Effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events

• Published in: Atmospheric environment (1994) 2015-12, Vol.122 (C), p.306-312
• Main Authors: Quan, Jiannong, Liu, Quan, Li, Xia, Gao, Yang, Jia, Xingcan, Sheng, Jiujiang, Liu, Yangang
• Format: Article
• Language: English
• Subjects: Beijing hazes; ENVIRONMENTAL SCIENCES; Heterogeneous aqueous reactions; Inorganic aerosol; Particles size
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2015.09.068

The effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events was investigated by analysis of comprehensive measurements of aerosol composition and concentrations [e.g., particular matters (PM2.5), nitrate (NO3), sulfate (SO4), ammonium (NH4)], gas-phase precursors [e.g., nitrogen oxides (NOx), sulfur dioxide (SO2), and ozone (O3)], and relevant meteorological parameters [e.g., visibility and relative humidity (RH)]. The measurements were conducted in Beijing, China from Sep. 07, 2012 to Jan. 16, 2013. The results show that the conversion ratios of N from NOx to nitrate (Nratio) and S from SO2 to sulfate (Sratio) both significantly increased in haze events, suggesting enhanced conversions from NOx and SO2 to their corresponding particle phases in the late haze period. Further analysis shows that Nratio and Sratio increased with increasing RH, with Nratio and Sratio being only 0.04 and 0.03, respectively, when RH < 40%, and increasing up to 0.16 and 0.12 when RH reached 60–80%, respectively. The enhanced conversion ratios of N and S in the late haze period is likely due to heterogeneous aqueous reactions, because solar radiation and thus the photochemical capacity are reduced by the increases in aerosols and RH. This point was further affirmed by the relationships of Nratio and Sratio to O3: the conversion ratios increase with decreasing O3 concentration when O3 concentration is lower than