SO2/H2O/N2混合ガス中でのα線照射によるナノメータエアロゾル生成に関する実験的研究

概要

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Formation of nanometer-sized particles by α-ray radiolysis in SO2/H2O/N2 mixtures was experimentally investigated. The size and charge distributions of generated particles were measured simultaneously using a differential mobility particle sizer (composed of a Vienna-type differential mobility analyzer, a particle-size magnifier (PSM), and an optical particle counter) and a ultrafine aerosol visualization system (composed of the PSM and an observation cell), respectively. The size and number concentration of the generated particles increased with increasing SO2 and H2O concentrations, the irradiation time, and the strength of 241Am α-source. When the SO2 concentration was 1 ppm, maximum values for average particle diameter and number concentration were 5 nm and 2.5 × 105 cm-3, respectively. The fraction of charged particles was less than 0.1. Our results showed that ion-induced nucleation was a minor mechanism and that binary nucleation of H2O molecules with H2SO4 molecules, produced by SO2-OH radical reactions, was a major mechanism.