Influence of selected cationic, anionic, and nonionic surfactants on hygroscopic growth of individual aqueous coarse mode aerosol particles

The properties of surfactants and their specific role in the hygroscopic growth and evaporation of coarse mode aqueous aerosol particles is still unknown. Here we show that the properties of surfactants within individual, coarse mode aerosol particles, especially ionicity, affect their hygroscopic growth. The hygroscopic growth of individual aqueous particles was measured with an Aerosol Optical Trap combined with Raman spectroscopy. Aqueous particles containing both NaCl and nonionic surfactants showed a statistically significant increase of up to 3% in hygroscopic growth from that of pure aqueous NaCl particles. However, no statistically significant deviations were observed in particles with NaCl and anionic or cationic surfactants. This work demonstrates that the type of the surfactants and their properties, including the charge of their polar head group and associated molecular weight, controls their influence on particle hygroscopic growth. The properties of surfactants in aerosol particles need to be considered when predicting the hygroscopic growth of coarse mode aerosol particles.Copyright (c) 2022 American Association for Aerosol Research