Sources of secondary organic aerosols in the Pearl River Delta region in fall: Contributions from the aqueous reactive uptake of dicarbonyls

Nan Li, Tzung May Fu, Junji Cao, Shuncheng Lee, Xiao Feng Huang, Ling Yan He, Kin Fai Ho, Joshua S. Fu, Yun Fat Lam

Research output: Journal article publicationJournal articleAcademic researchpeer-review

35 Citations (Scopus)

Abstract

We used the regional air quality model CMAQ to simulate organic aerosol (OA) concentrations over the Pearl River Delta region (PRD) and compared model results to measurements. Our goals were (1) to evaluate the potential contribution of the aqueous reactive uptake of dicarbonyls (glyoxal and methylglyoxal) as a source of secondary organic aerosol (SOA) in an urban environment, and (2) to quantify the sources of SOA in the PRD in fall. We improved the representation of dicarbonyl gas phase chemistry in CMAQ, as well as added SOA formation via the irreversible uptake of dicarbonyls by aqueous aerosols and cloud droplets, characterized by a reactive uptake coefficient γ=2.9×10-3based on laboratory studies. Our model results were compared to aerosol mass spectrometry (AMS) measurements in Shenzhen during a photochemical smog event in fall 2009. Including the new dicarbonyl SOA source in CMAQ led to an increase in the simulated mean SOA concentration at the sampling site from 4.1μgm-3to 9.0μgm-3duringthe smog event, in better agreement with the mean observed oxygenated OA (OOA) concentration (8.0μgm-3). The simulated SOA reproduced the variability of observed OOA (r=0.89). Moreover, simulated dicarbonyl SOA was highly correlated with simulated sulfate (r=0.72), consistent with the observed high correlation between OOA and sulfate (r=0.84). Including the dicarbonyl SOA source also increased the mean simulated concentrations of total OA from 8.2μgm-3to 13.1μgm-3, closer to the mean observed OA concentration (16.5μgm-3). The remaining difference between the observed and simulated OA was largely due to impacts from episodic biomass burning emissions, but the model did not capture this variability. We concluded that, for the PRD in fall and outside of major biomass burning events, 75% of the total SOA was biogenic. Isoprene was the most important precursor, accounting for 41% of the total SOA. Aromatics accounted for 13% of the total SOA. Our results show that the aqueous chemistry of dicarbonyls can be an important SOA source, potentially accounting for 53% of the total surface SOA in the PRD in fall.
Original languageEnglish
Pages (from-to)200-207
Number of pages8
JournalAtmospheric Environment
Volume76
DOIs
Publication statusPublished - 1 Sep 2013

Keywords

  • CMAQ
  • Glyoxal
  • Methylglyoxal
  • Pearl River Delta (PRD)
  • Secondary organic aerosol

ASJC Scopus subject areas

  • Environmental Science(all)
  • Atmospheric Science

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