EBIHARA, Mitsuru



Faculty of Education and Integrated Arts and Sciences, School of Education

Job title

Professor(without tenure)

Homepage URL


Concurrent Post 【 display / non-display

  • Faculty of Science and Engineering   Graduate School of Creative Science and Engineering

Education 【 display / non-display

  • 1976.04

    The University of Tokyo   Graduate School of Science  

  • 1974.04

    The University of Tokyo   Graduate School of Science  

  • 1972.04

    The University of Tokyo   Faculty of Science   Department of Chemistry  

  • 1970.04

    The University of Tokyo   College of Arts and Sciences  

Degree 【 display / non-display

  • 東京大学   理学博士

Research Experience 【 display / non-display

  • 2018.03

    Waseda University   Faculty of Education and Integrated Arts and Sciences

  • 2017.04

    Tokyo Metropolitan University

  • 2006.04

    Tokyo Metropolitan University

  • 2005.04

    Tokyo Metropolitan University   Faculty of Urban Liberal Arts

  • 2001.01

    Tokyo Metropolitan University

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Research Areas 【 display / non-display

  • Space and planetary sciences

  • Solid earth sciences

Research Interests 【 display / non-display

  • 希土類元素

  • 白金族元素

  • 揮発性元素

  • 隕石母天体

  • 親鉄元素

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Papers 【 display / non-display

  • Time-series analysis of atmospheric radiocesium at two SPM monitoring sites near the Fukushima Daiichi Nuclear Power Plant just after the Fukushima accident on March 11, 2011

    Haruo Tsuruta, Yasuji Oura, Mitsuru Ebihara, Yuichi Moriguchi, Toshimasa Ohara, Teruyuki Nakajima

    Geochemical Journal   52 ( 2 ) 103 - 121  2018  [Refereed]

     View Summary

    Using an hourly-resolution time series of the Fukushima radionuclides collected on used filter-tapes installed in suspended particulate matter (SPM) monitors, we measured the hourly radiocesium values at the SPM monitoring sites of Futaba and Naraha located within 20 km of the Fukushima Daiichi Nuclear Power Plant (FD1NPP) during March 12–25, 2011. The time-series of the 137Cs concentrations at the sites were analyzed and compared with radiation dose rates at the many monitoring posts/points of Fukushima Prefecture and the Tokyo Electric Power Company. At Futaba, nine plumes of high 137Cs concentrations were found on March 12–13, 15–16, 18–20, and 24–25, 2011, when southeasterly winds prevailed. On March 12, the first peak of the 137Cs concentrations was detected at Futaba at 9:00 Japanese Standard Time (JST) due to the first release from reactor Unit 1 (U1) in the early morning. Furthermore, the highest 137Cs concentration, i.e., 13,600 Bq m–3 was observed at 15:00 JST after a vent operation at U1, just before the hydrogen explosion of U1 at 15:36 JST. On the afternoon of March 15, plumes from the FD1NPP were observed at Futaba due to a constant southeasterly wind and were then transported to downwind, resulting in the formation of a highly deposited zone of radionuclides spanning more than 30 km from near the FD1NPP to the northwest. In contrast, seven plumes of high 137Cs concentrations were found at Naraha on March 15–16, 18, 20–21, 2011, when northerly winds prevailed. On March 15, a plume caused by the first release from Unit 2 was observed at Naraha at 1:00 JST, and the highest concentration, i.e., 8,300 Bq m–3, was observed at 3:00 JST, and then were transported southward to the Kantou area. The activity ratios of 134Cs/137Cs in the plumes were divided into two groups. The plumes at Futaba on March 12–13, which had ratios of 0.92–0.94, are identified to be released from U1, compared to its ratio of 0.94, as derived from the inventory data. All other plumes with the ratios of 1.02–1.04 at Futaba and Naraha during March 15–21 have not been determined to be released from U2 and/or Unit 3.


  • Mossbauer spectroscopic study on the composition of Fe-containing minerals in ordinary chondrites, Miller Range 07710 and Yamato 790272

    W. Sato, M. Nakagawa, N. Shirai, M. Ebihara

    Hyperfine Interact   239  2018  [Refereed]

  • Formation of an ultracarbonaceous Antarctic micrometeorite through minimal aqueous alteration in a small porous icy body

    Hikaru Yabuta, Takaaki Noguchi, Shoichi Itoh, Tomoki Nakamura, Akira Miyake, Shinichi Tsujimoto, Noriaki Ohashi, Naoya Sakamoto, Minako Hashiguchi, Ken-ichi Abe, Aya Okubo, A. L. David Kilcoyne, Shogo Tachibana, Ryuji Okazaki, Kentaro Terada, Mitsuru Ebihara, Hiroko Nagahara

    GEOCHIMICA ET COSMOCHIMICA ACTA   214   172 - 190  2017.10  [Refereed]

     View Summary

    A comprehensive study of the organic chemistry and mineralogy of an ultracarbonaceous micrometeorite (UCAMM D05IB80) collected from near the Dome Fuji Station, Antarctica, was carried out to understand the genetic relationship among organic materials, silicates, and water. The micrometeorite is composed of a dense aggregate of similar to 5 mm-sized hollow ellipsoidal organic material containing submicrometer-sized phases such as glass with embedded metal and sulfides (GEMS) and mineral grains. There is a wide area of organic material (similar to 15 x 15 mu m) in its interior. Low-Ca pyroxene is much more abundant than olivine and shows various Mg/(Mg + Fe) ratios ranging from similar to 1.0 to 0.78, which is common to previous works on UCAMMs. By contrast, GEMS grains in this UCAMM have unusual chemical compositions. They are depleted in both Mg and S, which suggests that these elements were leached out from the GEMS grains during very weak aqueous alteration, without the formation of phyllosilicates.
    The organic materials have two textures-smooth and globular with an irregular outline- and these are composed of imine, nitrile and/or aromatic nitrogen heterocycles, and amide. The ratio of nitrogen to carbon (N/C) in the smooth region of the organics is similar to 0.15, which is five times higher than that of insoluble organic macromolecules in types 1 and 2 carbonaceous chondritic meteorites. In addition, the UCAMM organic materials are soluble in epoxy and are thus hydrophilic; this polar nature indicates that they are very primitive. The surface of the material is coated with an inorganic layer, a few nanometers thick, that consists of C, O, Si, S, and Fe. Sulfur is also contained in the interior, implying the presence of organosulfur moieties. There are no isotopic anomalies of D, C-13, or N-15 in the organic material.
    Interstellar photochemistry alone would not be sufficient to explain the N/C ratio of the UCAMM organics; therefore, we suggest that a very small amount of fluid on a comet must have been necessary for the formation of the UCAMM. The GEMS grains depleted in Mg and S in the UCAMM prove a very weak degree of aqueous alteration; weaker than that of carbonaceous chondrites. Short-duration weak alteration probably caused by planetesimal shock locally melted cometary ice grains and released water that dissolved the organics; the fluid would likely have not mobilized because of the very low thermal conductivity of the porous icy body. This event allowed the formation of the large organic puddle of the UCAMM, as well as organic matter sulfurization, formation of thin membrane-like layers of minerals, and deformation of organic nanoglobules. (C) 2017 Elsevier Ltd. All rights reserved.


  • Accurate Determination of Chlorine, Bromine and Iodine in US Geological Survey Geochemical Reference Materials by Radiochemical Neutron Activation Analysis

    Shun Sekimoto, Mitsuru Ebihara

    GEOSTANDARDS AND GEOANALYTICAL RESEARCH   41 ( 2 ) 213 - 219  2017.06  [Refereed]

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    Trace amounts of three halogens (chlorine, bromine and iodine) in seventeen U.S. Geological Survey (USGS) geochemical reference materials were determined by radiochemical neutron activation analysis (RNAA). The materials analysed were AGV-2 (and esite), BCR-2, BHVO-2 and BIR-1a (basalts), CLB-1 (coal), COQ-1 (carbonatite), DGPM-1 (disseminated gold ore), DNC-1a (dolerite), DTS-2b (dunite), GSP-2 (granodiorite), Nod-A-1 and Nod-P-1 (manganese nodules), QLO-1a (quartz latite), SBC-1 (marine shale), SDC-1 (mica schist), SGR-1b (shale rock) and W-2a (diabase). The chlorine, bromine and iodine contents were determined to be 5.64mg kg(-1) (BIR-1a) to 4410mg kg(-1) (Nod-A-1), 0.039mg kg(-1) (BIR-1a) to 52.1mg kg(-1) (CLB-1), and 0.041mgkg(-1) (BIR-1a) to 599mg kg(-1) (CLB-1), respectively. The RNAA data of the three halogens were compared with the corresponding data in the literature.


  • Petrogenesis of the EET 92023 achondrite and implications for early impact events

    A. Yamaguchi, N. Shirai, C. Okamoto, M. Ebihara

    METEORITICS & PLANETARY SCIENCE   52 ( 4 ) 709 - 721  2017.04  [Refereed]

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    We report petrology and geochemistry of an achondrite EET 92023 and compare it with normal and anomalous eucrites. EET 92023 is an unbrecciated achondrite and shows a granular texture mainly composed of low-Ca pyroxene and plagioclase, petrologically similar to normal cumulate eucrites such as Moore County. However, this rock contains a significant amount of kamacite and taenite not common in unbrecciated, crystalline eucrites. EET 92023 contains a significant amount of platinum group elements (PGEs) (ca. 10% of CI), several orders of magnitude higher than those of monomict eucrites. We suggest that the metallic phases carrying PGEs were incorporated by a projectile during or before igneous crystallization and thermal metamorphism. The projectile was likely to be an iron meteorite rather than chondritic materials, as indicated by the lack of olivine and the presence of free silica. Therefore, the oxygen isotopic signature is indigenous, rather than due to contamination of the projectile material with different oxygen isotopic compositions. A significant thermal event involving partial melting and metamorphism after the impact event indicates that EET 92023 records early impact events which took place shortly after the crust formation on a differentiated protoplanet when the crust was still hot.


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Misc 【 display / non-display

  • はやぶさ宇宙探査機によって小惑星イトカワから回収された粒子の中性子放射化分析


    放射化学ニュース   25   1 - 8  2012  [Invited]

    Article, review, commentary, editorial, etc. (scientific journal)  

  • Report of NAMLS10

    Mitsuru Ebihara

    Isotope News   ( 697 ) 34 - 35  2012  [Invited]

    Article, review, commentary, editorial, etc. (scientific journal)  

  • 福島第一原子力発電所事故に対する地球化学会の取り組み


    地球化学   46   79 - 86  2012  [Refereed]  [Invited]

    Article, review, commentary, editorial, etc. (scientific journal)  


  • 中性子放射化分析法 – 宇宙物質に最適な元素分析法


    ぶんせき   2012年 ( 10月号 ) 562 - 565  2012  [Invited]

    Article, review, commentary, editorial, etc. (other)  

  • リマインダー:原子量は変わる?(日本化学会だより)

    海老原 充

    化学と教育   59 ( 4 )  2011.04


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Specific Research 【 display / non-display

  • 隕石中の高輝発性元素存在に基づく太陽系初期の物質進化に関する研究


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    内惑星領域の固体物質の生成の初期過程として元素の凝縮過程が考えられる。本研究ではこの凝縮過程で低い温度で気体から固体に移行する元素群である高揮発性元素に焦点を当て、始原的エコンドライトを対象に実験を行った。研究に用いた隕石はMAC 02675 (CBb)、 Asuka 881020, Asuka 881541, PAT 91546、PCA 91467 (以上CH)(カッコ内はグループ名)の5つの南極隕石である。中性子放射化分析、誘導結合(ICP)プラズマ質量分析、ICP原子発光分析の元素分析法を用い、それぞれの隕石の持つ元素組成上の特徴を明らかにした。その結果、各隕石とも、母天体形成後にその表層で起こった衝突によって気化した物質から凝縮により生成したものと解釈された。

  • 太陽系初期におけるハロゲン元素の挙動の解明


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  • 希土類元素の太陽系元素存在度


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    太陽系の元素存在度は太陽系を構成する物質の元素の相対存在度であり、太陽系に関する最も基本的な数値である。地球に飛来する隕石のうち、CIコンドライト隕石はほとんどの元素で太陽系の元素組成をもつ。本研究では、誘導結合プラズマ質量分析 (ICP-MS) 法を用いて、CIコンドライト隕石中の希土類元素 (REE) を精度、確度ともに高い分析値を求め、その結果をもとに現時点でもっとも妥当な希土類元素に関する太陽系存在度を推定することを目的とした。本報告書作成時点で、早稲田大学の新しい研究室に移設したICP-MS装置によるREE定量法を確立し、研究目的を達成すべく、実験を継続している。


Syllabus 【 display / non-display

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