The influence of surfactant properties on critical supersaturations of cloud condensation nuclei

Due to the complex nature of atmospheric surfactants, their effect on cloud droplet formation is still quite unknown. Most of the earlier studies of surface tension effects on cloud formation have been done either with model compounds or by neglecting the correct thermodynamic approach thereby giving no general idea of how the partitioning of surfactant between the droplet interior and the surface layer affects droplet growth. The neglect of partitioning leads to overestimated decrease in surface tension as well as to enhanced solute effect. Here, we study the extent to which surfactant partitioning affects critical supersaturation with different types of surfactants. The idea is to systematically vary the surface tension parameters that ultimately control how the surfactant is distributed between the bulk and the surface of the droplet, and to compare the critical supersaturations calculated with and without account of the partitioning. This study shows the importance of correct thermodynamical approach to partitioning with an example of three different classes of compounds found in atmospheric aerosols.