AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Measuring the Atmospheric Organic Aerosol Volatility Distribution: A Theoretical Analysis
ELENI KARNEZI, Ilona Riipinen, Spyros Pandis, Carnegie Mellon University
Abstract Number: 328 Working Group: Aerosol Physics
Abstract Organic compounds represent a significant fraction of the atmospheric aerosol mass. Even if most of these compounds are semi-volatile in atmospheric concentrations, the ambient organic aerosol volatility is quite uncertain. Understanding the partitioning between gas and aerosol phases has been recognized as one of the major challenges in our effort to quantify the rates of formation and atmospheric fate of organic particulate matter. The most common volatility measurement method relies on a thermodenuder (TD). The aerosol passes through a heated tube where its more volatile components evaporate leaving the less volatile behind in the particulate phase. The typical result of a thermodenuder measurement is the mass fraction remaining (MFR), which depends among other factors on the organic aerosol (OA) vaporization enthalpy and the accommodation coefficient. We use a new method combining forward modeling, introduction of ‘experimental’ error and inverse modeling with error minimization for the interpretation of existing TD measurements. We try to estimate simultaneously the OA volatility distribution, its effective vaporization enthalpy and the mass accommodation coefficient; we calculate the uncertainty range of each property and show that existing TD-based approaches cannot estimate reliably the OA volatility distribution. We propose an improved method, using both TD and isothermal dilution measurements. We evaluate this experimental approach using the same model and show that it is suitable for studies of OA volatility in the lab and the field.