Thermodynamic Modeling Suggests Declines in Water Uptake and Acidity of Inorganic Aerosols in Beijing Winter Haze Events during 2014/2015-2018/2019

Shaojie Song, Athanasios Nenes, Meng Gao, Yuzhong Zhang, Pengfei Liu, Jingyuan Shao, Dechao Ye, Weiqi Xu, Lu Lei, Yele Sun, Baoxian Liu*, Shuxiao Wang, Michael B. McElroy

*Corresponding author for this work

    Research output: Contribution to journalJournal articlepeer-review

    59 Citations (Scopus)

    Abstract

    During recent years, aggressive air pollution mitigation measures in northern China have resulted in considerable changes in gas and aerosol chemical composition. But it is unclear whether aerosol water content and acidity respond to these changes. The two parameters have been shown to affect heterogeneous production of winter haze aerosols. Here, we performed thermodynamic equilibrium modeling using chemical and meteorological data observed in urban Beijing for four recent winter seasons and quantified the changes in the mass growth factor and pH of inorganic aerosols. We focused on high relative humidity (>60%) conditions when submicron particles have been shown to be in the liquid state. From 2014/2015 to 2018/2019, the modeled mass growth factor decreased by about 9%-17% due to changes in aerosol compositions (more nitrate and less sulfate and chloride), and the modeled pH increased by about 0.3-0.4 unit mainly due to rising ammonia. A buffer equation is derived from semivolatile ammonia partitioning, which helps understand the sensitivity of pH to meteorological and chemical variables. The findings provide implications for evaluating the potential chemical feedback in secondary aerosol production and the effectiveness of ammonia control as a measure to alleviate winter haze.

    Original languageEnglish
    Pages (from-to)752-760
    Number of pages9
    JournalEnvironmental Science and Technology Letters
    Volume6
    Issue number12
    DOIs
    Publication statusPublished - 10 Dec 2019

    Scopus Subject Areas

    • Environmental Chemistry
    • Ecology
    • Water Science and Technology
    • Waste Management and Disposal
    • Pollution
    • Health, Toxicology and Mutagenesis

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