Abstract View
Airborne Extractive Electrospray Mass Spectrometry (EESI) Measurements of the Chemical Composition of Biomass Burning Organic Aerosol
DEMETRIOS PAGONIS, Pedro Campuzano-Jost, Hongyu Guo, Douglas Day, Melinda Schueneman, Wyatt Brown, Benjamin A. Nault, Kyla Siemens, Alexander Laskin, Felix Piel, Laura Tomsche, Tomas Mikoviny, Armin Wisthaler, Jose-Luis Jimenez, University of Colorado-Boulder
Abstract Number: 537
Working Group: Instrumentation and Methods
Abstract
Fast quantification of organic aerosols (OA) at near-molecular level is necessary to quantify its sources, evolution, and fate. To that end, we carried out airborne extractive electrospray time-of-flight mass spectrometry (EESI) measurements of OA composition during the 2019 FIREX-AQ mission on the NASA DC-8. We demonstrate fast EESI response to spatial gradients within wildfire smoke plumes, allowing for 1-Hz quantification of individual components of OA. The EESI was operated with positive and negative ion polarity during different flights, and we report aerosol levoglucosan concentrations for EESI(+) operation, and nitrocatechol for EESI(-). Attribution of EESI signal to these compounds is supported by offline analysis of FIREX-AQ aerosol filter extracts using liquid chromatography coupled to ultra-high-resolution electrospray ionization mass spectrometry. We present the first in-field intercomparison of co-located EESI, Aerodyne high-resolution Aerosol Mass Spectrometer (AMS), and CHemical Analysis of aeRosol ONline Proton-Transfer Reaction Mass Spectrometer (CHARON PTR-MS) during a single FIREX-AQ flight. We developed methodology to allow for stable EESI quantification up to altitudes of 7 km, including optimization of the electrospray working solution for low-pressure operation, control of electrospray region pressure, and pre- and post-flight calibrations in parallel with an AMS. The effect of electrospray region pressure, particle diameter, and particle composition on EESI sensitivity were systematically investigated and are described here. EESI quantification was stable flight-to-flight within 60% (1 σ), and calibrations using the same electrospray hours apart were stable within 20% (1 σ), showing the importance of calibrating EESI response for each electrospray established. Using the EESI measurements of levoglucosan and nitrocatechol and AMS measurements of total OA, we show evidence for balanced rates of primary OA evaporation and secondary OA formation during aging of wildland fire smoke aerosol.