Issue 1, 2023

Atmospheric OH reactivity in the western United States determined from comprehensive gas-phase measurements during WE-CAN

Abstract

Wildfire smoke contains numerous different reactive organic gases, many of which have only recently been identified and quantified. Consequently, their relative importance as an oxidant sink is poorly constrained, resulting in incomplete representation in both global chemical transport models (CTMs) and explicit chemical mechanisms. Leveraging 160 gas-phase measurements made during the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) aircraft campaign, we calculate OH reactivities (OHRs) for western U.S. wildfire emissions, smoke aged >3 days, smoke-impacted and low/no smoke-impacted urban atmospheres, and the clean free troposphere. VOCs were found to account for ∼80% of the total calculated OHR in wildfire emissions, with at least half of the field VOC OHR not currently implemented for biomass burning (BB) emissions in the commonly used GEOS-Chem CTM. To improve the representation of OHR, we recommend CTMs implement furan-containing species, butadienes, and monoterpenes for BB. The Master Chemical Mechanism (MCM) was found to account for 88% of VOC OHR in wildfire emissions and captures its observed decay in the first few hours of aging, indicating that most known VOC OH sinks are included in the explicit mechanisms. We find BB smoke enhanced the average total OHR by 53% relative to the low/no smoke urban background, mainly due to the increase in VOCs and CO thus promoting urban ozone production. This work highlights the most important VOC species for daytime BB plume oxidation and provides a roadmap for which species should be prioritized in next-generation CTMs to better predict the downwind air quality and health impacts of BB smoke.

Graphical abstract: Atmospheric OH reactivity in the western United States determined from comprehensive gas-phase measurements during WE-CAN

Supplementary files

Transparent peer review

To support increased transparency, we offer authors the option to publish the peer review history alongside their article.

View this article’s peer review history

Article information

Article type
Paper
Submitted
02 Jūn. 2022
Accepted
07 Okt. 2022
First published
31 Okt. 2022
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Atmos., 2023,3, 97-114

Atmospheric OH reactivity in the western United States determined from comprehensive gas-phase measurements during WE-CAN

W. Permar, L. Jin, Q. Peng, K. O'Dell, E. Lill, V. Selimovic, R. J. Yokelson, R. S. Hornbrook, A. J. Hills, E. C. Apel, I. Ku, Y. Zhou, B. C. Sive, A. P. Sullivan, J. L. Collett, B. B. Palm, J. A. Thornton, F. Flocke, E. V. Fischer and L. Hu, Environ. Sci.: Atmos., 2023, 3, 97 DOI: 10.1039/D2EA00063F

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements