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Media type:
E-Article
Title:
Direct Constraints on Secondary HONO Production in Aged Wildfire Smoke From Airborne Measurements Over the Western US
Contributor:
Peng, Qiaoyun;
Palm, Brett B.;
Fredrickson, Carley D.;
Lee, Ben H.;
Hall, Samuel R.;
Ullmann, Kirk;
Weinheimer, Andrew J.;
Levin, Ezra;
DeMott, Paul;
Garofalo, Lauren A.;
Pothier, Matson A.;
Farmer, Delphine K.;
Fischer, Emily V.;
Thornton, Joel A.
imprint:
American Geophysical Union (AGU), 2022
Published in:Geophysical Research Letters
Language:
English
DOI:
10.1029/2022gl098704
ISSN:
0094-8276;
1944-8007
Origination:
Footnote:
Description:
<jats:title>Abstract</jats:title><jats:p>Nitrous acid (HONO) mixing ratios measured in aged wildfire smoke plumes were higher than expected from known homogeneous chemical reactions. In a representative smoke plume, intercepted hours to days downwind of the source, the missing HONO source was highly correlated to particulate nitrate photolysis and NO<jats:sub>2</jats:sub> reactive uptake to particles. Using a multilinear regression involving these two sources, we could explain the missing HONO production in this plume (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.77). The resulting fit parameters from this plume had good explanatory power (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.64) for missing HONO production in other fire plumes. The mean enhancement factor for particulate nitrate photolysis relative to gas‐phase nitric acid photolysis was 63 and the mean NO<jats:sub>2</jats:sub> reactive uptake coefficient to submicron aerosol surface area forming HONO was 4.9 × 10<jats:sup>−4</jats:sup>. Given the likelihood of other neglected secondary HONO sources, these values are upper‐limits, suggesting a need to revisit HONO formation mechanisms in aged wildfire smoke.</jats:p>