Aerosol Science 37 (2006) 1797 – 1808 www.elsevier.com/locate/jaerosci Changes in large particle size distribution due to dry deposition processes Kenneth E. Noll ∗ , Obatosin Aluko Department of Chemical and Environmental Engineering, Illinois Institute of Technology, 10W. 33rd St. Chicago, IL 60616, USA Received 29 April 2006; received in revised form 7 August 2006; accepted 29 August 2006 Abstract A dry deposition model is described that can simulate variations in the size-resolved mass size distribution of large (> 1 m diameter) atmospheric particles due to dry deposition processes. The model is unique because it is based on both gravitational and inertial effects in turbulent flow and includes deposition and suspension velocities for large, airborne particles. The model allows the integration of a large number of variables, covering a wide range of conditions (height of particle injection, meteorological conditions, and removal time). Changes in the size distributions that result from model simulations of deposition show the expected decrease in concentration with size since the deposition is greater for the larger particles. However, the size distribution does not decrease with size in a uniform manner as would be suggested by Stokes settling velocity due to the effect of inertial forces acting on the particles. Application of the model reveals a number of patterns, including the development of two peaks in the large particle mass size distribution, a persistent peak in the 1–10 m size range, and a second peak in the 10–40 m range that is strongly affected by meteorological conditions. Published by Elsevier Ltd. Keywords: Dry deposition velocities; Suspension velocities; Inertial impaction; Deposition modeling; Size distribution 1. Introduction The process of particle emission, deposition, and suspension affect the initial concentration of particles and variations in the size distribution with time. However, measurements of size resolved particle concentration/time variations are complicated by the poor size and concentration resolution of particle sampling instruments and resulting particle data, and the episodic nature of both the pollutant emissions and deposition. A number of models are available that couple entrainment and deposition processes (Tegen, 2003) to aid in understanding the dynamics of particle production and removal in the atmosphere. Many of these models have shown promising results in regional and global simulations. For example models for dust emission, transport, and deposition exist for the Sahara (Westphal, Toon, & Carlson, 1988) and Asia (Wang, Ueda, & Huang, 2000). Predicting the distribution of particles with these models generally require representation of source, sink and transport processes and include particle mobilization by wind from natural sources or emission from anthropogenic sources; sink processes that include gravitation sedimentation, turbulent mixing, and wet deposition; and meteorological transport and chemical transformation processes that include comparing model ∗ Corresponding author. Tel.: +1 312 567 3536. E-mail address: noll@iit.edu (K.E. Noll). 0021-8502/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.jaerosci.2006.08.006