Yu Saitoh, Umezawa Yu, Kawamoto Kazuaki, Tanimizu Masaharu and Ishikawa Tsuyoshi : Discriminatory power of 204Pb-inclusive Pb isotope systematics for seasonal variability in atmospheric Pb: evidence from western Japan, Applied Geochemistry, 2026.
Yu Saitoh and Dan Matsumoto : The Sr isotope ratio of sediment leachate: A potential indicator of tsunami inundation, Geochemical Journal, 59, 6, 262-270, 2025.
(Summary)
<p>Detecting seawater-derived elements in terrestrial sediments as evidence of tsunami inundation is challenging due to dilution by freshwater over time. This study provides data useful for evaluating the potential of the strontium (Sr) isotope ratios (87Sr/86Sr) as indicators of seawater intrusion. We analyzed 87Sr/86Sr ratios in water leachates and acetic acid (AcOH) leachates from a sedimentary sequence sampled in November 2015 from a coastal lowland in Tohoku, Japan, which includes deposits from the March 2011 Tohoku earthquake tsunami.</p><p>The 87Sr/86Sr values of water leachates were low (~0.7082) in the pre-tsunami muddy layer, close to local freshwater values (0.7069), but higher (~0.7085) in the upper muddy part of the tsunami deposit, approaching seawater values (0.7092). This suggests that the muddy part retained seawater-derived Sr due to its low permeability and high cation adsorption capacity of clay minerals. However, alternative sources of high Sr isotope ratios, such as rainwater, atmospheric deposition, and acid-leachable materials, must be considered. If the high values reflect seawater intrusion, Sr isotope ratios provide a distinct advantage over element concentrations as tsunami indicators due to their longer retention, detectable even four years after the event.</p><p>In contrast, AcOH leachates exhibited significantly higher Sr isotope ratios (>0.7095) throughout the sequence, perhaps reflecting contributions from less-soluble components, such as oxides and clay minerals, in addition to marine carbonates. This finding suggests that AcOH leaching is unsuitable for isolating seawater-derived Sr.</p>
Razieh Chaharlang, Jalil Ghalamghash, Yu Saitoh, Mihai N. Ducea and Axel K. Schmitt : Sr Nd isotopes of Sabalan Volcano, NW Iran: insights into the origin of collisional adakites and geodynamic implications, International Journal of Earth Sciences, 112, 2065-2080, 2023.
A. Tsuneki, N. Watanabe, Ryo Anma, S. Jammo, Yu Saitoh and S. Ahmad : Preliminary report of the Charmo (Jarmo) Prehistoric investigations, Al -Rafidan, 44, 1-34, 2023.
(Summary)
The field expedition at Charmo was executed from July 23 to September 15, followed by supplemental work in the field and material studies until September 27, 2022.
(Keyword)
Neolithization | Iraqi-Kurdistan | Charmo site | The Fertile Crescent | Neolithic period | Jarmo
Etsuo Uchida, Shinya Nagano, Sota Niki, Kou Yonezu, Yu Saitoh and Ki-Cheol Shin : Geochemical and radiogenic isotopic signatures of granitic rocks in Chanthaburi and Chachoengsao provinces, southeastern Thailand: Implications for origin and evolution, Journal of Asian Earth Sciences: X, 8, 100111, 2022.
(Summary)
The Chanthaburi, Pliew, Klathing, Khao Cha Mao, and Khao Hin Son granitic bodies in Chanthaburi and Chachoengsao provinces in southeastern Thailand, which are located on the southwestern side of the Mae Ping Fault and eastern side of the Klaeng Fault, were investigated. In this study, magnetic susceptibility measurements, whole-rock chemical composition and Nd-Sr isotope analyses, and zircon U-Pb dating were conducted on these granitic bodies. The surveyed granitic rocks are classified as I- to A-type granites, are of the ilmenite series, and show clearly negative Eu anomalies, which suggest they formed under reducing conditions. Nd-Sr isotope ratios indicate continental crust material involvement in the formation of these granite bodies. The magnetic and geochemical signatures are similar to those of granite bodies in southwestern Cambodia. The study area is thus considered an extensional area of southwestern Cambodia, corresponding to the Sukhothai Zone (the Chanthaburi-Kampong Chhnang Zone). Zircon U-Pb dating yields ages of 208–214 Ma (the Late Triassic) for granite bodies except for the Khao Cha Mao granitic body, which dates to 55 Ma. The former age corresponds to the collision time of the Sibumasu and Indochina terranes, and the latter age is likely related to the collision time of the Indian and Eurasian continents.
Umezawa Yu, Toyoshima Kanae, Yu Saitoh, Takeda Shigenobu, Tamura Kei, Tamaya Chiaki, Yamaguchi Akira, Yoshimizu Chikage, Tayasu Ichiro and Kawamoto Kazuaki : Evaluation of origin-depended nitrogen input through atmospheric deposition and its effect on primary production in coastal areas of western Kyushu, Japan, Environmental Pollution, 291, 118034, 2021.
(Summary)
Long term monitoring of atmospheric wet and dry depositions and associated nutrients fluxes was conducted on the coast of Japan facing the East China Sea continuously for 1 year and 2 months, with the origin of air mass investigated based on isotope analyses (Sr, Nd, and NO). During the same period, intensive observations of ocean conditions and the chemical composition of sinking particles collected using sediment traps were conducted to investigate the effects of atmospheric deposition-derived nutrients on phytoplankton blooms. Dry-deposition-derived nutrient inputs to the surface ocean were larger during autumn to spring than in summer due to the effect of continental air mass occasionally carrying Asian dust (yellow sand). However, these nutrients fluxes were limited (1.1-1.5 mg-N m day on average) and didn't appear to cause phytoplankton blooms through the year. Although average dissolved inorganic nitrogen (DIN) concentrations in rainwater were lower in oceanic air masses compared to continental air masses, wet-deposition-derived nutrient inputs to the surface ocean on rainy days during the summer (26.0 mg-N m day on average) were large due to higher precipitation from oceanic air masses. Wet-deposition-derived nutrients significantly increased nutrient concentrations in the surface ocean and seemed to cause phytoplankton blooms in the warm rainy season when nutrients in the surface were depleted due to increased stratification. The increase in phytoplankton biomass was reflected in increased particle sinking into the bottom layer, as well as changing chemical characteristics. The supply of flesh phytoplankton-derived labile organic matter into the bottom layer could be expected to promote rapid bacterial decomposition and contribute to the formation of hypoxic water masses in early summer when the ocean was strongly stratified. Atmospheric deposition-derived nutrients in East Asia will have important impacts on not only the oligotrophic outer ocean but also surrounding coastal areas in the warm rainy season.
(Keyword)
Environmental Monitoring / Japan / Nitrogen / Oceans and Seas / Phytoplankton
Etsuo Uchida, Yuichiro Sakurai, Rathborith Cheng, Ichita Shimoda and Yu Saitoh : Supply ranges of stone blocks used in masonry bridges and their construction period along the East Royal Road in the Khmer Empire, Cambodia, Heritage Science, 8, 1, 2020.
(Keyword)
Bridge / Chemical composition / Cluster analysis / East Royal Road / Khmer monuments / Laterite / Magnetic susceptibility / Principal component analysis / Sandstone
Yu Saitoh, Tsuyoshi Ishikawa and Masaharu Tanimizu : Sr-Nd-Pb isotope systematics of fine sediments from the modern rivers in SW Japan: Implications for sediment provenance of the Northwest Pacific, Journal of Asian Earth Sciences: X, 3, 100029, 2020.
Takanori Nakano, Katsuyuki Yamashita, Atsushi Ando, Soichiro Kusaka and Yu Saitoh : Geographic variation of Sr and S isotope ratios in bottled waters in Japan and sources of Sr and S, The Science of the Total Environment, 704, 135449, 2020.
(Summary)
The geographic distribution of the stable isotope ratio of Sr (Sr/Sr) is useful for identifying the provenance of drinking water, organisms, and agricultural products. To explore how environmental factors influence this ratio, we determined the Sr/Sr, sulfur isotope ratio (δS), and elemental composition of 208 commercially available bottled waters in Japan, and compared them with the Sr/Sr 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 Sr/Sr 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 Sr/Sr of reported spring waters, indicating that bottled water, like other groundwater, reflects the lithology and chemistry of its aquifer. The Sr/Sr of bottled water, taken as a proxy for groundwater, showed regional variations consistent with those of rocks and vegetables, demonstrating that an Sr/Sr map of water and agricultural products has value for determining the production areas of these substances. However, the value and range of Sr/Sr 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 δS of bottled waters with Sr/Sr 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.
(Keyword)
Drinking Water / Environmental Monitoring / Japan / Strontium Isotopes / Sulfur Isotopes / Water Pollutants, Chemical
Ohta Tamihisa, Shin Ki-Cheol, Yu Saitoh, Nakano Takanori and Hiura Tsutom : The effects of differences in vegetation on calcium dynamics in headwater streams, Ecosystems, 21, 7, 1390-1403, 2018.
(Keyword)
Ecology / Environmental Chemistry / Ecology, Evolution, Behavior and Systematics
Jun Matsubayashi, Yu Saitoh, Yutaka Osada, Yoshitoshi Uehara, Junko Habu, Tsuyoshi Sasaki and Ichiro Tayasu : Incremental analysis of vertebral centra can reconstruct the stable isotope chronology of teleost fishes, Methods in Ecology and Evolution, 8, 1755-1763, 2017.
(Keyword)
Ecological Modelling / Ecology, Evolution, Behavior and Systematics
Toru Tamura, Yoshinori Kodama, D. Mark Bateman, Yu Saitoh, Naofumi Yamaguchi and Dan Matsumoto : Late Holocene aeolian sedimentation in the Tottori coastal dune field, Japan Sea, affected by the East Asian winter monsoon, Quaternary International, 397, 147-158, 2016.
(Keyword)
Coastal dune / Ground-penetrating radar / Japan Sea / Little Ice Age / Monsoon / Optically-stimulated luminescence dating
Yu Saitoh, Tsuyoshi Ishikawa, Masaharu Tanimizu, Masafumi Murayama, Yurika Ujiie, Yuzuru Yamamoto, Kohtaro Ujiie and Toshiya Kanamatsu : Sr, Nd, and Pb isotope compositions of hemipelagic sediment in the Shikoku Basin: implications for sediment transport by the Kuroshio and Philippine Sea plate motion in the late Cenozoic, Earth and Planetary Science Letters, 421, 47-57, 2015.
Yu Saitoh and Fujio Masuda : Spatial change of grading pattern of subaqueous flood deposits in Lake Shinji, Japan, Journal of Sedimentary Research, 83, 2, 221-233, 2013.
Yu Saitoh and Masuda Fujio : Spatial change of grading pattern of subaqueous flood deposits in Lake Shinji, Japan, Journal of Sedimentary Research, 83, 3, 193-205, 2013.
Toru Tamura, D. Mark Bateman, Yoshinori Kodama, Yu Saitoh, Kazuaki Watanabe, Naofumi Yamaguchi and Dan Matsumoto : Building of shore-oblique transverse dune ridges revealed by ground-penetrating radar and optical dating over the last 500years on Tottori coast, Japan Sea, Geomorphology, 132, 3-4, 153-166, 2011.
(Keyword)
East Asia / GPR / Monsoon / OSL dating / The Little Ice Age
Toru Tamura, Yoshinori Kodama, D. Mark Bateman, Yu Saitoh, Kazuaki Watanabe, Dan Matsumoto and Naofumi Yamaguchi : Coastal barrier dune construction during sea-level highstands in MIS 3 and 5a on Tottori coast-line, Japan, Palaeogeography, Palaeoclimatology, Palaeoecology, 308, 3-4, 492-501, 2011.
(Keyword)
East Asia / Ground-penetrating radar / Japan Sea / Optically-stimulated luminescence dating / Pleistocene / Sea-level change
Yu Saitoh, Tamura Toru, Kodama Yoshinori and Nakano Takanori : Strontium and neodymium isotopic signatures indicate the provenance and depositional process of loams intercalated in coastal dune sand, western Japan, Sedimentary Geology, 236, 272-278, 2011.
Takanori Nakano, Ichiro Tayasu, Yoshihiro Yamada, Takahiro Hosono, Akitake Igeta, Fujio Hyodo, Atsushi Ando, Yu Saitoh, Takuya Tanaka, Eitaro Wada and Shigeo Yachi : Effect of agriculture on water quality of Lake Biwa tributaries, Japan, The Science of the Total Environment, 389, 1, 132-148, 2007.
(Summary)
We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO(3), SO(4), NO(3), Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta(34)S values of SO(4) in the river water converged to 0+/-2 per thousand as the SO(4) concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO(3) concentration increased. In particular, both the delta(34)S values (0+/-2 per thousand) and the (87)Sr/(86)Sr ratios (0.7117+/-0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta(34)S values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable (87)Sr/(86)Sr in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO(3), owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO(3) and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries.
(Keyword)
Agriculture / Lake Biwa / S isotope / Sr isotope / Tributary / Water quality
Yu Saitoh and Fujio Masuda : Miocene sandstone of continental origin on Iriomote Island, southwest Ryukyu arc, Eastern Asia, Journal of Asian Earth Sciences, 24, 2, 137-144, 2004.
Yu Saitoh, Tamura Toru and Fujio Masuda : Hyperpycnal-flow deposits from the Miocene continental delta complex in the Ryukyu islands arc, southwest Japan, Mega-deltas of Asia - Geologic evolution and human impact, 262-268, 2005.
Review, Commentary:
1.
Yu Saitoh, Tamura Toru and Fujio Masuda : タービダイト・パラダイムの革新的要素としてのハイパーピクナル流とその堆積物の特徴, Journal of Georaphy, 114, 5, 687-704, Dec. 2005.
Proceeding of Domestic Conference:
1.
Yu Saitoh : Contour current sedimentation suggested by paleocurrents: an example from the Eocene Nahargawa Formation of the Muroto Peninsula Group, 日本堆積学会2025年大会, Apr. 2025.
Yu Saitoh : 泥の起源と行方:黒潮は砕屑粒子を遠洋域まで運べるのか?, 日本堆積学会20周年記念リレーセミナー, 0, 0, 0, Mar. 2023.
Report:
1.
Ryo Anma, 申 基澈, 渡辺 千香子, 辻 彰洋, 佐野 貴司, Yu Saitoh, 中野 孝教, 横尾 頼子, 小泉 龍人, Mark Altaweel, Anke Marsh, Hashim Hama, Kamal Rasheed and Jaafar Jotheri : スレマニ博物館所蔵の楔形文書粘土板胎土の化学組成, 都市文明の本質:古代西アジアにおける都市の発生と変容の学際研究 研究成果報告2022年度, 147-152, Mar. 2023.
2.
Yu Saitoh : Data Report: grain size distribution of the late Cenozoic hemipelagic mud from Site C0011, Proceedings of the Integrated Ocean Drilling Program, 333, 203, Apr. 2014.
Petrological study on stone materials and their deterioration in the Khmer monuments including the Angkor monuments (Project/Area Number: 19KK0016 )
Water and soil environmental changes and dawn of urban mine around the early cities in Ancient West Asia (Project/Area Number: 18H05447 )
Evaluation of the potential of iron-manganese oxides as information on the origin of sediment-carrying water (Project/Area Number: 18K03765 )
Development of the precise analytical techniques for studying migratory history using isotope ratios of heavy elements (Project/Area Number: 15K14602 )
Sr-Nd-Pb isotope ratios of hemipelragic sediments as the tracer of plate motion (Project/Area Number: 26870418 )
The effects of bioproduction in the East China Sea on cloud fields viewed from marine bio-originated aerosols (Project/Area Number: 24340114 )