Heterogeneous interaction of SO2 on H2O2-ice films at 190-210 K

Heterogeneous interaction of SO2 on both the H2O2-ice surface and the water-ice surface has been investigated in a flow reactor interfaced with a differentially pumped quadrupole mass spectrometer. The initial uptake coefficient and uptake amount of SO2 on the H2O2-ice surface and the water-ice surface were determined as a function of partial SO2 pressures and ice film temperatures. The initial "true" uptake coefficient gamma(o) of SO2 on 3% H2O2-ice surfaces is 3.2 x 10(-4) and 8.3 x 10(-5) at 192 and 211 K, respectively. The initial uptake coefficient gamma(w) of SO2 on the water-ice film is 1 x 10(-5) at 191 K. The uptake amount of SO2 on the H2O2-ice surface at 192 K was determined in the range of 9.5 x 10(12) to 5.3 x 10(15) molecules/cm(2) ais P-SO2 increased from 1.1 x 10(-7) to 1.4 x 10(-5) Torr, and the uptake amount of SO2 on the water-ice surface at 191 K was 2.4 x 10(12) molecules/cm(2) at P-SO2 = 1.3 x 10(-6) Torr. The results suggested that the uptake of SO2 on ice and snow surfaces was enhanced by the presence of H2O2 in ice at the temperature of the upper troposphere and lower stratosphere.