Assessing Ozone Distribution Vertically and Horizontally in Urban Street Canyons Based on Field Investigation and ENVI-met Modelling

Chunping Miao,Shuai Yu,Wei Chen

doi:10.3390/buildings12030262

Chunping Miao, Shuai Yu + Show 1 more

Open Access

https://doi.org/10.3390/buildings12030262

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Abstract

High concentrations of ozone (O3) is a major air problem in urban areas, which creates a serious threat to human health. Urban street canyon morphology plays a key role in air pollutant dispersion and photochemical reaction rate. In this study, a one-year observation at three height levels was performed to investigate the O3 distribution vertically in a street canyon of Shenyang. Then, field investigation and ENVI-met modelling were conducted to quantify the influence of street canyon morphology and microclimatic factors on O3 distribution at the pedestrian level. All O3 concentrations at the three height levels were high from 1:00 p.m. to 4:00 p.m. Both O3 concentrations at pedestrian level and the middle level in the canyon were 40% higher than at roof level. O3 accumulated in the canyons rather than spread out. The in-canyon O3 concentrations had significantly positive correlations with building height, aspect ratio, sky view factor, air temperature, and wind speed. Both field investigation and ENVI-met modelling found high O3 concentrations in medium canyons. Photochemical reaction intensity played a more important role in in-canyon O3 distribution than dispersion. Wide canyons were favorable for removing O3.

Highlights

The UN Sustainable Development Goals (SDGs) state that good health and wellbeing and sustainable cities and communities are integral to achieving the SDGs [1,2]
Street canyon morphology can be characterized as building height (BH), aspect ratio (AR, building height/street width), and sky view factor (SVF) [16,17,18]
Variations and daily variations of O3 concentration were examined in a street canyon at three height levels: pedestrian level, middle level, and roof level

Summary

Introduction

The UN Sustainable Development Goals (SDGs) state that good health and wellbeing and sustainable cities and communities are integral to achieving the SDGs [1,2]. The increasing urbanization and industrial development makes air pollution a serious problem in urban areas [3,4,5]. The buildings along the two sides of the street may hinder the dispersion of pollutant emissions from traffic, leading to higher pedestrian exposure to the pollutants inside the canyon [12]. Street canyon morphology can be characterized as building height (BH), aspect ratio (AR, building height/street width), and sky view factor (SVF) [16,17,18]. Decreasing the street aspect ratio or increasing the length might improve the rate of pollutant removal through turbulent diffusions across canopy roofs in canyons with uniform heights [19,20,21,22]. The O3 concentrations in street canyons show a distinct separation between the lower and upper regions, with an upward dispersion [24]

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