AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Functional Group Analysis of Wildfire-Influenced Free Tropospheric Organic Aerosol using Ultrahigh Resolution Tandem Mass Spectrometry
SIMEON SCHUM, Claudio Mazzoleni, Bo Zhang, Paulo Fialho, Lynn Mazzoleni, Michigan Technological University
Abstract Number: 596 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract A comprehensive ultrahigh resolution tandem mass spectrometry (MS/MS) analysis was performed on wildfire-influenced organic aerosol collected in the free troposphere at the Pico Mountain Observatory. This analysis revealed an unprecedented level of complexity within a single sample of organic aerosol and provided information regarding the polar functional groups present. Using a segmented scanning approach for the analysis of unfragmented precursors, over 9000 individual monoisotopic molecular formulas were identified in the range of m/z 150-500. This represents nearly 4 times more molecular formulas than previously identified within the same mass range using a full scan approach. The increased number of molecular formulas yielded a higher proportion of nitrogen-containing and aromatic molecular formulas. Of the over 9000 identified species, roughly 7000 were observed to have detectable neutral losses representing polar functional groups. The most abundant neutral losses represented carboxyl, hydroxyl, and carbonyl functional groups. Additionally, there were a surprising number of reduced nitrogen and sulfur containing losses as well. The prevalence of carbonyl groups in addition to the reduced nitrogen and sulfur supports a relatively low extent of oxidation for free tropospheric organic aerosol relative to boundary layer organic aerosol. Additionally, the multifunctional nature and isomerization of organic aerosol species is highlighted by the presence of multiple neutral losses for single molecular formulas. Using principal components analysis, neutral losses were attributed to different molecular characteristics (e.g., aromaticity, oxidation, etc.). Thus, novel relationships between neutral loss type and estimated aromaticity were established. This study represents the first comprehensive functional group analysis of organic aerosol using mass spectrometry. The results have implications for molecular structure and modeling studies involving functional groups in aerosol species.