The effects of specific properties of surfactants on the hygroscopic growth of supermicron aerosol in the atmosphere are not well understood. Nonionic surfactants have been shown to enhance aqueous aerosol water uptake, but further investigation is needed to determine the role of the specific properties of the nonionic surfactants, including molecular composition, structure, topological surface area, and surface tension. In this study, we investigate the hygroscopic growth of aqueous supermicron NaCl aerosol particles containing small fractions (<3-6% of dry particle mass) three nonionic surfactants with different properties using an Aerosol Optical Trap coupled with cavity-enhanced Raman spectroscopy. The dynamic surface tensions of corresponding solutions were measured with a Bubble Pressure Tensiometer. Here, we show that all nonionic surfactants in this study contributed to more particle hygroscopic growth, compared to that of particles with NaCl only. This degree of enhanced hygroscopic growth was dependent on the concentration of the nonionic surfactant but did not vary significantly with different surfactant molecular compositions, as did the dynamic surface tension. Additionally, when a small fraction (<3-6% of dry particle mass) of the water-soluble organic glucose was added to the particles with surfactant and NaCl, the hygroscopic growth decreased to that of the NaCl only particles, essentially removing any influence of the surfactants. Alone, this small fraction of glucose would not change the hygroscopic growth of NaCl particles. Together, this shows that it is important to take into account the total composition of the particle when modeling supermicron particle hygroscopic growth.
