Oxidation of Eucalyptus Biomass Burning Emissions by Hydroxyl Radical in Cloud Water Mimics and Implications to Secondary Organic Aerosol
VIVIAN CAMPBELL, Haley Royer, Megan McRee, Marc Fiddler, Cade Christensen, Solomon Bililign, Jason Surratt, Barbara Turpin, University of North Carolina at Chapel Hill
Abstract Number: 135
Working Group: Burning Questions of Aerosol Emissions, Chemistry, and Impacts from Wildland-Urban Interface (WUI) Fires
Abstract
Biomass Burning (BB) emissions are a substantial source of aerosol, including brown carbon (BrC), a form of light-absorbing organic aerosol that impacts radiative forcing. Previous research has demonstrated that water-soluble organic gases (WSOGs) present in BB emissions can form secondary organic aerosol through cloud processing, yet cloud processing of BB emissions remains poorly understood. Eucalyptus camaldulensis is a prevalent fuel on several continents. Using Eucalyptus camaldulensis from sub-Saharan Africa, we investigated the transformation of WSOGs through cloud water oxidation experiments, focusing on reactions with OH radicals. The combustion of Eucalyptus camaldulensis under smoldering conditions in an indoor smog chamber at NCA&T University generated smoke for the collection of WSOGs via mist chamber samplers (MCS). A MCS blank was collected before two 20-minute sampling periods. Samples and blanks were analyzed using a Total Organic Carbon (TOC) analyzer and aliquots were placed into quartz cuvettes for oxidation in an aqueous chemistry reactor. Both MCS samples and a blank MCS aliquot were exposed to ~10-12 M hydroxyl radicals produced through photolysis of 500 μM H2O2 by a 254 nm ultraviolet (UV) lamp. Control experiments included exposing samples to H2O2 only and UV only. A time-series of 14 samples removed from the reactor during each experiment was analyzed using ion chromatography to determine the presence of soluble small chain organics. To determine the overall chemical composition and optical properties of samples, we used reverse-phase liquid chromatography interfaced to diode array detection and electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (RPLC/DAD-ESI-HR-QTOFMS). Results are used to identify WSOGs for further study, with a focus on compounds that are potentially important precursors for secondary organic aerosol formation via cloud processing and to stimulate hypotheses relevant to BrC.