Effects of NO2 and SO2 on the heterogeneous reaction of acetic acid on α-Al2O3 in the presence and the absence of simulated irradiation
The effects of NO2 and SO2 on the atmospheric heterogeneous reaction of acetic acid on α-Al2O3 in the presence and absence of simulated irradiation were investigated at ambient conditions by using the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique. The experiment was divided into two parts: the heterogeneous reaction experiment and the pre-adsorption reaction experiment under light and dark conditions. In the heterogeneous reaction experiment, solar radiation stimulates the formation of more acetate and nitrate. At the same time, it can promote the partial conversion of sulfites to sulfates in the heterogeneous reaction of SO2 on α-Al2O3 particles. It can be seen that solar radiation plays a significant role in the heterogeneous reactions of inorganic and organic gases on mineral particles. In the pre-adsorption reaction experiment, the pre-adsorbed nitrate, sulfite or sulfate have conspicuous inhibition influence on the formation of acetate in the presence and absence of simulated irradiation. This indicates that the role of pre-adsorbed species should be given more attention for the heterogeneous reaction of acetic acid on the surface of α-Al2O3 particles. When α-Al2O3 particles were pre-adsorbed by different species, simulated irradiation could facilitate the growth of different amount of acetate. It was found that the extent to which solar radiation contributes to heterogeneous reactions of different kinds of gases on different mineral particles is different. This further emphasizes the complexities of the heterogeneous conversion processes of atmospheric trace gases on the surface of mineral aerosols, promoting a better understanding of the effects of solar radiation and pre-adsorption on the heterogeneous reaction in the atmosphere.