Observational Constraints on the Total Contributions of Biomass Burning to Ambient Organic Aerosol
MITCHELL ROGERS, Taekyu Joo, Lijin Zhang, Tori Hass-Mitchell, Benjamin Murphy, Ziheng Zeng, Theobard Habineza, Abhishek Anand, Dexter Resta, Catelynn Soong, Albert Presto, Havala Pye, Drew Gentner, Yale University
Abstract Number: 206
Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene
Abstract
Biomass burning represents a growing, yet uncertain source of primary and secondary organic aerosol globally. Despite this, source apportionment of organic aerosol mass spectrometry data alone risks underestimating organic aerosol attributable to biomass burning (BBOA). These challenges occur, in part, because oxidative aging diminishes characteristic spectral peaks of BBOA (i.e., m/z 60, 73; levoglucosan fragments), rendering it less distinguishable from other oxygenated organic aerosol with elevated signal at m/z 44 (e.g., organic acids). With tropospheric aerosol lifetimes of several days, biomass burning emissions can travel long distances and originate from a range of combustion sectors (e.g., wildfires, residential wood combustion) and types (e.g., smoldering, flaming). Since potassium is one of the most abundant metals in biomass burning emissions and remains present after transport and oxidative aging, it has utility as a quantitative tracer for biomass burning organic aerosol. The objective of this study is to provide observational constraints on the total contributions of biomass burning to organic aerosol. Specifically, we leverage multiple years of chemically resolved PM2.5 measurements from two ASCENT (Atmospheric Science and Chemistry mEasurement NeTwork) sites alongside filter measurements to isolate biomass burning potassium from other potassium sources through multiple methods, including both positive matrix factorization of metals data as well as application of derived dust emissions profiles. We then utilize a distribution of biomass burning organic aerosol and potassium emissions ratios derived from literature and recent field measurements to estimate the total contributions of biomass burning to organic aerosol (TBBOA), which presents as an accessible and transferrable method. Additionally, backward air mass trajectories and the Community Multiscale Air Quality modeling system (CMAQ) are used to isolate wildfire and non-wildfire contributions to TBBOA and evaluate their spatiotemporal variations. Lastly, we assess how our top-down quantification of TBBOA compares to model predictions and other source apportionment approaches.