Characteristics of Nitrogen Outflow from Mountain Area in the Northwest of KantoPlain

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The runoff characteristics of NO_3-N in forested mountain areas located in the northwest of Kanto Plain is investigated by field observation from 2001. The observation consists of two components, one is NO_3-N concentration in mountain stream water and the other is vertical profile of NO_3-N concentration in soil water. It is clarified that the large difference of NO_3-N concentration in mountain stream water exists between the west side and the east side of Tone River. Though NO_3-N concentration in soil water shows the almost similar tendency, vertical profile shows three types that do not exactly correspond to the areal distribution of concentration. By the correlation analysis, there is positive correlation between rainfall events and increase of NO_3-N concentration in mountain stream water in the east side of Tone River, where the concentration is low. On the contrary, no correlation is found out in the west side of Tone River, where the concentration is high. These phenomena correspond to the nitrogen saturation