EFFECTS OF CHEMICAL COMPOSITIONS ON CLOUD FORMATION POTENTIAL OF AMINIUM CARBOXYLATE AEROSOLS

Atmospheric aerosols impact weather, climate, visibility, air quality, and human health. Previous studies have investigated the effects of relative humidity (RH) and chemical composition on the physicochemical properties of aerosols including the hygroscopicity parameter (k or kappa) for single and multicomponent organic and inorganic aerosols. In this paper, aminium salt aerosols consisting of four different weak organic acids including cis-pinonic, p-toluic, oxalic, and succinic acid mixed with dimethylamine were generated with an excess acidic content, and their hygroscopicity and cloud condensation nuclei (CCN) activity were measured, utilizing a CCN counter and a Tandem Differential Mobility Analyzer (TDMA) coupled to a Condensation Particle Counter (CPC) for size-selected particles. Hygroscopic Growth Factors (HGF) were measured at a variety of relative humidities ranging from 30% to 90%. Kappa values for all four systems were calculated from both HGF and CCN, and compared to the measured (k) values for stoichiometrically neutral aerosols. Our results indicate that aminium salt aerosols with a higher acid content result in higher k values than those of single component aerosols but less than those of stoichiometrically neutral aerosols. The atmospheric implications of our measurements on the effect of changing chemical composition on aerosol hygroscopicity and CCN activity will be discussed.