Regional Influence of Wildfires on Aerosol Chemistry in the Western US and Insights into Atmospheric Aging of Biomass Burning Organic Aerosol

Abstract. Biomass burning (BB) is one of the most important contributors to atmospheric aerosols on a global scale, and wildfires are a large source of emissions that impact regional air quality and global climate. As part of the Biomass Burning Observation Project (BBOP) field campaign in summer 2013, we deployed a high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) coupled with a thermodenuder at the Mt. Bachelor Observatory (MBO, ∼  2.8 km above sea level) to characterize the impact of wildfire emissions on aerosol loading and properties in the Pacific Northwest region of the United States. MBO represents a remote background site in the western US, and it is frequently influenced by transported wildfire plumes during summer. Very clean conditions were observed at this site during periods without BB influence where the 5 min average (±1σ) concentration of non-refractory submicron aerosols (NR-PM1) was 3.7 ± 4.2 µg m−3. Aerosol concentration increased substantially (reaching up to 210 µg m−3 of NR-PM1) for periods impacted by transported BB plumes, and aerosol composition was overwhelmingly organic. Based on positive matrix factorization (PMF) of the HR-AMS data, three types of BB organic aerosol (BBOA) were identified, including a fresh, semivolatile BBOA-1 (O ∕ C  =  0.35; 20 % of OA mass) that correlated well with ammonium nitrate; an intermediately oxidized BBOA-2 (O ∕ C  =  0.60; 17 % of OA mass); and a highly oxidized BBOA-3 (O ∕ C  =  1.06; 31 % of OA mass) that showed very low volatility with only  ∼  40 % mass loss at 200 °C. The remaining 32 % of the OA mass was attributed to a boundary layer (BL) oxygenated OA (BL-OOA; O ∕ C  =  0.69) representing OA influenced by BL dynamics and a low-volatility oxygenated OA (LV-OOA; O ∕ C  =  1.09) representing regional aerosols in the free troposphere. The mass spectrum of BBOA-3 resembled that of LV-OOA and had negligible contributions from the HR-AMS BB tracer ions – C2H4O2+ (m∕z = 60.021) and C3H5O2+ (m∕z = 73.029); nevertheless, it was unambiguously related to wildfire emissions. This finding highlights the possibility that the influence of BB emission could be underestimated in regional air masses where highly oxidized BBOA (e.g., BBOA-3) might be a significant aerosol component but where primary BBOA tracers, such as levoglucosan, are depleted. We also examined OA chemical evolution for persistent BB plume events originating from a single fire source and found that longer solar radiation led to higher mass fraction of the chemically aged BBOA-2 and BBOA-3 and more oxidized aerosol. However, an analysis of the enhancement ratios of OA relative to CO (ΔOA ∕ΔCO) showed little difference between BB plumes transported primarily at night versus during the day, despite evidence of substantial chemical transformation in OA induced by photooxidation. These results indicate negligible net OA production in photochemically aged wildfire plumes observed in this study, for which a possible reason is that SOA formation was almost entirely balanced by BBOA volatilization. Nevertheless, the formation and chemical transformation of BBOA during atmospheric transport can significantly influence downwind sites with important implications for health and climate.

[1]  P. Sampson,et al.  Particulate Matter, Ozone, and Nitrogen Species in Aged Wildfire Plumes Observed at the Mount Bachelor Observatory , 2017 .

[2]  M. Facchini,et al.  Direct observation of aqueous secondary organic aerosol from biomass-burning emissions , 2016, Proceedings of the National Academy of Sciences.

[3]  Edward Charles Fortner,et al.  Regional Influence of Aerosol Emissions from Wildfires Driven by Combustion Efficiency: Insights from the BBOP Campaign. , 2016, Environmental science & technology.

[4]  Jian Wang,et al.  Influences of upwind emission sources and atmospheric processing on aerosol chemistry and properties at a rural location in the Northeastern U.S. , 2016 .

[5]  Qi Zhang,et al.  Influences of emission sources and meteorology on aerosol chemistry in a polluted urban environment: Results from DISCOVER-AQ California , 2015 .

[6]  J. Michalsky,et al.  Contributions of dust and biomass burning to aerosols at a Colorado mountain-top site , 2015 .

[7]  G. Evans,et al.  Single-particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium , 2015 .

[8]  A. Laskin,et al.  Molecular transformations of phenolic SOA during photochemical aging in the aqueous phase: competition among oligomerization, functionalization, and fragmentation , 2015 .

[9]  P. Massoli,et al.  Organic aerosol evolution and transport observed at Mt. Cimone (2165 m a.s.l.), Italy, during the PEGASOS campaign , 2015 .

[10]  H. Jonsson,et al.  Impact of wildfires on size-resolved aerosol composition at a coastal California site , 2015 .

[11]  S. Pandis,et al.  Volatility of organic aerosol and its components in the megacity of Paris , 2015 .

[12]  S. K. Akagi,et al.  Observations and analysis of organic aerosol evolution in some prescribed fire smoke plumes , 2015 .

[13]  S. Kreidenweis,et al.  Organic aerosol emission ratios from the laboratory combustion of biomass fuels , 2014 .

[14]  Jim Haywood,et al.  Ground-based aerosol characterization during the South American Biomass Burning Analysis (SAMBBA) field experiment , 2014 .

[15]  P. Palmer,et al.  Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires , 2014 .

[16]  R. Harrison,et al.  Investigating a two-component model of solid fuel organic aerosol in London: processes, PM 1 contributions, and seasonality , 2014 .

[17]  H. Timonen,et al.  Sources of carbonaceous aerosol in the free troposphere , 2014 .

[18]  Edward Charles Fortner,et al.  Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications , 2014 .

[19]  A. Nenes,et al.  Processing of biomass-burning aerosol in the eastern Mediterranean during summertime , 2014 .

[20]  M. Moritz,et al.  Large wildfire trends in the western United States, 1984–2011 , 2014 .

[21]  Scott L. Goodrick,et al.  Wildland fire emissions, carbon, and climate: Wildfire-climate interactions , 2014 .

[22]  Qi Zhang,et al.  Toward Understanding Amines and Their Degradation Products from Postcombustion CO2 Capture Processes with Aerosol Mass Spectrometry , 2014, Environmental science & technology.

[23]  Paulo Artaxo,et al.  Atmospheric aerosols in Amazonia and land use change: from natural biogenic to biomass burning conditions. , 2013, Faraday discussions.

[24]  J. Jimenez,et al.  Secondary organic aerosol formation and primary organic aerosol oxidation from biomass-burning smoke in a flow reactor during FLAME-3 , 2013 .

[25]  Q. Zhang,et al.  Gas-phase CO2 subtraction for improved measurements of the organic aerosol mass concentration and oxidation degree by an aerosol mass spectrometer. , 2013, Environmental science & technology.

[26]  Andrew A. May,et al.  Gas‐particle partitioning of primary organic aerosol emissions: 3. Biomass burning , 2013 .

[27]  D. Jaffe,et al.  Ozone and particulate matter enhancements from regional wildfires observed at Mount Bachelor during 2004–2011 , 2013 .

[28]  K. Prather,et al.  Air quality impact and physicochemical aging of biomass burning aerosols during the 2007 San Diego wildfires. , 2013, Environmental science & technology.

[29]  Qi Zhang,et al.  Primary and secondary organic aerosols in Fresno, California during wintertime: Results from high resolution aerosol mass spectrometry , 2012 .

[30]  Qi Zhang,et al.  Factor analysis of combined organic and inorganic aerosol mass spectra from high resolution aerosol mass spectrometer measurements , 2012 .

[31]  Allen L. Robinson,et al.  Cloud condensation nuclei activity of fresh primary and aged biomass burning aerosol , 2012 .

[32]  Qi Zhang,et al.  Effect of aqueous-phase processing on aerosol chemistry and size distributions in Fresno, California, during wintertime , 2012 .

[33]  D. Jaffe,et al.  Ozone production from wildfires: A critical review , 2012 .

[34]  J. Jimenez,et al.  Evaluation of Composition-Dependent Collection Efficiencies for the Aerodyne Aerosol Mass Spectrometer using Field Data , 2012 .

[35]  Karl Ropkins,et al.  openair - An R package for air quality data analysis , 2012, Environ. Model. Softw..

[36]  A. Weinheimer,et al.  Effects of aging on organic aerosol from open biomass burning smoke in aircraft and laboratory studies , 2011 .

[37]  J. Jimenez,et al.  Understanding atmospheric organic aerosols via factor analysis of aerosol mass spectrometry: a review , 2011, Analytical and bioanalytical chemistry.

[38]  David R. Weise,et al.  Evolution of trace gases and particles emitted by a chaparral fire in California , 2011 .

[39]  Andrew A. May,et al.  Chemical and physical transformations of organic aerosol from the photo-oxidation of open biomass burning emissions in an environmental chamber , 2011 .

[40]  P. DeCarlo,et al.  Investigations of primary and secondary particulate matter of different wood combustion appliances with a high-resolution time-of-flight aerosol mass spectrometer , 2011 .

[41]  D. Blake,et al.  Emissions of Black Carbon, Organic, and Inorganic Aerosols From Biomass Burning in North America and Asia in 2008 , 2011 .

[42]  Jared D. Smith,et al.  Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol. , 2011, Nature chemistry.

[43]  S. K. Akagi,et al.  Emission factors for open and domestic biomass burning for use in atmospheric models , 2010 .

[44]  Stephan Borrmann,et al.  Chemical, physical, and optical evolution of biomass burning aerosols: a case study , 2010 .

[45]  A. Weinheimer,et al.  Investigation of the sources and processing of organic aerosol over the Central Mexican Plateau from aircraft measurements during MILAGRO , 2010 .

[46]  M. Petters,et al.  Cloud condensation nucleation activity of biomass burning aerosol , 2009 .

[47]  Sonia M. Kreidenweis,et al.  Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer , 2009 .

[48]  J. Logan,et al.  Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States , 2009 .

[49]  Douglas R. Worsnop,et al.  Chemically-resolved aerosol volatility measurements from two megacity field studies , 2009 .

[50]  J. D. de Gouw,et al.  Organic aerosols in the Earth's atmosphere. , 2009, Environmental science & technology.

[51]  E. Atlas,et al.  Emissions from biomass burning in the Yucatan , 2009 .

[52]  Gerard Capes,et al.  Aging of biomass burning aerosols over West Africa: Aircraft measurements of chemical composition, microphysical properties, and emission ratios , 2008 .

[53]  R. Martin,et al.  Size-resolved aerosol chemistry on Whistler Mountain, Canada with a high-resolution aerosol mass spectrometer during INTEX-B , 2008 .

[54]  A. Robinson,et al.  Laboratory investigation of photochemical oxidation of organic aerosol from wood fires 2: analysis of aerosol mass spectrometer data , 2008 .

[55]  Martin Mohr,et al.  Organic aerosol mass spectral signatures from wood‐burning emissions: Influence of burning conditions and wood type , 2008 .

[56]  Qi Zhang,et al.  O/C and OM/OC ratios of primary, secondary, and ambient organic aerosols with high-resolution time-of-flight aerosol mass spectrometry. , 2008, Environmental science & technology.

[57]  J. Jimenez,et al.  Interpretation of organic components from Positive Matrix Factorization of aerosol mass spectrometric data , 2008 .

[58]  D. Spracklen,et al.  Interannual variations in PM2.5 due to wildfires in the Western United States. , 2008, Environmental science & technology.

[59]  D. A. N. J. A F F E,et al.  Interannual Variations in PM 2 . 5 due to Wildfires in the Western United States , 2008 .

[60]  H. Burtscher,et al.  An improved low-flow thermodenuder , 2007 .

[61]  Martin Mohr,et al.  Identification of the mass spectral signature of organic aerosols from wood burning emissions. , 2007, Environmental science & technology.

[62]  Masson-Delmotte,et al.  The Physical Science Basis , 2007 .

[63]  Yinon Rudich,et al.  The density of humic acids and humic like substances ( HULIS ) from fresh and aged wood burning and pollution aerosol particles , 2018 .

[64]  Katrin Fuhrer,et al.  Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer. , 2006, Analytical chemistry.

[65]  T. Swetnam,et al.  Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity , 2006, Science.

[66]  D. Jaffe,et al.  Observations of Asian air pollution in the free troposphere at Mount Bachelor Observatory during the spring of 2004 , 2006 .

[67]  A. Stohl,et al.  Volatile organic compounds composition of merged and aged forest fire plumes from Alaska and western Canada , 2006 .

[68]  W. Malm,et al.  Composition of the fine organic aerosol in Yosemite National Park during the 2002 Yosemite Aerosol Characterization Study , 2006 .

[69]  Qi Zhang,et al.  Time- and size-resolved chemical composition of submicron particles in Pittsburgh: Implications for aerosol sources and processes , 2005 .

[70]  D. Streets,et al.  A technology‐based global inventory of black and organic carbon emissions from combustion , 2004 .

[71]  J. Jimenez,et al.  A generalised method for the extraction of chemically resolved mass spectra from aerodyne aerosol mass spectrometer data , 2004 .

[72]  Jim Haywood,et al.  Evolution of biomass burning aerosol properties from an agricultural fire in southern Africa , 2003 .

[73]  R. Draxler.  An Overview of the HYSPLIT_4 Modelling System for Trajectories, Dispersion, and Deposition , 1998 .

[74]  P. Paatero,et al.  Positive matrix factorization: A non-negative factor model with optimal utilization of error estimates of data values† , 1994 .