Sulfur dioxide incorporation into ice depositing from the vapor

An experimental study has been made of the incorporation of SO2 into ice depositing from the vapor at −15°C. Surprisingly, SO2 was captured in deposited ice at concentrations comparable to those given by SO2/S(IV) aqueous equilibrium at 0°C. A consequence of this result is that, in the remote troposphere, unrimed snow scavenging ratios for SO2 may be comparable to those for sulfate. In addition, ozone and HCHO appeared to inhibit, rather than enhance, SO2 uptake. An aqueous‐film model is developed to account for SO2 capture. If SO2 dissolves in a liquidlike layer on growing ice surfaces, the concentration of S(IV) species may become enhanced within the layer as a result of retarded diffusional transport away from the advancing ice/layer interface. Such a concentration increase can produce significant solute incorporation into the bulk ice, despite effective solute rejection from the ice.