OSAKA Kenichi




Research Fields, Keywords

Forest Hydrology, Biogeochemistry

Graduating School 【 display / non-display

  • The University of Shiga Prefecture  2002.03

Graduate School 【 display / non-display

  • Kyoto University  Graduate School, Division of Agriculture  Doctor's Course  2007.03

Campus Career 【 display / non-display

  • University of Shiga Prefecture  School of Environmental Science  Department of Ecosystemus Studies  Lecturer   2019.04 - Now

  • University of Shiga Prefecture  School of Environmental Science  Department of Ecosystemus Studies  Assistant Professor   2010.08 - 2019.03

Field of expertise (Grants-in-aid for Scientific Research classification) 【 display / non-display

  • Environmental dynamic analysis


Papers 【 display / non-display

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

    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  Environmental Science and Technology  53 (9)   4707 - 4716  2019.05

    10.1021/acs.est.8b05837  Joint Work  


    © 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.

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

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

     Soil Science and Plant Nutrition  64 (5)   558 - 565  2018.08  Joint Work  Joint(The main charge)

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

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

     Hydrological Processes    2016.04

    DOI: 10.1002/hyp.10558  Single Work  

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

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

      Journal of Water and Health    2016.04

    wh2016035  Joint Work  Joint(The vice charge)

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

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

     Journal of Geophysical Research    2016.04

    10.1002/2015JG003210.  Joint Work  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


     陸水学雑誌  76   11 - 23  2015.04

    Joint Work  Joint(The vice charge)

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

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

     INNER ASIA   427 - 441  2014.04

    Joint Work  Joint(The vice charge)

  • Nitrogen availability in the taiga forest ecosystem of northeastern Siberia

    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  2013.04

    Joint Work  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

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

     Environmental Monitoring and Assessment  185   855 - 863  2013.04

    Joint Work  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

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

     Journal of Tropical Ecology  28   1 - 14  2012.04

    Joint Work  Joint(The vice charge)

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Books 【 display / non-display

  • 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.

    Kyoto University Press  415p  2010.04

    Scholarly Book  Joint Work

Review Papers 【 display / non-display

  • 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.

    University of Yamanashi  Annual report 2009,GCOE program   29 - 31  2009.04

     Joint Work  Joint(The main charge)