Atmospheric fate of peroxyacetyl nitrate in suburban Hong Kong and its impact on local ozone pollution

Lewei Zeng, Gang-Jie Fan, Xiaopu Lyu, Hai Guo*, Jia-Lin Wang, Dawen Yao

*Corresponding author for this work

    Research output: Contribution to journalJournal articlepeer-review

    38 Citations (Scopus)

    Abstract

    Peroxyacetyl nitrate (PAN) is an important reservoir ofatmospheric nitrogen, modulating reactive nitrogen cycle and ozone (O3)formation. To understand the origins of PAN, a field measurement was conductedat Tung Chung site (TC) in suburban Hong Kong from October to November 2016.The average level of PAN was 0.63 ± 0.05 ppbv, with a maximum of 7.30 ppbv.Higher PAN/O3 ratio (0.043–0.058) was captured on episodes, i.e. when hourly maximum O3exceeded 80 ppbv, than on non-episodes (0.01), since O3 productionwas less efficient than PAN when there was an elevation of precursors (i.e. volatile organic compounds(VOCs) and nitrogen oxide (NOx)). Model simulations revealed thatoxidations of acetaldehyde (65.3 ± 2.3%), methylglyoxal (MGLY, 12.7 ± 1.2%) andother oxygenated VOCs (OVOCs) (8.0 ± 0.6%), and radical cycling (12.2 ± 0.8%)were the major production pathways of peroxyacetyl (PA) radical, while localPAN formation was controlled by both VOCs and nitrogen dioxide (NO2).Among all VOC species, carbonyls made the highest contribution (59%) to PANformation, followed by aromatics (26%) and biogenic VOCs (BVOCs) (10%) throughdirect oxidation/decomposition. Besides, active VOCs (i.e. carbonyls, aromatics, BVOCsand alkenes/alkynes) could stimulate hydroxyl (OH) production, thus indirectlyfacilitating the PAN formation. Apart from primary emissions, carbonyls werealso generated from oxidation of first-generation precursors, i.e., hydrocarbons, of whichxylenes contributed the most to PAN production. Furthermore, PAN formationsuppressed local O3 formation at a rate of 2.84 ppbv/ppbv, when NO2,OH and hydroperoxy (HO2) levels decreased and nitrogen monoxide (NO)value enhanced. Namely, O3 was reduced by 2.84 ppbv per ppbv PANformation. Net O3 production rate was weakened (∼36%)due to PAN photochemistry, so as each individual production and loss pathway.The findings advanced our knowledge of atmospheric PAN and its impact on O3production.

    Original languageEnglish
    Pages (from-to)1910-1919
    Number of pages10
    JournalEnvironmental Pollution
    Volume252
    Issue numberPart B
    Early online date6 Jun 2019
    DOIs
    Publication statusPublished - Sept 2019

    Scopus Subject Areas

    • Toxicology
    • Pollution
    • Health, Toxicology and Mutagenesis

    User-Defined Keywords

    • Formation pathways
    • Master chemical mechanism (MCM)
    • O formation
    • Photochemical smog
    • Precursors

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