Ions at the Air/Water Interface

Thermodynamic analysis suggests that ions tend to be excluded from the air/water interface in simple salt solutions. In his Perspective, Garrett reviews recent molecular dynamics simulations and experimental studies that provide evidence to the contrary: Ions are found at the interface, sometimes even at enhanced concentrations. The author explains how this new picture may be reconciled with the thermodynamic observations. Ions in the surface layer are likely to play an important role in atmospheric reactions involving aerosol particles.