Secondary organic aerosol coating formation and evaporation: Chamber studies using black carbon seed aerosol and the single-particle soot photometer

Andrew R. Metcalf, Christine L. Loza, Matthew M. Coggon, Jill S. Craven, Haflidi H. Jonsson, Richard C. Flagan, John H. Seinfeld

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

We report a protocol for using black carbon (BC) aerosol as the seed for secondary organic aerosol (SOA) formation in an environmental chamber. We employ a single-particle soot photometer (SP2) to probe single-particle SOA coating growth dynamics and find that SOA growth on nonspherical BC aerosol is diffusionlimited. Aerosol composition measurements with an Aerodyne high resolution time-of-flight aerosol mass spectrometer (AMS) confirm that the presence of BC seed does not alter the composition of SOA as compared to self-nucleated SOA or condensed SOA on ammonium sulfate seed. We employ a 3-wavelength photoacoustic soot spectrometer (PASS-3) to measure optical properties of the systems studied, including fullerene soot as the surrogate BC seed, nucleated naphthalene SOA from high-NOx photooxidation, and nucleated a-pinene SOA from low-NOx photooxidation. A core-and-shell Mie scattering model of the light absorption enhancement is in good agreement with measured enhancements for both the low- and high-NOx a-pinene photooxidation systems, reinforcing the assumption of a core-shell morphology for coated BC particles. A discrepancy between measured and modeled absorption enhancement factors in the naphthalene photooxidation system is attributed to the wavelength-dependence of refractive index of the naphthalene SOA. The coating of high-NOx a-pinene SOA decreases after reaching a peak thickness during irradiation, reflecting a volatility change in the aerosol, as confirmed by the relative magnitudes of f43 and f44 in the AMS spectra. The protocol described here provides a framework by which future studies of SOA optical properties and single-particle growth dynamics may be explored in environmental chambers.

Original languageEnglish (US)
Pages (from-to)326-347
Number of pages22
JournalAerosol Science and Technology
Volume47
Issue number3
DOIs
StatePublished - Jan 21 2013

Fingerprint Dive into the research topics of 'Secondary organic aerosol coating formation and evaporation: Chamber studies using black carbon seed aerosol and the single-particle soot photometer'. Together they form a unique fingerprint.

Cite this