Measurement report: Emission factors of NH3 and NHx for wildfires and agricultural fires in the United States
Citation:
Tomsche, L., F. Piel, T. Mikoviny, C. Nielsen, H. Guo, P. Campuzano-Jost, B. Nault, M. Schueneman, J. Jimenez, H. Halliday, G. Diskin, J. DiGangi, J. Nowak, E. Wiggins, E. Gargulinski, A. Soja, AND A. Wisthaler. Measurement report: Emission factors of NH3 and NHx for wildfires and agricultural fires in the United States. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, Germany, , 2331-2343, (2023). https://doi.org/10.5194/acp-23-2331-2023
Impact/Purpose:
FIREX-AQ was a 2019 field campaign that measured smoke events using an instrumented aircraft. A modified mass spectrometer was used to measure reduced nitrogen during these flights, and the authors report high time resolution measurements of gas phase ammonia and submicron particulate ammonium. Data and calculated emission factors are reported for a series of wildfires, grassland fires, prescribed wildland fires, and agricultural burning, encompassing a wide variety of fuel types and fire sizes. This data and analysis is important for constraining the emissions of reduced nitrogen species to the atmosphere during burning events, and helping to refine the gas to aerosol pathway and budget.
Description:
During the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study, the NASA DC-8 carried out in situ chemical measurements in smoke plumes emitted from wildfires and agricultural fires in the contiguous United States. The DC-8 payload included a modified proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) for the fast measurement of gaseous ammonia (NH3) and a high-resolution time-of-flight aerosol mass spectrometer (AMS) for the fast measurement of submicron particulate ammonium (NH4+). We herein report data collected in smoke plumes emitted from 6 wildfires in the Western United States, 2 prescribed grassland fires in the Central United States, 1 prescribed forest fire in the Southern United States, and 66 small agricultural fires in the Southeastern United States. Smoke plumes contained double to triple digit ppb levels of NH3. In the wildfire plumes, a significant fraction of NH3 had already been converted to NH4+ at the time of sampling (≥2 h after emission). Substantial amounts of NH4+ were also detected in freshly emitted smoke from corn and rice field fires. We herein present a comprehensive set of emission factors of NH3 and NHx, with NHx = NH3 + NH4+. Average NH3 and NHx emission factors for wildfires in the Western United States were 1.86±0.75 g kg−1 and 2.47±0.80 g kg−1 of fuel burned, respectively. Average NH3 and NHx emission factors for agricultural fires in the Southeastern United States were 0.89±0.58 and 1.74±0.92 g kg−1, respectively. Our data show no clear inverse correlation between modified combustion efficiency (MCE) and NH3 emissions. The observed NH3 emissions were significantly higher than measured in previous laboratory experiments in the FIREX FireLab 2016 study.
URLs/Downloads:
DOI: Measurement report: Emission factors of NH3 and NHx for wildfires and agricultural fires in the United States