The Effect of Expansion of the Saturated Soil Zone on NO3--N Concentration in Streamwater During a Rainfall Event.

概要

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The variation of N03--N concentrations in streamwater and in soil solutions on the valley floor was measured during two rainfall events different in total rainfall amount. The 0.52ha catchment located in the Hakyuuchi in Hachiouji City, Tokyo is covered by a broad-leaved forest. By the 109mm rainfall, saturated soil zone expanded to surface soil layer and the N03--N concentration in streamwater increased remarkably. On the other hand, the 44.5mm rainfall kept surface soil layer unsaturated and didn't vary the N03--N concentration in streamwater. These results show that the increase of N03--N concentration in streamwater was caused by saturation of surface soil layer, which was rich in N03--N and had high hydraulic conductivity. Subsuface flow in the surface soil layer was the dominant source of streamwater when it was saturated. Subsuface flow also brings the variation of N03--N concentration in soil solution. This variation occurs by the congruence of concentrations of soil solutions in the direction of subsurface flow.
水文・水資源学会の論文