Shedding light on water structure at air-aqueous interfaces: ions, lipids, and hydration.

An account is given of the current state of understanding of aqueous salt, acid, and lipid/water surfaces, interfacial depth, and molecular organization within the air-solution interfacial region. Water structure, hydration, surface propensity of solutes, and surface organization are discussed. In this perspective, vibrational sum frequency generation spectroscopic studies of aqueous surfaces are interpreted. Comment on future directions within the field of aqueous surface structure is provided.