Effects of Dilution on Biomass Burning Aerosol: Evaporation of Primary Organic Aerosol (BBPOA) and Subsequent Formation of Secondary Organic Aerosol (BBSOA)

TIANCHANG XU, Nara Shin, Yutong Liang, Bin Bai, Dongli Wang, John Allen, Ryan Poland, Zachary McQueen, Omar El Hajj, Chase Glenn, Kruthika Kumar, Anita Anosike, Joseph O'Brien, Andrew Metcalf, Geoffrey Smith, Rawad Saleh, Pengfei Liu, Nga Lee Ng, Georgia Institute of Technology

     Abstract Number: 282
     Working Group: Aerosol Physics

Abstract
Biomass burning is a major contributor of gaseous and particulate carbon in the atmosphere, with significant impact on air quality, health, and climate forcing. Biomass burning events can result in both emission of primary organic aerosol (POA) and formation of secondary organic aerosol (SOA). Previous studies have proposed that dilution-driven BBPOA evaporation and subsequent BBSOA formation can account for up to one third of biomass burning organic aerosol (BBOA) in the atmosphere, in which a higher dilution ratio will lead to a higher potential of BBSOA formation from BBPOA. However, the chemical composition of the evaporated BBPOA and subsequent BBSOA is not well characterized owing to the chemical complexity of biomass burning plumes. In this work, we systematically investigate the relationship between BBPOA evaporation and BBSOA formation in the Georgia Wildland-fire Simulation Experiment (G-WISE) campaign. The G-WISE campaign involved burning fuel beds constructed using forest floors and surface fuels collected from three ecoregions in Georgia. The biomass burning aerosol is diluted with a dilution ratio of 3:1 to 15:1 and then passed through an oxidation flow reactor (OFR) to allow for measurement of both fresh POA (lights off condition) and SOA (lights on condition). The chemical composition of OA is measured by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a Filter Inlet for Gases and AEROsol (FIGAERO) inlet system coupled with an iodide HR-ToF-CIMS. It appears that higher dilution ratios lead to increased prevalence of organic acid (e.g., glycolic acid and lactic acid) and phenol derivative (e.g., syringic acid) in BBSOA, indicating the role of dilution ratio on SOA formation pathway. Results from this study highlight the complexity in the evolution of BBOA, especially on BBPOA fate and BBSOA formation pathway.