Abstract View
Quantification of Organic Aerosol Evaporation Rates in Aircraft Inlets and Instruments
DEMETRIOS PAGONIS, Benjamin A. Nault, Pedro Campuzano-Jost, Hongyu Guo, Jason Schroder, Douglas Day, Jose-Luis Jimenez, University of Colorado-Boulder
Abstract Number: 417
Working Group: Aerosol Chemistry
Abstract
The semivolatile character of part of the organic aerosol (OA) can lead to aerosol evaporation in sampling systems. This can be especially important during aircraft measurements, where there is often significant warming of the air upon entering the inlet system in the cabin. We have carried out quantitative airborne measurements of aerosol evaporation rates using an Aerodyne Aerosol Mass Spectrometer (AMS), and a thermodenuder. These measurements were carried out aboard the NASA DC-8 aircraft during the KORUS-AQ and FIREX-AQ studies, and aboard the NSF/NCAR C-130 during the WINTER study. During those studies the temperature difference between ambient air and the OFR ranged from 10–30 K, and the OA mass fraction remaining (MFR) ranged from 0.68–0.83. We analyze these results using an established kinetic model of aerosol evaporation, and published volatility basis sets. The model reproduces the OA evaporation within 15% error across the three studies, and thus provides unique information on ambient aerosol volatility aloft. We perform case studies of OA evaporation inside inlets where charcoal denuders are used to remove VOCs, which are applicable to the extractive electrospray ionization mass spectrometry (EESI) measurements made during FIREX-AQ. For the EESI inlet (residence time was 1.6 s, charcoal denuder) we estimate significant evaporative loss inside the inlet (MFR > 0.7). AMS inlet residence times are sufficiently short to minimize OA evaporation (MFR > 0.99 KORUS-AQ and WINTER; MFR > 0.95 FIREX-AQ). Finally, we explore the evaporative losses when black conductive tubing (which acts as a denuder) is used in an inlet.