ELUCIDATION OF GENERATION AND GROWTH MECHANISMS OF SECONDARY PARTICLES

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For assessment and prevention of the impact of secondary aerosol particles on atmospheric environment and human health, particle generation mechanism and methods for an accurate measurement of cluster ion and nanoparticles were investigated in this report.1. MEASUREMENT OF AEROSOL SIZE DISTRIBUTIONIn order to measure the particle size distribution of atmospheric aerosols from about 1nm to some microns, the differential mobility analyzer (DMA), mixing-type condensation nucleus counter (M-CNC), Faraday cup electrometer (FCE) were improved. Especially, combination of newly developed particle size magnifier (PSM) and conventional CNC made possible to measure number concentration of nanoparticles and ions down to 3nm in atmospheric and low pressure conditions. Moreover, in order to charge aerosol particles, alternative soft X-ray photoionizer was newly developed.2. DEVELOPMENT OF THE CARBON-CONTAINING AEROSOL MEASURING METHODFor an improvement of measuring technique for OC (organic carbon) … More and EC (elemental carbon) of aerosols, fundamental study for optical technique and comparison of OC concentrations with sampling methods were performed. For the improvement of carbonaceous particle measurement, standard filters with EC and OC reference particles were fabricated by a spray-drying method. The composite particles of SiO2/Carbon black were also prepared and the optical properties were also evaluated.3. NUCLEATION AND GROWTH OF NANO-PARTICLES BY ION-INDUCED NUCLEATIONExperimental system, which consists of a drift tube ion mobility spectrometer/mass spectrometer and a cluster-DMA combined with FCE, was developed to investigate the relationship between cluster ions and nanoparticles. This system enabled mass spectrometric measurement of ions and high-resolution mobility spectrometric measurements of ions and ultrafine particles generated by ionizing radiation. Since gaseous pollutants have significant effects on atmospheric aerosol particle formation, effects of NO_2, one of main atmospheric gaseous pollutants, on particle formation in SO_2/H_2O/air mixtures irradiated by α-ray was experimentally investigated and relative importance of ion-induced nucleation to homogeneous nucleation was discussed. Less