Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS13] Biogeochemistry

Mon. May 27, 2019 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Keisuke Koba(Center for Ecological Research, Kyoto University), Hideaki Shibata(Field Science Center fot Northern Biosphere, Hokkaido University), Naohiko Ohkouchi(Japan Agency for Marine-Earth Science and Technology), Youhei Yamashita(Faculty of Environmental Earth Science, Hokkaido University)

[MIS13-P05] Estimation of the formation and reduction of organic mud in tidal river using sulfate ionic flux and principal component analysis

Hiroki Itamura1, *Yoriko Yokoo1 (1.Faculty of Science and Engineering, Doshisha University)

Keywords:tidal river, sulfate flux, principal component analysis, organic mud

We determined the elemental compositions of river water and pore water in order to estimate the sites where the formation and reduction of organic mud occur in delta rivers using the principal component analysis. We collected river water and bed sediment samples at river mouth with tidal intrusion in Ota River, Hiroshima prefecture, and analyze the elemental concentrations using IC and ICP-MS.
We calculated major cations and SO42- flux (JSO4). There was positive correlation between JCa and JSO4. At the sites where their JSO4 showed negative values, JSO4 had strongly positive correlation to JCa. These results demonstrate that SO42- concentrations in pore water decreased and JSO4 showed negative values due to the reduction of SO42-, therefore, the formation and reduction of organic mud could occur at those sites and SO42- has same behavior to Ca2+. We conducted the principal component analysis using eight factors such as JCa, JSO4, water content, porosity, salinity, pH of pore water and concentration of Mn and Fe in pore water for the sites where their JSO4 showed negative values. The first principal component loadings of Fe and Mn concentrations, JCa, JSO4 and porosity were positive and the second principal component loadings of water content, pH, JSO4, and JCa were negative, indicating that the first and second principal component are the index of redox and the formation of organic mud, respectively. The reduction of organic mud could occur at sites plotted in the range of the negative first principal component loadings and the positive second principal component loadings.