Scavenging of SO 2 and NH 3 during growth of ice

Abstract

Scavenging of SO 2 and NH 3 during ice growth by deposition of water vapour by diffusion was studied in a diffusion chamber at T=−6°C and −15°C. At both temperatures, we observed within the ice an increase of sulphur compounds, expressed as S(VI), for SO 2 gas concentrations up to about 3 ppmv. At higher concentrations, saturation was reached in the ice phase. Addition of O 3 to the flowing air produced an increase of S(VI) within the ice, at lower SO 2 concentrations only. In experiments with NH 3, we obtained at T=−15°C nitrogen compound concentrations, expressed as NH 4 +, regardless of the NH 3 concentration in the gas phase in the range of concentrations tested, while at T=−6°C, NH 4 + increased with increasing NH 3. Concentrations of NH 4 + and SO 4 2− turned out to be higher at T=−6°C, compared to −15°C. By considering mixed runs at T=−15°C and −6°C, we observed an increase in both NH 4 + and SO 4 2− in the ice phase, compared to experiments at the same temperature, but with separate gases.