Production and Degradation of Nitrous Oxide in the Paddy Field and a Small River Contaminated with High Nitrate-nitrogen

Abstract

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 NO_3-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.