Laboratory measurements of trace gas emissions from biomass burning of fuel types from the southeastern and southwestern United States

Abstract

Abstract. Vegetation commonly managed by prescribed burning was collected from five southeastern and southwestern US military bases and burned under controlled conditions at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The smoke emissions were measured with a large suite of state-of-the-art instrumentation including an open-path Fourier transform infrared (OP-FTIR) spectrometer for measurement of gas-phase species. The OP-FTIR detected and quantified 19 gas-phase species in these fires: CO 2 , CO, CH 4 , C 2 H 2 , C 2 H 4 , C 3 H 6 , HCHO, HCOOH, CH 3 OH, CH 3 COOH, furan, H 2 O, NO, NO 2 , HONO, NH 3 , HCN, HCl, and SO 2 . Emission factors for these species are presented for each vegetation type burned. Gas-phase nitrous acid (HONO), an important OH precursor, was detected in the smoke from all fires. The HONO emission factors ranged from 0.15 to 0.60 g kg −1 and were higher for the southeastern fuels. The fire-integrated molar emission ratios of HONO (relative to NO x ) ranged from approximately 0.03 to 0.20, with higher values also observed for the southeastern fuels. The majority of non-methane organic compoundCorrespondence to: R. J. Yokelson (bob.yokelson@umontana.edu) (NMOC) emissions detected by OP-FTIR were oxygenated volatile organic compounds (OVOCs) with the total identified OVOC emissions constituting 61 ± 12% of the total measured NMOC on a molar basis. These OVOC may undergo photolysis or further oxidation contributing to ozone formation. Elevated amounts of gas-phase HCl and SO 2 were also detected during flaming combustion, with the amounts varying greatly depending on location and vegetation type. The fuels with the highest HCl emission factors were all located in the coastal regions, although HCl was also observed from fuels farther inland. Emission factors for HCl were generally higher for the southwestern fuels, particularly those found in the chaparral biome in the coastal regions of California.

Spatial and temporal variability in the ratio of trace gases emitted from biomass burning

“…The slope of the regression lines of these individual studies was more gentle than the slope we found for the whole dataset. Lab experiments McMeeking et al, 2009;Burling et al, 2010) also show overall higher correlations between MCE and EF CH 4 than our results for all data for the different vegetation biomes combined.…”

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)

“…Emission factors for biomass burning are primarily based on airborne and ground field measurements and measurements from small fires conducted in laboratories. Laboratory studies have shown that emissions of trace gases and particles from biomass burning can vary widely based on the type of fuel burned as well as the phase of combustion (i.e., whether the combustion is in the early "flaming" stages or the later "smoldering" stages) [4]. However, the size, fuel moisture, and combustion characteristics of laboratory fires may not be representative of large-scale wildfires.…”

Recent trends in gas-phase ammonia and PM2.5 ammonium in the Southeast United States

“…It has been recognized for many years that biomass burning can be a source of elevated NH 3 concentrations (Hegg et al, 1988), and both laboratory (Burling et al, 2010) and field (Akagi et al, 2013(Akagi et al, , 2014 measurements have documented wildfires and prescribed burning as important NH 3 sources in the Southeast. Although Xing et al (2013) estimates that wildfires typically account for only 1-3% of annual NH 3 emissions in the U.S. and 3-10% of annual emissions in SEARCH states, the incidence of wildfires are expected to increase in the Southeast as a result of continuing global change (Liu et al, 2014).…”