Single-particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium

Atmospheric Chemistry and Physics. 2016;16(9):5561-5572 DOI 10.5194/acp-16-5561-2016

 

Journal Homepage

Journal Title: Atmospheric Chemistry and Physics

ISSN: 1680-7316 (Print); 1680-7324 (Online)

Publisher: Copernicus Publications

Society/Institution: European Geosciences Union (EGU)

LCC Subject Category: Science: Physics | Science: Chemistry

Country of publisher: Germany

Language of fulltext: English

Full-text formats available: PDF, XML

 

AUTHORS

A. K. Y. Lee (Department of Chemistry, University of Toronto, Toronto, Canada)
M. D. Willis (Department of Chemistry, University of Toronto, Toronto, Canada)
R. M. Healy (Department of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland)
J. M. Wang (Southern Ontario Centre for Atmospheric Aerosol Research, Department of Chemical Engineering & Applied Chemistry, University of Toronto, Toronto, Canada)
C.-H. Jeong (Southern Ontario Centre for Atmospheric Aerosol Research, Department of Chemical Engineering & Applied Chemistry, University of Toronto, Toronto, Canada)
J. C. Wenger (Department of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland)
G. J. Evans (Southern Ontario Centre for Atmospheric Aerosol Research, Department of Chemical Engineering & Applied Chemistry, University of Toronto, Toronto, Canada)
J. P. D. Abbatt (Department of Chemistry, University of Toronto, Toronto, Canada)

EDITORIAL INFORMATION

Peer review

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Time From Submission to Publication: 16 weeks

 

Abstract | Full Text

Biomass burning organic aerosol (BBOA) can be emitted from natural forest fires and human activities such as agricultural burning and domestic energy generation. BBOA is strongly associated with atmospheric brown carbon (BrC) that absorbs near-ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single-particle measurements from a Soot-Particle Aerosol Mass Spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC), and potassium (K, a tracer for biomass burning aerosol) in an air mass influenced by wildfire emissions transported from northern Québec to Toronto, representing aged biomass burning plumes. Cluster analysis of single-particle measurements identified five BBOA-related particle types. rBC accounted for 3–14 wt % of these particle types on average. Only one particle type exhibited a strong ion signal for K<sup>+</sup>, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles. The average mass absorption efficiency of low-volatility BBOA is about 0.8–1.1 m<sup>2</sup> g<sup>−1</sup> based on a theoretical closure calculation. Our estimates indicate that low-volatility BBOA contributes ∼ 33–44 % of thermo-processed particle absorption at 405 nm; and almost all of the BBOA absorption was associated with low-volatility organics.