metals in lichens

Suno, Hiroya; Machida, Masahiko; Dohi, Terumi; Omura, Yoshihito*

Scientific Reports (Internet), 11(1), p.8228_1 - 8228_13, 2021/04

 Times Cited Count:1 Percentile:63.19(Multidisciplinary Sciences)

We evaluate stability of caesium (Cs) and other alkali-metal cation complexes of lichen metabolites in both gas and aqueous phases to discuss why lichens can retain radioactive Cs in the thalli over several years. We focus on oxalic acid, (+)-usnic acid, atranorin, lecanoric acid, and protocetraric acid, which are common metabolite substances in various lichens including, e.g., $textit{Flavoparmelia caperata}$ and $textit{Parmotrema tinctorum}$ retaining Cs in Fukushima, Japan. By performing quantum chemical calculations, their gas-phase complexation energies and aqueous-solution complexation free energies with alkali-metal cations are computed for their neutral and deprotonated cases. Consequently, all the molecules are found to energetically favor cation complexations and the preference order is Li$$^+>$$Na$$^+>$$K$$^+>$$Rb$$^+>$$Cs$$^+$$ for all conditions, indicating no specific Cs selectivity but strong binding with all alkali cations. Comparing complexation stabilities among these metabolites, lecanoric and protocetraric acids seen in medullary layer are found to keep higher affinity in their neutral case, while (+)-usnic acid and atranorin in upper cortex exhibit rather strong affinity only in deprotonated cases through forming stable six atoms' ring containing alkali cation chelated by two oxygens. These results suggest that the medullary layer can catch all alkali cations in a wide pH range around the physiological one, while the upper cortex can effectively block penetration of metal ions when the metal stress grows. Such insights highlight a physiological role of metabolites like blocking of metal-cation migrations into intracellular tissues, and explain long-term retention of alkali cations including Cs in lichens containing enough such metabolites to bind them.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Journal Articles

Vertical distribution of $$^{90}$$Sr and $$^{137}$$Cs in soils near the Fukushima Daiichi Nuclear Power Station

Sasaki, Takayuki*; Matoba, Daisuke*; Dohi, Terumi; Fujiwara, Kenso; Kobayashi, Taishi*; Iijima, Kazuki

Journal of Radioanalytical and Nuclear Chemistry, 326(1), p.303 - 314, 2020/10

 Times Cited Count:1 Percentile:39.17(Chemistry, Analytical)

Journal Articles

Radiation dose distribution in a mountainous area nearby the Fukushima Dai-ichi Nuclear Power Plant and data analysis

Dohi, Terumi; Muto, Kotomi; Yoshimura, Kazuya; Kanaizuka, Seiichi*; Iijima, Kazuki

KEK Proceedings 2019-2, p.14 - 19, 2019/11

In order to investigate the effect of topography, meteorological condition, etc., on the spatial distribution of air dose rate on the main plume path, we evaluated walking survey data of air dose rates on Mt. Koutaishi and Mt. Juman, directed in northwest of and approximately 33 km and 11 km from the FDNPP. Measurements were performed on two orbital routs with different constant altitudes and general mountain trails in each mountain. The measurement data were compared with airborne monitoring results to investigate the relation between the dose rate distribution and elevation and orientation. At Mt. Koutaishi, the air dose rate was particularly high on the east side of the mountain, and the significant dependence of direction on the dose rate distribution was observed. Furthermore, high dose rate near the mountain foot indicates possibility of large deposition of $$^{137}$$Cs due to the plume passage from the FDNPP. At Mt. Juman, uniformly distribution of air dose rate was observed, and effect of wet deposition was considered. These results suggest the possibility of different deposition mechanisms in mountain range unit.

Journal Articles

Book review "Handbook of humic substances"

Dohi, Terumi

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 61(11), P. 31, 2019/11

no abstracts in English

Journal Articles

Electron microscopic analysis of radiocaesium-bearing microparticles in lichens collected within 3 km of the Fukushima Dai-ichi Nuclear Power Plant

Dohi, Terumi; Tagomori, Hisaya; Omura, Yoshihito*; Fujiwara, Kenso; Kanaizuka, Seiichi*; Iijima, Kazuki

Environmental Radiochemical Analysis VI, p.58 - 70, 2019/09

In this study we established a separation method for radiocaesium-bearing microparticles (CsMPs) from lichens using electron microscopic analysis. Lichens were first digested within hydrogen peroxide and then an automatic particle analyser system based on FE-EPMA was used for detecting CsMPs within lots of mineral-like and metallic particles quickly. The elemental composition and radiocaesium activities of the separated CsMPs were measured, and the results show that the digestion treatment did not influence the CsMPs characteristics. An inhomogeneous elemental distribution was found in some CsMPs by two-dimensional elemental analysis using FE-EMPA. Our methods for separation of CsMPs and analysing their elemental composition are expected to be useful for grasping the chemical composition trends of CsMPs statistically.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Journal Articles

Inner structure and inclusions in radiocesium-bearing microparticles emitted in the Fukushima Daiichi Nuclear Power Plant accident

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Microscopy, 68(3), p.234 - 242, 2019/06

 Times Cited Count:5 Percentile:70.99(Microscopy)

Radiocesium-bearing microparticles (CsMPs), consisting substantially of silicate glass, were released to the environment during the Fukushima nuclear accident in March 2011. We investigated a total of nine CsMPs using transmission electron microscopy (TEM) and inferred the atmosphere in the reactors during the accident. From elemental mapping using energy-dispersive X-ray spectrometry, Fe and Zn showing radial inhomogeneities were found in the CsMPs, in addition to the Cs that had been previously reported. Four of the CsMPs included submicron crystals, which were identified as chromite, franklinite, acanthite, molybdenite, and hessite. The chromium-containing spinels, chromite and franklinite, indicated the presence of ferrous iron (Fe$$^{2+}$$), suggesting that the inside of the reactors was reductive to some extent. Electron energy-loss spectroscopy also confirmed that the CsMPs did not contain boron, and therefore the atmosphere in which they were formed might be boron-free.

JAEA Reports

Separation of radiocaesium-bearing micro particle from environmental samples; Application to litter samples

Tagomori, Hisaya; Dohi, Terumi; Ishii, Yasuo; Kanaizuka, Seiichi*; Fujiwara, Kenso; Iijima, Kazuki

JAEA-Technology 2019-001, 37 Pages, 2019/03

JAEA-Technology-2019-001.pdf:26.85MB

An efficient methodology for separating the radiocaesium-bearing micro particles (CsMPs) released by the TEPCO's Fukushima Dai-ichi Nuclear Power Station accident is required to investigate their spatial distribution and physicochemical properties. In this report we developed an efficiency separation method for CsMP from litters since the radiocaesium in litter may affect the radiocaesium cycling in forest ecosystem. One CsMP separation from litter containing lots of soil particles was attained within three days using electron microscopic analysis with digestion treatment of organic matter. This methodology is expected as CsMPs efficient separation method for not only forest floor litter but also barks and leaves of living tree, and other organic materials in the forested environment.

Journal Articles

Dissolution behaviour of radiocaesium-bearing microparticles released from the Fukushima nuclear plant

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Scientific Reports (Internet), 9(1), p.3520_1 - 3520_9, 2019/03

 Times Cited Count:22 Percentile:90.33(Multidisciplinary Sciences)

Radiocesium-bearing microparticles (CsMPs) were released by the FDNPP accident. We conducted dissolution experiments of CsMPs by reaction with pure water absorbing CO $$_{2}$$ from the atmosphere and seawater. The activation energy for the dissolution of CsMPs was estimated to be 67 and 89 kJ/mol, and the dissolution rate at 13$$^{circ}$$C was 0.011 and 0.130 $$mu$$m/y for pure water and seawater, respectively. Probably the faster dissolution rate in seawater than in pure water is mainly owing to the difference in pH. The shapes of CsMPs dissolved in pure water were considerably altered. Tin oxide and iron oxide nanoparticulates were formed on their surfaces. Such features were similar to those observed in a CsMP collected recently in Fukushima Prefecture, indicating that dissolution of CsMPs is also occurring in the environment. In the case of CsMPs dissolved in seawater, a crust of secondary minerals rich in Mg and Fe was formed and the glass matrix became smaller inside the crust.

Journal Articles

Loss of radioactivity in radiocesium-bearing microparticles emitted from the Fukushima Dai-ichi Nuclear Power Plant by heating

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Scientific Reports (Internet), 8, p.9707_1 - 9707_8, 2018/06

 Times Cited Count:8 Percentile:47.43(Multidisciplinary Sciences)

Radiocesium-bearing microparticles (CsP) substantially made of silicate glass are a novel form of radiocesium (RCs) emitted from the Fukushima Dai-ichi NPP. CsPs have a potential risk of internal radiation exposure caused by inhalation. Radiation-contaminated waste (Rcw) including CsPs is being burned in incinerators; therefore, this study has investigated the responses of CsPs to heating in air. The radioactivity of CsPs gradually decreased from 600 $$^{circ}$$C and was almost lost when the temperature reached 1000 $$^{circ}$$C. The size and spherical morphology of CsPs were almost unchanged after heating, but Cs including RCs, K and Cl were lost, probably diffused away from the CsPs. When the CsPs were heated together with weathered granitic soil that is common in Fukushima, the RCs released from CsPs was sorbed by the surrounding soil. From these results, it is expected that the radioactivity of CsPs will be lost when Rcw including CsPs is burned in incinerators.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima; As a part of dissemination of evidence-based information

Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.

JAEA-Review 2017-018, 86 Pages, 2017/10

JAEA-Review-2017-018.pdf:17.58MB

Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.

Journal Articles

Fate of radiocesium in freshwater aquatic plants and algae in the vicinity of the Fukushima Daiichi Nuclear Power Plant

Sasaki, Yoshito; Funaki, Hironori; Iri, Shatei; Dohi, Terumi; Hagiwara, Hiroki

Limnology, 17(2), p.111 - 116, 2016/04

AA2015-0204.pdf:3.47MB

 Times Cited Count:7 Percentile:39(Limnology)

The behavior of radiocesium ($$^{137}$$Cs) in aquatic plants (five species) and algae (three genera) that had been grown in a river (one sampling point) and ponds (four sampling points) in the area around the Fukushima Daiichi Nuclear Power Plant was investigated. The sediment-to-plant transfer factor (TF) was measured. For aquatic plants, the highest value was 5.55 for ${it P. crispus}$ from the river; the lowest was 3.34 $$times$$ 10$$^{-2}$$ for ${it P. distinctus}$ from a pond. There were significant differences in the values for aquatic plants belonging to the same genus. The water-to-plant TF of filamentous algae (${it Spirogyra}$ sp.) and cyanobacteria (coexisting ${it Anabaena}$ sp. and ${it Microcystis}$ sp.) were 2.39 $$times$$ 10$$^{3}$$ and 1.26 $$times$$ 10$$^{3}$$, respectively. The $$^{137}$$Cs concentration of cyanobacteria fraction in pond water was 4.87 $$times$$ 10$$^{-1}$$ Bq/L, the same order of magnitude as the $$^{137}$$Cs concentration of pond water. Enrichment of radiocesium in cyanobacteria was not observed.

Journal Articles

Radiocaesium activity concentrations in parmelioid lichens within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Journal of Environmental Radioactivity, 146, p.125 - 133, 2015/08

 Times Cited Count:13 Percentile:48.04(Environmental Sciences)

Radiocaesium activity concentrations ($$^{134}$$Cs, $$^{137}$$Cs) were measured in parmelioid lichens collected within the Fukushima Prefecture approximately 2 y after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. A total of 44 samples consisting of nine species were collected at 16 points within a 60 km radius of the FDNPP. The activity concentration of $$^{134}$$Cs ranged from 4.6 to 1000 kBq kg$$^{-1}$$ and for $$^{137}$$Cs ranged from 7.6 to 1740 kBq kg$$^{-1}$$. A significant positive correlation was found between the $$^{137}$$Cs activity concentration in lichens and the $$^{137}$$Cs deposition density on soil, based on the calculated Spearman's rank correlation coefficients as $$r$$ = 0.90 ($$P$$ $$<$$ 0.01). The two dominant species, Flavoparmelia caperata and Parmotrema clavuliferum, showed strong positive correlations, for which the r values were calculated as 0.92 ($$P$$ $$<$$ 0.01) and 0.90 ($$P$$ $$<$$ 0.01) respectively. Therefore, they are suggested as biomonitoring species for levels of radiocaesium fallout within the Fukushima Prefecture.

Journal Articles

$$^{137}$$Cs concentrations in foliose lichens within Tsukuba-city as a reflection of radioactive fallout from the Fukushima Dai-ichi Nuclear Power Plant accident

Omura, Yoshihito*; Matsukura, Kimiyo*; Abe, Junichi*; Hosaka, Kentaro*; Tamaoki, Masanori*; Dohi, Terumi; Kakishima, Makoto*; Seaward, M. R. D.*

Journal of Environmental Radioactivity, 141, p.38 - 43, 2015/03

 Times Cited Count:8 Percentile:31.98(Environmental Sciences)

$$^{137}$$Cs concentrations in ten species of foliose lichens collected within Tsukuba-city in August 2013 ranged from 1.7 to 35 kBq/kg. The relationships between $$^{137}$$Cs in two dominant species, Dirinaria applanata and Physcia orientalis, and the air dose rate ($$mu$$Sv/h) at the sampling sites were investigated. $$^{137}$$Cs in P. orientalis measured about 1 year after the Fukushima nuclear accident was correlated (r$$^{2}$$=0.80) more closely with the air dose rate than those measured after about 2 years (r$$^{2}$$=0.65), possibly demonstrating its continued value as a biomonitor to reflect ambient fall-out levels. In contrast, those of Dirinaria applanata were not correlated with the air dose rate in either year.

Journal Articles

Outline of Investigation for radiocaesium concentrations in lichens after Fukushima Dai-ichi Nuclear Power Plant accident

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Raiken, 18(1), p.11 - 13, 2014/12

no abstracts in English

Journal Articles

Disposal of low-level radioactive waste generated from research, industrial, and medical facilities in Japan

Dohi, Terumi

Genshiryoku Nenkan 2014, p.138 - 139, 2013/10

no abstracts in English

66 (Records 1-20 displayed on this page)