As part of the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) field campaign, aircraft collected samples from smoke plumes emitted by wildfires across the western US in summer 2018. A research team funded in part by CPO’s Atmospheric Chemistry, Carbon Cycle, & Climate (AC4) program observed and summarized the evolution of reactive oxidized nitrogen species in the sampled WE-CAN plumes. This comprehensive summary is available in the Journal of Geophysical Research Atmospheres. As a whole, the summary provides an organized dataset for the modeling community to investigate the processes controlling the evolution of reactive oxidized nitrogen in smoke.
Wildfires release large amounts of trace gases and particulate matter into the atmosphere, directly affecting air quality, weather, and climate. Reactive oxidized nitrogen species, aka chemical forms of nitrogen compounds with oxygen that easily react and change, is one such category of emissions. Understanding how reactive oxidized nitrogen changes or evolves in smoke after being emitted is necessary to predict further impacts, such as the formation of secondary pollutants. WE-CAN allowed researchers to study the partitioning, or the splitting off into various forms, of reactive oxidized nitrogen across multiple wildfire smoke plumes.
Major takeaways from the study include the observation that original emissions of reactive oxidized nitrogen are rapidly transformed within the first few hours of emission; that there are significant differences observed between samples from different fires; and, that partitioning can vary with altitude. Notably, for the samples where smoke mixed with anthropogenic emissions from the California Central Valley region, it was possible to identify which emissions were anthropogenic and which were not. The anthropogenic emissions contributed additional nitrogen oxides to the plume, leading to more peroxy acyl nitrates formation, which are large respiratory and eye irritants.