Characterization of carbonaceous aerosols in Singapore: insight from black carbon fragments and trace metal ions detected by a soot particle aerosol mass spectrometer

Rivellini, Laura-Hélèna; Adam, Max Gerrit; Kasthuriarachchi, Nethmi; Lee, Alex King Yin

Understanding sources and atmospheric processes that can influence the physiochemical properties of carbonaceous aerosols is essential to evaluate their impacts on air quality and climate. However, resolving the sources, emission characteristics, and aging processes of carbonaceous aerosols in complex urban environments remains challenging. In this work, a soot particle aerosol mass spectrometer (SP-AMS) was deployed to characterize organic aerosols (OAs), refractory black carbon (rBC), and trace metals in Singapore, a highly urbanized city with multiple local and regional air pollution sources in the tropical region. rBC (inline-formula M1inlinescrollmathml chem normal C normal 1 + 16pt15ptsvg-formulamathimg472eb161d64b68a231d325ff11f4c3a5 acp-20-5977-2020-ie00001.svg16pt15ptacp-20-5977-2020-ie00001.png inline-formula M2inlinescrollmathml chem normal C normal 9 + 16pt15ptsvg-formulamathimg8af7b9817e69df4fd53090a915849774 acp-20-5977-2020-ie00002.svg16pt15ptacp-20-5977-2020-ie00002.png ) fragments and trace metal ions (inline-formulaK+, inline-formulaNa+, inline-formulaNi+, inline-formulaV+, and inline-formulaRb+) were integrated into our positive matrix factorization of OA. Two types of fossil fuel combustion-related OAs with different degrees of oxygenation were identified. This work provides evidence that over 90 % of rBC originated from local combustion sources with a major part related to traffic and inline-formula∼30 % associated with fresh secondary organic aerosol (SOA) produced under the influence of shipping and industrial emission activities (e.g., refineries and petrochemical plants) during daytime. The results also show that inline-formula∼43 % of the total rBC was emitted from local traffic, while the rest of the rBC fraction stemmed from multiple sources including vehicular sources, shipping, and industrial emissions, but was not fully resolved. There was only a weak association of the cooking-related OA component with rBC. Although there was no observable biomass burning episode during the sampling period, inline-formulaK+ and inline-formulaRb+ were mainly associated with the more oxidized oxygenated OA component, indicating the potential contribution of regional biomass burning and/or coal combustion emissions to this aged OA component. Furthermore, the aerosol pollutants transported from the industrial area and shipping ports presented higher inline-formula M12inlinescrollmathml chem normal C normal 1 + / normal C normal 3 + 36pt15ptsvg-formulamathimgaeff7c7aa7fbabf3ed61ae9da0262ad8 acp-20-5977-2020-ie00003.svg36pt15ptacp-20-5977-2020-ie00003.png and inline-formula M13inlinescrollmathml chem normal V + / normal Ni + 38pt14ptsvg-formulamathimg03c39fb5ab0d7aa899626939f16010da acp-20-5977-2020-ie00004.svg38pt14ptacp-20-5977-2020-ie00004.png ratios than those associated with traffic. The observed association between inline-formulaNa+ and rBC suggests that the contribution of anthropogenic emissions to total particulate sodium should not be ignored in coastal urban environments. Overall, this work demonstrates that rBC fragments and trace metal ions can improve our understanding of the sources, emission characteristics, and aging history of carbonaceous aerosol (OA and rBC) in this type of complex urban environment.

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Rivellini, Laura-Hélèna / Adam, Max Gerrit / Kasthuriarachchi, Nethmi / et al: Characterization of carbonaceous aerosols in Singapore: insight from black carbon fragments and trace metal ions detected by a soot particle aerosol mass spectrometer. 2020. Copernicus Publications.

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