How efficient is cloud droplet formation of organic aerosols?

Based on laboratory findings that small amounts of a soluble aerosol, such as ammonium sulfate ( AS), drastically decrease the activation diameter of moderately soluble organic aerosols, we performed studies with an adiabatic parcel model for cloud droplet nucleation. Moderately soluble organics, such as adipic acid ( AA), which represents a class of partially soluble aerosols as found in atmospheric aerosols, require a larger supersaturation and result in fewer cloud droplets as compared to pure AS and vice versa when compared to a completely insoluble species such as dust. Adding only 10% AS to AA dramatically increases its ability to become activated resulting in 36 - 92% of the cloud droplets that would be obtained from pure AS, whereas the droplet concentration in the almost pure AA aerosol is only 11 - 47% of that of AS. Addition of a surface active species, such as nonanoic acid, instead of AS to AA reduces its activated fraction by 3 - 34% as compared to the AA/AS system.