Browsing by Subject "OZONE PRODUCTION"

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  • Tham, Yee Jun; Wang, Zhe; Li, Qinyi; Wang, Weihao; Wang, Xinfeng; Lu, Keding; Ma, Nan; Yan, Chao; Kecorius, Simonas; Wiedensohler, Alfred; Zhang, Yuanhang; Wang, Tao (2018)
    Heterogeneous uptake of dinitrogen pentoxide (N2O5) and production of nitryl chloride (ClNO2) are important nocturnal atmospheric processes that have significant implications for the production of secondary pollutants. However, the understanding of N2O5 uptake processes and ClNO2 production remains limited, especially in China. This study presents a field investigation of the N2O5 heterogeneous uptake coefficient (gamma (N2O5)) and ClNO2 production yield (phi) in a polluted area of northern China during the summer of 2014. The N2O5 uptake coefficient and ClNO2 yield were estimated by using the simultaneously measured ClNO2 and total nitrate in 10 selected cases, which have concurrent increases in the ClNO2 and nitrate concentrations and relatively stable environmental conditions. The determined gamma (N2O5) and phi values varied greatly, with an average of 0.022 for gamma (N2O5) (+/- 0.012, standard deviation) and 0.34 for (15 (+/- 0.28, standard deviation). The variations in gamma (N2O5) could not be fully explained by the previously derived parameterizations of N2O5 uptake that consider nitrate, chloride, and the organic coating. Heterogeneous uptake of N2O5 was found to have a strong positive dependence on the relative humidity and aerosol water content. This result suggests that the heterogeneous uptake of N2O5 in Wangdu is governed mainly by the amount of water in the aerosol, and is strongly water limited, which is different from most of the field observations in the US and Europe. The ClNO2 yield estimated from the parameterization was also overestimated comparing to that derived from the observation. The observation-derived phi showed a decreasing trend with an increasing ratio of acetonitrile to carbon monoxide, an indicator of biomass burning emissions, which suggests a possible suppressive effect on the production yield of ClNO2 in the plumes influenced by biomass burning in this region. The findings of this study illustrate the need to improve our understanding and to parameterize the key factors for gamma (N(2)O5) and phi to accurately assess photochemical and haze pollution.
  • Yang, Yuan; Wang, Yonghong; Yao, Dan; Zhao, Shuman; Yang, Shuanghong; Ji, Dongsheng; Sun, Jie; Wang, Yinghong; Liu, Zirui; Hu, Bo; Zhang, Renjian; Wang, Yuesi (2020)
    To what extent anthropogenic emissions could influence volatile organic compound (VOCs) concentrations and related atmospheric reactivity is still poorly understood. China's 70th National Day holidays, during which anthropogenic emissions were significantly reduced to ensure good air quality on Anniversary Day, provides a unique opportunity to investigate these processes. Atmospheric oxidation capacity (AOC), OH reactivity, secondary transformation, O-3 formation and VOCs-PM2.5 sensitivity are evaluated based on parameterization methods and simultaneous measurements of VOCs, O-3, NOx, CO, SO2, PM2.5, JO(1)D, JNO(2), JNO(3) carried out at a suburban site between Beijing and Tianjin before, during, and after the National Day holiday 2019. During the National Day holidays, the AOC, OH reactivity, O-3 formation potential (OFP) and secondary organic aerosol formation potential (SOAP) were 1.6 x 10(7) molecules cm(-3) s(-1), 41.8 s(-1), 299.2 mg cm(-3) and 1471.8 mg cm(-3), respectively, which were 42%, 29%, 47% and 42% lower than pre-National Day values and -12%, 42%, 36% and 42% lower than post-National Day values, respectively. Reactions involving OH radicals dominated the AOC during the day, but OH radicals and O-3 reactions at night. Alkanes (the degree of unsaturation = 0, (D, Equation (1)) accounted for the largest contributions to the total VOCs concentration, oxygenated VOCs (OVOCs; D