Article: Steffens JT, Wang YJ and Zhang KM (2012). “Exploration of effects of a vegetation barrier on particle size distributions in a near-road environment.” Atmospheric Environment 50: 120-128.
Abstract: w Roadside vegetation barriers have been suggested as a potential mitigation strategy for near-road air pollution. However, there is still a lack of mechanistic understanding of how roadside barriers affect pollutant transport and transformation on and near roadways, especially under different meteorological conditions and barrier properties. In this study, we incorporated the representations of particle aerodynamics and deposition mechanisms into the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model, and explored the effects of vegetation barriers on near-road particulate air pollution by comparing the simulation results against field measurements. The model shows generally adequate agreement with concentrations of particles larger than 50 nm, but tends to overpredict concentrations of particles less than 50 nm behind a vegetation barrier. Sensitivity tests were performed by comparing two different particle dry deposition models and varying the vegetation density and local meteorology. It was found that an increase in leaf area density (LAD) further reduces particle concentration, but the responses were non-linear. Increases in wind speed were shown to enhance particle impaction, but reduce particle diffusion, which result in reduction in concentration for particles larger than 50 nm but have a minimal effect on particles smaller than 50 nm. Further improvements in representing particle deposition and aerodynamics in near-road environments are needed to fully capture the complex effects of roadside vegetation barriers.
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