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Investigating the Southeast Asian Haze Impacts on Urban Organic Aerosol Composition Using a High-Mass Resolution Spectrometry and Factor Analysis
SRI HAPSARI BUDISULISTIORINI, Katie Balmer, Daniel Bryant, Liudongqing Yang, Jing Chen, Mikinori Kuwata, Jacqueline Hamilton, University of York
Abstract Number: 301
Working Group: Wildfire Aerosols
Abstract
Organic aerosol (OA) is a major component of urban particulate matter. One of the contributing sources to urban OA is biomass burning emission. Recurring peatland fire has caused Southeast Asia countries, including Singapore, blanketed by haze for the last two decades. Studies found oxygenated organic aerosol (OOA) as the dominant OA component during the haze episode and linked it to biomass burning tracers. The limited samples and analysis capabilities hindered further assessing the peatland fires' impact on urban air quality. Hence, we aim to investigate the OA sources in Singapore using a high-mass resolution spectrometer. Intermittent daily samples of particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) were collected from 2018 to 2019, covering clean and haze episodes. The samples were analyzed using liquid chromatography with heated electrospray ionization coupled to a Q-Exactive Orbitrap mass spectrometer. We developed a novel targeted and non-targeted molecular identification to the high-resolution mass spectrometry (HRMS) data. We identified almost 2000 compounds. Moreover, we discovered enhancement of biomass burning markers, including 4-nitrocatechol, 4-hydroxy-3-nitrobenzoic acid, 4-nitro-1-napthol, vanillin, nitroguaiacols, nitrophenols, methyl-nitrophenols, and hydrocinnamic acids, during the haze period compared to the clean period. Interestingly, vanillic acid, methyl-dinitrophenols, and dinitrophenols, previously identified as biomass burning markers, did not display elevated levels during the haze event. Therefore, we applied, for the first time, a positive matrix factorization analysis technique to the identified HRMS compounds to further investigate the OA sources. The results indicate other major OA sources, including traffic and biogenic secondary organic aerosol sources. The hybrid non-targeted HRMS and factor analysis provide detailed OA sources characterization and powerful urban air quality observation tools.