Hygroscopic growth and collision studies of atmospheric aerosols across scaled particle sizes

Abstract

In this paper, the hygroscopic growth and collision evolution of ammonium sulfate droplets are calculated at both the continuum and transition regime scales, and the results show that the variation of particle size across the scales will have a significant effect on the direction and degree of hygroscopic evolution of particles as well as the number of new particles generated by collision. At the continuum regime scale, solute effects determine whether water vapor condenses on the particle surface or escapes into the atmosphere. At the transition regime scale, curvature effects will result in an 80% overestimation of the hygroscopic growth of ammonium sulfate droplets and a threefold increase in the time to reach hygroscopic equilibrium. Collision results show that the droplet concentration decreased by 97% for 25 nm droplets, and increased by 13% for 250 nm droplets, which suggests that small droplets are more influenced by collision.