A LABORATORY STUDY OF THE INTERACTION OF NH3 AND NO2 WITH SEA-SALT PARTICLES

It is known from the literature that the reaction 2 NO2(aq) + Cl- (aq) --> NO3-(aq) + ClNO(g) takes place in the presence of NO2 and sea sal t aerosol. This work indicates that the reaction is first order in Cl- and second order in NO2(aq) and the rate coefficient was determined t o be 8.9 +/- 2.1) x 10(10) M-2 S-1 at 293 K. The study shows that the formation rate of nitrate in liquid sea salt aerosol is not influenced by pH in the range between 5.1 and 7.5. The uptake of ammonia in liqu id sea salt particles in the present experimental system is governed b y the rate of the reaction CO2(aq) + H2O --> H2CO3. The addition of NH 3 to NO2 and dry sea salt particles does not change the extent of nitr ate formation in the particles. The dry aerosol shows an unexpected co ntent of ammonium which increases with decreasing relative humidity. T he nitrate formation in frozen sea salt particles at 266 K exposed to only NO2, is about 5 times lower than for the corresponding droplets a t 293 K.