2成分凝集エアロゾル粒子の形態特性と個別粒子の化学組成

抄録

Morphological changes of two-component (Pb/NaCl) aerosol particles undergoing Brownian coagulation in a flowing system were studied by image processing of two-dimen-sional scanning electron micrographs of the particles. From the relationship between radii of gyration and perimeters of the particles, fractal dimensions were calculated considering the aggregates as multifractal (lower dimension d_l and higher dimension d_h). Changes in fractal dimension d_h were correlated to the degree of agglomeration.
 Chemical composition of individual particles was calculated by using diameter of primary Pb particles, side length of primary cubic NaCl particles and density of each constituents. Number distribution of the two-component particles was determined as a function of volume equivalent diameter and mass (or volume) fraction of the constituent, and time evolution of the distributions showed conversion of externally mixed aerosols to internally mixed ones due to Brownian coagulation. Mutimodality in NaCl mass distribution measured by cascade impactor could be reproduced by conversion of volume equivalent diameter to aerodynamic diameter using the primary particle sizes and density of two constituents.