AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Determination of Accommodation Coefficients for Organic Aerosol with Thermodenuder Measurements
JAMES HITE, Tianyu Shi, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 391 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Thermodeunders (TD) are commonly used in laboratory and ambient studies of aerosols to provide information about aerosol volatility. These uses range from qualitatively separating relatively volatile from relatively nonvolatile fractions of the sampled aerosol to quantitatively determining properties that describe the volatility and/or evaporation kinetics behavior of an aerosol sample. When utilized for the latter purpose, the data are often interpreted with a model of the aerosol evaporation kinetics within the TD – outside of conditions where a simplified treatment of the aerosol response within the instrument can reliably be deployed (i.e. the “thermodynamic” versus “kinetic” limits). These kinetic models require information about the aerosol accommodation (or evaporation) coefficient (alpha), often treated as a representation of all kinetic limitations to aerosol evaporation, and typically assume a value of unity.
In light of more recent developments in research concerning secondary organic aerosol (SOA), the likelihood that SOA can exhibit characteristics that would act as kinetic limitations to volatilization (alpha < 1) presents a challenge for the interpretation of data collected with TDs and demonstrates the need for experimental methods to probe this critical unknown. Although some work has been done to constrain α for ambient aerosol, current approaches come with considerable limitations (e.g., long measurement timescales required) that prohibit their use in rapidly varying environments found in airborne measurements and environmental chamber experiments. We present here a combined measurement and modeling strategy that can be utilized to constrain alpha independently of the aerosol thermodynamic properties by probing the response of laboratory-generated aerosol to a variety of instrument conditions.