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Published December 16, 2021 | Supplemental Material + Published
Journal Article Open

Modeling secondary organic aerosol formation from volatile chemical products


Volatile chemical products (VCPs) are commonly used consumer and industrial items that are an important source of anthropogenic emissions. Organic compounds from VCPs evaporate on atmospherically relevant timescales and include many species that are secondary organic aerosol (SOA) precursors. However, the chemistry leading to SOA, particularly that of intermediate-volatility organic compounds (IVOCs), has not been fully represented in regional-scale models such as the Community Multiscale Air Quality (CMAQ) model, which tend to underpredict SOA concentrations in urban areas. Here we develop a model to represent SOA formation from VCP emissions. The model incorporates a new VCP emissions inventory and employs three new classes of emissions: siloxanes, oxygenated IVOCs, and nonoxygenated IVOCs. VCPs are estimated to produce 1.67 µg m−3 of noontime SOA, doubling the current model predictions and reducing the SOA mass concentration bias from −75 % to −58 % when compared to observations in Los Angeles in 2010. While oxygenated and nonoxygenated intermediate-volatility VCP species are emitted in similar quantities, SOA formation is dominated by the nonoxygenated IVOCs. Formaldehyde and SOA show similar relationships to temperature and bias signatures, indicating common sources and/or chemistry. This work suggests that VCPs contribute up to half of anthropogenic SOA in Los Angeles and models must better represent SOA precursors from VCPs to predict the urban enhancement of SOA.

Additional Information

© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 28 Jun 2021 – Discussion started: 01 Jul 2021 – Revised: 18 Oct 2021 – Accepted: 20 Oct 2021 – Published: 16 Dec 2021. The authors thank Christopher Cappa, Wyat Appel, and Ben Schulze for modeling support and helpful discussions. Karl Seltzer and Elyse Pennington were supported by the Oak Ridge Institute for Science and Education (ORISE) Research Participation Program for the US Environmental Protection Agency (EPA). Elyse Pennington was also supported by a Global Research Outreach (GRO) award from the Samsung Advanced Institute of Technology (SAIT). Data availability. CalNex observations are publicly available at https://www.esrl.noaa.gov/csd/groups/csd7/measurements/2010calnex/ (last access: 7 July 2021) (CalNex measurement data, 2012). The full VCPy dataset is available by downloading VCPyv1.0 at https://doi.org/10.23719/1520157 (U.S. EPA, 2021a). The SAPRC07TIC_AE7I_VCP speciation profile, CMAQ chemical mechanism source code, and CMAQ output are posted at https://doi.org/10.23719/1522655 (U.S. EPA, 2021b). The supplement related to this article is available online at: https://doi.org/10.5194/acp-21-18247-2021-supplement. Author contributions. HOTP, KMS, and EAP designed the research. EAP and KMS implemented the mechanism in 65 CMAQv5.3.2 and ran the simulations. EAP, KMS, HOTP, BNM, MQ, and JHS participated in data analysis and discussions. EAP drafted the paper with input from all co-authors. The contact author has declared that neither they nor their co-authors have any competing interests. Review statement. This paper was edited by Manabu Shiraiwa and reviewed by three anonymous referees. Although this work was contributed by research staff in the Environmental Protection Agency and has been reviewed and approved for publication, it does not reflect official policy of the EPA. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the agency. EPA does not endorse any products or commercial services mentioned in this publication.

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Published - acp-21-18247-2021.pdf

Supplemental Material - acp-21-18247-2021-supplement.pdf


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