Japan Geoscience Union Meeting 2015

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW27] Water and material transport and cycle in watersheds: from headwater to coastal area

Sun. May 24, 2015 2:15 PM - 4:00 PM 301B (3F)

Convener:*Shinji Nakaya(Department of Civil Engineering, Faculty of Engineering, Shinshu University), Mitsuyo Saito(Graduate School of Environmental and Life Science, Okayama University), Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University), Kazuhisa Chikita(Department of Natural History Sciences, Faculty of Science, Hokkaido University), Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Masahiro Kobayashi(Forestry and Forest Products Research Institute), Seiko Yoshikawa(Narional Institute for Agro-Environmental Sciences), Noboru Okuda(Research Institute for Humanity and Nature), Chair:Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University)

3:45 PM - 4:00 PM

[AHW27-21] Phosphate oxygen isotope analysis to study phosphorous cycling

*Noboru OKUDA1, Abigail Cid1, Ichiro TAYASU1, Jun-ichiro IDE2 (1.Research Institute for Humanity & Nature, 2.Institute of Decision Science for a Sustainable Society, Kyusyu University)

Keywords:Temperature-dependent isotope exchange equilibrium, Kinetic isotope fractionation, Thermal conversion/elemental analyzer, Pyrophosphatase, Phosphate oxygen isotope ratio

Phosphorus (P), which is an essential element for all of life on the earth, often limits the productivity of aquatic ecosystems, especially of freshwater ecosystems, because of its scarcity relative to other macronutrients. In modern society, anthropogenic P loadings have caused serious eutrophication and deteriorated ecosystem services all over the world, stimulating social needs for studies on P cycling. Although identification of the primary P sources can provide useful information for designing the best ecosystem management practices to control eutrophication, standard methods have not yet been established because P-involved chemical processes are complicated and P has only one stable isotope, therefore, P isotope ratio is not available as natural tracers. With traditional P transport models, for instance, we have difficulty in estimating the relative contribution of P loadings from a variety of sources. Recently, however, a new isotopic technique has been developed to measure oxygen isotope ratio of dissolved inorganic phosphate (δ18OP), which distinguishes different phosphate sources and also reflects the degree of phosphate turnover by organisms. Here we apply this isotopic technique to identify natural and anthropogenic P sources and evaluate its relative importance to biological P recycling in a watershed ecosystem.