Airborne measurements of western U.S. wildfire emissions: Comparison with prescribed burning and air quality implications

Abstract

Wildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured from aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) and the Biomass Burning Observation Project (BBOP), both in summer 2013. This study reports an extensive set of emission factors (EFs) for over 80 gases and 5 components of submicron particulate matter (PM1) from these temperate wildfires. These include rarely, or never before, measured oxygenated volatile organic compounds and multifunctional organic nitrates. The observed EFs are compared with previous measurements of temperate wildfires, boreal forest fires, and temperate prescribed fires. The wildfires emitted high amounts of PM1 (with organic aerosol (OA) dominating the mass) with an average EF that is more than 2 times the EFs for prescribed fires. The measured EFs were used to estimate the annual wildfire emissions of carbon monoxide, nitrogen oxides, total nonmethane organic compounds, and PM1 from 11 western U.S. states. The estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI). However, our PM1 emission estimate (1530 ± 570 Gg yr−1) is over 3 times that of the NEI PM2.5 estimate and is also higher than the PM2.5 emitted from all other sources in these states in the NEI. This study indicates that the source of OA from biomass burning in the western states is significantly underestimated. In addition, our results indicate that prescribed burning may be an effective method to reduce fine particle emissions.

Non-methane organic gas emissions from biomass burning: identification, quantification, and emission factors from PTR-ToF during the FIREX 2016 laboratory experiment

“…Many of the above species have EFs that agree between PTR-ToF and FTIR within 10 % (Selimovic et al, 2017; Table S8). Additionally, it has been shown that the FTIR fire-integrated emission factors derived for hydroxyacetone are in excellent agreement with that reported for real wildfires by Liu et al (2017b;Selimovic et al, 2017).…”

“…6). The ER to CO are likely the easiest way to incorporate this new NMOG data into models since CO emissions from wildfires are relatively well characterized (Liu et al, 2017b). The 156 PTR ions for which we have identified the NMOG contributors account for a significant fraction of the instrument signal and total NMOG detected by the PTR-ToF instrument in each fire.…”

Speciated and total emission factors of particulate organics from burning western U.S. wildland fuels and their dependence on combustion efficiency

“…Specifically, Liu et al (2017) reported MCE values from three different California wildfires and total organic aerosol (OA) particle EFs, which are the most equivalent to total I/SVOC EFs measured here (though at MCE values of <0.8, we observed higher IVOCs mass loadings in our 20 chromatograms which would likely not be included in the OA EFs at lower particle mass loadings (May et al, 2013) cannot be evaluated at this time. Without this information, uncertainty in using the reported regression models in predicting EFs of various chemical families is estimated to be a factor of 3.…”

“…These regression models can be used to approximate EFs of I/SVOCs or their chemical families from average MCE of real wildfires. For example, comparison with Liu et al (2017) shows the estimated 25 particulate organics from the regression model to be within a factor of 2-3 from those measured in that study. The comparison between predicted and previously measured EFs is affected by methodology, concentration regime, and the definitions of I/SVOC.…”

“…In general, biomass burning, which includes wildfires, is the main global source of fine carbonaceous aerosol particles (~75%) in the atmosphere (Andreae and Merlet, 2001;Bond and Bergstrom, 2006;IPCC, 2014;Park et al, 2007). Individual and categorized organic emissions from wildfires have previously been 15 identified and quantified (Akagi et al, 2011;Andreae and Merlet, 2001;Hatch et al, 2015;Kim et al, 2013;Koss et al, 2018;Liu et al, 2017;Mazzoleni et al, 2007;Naeher et al, 2007;Oros et al, 2006;Oros and Simoneit, 2001a;Simoneit, 2002;Stockwell et al, 2015;Yokelson et al, 2013). The bulk of previous studies on speciated organic compound emissions focused on gas-phase volatile organic compounds (VOCs).…”