Reactive uptake of NO by atmospheric aerosol is dominated by interfacial processes.

Nitrogen oxides are removed from the troposphere through the reactive uptake of NO into aqueous aerosol. This process is thought to occur within the bulk of an aerosol, through solvation and subsequent hydrolysis. However, this perspective is difficult to reconcile with field measurements and cannot be verified directly because of the fast reaction kinetics of NO Here, we use molecular simulations, including reactive potentials and importance sampling, to study the uptake of NO into an aqueous aerosol. Rather than being mediated by the bulk, uptake is dominated by interfacial processes due to facile hydrolysis at the liquid-vapor interface and competitive reevaporation. With this molecular information, we propose an alternative interfacial reactive uptake model consistent with existing experimental observations.