Japan Geoscience Union Meeting 2023

Presentation information

[E] Online Poster

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

[A-HW18] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

Thu. May 25, 2023 10:45 AM - 12:15 PM Online Poster Zoom Room (5) (Online Poster)

convener:Takahiro Hosono(Faculty of Advanced Science and Technology, Kumamoto University), Syuhei Ban(The University of Shiga Prefecture), Mitsuyo Saito(Graduate School of Advanced Science and Engineering, Hiroshima University), Adina Paytan(University of California Santa Cruz)


On-site poster schedule(2023/5/26 17:15-18:45)

10:45 AM - 12:15 PM

[AHW18-P09] Impact of Anthropogenic phosphorus loading on authigenic apatite in marine sediment of Osaka Bay

*Muhammad Shahinur Rahman1, Shin-ichi Onodera1, Takuya Ishida1, Mitsuyo Saito1, Kunyang Wang1, Takahiro Hosono2, Yu Umezawa3 (1.Hiroshima University, 2.Kumamoto University, 3.Tokyo University of Agriculture and Technology)

Keywords:Limiting factor, Eutrophication, Urbanized Bay, SEDEX, Phosphorus species

Phosphorus is one of the most important limiting factors for coastal productivity. In recent years, due to the population growth and extensive use of phosphorus derived chemicals like fertilizer creates an enormous problem named eutrophication in many coastal regions along with nitrogen. It is important to know the accumulation and release pattern of phosphorus for better management planning.

This study was performed in Osaka Bay which is an urbanized enclosed bay and one of the most industrial regions of Japan. We analyze phosphorus concentrations in the sediment core of Osaka Bay using the sequential extraction method (SEDEX) for understanding the historical phosphorus loads from watersheds and phosphorus accumulation in the sediment, especially calcium bound authigenic apatite which characteristics is generally non-reactive and important for P accumulation. The 210Pb method was used for determination of the sediment core chronology.
The mean concentration of Ca-P is 99.7 ± 24.4 with a range of 55.7 to 149.9 mg/Kg. The value of Authigenic Apatite has stable since 1920, and a positive trend has seen which apex was after 1960. We also evaluate the relationship between depth distribution of Authigenic Apatite and historical total phosphorus loading from Yamato River estimated by Soil and Water Assessment Tool (SWAT). We divided data on total phosphorus loading into two subsets considering environmental law enforcement. Before 1970 there was less environmental law enforcement in Japan. There was a positive relationship between total phosphorus loading and Authigenic Apatite in 1940-1970 which converted to negative correlation after 1970. We also evaluate the sediment texture pattern and the Authigenic Apatite. We find that the sand percentage has increased comparatively after 1970. We assume sand particles contribute to the increase of Authigenic Apatite during this period.

Acknowledgement: This study supported by Asia-Pacific Network for Global Change Research Project (CRRP2019-09MY-Onodera).