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Organic aerosol (OA) is a significant constituent of urban particulate matter (PM), and molecular markers therein provide information on the sources and formation mechanisms. With the in situ measurement of over 70 OA molecular markers in a summer month at a bihourly resolution, this study focused on the temporal variations in representative markers and dynamic source contributions to OA at an urban site in Hong Kong SAR (HK). The levels of secondary OA (SOA) markers were markedly elevated (p < 0.05) in the short-duration cases with continental and coastal air relative to those in the most common marine air, and the primary markers primarily contained local characteristics. The troughs showed the enhancements of many SOA markers (p < 0.05), which appeared to be related to the high relative humidity. The diurnal patterns of 2-methyltetrols varied in differed cases, and their aqueous formation at night seemed plausible, particularly in the presence of troughs. Eight sources were identified for the organic matter in submicron PM (PM1 -OM). Despite being an urban site, the mean SOA contribution (66.1 ± 10.5 %), primarily anthropogenic, was significant. Anthropogenic SOA dominated in the cases with continental and coastal air and in the early afternoon. Local cooking and vehicle emissions became predominant in the case of marine air without troughs. Even averaged over the study period in this summer month with the prevalence of marine air, primary cooking emissions contributed up to 44.2 % 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 HK. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]