Investigating the vital influences of multi-factor synergies on the nitrate formations on the surface of nano MgO particles

Abstract

With the fast development of motor vehicle quantities in megacities in recent years, nitrate has become a very important component in atmospheric fine particulate matter, and produced significant impacts on haze formations. In the study, a photochemical smog chamber was used to investigate the impacts of atmospheric pollutants as O3, NH3 and SO2 on nitrate heterogeneous formations on the surfaces of nano MgO particles in the two reaction systems of NO2-MgO-dark and NO2-MgO-hν, and the related formation mechanisms. With dark similar to nighttime, O3 played a key role in the nitrate heterogeneous formations on the surfaces of nano MgO particles, and NH3 and SO2 also promoted the nitrate heterogeneous formations, respectively, presenting an order of O3 > SO2 > NH3. It is noted that the synergies of O3 and SO2 or NH3 were more favorable for the nitrate heterogeneous formations. Besides, the nitrite heterogeneous formations were greatly impacted by NH3 and SO2. With UV light like daytime, the synergies of UV light and O3 greatly promoted the nitrate heterogeneous formations, however, NH3 and SO2 exerted an inhibitory effect on the nitrate heterogeneous formations. The nitrate heterogeneous formation mechanisms on the surfaces of nano MgO particles were strongly impacted by UV light, O3, NH3 and SO2, presenting different reaction mechanisms. The synergistic effects of O3, NH3 and SO2 on the nitrate heterogeneous formations at nighttime were obviously higher than those of UV light, O3, NH3 and SO2 at daytime, implying that nighttime was more favorable for nitrate heterogeneous formations.