Updated on 2024/02/04

写真a

 
OSAKA Kenichi
 
Organization
Faculty of Environmental Science
Department
School of Environmental Science Department of Ecosystem Studies
Title
Associate Professor
URL
http://www.ses.usp.ac.jp/lab/osaka/
External link

Education

  • Kyoto University   Graduate School, Division of Agriculture

    　 More details

    Course completed： Doctor's Course

    Country： Japan

  • The University of Shiga Prefecture

    　 More details

    Country： Japan

Degree

  • 博士(農学) ( 2007.5   京都大学 )

Research Field

  • Forest Hydrology, Biogeochemistry

Research Experience

  • The University of Shiga Prefecture   School of Environmental Science Department of Ecosystem Studies   Associate Professor

    2022.4

  • The University of Shiga Prefecture   School of Environmental Science Department of Ecosystem Studies   Lecturer

    2019.4 - 2022.3

  • The University of Shiga Prefecture   School of Environmental Science Department of Ecosystem Studies   Assistant Professor

    2010.8 - 2019.3

  • 山梨大学医学工学研究部　国際流域環境研究センター   研究員

    2009.4 - 2010.7

    　 More details

    Country：Japan

  • 独立行政法人農業環境技術研究所   研究員

    2007.4 - 2009.3

    　 More details

    Country：Japan

Association Memberships

  • 土壌肥料学会

    2008.4

  • 水環境学会

    2008.4

  • AGU

    2008.4

  • 陸水学会

    2008.4

Research Areas

  • Environmental Science/Agriculture Science / Environmental dynamic analysis

Papers

  • Hydrological and biogeochemical controls of the seasonality of particulate and dissolved nitrogen exports during rainfall events from a forested watershed in monsoon Asia, Japan Reviewed

    Osaka, K., Kunimatsu, T., Hida, Y., Komai, Y., Katsuyama, M., Ohte, N.

    Water Resources Research   59   2023.11

    　More details

    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： doi.org/10.1029/2023WR034756

  • Nitrogen Contamination and Denitrification Occurrence in Shallow Groundwater of Urbanized Area at Kathmandu Valley, Nepal Reviewed

    Nakamura, T., Osaka, K., Chapagain, S. K., Nishida K.

    Journal of Geography (Chigaku Zasshi)   2023.3

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

    DOI： doi:10.5026/jgeography.132.183

  • Assessing the changes in river water quality across a land-use change (forest to oil palm plantation) in peninsular Malaysia using the stable isotopes of water and nitrate Reviewed International journal

    Itoh M., Osaka K., Iizuka K., Kosugi Y., Lion M., Shiodera S.

    Science of the Total Environment   859   2023.2

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Science of the Total Environment   Participation form：Joint(The vice charge)  

    Land conversion from natural forests to plantations (e.g., oil palm) in Southeast Asia is one of the most intensive land-use changes occurring worldwide. To clarify the effects of oil palm plantations on water quality, we conducted multipoint river and stream water sampling in peninsular Malaysia at the end of the rainy season over a 3-year period (2013–2015). We measured the major dissolved ions and stable isotope ratios of water (δ2H-H2O and δ18O-H2O) and nitrate (δ15N-NO3− and δ18O-NO3−) in water from the upper streams in mountainous forests to the midstream areas of two major rivers in peninsular Malaysia. The electrical conductivity increased, and the d-excess value (as an index of the degree of evaporation) decreased with increasing distance from the headwaters, suggesting the effect of evaporative enrichment and the addition of pollutants. We separated the sampling points into four groups (G1–G4) through cluster analysis of the water quality data. From the land use/land cover (LULC) classification maps developed from satellite images and local information, we found that G1 and G2 mainly consisted of sampling points in forested areas, while G3 and G4 were located in oil-palm-affected areas. The concentrations of major ions were higher in the oil palm areas, indicating the effects of fertilizer and limestone (i.e., pH adjustment) applications. The dissolved inorganic nitrogen concentration did not differ among the groups, but the dissolved organic carbon, total dissolved nitrogen, and δ15N-NO3− were higher in the oil palm area than in the forested area. Although the nitrogen concentration was low, even in the oil palm area, the significantly higher δ15N-NO3− in the oil palm area indicated substantial denitrification. This implies that denitrification contributed to the lowering of the NO3− concentration in rivers in the oil palm area, in addition to nutrient uptake by oil palm trees.

    DOI： 10.1016/j.scitotenv.2022.160319

    Scopus

    Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85142359418&origin=inward

  • Hydrological control of the chemical characteristics of suspended particulate phosphorus in the Yasu River watershed, Japan: Implications for its source and bioavailability Reviewed International journal

    Osaka, K., Chishiro, S., Matsumoto, Y., Iwata T., Okuda, N.

    Hydrological Processes   36 ( 10 )   2022.11

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

  • Effect of dissolved oxygen on nitrogen and phosphorus fluxes from lake sediments and their thresholds based on incubation using a simple and stable dissolved oxygen control method Reviewed International journal

    Osaka, K., Yokoyama, R., Ishibashi, T., Goto, N.

    Limnology and Oceanography: Methods   20 ( 1 )   1 - 14   2022.2

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

    DOI： doi.org/10.1002/lom3.10466

  • 元素分析計連結型安定同位体比質量分析計の簡易改造による微量試料炭素窒素安定同位体比測定 Reviewed

    木庭啓介、木下桂、大西雄二、福島慶太郎、尾坂兼一、松尾奈緒子、舟川一穂、瀬古祐吾、目戸綾乃、平澤理世、小川奈々子、兵藤不二夫、由水千景

    RADIOISOTOPE   2021.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Factors characterizing phosphate oxygen isotope ratios in river water: an inter-watershed comparison approach Reviewed

    Ide J., Ishida T., Cid-Andres A.P., Osaka K., Iwata T., Hayashi T., Akashi M., Tayasu I., Paytan A., Okuda N.

    Limnology   2020.1

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Limnology  

    © 2020, The Japanese Society of Limnology. We compared the oxygen isotope ratio of dissolved phosphate (δ18OPO4) in two rivers with different land-cover and geological features (Ado River and Yasu River) within Lake Biwa basin, central Japan, to explore what factor primarily characterizes the δ18OPO4. Mean values of δ18OPO4 in river water were 19.0 ± 2.4‰ (n = 7) in Ado River and 13.1 ± 2.3‰ (n = 15) in Yasu River, which were significantly different. Comparisons of δ18OPO4 between river water and potential sources of phosphate revealed that in the Ado River, the δ18OPO4 was similar to that in rocks from the accretionary complex and decreased with increasing sedimentary rock coverage. In the Yasu River, the δ18OPO4 was low in the upper forested areas, but increased with paddy field coverage. These results demonstrate that river δ18OPO4 strongly reflects inputs from geological substances, but is also impacted by land-use activities and varies with anthropogenic land coverage in the watershed. Thus, river δ18OPO4 relates to land or bedrock coverage differentially in each river. Regression analysis showed that residuals of the δ18OPO4 tended to converge to zero with increasing drainage area, suggesting that river δ18OPO4 more explicitly reflects land-cover and geological features on a larger watershed scale.

    DOI： 10.1007/s10201-020-00610-6

    Scopus

    Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85082952035&origin=inward

  • Identification of Phosphorus Sources in a Watershed Using a Phosphate Oxygen Isoscape Approach Reviewed

    Ishida T., Uehara Y., Iwata T., Cid-Andres A., Asano S., Ikeya T., Osaka K., Ide J., Privaldos O., Jesus I., Peralta E., Triño E., Ko C., Paytan A., Tayasu I., Okuda N.

    Environmental Science and Technology   53 ( 9 )   4707 - 4716   2019.5

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Environmental Science and Technology  

    © 2019 American Chemical Society. Identifying nonpoint phosphorus (P) sources in a watershed is essential for addressing cultural eutrophication and for proposing best-management solutions. The oxygen isotope ratio of phosphate (δ 18 O PO 4 ) can shed light on P sources and P cycling in ecosystems. This is the first assessment of the δ 18 O PO 4 distribution in a whole catchment, namely, the Yasu River Watershed in Japan. The observed δ 18 O PO 4 values in the river water varied spatially from 10.3‰ to 17.6‰. To identify P sources in the watershed, we used an isoscape approach involving a multiple-linear-regression model based on land use and lithological types. We constructed two isoscape models, one using data only from the whole watershed and the other using data from the small tributaries. The model results explain 69% and 96% of the spatial variation in the river water δ 18 O PO 4 . The lower R 2 value for the whole watershed model is attributed to the relatively large travel time for P in the main stream of the lower catchment that can result in cumulative biological P recycling. Isoscape maps and a correlation analysis reveal the relative importance of P loading from paddy fields and bedrock. This work demonstrates the utility of δ 18 O PO 4 isoscape models for assessing nonpoint P sources in watershed ecosystems.

    DOI： 10.1021/acs.est.8b05837

    Scopus

    Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85064746297&origin=inward

  • Nitrogen and oxygen isotope enrichment factors of nitrate at different denitrification rates in an agricultural soil. Reviewed International journal

    Osaka, K., Nakajima, Y., Suzuki, K., Eguchi, S., Katou, H.

    Soil Science and Plant Nutrition   64 ( 5 )   558 - 565   2018.8

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

    DOI： https://doi.org/10.1080/00380768.2018.1504321

  • インドネシアスマトラ島ブンクル州における極小規模金採掘・精錬地区の環境媒体中水銀濃度とそのヒト健康リスク評価, Reviewed

    永淵修, 中澤暦, 井上隆信, Elvince R., 川上智規, 尾坂兼一, 金藤浩司

    環境科学会誌   31 ( 2 )   43 - 58   2018.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • 琵琶湖流入河川流域における森林および農地土壌中のリン含有粒子サイズの違い Reviewed

    長根美和子、尾坂兼一、阿江教治、大園亨司、保原達

    酪農学園大学紀要   41 ( 2 )   147 - 152   2017.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Influence of bedrock groundwater on streamflow characteristics in a volcanic catchment. Reviewed International journal

    4) Fujimoto, M., Ohte, N., Kawasaki, M., Osaka, K., Itoh, M., Ohtsuka, I., Itoh, M.

    Hydrological Processes   2016.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1002/hyp.10558

  • Atmospheric nitrate leached from small forested watersheds during rainfall events: processes and quantitative evaluation Reviewed International journal

    Osaka, K., Kugo, T., Komaki, N., Nakamura, T., Nishida, K., Nagafuchi, O.

    Journal of Geophysical Research   2016.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

    DOI： 10.1002/2015JG003210.

  • Non-carcinogenic risk assessment of groundwater in South Gobi, Mongolia Reviewed International journal

    Nakazawa, K., Nagafuchi, N., Okano, K., Osaka, K., Hamabata, E

    Journal of Water and Health   2016.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

    DOI： https://doi.org/10.2166/wh.2016.035

  • ヒノキ人工林集水域における表面流の発生とそれが集水域からの溶存態窒素流出に与える影響 Reviewed

    久郷達朗、尾坂兼一、川村湧也、永淵修

    陸水研究   2   27 - 37   2015.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

  • 琵琶湖北部の森林流域から流出する硫酸イオンの動態と起源解析 Reviewed

    中澤暦、堀江清悟、永淵修、尾坂兼一、西村拓朗

    陸水学雑誌   76   11 - 23   2015.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Hydrochemical characteristics of the Mongolian plateau and its pollution levels. Reviewed

    Nagafuchi, O., Nakazawa K., Okano, K., Osaka, K., Nishida, Y., Hishida, N.

    INNER ASIA   427 - 441   2014.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • ネパール・カトマンズ盆地における浅層地下水の窒素汚染 Reviewed

    中村高志、西田継、風間ふたば、尾坂兼一、Chapagain, S. K.

    日本水文科学会誌   44 ( 4 )   197 - 206   2014.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan Reviewed

    Tokuchi, N., Ohte, N., Osaka, K., Katsuyama, M.

    Environmental Monitoring and Assessment   185   855 - 863   2013.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Nitrogen availability in the taiga forest ecosystem of northeastern Siberia Reviewed

    Popova, A.S., Tokuchi, N., Ohte, N., Ueda, M.U., Osaka, K., Maximov, T.C., Sugimoto, A.

    Soil Sciene and Plant Nutrition   59 ( 3 )   427 - 441   2013.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • 筑波山周辺の渓流水中の硝酸イオンの酸素・窒素安定同位体比による硝酸イオンの生成・混合・消費プロセスの解析 Reviewed

    高津文人, 渡邊未来, 林誠二, 今井章雄, 中島泰弘, 尾坂兼一, 三浦真吾

    陸水学雑誌   73   1 - 16   2012.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Effects of soil water status on the spatial variation of carbon dioxide, methane and nitrous oxide fluxes in tropical rain-forest soils in Peninsular Malaysia Reviewed

    Itoh, M., Kosugi, Y., Takanashi, S., Kanemitsu, S., Osaka, K., Hayashi, Y., Tani, M., Rahim, A. N.

    Journal of Tropical Ecology   28   1 - 14   2012.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Upward Diffusion of nitrous oxide produced by denitrification near shallow groundwater table in the summer Reviewed

    10) Minamikawa, K., Nishimura, S., Nakajima, Y., Osaka, K., Sawamoto, T., Yagi, K.

    Soil Science and Plant Nutrition   57   719 - 732   2011.10

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Evaluation of Nitrogen, Phosphorus and Carbon Loading by Litters Discharge from a Mountain Watershed Comprises with Japanese Cypress Reviewed

    Osaka, K., Hida, Y., Kunimatsu, T.

    Journal of Ecotechnology Research   16 ( 2 )   33 - 38   2011.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

  • Seasonal fluctuations in growth/decline and single-leaf gas exchange of C3 turfgrass fields under various light conditions. Reviewed

    Matsubara, T., Kosugi. Y., Takanashi, S., Mizota, Y., Itoh, M., Osaka, K., Fujimoto, M., Ohkubo, S.

    Journal of Agricultural Meteorology   67   1 - 12   2011.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • 富士川流域における渓流水中の硝酸イオンの窒素・酸素安定同位体比 Reviewed

    中村高志, 尾坂兼一, 平賀由紀, 風間ふたば

    日本水文科学会誌   41 ( 3 )   79 - 89   2011.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Photosynthesis and respiration of C3 turfgrass fields under various light conditions. Reviewed

    Kosugi, Y., Osaka, K., Itoh, M., Takanashi, S., and Matsubara, T.

    Journal of Agricultural Meteorology   66   163 - 171   2010.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Society of Agricultural Meteorology of Japan   Participation form：Joint(The vice charge)  

  • Spatial distribution of nitrate sources of rivers in the Lake Biwa watershed, Japan: Controlling factors revealed by nitrogen and oxygen isotope values Reviewed

    Ohte, N., Tayasu, I., Kohzu, A., Yoshimizu, C., Osaka, K., Makabe, A., Koba, K., Nagata, T.

    Water Resources Research   46   W07505 - W07505   2010.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • 森林小流域で測定した比流出量の収斂性の検証 Reviewed

    尾坂兼一, 國松孝男, 乙守利樹, 草加伸吾, 駒井幸雄, 浜端悦治, 肥田嘉文, 永淵 修

    水環境学会誌   33 ( 10 )   167 - 174   2010.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本水環境学会   Participation form：Joint(The main charge)  

  • Hydrological influences on spatiotemporal variations of d15N and d18O of nitrate in a forested headwater catchment in central Japan: Denitrification plays a critical role in groundwater Reviewed

    Osaka, K., Ohte, N., Koba, K., Yoshimizu, C., Katsuyama, M., Tani, M., Tayasu, I., Nagata, T.

    Journal of Geophysical Research   115   G02021 - G02021   2010.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

  • Partitioning of respiratory CO2 fluxes in a managed C3 turfgrass field Reviewed

    Kosugi, Y., Itoh, M., Matsubara, M., Takanashi, S., Osaka K., Mizota, Y., Dannoura M., Shimamura, T., Makita, N.

    Journal of Agricultural Meteorology   66   151 - 161   2010.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Biogeochemistry of nitrous oxide in groundwater in a forested ecosystem elucidated by nitrous oxide isotopomer measurements Reviewed

    Koba, K., Osaka, K., Tobari, Y., Toyoda, S.,Ohte, N., Katsuyama, M., Suzuki, N, Itoh M., Yamagishi, H., Kawasaki, M., Kim, S., Yoshida, N. and Nakajima, T.

    Geochimica et Cosmochimica Acta   73   3115 - 3133   2009.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • 深泥池における水質管理に向けた水質の空間分布の把握 Reviewed

    嶋村鉄也, 徳地直子, 尾坂兼一, 伊藤雅之, 大手信人, 竹門康弘

    保全生態学研究   14 ( 2 )   152 - 163   2009.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本生態学会   Participation form：Joint(The vice charge)  

  • ヒノキの植栽された小流域における土壌呼吸速度の時空間分布 Reviewed

    三谷智典, 小杉緑子, 尾坂兼一, 大久保晋治郎, 高梨聡, 谷誠

    日本森林学会誌   88 ( 6 )   496 - 507   2007.4

    　More details

    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本森林学会   Participation form：Joint(The vice charge)  

  • Evaluation of nutrient loads from a mountain forest including storm runoff loads Reviewed

    Kunimatsu, T., Otomori, T., Osaka, K., Hamabata, E., Komai, Y.

    Water Science and Technology   53 ( 2 )   79 - 91   2006.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Spatial distribution of nitrate in Mizoro-ga-ike, a pond with floating mat bog Reviewed

    Advances in Geosciences, Vol. 6: Hydrological Science, World Scientific Co., Pte. Ltd., Singapore   1   129 - 137   2006.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

  • Hydrologic controls on nitrous oxide production and consumption in a forested headwater catchment in central Japan Reviewed

    Journal of Geophysical Research   111   G01013 - G01013   2006.4

    　More details

    Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The main charge)  

▼display all

Books etc

  • 「サンタローザ流域における共通の関心(Boundary Object)」in 流域ガバナンス

    Ria Lambino, 尾坂兼一, 石田卓也, 上原佳敏, Osbert Privaldos (脇田健一, 谷内茂雄, 奥田昇編)（ Role： Contributor）

    京都大学学術出版会  2020.12 

    　More details

    Responsible for pages：第4章-4   Language：Japanese   Book type：Scholarly book

  • Hydrologic controls on the nitrogen dynamics of forested ecosystems investigated using water and nitrate isotope signatures, In: Earth, Life, and Isotopes

    Ohte, N., Tokuchi, N., and Osaka, K., edited by Ohkouch, N, Tayasu, I, Koba, K.（ Role： Joint author）

    Kyoto University Press  2010.4  （ ISBN:978-4-87698-960-7 ）

    　More details

    Total pages：415   Language：English   Book type：Scholarly book

MISC

  • Improvement of analysis for nitrogen and oxygen isotopes of nitrate using denitrifier method: Challenge to reduce methodological blank

    Osaka, K., Nakamura, T., Nishida, K., Kazama, F.

    Annual report 2009,GCOE program   29 - 31   2009.4

    　More details

    Language：English   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：University of Yamanashi   Participation form：Joint(The main charge)  

    Annual report 2009,GCOE program