THE INTERDEPENDENCE OF AEROSOL PROCESSES AND MIXING IN POINT-SOURCE PLUMES

The basic aerosol phenomena, condensation, coagulation, nucleation and gravitational settling, were studied in plumes generated by industria l point sources. The investigation was concentrated on regions near th e source, where the plume is still clearly distinguishable from the ba ckground and not vertically mixed. Initially vapors are depleted from the plume more by condensation than by mixing, while later these two p rocesses are often comparable in magnitude. Explicit treatment of cond ensation is required during most stages of the plume development. Coag ulation is normally suppressed by the more rapid dilution, and is prob ably significant only for nanometer sized nuclei. Gravitational settli ng depletes largest particles from the plume, but has no effect on oth er aerosol processes. Binary homogeneous nucleation of sulfuric acid a nd water is probably a commonplace phenomenon in power plant plumes, c an take place only after the plume becomes rather diluted, and is favo red by high SO2(g) to fine particulate mass ratio in the emissions, co ol and humid ambient conditions, and strong solar radiation.