Emissions of reactive nitrogen from Western U.S. wildfires during summer 2018

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 N-r normalized excess mixing ratios and emission factors from fires sampled within 80 min of estimated emission and explore variability in the dominant forms of N-r between these fires.

We find that reduced N compounds comprise a majority (39%-80%; median = 66%) of total measured reactive nitrogen (Sigma N-r) 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 (Sigma NOy) and measured total Sigma NHx (NH3 + pNH(4)) are more robustly correlated with modified combustion efficiency (MCE) than NOx and NH3 by themselves.