Airborne and ground-based measurements of the trace gases and particles emitted by prescribed fires in the United States

We have measured emission factors for 19 tracegas species and particulate matter (PM2.5) from 14 prescribedfires in chaparral and oak savanna in the southwesternUS, as well as conifer forest understory in the southeasternUS and Sierra Nevada mountains of California. These arelikely the most extensive emission factor field measurementsfor temperate biomass burning to date and the only publishedemission factors for temperate oak savanna fuels. This studyhelps to close the gap in emissions data available for temperatezone fires relative to tropical biomass burning. Wepresent the first field measurements of the biomass burningemissions of glycolaldehyde, a possible precursor for aqueousphase secondary organic aerosol formation. We alsomeasured the emissions of phenol, another aqueous phasesecondary organic aerosol precursor. Our data confirm previousobservations that urban deposition can impact the NOxemission factors and thus subsequent plume chemistry. Fortwo fires, we measured both the emissions in the convectivesmoke plume from our airborne platform and the unloftedresidual smoldering combustion emissions with our groundbasedplatform. The smoke from residual smoldering combustionwas characterized by emission factors for hydrocarbonand oxygenated organic species that were up to ten timeshigher than in the lofted plume, including high 1,3-butadieneand isoprene concentrations which were not observed in thelofted plume. This should be considered in modeling the air quality impacts for smoke that disperses at ground level. Wealso show that the often ignored unlofted emissions can significantlyimpact estimates of total emissions. Preliminaryevidence suggests large emissions of monoterpenes in theresidual smoldering smoke. These data should lead to animproved capacity to model the impacts of biomass burningin similar temperate ecosystems.