AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Estimating Volatility Distributions of Primary Organic Aerosols Using Artifact-Corrected Quartz Filters
Alexandra Ng, Hanyang Li, ANDREW MAY, The Ohio State University
Abstract Number: 139 Working Group: Carbonaceous Aerosol
Abstract Recent studies have estimated volatility distributions to represent primary organic aerosol (POA) of some combustion sources (on-road vehicles, open biomass burning), and these volatility distributions have been implemented into chemical transport models for the simulation of regional air quality. However, the derivation of these distributions based on empirical observations may be challenging for other sources. For example, some of the previous work utilized sampling and analytical techniques that may be less readily available, including a thermodenuder/aerosol mass spectrometer system, thermal desorption-gas chromatography-mass spectrometry, and/or complex kinetic models of the observed aerosols. In this study, we investigate the feasibility of estimating volatility distributions from these sources using bare quartz and quartz-behind-Teflon (QBT) filters analyzed by a thermal-optical technique; the combination of bare quartz and QBT enables the correction of the filters for positive sampling artifacts.
We include both open biomass burning samples collected at the Fire Sciences Laboratory in Missoula, MT and light-duty gasoline vehicle (LDGV) samples collected at the Haagen-Smit Laboratory in El Monte, CA. Assuming both gas/particle equilibrium and sample-air-stream/filter equilibrium, we apply the equilibrium volatility basis set approach to derive volatility distributions for both sources. We observe some discrepancies with the biomass burning samples (likely because those experiments were not designed to study organic carbon), specifically under more dilute conditions. However, applying this approach to the LDGV samples results in good agreement with published results. This finding has important implications for the derivation of volatility distributions for other POA sources (e.g., cooking) that are currently unrepresented in the transport models, given that the collection and analysis of quartz filters for organic carbon is something of a standard practice for most source testing.