Gas-to-Particle Conversion of Polluted Gas by Nucleation

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A dispersed system of submicron, fine particles in the atmospheric air (aerosol) causes atmospheric pollution, problems on human health and the greenhouse effect to the earth. However, the processes of gas-to-particle conversion which are important as the processes of fine particle generation in the atmospheric environment have not been fully evaluated to date since these are governed by nucleation phenomena. Therefore, in this study, the conversion processes of trace impurity gas in the atmosphere into fine particles, and dynamic behavior and deposition processes of fine particles and gas, which are important especially from the viewpoint of investigating atmospheric pollution, were studied through collaboration among researchers in Japan, U.S.A.and Europe.In the experiments of this study, nucleation phenomena in binary and ternary gas systems including NO_<x'>, SO_<x'>, H_2O,etc.were investigated using a small chamber equipped with a radioactive source and an adiabatic expansion cham … More ber. The rate of nucleation and the effect of ions on the enhancement of nucleation were then clarified from the measurements of the size distributions of clusters and particles. The mechanisms of the enhancement of nucleation by ions were discussed with a theoretical model based on the modem nucleation theories, which made it possible to explain the experimental results. The general dynamic equation and convection-diffusion equation were also derived to describe the growth processes of generated particles, and the transport and deposition processes of gas and particles. The results of numerical calculation of the equations could explain the results of experiments on particle generation via chemical reaction and experiments using a small space where gas and particles are suspended. Accordingly, the results obtained through the experiments and theoretical investigation of this study are considered useful for constructing a physico-mathematical model for evaluating the effect of fine particles in the environment. Less