Influence of ozone and humidity on the formation of sulfate and nitrate in airborne fine particles

Abstract

Ambient concentrations of HNO3 and SO2, and particulate NO3- and SO4(2-) were simultaneously measured in daytime and nighttime in southern Taiwan, to investigate the conversion effect of these inorganic species into airborne particulate. During the episode days, the average particulate nitrate mass of accumulation mode (0.18-1.8 microm) measured over daytime and nighttime were about 3.9 and 7.6 times higher than those measured during non-episode days, respectively. The mean value of gaseous nitric acid was always higher during episode daytime than that during non-episode daytime. In addition, the SO4(2-) mass of accumulation mode during episode days was about 2.6 and 2.0 times higher than those during the daytime and nighttime of the non-episode days, respectively. Both of (1) the extent of SO2 oxidation to sulfate and NO2 oxidation to nitrate and (2) conversion ratios for sulfur (Fs) and nitrogen (Fn) were defined and calculated using field measurements. The nighttime Fn and Fs during the episode days were about 4 and 1.6 times higher, respectively, than those during the non-episode days. Furthermore, the Fs and Fn increased with the increase of relative humidity during both of the episode daytime and nighttime. A positive correlation coefficient that the Fn and Fs increases with increasing ozone concentration was found during the non-episode daytime. These results might be attributed to high NO2, SO2 and ozone concentrations in a humid atmosphere, and also the fact that the gas-to-particle conversion plays an important role during episode days.

Roles of Sulfur Oxidation Pathways in the Variability in Stable Sulfur Isotopic Composition of Sulfate Aerosols at an Urban Site in Beijing, China

“…SOR is the formation ratio of SO 2 to sulfate, and ambient temperature and RH significantly influence sulfate formation during the different processes. 45,46 Consequently, significant correlation between δ 34 S-SO 4 2− and the aforementioned parameters might also suggest that the δ 34 S values of sulfate were dependent on the different SO 2 oxidation processes.…”

“…In addition, the significant correlation between δ 34 S and RH might suggest that isotope fractionation occurred in aqueous-phase oxidation of SO 2 to sulfate formation. SOR is the formation ratio of SO 2 to sulfate, and ambient temperature and RH significantly influence sulfate formation during the different processes. , Consequently, significant correlation between δ 34 S-SO 4 2– and the aforementioned parameters might also suggest that the δ 34 S values of sulfate were dependent on the different SO 2 oxidation processes.…”

Attributions of meteorological and emission factors to the 2015 winter severe haze pollution episodes in China's Jing-Jin-Ji area

“…Because of the WSCL shift, the increase in RH in Shijiazhuang was slightly larger than in Beijing, at about 32 %. Researchers (Chang et al, 2009) have shown that the extent of SO 2 oxidation to sulfate and NO 2 oxidation to nitrate increased with the increase of relative humidity during two episodes of daytime and nighttime pollution in Taiwan. Gund et al (1991) found that the oxidation rate of SO 2 to sulfate would increase by about 10 times if the relative humidity increased from 40 to 80 % T. Liu et al: Attributions of meteorological and emission factors in sea-salt aerosols.…”

Haze pollution in winter and summer in Zibo, a heavily industrialized city neighboring the Jin-Jin-Ji area of China: source, formation, and implications

“…In summer ( Figure 3 (b)), nitrate increased significantly from non-haze days (4.4%) to haze days (15.3%), indicating the important role of nitrate in the evolution of pollution. The approximately three-times increase may be caused by the higher concentration of ammonium, higher RH, more intensive photochemical reactivity (high O3), and higher concentration of NO2 (Chang et al, 2009;Lin and Cheng, 2007). A detailed discussion of its formation mechanisms is provided later.…”