The size and composition of atmospheric aerosol particles modulate their interactions with solar radiation, and thus affect their influence on climate and visibility. The radiative effects of aerosol particles remain a large uncertainty in accurately modeling and predicting current and future climates. Sea spray aerosol particles are a significant fraction of particle mass in the atmosphere, and their hygroscopic growth is dependent on their size as well as the hygroscopicity of their sea salt and organic fractions. Recent work has demonstrated the presence of surfactant molecules in sea spray aerosol particles, in both submicron and supermicron sizes. The role of different surfactants in the hygroscopic properties of coarse mode aqueous aerosol particles is still unknown. Here we show that the properties of surfactants within individual, coarse mode aqueous NaCl particles, including size, structure, and ionicity, affect particle hygroscopic growth, compared to that of particles containing pure NaCl. The hygroscopic growth of individual particles was measured with an Aerosol Optical Trap combined with Raman spectroscopy. Particles containing both NaCl and large, nonionic surfactants showed an increase in hygroscopic growth from that of pure aqueous NaCl particles by up to 3%. However, this deviation was not observed in aqueous NaCl particles containing anionic or cationic surfactants, suggesting different electrostatic interactions between the different surfactants and the NaCl ions in solution. This work demonstrates that the charge of the surfactant polar head group controls the influence on particle hygroscopic growth.

Surfactant properties influence hygroscopic growth of individual aqueous coarse mode NaCl particles

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.