Behavior and seasonal variation of eutrophication substances in the Yodo River system

Abstract

In order to elucidate the behavior and the seasonal variation of eutrophication substances in the Yodo River system, the dissolved inorganic nitrogen compounds, dissolved inorganic phosphate, total dissolved nitrogen (TDN), total dissolved phosphate (TDP) and dissolved organic carbon (DOC) were periodically observed during March 2001 to February 2002. Concentrations of TDN and TDP were near doubled downstream from the confluence of tributaries, the Katsura and Kizu Rivers. However, that of DOC did not increase significantly in the same interval. These results suggested that the nitrogen and phosphorus compounds from the tributaries had much influence on the water pollution of the Yodo River system compared to those of the main stream. The loads per year of TDN, TDP and DOC from the Yodo River to Osaka Bay were calculated to be 8,370, 444 and 11,700 ton/yr, respectively.