AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Molecular Characterization of Water-Soluble Organic Carbon (WSOC) from Biomass Burning of Wildland Fuels Using Ultrahigh Resolution Orbitrap Elite Mass Spectrometry
Elena Kirillova, Vera Samburova, Chiranjivi Bhattarai, Deep Sengupta, Hans Moosmuller, Andrey Khlystov, LYNN MAZZOLENI, Michigan Tech
Abstract Number: 222 Working Group: Aerosol Chemistry
Abstract Wildland biomass burning is an important source of water-soluble organic carbon (WSOC) to the atmosphere contributing to climate change, reductions in visibility, and adverse human health affects. In this study, we focused on five globally important fuels: Alaskan, Russian, and Florida swamp peat, cheatgrass, and Ponderosa Pine needles. Aerosol from laboratory controlled combustion experiments was collected on filters and extracted in HPLC grade water. Ultrahigh resolution electrospray ionization mass spectrometry and light absorption measurements were performed after sequential solid-phase extraction (SPE) using Strata-X and HyperSep Hypercarb SPE cartridges. This was done to remove inorganic components and to pre-concentrate acidified WSOC components. The SPE cartridges were eluted twice: first, with methanol and water (90:10); second, with methanol containing 1% of aqueous ammonia. Over 2000 molecular formulas were assigned in the negative ion mass spectra of WSOC from each fuel. CHO compounds were dominant followed by CHNO, CHOS, and CHNOS compounds. In all cases, the reversed phase Strata-X cartridges retained the majority of the organic anions; the greater part of which was eluted during the first elution, while the larger, less oxidized, more aromatic molecules with lower average O/C and H/C ratios were eluted with the alkaline methanol elution. Only 25-36% of the assigned formulas were common for both elutions. We observed Absorption Ångström Exponents (AAE) of 10.4-15.2 for the first elution and 6.7-8.8 for the second elution, indicating clear differences in the light absorbing properties of WSOC in the two Strata-X elutions. The Hypercarb SPE cartridge retained the smaller, more polar and non-light absorbing molecules not captured by the Strata-X cartridge. Overall, most of the assigned molecular formulas demonstrated low O/C ratio (< 1) typical for fresh biomass combustion aerosols. Larger similarity was observed in peat burning aerosol samples compared to aerosol of other fuel types.