Quantifying the impact of urban trees on passive pollutant dispersion using a coupled large-eddy simulation–Lagrangian stochastic model

Chenghao Wang, Qi Li, Zhihua Wang

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The use of shade trees is among favorable urban planning strategies to improve outdoor thermal comfort and promote energy efficiency. Meanwhile, the presence of trees alters flow patterns and turbulent transport and influences the dispersion of air pollutants. In this study, we investigated the effects of urban trees on air pollutant dispersion in urban canopy layers using a coupled large-eddy simulation–Lagrangian stochastic modeling framework. The dispersions of two-way traffic emissions were simulated using a set of twenty four scenarios with varying canyon and tree geometries. Results show that tall trees lead to the strongest modification of the canyon flow and pollutant concentration, except in narrow canyons. Trees can exacerbate canyon pollution level in certain built environment owing to the presence of isolated canyon vortices. Trees with high leaf area density are beneficial to reducing concentration in broad street canyons, while trapping of pollutants is manifest in narrow canyons. The participatory role of trees, in conjunction with the effect of urban morphology, is crucial and needs to be meticulously evaluated in urban planning for promoting environmental quality.

Original languageEnglish (US)
Pages (from-to)33-49
Number of pages17
JournalBuilding and Environment
Volume145
DOIs
StatePublished - Nov 1 2018

Fingerprint

Urban planning
Stochastic models
pollutant
eddy
canyon
Thermal comfort
Air
Dispersions
urban planning
Flow patterns
Energy efficiency
Pollution
Vortex flow
air
planning conception
Geometry
environmental quality
mathematics
traffic
scenario

Keywords

  • Atmospheric dispersion
  • Built environment
  • Environmental quality
  • Lagrangian stochastic model
  • Urban trees

ASJC Scopus subject areas

  • Environmental Engineering
  • Civil and Structural Engineering
  • Geography, Planning and Development
  • Building and Construction

Cite this

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title = "Quantifying the impact of urban trees on passive pollutant dispersion using a coupled large-eddy simulation–Lagrangian stochastic model",
abstract = "The use of shade trees is among favorable urban planning strategies to improve outdoor thermal comfort and promote energy efficiency. Meanwhile, the presence of trees alters flow patterns and turbulent transport and influences the dispersion of air pollutants. In this study, we investigated the effects of urban trees on air pollutant dispersion in urban canopy layers using a coupled large-eddy simulation–Lagrangian stochastic modeling framework. The dispersions of two-way traffic emissions were simulated using a set of twenty four scenarios with varying canyon and tree geometries. Results show that tall trees lead to the strongest modification of the canyon flow and pollutant concentration, except in narrow canyons. Trees can exacerbate canyon pollution level in certain built environment owing to the presence of isolated canyon vortices. Trees with high leaf area density are beneficial to reducing concentration in broad street canyons, while trapping of pollutants is manifest in narrow canyons. The participatory role of trees, in conjunction with the effect of urban morphology, is crucial and needs to be meticulously evaluated in urban planning for promoting environmental quality.",
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AU - Li, Qi

AU - Wang, Zhihua

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N2 - The use of shade trees is among favorable urban planning strategies to improve outdoor thermal comfort and promote energy efficiency. Meanwhile, the presence of trees alters flow patterns and turbulent transport and influences the dispersion of air pollutants. In this study, we investigated the effects of urban trees on air pollutant dispersion in urban canopy layers using a coupled large-eddy simulation–Lagrangian stochastic modeling framework. The dispersions of two-way traffic emissions were simulated using a set of twenty four scenarios with varying canyon and tree geometries. Results show that tall trees lead to the strongest modification of the canyon flow and pollutant concentration, except in narrow canyons. Trees can exacerbate canyon pollution level in certain built environment owing to the presence of isolated canyon vortices. Trees with high leaf area density are beneficial to reducing concentration in broad street canyons, while trapping of pollutants is manifest in narrow canyons. The participatory role of trees, in conjunction with the effect of urban morphology, is crucial and needs to be meticulously evaluated in urban planning for promoting environmental quality.

AB - The use of shade trees is among favorable urban planning strategies to improve outdoor thermal comfort and promote energy efficiency. Meanwhile, the presence of trees alters flow patterns and turbulent transport and influences the dispersion of air pollutants. In this study, we investigated the effects of urban trees on air pollutant dispersion in urban canopy layers using a coupled large-eddy simulation–Lagrangian stochastic modeling framework. The dispersions of two-way traffic emissions were simulated using a set of twenty four scenarios with varying canyon and tree geometries. Results show that tall trees lead to the strongest modification of the canyon flow and pollutant concentration, except in narrow canyons. Trees can exacerbate canyon pollution level in certain built environment owing to the presence of isolated canyon vortices. Trees with high leaf area density are beneficial to reducing concentration in broad street canyons, while trapping of pollutants is manifest in narrow canyons. The participatory role of trees, in conjunction with the effect of urban morphology, is crucial and needs to be meticulously evaluated in urban planning for promoting environmental quality.

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KW - Built environment

KW - Environmental quality

KW - Lagrangian stochastic model

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