In situ measurements of ammonia in plumes emitted from wildfires and agricultural fires in the US

Emissions of trace gases and particles from fires have a major impact on climate, visibility, air quality, and public health. Biomass burning emissions include reactive nitrogen gases, among which ammonia (NH₃) plays a prominent role. NH₃ is a short-lived gas that acts as precursor for secondary inorganic aerosols. This process is still poorly constrained in downwind fire plumes.

In summer 2019, NASA and NOAA carried out the joint airborne FIREX-AQ (Fire Influence on Regional to global Environments and Air Quality) mission over the continental US to sample plumes from wildfires and agricultural fires. On board the NASA DC-8, we used a modified PTR-ToF-MS instrument for measuring NH₃ in situ and at high time resolution. Over the course of the mission, we collected a large set of NH₃ data in plumes emitted from fires differing in fuel type and burning stage. Herein, we will present the measured NH₃ emissions ratios and factors, compare them with the literature, and investigate the dependence of NH₃ emissions on fuel type and burning conditions.