The Morphology and Size Distribution of Atmospheric Particles Deposited on Foliage and Inert Surfaces

Abstract

Particles deposited on leaves and inert surfaces during dry periods were examined with scanning electron microscopy to determine their morphologies and size distributions. Deposited particles were classified into two general types: spherical fly ash particles released during the burning of fossil fuels, and nonspherical particles (primarily soil material) consisting of both organic and mineral matter. Size distribution data indicated that deposited particle mass was dominated by particles larger than 10 microns in diameter, despite the fact that nearly 40 percent of the over 3800 particles analyzed were less than 2 microns in diameter. Our observations lend support to the hypothesis that a small fraction of the airborne particle population is responsible for an unproportionally large fraction of the dry-deposited particle mass and that particle sedimentation may be an important dry deposition process.