Experimental study of the impacts of external disturbances on N_2O emission from water to air

摘要

To obtain a comprehensive understanding of nitrous oxide (N_2O) emission from water to air, the impacts of external disturbances including wind, stirring and aeration on N_2O emissions were investigated by continuously monitoring N_2O concentration variations in water. The volumetric mass transfer coefficient of N_2O from water to air (K_(LaN_2O)) under different conditions was determined by using exponential regression to fit the monitoring data. The results showed that K_(LaN_2O) was 0.0017 min~(–1) at the stable condition, and with the increase of wind velocity, stirring velocity and aeration rate, the diffusion of N_2O from water to air was enhanced. It was also observed that K_(LaN_2O) linearly increased with the increase of wind velocity and aeration rate, and exponentially increased with the increase of stirring velocity. The sequencing of the impacts of the three factors on N_2O emission was aeration>stirring >wind. As turbulence and the mixing intensity of the liquid phase under the aeration condition were more vigorous than those of the wind and the stirring, the impact of aeration on N_2O emission was greater than those of wind and stirring. When predicting N_2O emissions from water to air, external disturbances, either environmental factors or operational factors, should be taken into consideration.