教員紹介 – 乙坂 重嘉

乙坂 重嘉 otosaka(a)aori.u-tokyo.ac.jp

准教授・博士(地球環境科学)

東京大学大気海洋研究所

海洋化学部門・海洋無機化学分野

〒277-8564 千葉県柏市柏の葉5-1-5

 

海洋には、様々な物質が運ばれています。それらの分布を正しく把握するとともに、その成因を矛盾なく説明できるようにすることは、例えば、人類活動によって放出された物質の海洋環境への影響を知るうえで不可欠です。

私は、海水中や海底に存在する微量元素や放射性核種の供給源と行方を追跡するため、海洋観測と化学分析を主な手法とした研究に取り組んでいます。

特に、海水中を浮遊したり沈降したりしながら移動する粒子状物質が、どのようにして海洋における微量元素や放射性核種のキャリア(運び屋)としての役割を果たしているかについて、理解を深めることを主な目的としています。

これまでの主な研究テーマ

  • 日本周辺海域を沈降移動する陸起源粒子の供給源と輸送経路の推定
  • 日本海における人工放射性核種の分布と移行過程の解明
  • 東京電力福島第一原子力発電所事故由来の放射性核種の分布・移行過程の解明
  • 加速器質量分析装置 (AMS)を用いた海水中の溶存有機態放射性炭素 (DOC-14C) 分析法の開発と高度化

 

略歴

1996年3月 北海道大学水産学部水産化学科卒業

1998年3月 北海道大学大学院地球環境科学研究科修士課程修了

2000年3月 北海道大学大学院地球環境科学研究科博士後期課程退学

2004年12月 博士(地球環境科学), 北海道大学

2000年4月 日本原子力研究所 環境科学研究部 研究員

2005年10月 日本原子力研究開発機構 原子力基礎工学研究部門 研究員

2010年2月~2011年2月 米国 テキサスA&M大学ガルベストン校 外来研究員

2011年10月 日本原子力研究開発機構 原子力基礎工学研究部門 研究副主幹

2015年7月 日本原子力研究開発機構 原子力基礎工学研究センター 研究主幹

2018年12月 東京大学大気海洋研究所 准教授

 

所属学会

日本海洋学会

日本地球化学会

日本原子力学会

American Geophysical Union

 

Publication list

Researchmap (https://researchmap.jp/shigeyoshiotosaka/) でもご覧いただけます。

 

Suzuki, T., S. Otosaka, J. Kuwabara, H. Kawamura, T. Kobayashi:  Vertical distribution of 129I released from the Fukushima Daiichi Nuclear Power Plant in the Kuroshio and Oyashio current areas.  Marine Chemistry 204, 163-171 (2018).

Otosaka, S., Y. Satoh, T. Suzuki, J. Kuwabara, T. Nakanishi: Distribution and fate of 129I in the seabed sediment off Fukushima.  Journal of Environmental Radioactivity 192, 208-218 (2018).

Fukuda, M., T. Aono, S. Yamazaki, T. Ishimaru, J. Kanda, J. Nishikawa, S. Otosaka:  Factors controlling 134Cs activity concentrations in sediment collected off the coast of Fukushima Prefecture in 2013-2015. Geochemical Journal 52, 201-209 (2018).

Khim, B.-K., S. Otosaka, K.-A. Park, S. Noriki:  δ13C and δ15N values of sediment-trap particles in the Japan and Yamato Basins and comparison with the core-top values in the East/Japan Sea.  Ocean Science Journal 53, 17-29 (2018).

Otosaka, S.:  Processes affecting long-term changes in 137Cs concentration in surface sediments off Fukushima. Journal of Oceanography 73, 559-570 (2017).

Fukuda, M., T. Aono, S. Yamazaki, J. Nishikawa, S. Otosaka, T. Ishimaru, J. Kanda:  Dissolved radiocaesium in seawater off the coast of Fukushima during 2013–2015. Journal of Radioanalytical and Nuclear Chemistry 311, 1479-1484 (2017).

Matsunaga, T., T. Nakanishi, M. Atarashi-Andoh, E. Takeuchi, K. Muto, K. Tsuduki, S. Nishimura, J. Koarashi, S. Otosaka, T. Sato, Y. Miyata, S. Nagao:  Year-round variations in the fluvial transport load of particulate 137Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident.  Journal of Radioanalytical and Nuclear Chemistry 310, 679-693 (2016).

Buesseler, K.O., C.R. German, M.C. Honda, S. Otosaka, E.E. Black, H. Kawakami, S.J. Manganini, S.M. Pike:  Tracking the fate of particle associated Fukushima Daiichi cesium in the ocean off Japan. Environmental Science and Technology 49, 9807-9816 (2015).

Matsunaga, T., T. Nakanishi, E. Takeuchi, S. Nishimura, K. Tsuduki, M. Atarashi-Andoh, J. Koarashi, S. Otosaka, T. Sato, S. Nagao: A passive collection method for whole size fractions of suspended river materials. Journal of Radioanalytical Nuclear Chemistry 303, 1291-1295 (2015).

Bu, W., J. Zheng, Q. Guo, T. Aono, S. Otosaka, K. Tagami, S. Uchida: Temporal distribution of plutonium isotopes in marine sediments off Fukushima after the Fukushima Dai-ichi Nuclear Power Plant accident. Journal of Radioanalytical Nuclear Chemistry, 303, 1151-1154 (2015).

Otosaka, S., T. Nakanishi, T. Suzuki, Y. Satoh, H. Narita: Vertical and lateral transport of particulate radiocesium off Fukushima. Environmental Science and Technology 48, 12595-12602 (2014).

Schwehr, K.A, S. Otosaka, S. Merchel, D.I. Kaplan, S. Zhang, C. Xu, H.-P. Li, Y.-F. Ho, C.M. Yeager, ASTER Team, P.H. Santschi: Speciation of iodine isotopes inside and outside of a contaminant plume at the Savannah River Site. Science of the Total Environment 497-498, 671-678 (2014).

Otosaka, S., Y. Kato: Radiocesium derived from the Fukushima Daiichi Nuclear Power Plant accident in seabed sediments: Initial deposition and inventories. Environmental Science: Processes & Impacts 16, 978-990 (2014).

Satoh, Y., S. Otosaka, T. Suzuki: Determination of total iodine concentration in aquatic environments using cathodic stripping voltammetry combined with sodium hypochlorite (NaClO) oxidation. Journal of Water and Environmental Technology 12, 201-210 (2014).

Suzuki, T., S. Otosaka, J. Kuwabara, H Kawamura, T. Kobayashi: Iodine-129 concentration in seawater near Fukushima before and after the accident at the Fukushima Daiichi Nuclear Power Plant. Biogeosciences 10, 3839-3747 (2013).

Otosaka, S., T. Kobayashi: Sedimentation and remobilization of radiocesium in the coast of Ibaraki, 70 km south of the Fukushima Dai-ichi Nuclear Power Plant. Environmental Monitoring and Assessment 185, 5419-5433 (2013).

Suzuki, T., S. Otosaka, O. Togawa: Concentration of iodine-129 in surface seawater at subarctic and subtropical circulations in the Japan Sea. Nuclear Instrument and Methods in Physics Research B 294, 563-567 (2013).

Johnson, B.E., P. H. Santschi, C.-Y. Chuang, S. Otosaka, R. Shane Addleman, M. Douglas, R.D. Rutledge, W. Chouyyok, J.D. Davidson , G.E. Fryxell, J. M. Schwantes: Collection of Lanthanides and Actinides from Natural Waters with Conventional and Nanoporous Sorbents. Environmental Science and Technology, 46, 11251-11258 (2012).

Ishihara, R., S. Asai, S. Otosaka, S. Yamada, H. Hirota, K. Miyoshi, D. Umeno, K. Saito: Dependence of lanthanide-ion binding performance on HDEHP concentration in HDEHP impregnation to porous sheet. Solvent Extraction and Ion Exchange 30, 171-180 (2012)

Li, H.-P., C.M. Yeager, R. Brinkmeyer, S. Zhang, Y.-F. Ho, C. Xu, W.L. Jones, K.A. Schwehr, S. Otosaka, K.A. Roberts, D.I. Kaplan, P.H. Santschi: Bacterial production of organic acids enhances H2O2-dpendent iodine oxidation. Environmental Science and Technology 46, 4837-4844 (2012).

Xu, C., E.J. Miller, S. Zhang, H.-P. Li, Y.-F. Ho, K.A. Schwehr, D.I. Kaplan, K.A. Roberts, S. Otosaka, R. Brinkmeyer, C.M. Yeager, P.H. Santschi: Sequestration and re-mobilization of radioiodine (129I) by soil organic matter and possible consequences of the remedial action at Savannah River Site. Environmental Science and Technology 45, 9975-9983 (2011).

Otosaka, S., K.A. Schwehr, D.I. Kaplan, K.A. Roberts, S. Zhang, C. Xu, H.-P. Li, Y.-F. Ho, R. Brinkmeyer, C.M. Yeager, P.H. Santschi: Factors controlling mobility of 127I and 129I species in an acidic groundwater plume at the Savannah River Site.  Science of the Total Environment 409, 3857-3865 (2011).

Xu, C., S. Zhang, Y.-F. Ho, E.J. Miller, K.A. Roberts, H.-P. Li, K.A. Schwehr, S. Otosaka, D.I. Kaplan, R. Brinkmeyer, C.M. Yeager, P.H. Santschi: Is soil organic matter a sink or source for radioiodine (129I) at the Savannah River Site?  Geochimica et Cosmochimica Acta 75, 5716-5735 (2011).

Lee, K.-E., B.-K. Khim, S. Otosaka, S. Noriki: Sediment trap record of alkenones from the East Sea (Japan Sea). Organic Geochemistry 42, 255-261 (2011).

Fujita, S., K. Kuma, S. Ishikawa, S. Nishimura, Y. Nakayama, S., Ushizaka, Y. Isoda, S. Otosaka, T. Aramaki: Iron distributions in the water column of the Japan Basin and Yamato Basin (Japan Sea). Journal of Geophysical Research 115, C12001, doi: 10.1029/2010JC006123 (2010).

Nagao, S., T. Irino, T. Aramaki, K. Ikehara, H. Katayama, S. Otosaka, M. Uchida, Y. Shibata: Spatial distribution of Δ14C values of organic matter in surface sediments Off Saru River in northern Japan, one year after a flood event in 2006. Radiocarbon 52, 1068-1077 (2010).

Kawamura, H., T. Ito, T. Kobayashi, S. Otosaka, N. Hirose, O. Togawa: Numerical experiment for strontium-90 and cesium-137 in the Japan Sea. Journal of Oceanography 66, 649-662 (2010).

Morita, T., S. Otosaka, K. Fujimoto, K. Nishiuchi, K. Kimoto, H. Yamada, H. Kasai, M. Minakawa, K. Yoshida: Detection and temporal change of 60Co in the digestive glands of the common octopus, Octopus vulgaris, in the East China Sea. Marine Pollution Bulletin 60, 1193-1199 (2010).

Morita, T., K. Niwa, K. Fujimoto, H. Kasai, H. Yamada, K. Nishiutch, T. Sakamoto, W. Godo, S. Taino, Y. Hayashi, K. Takeno, T. Nishigaki, K. Fujiwara, H. Aratake, S. Kamonoshita, H. Hashimoto, T. Kobayashi, S. Otosaka, T. Imanaka: Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas. Science of Total Environment 408, 3443-3447(2010).

Tanaka, T., S. Otosaka, M. Wakita, H. Amano, O. Togawa: Preliminary result of dissolved organic radiocarbon in the western North Pacific Ocean. Nuclear Instrument and Methods in Physics Research B. 268, 1219-1221, doi:10.1016/j.nimb.2009.10.137 (2010).

Tanaka, T., S. Otosaka, H. Amano, O. Togawa: Development of the analysis system for dissolved organic radiocarbon in large volume seawater by accelerator mass spectrometry. Journal of Nuclear Science and Technology 46, 289-294 (2009).

Otosaka, S., T. Tanaka, O. Togawa, H. Amano, E.V. Karasev, M. Minakawa, S. Noriki: Deep sea circulation of particulate organic carbon in the Japan Sea. Journal of Oceanography 64, 911-923 (2008).

Takata, H., K. Kuma, Y. Isoda, S. Otosaka, T. Senjyu, M. Minakawa: Iron in the Japan Sea and its implications for the physical processes in deep water. Geophysical Research Letters L02606, doi: 1029/ 2007GL031794 (2008).

Aramaki, T., T. Senjyu, O. Togawa, S. Otosaka, T. Suzuki, T. Kitamura, H. Amano, Y.N. Volkov: Circulation in the northern Japan Sea studied chiefly with radiocarbon. Radiocarbon 49, 915-924 (2007).

Togawa, O., T. Ito, S. Otosaka: Transport processes of radionuclides in the Japan Sea obtained by JAEA’s expeditions. Japanese Journal of Health Physics 42, 234-246 (2007).

Ito, T., S. Otosaka, H. Kawamura: Estimation of total amounts of anthropogenic radionuclides in the Japan Sea. Journal of Nuclear Science and Technology 44, 912-922 (2007).

Kobayashi, T., S. Otosaka, O. Togawa, K. Hayashi: Development of a non-conservative radionuclides dispersion model in the ocean and its application to surface 137Cs dispersion in the Irish Sea. Journal of Nuclear Science and Technology 44, 238-247 (2007).

Otosaka, S., H. Amano, T. Ito, H. Kawamura, T. Kobayashi, T. Suzuki, O. Togawa, E.L. Chaykovskaya, T.S. Lishavskaya, V.P. Novichkov, E.V. Karasev, A.V. Tkalin, Y.N. Volkov: Anthropogenic radionuclides in sediment in the Japan Sea: Distribution and transport processes of particulate radionuclides. Journal of Environmental Radioactivity 91, 128-145 (2006).

Otosaka, S., S. Noriki: Relationship between composition of settling particles and organic carbon flux in the western North Pacific and the Japan Sea. Journal of Oceanography 61, 25-40 (2005).

Senjyu, T., Y. Isoda, T. Aramaki, S. Otosaka, S. Fujio, D. Yanagimoto, T. Suzuki, K. Kuma, K. Mori: Benthic front and the Yamato Basin Bottom Water in the Japan Sea. Journal of Oceanography 61, 1047-1058 (2005).

Ito, T., T. Aramaki, S. Otosaka, T. Suzuki, O. Togawa, T. Kobayashi, H. Kawamura, H. Amano, T. Senjyu, E.L. Chaiykovskaya, T.S. Lishavskaya, E.V. Karasev, V.P. Novichikov, A.F. Scherbinin, A.V. Tkalin, Y.N. Volkov: Anthropogenic Radionuclides in Seawater of the Japan Sea: The results of recent observations and the temporal change of concentrations. Journal of Nuclear Science and Technology 42, 90-100 (2005).

Otosaka, S., M.C. Honda, S. Noriki: La/Yb and Th/Sc in settling particles: vertical and horizontal transport of lithogenic material in the western North Pacific. Geochemical Journal 38, 515-525 (2004).

Otosaka, S., M. Baba, O. Togawa, E. Karasev, Y. Volkov, N. Omata, S. Noriki: Lithogenic flux in the Japan Sea measured with sediment traps. Marine Chemistry 91, 143-163 (2004).

Otosaka, S., M. Baba, O. Togawa, E.V. Karasev: Fluxes and balance of 210Pb in the northwestern Japan Sea. Pacific Oceanography 1, 149-157 (2003).

濱原和広, 重光雅仁, 乗木新一郎, 福山龍次, 荒巻能史, 乙坂重嘉: 石狩湾堆積物中の高いC/N比の有機物と重金属. 沿岸海洋研究 41, 53-60 (2003).

Ito, T., T. Aramaki, T. Kitamura, S. Otosaka, T. Suzuki, O.Togawa, T. Kobayashi, T. Senjyu, E.L. Chaykovskaya. E.V. Karasev, T.S. Lishavskaya, V.P. Novichkov, A.V. Tkalin, A.F. Sherbinin, Y.N. Volkov: Anthropogenic radionuclides in the Japan Sea: Their distributions and transport processes. Journal of Environmental Radioactivity 68, 249-267 (2003).

Senjyu, T., T. Aramaki, S. Otosaka, T. Kobayashi, O. Togawa, M. Takematsu, T. Suzuki, Y. Volkov, E. Karasev, M. Danchenkov: Renewal of the bottom water after the winter 2000-2001 may spin-up the thermohaline circulation in the Japan Sea. Geophysical Research Letters 29, 10.1029/2001GL014093 (2002).

Otosaka, S., S. Noriki: REEs and Mn/Al ratio of settling particles: horizontal transport of particulate material in the northern Japan Trench. Marine Chemistry 72, 329-342 (2000).

乗木新一郎, 佐々木建一, 乙坂重嘉:  噴火湾における粒子の挙動.  沿岸海洋研究 38, 39-45 (2000).