A NEW SOURCE OF TROPOSPHERIC AEROSOLS - ION-ION RECOMBINATION

We propose a new source of aerosol particles in the lower atmosphere t hat is based on the formation, growth, and recombination of ubiquitous cosmogenically-generated ions. This mechanism provides a uniform, con tinuous fine-particle generator in the presence of precursor vapors, s uch as sulfuric acid, or certain organic compounds. Thus, for example, aqueous sulfate aerosols can form at sulfuric acid vapor partial pres sures well below the supersaturations required for homogeneous nucleat ion. De;ailed microphysical modeling shows that the highly nonlinear c hemical/physical system comprising ions, vapors, and aerosols produces ultrafine and accumulation mode particles having characteristics simi lar to those detected in the lower troposphere. Accordingly, this mech anism may explain the presence of a stable boundary layer aerosol popu lation of several hundred particles/cm(3). The theory of nucleation by ion-ion recombination (NIIR) is roughly calibrated here using observe d ultrafine particle measurements, and is applied to interpret troposp heric aerosol observations.