Enrichment of Surface-Active Compounds in Bursting Bubble Aerosols

The pronounced enrichment of surface-active compounds in the aerosols produced by bubble bursting plays a central role in the chemical transfer from the ocean into the atmosphere and has an important impact on the global Earth's climate. However, the mechanism of chemical enrichment in bursting bubble aerosols remains poorly understood and controversial due to the high complexity and diversity of experimental behaviors. Contrary to the common belief, here we show that the major share of surfactants in the jet droplets produced by individually bursting bubbles at a calm solution surface is released directly from the bubble surface rather than from the solution surface or subsurface microlayer. We reveal that surfactants are accumulated at the surface of a rising bubble in solution following three successive stages with strongly distinct adsorption profiles: linear kinetic, mixed kinetic, and equilibrium. The magnitude of surfactant enrichment in the aerosol is directly determined by which adsorption mode is in control by the moment of the bubble bursting at solution surface. Our mechanistic description explains the diversity of experimental observations regarding the surfactant enrichment in aerosol droplets and lays the ground for understanding the more complex behaviors associated with collective effects at the solution surface (e.g., breaking waves).