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Ana Deletic - One of the best experts on this subject based on the ideXlab platform.
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plant traits that enhance Pollutant Removal from stormwater in biofiltration systems
International Journal of Phytoremediation, 2009Co-Authors: Jennifer Read, Tim D Fletcher, Tricia Wevill, Ana DeleticAbstract:Plants species have been shown to improve the performance of stormwater biofiltration systems, particularly in Removal of N and P. Recent research has shown that plants vary in their contribution to Pollutant Removal but little is known about the type of plant that is best suited to use in biofilters in terms of survival, growth rate, and performance. In this study, growth responses of 20 species to applications of semi-synthetic stormwater were measured, and the roles of key plant traits in Removal of N, P, and several metals were investigated. There was no evidence of negative effects of stormwater application on plant growth, and plant traits, particularly root traits, were strongly correlated negatively with N and P concentrations of effluent stormwater. The most common and strong contributors to N and P Removal appeared to be the length of the longest root, rooting depth, total root length, and root mass. The plants that made the strongest contribution to Pollutant Removal, e.g, Carex appressa, combined these traits with high growth rates. Investigation of other plant traits (e.g, physiology), causal mechanisms, and effects of more complex planting environments (e.g, species mixtures) should further guide the selection of plants to enhance performance of biofiltration systems.
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Pollutant Removal performance of field scale stormwater biofiltration systems
Water Science and Technology, 2009Co-Authors: Belinda Elizabeth Hatt, Tim D Fletcher, Ana DeleticAbstract:The Pollutant Removal performance of three separate stormwater biofiltration systems in two different climates was assessed. At one of the sites, rain events were simulated, while actual runoff events were monitored at the other two sites. In all cases, concentrations of total suspended solids (TSS), copper, lead and zinc were effectively and reliably reduced, despite variations in inflow concentrations. Two biofiltration systems also effectively reduced phosphorus concentrations, however the third system discharged elevated phosphorus concentrations relative to inflow; this is attributed to poor specification of filter media properties. Effluent nitrogen concentrations were more variable at all sites and ranged from being substantially lower to considerably higher than inflow concentrations. Flow was also measured at two sites, where it was determined that volumetric reductions in runoff further improved Pollutant Removal. TSS and heavy metals will be reliably removed by a wide range of soil-based filter media, as will phopshorus, as long as the phosphorus content of the filter media is low. However, nitrogen Removal remains a challenge because it is easily transformed to soluble forms and is influenced by wetting and drying. These results are essentially consistent with related laboratory studies.
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hydrologic and Pollutant Removal performance of stormwater biofiltration systems at the field scale
Journal of Hydrology, 2009Co-Authors: Belinda Elizabeth Hatt, Tim D Fletcher, Ana DeleticAbstract:Summary Biofiltration systems are a recommended and increasingly popular technology for stormwater management; however there is a general lack of performance data for these systems, particularly at the field scale. The objective of this study was to investigate the hydrologic and Pollutant Removal performance of three field-scale biofiltration systems in two different climates. Biofilters were shown to effectively attenuate peak runoff flow rates by at least 80%. Performance assessment of a lined biofilter demonstrated that retention of inflow volumes by the filter media, for subsequent loss via evapotranspiration, reduced runoff volumes by 33% on average. Retention of water was found to be most influenced by inflow volumes, although only small to medium storms could be assessed. Vegetation was shown to be important for maintaining hydraulic capacity, because root growth and senescence countered compaction and clogging. Suspended solids and heavy metals were effectively removed, irrespective of the design configuration, with load reductions generally in excess of 90%. In contrast, nutrient retention was variable, and ranged from consistent leaching to effective and reliable Removal, depending on the design. To ensure effective Removal of phosphorus, a filter medium with a low phosphorus content should be selected. Nitrogen is more difficult to remove because it is highly soluble and strongly influenced by the variable wetting and drying regime that is inherent in biofilter operation. The results of this research suggest that reconfiguration of biofilter design to manage the deleterious effects of drying on biological activity is necessary to ensure long term nitrogen Removal.
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hydraulic and Pollutant Removal performance of fine media stormwater filtration systems
Environmental Science & Technology, 2008Co-Authors: Belinda Elizabeth Hatt, Tim D Fletcher, Ana DeleticAbstract:Stormwater runoff from urban areas has multiple negative hydrologic and ecological impacts for receiving waters. Fine media stormwater filtration systems have the potential to mitigate these effects, through flow attenuation and Pollutant Removal. This work provides an overall assessment of the hydraulic and Pollutant Removal behavior of sand- and soil-based stormwater filters at the laboratory scale. The influence of time, cumulative inflow sediment, cumulative water volume, wetting and drying, and compaction on hydraulic capacity was investigated. The results suggested that the primary cause of hydraulic failure was formation of a clogging layer at the filter surface. Loads of sediment and heavy metals were effectively retained; however, the soil-based filters leached nitrogen and phosphorus for the duration of the experimental period. Media Pollutant profiles revealed significant accumulation of all Pollutants in the top 20% of the filter profile, suggesting that elevated discharges of nutrients was du...
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variation among plant species in Pollutant Removal from stormwater in biofiltration systems
Water Research, 2008Co-Authors: Jennifer Read, Tim D Fletcher, Tricia Wevill, Ana DeleticAbstract:Abstract Biofiltration systems use vegetation to improve efficiency of Pollutant Removal from stormwater, but little is known of how plants vary in their capacity to improve biofilter effectiveness. We used a pot trial of 20 Australian species to investigate how species vary in the Removal of Pollutants from semisynthetic stormwater passing through a soil filter medium. Effluent levels of total suspended solids (TSS), Al, Cr, Cu, Pb and Zn were similarly low for vegetated and non-vegetated soils, with reduction to 150-fold variation in NOx and NH4+. Hence, choice of plant species may have marked effects on biofilter effectiveness.
Jacques Brisson - One of the best experts on this subject based on the ideXlab platform.
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Pollutant Removal efficiency of native versus exotic common reed phragmites australis in north american treatment wetlands
Ecological Engineering, 2015Co-Authors: Mariana Rodriguez, Jacques BrissonAbstract:A B S T R A C T Growing concerns about the threat of invasive macrophyte species increasingly require the use of substitute native species in constructed wetlands for wastewater treatment. We conducted a mesocosm experiment at two loading rates to compare the Removal efficiency of treatment wetlands planted with Phragmites australis from a lineage native to North America (P. australis subsp. americanus) versus the widely used but highly invasive European P. australis. Based on the plant’s relative ecophysiological and morphological characteristics as reported in field studies, we hypothesized that the native Phragmites would show lower Pollutant Removal efficiency than the exotic European subspecies. P. australis subsp. americanus was found to show potential for treatment wetlands, and there was no evidence that its Removal efficiency would be inferior to that of European P. australis. In fact, contrary to our expectations, our results suggest that the native Phragmites may be the preferred subspecies, due to its slightly more effective Removal of phosphorus. Further pilot or full scale experiments are needed to quantitatively assess the efficiency of treatment wetlands planted with this subspecies, as well as its resistance to diseases, before its use in treatment wetlands could be definitively recommended. Also, while plant characteristics measured under field conditions may reflect a species’ potential Removal efficiency, growing conditions in treatment wetlands may differently affect morphological, ecological and physiological plant attributes and, consequently, Pollutant Removal efficiency.
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maximizing Pollutant Removal in constructed wetlands should we pay more attention to macrophyte species selection
Science of The Total Environment, 2009Co-Authors: Jacques Brisson, F ChazarencAbstract:While the positive role of macrophytes on Removal efficiency in constructed wetlands has been well established, possible differences in performance between plants species of comparable life forms and sizes are much harder to demonstrate. We reviewed 35 experimental studies published in peer-reviewed journals and proceedings on the effect of macrophyte species selection on Pollutant Removal in SSFCW. The studies cover a wide range of macrophyte species, experimental approaches (from well-replicated microcosm experiments to comparison between full full-size constructed wetlands), climatic conditions (from tropical to cold-temperate) and types of effluent (domestic, industrial, etc.). Frequent methodological limitations in these studies compel caution in the interpretation of their results. Yet, the fact that the majority found some (occasionally large) differences in efficiency between plant species for one or more type of Pollutant suggests that macrophyte species selection does matter. However, there is little generalization to be made that could help guide species selection for SSFCW, except for the exact conditions in which the experiments were done. For example, the same pair of species that was tested in different studies occasionally gave opposite results in terms of which one performs best. Also, most studies provided few insights on the mechanisms or plant properties that could explain the observed differences in plant species efficiency. Finally, we discuss other relevant research questions and approaches that could help better guide macrophyte species selection for CW.
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artificial aeration to increase Pollutant Removal efficiency of constructed wetlands in cold climate
Ecological Engineering, 2006Co-Authors: Claudiane Ouelletplamondon, Florent Chazarenc, Yves Comeau, Jacques BrissonAbstract:Abstract In horizontal subsurface flow constructed wetlands, oxygen availability, which is frequently low in summer, may be even more limiting in winter when the plants are dormant. We tested the contribution of artificial aeration on Pollutant Removal in summer and winter, with a combination of planted, unplanted, aerated and non-aerated mesocosms treating a reconstituted fish farm effluent. Artificial aeration slightly enhanced TSS Removal in all seasons regardless of treatment, probably by maintaining empty space in the head part of the gravel bed. In winter, the reduction in COD Removal in non-aerated mesocosms compared to summer was totally compensated for in aerated mesocosms, in both planted and unplanted units. Artificial aeration improved summer and winter TKN Removal for unplanted units, but the additional aeration did not fully compensate for the absence of plants, which suggests that the role of macrophytes goes beyond the sole addition of oxygen in the rhizosphere. Artificial aeration also improved TKN Removal in planted units, but to a lower extent than for unplanted units. Our results suggest that artificial aeration represents a promising approach to improve Removal efficiency in horizontal subsurface flow constructed wetland (HSSFCW), especially for fresh water fish farms in cold climate, where artificial aeration is readily available.
Tim D Fletcher - One of the best experts on this subject based on the ideXlab platform.
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plant traits that enhance Pollutant Removal from stormwater in biofiltration systems
International Journal of Phytoremediation, 2009Co-Authors: Jennifer Read, Tim D Fletcher, Tricia Wevill, Ana DeleticAbstract:Plants species have been shown to improve the performance of stormwater biofiltration systems, particularly in Removal of N and P. Recent research has shown that plants vary in their contribution to Pollutant Removal but little is known about the type of plant that is best suited to use in biofilters in terms of survival, growth rate, and performance. In this study, growth responses of 20 species to applications of semi-synthetic stormwater were measured, and the roles of key plant traits in Removal of N, P, and several metals were investigated. There was no evidence of negative effects of stormwater application on plant growth, and plant traits, particularly root traits, were strongly correlated negatively with N and P concentrations of effluent stormwater. The most common and strong contributors to N and P Removal appeared to be the length of the longest root, rooting depth, total root length, and root mass. The plants that made the strongest contribution to Pollutant Removal, e.g, Carex appressa, combined these traits with high growth rates. Investigation of other plant traits (e.g, physiology), causal mechanisms, and effects of more complex planting environments (e.g, species mixtures) should further guide the selection of plants to enhance performance of biofiltration systems.
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Pollutant Removal performance of field scale stormwater biofiltration systems
Water Science and Technology, 2009Co-Authors: Belinda Elizabeth Hatt, Tim D Fletcher, Ana DeleticAbstract:The Pollutant Removal performance of three separate stormwater biofiltration systems in two different climates was assessed. At one of the sites, rain events were simulated, while actual runoff events were monitored at the other two sites. In all cases, concentrations of total suspended solids (TSS), copper, lead and zinc were effectively and reliably reduced, despite variations in inflow concentrations. Two biofiltration systems also effectively reduced phosphorus concentrations, however the third system discharged elevated phosphorus concentrations relative to inflow; this is attributed to poor specification of filter media properties. Effluent nitrogen concentrations were more variable at all sites and ranged from being substantially lower to considerably higher than inflow concentrations. Flow was also measured at two sites, where it was determined that volumetric reductions in runoff further improved Pollutant Removal. TSS and heavy metals will be reliably removed by a wide range of soil-based filter media, as will phopshorus, as long as the phosphorus content of the filter media is low. However, nitrogen Removal remains a challenge because it is easily transformed to soluble forms and is influenced by wetting and drying. These results are essentially consistent with related laboratory studies.
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hydrologic and Pollutant Removal performance of stormwater biofiltration systems at the field scale
Journal of Hydrology, 2009Co-Authors: Belinda Elizabeth Hatt, Tim D Fletcher, Ana DeleticAbstract:Summary Biofiltration systems are a recommended and increasingly popular technology for stormwater management; however there is a general lack of performance data for these systems, particularly at the field scale. The objective of this study was to investigate the hydrologic and Pollutant Removal performance of three field-scale biofiltration systems in two different climates. Biofilters were shown to effectively attenuate peak runoff flow rates by at least 80%. Performance assessment of a lined biofilter demonstrated that retention of inflow volumes by the filter media, for subsequent loss via evapotranspiration, reduced runoff volumes by 33% on average. Retention of water was found to be most influenced by inflow volumes, although only small to medium storms could be assessed. Vegetation was shown to be important for maintaining hydraulic capacity, because root growth and senescence countered compaction and clogging. Suspended solids and heavy metals were effectively removed, irrespective of the design configuration, with load reductions generally in excess of 90%. In contrast, nutrient retention was variable, and ranged from consistent leaching to effective and reliable Removal, depending on the design. To ensure effective Removal of phosphorus, a filter medium with a low phosphorus content should be selected. Nitrogen is more difficult to remove because it is highly soluble and strongly influenced by the variable wetting and drying regime that is inherent in biofilter operation. The results of this research suggest that reconfiguration of biofilter design to manage the deleterious effects of drying on biological activity is necessary to ensure long term nitrogen Removal.
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hydraulic and Pollutant Removal performance of fine media stormwater filtration systems
Environmental Science & Technology, 2008Co-Authors: Belinda Elizabeth Hatt, Tim D Fletcher, Ana DeleticAbstract:Stormwater runoff from urban areas has multiple negative hydrologic and ecological impacts for receiving waters. Fine media stormwater filtration systems have the potential to mitigate these effects, through flow attenuation and Pollutant Removal. This work provides an overall assessment of the hydraulic and Pollutant Removal behavior of sand- and soil-based stormwater filters at the laboratory scale. The influence of time, cumulative inflow sediment, cumulative water volume, wetting and drying, and compaction on hydraulic capacity was investigated. The results suggested that the primary cause of hydraulic failure was formation of a clogging layer at the filter surface. Loads of sediment and heavy metals were effectively retained; however, the soil-based filters leached nitrogen and phosphorus for the duration of the experimental period. Media Pollutant profiles revealed significant accumulation of all Pollutants in the top 20% of the filter profile, suggesting that elevated discharges of nutrients was du...
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variation among plant species in Pollutant Removal from stormwater in biofiltration systems
Water Research, 2008Co-Authors: Jennifer Read, Tim D Fletcher, Tricia Wevill, Ana DeleticAbstract:Abstract Biofiltration systems use vegetation to improve efficiency of Pollutant Removal from stormwater, but little is known of how plants vary in their capacity to improve biofilter effectiveness. We used a pot trial of 20 Australian species to investigate how species vary in the Removal of Pollutants from semisynthetic stormwater passing through a soil filter medium. Effluent levels of total suspended solids (TSS), Al, Cr, Cu, Pb and Zn were similarly low for vegetated and non-vegetated soils, with reduction to 150-fold variation in NOx and NH4+. Hence, choice of plant species may have marked effects on biofilter effectiveness.
Jan Carmeliet - One of the best experts on this subject based on the ideXlab platform.
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the Pollutant Removal capacity of an urban street canyon and its link to the breathability and exchange velocity
Procedia Engineering, 2017Co-Authors: Aytac Kubilay, Marina Neophytou, S Matsentides, M Loizou, Jan CarmelietAbstract:Abstract The rate of Removal of Pollutants within simplified urban street canyons is investigated using air flow fields obtained from Particle Image Velocimetry (PIV) experiments and Computational Fluid Dynamics (CFD) simulations of the resulting Pollutant dispersion. In particular, the link between the Pollutant Removal capacity and the air-flow exchange velocity, a characteristic velocity widely used to characterize this Pollutant Removal capacity, is examined. First, velocity fields through a series of homogeneous urban street canyons with flat roofs are obtained using ensemble-averaged PIV measurements as obtained within water channel experiments. The experimental results for the fully-developed street canyon air velocity field are used to drive numerical simulations of turbulent Pollutant dispersion from a Pollutant release source located within the street canyon. The rate of Removal of Pollutant from the canyon is deduced from the numerical simulations and analyzed in terms of mean convective and turbulent exchange mechanisms. It is found that rate of Pollutant Removal as expressed through a Pollutant-exchange velocity is dominated by the turbulent Pollutant diffusion in the street canyon case. It is found that the air-exchange velocity cannot be used as a representative measure for Pollutant Removal, since it does not take into account all physics involved in the Removal process. It is only a measure for the convective Pollutant flux when the Pollutants are uniformly distributed in the control volume.
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The Pollutant Removal capacity of urban street canyons as quantified by the Pollutant exchange velocity
Urban Climate, 2017Co-Authors: Aytac Kubilay, Marina Neophytou, S Matsentides, M Loizou, Jan CarmelietAbstract:Abstract In this work we investigate the representativeness of the Pollutant exchange velocity as a quantitative metric for the actual Pollutant Removal capacity of a canyon under different pollution emission scenarios. We further explore its sensitivity to a change of the street canyon geometry aspect ratio as well as different exposure regions of interest within a 2-D canyon. We find that the effective Pollutant Removal capacity as quantified by the Pollutant exchange velocity can vary substantially from its reference-nominal value as customarily derived for uniformly-distributed Pollutant conditions in the canyon. We specifically find that for the case of the center and leeward wall locations of the source, the Pollutant exchange velocity varied substantially exceeding a factor of 2 variations. Furthermore, we find that the highly nonhomogeneous Pollutant distribution arising from the different source locations plays an important role in the Pollutant Removal rate accounting for both the turbulent and convective Pollutant transport. As expected, the Pollutant-exchange velocity was found to be dominated by the turbulent flux, reaching up to 2 to 3 times the convective Pollutant flux at the rooftop level.
Dennis Y C Leung - One of the best experts on this subject based on the ideXlab platform.
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on the mechanism of air Pollutant re entrainment in two dimensional idealized street canyons
Atmospheric Environment, 2011Co-Authors: W C Cheng, Thomas C Y Leung, Dennis Y C LeungAbstract:Abstract The two-dimensional (2D) idealized street canyon, which is the generic unit of a city, is the platform for our fundamental understanding of ventilation and Pollutant Removal at the neighborhood scale. The building-height-to-street-width aspect ratio h/b is the key geometric parameters affecting the flow structures in a street canyon. In this study, a series of computational fluid dynamics (CFD) sensitivity tests were performed to examine how the air Pollutant concentration in a street canyon is related to the aspect ratio. The Reynolds-averaged Navier–Stokes (RANS) equations and the Renormalization Group (RNG) k − e turbulence model were used in the mathematical model. The spatial behaviors of air Pollutant transport from the facades, streets, and roofs to the shear layer were depicted by the local Pollutant exchange rate ω. Besides, the bulk quantities, air exchange rate ACH, Pollutant exchange rate PCH, and volume average Pollutant concentration Θ, were used to elucidate the ventilation and Pollutant Removal mechanisms of the street canyon. The aspect ratios tested were in the range 0.067 ≤ h/b ≤ 2.5 that covered the isolated roughness, wake interference and skimming flow regimes in 2D street canyons. A local maximum Θ was determined in 0.2 ≤ h/b ≤ 0.5 that is different from the monotonic ACH or PCH. The CFD results showed that the mildly elevated air Pollutant concentration is not caused by poor Pollutant Removal but the Pollutant re-entrainment from the shear layer aloft back into the street canyon. It is thus suggested that ACH, PCH, and Θ should be used as complementary indicators.
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on the correlation of air and Pollutant exchange for street canyons in combined wind buoyancy driven flow
Atmospheric Environment, 2009Co-Authors: W C Cheng, Chunho Liu, Dennis Y C LeungAbstract:The ventilation and Pollutant transport in a two-dimensional (2D) street canyon of building-height-to-street-width (aspect) ratio h/b = 1 under different unstable stratifications were examined. To characterize the combined wind-buoyancy-driven flow and Pollutant transport at different Richardson number Ri, a computational fluid dynamics (CFD) model based on the Reynolds-averaged Navier–Stokes (RANS) equations with the Renormalization Group (RNG) k − e turbulence model was adopted. Unlike the isothermal condition, a secondary recirculation is initiated at the ground-level windward corner of the street canyon once the unstable stratification is switched on (Ri < 0). It traps the ground-level Pollutant leading to elevated Pollutant concentration there. As Ri further decreases, the enlarging secondary recirculation enables direct Pollutant Removal from its core to the shear layer that offsets the ground-level Pollutant accumulation. The ventilation and Pollutant Removal performance under different unstable stratifications are compared by the air (ACH) and Pollutant (PCH) exchange rates, and Pollutant retention time (τ). Both the mean and turbulent components of ACH are found to increase with decreasing Ri, suggesting that unstable stratification promotes ventilation in street canyons. Moreover, the CFD results agree well with our theoretical model that ACH2 varies linearly with Ri. Turbulent transport originally dominates the Pollutant Removal under isothermal condition. However, progressive domination of Pollutant Removal by mean wind can be observed with decreasing stability (decreasing Ri from 0 to −10.6). The critical value is estimated to be Ri = −8, below which mean wind is the major Pollutant Removal carrier. Reduction in τ is also observed with decreasing Ri. Hence, in unstable stratification, Pollutant resides shorter time in the street canyon compared with its isothermal counterpart, and the ventilation and Pollutant Removal are more favorable.
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computational formulation for the evaluation of street canyon ventilation and Pollutant Removal performance
Atmospheric Environment, 2008Co-Authors: W C Cheng, Chunho Liu, Dennis Y C LeungAbstract:Abstract A computational formulation using the concept of air exchange rate (ACH), Pollutant exchange rate (PCH), average Pollutant concentration (Θ) and Pollutant retention time (τ) is proposed to evaluate the ventilation and Pollutant Removal performance of street canyons. Using computational fluid dynamics (CFD), the newly developed formulation is applied to two-dimensional (2D) idealized street canyons with different building-height-to-street-width (aspect) ratios. The Reynolds-averaged Navier-Stokes (RANS) equations equipped with the Renormalization Group (RNG) k − ɛ turbulence model is adopted. The accuracy of three numerical discretizations, including the 1st-order upwind, 2nd-order upwind and 3rd-order monotone upstream-centered schemes for conservation laws (MUSCL), are compared by considering the Pollutant conservation. It is found that the 1st-order upwind is not accurate enough for the Pollutant transport mainly due to its over dissipative nature while the 2nd-order upwind and 3rd-order MUSCL exhibit an error of 10%. The ACH and PCH are decomposed into the mean and turbulent components in which the roof-level transport processes are dominated by the turbulent component. The spatial distributions of the vertical wind velocity and Pollutant flux are also investigated to examine the ventilation and Pollutant Removal mechanisms of street canyons.