印旛沼流入河川における窒素汚染の実態とその要因

抄録

High-concentration nitrogen is observed in influent rivers into Lake Inba-numa. This is one of important factor for prolonged eutrophication in Lake Inba-numa. In this study, we conducted water and sediment sampling at a number of measurement stations in the influent rivers into Lake Inba-numa and analyzed nutrient concentration of river water and stable isotope of sediment. In Takasaki River, the detailed observations and GIS analysis were conducted to clarify the contributing factor of nitrogen pollution. The results indicate that the nutrient concentration in Takasaki River is closely related to the landuse of catchment basin and there is a positive correlation between permeable area in the catchment basin and non-point source of nitrogen, which is derived by subtracting point source from observed nitrogen flux. The contributing rate of groundwater to nitrogen pollution and flow discharge , which was estimated using the unit loading of the permeable area, was found to be 20～84% and 28～74%, respectively.