LABORATORY STUDY OF NO2 REACTION WITH DISPERSED AND BULK LIQUID WATER

We have studied the reaction 2NO2(g) + H2O(l) --> 2H+ + NO3- + NO2- with dispersed and bulk liquid water. The experiments were performed with a laboratory cloud chamber at conditions corresponding to the phase-mixed reaction regime, when the apparent reaction order with respect to NO2 should reflect the aqueous-phase reaction order. Parallel measurements with water bubblers were performed under conditions favoring the mass transport controlled regime. Our results show that the reaction is first order with respect to gaseous NO2 for both reaction regimes. These results differ from results obtained by other workers from experiments with a bulk water system (Lee and Schwartz, 1981 a,b, J. phys. Chem. 85, 840-848, J. geophys. Res. 86, 11,971-11,983), which showed reaction orders of 2 and 1, respectively, for the two regimes. Our results also demonstrate that NO2 reaction with acidified cloud droplets should be a source of gaseous HONO. Finally, we present preliminary evidence of a possible synergism between HNO3 and the uptake and oxidation of NO2 in cloud droplets.