Researcher Profile and Settings

Master

Affiliation (Master)

• Faculty of Environmental Earth Science　Integrated Environmental Science　Environmental Adaptation Science

Affiliation (Master)

• Faculty of Environmental Earth Science　Integrated Environmental Science　Environmental Adaptation Science

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Profile and Settings

Degree

• Ph.D., in Chemistry（The University of Tokyo）
• Ph.D., in Chemistry（The University of Tokyo）

Profile and Settings

• Name (Japanese)

  Toyoda

• Name (Kana)

  Kazuhiro

• Name

  200901032485943240

Alternate Names

http://www.ees.hokudai.ac.jp/ems/stuff/toyoda/SeigLab_en/Welcome.html

Achievement

Research Interests

• 環境微生物   地球科学   放射化学   鉱物化学   元素分析   無機地球化学   環境化学   Radiochemistry   Environmental Geochemistry   Analytical Geochemistry   Environmental Mineralogy   isotope Geochemistry   Inorganic Geochemistry   Paleolimnology   Bioremediation   

Research Areas

• Natural sciences / Space and planetary science

Research Experience

• 2005 - 2006 大学院地球環境科学研究院環境起学専攻 助教授
• 2005 - 2006 Associate Professor
• 2006 - 大学院環境科学院 環境起学専攻 准教授
• 1995 - 2005 大学院地球環境科学研究科物質環境科学専攻 助教授
• 1995 - 2005 Associate Professor
• 1993 - 1995 東京大学助手（大学院理学系研究科鉱物学専攻） 助手
• 1993 - 1995 Research Associate
• 1988 - 1993 東京大学助手（理学部鉱物学教室） 助手
• 1988 - 1993 Research Associate

Education

•        - 1987  The University of Tokyo
•        - 1987  The University of Tokyo  Graduate School, Division of Science
•        - 1984  The University of Tokyo
•        - 1984  The University of Tokyo  Graduate School, Division of Science
•        - 1982  The University of Tokyo  Faculty of Science
•        - 1982  The University of Tokyo  Faculty of Science

Published Papers

• Geochemical identification of particulate lead pollution in shallow groundwater in inhabited areas in Kabwe, Zambia

  Kazuhiro Toyoda, Shota Nakano, Shunitz Tanaka, Kawawa Banda, Imasiku A. Nyambe, Tsuyoshi Ishikawa, Shouta Nakayama, Mayumi Ishizuka

  Applied Geochemistry 139 105215 - 105215 0883-2927 2022/04
• Humic acid attachment on chitosan-modified silica gel as an economical, efficient, and selective adsorbent for thorium and uranium removal

  Erik Prasetyo, Kazuhiro Toyoda

  Environmental Technology 1 - 15 0959-3330 2021/08/29 [Refereed]
  
• Coupled benthic–hyporheic responses of macroinvertebrates to surface water pollution in a gravel-bed river

  Junjiro N. Negishi, Aiko Hibino, Kazuki Miura, Ryota Kawanishi, Nozomi Watanabe, Kazuhiro Toyoda

  Freshwater Science 38 (3) 591 - 604 2161-9549 2019/09 [Refereed][Not invited]
   

  Interactions between the hyporheic and benthic zones play a vital role in maintaining the integrity of river ecosystems, but simultaneous assessments of hyporheic and benthic macroinvertebrate responses to surface water pollution are limited. We examined how hyporheic (50 cm below surface) and benthic (surface) invertebrates responded to water pollution that originated from a point source (wastewater treatment plant) in a gravel-bed river in Hokkaido, Japan. Dissolved nutrient levels and algal biomass were significantly higher at sample sites down- than upstream of the point source. Furthermore, nitrate concentrations increased gradually from up- to downstream sites, which suggest the presence of diffuse pollution sources in the surrounding areas. Closely synchronized fluctuations of water temperature and similar water quality in the surface and hyporheic zones indicated that the hyporheic zone was highly hydrologically interactive with the surface water. Chloroperlidae (mostly Alloperla ishikariana) had a disproportionately high abundance in the hyporheic zone relative to the benthic zone, regardless of the surface water quality. Numerically dominant invertebrate taxa increased in abundance below the point source of pollution in both the benthic and hyporheic habitats. High N stable isotope ratios (SIR) of the invertebrates in both habitat types indicated that invertebrates assimilated anthropogenic N via the ingestion of pollution-contaminated food resources. End-member mixing analyses based on C SIR demonstrated that assimilation of anthropogenic N occurred because of the increase in available food resources originating from the biofilm. The trophic structure of invertebrates changed less markedly in the hyporheic zone than in the benthic zone, suggesting that the hyporheic assemblage was less sensitive than the benthic assemblage to the changes in surface water quality. Overall, our findings showed that the numeric responses of the invertebrate assemblage to anthropogenic changes in surface water quality were similar and coupled between the benthic and hyporheic zones.
• Selective Ion Exchange in Supramolecular Channels in the Crystalline State.

  Katsuya Ichihashi, Daisuke Konno, Kseniya Yu. Maryunina, Katsuya Inoue, Kazuhiro Toyoda, Shogo Kawaguchi, Yoshiki Kubota, Yoko Tatewaki, Tomoyuki Akutagawa, Takayoshi Nakamura, Sadafumi Nishihara

  Angew. Chem. Int. Ed. 58 (13) 4169 - 4172 2019 [Refereed][Not invited]
  
• Optimizing Lithium Ion Conduction through Crown Ether-Based Cylindrical Channels in [Ni(dmit)(2)](-) Salts

  Katsuya Ichihashi, Daisuke Konno, Takuya Date, Takumi Nishimura, Kseniya Yu Maryunina, Katsuya Inoue, Toshimi Nakaya, Kazuhiro Toyoda, Yoko Tatewaki, Tomoyuki Akutagawa, Takayoshi Nakamura, Sadafumi Nishihara

  CHEMISTRY OF MATERIALS 30 (20) 7130 - 7137 0897-4756 2018/10 [Refereed][Not invited]
   

  The synthesis of artificial ion channels is one of the core areas of biomimetics and is aimed at achieving control over channel functionality by careful design and selection of the constituent components. However, the optimization of ionic conductivity in the channel in the crystalline state is challenging because of crystal strain, polymorphism, and potentially limited stability. In this study, the pore size of cylindrical channels was controlled with the aim of optimizing ionic conductivity. We prepared two isomorphic salts, Li-2([18]crown-6)(3)[Ni-(dmit)(2)](2)(H2O)(4) (1) and Li-2([15]crown-5)(3)[Ni(dmit)(2)](2)(H2O)(2) (2), both of which possess ion channels formed by a one-dimensional array of crown ethers, Li + ions, and crystalline water molecules. Meanwhile, [Ni(dmit)(2)] - (S = 1/2) molecules formed a ladder configuration with J(rung)/k(B) = -631(5) K, J(l)(eg)/k(B) = -185(5) K for 1, and J(rung)/k(B) = -S17(4) K, J(l)(eg)/k(B) = -109(5) K for 2. For 1, the Li+ ionic conductivity at 293 K in the crystalline state was enhanced from 1.89(18) x 10(-8) S.cm(-1) to 2.46(6) X 10(-7) S.cm(-1) via dehydration. Furthermore, analysis of Li+ ionic conductivities of 2, which incorporated a crown ether with a smaller cavity (the cavity diameters of [18]crown-6 and [15]crown-5 are 2.60-3.20 angstrom and 1.70-2.20 angstrom, respectively) at the same temperature both before and after dehydration revealed conductivities of 1.93(31) X 10(-8) S.cm(-1) and 7.01(21) X 10(-7) S.cm(-1), respectively. This molecular design approach can contribute to increasing the ionic conductivity as well as the development of all-solid-state lithium ion batteries and other electronic device fabrications.
• Solid phase extraction of thorium and uranium and their separation from lanthanides using humic acid silica gel as a low-cost adsorbent

  Erik Prasetyo, Kazuhiro Toyoda

  Journal of Engineering and Technological Sciences 49 (4) 508 - 519 2337-5779 2017 [Refereed][Not invited]
   

  Solid phase extraction and separation of thorium (Th), uranium (U) and lanthanides were achieved using a humic acid-modified silica gel (Si-HA). Adsorption capacity, effect of contact time, pH, and adsorbent dose were examined at room temperature. The maximum adsorbent capacities (pH = 3) for Th and U were 28.0 and 31.3 mg g-1, respectively. The isotherm parameters denoted that the adsorption was favorable and optimum conditions were attained within 90 min. The kinetic data conformed well to pseudo-second order and intra-particle diffusion models. The distribution coefficients of U, Th and lanthanides in EDTA, citric acid and nitric acid media signify the possible separation of each element from the others. The salinity did not significantly affect the ability of Si-HA to extract Th and U. The adsorbent stability and reusability were also assessed through four-adsorption-desorption cycles. The simplicity of the proposed separation method along with the stability of the adsorbent and high regeneration efficiency under acidic conditions demonstrated the merit of using Si-HA as a low-cost adsorbent.
• Sol-gel synthesis of a humic acid-silica gel composite material as low-cost adsorbent for thorium and uranium removal

  Erik Prasetyo, Kazuhiro Toyoda

  JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY 310 (1) 69 - 80 0236-5731 2016/10 [Refereed][Not invited]
   

  A new humic acid-silica gel composite (HASi) to serve as an adsorbent was synthesized via a single-pot method, and its formation via the sol-gel process was confirmed by FTIR and SEM-EDS characterization. The adsorbent effectively removed Th and U at low pH (2.5-3), and the Langmuir model yielded a maximum sorption capacity of 32.3 and 33.2 mg/g for Th and U, respectively. The removal process was rapid (85 % removal within 5 min) and followed a pseudo-second-order model. The salinity of the solution had little effect on the removal efficiency, which continued throughout the adsorbent's repeated use up to nine times.
• Kinetics of Mn(II) oxidation by spores of the marine Bacillus sp SG-1

  Kazuhiro Toyoda, Bradley M. Tebo

  GEOCHIMICA ET COSMOCHIMICA ACTA 189 58 - 69 0016-7037 2016/09 [Refereed][Not invited]
   

  The kinetics of Mn(II) oxidation by spores of the marine Bacillus sp. SG-1 was measured under controlled conditions of the initial Mn(II) concentration, spore concentration, chemical speciation, pH, O-2, and temperature. Mn(II) oxidation experiments were performed with spore concentrations ranging from 0.7 to 11 x 10(9) spores/L, a pH range from 5.8 to 8.1, temperatures between 4 and 58 degrees C, a range of dissolved oxygen from 2 to 270 mu M, and initial Mn(II) concentrations from 1 to 200 mu M. The Mn(II) oxidation rates were directly proportional to the spore concentrations over these ranges of concentration. The Mn(II) oxidation rate increased with increasing initial Mn(II) concentration to a critical concentration, as described by the Michaelis-Menten model (Km = ca. 3 mu M). Whereas with starting Mn(II) concentrations above the critical concentration, the rate was almost constant in low ionic solution (I = 0.05, 0.08). At high ionic solution (I = 0.53, 0.68), the rate was inversely correlated with Mn(II) concentration. Increase in the Mn(II) oxidation rate with the dissolved oxygen concentration followed the Michaelis-Menten model (Km = 12-19 mu M DO) in both a HEPES-buffered commercial drinking (soft) water and in artificial and natural seawater. Overall, our results suggest that the mass transport limitations of Mn(II) ions due to secondary Mn oxide products accumulating on the spores cause a significant decrease of the oxidation rate at higher initial Mn (II) concentration on a spore basis, as well as in more concentrated ionic solutions. The optimum pH for Mn(II) oxidation was approximately 7.0 in low ionic solutions (I = 0.08). The high rates at the alkaline side (pH > 7.5) may suggest a contribution by heterogeneous reactions on manganese bio-oxides. The effect of temperature on the Mn(II) oxidation rate was studied in three solutions (500 mM NaCl, ASW, NSW solutions). Thermal denaturation occurred at 58 degrees C and spore germination was evident at 40 degrees C in all three solutions. The activation energies calculated from the Arrhenius plots are consistent with the observation that Ca ions stimulate the Mn(II) oxidation rate. (C) 2016 Elsevier Ltd. All rights reserved.
• Late Quaternary tephrostratigraphy of Baegdusan and Ulleung volcanoes using marine sediments in the Japan Sea/East Sea

  Chungwan Lim, Kazuhiro Toyoda, Ken Ikehara, David W. Peate

  QUATERNARY RESEARCH 80 (1) 76 - 87 0033-5894 2013/07 [Refereed][Not invited]
   

  Only Ulleung and Baegdusan volcanoes have produced alkaline tephras in the japan Sea/East Sea during the Quaternary. Little is known about their detailed tephrostratigraphy, except for the U-Old and B-Tm tephras. Trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast Five sediment cores spanning the interval between the rhyolitic AT (29.4 ka) and Aso-4 (87 ka) tephras were analyzed using an INAA scanning method. Source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand-picked glass shards: Ulleung (U-Ym, and the newly identified U-Sado), and Baegdusan (B-J, and the newly identified B-Sado and B-Ym). The eruption ages of the U-Ym, U-Sado, B-J, B-Sado, and B-Ym tephras are estimated to be 38 ka, 61 ka, 26 ka, 51 ka, 68-69 ka, and 86 ka, respectively, based on correlations with regional-scale TL (thinly laminated) layer stratigraphy (produced by basin-wide changes in bottom-water oxygen levels in response to millennium-scale paleoclimate variations). This study has allowed construction of an alkaline tephrostratigraphical framework for the late Quaternary linked to global environmental changes in the Japan Sea/East Sea, and improves our knowledge of the eruptive histories of Ulleung and Baegdusan volcanoes. Crown Copyright (C) 2013 Published by Elsevier Inc. on behalf of University of Washington. All rights reserved.
• The effect of Ca2+ ions and ionic strength on Mn(II) oxidation by spores of the marine Bacillus sp SG-1

  Kazuhiro Toyoda, Bradley M. Tebo

  GEOCHIMICA ET COSMOCHIMICA ACTA 101 1 - 11 0016-7037 2013/01 [Refereed][Not invited]
   

  Manganese(IV) oxides, believed to form primarily through microbial activities, are extremely important mineral phases in marine environments where they scavenge a variety of trace elements and thereby control their distributions. The presence of various ions common in seawater are known to influence Mn oxide mineralogy yet little is known about the effect of these ions on the kinetics of bacterial Mn(II) oxidation and Mn oxide formation. We examined factors affecting bacterial Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1 in natural and artificial seawater of varying ionic conditions. Ca2+ concentration dramatically affected Mn(II) oxidation, while Mg2+, Sr2+, K+, Na+ and NO3- ions had no effect. The rate of Mn(II) oxidation at 10 mM Ca2+ (seawater composition) was four or five times that without Ca2+. The relationship between Ca2+ content and oxidation rate demonstrates that the equilibrium constant is small (on the order of 0.1) and the binding coefficient is 0.5. The pH optimum for Mn(II) oxidation changed depending on the amount of Ca2+ present, suggesting that Ca2+ exerts a direct effect on the enzyme perhaps as a stabilizing bridge between polypeptide components. We also examined the effect of varying concentrations of NaCl or KNO3 (0-2000 mM) on the kinetics of Mn(II) oxidation in solutions containing 10 mM Ca2+. Mn(II) oxidation was unaffected by changes in ionic strength (I) below 0.2, but it was inhibited by increasing salt concentrations above this value. Our results suggest that the critical coagulation concentration is around 200 mM of salt (I = ca. 0.2), and that the ionic strength of seawater (I > 0.2) accelerates the precipitation of Mn oxides around the spores. Under these conditions, the aggregation of Mn oxides reduces the supply of dissolved O-2 and/or Mn2+ and inhibits the Mn(II) -> Mn(III) step controlling the enzymatic oxidation of Mn(II). Our results suggest that the hardness and ionic strength of the aquatic environment at circumneutral pH strongly influences the rate of biologically mediated Mn(II) oxidation. (C) 2012 Elsevier Ltd. All rights reserved.
• Sedimentary records of metal deposition in Japanese alpine lakes for the last 250years: Recent enrichment of airborne Sb and In in East Asia

  Michinobu Kuwae, Narumi K. Tsugeki, Tetsuro Agusa, Kazuhiro Toyoda, Yukinori Tani, Shingo Ueda, Shinsuke Tanabe, Jotaro Urabe

  Science of the Total Environment 442 189 - 197 0048-9697 2013 [Refereed][Not invited]
   

  Concentrations of 18 elements, including Sb, In, Sn, and Bi, were measured in sediment cores from two pristine alpine lakes on Mount Hachimantai, northern Japan, representing the past 250years. Vertical variations in concentrations are better explained by atmospheric metal deposition than by diagenetic redistribution of Fe and Mn hydroxide and organic matter. Anthropogenic metal fluxes were estimated from 210Pb-derived accumulation rates and metal concentrations in excess of the Al-normalized mean background concentration before 1850. Anthropogenic fluxes of Sb and In showed gradual increases starting around 1900 in both lakes, and marked increases after 1980. Comparison of Sb/Pb and Pb stable isotope ratios in sediments with those in aerosols of China or northern Japan and Japanese source materials (recent traffic- and incinerator-derived dust) suggest that the markedly elevated Sb flux after 1980 resulted primarily from enhanced long-range transport in aerosols containing Sb and Pb from coal combustion on the Asian continent. The fluxes of In, Sn, and Bi which are present in Chinese coal showed increasing trends similar to Sb for both study lakes. This suggests that the same source although incinerators in Japan may not be ruled out as sources of In. The sedimentary records for the last 250years indicate that atmospheric pollution of Sb and In in East Asia have intensified during recent decades. © 2012 Elsevier B.V.
• New technique for the determination of trace elements using multiparameter coincidence spectrometry.

  Hatsukawa, Yuichi, Toh, Yosuke, Oshima, Masumi, Hayakawa, Takehito, Shinohara, Nobuo, Kushita, Kohei, Ueno, Takashi, Toyoda, Kazuhiro

  Journal of Radioanalytical and Nuclear Chemistry 255 (1) 111 - 113 2013 [Refereed][Not invited]
  
• B1-10 Late Quaternary tephrostratigraphy of Baegdusan and Ulleung volcanoes using marine sediments in the Japan Sea/East Sea

  Lim Chungwan, Toyoda Kazuhiro, Ikehara Ken

  PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN 特定非営利活動法人日本火山学会 2013 61 - 61 2013
• Eutrophication of mountain lakes in Japan due to increasing deposition of anthropogenically produced dust

  Narumi K. Tsugeki, Tetsuro Agusa, Shingo Ueda, Michinobu Kuwae, Hirotaka Oda, Shinsuke Tanabe, Yukinori Tani, Kazuhiro Toyoda, Wan-lin Wang, Jotaro Urabe

  ECOLOGICAL RESEARCH 27 (6) 1041 - 1052 0912-3814 2012/11 [Refereed][Not invited]
   

  Atmospheric dust has wide-reaching effects, not only influencing climate conditions, but also ecosystems. The eastern region of the Asian continent is one of the largest emitters of dust in the world, and recent economic growth in the region has been accompanied by an increase in anthropogenic emissions. However, the effects of increased Asian dusts on aquatic ecosystems are not well understood. We examined fossil pigments and zooplankton remains from Pb-210-dated sediments taken from high mountain lakes of Hourai-Numa and Hachiman-Numa, located in the Towada-Hachimantai National Park of Japan Islands, to uncover historical changes in the phyto-and zooplankton community over the past 100 years. Simultaneously, we measured the geochemical variables of TOC, TN, TP, delta C-13, delta N-15, and lead isotopes (Pb-207/Pb-206, Pb-208/Pb-206) in the sediments to identify environmental factors causing such changes. As a result, despite few anthropogenic activities in the watersheds, alpine lakes in Japan had increased algal and herbivore plankton biomasses by 3-6 fold for recent years depending on the surrounding terrestrial vegetation and landscape conditions. Biological and biogeochemical proxies recorded from the lake sediments showed that this eutrophication occurred after the 1990s when P deposition increased as a result of atmospheric loading of dust transported from the Asian continent. The continued increase of anthropogenically produced dust may therefore impart damaging impacts on mountain ecosystems even if they are protected from direct anthropogenic disturbances.
• Structure, Magnetism, and Ionic Conductivity of the Gigantic {Mo-176}-Wheel Assembly: Na15Fe3Co16[Mo176O528H3(H2O)(80)]Cl-27 center dot 450H(2)O

  Hiroyuki Imai, Tomoyuki Akutagawa, Fumito Kudo, Mitsuhiro Ito, Kazuhiro Toyoda, Shin-ichiro Noro, Leroy Cronin, Takayoshi Nakamura

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 131 (38) 13578 - + 0002-7863 2009/09 [Refereed][Not invited]
   

  Single crystals of the nanoscale polyoxomolybdate wheel, Na15Fe3Co16[Mo176O528(H2O)(80)]Cl-27 center dot 450H(2)O, was synthesized by the condensation reaction of Na0.4Co0.8[MoO4]center dot 1.5H(2)O at low pH and in the presence of an iron-based reducing agent, and these crystals were characterized by the synchrotron-based X-ray single crystal analysis, magnetic susceptibility, and ionic conductivity measurements.
• Cryptotephra detection using high-resolution trace-element analysis of Holocene marine sediments, southwest Japan

  Chungwan Lim, Ken Ikehara, Kazuhiro Toyoda

  GEOCHIMICA ET COSMOCHIMICA ACTA 72 (20) 5022 - 5036 0016-7037 2008/10 [Refereed][Not invited]
   

  Detection techniques for invisible tephra, known as cryptotephra, have been exploited to construct precise and high-resolution correlations for a broad range of sedimentary sequences. We demonstrate that continuous trace-element profiles are an effective means for detecting probable positions of distal cryptotephra in Holocene hemipelagic sediments. Instrumental neutron activation analyses were performed on specimens of bulk sediments from five piston and gravity cores (water depths: 300-1500 m) taken from the southern Japan/East Sea. The down-core variations in the Ta/Sc ratio identify the positions of one to three alkaline cryptotephra in four of these cores. The Cr/Sc profiles show the position of one rhyolitic cryptotephra in three of the cores. The existence of tephra-derived components (glass +/- crystals) was confirmed by microscopic observation, SEM-EPMA analysis and refractive index measurement on grains extracted from these layers. Based on microscopic observation and the stratigraphic correlations between cores, we identified eruption ages of the cryptotephras at 6.3, 7.5 and 9.3 C-14 kyr BP, and two source volcanoes around 800 and 400 km from the study area. The tephra layers visible to the naked eye contained volcanic grains coarser than 200 mu m, and the alkaline and rhyolitic tephra component comprised >20% and >33% of the sediment on weight basis, respectively. In contrast, the range of particle sizes of the cryptotephras detected in this study is finer than 125 mu m, and almost all of the glass shards were finer than 40 Pm. The alkaline and rhyolitic cryptotephras made up only 2-17% and 22-24%, respectively, of the sediment on weigh basis. The high sensitivity of this method stems from the significant difference in trace-element contents between the tephras and enclosing hemipelagic sediments in the core. Alkaline U-Oki tephra was enriched in Ta by one order of magnitude over that of the sediment, and depleted in Sc by one order. The rhyolitic tephra, K-Ah, was depleted by about one order in Cr relative to that of enclosing the sediment. The differences in chemical composition between within-plate alkaline tephras and hemipelagic sediments are usually so large that trace-element geochemical method is likely to be useful for alkaline cryptotephra detection in other areas with similar tectonic characteristics. (C) 2008 Elsevier Ltd. All rights reserved.
• Main controlling factors of coral skeletal carbon isotopic composition and skeletal extension rate: High-resolution study at Hainan Island, South China Sea

  Michiyo Shimamura, Tomohisa Irino, Tadamichi Oba, Guoqiang Xu, Bingquan Lu, Luejiang Wang, Kazuhiro Toyoda

  GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 9 (Q04024) 1525-2027 2008/04 [Refereed][Not invited]
   

  To understand the main controlling factors of coral skeletal carbon isotope ratio (delta(13)Cc), we undertook high-temporal- resolution (similar to 1.5 d) measurements of delta(13)Cc for Porites lutea collected from the east coast of Hainan Island, China. The results were compared with factors that have previously been proposed to control coral delta(13)Cc: skeletal extension rate, carbon isotope composition of dissolved inorganic carbon in seawater (delta(13)Cw), and light availability to the coral colony. Hainan Island is characterized by strong summer and winter monsoons that result in distinctive seasonal variations in environmental and coral growth conditions. Compared with other tropical/ subtropical areas, this climate is advantageous in evaluating the effects of different environmental factors on delta(13)Cc. We found that delta(13)Cc varied in phase with solar radiation. Increased total suspended matter (TSM) in the water column was found to reduce delta(13)Cc. These data suggest that light availability, the interplay between solar intensity and attenuation of light by TSM in the water column, is the main controlling factor of delta(13)Cc in the studied coral. In addition, slower skeletal extension was found during periods of lower solar radiation and high turbidity than other periods of similar temperature conditions, suggesting that both factors influence skeletal growth. Seasonal variations in delta(13)Cw were not only too narrow in range to explain the observed delta(13)Cc, but also showed an opposite trend to that of delta(13)Cc. We also failed to detect delta(13)Cc variations due to the kinetic isotope effect (i.e., the discrimination of heavier isotopes during CO2 hydration and hydroxylation and the resulting simultaneous negative shifts of delta(13)Cc and delta(18)Oc from equilibrium values), despite large variations in the measured skeletal extension rate. This outcome probably reflects the high skeletal extension rates of the studied coral (average, 15 mm/a; minimum, 4 mm/a).
• Construction of an alkaline tephrostratigraphical framework of the late Quaternary by INAA-scanning of sediment cores in the Japan Sea

  Lim Chungwan, Ikehara ken, Toyoda Kazuhiro

  Abstracts of Annual Meeting of the Geochemical Society of Japan 日本地球化学会 55 419 - 419 2008 

  古気候変動を研究する際に、高密度に堆積物中のテフラ層準を特定できれば、離れた地域の同一時間面が確実に特定できるため、肉眼では検出できないほど希薄なテフラ層（クリプトテフラ）の検出法にも注目が集まっている。堆積層を１cm毎に連続して分取して中性子放射化分析を行って得られる微量元素の垂直分布がクリプトテフラの検出に有用であることを示し、日本地質調査所の研究航海で採取された日本海南部から東部にかけての数本の海底コア中の１万年前から９万年前の堆積層から、韓国・鬱陵島系の火山または中朝国境の白頭山を給源とするアルカリ岩質クリプトテフラ層およだを複数検出している。これらの検出層から抽出したテフラ粒の主成分・微量元素の定量を行い、噴火毎の化学成分の違いを特定する事で、これまで不明な点が多かった日本海における第四紀後期のアルカリ岩質テフラの層序を構築しつつあるので、その成果を報告する。
• High-sensitive elemental analysis using multi-parameter coincidence spectrometer: GEMINI-II

  Y. Hatsukawa, Y. Miyamoto, Y. Toh, M. Oshima, M. Hosein Mahmudy Gharaie, K. Goto, K. Toyoda

  JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY 272 (2) 273 - 276 0236-5731 2007/05 [Refereed][Not invited]
   

  In this study, using neutron activation analysis with multi-parameter coincidence method which was developed at Japan Atomic Energy Agency (JAEA), a non-destructive, ultra-high sensitive multi-elemental determination has been realized. The multi-parameter coincidence method is carried out with an array of 19 germanium detectors, GEMINI-II. Using this system, very weak gamma-rays emitted from trace amounts of elements can be detected. The iridium concentration has been determined by means of neutron activation analysis with multi-parameter coincidence method for Cuban sediment samples across the K/T boundary strata.
• Sea surface temperature record off central Japan since the Last Glacial Maximum using planktonic foraminiferal Mg/Ca thermometry

  T Sagawa, K Toyoda, A Tadamichi

  JOURNAL OF QUATERNARY SCIENCE 21 (1) 63 - 73 0267-8179 2006/01 [Refereed][Not invited]
   

  We conducted paired measurements of the Mg/Ca ratio and delta O-18 of planktonic foraminifera, Globigerina bulloides, from a sediment core (MD01-2420) off central Japan in the northwest Pacific, to reconstruct Current movements since the Last Glacial Maximum (LGM). These methods make it possible to determine the magnitude and timing of the sea Surface temperature (SST) changes and to reconstruct the variations of the past seawater delta O-18 (delta(18)Ow) off central Japan. The amplitude of Mg/Ca-based SST changes between the Holocene and the LGM was about 10 degrees C. The strong resemblance of the SSTs estimated from both methods, Mg/Ca-based and delta O-18-based, Suggests that the SST changes were caused primarily by latitudinal displacement of the Kuroshio-Oyashio currents and no distinct change in the carbonate dissolution of the core. The southward migration of the water mass was 5-6 degrees in latitude at the LGM. The values for regional delta(18)Ow changes, which were obtained by subtracting the ice volume contribution from the calculated delta(18)Ow, describe the millennial-scale water mass migration over the last 30 kyr. Copyright (c) 2005 John Wiley & Sons, Ltd.
• Fidelity of delta O-18 as a proxy for sea surface temperature: Influence of variable coral growth rates on the coral Porites lutea from Hainan Island, China

  M Shimamura, T Oba, GQ Xu, BQ Lu, LJ Wang, M Murayama, K Toyoda, A Winter

  GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 6 (Q09017) 09017  1525-2027 2005/09 [Refereed][Not invited]
   

  [1] The extremely high temporal resolution ( nearly daily interval) measurement was conducted on the coral (Porites lutea) oxygen isotope compositions (delta(18)Oc) to examine the detailed relationship between delta(18)Oc and sea surface temperature (SST) and seawater oxygen isotope composition (delta(18)Ow) from Hainan Island, China. Although SST and sea surface salinity (SSS) or delta(18)Ow varied in a wide range at the studied site, the dynamic range of delta(18)Oc recorded in coral was much smaller than expected from SST and SSS (delta(18)Ow) changes. The extremely high (> 30 degrees C) and low (< 22 degrees C) SST and low (< 27) SSS are not suitable for coral calcification, and coral could not record the information as their skeletal delta(18)O. Estimated coral extension rates ( the overall rate is 15 mm/year) varied by a factor of about 18 within one year, from very slow in winter to very fast in spring. Light availability could affect the extension rate of coral skeleton through the activity of photosynthesis of symbiont algae. Such cessation and acceleration of calcification cause a serious distortion of the delta(18)O profile, which makes it difficult to make a correlation between delta(18)O and SST. Because high and low extension rates correspond to low- and high-density bands, respectively, a detailed examination of the density structure may assist the correction for distortion of the delta(18)O profile.
• Validation of arsenic as a proxy for lake-level change during the past 40,000 years in Lake Biwa, Japan

  K Toyoda, Y Shinozuka

  QUATERNARY INTERNATIONAL 123 51 - 61 1040-6182 2004 [Refereed][Not invited]
   

  Lake Biwa is the largest lake in Japan. It is a semi-closed lake surrounded by active faults, and was oxygen-rich prior to the Industrial Revolution. In this lake, arsenic concentration in core sediments was proposed as a proxy for lake-level change, due to a strong correlation between As concentration in recent sediments and water depth. Detailed elemental variations from two piston cores from water depths of 76 and 67 m were obtained from the center of the lake to examine the possible correspondence between As concentrations and paleo-environmental change during the past 40,000 years. The vertical Fe distribution pattern indicates that precipitated Fe hydroxide, the adsorbent of As ions from lake water, has been preserved in buried sediment due to oxic conditions. The change in the Ti/Al ratio suggests that the rapid drop of As content through the last several centuries is due to the increasing inflow of clayey materials generated by human activity, diluting the hydrogenous component. The As contents are fairly constant between 2000 and 9000 yr BP, and the fluctuation of equivalent water depth was 10 m at most. The increase of As content and equivalent water depth during the last two millennia should be coincident with the lake-level rise event at about 2000 yr BP, as suggested by previous investigations. However, during the last 40 kyr the extent of change of equivalent water depth is too large to explain only by tectonic movement. From about 40 cal. kyr BP to 30 cal. kyr BP, As contents significantly increased, and then gradually decreased until mid-Holocene. The change at 30 cal. kyr BP should correspond with climatic change, from wet to dry, at the marine oxygen stage 2/3 transition, with some time lag. Increases of As content are synchronized with events marked by abrupt increases in precipitation. Arsenic was dissolved in lake water as a consequence of rock and soil weathering around Lake Biwa, and then immediately precipitated with iron hydroxide into the take sediment. Our results revealed that the historical change of As contents in core samples was influenced by the amount of As inflow to the lake from the watershed area, as well as by lake-level change. Chemical analysis of the extracts of the hydrogenous component of the samples confirmed this hypothesis. (C) 2004 Elsevier Ltd and INQUA. All rights reserved.
• Paleo-phosphorus loading to Lake Biwa in Japan anterior to the urban-industrial activity

  K Toyoda

  GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A489 - A489 0016-7037 2003/09 [Refereed][Not invited]
  
• Chemical composition of a drilled core of Lake Biwa in Japan and implications for source changes during the past 430,000 years

  K Toyoda

  QUATERNARY INTERNATIONAL 105 57 - 69 1040-6182 2003 [Refereed][Not invited]
   

  Neutron activation analysis was performed on sediments taken from the 250 in thick sediment bed of Lake Biwa, which is composed entirely of lacustrine clay and records palco-environmental change over the past 430,000 years. A comparison is made between the geochemical compositions of cores from the center of Lake Biwa, and lacustrine surface and terrestrial sediments from around Lake Biwa, to estimate past changes in sediment sources. Time series of Th/Sc ratios are synchronized with glacial-interglacial climatic change and also correlated with the reported aeolian quartz flux data. Th/Sc ratios during the delta(18)O stages 1, 5, 7, 9 and 11 are approximately 1.1-1.2, whereas Th/Sc ratios during the 6180 stages 2, 4, 6, 8 and 10 are approximately 1.0-1.1. The possibility of a contribution from the mafic area in the northwestern shore of Lake Biwa, which has low Th/Sc ratios (ca. 0.8), is excluded by the Ti/Al ratio data. As aeolian dust flux to the downwind area from the Asian desert area is higher during glacial times, this data suggests that aeolian dust reaching Japan has an unexpectedly low Th/Sc ratio of source material, and/or that there was a large shift in the amount of dust flux. This assumption remains to be tested by future studies. Th/Sc ratios apparently lag ca. 5000 years behind the marine delta(18)O record during the stage 1/2, 3/4, and 5/6 transitions, which coincides 214, 6 with the aeolian quartz flux variation. Continuous increase of Hf contents from ca. 200,000 years BP could be mainly related to upheaval of the Hf rich and high Th/Sc ratio granite block on the west shore of drilling site by active fault movement. The variations in delivery of high Th/Sc granitic debris has damped the oscillation between Th/Sc ratios of sediments and aeolian dust flux during oxygen isotopic stages 2-3. Both the intermittent increase of Na contents from ca. 430,000 years BP to present, and the abrupt increase of Na content at ca. 140,000 years BP are probably due to the subsidence of the northern basin, as the result of tectonic movement around Lake Biwa. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved.
• New technique for the determination of trace elements using multiparameter coincidence spectrometry

  Y Hatsukawa, Y Toh, M Oshima, T Hayakawa, N Shinohara, K Kushita, T Ueno, K Toyoda

  JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY 255 (1) 111 - 113 0236-5731 2003 [Refereed][Not invited]
   

  Multiparameter coincidence gamma-ray spectrometry based on gamma-gamma coincidence is widely used in the field of nuclear structure studies, and has produced many succesful results. In this paper, feasibility of the method for neutron activation analysis of trace elements was studied. Particularly, a long-lived radioisotope I-129 (T-1/2 = 1.57.10(7) y) in algae samples and iridium in geological samples has been determined.
• K/T boundary deposit in the proto-Caribbean basin.

  H. Takayama, S. Yamamoto, S. Kiyokawa, K. Toyoda, D. Garcia-Delgado, C. Diaz-Otero, R. Rojas-Consuegra

  American association of petroleum Geologists Memoir, 79 582 - 604 2003 [Refereed][Not invited]
  
• Complex tsunami waves suggested by the Cretaceous-Tertiary boundary deposit at the Moncada section, western Cuba

  R. Tada, Y. Nakano, M. A. Iturralde-Vinent, S. Yamamoto, T. Kamata, E. Tajika, K. Toyoda, S. Kiyokawa, D. Garcia Delgado, T. Oji, K. Goto, H. Takayama, R. Rojas-Consuegra, T. Matsui

  Special Paper of the Geological Society of America 356 109 - 123 0072-1077 2002 [Refereed][Not invited]
   

  The Moncada Formation in western Cuba is an ∼2-m-thick weakly metamorphosed complex characterized by repetition of calcareous sandstone units that show overall upward fining and thinning. The Moncada Formation contains abundant shocked quartz, altered vesicular impact-melt fragments, and altered and deformed greenish grains of possible impact glass origin. In addition, a high iridium (∼0.8 ppb) peak is identified at the top of the formation. Together with the biostratigraphically estimated age, between late Maastrichtian and early Paleocene, this evidence supports a Cretaceous-Tertiary (K-T) boundary origin for the deposit. The Moncada Formation has ripple cross-laminations at several horizons that indicate north-south-trending paleocurrent directions with reversals. Changes in detrital provenance corresponding to paleocurrent reversals are also recognized. These characteristics are similar to K-T boundary sandstone complexes reported from the Gulf of Mexico region, and strongly support a K-T boundary tsunami origin for the Moncada Formation. The pattern of paleocurrent reversals in the Moncada Formation suggests that tsunami waves were not simple alternations of a single beat, but rather alternations of double beats following the first wave that came from the south. In addition, the maximum grain-size variation within each unit suggests the presence of higher frequency waves superimposed on the lower frequency waves. Thus, our results suggest that K-T impact tsunami waves had a complex rhythm that was caused either by reflections and diffractions of waves or by multiple tsunami waves created by multiple gravity-flows triggered by seismic shocks of the impact.
• Research on the mass-determination method of As content in soil samples by its capability concerning for the microwave digestion method and epithermal neutron activation analysis

  Y Shinozuka, K Toyoda

  BUNSEKI KAGAKU The Japan Society for Analytical Chemistry 50 (4) 229 - 235 0525-1931 2001/04 [Refereed][Not invited]
   

  We investigated the mass-determination method of As content in soil samples. Both HG (hydride generation)/ICP-AES and HG/AAS combined with the procedure of acid digestion in open vessels are commonly used for As determination in soil and sediment samples, which should shorten the dissolution times. We examined two commercial microwave digestion (MWD) systems to evaluate the possibility fur the MWD of soil and sediment samples. They yielded poor results compared to the recommended values from the literature. This is probably because the resistant organic matter found after MWD contains a significant amount of As, and the residual component hinders a complete dissolution of the samples. We also evaluated the usefulness of ENAA (epithermal neutron activation analysis) for sediment reference samples and a large number of lake sediments, and compared the results with HG/ICP-AES for the mass-determination of as contents. The limit value of the determination (10 sigma) during a routine analysis was about 0.7 ppm in the samples. This is several times higher than that of HG/ICP-AES, but is satisfaction low for the determination of As in almost all soil samples. About 7 days are required for the As determination of 100 sediment samples by routine ENAA, which is equivalent to the time required for HG/ICP-AES. The total amount of actual work of ENAA is significantly less than that of HG/ICP-AES. T We thus realized that ENAA should be recommended for the As determination of a number of sediments and soil samples.
• Origin of the Penalver Formation in northwestern Cuba and its relation to K/T boundary impact event

  H Takayama, R Tada, T Matsui, MA Iturralde-Vinent, T Oji, E Tajika, S Kiyokawa, D Garcia, H Okada, T Hasegawa, K Toyoda

  SEDIMENTARY GEOLOGY 135 (1-4) 295 - 320 0037-0738 2000/09 [Refereed][Not invited]
   

  The uppermost Maastrichtian Penalver Formation and its equivalents in northwestern Cuba are characterized by thick, normal-graded calcarenite with distinct basal conglomerate, and have been suspected as deposits related to the Cretaceous-Tertiary boundary (K/T) impact. However, its depositional mechanism is not well understood and clear evidence for its association with the impact has never been presented. In this study, detailed field survey and petrographic observations were carried out on the Penalver Formation in order to clarify its sedimentary processes and to test its relation to the K/T impact. The Penalver Formation at the type locality near Havana is approximately 180 m thick and is subdivided into the Basal, Lower, Middle, Upper and Uppermost Members based on its lithology. The Basal Member consists of massive, poorly sorted, calcirudite with grain-supported fabric, which contains abundant macrofossils of shallow-marine origin and occasional large intraclasts of the underlying strata, suggesting that it was formed by a grain flow from a carbonate platform on the Cretaceous Cuban Are. The Lower to Uppermost Members consist of massive calcarenite and calcilutite that show upward fining. Composition of the calcarenite is distinctly different from that of the Basal Member. The homogeneous appearance, coarse-tail normal grading, abundant water escape structures, and abundant reworked fossils in these members are consistent with those of the Mediterranean "homogenite", a deep sea tsunami-induced deposit that was formed by settling from a high density suspension. Repetition of thin conglomerate beds in the Lower Member that contain well-sorted, well-rounded mud clasts and shallow marine fossils is considered to reflect intermittent lateral dow possibly induced by a series of tsunami waves during an early stage of settling of grains from a high density suspension. Altered vesicular glass of probable impact origin and shocked quartz are discovered in the Basal and the Lower to Upper Members, respectively. Together with the biostratigraphically constrained age of the Penalver Formation, this evidence suggests that the Penalver Formation has a genetic relation to the K/T impact. Distribution of altered vesicular glass and shocked quartz grains can explain the sequence of the initial grain flow and the following tsunami waves. (C) 2000 Published by Elsevier Science B.V.
• Origin of the Penalver Formation in northwestern Cuba and its relation to K/T boundary impact event

  H. Takayama, R. Tada, T. Matsui, M. A. Iturralde-Vinent, T. Oji, E. Tajika, S. Kiyokawa, D. Garcia, H. Okada, T. Hasegawa, K. Toyoda

  Sedimentary Geology 135 (1-4) 295 - 320 0037-0738 2000 [Refereed][Not invited]
   

  The uppermost Maastrichtian Penalver Formation and its equivalents in northwestern Cuba are characterized by thick, normal-graded calcarenite with distinct basal conglomerate, and have been suspected as deposits related to the Cretaceous-Tertiary boundary (K/T) impact. However, its depositional mechanism is not well understood and clear evidence for its association with the impact has never been presented. In this study, detailed field survey and petrographic observations were carried out on the Penalver Formation in order to clarify its sedimentary processes and to test its relation to the K/T impact. The Penalver Formation at the type locality near Havana is approximately 180 m thick and is subdivided into the Basal, Lower, Middle, Upper and Uppermost Members based on its lithology. The Basal Member consists of massive, poorly sorted, calcirudite with grain-supported fabric, which contains abundant macrofossils of shallow-marine origin and occasional large intraclasts of the underlying strata, suggesting that it was formed by a grain flow from a carbonate platform on the Cretaceous Cuban Arc. The Lower to Uppermost Members consist of massive calcarenite and calcilutite that show upward fining. Composition of the calcarenite is distinctly different from that of the Basal Member. The homogeneous appearance, coarse-tail normal grading, abundant water escape structures, and abundant reworked fossils in these members are consistent with those of the Mediterranean 'homogenite', a deep sea tsunami-induced deposit that was formed by settling from a high density suspension. Repetition of thin conglomerate beds in the Lower Member that contain well-sorted, well-rounded mud clasts and shallow marine fossils is considered to reflect intermittent lateral flow possibly induced by a series of tsunami waves during an early stage of settling of grains from a high density suspension. Altered vesicular glass of probable impact origin and shocked quartz are discovered in the Basal and the Lower to Upper Members, respectively. Together with the biostratigraphically constrained age of the Penalver Formation, this evidence suggests that the Penalver Formation has a genetic relation to the K/T impact. Distribution of altered vesicular glass and shocked quartz grains can explain the sequence of the initial grain flow and the following tsunami waves. (C) 2000 Published by Elsevier Science B.V.
• A catalytic hydrogen wave of the osmium-cysteine system

  M Kawasaki, T Kakizaki, WH Hu, K Toyota, K Hasebe

  ELECTROANALYSIS 10 (4) 276 - 278 1040-0397 1998/04 [Refereed][Not invited]
   

  In the presence of cysteine, osmium(VIII) in hydrochloric acid exhibits a will-defined maximum wave at -0.85 V (vs. SCE). Effects of the osmium's valence states and the coexisting anions on the reduction wave have been studied polarographically in acidic solution. The high oxidation states (e.g., osmium(VIII) and (VI)) in comparison with low oxidation states have an influence on the height of the hydrogen wave.
• A catalytic hydrogen wave of the osmium-cysteine system

  M Kawasaki, T Kakizaki, WH Hu, K Toyota, K Hasebe

  ELECTROANALYSIS 10 (4) 276 - 278 1040-0397 1998/04 [Refereed][Not invited]
   

  In the presence of cysteine, osmium(VIII) in hydrochloric acid exhibits a will-defined maximum wave at -0.85 V (vs. SCE). Effects of the osmium's valence states and the coexisting anions on the reduction wave have been studied polarographically in acidic solution. The high oxidation states (e.g., osmium(VIII) and (VI)) in comparison with low oxidation states have an influence on the height of the hydrogen wave.
• Origin of the upprement Maastrichtian Penalver Formation in the northwestern Cuba

  Takayama Hideo, Tada Ryuji, Matsui Takafumi, Iturralde-Vinent M.A., Tajika Eiichi, Oji Tatsuo, Kiyokawa Shoichi, Toyoda Kazuhiro, Okada Hisataka

  Annual Meeting of the Geological Society of Japan 一般社団法人 日本地質学会 1998 152 - 152 1998
• Preliminary results of the first scientific drilling on Lake Baikal, Buguldeika site, southeastern Siberia

  S. Colman, M. Grachev, P. Hearn, S. Horie, T. Kawai, N. Logachov, V. Antipin, V. Fialkov, A. Gorigljad, B. Tomilov, B. Khakhaev, S. Kochikov, V. Lykov, L. Pevzner, A. Bucharov, N. Logachev, V. Mats, A. Bardardinov, E. Karabanov, E. Baranova, O. Khlystov, V. Khrachenko, M. Shimaraeva, E. Kornakova, S. Efremova, E. Stolbova, A. Gvozdkov, V. Kravchinski, T. Fileva, S. Kashik, T. Khramtsova, I. Kalashnikova, T. Rasskazova, V. Tatarnikova, R. Yuretich, V. Mazilov, K. Takemura, V. Bobrov, T. Gunicheva, H. Haraguchi, S. Ito, T. Kocho, M. Kuzmin, M. Markova, V. Pampura, O. Proidakova, H. Sawatari, A. Takeuchi, K. Toyoda, S. Vorobieva, A. Ikeda, A. Marui, T. Nakamura, K. Ogura, T. Ohta, J. King, J. Peck, H. Sakai, T. Yokoyama, A. Hayashida, E. Bezrukova, S. Fowell, N. Fuji, P. Letunova, V. Misharina, N. Miyoshi, G. Chernyaeva, I. Ignatova, E. Likhoshvai, E. Stoermer, L. Granina, O. Levina, P. Dolgikh, R. Ishiwatari, F. Lazo, N. Lutskaia, W. Orem, E. Wada, D. Williams, K. Yamada, S. Yamada, E. Callander, L. Golobokoval, L. Granina, P. Shanks, R. Dorofeeva, A. Duchkov

  Quaternary International 37 3 - 17 1040-6182 1997 [Refereed][Not invited]
   

  The Baikal Drilling Project (BDP) is a multinational effort to investigate the paleoclimatic history and tectonic evolution of the Baikal sedimentary basin during the Late Neogene. In March 1993 the Baikal drilling system was successfuly deployed from a barge frozen into position over a topographic high, termed the Buguldeika saddle, in the southern basin of Lake Baikal. The BDP-93 scientific team, made up of Russian, American and Japanese scientists, successfully recovered the first long (>100 m) hydraulic piston cores from two holes in 354 m of water. High quality cores of 98 m (Hole 1) and 102 m (Hole 2), representing sedimentation over the last 500,000 years, were collected in 78 mm diameter plastic liners with an average recovery of 72% and 90%, respectively. Magnetic susceptibility logging reveals an excellent hole-to-hole correlation. In this report the scientific team describes the preliminary analytical results from BDP-93 hole 1 cores. Radiocarbon dating by accelerator mass spectrometry provides an accurate chronology for the upper portion of Hole 1. Detailed lithologic characteristics, rock magnetic properties and inorganic element distributions show a significant change to the depositional environment occuring at 50 m subbottom depth, approximately 250,000 BP. This change may be due to uplift and rotation of the horst block in the Buguldeika saddle. The sedimentary section above 50 m is pelitic with varve-like laminae, whereas the section below 50 m contains a high proportion of sand and gravel horizons often organized into turbidite sequences. Accordingly, high resolution seismic records reveal a change in sonic velocity at this depth. It is inferred that sedimentation prior to 250 ka BP was from the west via the Buguldeika river system. After 250 ka BP the Buguldeika saddle reflects an increase in hemipelagic sediments admixed with fine-grained material from the Selenga River drainage basin, east of Lake Baikal. Variations in the spore-pollen assemblage, diatoms, biogenic silica content, rock magnetic properties, clay mineralogy and organic carbon in the upper 50 m of BDP-93-1 reveal a detailed record of climate change over approximately the last 250,000 years. These variables alternate in a pattern characteristic of glacial/interglacial climatic fluctuations. The present age model suggests that the climate signal recorded in Lake Baikal sediments is similar to Late Quaternary signals recorded in Chinese loess sections and in marine sediments. Copyright © 1996 INQUA/ Elsevier Science Ltd.
• LEAD ISOTOPIC COMPOSITIONS IN FAULT GOUGES AND THEIR PARENT ROCKS - IMPLICATIONS FOR ANCIENT FAULT ACTIVITIES

  A MASUDA, K SUGINO, K TOYODA

  APPLIED GEOCHEMISTRY 10 (4) 437 - 446 0883-2927 1995/07 [Refereed][Not invited]
   

  This is the first study on Pb stable isotopes in fault gouges and their parent rocks. We analyzed the composition of Pb isotopes and contents of U and Pb in 10 pairs of fault gouges and their parent rocks collected along several active faults in central Japan. Thorium-232-Pb-208 ages of two fault systems were determined as pre-Tertiary, which are consistent with the data from K-Ar ages and geological considerations. Naturally, the U-235-Pb-207 system is of little use for dating because the magnitude of difference in Pb-207/Pb-204 between gouges and parent rocks is too small. It is found that the Pb-206/Pb-204 can indicate the contribution of Pb-206 resulting from excess supplies of Ra-226 and Rn-222 along the fault. The excess Pb-206 accumulation rate corresponds to the average Rn-222 concentration in soil gas or groundwater through geological time since the gouge formation. A comparison of Quaternary fault activity and estimated Tertiary activity reveals the characteristics of each fault system.
• KINETICS OF REMELTING REACTION IN CA2SIO4 SOLID-SOLUTIONS

  K FUKUDA, MAKI, I, S ITO, K TOYODA

  JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 103 (5) 444 - 448 1882-0743 1995/05 [Refereed][Not invited]
   

  The cell dimensions for a series of beta-Ca2SiO4 solid solutions were determined as a function of concentration of foreign oxides (Na2O, Al2O3 and Fe2O3). The angle beta varied most sensitively with the Na/(Na+Ca) ratio (=x) according to beta (degrees) = 94.55-8.86 x (0 less than or equal to x less than or equal to 0.03). The decrease in x that accompanies the remelting reaction was therefore defectable by the increase in beta. When the crystals were cooled at a constant rate r (degrees C/s) over the temperature range in which the remelting reaction occurred, the fraction remelted was expressed by 1-exp(-1.33 r(-0.25)).
• DUPAL ANOMALY OF BRAZILIAN CARBONATITES - GEOCHEMICAL CORRELATIONS WITH HOTSPOTS IN THE SOUTH-ATLANTIC AND IMPLICATIONS FOR THE MANTLE SOURCE

  K TOYODA, H HORIUCHI, M TOKONAMI

  EARTH AND PLANETARY SCIENCE LETTERS 126 (4) 315 - 331 0012-821X 1994/09 [Refereed][Not invited]
   

  Geochemical and Sr, Pb, O and C isotopic data are reported for carbonatite samples from five locations in southeast Brazil. Elemental abundances and delta(13)C(PDB) data (between -5.8 and -7.2 parts per thousand) prove that all the samples are derived from the mantle. Dupal isotopic characteristics in the all carbonatite samples from five locations in southeast Brazil are found in this study, characteristics that have not previously been recognized in carbonatites. Brazilian carbonatites possess average Delta 8/4 values of between 101 and 145, average Delta 7/4 values of between 5.2 and 10.3, and initial Sr isotopic compositions of between 0.7046 and 0.7062. The Brazilian carbonatites comprise two groups: The northern group is coincident with the passage of the Trindade non-Dupal hotspot at ca. 80 Ma, while the southern group mainly corresponds to the passage of the Tristan de Cunha Dupal hotspot at ca. 130 Ma. Although we expected a geochemical correlation between the Brazilian carbonatites and the South Atlantic hotspots, the enriched isotopic signature (EM1) of all the carbonatite samples is similar to that of alkali basalts on Tristan de Cunha. The combined O-Sr isotopic diagram indicates that the southern group carbonatites have negligible or only slight crustal contamination. The northern group samples show significantly higher delta(18)O(SMOW) values of 9-14 parts per thousand, more radiogenic Pb isotopic ratios, and a Sr-87/Sr-86 value of 0.705. Even if these signatures are derived from the contamination of a lower crustal component with mantle sources, it is clear that the parental magma also has inherent EM1 isotopic characteristics. The interpretation of the origin of EM1 in the Brazilian carbonatites (subcontinental lithospheric mantle vs. asthenosphere) is dependent on the model of Parana volcanism at ca. 130 Ma, which remains controversial. One possibility is that both the northern and southern carbonatites came from enriched SCLM under a part of Gondwanaland. In this case, a hotspot would provide the thermal energy to melt the lithospheric source region for both the Parana flood basalts and the alkali carbonatitic volcanism. Another possibility is that the source of the northern carbonatites is also the Tristan plume carbonate-rich material which had once been trapped under the crust and reactivated by the Trindade hotspot, on the assumption that Parana volcanism at ca. 130 Ma was mainly triggered by the huge Tristan plume activity. If anything, we favour the latter and believe an asthenospheric mantle plume origin for bath the ultimate carbonate source and the Dupal anomaly in the Brazilian carbonatites.
• DUPAL ANOMALY OF BRAZILIAN CARBONATITES - GEOCHEMICAL CORRELATIONS WITH HOTSPOTS IN THE SOUTH-ATLANTIC AND IMPLICATIONS FOR THE MANTLE SOURCE

  K TOYODA, H HORIUCHI, M TOKONAMI

  EARTH AND PLANETARY SCIENCE LETTERS 126 (4) 315 - 331 0012-821X 1994/09 [Refereed][Not invited]
   

  Geochemical and Sr, Pb, O and C isotopic data are reported for carbonatite samples from five locations in southeast Brazil. Elemental abundances and delta(13)C(PDB) data (between -5.8 and -7.2 parts per thousand) prove that all the samples are derived from the mantle. Dupal isotopic characteristics in the all carbonatite samples from five locations in southeast Brazil are found in this study, characteristics that have not previously been recognized in carbonatites. Brazilian carbonatites possess average Delta 8/4 values of between 101 and 145, average Delta 7/4 values of between 5.2 and 10.3, and initial Sr isotopic compositions of between 0.7046 and 0.7062. The Brazilian carbonatites comprise two groups: The northern group is coincident with the passage of the Trindade non-Dupal hotspot at ca. 80 Ma, while the southern group mainly corresponds to the passage of the Tristan de Cunha Dupal hotspot at ca. 130 Ma. Although we expected a geochemical correlation between the Brazilian carbonatites and the South Atlantic hotspots, the enriched isotopic signature (EM1) of all the carbonatite samples is similar to that of alkali basalts on Tristan de Cunha. The combined O-Sr isotopic diagram indicates that the southern group carbonatites have negligible or only slight crustal contamination. The northern group samples show significantly higher delta(18)O(SMOW) values of 9-14 parts per thousand, more radiogenic Pb isotopic ratios, and a Sr-87/Sr-86 value of 0.705. Even if these signatures are derived from the contamination of a lower crustal component with mantle sources, it is clear that the parental magma also has inherent EM1 isotopic characteristics. The interpretation of the origin of EM1 in the Brazilian carbonatites (subcontinental lithospheric mantle vs. asthenosphere) is dependent on the model of Parana volcanism at ca. 130 Ma, which remains controversial. One possibility is that both the northern and southern carbonatites came from enriched SCLM under a part of Gondwanaland. In this case, a hotspot would provide the thermal energy to melt the lithospheric source region for both the Parana flood basalts and the alkali carbonatitic volcanism. Another possibility is that the source of the northern carbonatites is also the Tristan plume carbonate-rich material which had once been trapped under the crust and reactivated by the Trindade hotspot, on the assumption that Parana volcanism at ca. 130 Ma was mainly triggered by the huge Tristan plume activity. If anything, we favour the latter and believe an asthenospheric mantle plume origin for bath the ultimate carbonate source and the Dupal anomaly in the Brazilian carbonatites.
• GEOCHEMICAL HISTORY OF ANCIENT LAKE BIWA IN JAPAN - CHEMICAL INDICATORS OF SEDIMENTARY PALEO-ENVIRONMENTS IN A DRILLED CORE

  K TOYODA

  PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY 101 (1-2) 169 - 184 0031-0182 1993/03 [Refereed][Not invited]
   

  A comparison is made between the geochemical compositions of drilled sediment core samples from Lake Biwa and samples of surface sediments and from land around Lake Biwa to estimate paleo-water depth, spatial variability and past changes in sediment sources. The Al-Fe-Mn x 10 diagram indicates that Lake Biwa has been an oligotrophic lake since its formation. An investigation of the origin of a positive correlation between water-depth and the Mn/Al ratio in surface sediments is made and the historical change of paleo-water depth in Lake Biwa proposed by Koyama et al. (1985) verified. Demonstrated are the usefulness of both Ti/Al ratio and REE pattern to detect changes in sediment sources and geochemical discontinuities in four layers which should indicate unconformities are found. My data could be supporting evidence for the chronological assignment of Takemura (1990). An explanation is given for the historical changes of source materials in drilled core samples associated with tectonic changes on the basis of the historical basin development postulated by Yokoyama (1984).
• Comprehensive investigation of lake Baikal core 323-PC1

  K.Toyoda, K.Takemura, R.Ishiwatari

  Russian Geology and Geophysics. 34 (11) 101 - 110 1993 [Refereed][Not invited]
   

  K.Toyoda, K.Takemura and R.Ishiwatari: "Comprehensive investigation of lake Baikal core 323-PC1" Russian Geology and Geophysics. 34. 101-110 (1993). Тойеда К., Такемура К., Ишиватари Р.Комплексное исследование колонки 323-PC1 донных осадков оз. Байкал. // Геология и геофизика; 1993; 34(10-11):124-135.
• Geochemical history of ancient Lake Biwa in Japan-chemical indicators of sedimentary paleo-environments in a drilled core

  Kazuhiro Toyoda

  Palaeogeography, Palaeoclimatology, Palaeoecology 101 (1-2) 169 - 184 0031-0182 1993 [Refereed][Not invited]
   

  A comparison is made between the geochemical compositions of drilled sediment core samples from Lake Biwa and samples of surface sediments and from land around Lake Biwa to estimate paleo-water depth, spatial variability and past changes in sediment sources. The AlFeMn × 10 diagram indicates that Lake Biwa has been an oligotrophic lake since its formation. An investigation of the origin of a positive correlation between water-depth and the Mn/Al ratio in surface sediments is made and the historical change of paleo-water depth in Lake Biwa proposed by Koyama et al. (1985) verfied. Demonstrated are the usefulness of both Ti/Al ratio and REE pattern to detect changes in sediment sources and geochemical discontinuities in four layers which should indicate unconformities are found. My data could be supporting evidence for the chronological assignment of Takemura (1990). An explanation is given for the historical changes of source materials in drilled core samples associated with tectonic changes on the basis of the historical basin development postulated by Yokoyama (1984). © 1993.
• Kinetics of the α‐to‐α′H Polymorphic Phase Transition of Ca2SiO4 Solid Solutions

  Koichiro Fukuda, Iwao Maki, Kazuhiro Toyoda, Suketoshi Ito

  Journal of the American Ceramic Society 76 (7) 1821 - 1824 1551-2916 1993 [Refereed][Not invited]
   

  The α‐to‐α′H transition of Ca2SiO4 solid solutions (C2S(ss)) is a nucleation and growth process. This process was shown on time–temperature–transformation (TTT) diagrams for C2S(ss) with different concentrations of foreign oxides (Na2O, Al2O3, and Fe2O3). The kinetic cutoff temperature and the activation energy for growth of the α′H phase increase steadily with increasing concentration of impurities. The activation energy for nucleation also increases above 950°C. The α′H phase, which exists in equilibrium with the α phase at 1280°C, is formed at a maximum rate at around 1100°C regardless of the chemical composition. The TTT diagrams enable us to predict, as a function of cooling rate, the phase constitution of C2S(ss) at ambient temperature. Copyright © 1993, Wiley Blackwell. All rights reserved
• CHEMICAL LEACHING OF PELAGIC SEDIMENTS - IDENTIFICATION OF THE CARRIER OF CE ANOMALY

  K TOYODA, A MASUDA

  GEOCHEMICAL JOURNAL 25 (2) 95 - 119 0016-7002 1991 [Refereed][Not invited]
   

  Several chemical leaching experiments were carried out to characterize the REE distribution in four pelagic sediments which have negative Ce anomaly collected in Central Pacific. Extraction experiments indicate that the carrier of the negative Ce anomaly is phosphate phase. This result supports our hypothesis that a negative Ce anomaly is mainly due to fish bone debris in the Pacific equatorial pelagic sediments, in case of pelagic sediments far from the areas of hydrothermal activity. Furthermore, a positive Ce anomaly in pelagic sediments was confirmed by leaching experiment to be due to hydrogenous components (Mn-Fe oxides). The terrigenous component (silicate phase) has a low REE content and a flat shale-normalized REE pattern.
• CHEMICAL LEACHING OF PELAGIC SEDIMENTS - IDENTIFICATION OF THE CARRIER OF CE ANOMALY

  K TOYODA, A MASUDA

  GEOCHEMICAL JOURNAL 25 (2) 95 - 119 0016-7002 1991 [Refereed][Not invited]
   

  Several chemical leaching experiments were carried out to characterize the REE distribution in four pelagic sediments which have negative Ce anomaly collected in Central Pacific. Extraction experiments indicate that the carrier of the negative Ce anomaly is phosphate phase. This result supports our hypothesis that a negative Ce anomaly is mainly due to fish bone debris in the Pacific equatorial pelagic sediments, in case of pelagic sediments far from the areas of hydrothermal activity. Furthermore, a positive Ce anomaly in pelagic sediments was confirmed by leaching experiment to be due to hydrogenous components (Mn-Fe oxides). The terrigenous component (silicate phase) has a low REE content and a flat shale-normalized REE pattern.
• SEDIMENTARY ENVIRONMENTS AND CHEMICAL-COMPOSITION OF PACIFIC PELAGIC SEDIMENTS

  K TOYODA, A MASUDA

  CHEMICAL GEOLOGY 88 (1-2) 127 - 141 0009-2541 1990/10 [Refereed][Not invited]
  
• DIFFUSION OF RARE-EARTH ELEMENTS IN FISH TEETH FROM DEEP-SEA SEDIMENTS

  K TOYODA, M TOKONAMI

  NATURE 345 (6276) 607 - 609 0028-0836 1990/06 [Refereed][Not invited]
  
• RARE-EARTH ELEMENTS OF PACIFIC PELAGIC SEDIMENTS

  K TOYODA, Y NAKAMURA, A MASUDA

  GEOCHIMICA ET COSMOCHIMICA ACTA 54 (4) 1093 - 1103 0016-7037 1990/04 [Refereed][Not invited]
  
• GEOCHEMICAL CHARACTERIZATION OF GEOLOGICAL STANDARD ROCK SAMPLES FROM RARE-EARTH ELEMENT DISTRIBUTION PATTERNS MEASURED BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

  K TOYODA, H HARAGUCHI

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 60 (3) 933 - 939 0009-2673 1987/03 [Refereed][Not invited]
  
• GEOCHEMICAL CHARACTERIZATION OF GEOLOGICAL STANDARD ROCK SAMPLES FROM RARE-EARTH ELEMENT DISTRIBUTION PATTERNS MEASURED BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

  K TOYODA, H HARAGUCHI

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 60 (3) 933 - 939 0009-2673 1987/03 [Refereed][Not invited]
  
• RARE-EARTH ELEMENTS IN 6 NEW GSJ STANDARD ROCK SAMPLES AS DETERMINED BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

  K TOYODA, H HARAGUCHI

  GEOSTANDARDS NEWSLETTER 10 (2) 173 - 175 0150-5505 1986/10 [Refereed][Not invited]
  
• RARE-EARTH ELEMENTS IN 6 NEW GSJ STANDARD ROCK SAMPLES AS DETERMINED BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

  K TOYODA, H HARAGUCHI

  GEOSTANDARDS NEWSLETTER 10 (2) 173 - 175 0150-5505 1986/10 [Refereed][Not invited]
  
• HE-3-HE-4 RATIOS OF MARINE FERROMANGANESE NODULES

  Y SANO, K TOYODA, H WAKITA

  NATURE 317 (6037) 518 - 520 0028-0836 1985 [Refereed][Not invited]
  
• DETERMINATION OF RARE-EARTH ELEMENTS IN GEOLOGICAL STANDARD ROCK SAMPLES BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

  K TOYODA, H HARAGUCHI

  CHEMISTRY LETTERS (7) 981 - 984 0366-7022 1985 [Refereed][Not invited]
  
• HE-3-HE-4 RATIOS OF MARINE FERROMANGANESE NODULES

  Y SANO, K TOYODA, H WAKITA

  NATURE 317 (6037) 518 - 520 0028-0836 1985 [Refereed][Not invited]
  
• DETERMINATION OF RARE-EARTH ELEMENTS IN GEOLOGICAL STANDARD ROCK SAMPLES BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

  K TOYODA, H HARAGUCHI

  CHEMISTRY LETTERS (7) 981 - 984 0366-7022 1985 [Refereed][Not invited]
  
• 深海底堆積物とマンガンノジュールの地球化学的研究」

  豊田 和弘

  東京大学大学院理学系研究科 [Refereed][Not invited]
  

MISC

• Ecological Risk Assessments of Heavy Metals in the Surface Sediment between the Artificial Granite Rocky Shore of Tanjung Harapan, Selangor.

  Chee Kong Yap, Wan Hee Cheng, Kazuhiro Toyoda  Sediment Watch: Monitoring, Ecological Risk Assessment and Environmental Management  Chapter 8-  2018  [Not refereed][Not invited]
  
• 放射化分析専門研究会報告 : 参加者の視点から(平成21年度京都大学原子炉実験所専門研究会)

  豊田 和弘  放射化分析  0-  (26)  59  -61  2010/07  [Not refereed][Not invited]
  
• 過去4万年における琵琶湖コア中の重鉱物の運搬堆積に関する地球化学的記録と気候変動や古地震との関連(平成17年度京大原子炉実験所専門研究会要旨)

  篠塚 良嗣, 任 忠完, 豊田 和弘  放射化分析  0-  (20)  37  -38  2006/07  [Not refereed][Not invited]
  
• 琵琶湖と水月湖の湖底コアの放射化分析から検出した複数の鬱陵島テフラ(平成16年度京大原子炉実験所専門研究会講演要旨,研究紹介)

  篠塚 良嗣, 豊田 和弘, 宮田 一成, 任 忠完, 北川 浩之, 安田 黄憲  放射化分析  0-  (18)  40  -40  2005/04  [Not refereed][Not invited]
  
• 中国の風成塵堆積物の放射化分析(平成16年度京大原子炉実験所専門研究会講演要旨,研究紹介)

  村田 拓也, 前野 太平, 篠塚 良嗣, 豊田 和弘, 福澤 仁之, 尹 懐寧, 安田 喜憲  放射化分析  0-  (18)  41  -41  2005/04  [Not refereed][Not invited]
  
• K/T boundary deposits in the Paleo-western Caribbean basin

  Ryuji Tada, Manuel A. Iturralde-Vinent, Takafumi Matsui, Eiichi Tajika, Tatsuo Oji, Kazuhisa Goto, Yoichiro Nakano, Hideo Takayama, Shinji Yamamoto, Shoichi Kiyokawa, Kazuhiro Toyoda, Dora García-Delgado, Consuelo Díaz-Otero, Reinaldo Rojas-Consuegra  AAPG Memoir  (79)  105  -108  2005  

  A thick, calcareous, clastic megabed of late Maastrichtian age has been known for sometime in western and central Cuba. This megabed was formed in association with the bolide impact at Chicxulub, Yucatan, at the K/T boundary, and is composed of a lower gravity-flow unit and an upper homogenite unit. The lower gravity-flow unit is dominantly composed of calcirudite that was formed because of collapses of the Yucatan, Cuban, and Bahamian platform margins and subsequent accumulation in the lower slope to basin margin environment. The gravity flow probably was triggered by a seismic wave induced by the impact, although a ballistic flow may have triggered collapse in the case of proximal sites (Yucatan margin). The upper homogenite unit is composed of massive and normally graded calcarenite to calcilutite that was formed as a result of large tsunamis associated with the impact and deposited in wider areas in the deeper part of Paleo-western Caribbean basin. Slight grain-size oscillations in this unit probably reflect the influence of repeated tsunamis. The large tsunamis were generated either by the movement of water into and out of the crater cavity or by the large-scale slope failure on the eastern margin of the Yucatan platform. In upper slope to shelf environments, gravity-flow deposits and homogenite are absent, and a thin sandstone complex influenced by repeating tsunami waves was deposited.
• 水の分析 (単行本) 第5版<日本分析化学会北海道支部 (編集) 出版社>

  化学同人  2005  [Not refereed][Not invited]
  
• 中国南部のエルハイ湖とインドのサンバール湖で採取された堆積物コア試料の放射化分析 (中性子利用分析(宇宙地球科学))

  豊田 和弘, 篠塚 良嗣, 三浦 雅洋  原研施設利用共同研究成果報告書  39  -44  2003  [Not refereed][Not invited]
  
• 学ぶ環境<（共同執筆）日本分析化学会北海道支部 編 >

  三共出版  2002  [Not refereed][Not invited]
  
• 中国で採取された風成塵堆積物の放射化分析 (中性子利用分析・放射化分析)

  豊田 和弘, 篠塚 良嗣, 渡辺 厚志  原研施設利用共同研究成果報告書  (41)  104  -106  2001  [Not refereed][Not invited]
  
• O-181 Distribution and formation mechanism of the K/T boundary mega-tsunami deposits of the Penalver. Fm, northwestern Cuba

  Iturralde-Vinent Manuel A, Dora G, Rojas D  Annual Meeting of the Geological Society of Japan  107-  (0)  101  -101  2000/09/25  [Not refereed][Not invited]
  
• 2. 堆積物コア試料の機器中性子放射化分析(講座「宇宙・地球科学における放射化分析」)

  豊田 和弘  放射化分析  0-  (9)  6  -14  1999/10  [Not refereed][Not invited]
  
• 堆積物中の砒素の定量について : 中性子放射化分析と他の分析方法との比較(研究紹介)

  豊田 和弘, 篠塚 良嗣  放射化分析  0-  (9)  32  -35  1999/10  [Not refereed][Not invited]
  
• バイカル湖300mコア中のイリジウムの放射化分析 (中性子利用分析・放射化分析)

  豊田 和弘, 嶋田 光雄, 篠塚 良嗣  原研施設利用共同研究成果報告書  0-  (39)  149  -155  1999  [Not refereed][Not invited]
  
• 堆積物試料中の微量元素の放射化分析(3) (放射化分析A(宇宙地球科学))

  豊田 和弘, 嶋田 光雄, 篠塚 良嗣  立教大学原子炉利用共同研究成果報告書  (26)  28  -31  1999  [Not refereed][Not invited]
  
• 「堆積物コア試料の機器中性子放射化分析」

  「「放射化分析」」  (9号)  6  -13  1999  [Not refereed][Not invited]
  
• 「「放射化分析」」9号

  1999  [Not refereed][Not invited]
  
• 311 Large-scale "Tsunami" deposit at K/T boundary in Cuba

  TADA Ryuji, MATSUI Takafumi, TAJIKA Eiichi, OJI Tatsuo, TAKAYAMA Hideo, KIYOKAWA Shoichi, TOYODA Kazuhiro, OKADA Hisatake  Annual Meeting of the Geological Society of Japan  104-  (0)  256  -256  1997/09/30  [Not refereed][Not invited]
  
• Development in Depositional Dating of Sediments Using Optically Stimulated Luminescence Phenomena.

  TOYODA Kazuhiro  ぶんせき  269-  (0)  401  -403  1997/05/05  [Not refereed][Not invited]
  
• Iridium anomaly is not detected at around the P/T boundary of bedded chert sequence in Southwest Japan

  Kakuwa Yoshitaka, Toyoda Kazuhiro  Journal of the Geological Society of Japan  102-  (2)  139  -142  1996/02/15  [Not refereed][Not invited]
  
• Iridium anomaly is not detected at around the P/T boundary of bedded chert sequence in Southwest Japan

  Kakuwa Yoshitaka, Toyoda Kazuhiro  Journal of the Geological Society of Japan  102-  (2)  139  -142  1996  [Not refereed][Not invited]
  
• 23 ブラジル・バイヤ州イタペチンガ東南方における含霞石方ソウダ石閃長岩の風化作用における構成鉱物と化学組成の変化(第二報)

  湊 秀雄, 床次 正安, 豊田 和弘, Nakashima J  粘土科学討論会講演要旨集  0-  (36)  64  -65  1992/08/31  [Not refereed][Not invited]
  
• 23.ブラジル・バイヤ州イタペチンガ東南における含霞石第ソーダ石閃長岩の風化作用における構成鉱物と科学組成の変化(第二報)(第36回粘土科学討論会発表論文抄録)

  湊 秀雄, 床次 正安, 豊田 和弘, Nakashima J  粘土科学  32-  (4)  1992/03/25  [Not refereed][Not invited]
  
• 岩石・鉱物の分析--マイクロビ-ムアナリシスや状態分析を中心に

  豊田 和弘  ぶんせき  1989-  (8)  p630  -637  1989/08  [Not refereed][Not invited]
  
• 機器光量子放射化分析法による標準岩石試料およびカ-ボナタイト風化土壌試料の分析

  豊田 和弘, 床次 正安  核理研研究報告  22-  (1)  p117  -122  1989/06  [Not refereed][Not invited]
  

Books etc

• 地球と宇宙の化学辞典

  豊田 和弘 (Contributorテフラによる火山活動履歴)
  朝倉書店 2012/09 (ISBN: 9784254160574)
• オゾン層破壊の科学

  北海道大学出版会 2007
• 放射化分析ハンドブック—確度の高い多元素同時微量分析への実践

  日本アイソトープ協会 2004

Presentations

• Airborne radioactive contamination in urban areas from the nuclear accident in Fukushima  [Invited]

  TOYODA Kazuhiro

  the Second International Conference on Sustainable Built Environment (ICSBE) 2012 Universitas Islam Indonesia, Yogyakarta, Indonesia  2012/07
• Environmental purification by manganese-oxidizing bacteria.  [Invited]

  TOYODA Kazuhiro, TEBO Bradley

  Annual meeting of Japan Society for Bioscience, Biotechnology, and Agrochemistry 2011 Kyoto  2011/03

Teaching Experience

Methods of International CommunicationMethods of International Communication GSES, Hokkaido Univ.
Exercise on chemistry of the environmentExercise on chemistry of the environment GSES, Hokkaido Univ.
Advanced Course of international communication methodsAdvanced Course of international communication methods GSES, Hokkaido Univ.

Association Memberships

• 放射化分析研究会   日本地球化学会   第四紀学会   GEOCHEMICAL SOCIETY   Japan association of Activation Analysis   Japan association of Quaternary Research   The Geochemical Society of Japan   The Geochemical Society   地球環境史学会   

Research Projects

• A new reconstructing method of Tsunami attack during the last several thousand years by Sr ratio measurements in a varve of a brackish lake

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2012 -2012 

  Author : TOYODA Kazuhiro, YONENOBU Hitoshi

   

  This research is to pursue the possibility in reconstructing the history of tsunami attack during the last several thousand years based on Sr isotopic data extracted from an annually laminated sediment core taken in center part of Lake Ogawara in Aomori Prefecture. The Sr isotope could be served as proxy of paleosalinity of environmental waters. As for the Lake Ogawara, the method is problematic because the variations of Sr isotope in the sediment little reflect the past paleosalinity fluctuation inthe bottom water. This is due to the low Sr concentration in the river flowing to the lake.
• High-resolution environmental reconstruction for the Pacific civilizations using annually laminated lake sediments

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2009 -2012 

  Author : YONENOBU Hitoshi, TOYODA Kazuhiro, GOTANDA Katsuya, YASUDA Yoshinori, OKUNO Mitsuru, NASU Hiroo, YAMADA Kazuyoshi, MORITA Yoshimune, HAYSHIDA Akira, HARAGUCHI Tsuyoshi, YOKOYAMA Yusuke, OHYAMA Motonari, SAITO-KATO Megumi, ODA Hirotaka

   

  The purpose of the study is to clarify the relationship between environmental changes and the ancient civilizations in the Pacific regions. Sediment cores were recovered from the lakes in Guatemala, Southern Peru, Cambodia and Ryukyu Islands. These were analyzed to reconstruct the past environmental changes, i.e., climate, natural disasters, vegetation and anthropogenic activities over the regions. Radiocarbon (C-14) determinations obtained from annually laminated sediments in Lake Suigetsu were incorporated in the C-14 calibration curve, Intcal 13, which contributes to the high-precision dating in archaeology and geosciences. The environmental reconstructions were compared to the societal changes in the civilizations.
• High resolution multiple time scale analysis of Lake Biwa sediments-Research on climate and tectonics during past 150,000 years

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))

  Date (from‐to) : 2007 -2009 

  Author : Keiji TAKEMURA, 北川 浩之, 奥田 昌明, 公文 富士夫, Akira HAYASHIDA, Naoto ISHIKAWA, Tsuyoshi HARAGUCHI, Takehiko SATOMURA, Masahiro CHIGIRA, Hiroki KAMATA, Takahiro TAGAMI, Tomoyuki SHIBATA, Kazuhiro TOYODA, Masaaki OKUDA, Fujio KUMON, Hiroyuki KITAGAWA, Fujio MASUDA, Masayuki TORII

   

  Six piston core samples and two drilling samples from Lake Biwa were obtained in 2007 and 2008. Those core sediments have a potential which is clarified the precise environmental change during past 300,000 years on the basis of tephrochronologial data and 14C dating. Paleomagnetic information and paleotemperature information also were obtained. Shallow seismic survey of total 300km revealed the sediment stratigraphy in whole North Lake region of Lake Biwa.
• Geological studies on extrusion of metamorphic nappe and changesin Indian monsoon

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 2006 -2008 

  Author : Harutaka SAKAI, 藤井 理恵, 豊田 和弘, Yutaka TAKIGAMI, Yoshihiro TANIMURA, Yoshihiro KUWAHARA, Hideo SAKAI, Toshiro YAMANAKA, Rie FUJII, Kazuhiro TOYODA, Arata MOMOHARA

   

  ヒマラヤ山脈上昇史の鍵を握る変成岩ナップは, 約1440万年前に地表に露出・急冷し, 年間3-4cm の速度で南南西に前進し, 約1100 万年前に運動を停止した.冷却は先端から北方へ向け年間約1-1.5cm の速度で進行した.古カトマンズ湖の泥質湖成堆積物の堆積開始は約100 万年前まで遡り, 寒冷期には化学的風化が進まず, 堆積速度が遅く, 温暖期には化学的風化が促進され, 堆積速度が速かったことが判明した.
• Sensitive detection of alkaline cryptotephra layers in deep-sea cores from the Sea of Japan using high-resolution INAA analysis

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 2005 -2008 

  Author : Kazuhiro TOYODA, Ken IKEHARA, Hiroshi MACHIDA, Jonghwa CHUN

   

  地球温暖化の将来予測に有用な古環境復元の精密年代軸として注目されるクリプトテフラ(肉眼では検出不可な希薄な火山灰層)の高感度な検出法として、放射化分析法による地層の高密度な微量元素分析が有効であると実証した。十数本の日本海海底コア中の最大過去十五万年間の堆積物を走査し、5つの新しい指標となるテフラを検出し年代推定を行い、欝陵島(韓国)と白頭山(中朝国境)から飛来する降下火山灰の履歴を構築にした。
• A study for the long-term and short-term disturbances of the envirnment by the extraterrestrial impact at the Cretaceous/Tertiary boundary

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 2005 -2007 

  Author : Takafumi MATSUI, 多田 隆治, 田近 英一, 後藤 和久, 長谷川 卓, 豊田 和弘

   

  We conducted field survey near the impact site at the Cretaceous/Tertiary (K/T) boundary at Fomento area, Cuba and Lajilla area, Mexico in order to investigate the magnitude and duration of the impact-induced tsunami. As a result, we found that the evidence of the crater-ward first tsunami wave is observed at Fomento area as well as the impactite in and out of the Chicxulub crater. These observations support the hypothesis that the tsunami was generated by the ocean water invasion into the crater and overflow from the crater.We also studied K/T boundary deposits and their adjacent deposits ...
• 桿菌胞子の酸化酵素を活用してヒ素汚染地下水を浄化できる可能性についての基礎研究

  文部科学省：科学研究費補助金(萌芽研究)

  Date (from‐to) : 2003 -2004 

  Author : 豊田 和弘

   

  地下水のヒ素汚染は南アジアなどで深刻な問題となっている。その地域の地下水は難分解有機物(フミン物質)に富んでいるためにヒ素の除去は容易ではない。本研究の目的はマンガン酸化バクテリアの1つである桿菌SG-1休眠胞子の環境水中のヒ素の浄化処理能力について確定することである。平成15年度ではマンガンの溶存2価イオンから不溶な4価の酸化物への触媒反応速度とそれに伴う三価と五価のヒ素イオンの変化について実験したが、平成16年度では、有機物や鉄イオンとの共存状態の系について実験を行った。有機物の分解速度を測定するために、フミン物質の分解生成物である一酸化炭素などのガス発生量の定量に必要なガスクロマトグラフィーの検出器を本研究費で購入した。しかし、既に本研究科の専攻に設置済みのガスクロマトグラフィー本体は放射性物質を含むために設置場所の放射線管理区域の移転許可が必要である。ところが、その移転許可申請後3年たった今でもその承認が降りないために購入備品を使用することが出来なかった。そこで、COE経費で捕足部品購入することで使用可能になった有機酸測定用のHPLCシステムを用いて、別のフミン物質分解生成物である低分子有機酸の測定を行う事にした。難分解有機物の標準試料としては泥炭地土壌を原料とした市販のフミン物質をさらに生成してもちいた。無機生成したマンガン酸化物による酸化でフミン物質が分解して直接...
• Testing of the Snowball Earth hypothesis in terms of the cap carbonates, Namibia

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 2001 -2003 

  Author : Shin-ichi KAWAKAMI, 豊田 和弘, 大野 照文, 高野 雅夫, 能田 成, 道林 克禎, 可児 智美, 酒井 英男

   

  The purpose of this study is to test the Snowball Earth hypothesis, which suggests that the entire Earth surface was covered with icesheet in several times during Neoproterozoic era. For this purpose, we visited Namibia in winter seasons from 2001 to 2003 and investigated ouccrops of diamictites, cap carbonates, and iron formations associated with diamictites. The rock specimens sampled from Ghaab diamictites near Fransfountain was used for rheological analysis which revealed that the diamicites was compressed by the overburden pressures after deposition. The cap carbonates were used for ge...
• Uplift of Himalayas and its induced Global Environmental Changes

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))

  Date (from‐to) : 1999 -2001 

  Author : Harutaka SAKAI, 山縣 毅, 折橋 裕二, 瀧上 豊, 桑原 義博, 西 弘嗣, 豊田 和弘, 大野 正夫, 酒井 英男, 山中 寿朗

   

  We carried out geological field investigation and core drilling for academic purpose in the southern part of the Kathmandu Basin, in order to clarify the uplift process of the Himalaya and changes in Indian monsoon during the last 3 myr. Regarding on the drilled cores, we undertook the following studies.1. Paleomagnetic study : we measured natural remanent magnetization and stepwise alternating field demagnetization, and detected two excursions corresponding to Mono Lake and Laschamp excursion.2. 14C age determination : we measured AMS C 14 ages of twelve pieces of carbonized fragment, and ...
• A study on the environmental catastrophe at the K/T bundary

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 1999 -2001 

  Author : Takafumi UATSUI, 田近 英一, 大路 樹生, 多田 隆治, 豊田 和弘

   

  In order to understand the mode and magnitude of K/T boundary impact and its consequences, field surveys were conducted in Cuba where the proximal deep-sea K/T boundary deposits are well exposed. As a result of the field surveys, the following new informations are obtained :1) The deep-sea K/T boundary deposits, as thick as 700 m, are well exposed in three different geological provinces in western Cuba.2) The K/T boundary deposits are composed of two units such as a lower calcirudite unit and an upper calcarenite/calcilutite unit.3) The lower unit is characterized by breccia derived from th...
• 断層の活動履歴を断層物質中の鉛同位体比から復元する新手法の開発

  文部科学省：科学研究費補助金(萌芽的研究)

  Date (from‐to) : 1999 -2000 

  Author : 豊田 和弘

   

  本研究は、東日本の大規模な破砕帯を伴う活断層中の、既によく調査されたトレンチ路頭から試料を採取して、鉛同位体比と化学組成を精度よく測定することで、断層の年代測定及び活動度の新しい評価法としての研究手法を提示することを目的とする。北海道夕張郡のシューパロ湖周辺のダム計画のために掘削されたコア中の断層、福島県双葉郡の路頭から採取した双葉断層と畑山断層、及び群馬県多野郡上野町の神流川の断層の試料、計13地点から採取した。機器中性子放射化分析、ICP発光分析計及びICP質量分析計を併用して、注目しているウラン、トリウム、鉛以外に主成分元素や希土類元素についても定量を行った。主成分・微量元素から同一起源物質と考えられ、ウラン/鉛比とトリウム/鉛比が大きく異なる母岩とガウジの対試料について選定してから、鉛同位体比を測定する。双葉断層N10地点の隣接した部位から採取した3試料は同一起源物質と考えられ、ウラン/鉛比とトリウム/鉛比が大きく異なった。畑山断層Ht101地点の隣接した部位から採取した3試料は起源の異なると考えられ、本研究には適さない。畑山断層M152地点の隣接した部位から採取した4試料のうち、2試料は起源が同じと推測できるし、ウラン/鉛比とトリウム/鉛比が大きく異なるので、この対試料は本研究に都合がよい。畑山断層Ht132の試料はウラン/鉛比とトリウム/鉛比がほとんど変わらないの...
• Climatic change and Asian monsoon variation for the last 300 years recorded in coral skeleton of the South China Sea.

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))

  Date (from‐to) : 1999 -2000 

  Author : Tadamichi OBA, 王 律江, 村山 雅史, 豊田 和弘

   

  We collected one coral drilling core of 2.2 m length in Octorber 1999 from the east coast of Hainan Island, China. The following conclusions were obtained by comparing the in situ temperature-salinity record and the high-resolution oxygen carbon isotopic record (ca 200 samples) of a Hainan Island coral (Porites lutea) for the same one-year period (1999-2000).1. The oxygen isotopic ratios of the coral are clearly affected by both SST and the oxygen isotopic composition of the seawater.2. Minimum oxygen isotopic ratios occurred in December when surface temperatures were the coldest and the ma...
• High-time-resolution reconstruction of sedimentary environment of Lake Biwa during the past ten and several thousand years by inorganic chemical determination.

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))

  Date (from‐to) : 1996 -1999 

  Author : Kazuhiro TOYODA, 田中 俊逸, 長谷部 清

   

  We performed both neutron activation analysis and ICP-AES of sediments taken from the 250 m thick top bed of Lake Biwa at 1.4-2 m intervals, three ca.10 meter long piston cores at 6cm intervals, varved core from the center of Lake Suigetsu at 2 cm intervals during the last glacial/Holocene transition, and the samples from surface sediments and from land around Lake Biwa and Lake Suigetsu for the comparison. The goals in this study are three : (1) Evaluation of As contents as the geochemical proxy of paleo-water-depth ; (2) Quest of geochemical proxy for synchronisation with glacial/-intergl...
• 放射性廃棄物処分地におけるアメリシウムの吸着材としての生物源燐酸塩に関する研究

  文部科学省：科学研究費補助金(萌芽的研究)

  Date (from‐to) : 1996 -1997 

  Author : 豊田 和弘

   

  本研究は、現在問題になっている放射性廃棄物中のアクチノイドの除去材としての生物源リン酸塩の有用性について検討している。ただし、現段階ではアクチノイドと化学的性質が類似している希土類元素を用いている。堆積物中の生物源リン酸塩にはしばしば希土類元素を濃縮しているが、これは堆積物中で有機物が分解後、リン酸塩中のカルシウムが希土類元素に置換されて濃縮されていると考えられる。そこで、本研究では食用の魚の骨片を水酸化カリウム溶液、エチレンジアミン溶液または次亜塩素酸ナトリウム溶液という3つの試薬で処理して有機物を除去した後、吸着剤として使用した。これらの試料片約10〜20mgをそれぞれ0.015〜1.5ppmの希土類元素を含んだ人工海水溶液3mlに3〜7日間室温にて液浸した。各試料を純水中で超音波洗浄後、25℃で乾燥させ、中性子放射化分析を行い、吸着された希土類元素の量を測定した。吸着量はどの吸着剤においても液浸日数に対して増加する傾向にあった。これらの試料はユーロピウム以外の希土類元素についても同様の強い吸着能力を示した。太平化学社製の合成リン酸カルシウム(球形HAP)も生物源リン酸塩と同様に希土類元素に対して強い吸着能力を示し、粒径が小さな試料がより高い吸着能力を示す傾向のあることがわかった。次に、ネオジムについて、球形HAPと球形FAP(合成フロロリン酸カルシウム)の吸着速度と吸着...
• 深海性P/T(二畳紀/三畳紀)境界試料の地球化学的研究

  文部科学省：科学研究費補助金(重点領域研究)

  Date (from‐to) : 1995 -1995 

  Author : 豊田 和弘

   

  今から二億数千万年前の二畳紀と三畳紀の境界(P/T境界)には地球生物史上最大の大量絶滅が起きたとされている。生物絶滅事件の原因として白亜紀/第三紀においてその境界層にイリジウムの濃集が発見されてから天体衝突説が主張されており、梶原ら(1994)は硫黄の同位体比からP/T境界での天体衝突の可能性を示唆した。私は角和善隆氏(東大教養学部)と共同研究で秩父累帯の天神丸セクション(徳島県)などで採取された、P/T境界の黒色炭質泥岩試料中のイリジウムの中性子放射化分析を行った。黒色炭質泥岩が堆積し始めた時代試料ほどの分析(検出限界は数+ppt)では小天体の衝突を示唆するイリジウムの濃縮は全く見られないことがわかった(角和・豊田、1996)が、路頭での厳密なP/T境界層は確定しておらず、数メートルにも渡る黒色炭質泥岩層からさらに百試料ほど採取して丹念に分析をおこなっている。平成7年10月1日付けで東京大学・大学院理学系研究科から北海道大学・大学院地球環境科学研究科へ転出したために東京大学での研究は不可能になったが、それから一カ月経るうちに環境がある程度整い、北海道大学において研究事業を再開することが可能になったが、こちらでの放射線取り扱いの認可が遅れたためにデータの提出が遅れている。これらの試料中の希土類元素については既に山口大の加藤らがおこなっており、現在化学抽出やその他の微量元素や主...
• 断層粘土の形成に伴う微量元素の挙動について

  文部科学省：科学研究費補助金(奨励研究(A))

  Date (from‐to) : 1995 -1995 

  Author : 豊田 和弘

   

  私は中部日本の10箇所の代表的な断層のTh-Pb年代測定および断層帯のラドン濃縮による過剰鉛-206からの過去の活動度推定を試みている。ただしこれらの考察には断層粘土とその母岩との鉛、ウラン、トリウムの含有量が断層粘土形成から現在まで変化していないという前提が必要である。断層粘土の形成に伴う微量元素の挙動については不明な点が多く、国内外でも類似の研究は見あたらない。母岩が花崗岩の場合の断層粘土形成時の化学組成の変化を知るために、六甲花崗岩、跡津川断層北東部の船津花崗岩、阿寺断層中央部の苗木一上松花崗岩、中央構造線の両家花崗岩のような地域における、近畿・中部日本の断層の母岩と断層破砕物質について文献調査をおこない、その一部についての試料を入手した。中性子放射化法などの微量元素分析や粉末X線回折装置を併用して鉱物分析および状態分析を併用して母岩と断層破砕物質との化学組成の違い、同一母岩から生成したと考えられる断層破砕物質内での鉱物組成と化学組成の関係、酸化還元状態による鉱物組成と化学組成の差、採取地点の断層からの距離による断層破砕物質、母岩の種類、断層の種類による相違点などについて検討している。平成7年10月1日付けで東京大学・大学院理学系研究科から北海道大学・大学院地球環境科学研究科へ転出したために東京大学での研究は不可能になり、北大での放射線取り扱いの認可が遅れたためにデータ...
• Geochemical studies of Lake Baikal core sediment samples

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(国際学術研究)

  Date (from‐to) : 1994 -1995 

  Author : 原口 紘き, Hiroki HARAGUCHI, Dril S.I, Perepelov A, Kuzmin M, 堀江 正治, 小椋 和子, 石渡 良志, 豊田 和弘, 猿渡 英之, DRIL S.I, PEREPELOV A, KUZMIN M

   

  Lake baikal, the biggest lake in the world, is located in the central Siberia. According to the primary survey, it is known that the 5000-10000 m deep sediment may be accumulated in Lake Baikal during last ca.2000 million years. In the present research project entitled "Geochemical Studies on Sediment Core Samples from Lake Baikal", 2 kinds of the 100 m sediment core samples (BDP-93-1, BDP-93-2) collected in 1993 have been analyzed from the viewpoint of inorganic and organic geochemistry. These sediment core samples were taken and distributed under the BDP (Baikal Drilling Project) internat...
• Nuclear waste block-form and minerals of its natural analogue

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(一般研究(B))

  Date (from‐to) : 1993 -1994 

  Author : 床次 正安, Masayasu TOKOMANI, 豊田 和弘, 小野 洋子, 堀内 弘之, 小澤 徹

   

  Underground disposals of nuclear waste are considered to be indispensable for long-term isolation from the biosphere. The glass waste form will contain the highly radioactive isotopes extracted from spent nuclear fuel. Increasing crystallinity and alteration (metamictization) of waste glass by the effect of alpha-radiolysis and the associated release/retention of radionuclides are problem. Natural analogue is available to estimate the long-term behavior of the radionuclides. The objective is to establish the method of autoradiography of imaging plate (IP) system (R-AXIS-DS III) of block sam...
• 第四紀気候変動が湖の天然の栄養状態に及ぼした影響について・・・琵琶湖とバイカル湖のボーリング・コア討料の解析から

  文部科学省：科学研究費補助金(奨励研究(A))

  Date (from‐to) : 1993 -1994 

  Author : 豊田 和弘

   

  湖の富栄養化は大きな環境問題であるが、そのバックグランドといえる天然状態での湖の栄養状態(酸化還元状態や生物生産性)と気候変動との関係については研究が皆無である。本研究では構造湖で堆積盆の沈降により数十万年以上も現在と同様な水深を保ち続けていた琵琶湖やバイカル湖のボーリングコア試料をもちいて第四紀の氷河期間氷期の繰り返しと湖の栄養状態にどのような因果関係があるか調べることが目的である。当初は過去の琵琶湖の栄養状態の変化は堆積物の水酸化物相中の鉄マンガン比を測定することで推定できると考えていた。琵琶湖の1400mボーリングコアの最上部の120mの80試料について、還元剤で酸化物相中を抽出した後ICP発光分析法で、試料中の水酸化物相中の鉄マンガン比の値をだし、これまでの研究データと比較した。氷期が降水量の少ない時期に、現在のような間氷期が降水量の多い時期に対応すると考えられる。各種分析データの文献値から、降水量の多い時期は約25mから表層面まで、約65-95m、約130-145mであり、鉄マンガン比の値の値にそれに対応した変化があればと期待したが、値は約10-30とかなり変動するが、あまり対応関係はみられない。鉄やマンガンと似た挙動のヒ素についても放射化分析で分析してこの3元素から栄養状態の変化に対応する地球化学的指標を考察するよう現在分析中である。過去の富栄養化状態のもう一つの...
• Basic Study on Hemispheric Climatic Changes and on Transition of Paleoenvironments in Huge Tectonic Lakes.

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(国際学術研究)

  Date (from‐to) : 1991 -1991 

  Author : Kazuhiro TOYODA, Christian Sc, Michael Kuzm, Louis Scott, 竹村 恵二, 小椋 和子, 石渡 良志, 日比野 紘一郎, 堀江 正治

   

  1. PROGRAM CARRIED OUTIn our joint work on the present theme, we had concentrated our study to South Africa and lake Baikal ; the most distinguished features as tectonic lake are observed in both typical tectonic lakes such as Tanganyika and Baikal. As the first step to study Lake Tanganyika, we started stratigraphic study on the core sample obtained in Verloren Vlei because Lakes Tanganyika and Malauii is regarded as one unit of African tectonism extending to southern coast.On the other hand, paleolimnological study is carried out in Lake Paikal by Russian and American joint work supported...
• Studies on Rare-earth and Radioactive Minerals of Alkalline Complexes in Brazil.

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(国際学術研究)

  Date (from‐to) : 1989 -1990 

  Author : Masayasu TOKONAMI, 湊 秀雄, HASUI Yocite, HIODO Y.Fran, 豊田 和弘, 相川 信之, 芳賀 信彦, 小澤 徹, 堀内 弘之

   

  Research surveys of this project were performed for two years of 1989 and 1990, but have actually been continued since 1987. Main subjects of this project are the surveys of minerals which are closely related to alkaline rocks and carbonatite-alkaline complexes in Brazil and understanding their occurrences, mineral assemblages, textures, chemical compositions and so on. Concentration of rare-earth elements are characteristic in the complexes, and radioactive elements are often accompanied in minerals. Therefore, their minerals are also intersted as a natural analogue for the basic research ...
• Basic Research on the Minerals Related to High-Level Radioactive Wastes.

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(一般研究(A))

  Date (from‐to) : 1986 -1989 

  Author : Masayasu TOKONAMI, 山中 高光, 芳賀 信彦, 小澤 徹, 堀内 弘之, 豊田 和弘

   

  High-level radioactive wastes unavoidably remain whenever the used nuclear fuels are reprocessed for the next effective use. These wastes must be kept away from human being and animals in safety for a very long period. Thus, the search of the best way of their disposal is an emergency subject for the use of atomic energy. Most of researches on this problem are performed from technological point of view, however, basic researches of wasted substances are not strongly promoted.In this project, microtextures of minerals which are related to radioactive wastes are mainly investigated because su...
• レス堆積物及び湖底堆積物コアの無機化学分析と高精度な古環境変動解析、マンガン酸化バクテリアのマンガンイオン酸化反応機構と環境修復、古い活断層の活動履歴の検出法、隠れた火山灰層の検出法