Daytime oxidized reactive nitrogen partitioning in Western U.S. wildfire smoke plumes

We present a summary of a subset of reactive oxidized nitrogen species (NOy) in plumes sampled in a pseudo-Lagrangian fashion. Emissions of nitrogen oxides (NOx = NO + NO2) and nitrous acid (HONO) are rapidly converted to more oxidized forms.

Within 4 h, similar to 86% of the sigma NOy is in the form of peroxy acyl nitrates (PANs) (similar to 37%), particulate nitrate (pNO(3)) (similar to 27%), and gas-phase organic nitrates (Org N-(g)) (similar to 23%). The average e-folding time and distance for NOx are similar to 90 min and similar to 40 km, respectively. Nearly no enhancements in nitric acid (HNO3) were observed in plumes sampled in a pseudo-Lagrangian fashion, implying HNO3-limited ammonium nitrate (NH4NO3) formation, with one notable exception that we highlight as a case study.