Measurement in a wind tunnel of dry deposition velocities of submicron aerosol with associated turbulence onto rough and smooth urban surfaces

Roupsard, Pierre; Amielh, Muriel; Maro, D.; Coppalle, A.; Branger, Hubert; Connan, O.; Laguionie, P.; Hébert, D.; Talbaut, M.

doi:10.1016/j.jaerosci.2012.07.006

Cited by 72 publications

(32 citation statements)

References 24 publications

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“…Dry deposition velocities have been analysed selecting downward fluxes for the different datasets to separate emission (upward fluxes often associated with local sources) from deposition processes [47,48]. In general, under turbulence conditions, especially during daytime, dry deposition is controlled by the settling velocity, aerodynamic resistance, turbulent diffusion of the particles (Brownian motion), and their impaction and interception [26].…”

Section: Resultsmentioning

confidence: 99%

Correlation of Dry Deposition Velocity and Friction Velocity over Different Surfaces for PM2.5 and Particle Number Concentrations

Donateo

Contini

2014

Advances in Meteorology

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Dry deposition of particles is an important way of aerosol removal from the atmosphere and a key process in surface-atmosphere exchanges. The deposition velocities, Vd, are often parameterised in air quality and climate modelling as function of the friction velocity,u*, atmospheric stability, and particle size (if size-segregated information is available). In this work, a study of the correlation between Vd andu*over different surfaces is presented for both PM2.5 and particle number fluxes. Results indicate an almost linear increase of Vd withu*with slopes similar for PM2.5 fluxes and particle number fluxes over the different surfaces analysed. This means that the ratios Vd/u*tend to collapse over similar values even if Vd andu*are significantly different becauseu*take into account most of the surface effects. There is a limited difference between stable cases and unstable/neutral cases with slightly lower deposition velocities in stable cases for fixed values ofu*. The average value of Vd/u*is 0.010 ± 0.0017 (median 0.0062 ± 0.0015) (considering all stabilities) and 0.0097 ± 0.002 (median 0.005 ± 0.001) for stable cases. This could be the base for an empirical parameterisation of deposition velocities in air quality models.

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Section: Resultsmentioning

confidence: 99%

Correlation of Dry Deposition Velocity and Friction Velocity over Different Surfaces for PM2.5 and Particle Number Concentrations

Donateo

Contini

2014

Advances in Meteorology

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“…Thick leaves showed lower deposition for all particle sizes, apart from 0.2 to 2.5 mm particles. There was a 10e20 fold difference between different species in terms of particle deposition (Saebo et al, 2012).…”

Section: Description Of Vegetationmentioning

confidence: 98%

“…Most plants have a large surface area per unit volume, increasing the probability of deposition compared with the smooth, manufactured surfaces present in urban areas. For example, 10e30 times faster deposition has been reported for submicrometre (<mm) particles on synthetic grass compared with glass and cement surfaces (Roupsard et al, 2013). Particle size, among other parameters, has a great effect on deposition.…”

Section: Depositionmentioning

confidence: 99%

Review on urban vegetation and particle air pollution – Deposition and dispersion

Janhäll

2015

Atmospheric Environment

882

409

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h i g h l i g h t sCombining deposition and dispersion helps designing urban vegetation related to air quality. The dilution of emissions with clean air from aloft is crucial; limit high urban vegetation. High concentrations of air pollutants increase deposition; vegetation should be close to the source. Air floating above, and not through, vegetation barriers is not filtered; decides barrier porosity. Differently designed vegetation catch different particle sizes. a b s t r a c tUrban vegetation affects air quality through influencing pollutant deposition and dispersion. Both processes are described by many existing models and experiments, on-site and in wind tunnels, focussing e.g. on urban street canyons and crossings or vegetation barriers adjacent to traffic sources. There is an urgent need for well-structured experimental data, including detailed empirical descriptions of parameters that are not the explicit focus of the study.This review revealed that design and choice of urban vegetation is crucial when using vegetation as an ecosystem service for air quality improvements. The reduced mixing in trafficked street canyons on adding large trees increases local air pollution levels, while low vegetation close to sources can improve air quality by increasing deposition. Filtration vegetation barriers have to be dense enough to offer large deposition surface area and porous enough to allow penetration, instead of deflection of the air stream above the barrier. The choice between tall or short and dense or sparse vegetation determines the effect on air pollution from different sources and different particle sizes.

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“…However, if one wants to follow the spatial distribution of pollutant deposition within urban areas, the roughness-length model is not suitable because it fails to differentiate among the different types of surfaces (roofs, walls, streets, etc.). For example, the experimental results of Roupsard et al (2013) suggest that dry deposition velocities can vary by a factor of 24 between two surface types in urban areas. Consequently, there is a need to be able to model dry deposition in urban areas with some spatial resolution.…”

Section: N Cherin Et Al: Dry Deposition In Urban Areas 6 Conclusionmentioning

confidence: 99%

Modelling atmospheric dry deposition in urban areas using an urban canopy approach

et al. 2015

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Revue OA, lien vers le full-text : http://www.geosci-model-dev.net/8/893/2015/gmd-8-893-2015.pdfInternational audienceAtmospheric dry deposition is typically modelled using an average roughness length, which depends on land use. This classical roughness-length approach cannot account for the spatial variability of dry deposition in complex settings such as urban areas. Urban canopy models have been developed to parametrise momentum and heat transfer. We extend this approach here to mass transfer, and a new dry deposition model based on the urban canyon concept is presented. It uses a local mixing-length parametrisation of turbulence within the canopy, and a description of the urban canopy via key parameters to provide spatially distributed dry deposition fluxes. Three different flow regimes are distinguished in the urban canyon depending on the height-to-width ratio of built areas: isolated roughness flow, wake interference flow and skimming flow. Differences between the classical roughness-length model and the model developed here are investigated. Sensitivity to key parameters are discussed. This approach provides spatially distributed dry deposition fluxes that depend on surfaces (streets, walls, roofs) and flow regimes (recirculation and ventilation) within the urban area. © 2015 Author(s). CC Attribution 3.0 License

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Measurement in a wind tunnel of dry deposition velocities of submicron aerosol with associated turbulence onto rough and smooth urban surfaces

Cited by 72 publications

References 24 publications

Correlation of Dry Deposition Velocity and Friction Velocity over Different Surfaces for PM2.5 and Particle Number Concentrations

Correlation of Dry Deposition Velocity and Friction Velocity over Different Surfaces for PM2.5 and Particle Number Concentrations

Review on urban vegetation and particle air pollution – Deposition and dispersion

Modelling atmospheric dry deposition in urban areas using an urban canopy approach

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