[A-HW22] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW22-P04] Temporal variation in phosphorous fractionation of suspended sediment from 2022 to 2023 in Yamato River

*Wanna Zaw¹, Shin-ichi Onodera¹, Mitsuyo Saito¹, Sharon Bih Kimbi¹, Takuya Ishida¹, Muhammad Shahinur Rahman¹ (1.Graduate School of advanced science and Engineering )

Keywords:Phosphorus concentration, speciation , hydrological control

Phosphorus (P) is important as an essential nutrient for aquatic ecosystems. On the other hand, excess P loading has the potential to cause environmental problems such as eutrophication of surface water. The bioavailability of P is related to all fractions of P. Therefore, it is important to understand the dynamics of different fractions of P exported from river basins to coastal. Additionally, land use patterns and hydrological conditions greatly influence on P exports from river basins. In our target catchment, Yamato River in Osaka, an environmental issue occurred in around 1970, when the population and the industrial areas immediately increased. We aimed to examine the chemical fractions of particulate phosphorus (PP) exported from the Yamato River during the different hydrological conditions. In this study, the sequential extraction method was used to extract the P fraction such as Ex-P, Fe-P, Ca-P, and Det-P, and measured the concentration of the total phosphorus (TP), total particulate phosphorus (TPP), particulate inorganic phosphorus (PIP), soluble reactive phosphorus (SRP), and calculate the total dissolved phosphorus (TDP), particulate organic phosphorus (POP) and non-reactive phosphorus (NRP). TP was highest in May with higher precipitation and river water levels, when agricultural activity also started during the period. TPP is higher than TDP during the period with higher precipitation and water levels. For the fraction of P, Iron-bound phosphorus (Fe-P) is the dominant P fraction, particularly from late March to late October in the Yamato River catchment.
Acknowledgement: This study is supported by Asia-Pacific Network for Global Change Research Project (CRRP2019-09MY-Onodera) and Grant for Environmental Rehabilitation and Creation of the Osaka Bay Area (PI: Mitsuyo Saito, Grant Number: 040006, 2022).