THE KINETICS OF THE PHOTOLYTIC PRODUCTION OF AEROSOLS FROM SO2 AND NH3 IN HUMID AIR

The reaction of SO2 and NH3 in humid air to produce an aerosol of ammo nium sulfate is studied in a photolytic laboratory reactor. The reacti on is shown to be controlled by ultraviolet irradiation in the wavelen gth range of 240-330 nm and is initiated by excitation of SO2. It is f ound that NH3 has a strong catalytic effect on the photolytic oxidatio n of SO2 and surprisingly high values of the quantum yield are observe d with NH3 concentration in the range of 20-400 ppm. The reaction rate increases with decreasing temperature. An overall mechanism for the f ormation of aerosol particles is proposed. It is concluded that aeroso l formation due to sunlight photolysis by this mechanism explains the high-opacity smoke formed in industrial stack plumes with small amount s of NH3 and SO2.