Abstract
Nature of individual hygroscopic particles, including those in the Aitken size range, was examined by the dialysis of water-soluble material applied to samples collected on a carbon covered nitrocellulose film supported on an electron-microscopic grid. The samples were collected by a low-pressure impactor in the urban atmosphere of Nagoya and Yokkaichi. Change in morphology of particles on the collecting surface before and after the dialysis was observed by an electron microscope. More than 80% of aerosol particles of 0.03 to 0.35μm radius were hygroscopic particles. Mixed particles occupied 34% of hygroscopic particles in the Aitken size range (0.03-0.10μm radius) and 67% in the large size range (0.10-0.35μm radius). The volume fraction of water-soluble material ε in individual particles was estimated by the electron microscopic examination. Those with high values of ε(>0.95) were dominant hygroscopic particles of 0.03 to 0.35μm radius.
