Deriving aerosol hygroscopic mixing state from size-resolved CCN activity and HR-ToF-AMS measurements

Despite the large differences between κ measured from two approaches, less over-prediction (up to 18%) between measured and predicted CCN concentration suggested lower impact of chemical composition and mixing state at higher SS. However, at lower SS, presences of externally mixed CCN-inactive aerosols lead to CCN over-prediction reflecting the significance of aerosol mixing state information. Further examination of the effect of biomass burning aerosols (∼35% in least oxidized biomass burning organic aerosol (BBOA-2 fraction) on hygroscopicity and CCN activity showed increase in the concentration of all AMS measured species (except NH4+ and SO42−), less O:C ratio, and organic mass fraction (forg) peak shift to lower diameter range caused ∼13% change in critical diameter (Da) and ∼40% change in κCCN. Increased deviation of ∼100% between κCCN and κAMS due to sudden influx of internally mixed BBOA caused suppressed hygroscopic growth. This study finally suggests the assumption of pure internally mixed aerosol does not completely hold true for this anthropogenically polluted site.