A single-parameter hygroscopicity model for functionalized insoluble aerosol surfaces

Abstract. The impact of molecular level surface chemistry for aerosol water-uptake and droplet growth is not well understood. In this work, spherical, nonporous, monodisperse polystyrene latex (PSL) particles treated with different functional groups are exploited to isolate the effects activation. PSL effectively water insoluble changes in particle may be considered a critical factor initial uptake water-insoluble material. two modified types (PSL-NH2 PSL-COOH) along plain was measured supersaturated environment Cloud Condensation Nuclei Counter (CCNC). Three models – traditional Köhler (TK), Flory–Huggins (FHK) Frenkel–Halsey–Hill adsorption theory (FHH-AT) were compared experimental data. experimentally determined single hygroscopicity parameter, ?, found within range from 0.002 0.04. prediction assumes Raoult's law solute dissolution underestimates ability particles. FHK can applied polymeric aerosol; however, that polymer soluble hydrophilic. Thus, model generates negative result hydrophobic predicts non-activation behavior disagrees observation. FHH-AT fit empirical parameters (AFHH BFHH). agrees data differentiate owing modification surface. PSL-NH2 exhibits slightly higher than PSL-COOH, whereas least hygroscopic among three. This consistent polarity their affinity molecules. AFHH BFHH quantified when isolated study water-uptake. fitted PSL-NH2, 0.23, 0.21, 0.18 unity. To simplify use cloud activation models, we also present test new parameter framework compounds, ?FHH. ?FHH 5 % agreement describe single-parameter properties.