Nitrogen oxides and PAN in plumes from boreal fires during ARCTAS-B and their impact on ozone: an integrated analysis of aircraft and satellite observations

Abstract

We determine enhancement ratios for NO<sub>x</sub>, PAN, and other NO<sub>y</sub> species from boreal biomass burning using aircraft data obtained during the ARCTAS-B campaign and examine the impact of these emissions on tropospheric ozone in the Arctic. We find an initial emission factor for NO<sub>x</sub> of 1.06 g NO per kg dry matter (DM) burned, much lower than previous observations of boreal plumes, and also one third the value recommended for extratropical fires. Our analysis provides the first observational confirmation of rapid PAN formation in a boreal smoke plume, with 40% of the initial NO<sub>x</sub> emissions being converted to PAN in the first few hours after emission. We find little clear evidence for ozone formation in the boreal smoke plumes during ARCTAS-B in either aircraft or satellite observations, or in model simulations. Only a third of the smoke plumes observed by the NASA DC8 showed a correlation between ozone and CO, and ozone was depleted in the plumes as often as it was enhanced. Special observations from the Tropospheric Emission Spectrometer (TES) also show little evidence for enhanced ozone in boreal smoke plumes between 15 June and 15 July 2008. Of the 22 plumes observed by TES, only 4 showed ozone increasing within the smoke plumes, and even in those cases it was unclear that the increase was caused by fire emissions. Using the GEOS-Chem atmospheric chemistry model, we show that boreal fires during ARCTAS-B had little impact on the median ozone profile measured over Canada, and had little impact on ozone within the smoke plumes observed by TES

Emission Ratios for Ammonia and Formic Acid and Observations of Peroxy Acetyl Nitrate (PAN) and Ethylene in Biomass Burning Smoke as Seen by the Tropospheric Emission Spectrometer (TES)

“…Biomass burning plumes were identified following the procedure in Alvarado et al [12], which we briefly outline here. We used maps of Level 3 daily AIRS retrievals of CO at 1° × 1° resolution to identify the transport of CO from major regions of boreal biomass burning.…”

“…This data set includes several observations of smoke plumes from boreal fires in Siberia and Canada. Alvarado et al previously analyzed the correlation between TES retrievals of CO and O 3 within these smoke plumes [12]. Here we use nadir observations from TES to determine the concentrations of the trace gases ammonia (NH 3 ) and formic acid (HCOOH) within two boreal biomass burning plumes over Canada and determine the emission ratio of these gases relative to CO.…”

“…The primary NO x emissions from biomass burning are rapidly converted to PAN within biomass burning plumes [12,37]. Satellite retrievals of PAN could provide substantial information on the fate of NO x emitted by biomass burning in the atmosphere and the impact of these NO x emissions on global tropospheric ozone.…”

“…It has a short lifetime in the summer Arctic troposphere (14-35 h, [12]) due to rapid reaction with OH. As this rapid oxidation of ethylene impacts the ozone formation rate within young smoke plumes [40], better estimates of the emissions of ethylene from biomass burning could help to reduce the uncertainty in the impact of biomass burning on tropospheric ozone.…”

“…Examples of these studies include: estimating the emission rate of fine particles with fire radiative power (FRP) and aerosol optical depth retrievals from the Moderate-Resolution Imaging Spectroradiometer (MODIS) [5,6]; estimating emissions of NO x with MODIS FRP and tropospheric NO 2 columns from the Ozone Monitoring Instrument (OMI) [7]; constraining emissions of CO using retrievals from the Measurements Of Pollution In The Troposphere (MOPITT) instrument, the Atmospheric Infrared Sounder (AIRS), the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), and the Tropospheric Emission Spectrometer (TES) [8]; detecting several trace gases within smoke plumes using the Infrared Atmospheric Sounding Interferometer (IASI) [9,10]; and estimating the correlation between CO and O 3 in smoke plumes with TES [11][12][13].…”