齋藤 有 (サイトウ ユウ)

写真a

所属

理工学術院 創造理工学部

職名

講師(任期付)

学位 【 表示 / 非表示

  • 京都大学   博士(理学)

 

研究分野 【 表示 / 非表示

  • 地球生命科学   堆積学・同位体地球化学

研究キーワード 【 表示 / 非表示

  • ハイパーピクナイト

  • 後背地

  • 同位体

  • 堆積物

論文 【 表示 / 非表示

  • Sr-Nd-Pb isotope systematics of fine sediments from the modern rivers in SW Japan: Implications for sediment provenance of the Northwest Pacific

    Yu Saitoh, Masaharu Tanimizu, Tsuyoshi Ishikawa

    Journal of Asian Earth Sciences: X   3   100029 - 100029  2020年06月  [査読有り]

    DOI

  • Geographic variation of Sr and S isotope ratios in bottled waters in Japan and sources of Sr and S

    Takanori Nakano, Katsuyuki Yamashita, Atsushi Ando, Soichiro Kusaka, Yuh Saitoh

    Science of the Total Environment    2019年01月  [査読有り]

     概要を見る

    © 2019 Elsevier B.V. The geographic distribution of the stable isotope ratio of Sr (87Sr/86Sr) is useful for identifying the provenance of drinking water, organisms, and agricultural products. To explore how environmental factors influence this ratio, we determined the 87Sr/86Sr, sulfur isotope ratio (δ34S), and elemental composition of 208 commercially available bottled waters in Japan, and compared them with the 87Sr/86Sr values of groundwater, rainwater, rocks, and vegetables from similar localities. We classified the bottled waters into seven categories based on the geology of their source aquifers. The 87Sr/86Sr and concentrations of several elements (Ca, K, Si, Rb, and Ba) of the bottled waters differed with the aquifer rock type and were well correlated with the 87Sr/86Sr of reported spring waters, indicating that bottled water, like other groundwater, reflects the lithology and chemistry of its aquifer. The 87Sr/86Sr of bottled water, taken as a proxy for groundwater, showed regional variations consistent with those of rocks and vegetables, demonstrating that an 87Sr/86Sr map of water and agricultural products has value for determining the production areas of these substances. However, the value and range of 87Sr/86Sr differed among these three materials, and the degree of the difference between groundwater and rock depended on the rock type. An analysis of geochemical data from rocks and rainwater suggests that groundwater contains Sr and additional S derived from atmospheric sources such as rainwater and sea salt aerosols. The atmospheric contribution of Sr to groundwater is greatest in areas of siliceous sedimentary rocks with low Sr concentrations and high resistance to weathering. A weak correlation of δ34S of bottled waters with 87Sr/86Sr indicates the usefulness of maps of combined Sr and S isotope ratios for groundwater provenance. This study shows that for accurate provenance determinations of groundwater, organisms, and agricultural products, it is essential to better quantify the contributions of Sr and S from the atmosphere as well as from rocks and human activities.

    DOI PubMed

  • The Effects of Differences in Vegetation on Calcium Dynamics in Headwater Streams

    Tamihisa Ohta, Ki-Cheol Shin, Yu Saitoh, Takanori Nakano, Tsutom Hiura

    Ecosystems   21 ( 7 ) 1390 - 1403  2018年11月  [査読有り]

    DOI

  • 鳥取砂丘の地中レーダ断面

    田村 亨, 小玉芳敬, 齋藤 有, 渡辺和明, 山口直文, 松本 弾

    第四紀研究   49   357-368  2010年12月  [査読有り]

  • RADIONUCLIDES IN ANCIENT RELICS OBTAINED FROM THE MATSUSAKI SITE AND THE HIROHATA SHELLMOUND ON THE PACIFIC COAST OF JAPAN

    Tomoko Ohta, Yasunori Mahara, Takumi Kubota, Yu Saito, Satoshi Fukutani, Toshiyuki Fujii, Atsushi Ando, Eiji Nakata, Takanori Nakano, Yoshiro Abe, Akira Tatematsu

    RADIOCARBON   52 ( 2 ) 526 - 533  2010年  [査読有り]

     概要を見る

    We compared 2 archaeological relics of different preservation environments, white substances adhering to a vessel from the Matsusaki site and to earthenware from Hirohata, by measuring their environmental radioactivity, (14)C, (228)Ra/(226)Ra, (234)U/(238)U, and (87)Sr/(86)Sr, and major element contents (Ca, Sr, Mg, Fe, and Mn). The results showed that the 2 materials were somewhat different and also reflected differences in their preservation environments. The chemical elements that were more abundant in the Matsusaki sample than in the Hirohata sample, Fe, Mn, (238)U, and (232)Th (parent of (228)Ra), are also abundant in seaweed or seagrass. Contamination by (14)C derived from rainwater after atmospheric nuclear tests was clearly observed in the white substance from Hirohata.

    J-GLOBAL

Misc 【 表示 / 非表示

  • The Effects of Differences in Vegetation on Calcium Dynamics in Headwater Streams

    Tamihisa Ohta, Ki Cheol Shin, Yu Saitoh, Takanori Nakano, Tsutom Hiura

    Ecosystems   21   1390 - 1403  2018年11月

     概要を見る

    © 2018, Springer Science+Business Media, LLC, part of Springer Nature. Although organisms can alter dynamics of elements in ecosystems via physiological results, the effects of tree species on ecosystem nutrient dynamics are highly uncertain. A four-fold variation in the calcium concentrations of streams, soils and leaf litters were caused by the planting of Cryptomeria japonica in south-central Japan. In this study, we examined how the calcium dynamics were affected by the planting of C. japonica through strontium isotope analysis. We predicted the planting of C. japonica would result in the calcium concentration increasing because of the significant dissolution of calcium from bedrock. In a forest ecosystem, calcium is usually derived from precipitation and bedrock weathering, and their relative contributions can be estimated using a strontium isotope mixing model. Therefore, we collected stream water, litter, soil, precipitation and bedrock samples from 17 sites in catchments dominated by C. japonica plantation or evergreen broad-leaved forest; after collection, we analyzed the sample chemical compositions and strontium isotope ratios. The calcium concentrations in the stream water and the water-soluble calcium in the soil were significantly higher at sites dominated by C. japonica than at broad-leaved forest sites. Strontium isotope analysis indicated that there was more calcium from the bedrock present in stream water at sites dominated by C. japonica than in stream water at broad-leaved forest sites. Our results showed that watershed-scale dynamics of calcium and other cations can be altered by the type of vegetation in a catchment due to the effects of vegetation on the supply of calcium from bedrock.

    DOI

  • Utility of Nd isotope ratio as a tracer of marine animals: regional variation in coastal seas and causal factors

    Yu Saitoh, Takanori Nakano, Ki-Cheol Shin, Jun Matsubayashi, Yoshikazu Kato, Hiroshi Amakawa, Yutaka Osada, Chikage Yoshimizu, Noboru Okuda, Yosuke Amano, Hiroyuki Togashi, Yutaka Kurita, Ichiro Tayasu

    Ecosphere   9 ( 8 ) e02365 - e02365  2018年08月

     概要を見る

    © 2018 The Authors. Isotopic compositions of animal tissue are an intrinsic marker commonly used to trace animal origins and migrations; however, few isotopes are effective for this purpose in marine environments, especially on a local scale. The isotope ratio of the lanthanoid element neodymium (Nd) is a promising tracer for coastal animal migrations. Neodymium derives from the same geologic materials as strontium, well known as an isotopic tracer (87Sr/86Sr) for terrestrial and anadromous animals. The advantage of the Nd isotope ratio (143Nd/144Nd, expressed as εNd) is that it varies greatly in the ocean according to the geology of the neighboring continents, whereas oceanic 87Sr/86Sr is highly uniform. This study explored the utility of the Nd isotope ratio as a marine tracer by investigating the variation of εNd preserved in tissues of coastal species, and the causes of that variation, in a region of northeastern Japan where the bedrock geology is highly variable. We measured εNd and 87Sr/86Sr in seawater, river water, and soft tissues of sedentary suspension feeders: the mussels Mytilus galloprovincialis and Mytilus coruscus and the oyster Crassostrea gigas. We also measured concentrations of three lanthanoids (La, Ce, and Pr) in shellfish bodies to determine whether the Nd in shellfish tissue was derived from solution in seawater or from suspended particulates. The εNd values in shellfish tissue varied regionally (−6 to +1), matching the ambient seawater, whereas all 87Sr/86Sr values were homogeneous and typical of seawater (0.7091–0.7092). The seawater εNd values were in turn correlated with those in the adjacent rivers, linking shellfish εNd to the geology of river catchments. The depletion of Ce compared to La and Pr (negative Ce anomaly) suggested that the Nd in shellfish was derived from the dissolved phase in seawater. Our results indicate that the distinct Nd isotope ratio derived from local geology is imprinted, through seawater, on the soft tissues of shellfish. This result underscores the potential of εNd as a tracer of coastal marine animals.

    DOI

  • Incremental analysis of vertebral centra can reconstruct the stable isotope chronology of teleost fishes

    Jun Matsubayashi, Yu Saitoh, Yutaka Osada, Yoshitoshi Uehara, Junko Habu, Tsuyoshi Sasaki, Ichiro Tayasu

    METHODS IN ECOLOGY AND EVOLUTION   8 ( 12 ) 1755 - 1763  2017年12月

     概要を見る

    1. Isotope analysis has high potential for understanding fish ecology and food-web structure in aquatic ecosystems. The utility of isotope analysis will be greatly improved if we can reconstruct the chronology of several isotopes at multiple growth stages of individual fish. However, no practical methods exist for reconstructing the chronology of light-element isotopes (e.g. C-13, N-15, S-34, and C-14) in teleost fishes. Here, we present and test a new analytical approach for reconstructing the isotopic ratios of light isotopes at multiple life-stages in teleost fishes.
    2. We sampled an anadromous salmon species, masu salmon Oncorhynchus masou (n=3), along with water from its natal stream and from the ocean. We subdivided the vertebral centra of the salmon equally into 10 sections and extracted bone collagen from each sample. We then measured the stable sulphur isotope ratios of each vertebral section and compared them with S-34 values of the river water and sea water. We also measured the Sr-87/Sr-86 ratios of otoliths as a reference indicator of salmon migration between fresh water and the ocean.
    3. In all samples, the bone section closest to the centre of the centrum had the lowest S-34 values, which were similar to those of fresh water. The S-34 values gradually increased from the centre to marginal sections, finally reaching constant values similar to those of seawater. The Sr-87/Sr-86 ratios of sagittal otolith sections had significant inter-individual differences and were consistent with the patterns of variation of the S-34 values of the vertebral sections.
    4. Our results show that the vertebral centra of teleost fishes record isotopic information from juvenile to adult life stages. We suggest that our method can provide reproducible isotopic chronology, even in teleost fishes smaller than 50cm. This method can be used in isoscape studies and in studies of the ecology of marine teleost fishes.

    DOI

  • Geochemical constraints on the sources of beach sand, southern Sendai Bay, northeast Japan

    Yu Saitoh, Toru Tamura, Takanori Nakano

    MARINE GEOLOGY   387   97 - 107  2017年05月

     概要を見る

    Unraveling the precise sources of sand and their quantitative contributions to a beach is beneficial for effective coastal management. To demonstrate a method for provenance analysis serving that practical purpose, we conducted a case study of the southern coast of Sendai Bay, a storm-wave dominated coast facing the NW Pacific Ocean. To eliminate the effect of hydraulic sorting, which changes sediment composition independently of the sediment source, we analyzed only medium-sand-sized light minerals (density < 2.65 g cm(-3)), which consisted mainly of quartz and feldspars. Concentrations of Al, Na, K, Ca, Mg, Fe, Rb, Sr, Ba, and Pb in the fraction were measured. In addition to that, the Sr isotope ratio, Sr-87/Sr-86, was considered to compensate for the weakened compositional contrast due to the limited mineralogy. We first compared the chemical compositions, which were transformed to centered log-ratio in order to get rid of the constant-sum constraints, and Sr isotope ratio between beach samples and possible sources. Second, we estimated the contributions of the presumed sources by comparing the chemical and isotopic composition of beach sand samples with an ideal composition calculated by assuming simple mixing of source sediments. Finally, under the assumption that the contributions derived by analyzing medium-sand-sized light minerals are also applicable to bulk beach sand, we calculated the total amount contributed by the sources to the beach in the past few decades as the sum of the products of the contributions of each source and the change of the sediment volume at each site along the coast. Our measurements of 19 samples of beach sand and 12 of riverbed sediment showed that the main sources of beach sand were the Abukuma River, which enters the ocean near the center of the study area, and coastal cliffs composed of Mio-Pliocene sedimentary rocks at the southern end of the beach. Contributions from other rivers were negligible. The contribution of the Abukuma River gradually increased northward from about 10% at a point 20 km south of the river's mouth to more than 80% at a point 20 km north of the mouth. We inferred that this alongshore change was due to the dominant northward direction of longshore currents and the locations of the two main sources. Thus, sediments from both sources migrate preferentially northward, transported by the longshore currents, and the amount of sediment derived from the Abukuma River, relative to the amount from the coastal cliffs, increases northward. We assumed that the sources of the medium-sand-sized light-minerals are the same as those of the bulk sediments and estimated the annual contribution of the Abukuma River and the coastal cliffs to the whole beach system to be 3.8 x 10(4) m(3) and 4.1 x 10(4) m(3), respectively. The annual contribution of the river to the beach sediment is about 34% of its estimated annual sediment discharge. The rest of the discharged sediment is presumably retained on the seafloor.

    DOI

  • Late Holocene aeolian sedimentation in the Tottori coastal dune field, Japan Sea, affected by the East Asian winter monsoon

    Toru Tamura, Yoshinori Kodama, Mark D. Bateman, Yu Saitoh, Naofumi Yamaguchi, Dan Matsumoto

    QUATERNARY INTERNATIONAL   397   147 - 158  2016年03月

     概要を見る

    Many dune fields that have formed along the southern coast of the Japan Sea are influenced by the north-westerly winter monsoon, which transports beach sand landwards. The Tottori coastal dune field of the Japan Sea has not been disturbed much by human activities until the 20th century and thus is expected to provide a continuous record of the relationships between the winter monsoon and aeolian sedimentation. We examined new ground-penetrating radar profiles and optically stimulated luminescence (OSL) ages of quartz sand from transverse dune ridges in the western part of the dune field in addition to existing data in the eastern part. This allowed us to extend the study period to cover the past 1000 years and to effectively compare the sedimentary record with other coastal dune fields in East Asia and other palaeoenvironmental proxies. OSL ages from older dune sediments suggest considerable aeolian activity from the 10th to 12th century AD, whereas a hiatus of dune sediment record between the 12th and 15th centuries was detected. These results suggest that during the Medieval period aeolian activity was low or that extensive erosion removed most of the deposits. Since the late 15th century, dune sedimentation has apparently been broadly continuous, though with periods of higher and lower activity. In both of the eastern and western parts, most of the dune ridges accreted landwards, but clear seaward accretion occurred during the 18th century, possibly reflecting a decrease in wind strength that restricted sand transport. In contrast, two significant landward accretion events are inferred to have occurred from the late 15th to 17th centuries and around 1840, corresponding to periods of increased dust fall in China, which suggests an enhanced winter monsoon, and to cold periods suggested by the decline of the sunspot number. The timing of periods of inactive and active dune sedimentation, inferred from alternations of organic soil and aeolian sand, in other coastal dune fields of East Asia appears to be concordant with corresponding periods in the Tottori dune field. We thus propose that other Japan Sea dune fields may also provide a valuable record of East Asian winter monsoon fluctuations. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.

    DOI

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