抄録
Production and degradation of nitrous oxide(N2O) were investigated in agricultural water system consisting of paddy fields, a small river, and the groundwater. In this area, anthropogenie nitrogen, as fertilizer, animal wastes etc., causes the occurrence of high nitrate-nitrogen (20-30mgN·l-1). Denitrification actively occurred and N2O was produced both in the paddy field and the small river receiving organic wastewater. Dissolved N2O concentration in this area ranged from 10 to 400 μgN·l-1, which was much higher than the concentration in the equilibrium with the ambient atmosphere. N2O gas flux from the small river was about 500μgN·m-2·h-1. The conversion from NO3-N to N2O varied from 0.06 to 20.5% depending on season and other circumstances. This suggests that the agricultural water system is potential source of N2O emission.
