Heterogeneous reaction of Cl2 and NO2 on γ-Al2O3: A potential formation pathway of secondary aerosols. (September 2018)

• Record Type: Journal Article
• Authors: Tang, Siqun; Ma, Lingling; Luo, Min; Zhang, Zhaohui; Cao, Xingzhong; Huang, Zhenling; Xia, Rui; Qiu, Ye; Feng, Shuo; Zhang, Peng; Xia, Chuanqin; Jin, Yongdong; Xu, Diandou
• Is Part Of: Atmospheric environment. Volume 188(2018)
• Page Start: 25
• Page End: 33
• Publication Date: 2018-09
• Subjects: Cl2 -- NO2 -- Secondary inorganic aerosols -- Heterogeneous reaction -- Positron annihilation lifetime spectroscopy; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.06.005
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: The importance of the oxidizing capacity of reactive chlorine species, and the heterogeneous reactions of atmospheric pollution gases on the surface of particles has been well established in field observation, modeling simulation and laboratory exploration. However, less is known about the reactions of reactive chlorine on mineral particles. We studied the effect of Cl2 on the heterogeneous reaction of NO2 with γ-Al2 O3 by using ion chromatography and positron annihilation lifetime spectroscopy. The presence of Cl2 can promote the uptake of NO2 on γ-Al2 O3 at humid conditions. The probable explanations are that Cl2 rapidly reacts with NO2 on the γ-Al2 O3 surface in the presence of adsorbed water, and nitrites, as the intermediate products during the heterogeneous reaction of NO2 on mineral dust, are immediately oxidized by adsorbed Cl2 . In the positron annihilation lifetime spectroscopy experiment, a porous γ-Al2 O3 was demonstrated by the relatively high fourth lifetime intensity. The increase in the number of anions (onto γ-Al2 O3 ) when the reaction time was prolonged was a direct consequence of the decrease in the o -Ps intensity and the o -Ps lifetime, which illustrated that the heterogeneous reactions might occur on the porous surface of γ-Al2 O3 . Our results suggest that the oxidative effect of Cl2 on the heterogeneous conversion of NO2 to nitrogen-containing particles might have a significant contribution to the fine particle growth and to the unknown sources of nitrate observed in secondary inorganic aerosols. Graphical abstract: Image 1 Highlights: The formation of nitrites is obvious during the reaction of NO2 and Cl2 on γ-Al2 O3 surface by IC. Nitrites increases with the increase of Cl2 concentration on γ-Al2 O3 during exposure to NO2 and Cl2 -poor conditions. Nitrites are entirely oxidized to nitrates on γ-Al2 O3 during exposure to NO2 and Cl2 -rich conditions. Positron annihilation lifetime spectroscopy shows that the heterogeneous reactions occur at the pore surface. The possible heterogeneous reaction mechanism of Cl2 and NO2 on γ-Al2 O3 surface are proposed.