Emissions of Reactive Nitrogen From Western U.S. Wildfires During Summer 2018

Media type: E-Article
Title: Emissions of Reactive Nitrogen From Western U.S. Wildfires During Summer 2018
Contributor: Lindaas, Jakob; Pollack, Ilana B.; Garofalo, Lauren A.; Pothier, Matson A.; Farmer, Delphine K.; Kreidenweis, Sonia M.; Campos, Teresa L.; Flocke, Frank; Weinheimer, Andrew J.; Montzka, Denise D.; Tyndall, Geoffrey S.; Palm, Brett B.; Peng, Qiaoyun; Thornton, Joel A.; Permar, Wade; Wielgasz, Catherine; Hu, Lu; Ottmar, Roger D.; Restaino, Joseph C.; Hudak, Andrew T.; Ku, I‐Ting; Zhou, Yong; Sive, Barkley C.; Sullivan, Amy; [...]
imprint: American Geophysical Union (AGU), 2021
Published in: Journal of Geophysical Research: Atmospheres
Language: English
DOI: 10.1029/2020jd032657
ISSN: 2169-897X; 2169-8996
Origination:
Footnote:
Description: <jats:title>Abstract</jats:title><jats:p>Reactive nitrogen (<jats:italic>N</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub>) within smoke plumes plays important roles in the production of ozone, the formation of secondary aerosols, and deposition of fixed N to ecosystems. The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE‐CAN) field campaign sampled smoke from 23 wildfires throughout the western U.S. during summer 2018 using the NSF/NCAR C‐130 research aircraft. We empirically estimate <jats:italic>N</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub> normalized excess mixing ratios and emission factors from fires sampled within 80 min of estimated emission and explore variability in the dominant forms of <jats:italic>N</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub> between these fires. We find that reduced N compounds comprise a majority (39%–80%; median = 66%) of total measured reactive nitrogen (<jats:italic>ΣN</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub>) emissions. The smoke plumes sampled during WE‐CAN feature rapid chemical transformations after emission. As a result, within minutes after emission total measured oxidized nitrogen (<jats:italic>Σ</jats:italic>NO<jats:sub>y</jats:sub>) and measured total <jats:italic>Σ</jats:italic>NH<jats:sub>x</jats:sub> (NH<jats:sub>3</jats:sub> + <jats:italic>p</jats:italic>NH<jats:sub>4</jats:sub>) are more robustly correlated with modified combustion efficiency (MCE) than NO<jats:sub>x</jats:sub> and NH<jats:sub>3</jats:sub> by themselves. The ratio of ΣNH<jats:sub>x</jats:sub>/ΣNO<jats:sub>y</jats:sub> displays a negative relationship with MCE, consistent with previous studies. A positive relationship with total measured <jats:italic>ΣN</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub> suggests that both burn conditions and fuel N content/volatilization differences contribute to the observed variability in the distribution of reduced and oxidized <jats:italic>N</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub>. Additionally, we compare our in situ field estimates of <jats:italic>N</jats:italic><jats:sub><jats:italic>r</jats:italic></jats:sub> EFs to previous lab and field studies. For similar fuel types, we find <jats:italic>Σ</jats:italic>NH<jats:sub>x</jats:sub> EFs are of the same magnitude or larger than lab‐based NH<jats:sub>3</jats:sub> EF estimates, and <jats:italic>Σ</jats:italic>NO<jats:sub>y</jats:sub> EFs are smaller than lab NO<jats:sub>x</jats:sub> EFs.</jats:p>
Access State: Open Access

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