Fractal dimensional classification of aerosol particles by computer-controlled scanning electron microscopy.

A method for the classification of individual aerosol particles into one of two main groups, namely, fly ash and soil dust, is presented. It is based on the calculation of the fractal dimensions of the images of the particles obtained with the computer-controlled scanning electron microscopy. The risk of an improper determination of the fractal dimension is pointed out. It is shown that spherically shaped particles that normally compose the majority of the fly ash particles do not possess fractality. The rarely met fly ash particles with very irregular shape possess two types of the fractal dimensions, namely, textural and structural. On the other hand, it is found that the soil dust particles have only a textural fractal dimension. The obtained results allow the unequivocal identification of the particle source, which is especially important when the chemical compositions of the particles are nearly the same.