Enhanced concentrations of reactive nitrogen species in wildfire smoke. (January 2017)

• Record Type: Journal Article
• Authors: Benedict, Katherine B.; Prenni, Anthony J.; Carrico, Christian M.; Sullivan, Amy P.; Schichtel, Bret A.; Collett, Jeffrey L.
• Is Part Of: Atmospheric environment. Volume 148(2017)
• Page Start: 8
• Page End: 15
• Publication Date: 2017-01
• Subjects: Biomass burning -- Ammonia -- Reactive nitrogen -- Emissions; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2016.10.030
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: During the summer of 2012 the Hewlett Gulch and High Park wildfires burned an area of 400 km 2 northwest of Fort Collins, Colorado. These fires both came within 20 km of the Department of Atmospheric Science at Colorado State University, allowing for extensive measurements of smoke-impacted air masses over the course of several weeks. In total, smoke plumes were observed at the measurement site for approximately 125 h. During this time, measurements were made of multiple reactive nitrogen compounds, including gas phase species NH3, NOx, and HNO3, and particle phase species NO3 − and NH4 +, plus an additional, unspeciated reactive nitrogen component that is measured by high temperature conversion over a catalyst to NO. Concurrent measurements of CO, levoglucosan and PM2.5 served to confirm the presence of smoke at the monitoring site. Significant enhancements were observed for all of the reactive nitrogen species measured in the plumes, except for NH4 + which did not show enhancements, likely due to the fresh nature of the plume, the presence of sufficient regional ammonia to have already neutralized upwind sulfate, and the warm conditions of the summer measurement period which tend to limit ammonium nitrate formation. Excess mixing ratios for NH3 and NOx relative to excess mixing ratios of CO in the smoke plumes, ΔNH3 /ΔCO (ppb/ppb) and ΔNOx /ΔCO (ppb/ppb), were determined to be 0.027 ± 0.002 and 0.0057 ± 0.0007, respectively. These ratios suggest that smoldering combustion was the dominant source of smoke during our plume interceptions. Observations from prior relevant laboratory and field measurements of reactive nitrogen species are also briefly summarized to help create a more comprehensive picture of reactive nitrogen and fire. Highlights: NH3, NOx, HTC-RN, NO3 −, and NH4 + were measured in fresh smoke from two wildfires. Enhanced concentrations of all reactive nitrogen species except NH4 + were observed. Ammonia during smoke-impacted periods was enhanced by a factor of 20. Excess mixing ratios NH3 relative to excess CO were found to be 0.027 ± 0.002. Excess mixing ratios NOx relative to excess CO were found to be 0.057 ± 0007.