Field evaluation of vegetation and noise barriers for mitigation of near-freeway air pollution under variable wind conditions

Lee, Eon S.; Ranasinghe, Dilhara; Ahangar, Faraz Enayati; Amini, Seyedmorteza; Mara, Steven; Choi, Won-Sik; Paulson, Suzanne E.; Zhu, Yifang

doi:10.1016/j.atmosenv.2017.11.060

Cited by 43 publications

(26 citation statements)

References 30 publications

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“…Also, the concentration can be larger than that without the barrier if α is large enough. If we assume that vegetation can reduce turbulence levels, vegetation on top of a solid barrier can enhance the effect of the solid barrier by reducing entrainment of the pollutant into the wake of the solid barrier, as has been shown by Baldauf et al (2008) and Lee et al (2018). Figure 4 also highlights the potential for downwind pollutant reductions with thick, less porous vegetation, as pollutant concentrations behind the bushes and bush/tree combinations (Stops 2, 4, and 6) were lower for the normal wind conditions as compared to all wind conditions.…”

Section: Resultsmentioning

confidence: 94%

The effects of roadside vegetation characteristics on local, near-road air quality

Deshmukh

Isakov

Venkatram

et al. 2018

Air Qual Atmos Health

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Roadside vegetation has been shown to impact downwind, near-road air quality, with some studies identifying reductions in air pollution concentrations and others indicating increases in pollutant levels when vegetation is present. These widely contradictory results have resulted in confusion regarding the capability of vegetative barriers to mitigate near-road air pollution, which numerous studies have associated with significant adverse human health effects. Roadside vegetation studies have investigated the impact of many different types and conditions of vegetation barriers and urban forests, including preserved, existing vegetation stands usually consisting of mixtures of trees and shrubs or plantings of individual trees. A study was conducted along a highway with differing vegetation characteristics to identify if and how the changing characteristics affected downwind air quality. The results indicated that roadside vegetation needed to be of sufficient height, thickness, and coverage to achieve downwind air pollutant reductions. A vegetation stand which was highly porous and contained large gaps within the stand structure had increased downwind pollutant concentrations. These field study results were consistent with other studies that the roadside vegetation could lead to reductions in average, downwind pollutant concentrations by as much as 50% when this vegetation was thick with no gaps or openings. However, the presence of highly porous vegetation with gaps resulted in similar or sometimes higher concentrations than measured in a clearing with no vegetation. The combination of air quality and meteorological measurements indicated that the vegetation affects downwind pollutant concentrations through attenuation of meteorological and vehicle-induced turbulence as air passes through the vegetation, enhanced mixing as portions of the traffic pollution plume are blocked and forced over the vegetation, and through particulate deposition onto leaf and branch surfaces. Computational fluid dynamic modeling highlighted that density of the vegetation barrier affects pollutant levels, with a leaf area density of 3.0 m 2 m −3 or higher needed to ensure downwind pollutant reductions for airborne particulate matter. These results show that roadside bushes and trees can be preserved or planted along highways and other localized pollution sources to mitigate air quality and human health impacts near the source if the planting adheres to important characteristics of height, thickness, and Highlights

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Section: Resultsmentioning

confidence: 94%

The effects of roadside vegetation characteristics on local, near-road air quality

Deshmukh

Isakov

Venkatram

et al. 2018

Air Qual Atmos Health

View full text Add to dashboard Cite

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“…A higher vegetation barrier density generally results in lower downwind concentrations of both PM 86,98,99 and gaseous pollutants 54,100 . However, CFD modelling undertaken by Ghasemian et al 54 found that a LAD of 3.33 m 2 /m 3 reduced downwind concentrations of roadway emissions (represented by a tracer gas) by 10%, whereas a LAD of 1 m 2 /m 3 increased downwind concentrations by 15%.…”

Section: Density and Porositymentioning

confidence: 99%

Designing vegetation barriers for urban air pollution abatement: a practical review for appropriate plant species selection

2020

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Vegetation can form a barrier between traffic emissions and adjacent areas, but the optimal configuration and plant composition of such green infrastructure (GI) are currently unclear. We examined the literature on aspects of GI that influence ambient air quality, with a particular focus on vegetation barriers in open-road environments. Findings were critically evaluated in order to identify principles for effective barrier design, and recommendations regarding plant selection were established with reference to relevant spatial scales. As an initial investigation into viable species for UK urban GI, we compiled data on 12 influential traits for 61 tree species, and created a supplementary plant selection framework. We found that if the scale of the intervention, the context and conditions of the site and the target air pollutant type are appreciated, the selection of plants that exhibit certain biophysical traits can enhance air pollution mitigation. For super-micrometre particles, advantageous leaf micromorphological traits include the presence of trichomes and ridges or grooves. Stomatal characteristics are more significant for sub-micrometre particle and gaseous pollutant uptake, although we found a comparative dearth of studies into such pollutants. Generally advantageous macromorphological traits include small leaf size and high leaf complexity, but optimal vegetation height, form and density depend on planting configuration with respect to the immediate physical environment. Biogenic volatile organic compound and pollen emissions can be minimised by appropriate species selection, although their significance varies with scale and context. While this review assembled evidence-based recommendations for practitioners, several important areas for future research were identified.

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“…On-site air quality measurements, also if coupled with field vegetation inventories, and data analysis [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] On-site air quality measurements or soil sampling, measurements of pollution removal by means of laboratory techniques, including instrumental analysis on plant samples (e.g., microscopic analysis, spectroscopy, gravimetry, gas exchange measurements, wind tunnel experiments on leaves or branches etc.) and data analysis [31][32][33][34][35] Measurements of pollution removal by means of laboratory techniques, including instrumental analysis on plant samples and data analysis [11][12][13] Estimates of pollution removal by vegetation or statistical analysis based on field plant inventories or remote sensing data and existing literature/databases or air quality data [60][61][62][63][64][65][66] Modelling Approaches…”

Section: Field Measurements And/or Laboratory Analysismentioning

confidence: 99%

Urban Vegetation in Air Quality Management: A Review and Policy Framework

2020

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Recent episodes of high air pollution concentration levels in many Polish cities indicate the urgent need for policy change and for the integration of various aspects of urban development into a common platform for local air quality management. In this article, the focus was placed on the prospects of improving urban air quality through proper design and protection of vegetation systems within local spatial planning strategies. Recent studies regarding the mitigation of air pollution by urban greenery due to deposition and aerodynamic effects were reviewed, with special attention given to the design guidelines resulting from these studies and their applicability in the process of urban planning. The conclusions drawn from the review were used to conduct three case studies: in Gdańsk, Warsaw, and Poznań, Poland. The existing local urban planning regulations for the management of urban greenery were critically evaluated in relation to the findings of the review. The results indicate that the current knowledge regarding the improvement of urban air quality by vegetation is not applied in the process of urban planning to a sufficient degree. Some recommendations for alternative provisions were discussed.

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Field evaluation of vegetation and noise barriers for mitigation of near-freeway air pollution under variable wind conditions

Cited by 43 publications

References 30 publications

The effects of roadside vegetation characteristics on local, near-road air quality

The effects of roadside vegetation characteristics on local, near-road air quality

Designing vegetation barriers for urban air pollution abatement: a practical review for appropriate plant species selection

Urban Vegetation in Air Quality Management: A Review and Policy Framework

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