Abstract Number: 274 Working Group: Aerosol Physics
Abstract The volatility distribution of complex organic aerosol can be better constrained combining thermodenuder and isothermal dilution measurements (Karnezi et al., 2014). Smog chamber experiments were conducted in the FORTH Laboratory of Air Quality studies using organic aerosol produced during meat charbroiling. The emissions were then fed in a 10 m$^3 chamber filled with clean air. The thermodenuder was operated at a temperature range from 25 to 250$^oC with a 16 s centerline residence time coupled to a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS) and a Scanning Mobility Particle Sizer (SMPS). In parallel, a smaller chamber (~1 m$^3) filled with clean air was used to dilute isothermally the aerosol of the larger chamber facility by approximately a factor of 10. The evolution of the OA size distribution in the smaller chamber was followed using an SMPS. The measurements in both systems were corrected for the size-dependent wall losses. The OA mass fraction remaining was measured as a function of temperature in the thermodenuder and as a function of time in the dilution chamber. These two sets of measurements were then used together with the approach of Karnezi et al. (2014) to estimate the volatility distribution of the OA and its effective enthalpy of vaporization.
In most of the isothermal dilution experiments 20-30% of the aerosol mass evaporated at ambient temperature after approximately an hour. In the thermodenuder almost all the organic aerosol evaporated at 200$^oC. The resulting volatility distribution suggests that 20% of the cooking OA consisted of extremely low volatility organic compounds, 65% of low volatility compounds, and the remaining 15% of semi-volatile organic compounds.