REMOVAL DYNAMICS OF AIRBORNE ROAD DUST IN A VENTILATED AIRSPACE

Abstract

ABSTRACT We derive a simple linear dynamic equation to describe the removal mechanisms of airborne road dust from a ventilated airspace. The dynamic equation is sufficiently to take into account the simultaneous removal effects of turbulent coagulation, turbulent diffusive deposition, gravitational sedimentation, and airflow pattern within a ventilated airspace. Three dimensionless parameters TC, TD, and GS that characterize the relative effects of turbulent coagulation, turbulent diffusive deposition and gravitational settling, respectively, in a ventilated airspace were introduced to generalize the removal dynamics of airborne road dust. An environmental chamber test was carried out not only to determine the particle size distributions but also to verify the removal dynamics of airborne road dust in a ventilated airspace. Our results demonstrate that there is no significant variation for particle size distributions of road dust obtained from urban and suburban areas in north Taiwan region and both followed a lognormal distribution with average geometric mean diameter of 1.08 ± 0.02 µm and geometric standard deviation of 2.59 ± 0.03. Measured values match the simulated values with an r 2 value of 0.93, whereas the overall RMSE value of 2.36 ± 1.05 mg m−3 is low, indicating that the ability to predict the removal dynamics of airborne road dust within a ventilated airspace using an average particle size based linear equation. Effects of TC, TD, GS, and various ventilation systems on the time-dependent road dust concentrations are also justified.