Experimental study of the impacts of external disturbances on N₂O emission from water to air

To obtain a comprehensive understanding of nitrous oxide (N₂O) emission from water to air, the impacts of external disturbances including wind, stirring and aeration on N₂O emissions were investigated by continuously monitoring N₂O concentration variations in water. The volumetric mass transfer coefficient of N₂O from water to air (K_LaN2O) under different conditions was determined by using exponential regression to fit the monitoring data. The results showed that K_LaN2O was 0.0017 min^–1 at the stable condition, and with the increase of wind velocity, stirring velocity and aeration rate, the diffusion of N₂O from water to air was enhanced. It was also observed that K_LaN2O 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 N₂O 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 N₂O emission was greater than those of wind and stirring. When predicting N₂O emissions from water to air, external disturbances, either environmental factors or operational factors, should be taken into consideration.