Near source deposition of vehicle generated fugitive dust on vegetation and buildings: Model development and theory

This paper describes the development of a simple quasi-2D Eulerian atmospheric dispersion model that accounts for dry deposition of fugitive dust onto vegetation and buildings. The focus of this work is on the effects of atmospheric surface layer parameterizations on deposition in the “impact zone” near unpaved roads where horizontal advection of a dust cloud through roughness is important. A wind model for computing average and turbulent wind fields is presented for flow within and above a roughness canopy. The canopy model has been developed to capture the most essential transport and deposition physics while minimizing the number of difficult-to-obtain input parameters. The deposition model is based on a bulk sink term in the transport equation that lumps the various dry deposition physical process. Wind field, turbulence and deposition results are presented for a range of atmospheric stabilities and roughnesses. The canopy model produces results in which deposition within a canopy is enhanced under certain initial, atmospheric and roughness conditions, while under other conditions much less deposition occurs. The primary limitation of the model is the ability to accurately determine (typically using experimental data) the vegetative deposition parameter (clearance frequency). To understand the clearance frequency better, a dimensionless parameter called the deposition effectiveness is identified that can be used to estimate deposition in the canopy. In general, the model captures the essential physics of near source dust transport and provides a tool that can efficiently simulate site-specific conditions in practical situations.