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Abstract. Extensive airborne measurements of non-methane organic gases (NMOGs), methane, nitrogen oxides, reduced nitrogen species, and aerosol emissions from US wild and prescribed fires were conducted during the 2019 NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality campaign (FIREX-AQ). Here, we report the atmospheric enhancement ratios (ERs) and inferred emission factors (EFs) for compounds measured on board the NASA DC-8 research aircraft for nine wildfires and one prescribed fire, which encompass a range of vegetation types. We use photochemical proxies to identify young smoke and reduce the effects of chemical degradation on our emissions calculations. ERs and EFs calculated from FIREX-AQ observations agree within a factor of 2, with values reported from previous laboratory and field studies for more than 80 % of the carbon- and nitrogen-containing species. Wildfire emissions are parameterized based on correlations of the sum of NMOGs with reactive nitrogen oxides (NOy) to modified combustion efficiency (MCE) as well as other chemical signatures indicative of flaming/smoldering combustion, including carbon monoxide (CO), nitrogen dioxide (NO2), and black carbon aerosol. The sum of primary NMOG EFs correlates to MCE with an R2 of 0.68 and a slope of −296 ± 51 g kg−1, consistent with previous studies. The sum of the NMOG mixing ratios correlates well with CO with an R2 of 0.98 and a slope of 137 ± 4 ppbv of NMOGs per parts per million by volume (ppmv) of CO, demonstrating that primary NMOG emissions can be estimated from CO. Individual nitrogen-containing species correlate better with NO2, NOy, and black carbon than with CO. More than half of the NOy in fresh plumes is NO2 with an R2 of 0.95 and a ratio of NO2 to NOy of 0.55 ± 0.05 ppbv ppbv−1, highlighting that fast photochemistry had already occurred in the sampled fire plumes. The ratio of NOy to the sum of NMOGs follows trends observed in laboratory experiments and increases exponentially with MCE, due to increased emission of key nitrogen species and reduced emission of NMOGs at higher MCE during flaming combustion. These parameterizations will provide more accurate boundary conditions for modeling and satellite studies of fire plume chemistry and evolution to predict the downwind formation of secondary pollutants, including ozone and secondary organic aerosol. 

Abstract. Anthropogenic secondary organic aerosol (ASOA), formed from anthropogenicemissions of organic compounds, constitutes a substantial fraction of themass of submicron aerosol in populated areas around the world andcontributes to poor air quality and premature mortality. However, theprecursor sources of ASOA are poorly understood, and there are largeuncertainties in the health benefits that might accrue from reducinganthropogenic organic emissions. We show that the production of ASOA in 11urban areas on three continents is strongly correlated with the reactivityof specific anthropogenic volatile organic compounds. The differences inASOA production across different cities can be explained by differences inthe emissions of aromatics and intermediate- and semi-volatile organiccompounds, indicating the importance of controlling these ASOA precursors.With an improved model representation of ASOA driven by the observations,we attribute 340 000 PM2.5-related premature deaths per year to ASOA, which isover an order of magnitude higher than prior studies. A sensitivity casewith a more recently proposed model for attributing mortality to PM2.5(the Global Exposure Mortality Model) results in up to 900 000 deaths. Alimitation of this study is the extrapolation from cities with detailedstudies and regions where detailed emission inventories are available toother regions where uncertainties in emissions are larger. In addition tofurther development of institutional air quality management infrastructure,comprehensive air quality campaigns in the countries in South and CentralAmerica, Africa, South Asia, and the Middle East are needed for furtherprogress in this area.