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

Reactive nitrogen (Nr) 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 estimateNrnormalized excess mixing ratios and emission factors from fires sampled within 80 min of estimated emission and explore variability in the dominant forms ofNrbetween these fires. We find that reduced N compounds comprise a majority (39%–80%; median = 66%) of total measured reactive nitrogen (ΣNr) 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 (ΣNOy) and measured totalΣNHx(NH3 + pNH4) are more robustly correlated with modified combustion efficiency (MCE) than NOxand NH3by themselves. The ratio of ΣNHx/ΣNOydisplays a negative relationship with MCE, consistent with previous studies. A positive relationship with total measuredΣNrsuggests that both burn conditions and fuel N content/volatilization differences contribute to the observed variability in the distribution of reduced and oxidizedNr. Additionally, we compare our in situ field estimates ofNrEFs to previous lab and field studies. For similar fuel types, we findΣNHxEFs are of the same magnitude or larger than lab‐based NH3EF estimates, andΣNOyEFs are smaller than lab NOxEFs.

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Award ID(s):
1650786 1652688 1650275
Author(s) / Creator(s):
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Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Journal of Geophysical Research: Atmospheres
Medium: X
Sponsoring Org:
National Science Foundation
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