Passive methods for improving air quality in the built environment: A review of porous and solid barriers

Gallagher, John; Baldauf, Richard; Fuller, Christina H.; Kumar, Prashant; Gill, Laurence; McNabola, Aonghus

doi:10.1016/j.atmosenv.2015.08.075

Cited by 188 publications

(109 citation statements)

References 55 publications

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“…The results of numerical modeling studies have indicated that trees in built environments exerted similar effects as a solid barrier, and particle dispersion was affected by trees species, crown morphology, porosity, LADs, trees height, and tree-building distance [22]. Simulations have shown that wide streets and low building heights favored air ventilation and the removal of air pollutants within an isolated street canyon [23].…”

Section: Introductionmentioning

confidence: 87%

Numerical Investigation on the Effect of Avenue Trees on PM2.5 Dispersion in Urban Street Canyons

2017

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Abstract:The Reynolds-averaged Navier-Stokes (RANS) model and revised generalized drift flux model were used to investigate the characteristics of airflow fields and PM 2.5 dispersion in street canyons with a variety setting on tree crown morphologies (i.e., conical, spherical, and cylindrical), leaf area densities (LADs = 0.5, 1.5, and 2.5 m 2 /m 3 ), and street canyon aspect ratios (H/W = 0.5, 1.0, and 2.0). Results were as follows: (1) airflow fields were reversed in the presence of trees and enhanced with higher LAD; (2) air velocity decreased negligibly when LAD increased from 1.5 to 2.5, but significantly when LAD increased from 0.5 to 1.5; (3) tree crown morphologies, building aspect ratios, and LADs were interrelated. The comparison of PM 2.5 showed that the most critical situations in H/W = 0.5, 1.0, and 2.0 corresponded to LAD = 0.5 with a conical canopy; (4) the H/W = 1.0 and LAD = 1.5 scenario was identified as the most efficient combination for PM 2.5 capture; (5) the maximum PM 2.5 reduction ratio was ordered from low to high in the sequence of conical, spherical, and cylindrical canopies. At predestinated LADs and aspect ratio, Populus tomentosa with cylindrical crown morphology exhibited the best efficiency on PM 2.5 capture with a reduction ratio of 75% to 85% at pedestrian height.

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Section: Introductionmentioning

confidence: 87%

Numerical Investigation on the Effect of Avenue Trees on PM2.5 Dispersion in Urban Street Canyons

2017

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“…Previous studies suggested that greenspace reduced PM 2.5 concentration as a sink landscape [53], and outdoor PM 2.5 concentrations can be reduced by dry and wet deposition on leaves; it was revealed that vegetation had the strong impact on PM 2.5 mitigation [40], and a combination of trees and other solid barriers, such as building and parked cars, could reduce local air pollution [26], so higher PLAND of greenspace reduced more PM pollution. Higher LPI and ED may increase the interactions between greenspace and other elements in urban areas to mitigate PM pollution more efficiently, because LPI increased the energy gradient between greenspace and other elements and their interaction, and as an indicator of the complexity of the green space edges, ED reflects the degree of interactions between greenspace and other elements [40].…”

Section: Scale-dependent Effects Of Greenspace Pattern On Pm Pollutionmentioning

confidence: 99%

Effects of Urban Greenspace Patterns on Particulate Matter Pollution in Metropolitan Zhengzhou in Henan, China

Lei

Duan

et al. 2018

Atmosphere

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This case study was conducted to quantify the effects of urban greenspace patterns on particle matter (PM) concentration in Zhengzhou, China by using redundancy and variation partitioning analysis. Nine air-quality monitoring stations (AQMS) were selected as the central points. Six distances of 1 km, 2 km, 3 km, 4 km, 5 km, and 6 km were selected as the side lengths of the squares with each AQMS serving as the central point, respectively. We found:(1) the fine size of PM (PM 2.5 ) and coarse size of PM (PM 10 ) among four seasons showed significant differences; during winter, the concentration of PM 2.5 and PM 10 were both highest, and PM 2.5 and PM 10 concentration in summer were lowest. (2) To effectively reduce the PM 2.5 pollution, the percentage of greenspace, the differences in areas among greenspace patches, and the edge complexity of greenspace patches should be increased at distances of 2 km and 3 km. To effectively reduce PM 10 , the percentage of greenspace at a distance of 4 km, the edge density at distances of 2 km and 4 km, and the average area of greenspace patches at a distance of 1 km should be increased. (3) Greenspace pattern significantly affected PM 2.5 at a distance of 3 km, and PM 10 at a distance of 4 km. From shorter distance to longer distance, the proportion of variance explained by greenspace showed a decline-increase-decline-increase trend for PM 2.5 , and a decline-increase-decline trend for PM 10 . At shorter distances, the composition of greenspace was more effective in reducing the PM pollution, and the configuration of greenspace played a more important role at longer distances. The results should lead to specific guidelines for more cost-effective and environmentally sound greenspace planning.

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“…Due to the lack of specific tree data, the mean height of trees was estimated through satellite images from Google Earth ® and ranges from 5 m to 12 m. Even though challenges and strategies for urban green-space planning in compact cities have also been proposed [32], it can be argued that the effects of urban vegetation strictly depend on their interaction with the city morphology and meteorological conditions. Currently, studies which account for the main effects of trees (aerodynamic, deposition and thermal) are still poor in the literature and thus, comprehensive strategies on the use of urban vegetation for air quality purposes are still missing [1].…”

Section: The Study Area and Modeling Set-upmentioning

confidence: 99%

“…Traffic emissions generally constitute the major source of air pollution and roadside barriers can be employed to influence flow patterns and, thus, the resulting levels of concentrations. Advantages and disadvantages of using several barriers, such as trees and vegetation, noise barriers, low boundary walls, and parked cars, have been recently reviewed by Gallagher et al [1].…”

Section: Introductionmentioning

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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Passive methods for improving air quality in the built environment: A review of porous and solid barriers

Cited by 188 publications

References 55 publications

Numerical Investigation on the Effect of Avenue Trees on PM2.5 Dispersion in Urban Street Canyons

Numerical Investigation on the Effect of Avenue Trees on PM2.5 Dispersion in Urban Street Canyons

Effects of Urban Greenspace Patterns on Particulate Matter Pollution in Metropolitan Zhengzhou in Henan, China

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

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