Impact of local urban design and traffic restrictions on air quality in a medium-sized town

Abstract

Traffic is the major air pollution source in most urban areas. Nowadays, most of the strategies carried out to improve urban air quality are focused on reducing traffic emissions. Nevertheless, acting locally on urban design can also reduce levels of air pollutants. In this paper, both strategies are studied in several scenarios for a medium-sized town of the Basque Country (Spain). Two main actions are analysed in order to reduce traffic emissions: (1) minor extension ofa pre-existing low emission zone (LEZ); (2) substitution of 10% of passenger cars that are older than 5 years by hybrid and electric vehicles. Regarding local urban design, three alternatives for the development of one side of a street canyon are considered: (1) a park with trees; (2) an open space without obstacles; (3) a building. Two different urban traffic dispersion models are used to calculate the air quality scenarios: PROKAS (Gaussian&box) to analyse the reduction of traffic emissions in the whole urban area and WinMISKAM (CFD) to evaluate specific urban designs. The results show the effectiveness of the analysed actions. On one hand, the definition of a small LEZ, as well as the introduction in 2015 of vehicles with new technology (hybrid and electric), results in minor impacts on PM10 and NO2 ambient concentrations. On the other hand, local urban design can cause significant variation in spatial distribution ofpollutant concentrations emitted inside street canyons. Consequently, urban planners should consider all these aspects when dealing with urban air pollution control.

PM2.5 Concentration Differences between Various Forest Types and Its Correlation with Forest Structure

“…This may occur because the PM2.5 spreads C o n t r o l C r a b a p p l e C h e r r y P e a c h A i l a n t h u s S c h o l a r C a t a l p a W h i t e w a x B l a c k more slowly in forests than in the control area, and PM2.5 accumulated in forests. In addition, breezes may lead to PM2.5 resuspension on leaves, and trees emit BVOCs that can react with NOx and O3 to form aerosols during the daytime [16,17]. In contrast, photosynthesis stops and most stomata close at night.…”

“…Leaves and branches can directly capture or retain PM2.5 from the air. Vegetation can intercept particulate matter in some regions [12][13][14][15][16][17]. Trees can also be a source of air pollutants; they emit biogenic volatile organic compounds (BVOCs).…”

Developing Community-Level Policy and Practice to Reduce Traffic-Related Air Pollution Exposure

“…52,53,54,55 In addition, garages and street parking could be distributed so as to decrease driving or low emissions zones could substitute some of the vehicle fleet with electric vehicles. 56,57 .…”

“…Vegetation along the side of a busy road can reduce air pollution behind the vegetative barrier by less than 40%, although results vary greatly by wind direction and study 63,64 . When planning urban vegetation, it is important to note that vegetation in street canyons can increase pollutant concentrations by as much as 33% due to decreasing wind flow and ventilation 65,66,67,68,69 . Off-site, solid or vegetative noise barriers along highways can decrease the amount of air pollution reaching neighborhoods 70,71 .…”

A Novel Approach in Quantifying the Effect of Urban Design Features on Local-Scale Air Pollution in Central Urban Areas

“…Physical dispersion modeling studies have also been used to establish the effect of some urban design features on local air pollution. 12 However, dispersion models require a large amount of often uncertain or unavailable input data (such as long-term data on wind variables), carry high implementation costs, and rely on mechanical processes associated with dispersion being adequately captured by the model. 11 In complex urban environments, LUR models have been found to provide comparable results when compared to predictions from physical-based dispersion models 13,14 with significantly reduced complexity, computational requirements, and data input.…”