Date Published:

NOV 20

Abstract:

Collisions of the gaseous hydroxyl (OH) radical and ozone (O-3) with the surfaces of sodium chloride or iodide solutions, as well as with the surface of neat water, were investigated by molecular dynamics simulations. The principal intent was to answer atmospherically relevant questions concerning the trapping and accommodation of the OH and O-3 species at the surface and their uptake into the bulk solution. Although trapping is substantial for both species, OH adsorbs and absorbs significantly better than O-3. Most of the trapped O-3 molecules desorb from the surface within 50 ps, whereas a significant fraction of OH radicals remains at the interface for time intervals exceeding 100 ps. The aqueous surface has also an orientational effect on the OH species, favoring geometries with the H atom pointing toward the aqueous bulk. The effect of the dissolved salt on the trapping efficiency is minor; therefore, most likely, atomic ions solvated in aqueous aerosols do not act as strong scavengers of reactive gases in the atmosphere. However, frequent and relatively long contacts between the adsorbed molecules and halide anions do occur, allowing for heterogeneous atmospheric chemistry in the interfacial layer.