On the Impact of Trees on Dispersion Processes of Traffic Emissions in Street Canyons

Gromke, CB Christof; Ruck, Β.

doi:10.1007/s10546-008-9301-2

Cited by 174 publications

(80 citation statements)

References 25 publications

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“…This county-wide modeling focused on broad-scale estimates of pollution removal by trees on air quality. At the local scale, pollution concentrations can be increased if trees: a) trap the pollutants beneath tree canopies near emission sources (e.g., along road ways, Gromke and Ruck, 2009;Wania et al, 2012;Salmond et al, 2013;Vos et al, 2013), b) limit dispersion by reducing wind speeds, and/or c) lower mixing heights by reducing wind speeds (Nowak et al, 2006a). Under stable atmospheric conditions (limited mixing), tree removal could lead to greater reductions in pollution concentrations at the ground level by limiting mixing with air pollutants above the canopy.…”

Section: Discussionmentioning

confidence: 99%

Tree and forest effects on air quality and human health in the United States

Nowak

Hirabayashi

Bodine

et al. 2014

Environmental Pollution

674

378

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a b s t r a c tTrees remove air pollution by the interception of particulate matter on plant surfaces and the absorption of gaseous pollutants through the leaf stomata. However, the magnitude and value of the effects of trees and forests on air quality and human health across the United States remains unknown. Computer simulations with local environmental data reveal that trees and forests in the conterminous United States removed 17.4 million tonnes (t) of air pollution in 2010 (range: 9.0e23.2 million t), with human health effects valued at 6.8 billion U.S. dollars (range: $1.5e13.0 billion). This pollution removal equated to an average air quality improvement of less than one percent. Most of the pollution removal occurred in rural areas, while most of the health impacts and values were within urban areas. Health impacts included the avoidance of more than 850 incidences of human mortality and 670,000 incidences of acute respiratory symptoms.Published by Elsevier Ltd.

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Section: Discussionmentioning

confidence: 99%

Tree and forest effects on air quality and human health in the United States

Nowak

Hirabayashi

Bodine

et al. 2014

Environmental Pollution

674

378

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“…Our validation results have been presented in Krayenhoff et al [37] and Santiago et al [28]. In addition, the current modelling of urban vegetation was evaluated by using CODASC wind-tunnel dataset (COncentration DAta of Street Canyons -www.windforschung.de/CODASC.htm) [49,50] by simulating a street canyon with and without vegetation. Two different tree porosities were used with a pressure loss coefficient (λ) of 80 and 200 m −1 (0.53 and 1.33 m −1 at full scale).…”

Section: Previous Validation Studiesmentioning

confidence: 99%

The Impact of Planting Trees on NOx Concentrations: The Case of the Plaza de la Cruz Neighborhood in Pamplona (Spain)

et al. 2017

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Abstract:In this paper, the role of trees on airborne pollutant dispersion in a real neighborhood in Pamplona (Spain) is discussed. A Computational Fluid Dynamics (CFD) model is employed and evaluated against concentrations measured during the last part of winter season at a monitoring station located in the study area. Aerodynamic and deposition effects of trees are jointly considered, which has only been done in few recent studies. Specifically, the impact on NO x concentration of: (a) tree-foliage; and (b) introducing new vegetation in a tree-free street is analyzed considering several deposition velocities and Leaf Area Densities (LAD) to model deciduous and evergreen vegetation. Results show that the higher the LAD, the higher the deposition (concentration reduction) and the blocking aerodynamic effect (concentration increase). Regardless of foliage or deposition rates, results suggest the predominance of aerodynamic effects which induce concentration increases up to a maximum of 7.2%, while deposition induces concentration decreases up to a maximum of 6.9%. The inclusion of new trees in one street modifies the distribution of pollutant, not only in that street, but also in nearby locations with concentration increase or decrease. This finding suggests that planting trees in street with traffic as an air pollution reduction strategy seems to be not appropriate in general, highlighting the necessity of ad hoc studies for each particular case to select the suitable location of new vegetation.

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“…Furthermore, the complexity of the wind flow inside the street-canyon is significantly increased by the presence of urban vegetation, which is known to modify the recirculating flow inside the street-canyons and the vortex structures, in terms of number and arrangement, which govern the vertical exchange rates of pollutants. This type of behaviour has been presented by field campaigns [13], wind tunnel experimentation [14] and numerical modelling [15 16]. Nevertheless, the extent of the resulting perturbations on air pollutants dispersion in complex urban geometries is still difficult to simulate, and the extent of the impacts on air quality are still not entirely understood.…”

Section: Introductionmentioning

confidence: 95%

Modelling of tree-induced effects on pedestrian exposure to road traffic pollution

Borrego¹,

Valente²,

Amorim³

et al. 2012

WIT Transactions on the Built Environment

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According to the United Nations Environment Programme (UNEP) information in 2009, at least 1 billion people are exposed to outdoor air pollution that exceeds the air quality standards of the World Health Organization (WHO). Poor air quality in urban areas, mainly associated with the transportation sector, has been directly linked to almost 0.8 million premature deaths annually, especially in sensitive groups such as children. In this context, the role of trees on improving urban air quality has been discussed. However, there is still a scarce understanding on the ultimate impact of trees over the exposure of pedestrians. This paper evaluates the exposure of students in their daily walk to/from school, and how it relates with the effect of trees over the local concentrations of road traffic-emitted air pollutants. The study is focused on an area of 0.380.22 km 2 centred at a high school of the city of Aveiro, in central Portugal, which is located close to a road with significant traffic. A period of one day was chosen, based on data availability. Time evolution of georeferenced location of an individual was tracked with a GPS for different alternative walking routes to the school. Air quality and meteorological data were measured in the school yard. Simulations of carbon monoxide (CO) concentrations in the study domain were performed with the Computational Fluid Dynamics (CFD) model VADIS, with and without considering the influence of trees over the dispersion. Traffic emissions were estimated with the TREM model, using traffic counts (with vehicles categories discretization) data.Simulated wind speed and CO concentrations were compared with measured values showing a very good agreement (normalized mean square error, NMSE, equals 0.29 and 0.04, respectively). An exposure model was developed that associates the georeferenced location of the student with the computed air quality WIT Transactions on The Built Environment, Vol 128, © 2012 WIT Press levels (at an average breathing height) for that specific grid cell. The model calculates the individual exposure at each time frame and the integrated value for a given period and a given route. Results have shown that, depending on wind flow behaviour, trees can promote or inhibit the ventilation of vehicle's emissions in the street-canyon. Also, knowledge-based routing can promote a lower exposure to air pollutants in typical daily travels. The variability of the estimated exposure values shows the magnitude of the error that can be committed when using a single value of air quality as a surrogate of air pollution exposure.

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On the Impact of Trees on Dispersion Processes of Traffic Emissions in Street Canyons

Cited by 174 publications

References 25 publications

Tree and forest effects on air quality and human health in the United States

Tree and forest effects on air quality and human health in the United States

The Impact of Planting Trees on NOx Concentrations: The Case of the Plaza de la Cruz Neighborhood in Pamplona (Spain)

Modelling of tree-induced effects on pedestrian exposure to road traffic pollution

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