JpGU-AGU Joint Meeting 2020

Presentation information

[J] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS25] Biogeochemistry

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)

[MIS25-P07] Geological, anthropogenic and tidal effects for stream water chemistry of the Yoshinogawa river systems in the Shikoku region

*Yoriko Yokoo1, Saki Nagayama1, Tomohiro Yoshida1, Ryo Anma2 (1.Faculty of Science and Engineering, Doshisha University, 2.Graduate School of Technology, Industrial and Social Sciences, Tokushima University)

Keywords:Yoshinogawa river, ionic composition, tidal effect

We determined the elemental compositions of stream water of the Yoshinogawa river systems in the Shikoku region. The main stream water, except for samples around the mouth, were enriched in Ca2+and HCO3-. The tributaries on the right side of the Yoshinogawa river were enriched in Ca2+and HCO3- and Ca2+, Mg2+and HCO3-. The river water were rich in Mg2+and Si in Sonosegawa, indicating that these ionic compositions are derived mainly from geological inputs from the weathering of green schist in Sanbagawa Belt. On the other hand, the tributaries on the left side of the Yoshinogawa river were rich in Ca2+, HCO3-and SO42-. The rates of SO42- and NO3-in anions and the concentrations of Al, P, and Si were higher in Imagirigawa and Kyuyoshinogawa than those of the other tributaries. This ionic composition is largely attributable to anthropogenic effect.

The main stream and tributaries around the mouth were enrich in Na+and Cl-. Tidal effect was shown in this area. Na+and Cl- concentrations of tributaries in the center of Tokushima city were higher than those of main stream of the Yoshinogawa river. This result shows that tributaries in the center of Tokushima city are more influenced by tide than main stream. Tamiyagawa, located at the farthest site from the mouth in the center of Tokushima city, had high EC and P, SO42- and NO3- concentrations. This result is largely attributable to anthropogenic effect due to sewage treatment system.