22 Sep 2023
 | 22 Sep 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

An overview of organic aerosols at an urban site in Hong Kong: insights from in-situ measurement of molecular markers

Hongyong Li, Xiaopu Lyu, Likun Xue, Yunxi Huo, Dawen Yao, Haoxian Lu, and Hai Guo

Abstract. Organic aerosol (OA) is a significant constituent of urban particulate matter (PM), and molecular markers therein provide information on sources and formation mechanisms of OA. With in-situ measurement of over 70 OA molecular markers at a bihourly resolution, this study focused on the temporal variations of representative markers and dynamic source contributions to OA at an urban site in Hong Kong. The levels of secondary OA (SOA) markers were markedly elevated in continental and coastal air, and the primary markers were more of local characteristics. The diurnal patterns of 2-methyltetrols differed between scenarios, and their aqueous formation at night seemed plausible, particularly in the presence of troughs. Seven unambiguous sources were identified for the organic matters in submicron PM (PM1-OM). Despite an urban site, the SOA contribution (49 ± 8 %), primarily anthropogenic, was significant. Anthropogenic SOA dominated in continental and coastal air and in early afternoon. Local cooking and vehicle emissions became predominant in the scenario of marine air without troughs. Even averaged over the study period, cooking emissions contributed up to 40 % to PM1-OM in the early evening. The study highlighted the need to control regional anthropogenic SOA and local cooking emissions to mitigate PM pollution in Hong Kong.

Hongyong Li et al.

Status: open (until 20 Dec 2023)

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  • RC1: 'Comment on egusphere-2023-1835', Anonymous Referee #1, 29 Nov 2023 reply

Hongyong Li et al.


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Short summary
Organic aerosols are ubiquitous in the atmosphere and largely explain the gap between current levels of fine particulate matter in many cities and the World Health Organization guideline values. This study highlights the secondary fraction derived from anthropogenic aromatics and cooking emissions as the leading sources of organic aerosols in the early afternoon and early evening, respectively, in urban Hong Kong. The findings may apply to other densely populated cities.