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Mixing order of sulfate aerosols and isoprene epoxydiols affect secondary organic aerosol formation in chamber experiments

Nah, Theodora and Xu, Lu and Osborne-Benthaus, Kymberlee A. and White, S. Meghan and France, Stefan and Ng, Nga Lee (2019) Mixing order of sulfate aerosols and isoprene epoxydiols affect secondary organic aerosol formation in chamber experiments. Atmospheric Environment, 217 . Art. No. 116953. ISSN 1352-2310.

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The reactive uptake of isoprene epoxydiols (IEPOX) is a significant source of isoprene-derived secondary organic aerosols (SOA). Multiple field studies have reported that summertime isoprene-derived SOA in the Southeastern U.S. correlated strongly with sulfate mass concentration. However, previous laboratory studies have focused largely on the effect of aerosol acidity on the reactive uptake of IEPOX. In this study, we investigated the role of inorganic sulfate aerosols in SOA formation arising from the reactive uptake of trans-β-IEPOX (the predominant IEPOX isomer) at 50–56% RH in laboratory chamber experiments. Our measurements showed that the SOA mass concentration increased with the sulfate mass for both highly acidic and less acidic seed aerosols. This was due to the roles that sulfate played in SOA formation as a particle-phase reactant and as a contributor to aerosol surface area and volume. Higher concentrations of SOA were formed when highly acidic seed aerosols were used, consistent with previous laboratory studies. SOA mass concentration and composition were also observed to be dependent on the injection order of IEPOX and sulfate seed aerosols (i.e., injection of IEPOX first vs. Injection of seed aerosols first) in the chamber experiments. Higher SOA mass concentrations were measured in experiments where sulfate seed aerosols were introduced into the chamber first, followed by IEPOX. Volatility measurements showed that the SOA formed in the “seed aerosols first” experiments likely contained larger quantities of low volatility organic matter compared to SOA formed in the “IEPOX first” experiments. These results showed that the mass concentration and composition of IEPOX-derived SOA formed in chamber experiments can be sensitive to mixing conditions in the chamber brought about by slight differences in experimental methodology (in this case injection procedure). The sensitivity of SOA formation to the amount of seed aerosols and injection procedure used in chamber experiments indicated that caution should be exercised when extrapolating laboratory data to ambient conditions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Nah, Theodora0000-0002-8755-6153
Xu, Lu0000-0002-0021-9876
White, S. Meghan0000-0002-1215-116X
Ng, Nga Lee0000-0001-8460-4765
Additional Information:© 2019 Published by Elsevier Ltd. Received 29 March 2019, Revised 24 August 2019, Accepted 2 September 2019, Available online 6 September 2019. This research was funded by NSF AGS-1455588 awarded to Georgia Institute of Technology. The FIGAERO-HR-ToF-CIMS was purchased with NSF Major Research Instrumentation (MRI) grant 1428738. K.O.B. thanks NSF for a graduate research fellowship (DGE-1148903). We thank Raynold Shenje for preliminary work on the trans-β-IEPOX synthesis, and Yunle Chen for assistance with preliminary chamber experiments. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1148903
Subject Keywords:Secondary organic aerosols; Isoprene; Reactive uptake; Sulfate; Multiphase chemistry
Record Number:CaltechAUTHORS:20190906-093254969
Persistent URL:
Official Citation:Theodora Nah, Lu Xu, Kymberlee A. Osborne-Benthaus, S. Meghan White, Stefan France, Nga Lee Ng, Mixing order of sulfate aerosols and isoprene epoxydiols affects secondary organic aerosol formation in chamber experiments, Atmospheric Environment, Volume 217, 2019, 116953, ISSN 1352-2310, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98473
Deposited By: Tony Diaz
Deposited On:06 Sep 2019 17:21
Last Modified:03 Oct 2019 21:41

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