The chemical composition of surface snow and rime ice has been measured in a winter mountain setting for the purpose of identifying the principal scavenging mechanisms. The sitting permitted the results to be interpreted with minimal consideration of below-cloud scavenging processes and close comparison of the snow and rime ice compositions. The concentrations of all major ions in the snow were well below those in the rime ice and could be related to the estimated degree of snow crystal riming. The results of this study support the two-step concept of wet removal, in which atmospheric pollutants are first incorporated into cloud droplets and then removed from the cloud through the hydrodynamical collection of the droplets by falling precipitation elements. Under some meteoroglogical conditions, therefore, it is likely that pollutant removal from the atmosphere is mechanistically limited by the removal of cloud water. ¿ American Geophysical Union 1989