5:15 PM - 6:30 PM
[ACG23-P03] Dynamics of dissolved inorganic nitrogen and phosphorous of the river water in the Kunisaki Peninsula in summer
Keywords:Nutrients, stream water, agricultural land, forest, GIAHS
Concentrations of DIN, DIP and d-excess of water isotopes ranged from 6.3 to 153.4 μM, from 0.1 to 4.1 μM and from 8.9 to 15.5, respectively. Fluxes of DIN and DIP from each watershed to coastal regions ranged from 0.8 to 140 kg d-1, and from 0.2 to 22 kg d-1, respectively. Although the fluxes were mainly dominated by river discharge, the molar ratio of DIN and DIP (DIN/DIP) varied from 6 to 39. We found positive exponential relationship between DIN/DIP and d-excess. These results suggests that unique water use system affected the difference in DIN and DIP dynamics within the watershed, since a number of ponds increased d-excess values from upstream to downstream. Moreover, in the Kunisaki Peninsula, the forest supplied DIN to the river, while DIP was mainly supplied from the agricultural land.
Therefore, higher d-excess and DIN/DIP showed lower retention time and larger impacts of forest. On the other hand, lower d-excess and DIN/DIP showed higher retention time and larger impacts of agricultural land.