SCAVENGING OF SO2 AND NH3 DURING GROWTH OF ICE

Scavenging of SO2 and NH3 during ice growth by deposition of water vap our by diffusion was studied in a diffusion chamber at T = -6 degrees C and -15 degrees C. At both temperatures, we observed within the ice an increase of sulphur compounds, expressed as S(VI), for SO2 gas conc entrations up to about 3 ppmv. At higher concentrations, saturation wa s reached in the ice phase. Addition of O-3 to the flowing air produce d an increase of S(VI) within the ice, at lower SO2 concentrations onl y. in experiments with NH3, we obtained at T = -15 degrees C nitrogen compound concentrations, expressed as NH:, regardless of the NH, conce ntration in the gas phase in the range of concentrations tested, while at T = -6 degrees C, NH4+ increased with increasing NH3. Concentratio ns of NH4+ and SO42- turned out to be higher at T = -6 degrees C, comp ared to -15 degrees C. By considering mixed runs at T = -15 degrees C and -6 degrees C, we observed an increase in both NH4+ and SO42- in th e ice phase, compared to experiments at the same temperature, but with separate gases. (C) 1998 Elsevier Science B.V. All rights reserved.