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 salt aerosol. This work indicates that the reaction is first order in Cl- and second order in NO2(aq) and the rate coefficient was determined to be 8.9 ± 2.1) × 1010 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 liquid sea salt particles in the present experimental system is governed by the rate of the reaction CO2(aq) + H2O → H2CO3. The addition of NH3 to NO2 and dry sea salt particles does not change the extent of nitrate formation in the particles. The dry aerosol shows an unexpected content of ammonium which increases with decreasing relative humidity. The nitrate formation in frozen sea salt particles at 266 K exposed to only NO2, is about 5 times lower than for the corresponding droplets at 293 K.