CCN activity of thermodenuded aerosol particles downwind of the Sacramento area urban plume

This study focuses on the characterization of cloud condensation nuclei (CCN) properties of aerosol particles measured during the Carbonaceous Aerosols and Radiative Effects Study (CARES) near Sacramento, CA in June 2010. Supersaturation-dependant CCN activity (0.07 - 0.5% supersaturation) was measured with DMT CCN counters at two locations; one near the city center (T0) and the other in Cool, CA, a small town located ~40 kilometers downwind of the urban plume in the Sierra Nevada foothills (T1). The T1 CCN counter was operated behind a thermodenuder to study volatility-dependant CCN activity of the urban aerosol plume as it was transported into the biogenically influenced foothills. Preliminary analysis indicated that activated fraction was inversely proportional to the thermodenuder temperature, suggesting that the more-volatile fraction of the aerosol might have played an important role in the CCN activity of the aerosol. The relationship between the chemical composition and CCN activity of the aerosol will be discussed. The physical and chemical transformations of particles aged in the foothills as well as the diurnal profiles of CCN both at T0 and T1 will also be discussed for the transport event of 15 June 2010.