The Reactive Nitrogen Budget of Laboratory-Simulated Western North American Wildfires

Wildfires are a significant source of reactive nitrogen (N_r = all N compounds aside from N₂ and N₂O) to the atmosphere, influencing both photooxidation and secondary aerosol formation chemistries. In addition, some individual N compounds are health actors in their own right. Total N_r was measured along with individual N compounds during the FIREX Fire Lab experiment in 2016. This presentation will summarize the nitrogen budget for a series of burns of fuels characteristic of western North America. Our observations confirm that during the average fire, most nitrogen is lost as N₂ due to combustion- associated denitrification chemistry. The remaining N_r composition was found to depend broadly on combustion temperature, similar to that observed for volatile organic compounds (Sekimoto et al., 2018), except that NOx (nitric oxide and nitrogen dioxide) appears at under temperature conditions much higher than the high temperature VOC compounds. As a result, N_r emissions fall into roughly three regimes, very high temperature (NOx, and to some extent nitrous acid), high temperature (HNCO, HCN and organic nitriles) and low temperature (NH₃, and most org-N compounds).