Near-Road Tree Canopy Modeling of Particulate Matter Impaction in Dilute Air Flows

This study examines the potential effectiveness of a vegetative buffer for reducing exposure to roadside pollutants. We used a computational fluid dynamics (CFD) modeling approach to compute particulate matter (PM) flow through a vegetative buffer near an elementary school and to investigate impaction percentages under different tree planting configurations. We examined the effects of distance, porosity, particle size, total leaf surface area, and wind speed on particulate impaction rates. We found that for the simulated elementary school site a closely spaced, 50% porous, four-row tree configuration with 924m2 of total leaf surface area significantly slowed the airflow and provided the conditions for PM impaction in a 2.5 m/s wind. Our numerical results indicated that PM impaction percentages were not appreciably affected by particle size in the range 0.1 micron to 10 micron. In our case study, we showed that up to 81% of PM1.0 impacted a vegetative surface under the examined configuration scenarios.