AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Quantifying Organic Matter and Functional Groups in Aerosol Filter Samples from the Southeastern Aerosol Research and Characterization (SEARCH) Network
ALEXANDRA BORIS, Satoshi Takahama, Andrew Weakley, Bruno Debus, Stephanie L. Shaw, Eric Edgerton, Ann Dillner, University of California, Davis
Abstract Number: 369 Working Group: Carbonaceous Aerosol
Abstract A broad view of atmospheric aerosol organic matter (OM) composition is afforded by Fourier transform infrared (FT-IR) spectrometry of filter-based samples. Infrared absorption patterns and multivariate calibration efficiently quantifies OM and functional group quantities on individual samples. Teflon filter samples are analyzed quickly and without damage, enabling application to air monitoring networks as well research campaigns. This methodology is an improvement over OM calculated by converting routinely measured organic carbon (OC) concentrations to OM using a constant OM/OC ratio.
This work discusses the contribution of functional groups to OM, as well as total OM concentration, directly measured within samples from the Southeastern Aerosol Research and Characterization (SEARCH) network. The study expands upon previous work to include particle water, additional oxygenated chemical standards, and improved functional group specificity (e.g., addition of carboxylates). The ~5400 SEARCH samples collected over eight years (2009-2016) allow contrast between urban and rural compositions, between months, and over a long time period. Preliminary results demonstrate that FT-IR spectrometry measured composition matches that from other techniques, including in the van Krevelen space and relative to residual OM (calculated using aerosol mass balance from network measurements). Long-term trends are observed in OM concentration and composition, as are seasonal differences in OM degree of oxidation. This work is a step toward quantifying all major functional groups and evaluating variability of total OM composition.