Scavenging of SO2 and HCl during growth of ice crystals by vapour diffusion

Scavenging of HCl and SO2 during snow-crystal growth by sublimation of water vapour from liquid droplets was studied in a cylindrical chamber housed in a cold room. The SO2 sorption in crystals appears to be independent of the gaseous-phase concentration in the tested 1.2–7.4 ppmv range. The mean sulphur (as sullphate) concentration in crystals was S(VI) = (9.3 ± 5.5) ppm. A second set of experiments was performed in the same conditions using HCl. The resulting data indicate that for Clliq− < 20 ppm all the HCl goes from the droplets into the ice, whereas for higher liquid phase Cl− concentrations, the solid phase Cl− decreases to about 0.35 times the value in the initial liquid phase.