Ranking current and prospective NO 2 pollution mitigation strategies: An environmental and economic modelling investigation in Oxford Street, London

Abstract

Air pollution continues to be a problem in the urban environment. A range of different pollutant mitigation strategies that promote dispersion and deposition exist, but there is little evidence with respect to their comparative performance from both an environmental and economic perspective. This paper focuses on examining different NO mitigation strategies such as trees, buildings facades coated with photocatalytic paint and solid barriers in Oxford Street in London. The case study findings will support ranking the environmental and economic impacts of these different strategies to improve personal exposure conditions on the footpath and on the road in a real urban street canyon. CFD simulations of airflow and NO dispersion in Oxford Street in London were undertaken using the OpenFOAM software platform with the k-ε model, taking into account local prevailing wind conditions. Trees are shown to be the most cost-effective strategy, with a small reduction in NO concentrations of up to 0.7% on the road. However, solid barriers with and without the application of photocatalytic paint and an innovative material (20 times more expensive than trees) can improve air quality on the footpaths more substantially, up to 7.4%, yet this has a significant detrimental impact on NO concentrations (≤23.8%) on the road. Photocatalytic paint on building surfaces presented a minimal environmental reductions (1.2%) and economic (>100 times more expensive than trees) mitigation strategy. The findings recognised the differences between footpath and road concentrations occurred and that a focused examination of three pollution hotspots can provide more cost effective pollution mitigation. This study considers how a number of pollutant mitigation measures can be applied in a single street canyon and demonstrates the strengths and weaknesses of these strategies from economic and environmental perspectives. Further research is required to extrapolate the findings presented here to different street geometries.

LES over RANS in building simulation for outdoor and indoor applications: A foregone conclusion?

“…6g) (e.g. Hanna et al 2006;Flaherty et al 2007;Baik and Park 2009;Lateb et al 2010Lateb et al , 2011Gousseau et al 2011a;Panagiotou et al 2013;van Hooff and Blocken 2013;Blocken et al 2016a;Antoniou et al 2017;Jeanjean et al 2017;Efthimiou et al 2017;Juan et al 2017;Toja-Silva et al 2017;Garcia-Sánchez et al 2017;Gao et al 2018;Peng et al 2018;Buccolieri et al 2018) and natural ventilation of buildings (e.g. Mochida et al 2005Mochida et al , 2006Horan and Finn 2008;Norton et al 2009;Blocken 2010a,b, 2013;Wu et al 2012; Martins and da Graça 2016; Aydin and Mirzaei 2017).…”

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

“…Computational fluid dynamics (CFD) simulations with established, previously validated models or models validated against data from previous studies or existing databases [80,97,98,[101][102][103][104][105][106][107][108][109] CFD simulations and on-site air quality measurements, or measurements of pollution deposition on plant samples using laboratory techniques or wind tunnel experiments [110][111][112] CFD simulations and drift flux model simulations [113] CFD simulations and drift flux model simulations and on-site air quality measurements [114,115] Mesoscale Weather Research and Forecasting (WRF) model simulations and CFD simulations [116] Mesoscale WRF model coupled with chemistry (WRF-Chem) and Building Effect Parameterization (BEP) simulations [117] At the local scale street canyons, including street canyon trees [101,104,105,109,113,114] and green walls and roofs [115], near-road vegetation [102,108,110,111] and urban green spaces [98,106,112] were investigated. In 3D simulations idealised models [101,105,106,[109][110][111][112]…”

“…For example, the results obtained for a road with a vegetation barrier on one side cannot be extrapolated for a street or avenue with vegetation on both sides because different design scenarios and conditions require individual case studies [111]. Other limitations are related to the currently most advanced and most commonly applied CFD approach because it cannot fully account for complex variations in wind strength and direction, dynamic chemical reactions, or for the effect of traffic turbulence on pollution dispersion [104]. Limited computational domain and types of vegetation can also be indicated [108].…”

“…It is also important to note that both economic and environmental perspectives should be taken into account in policy recommendations. For example, although the reductions of road-side NO 2 concentration levels due to the effect of trees were very small in comparison to those achieved with solid barriers, trees were still suggested as the most cost-effective mitigation strategy [104].…”

Impact of Economic Growth, Energy Use and Population Growth on Carbon Emissions in Sub-Sahara Africa

“…Economic growth plays a critical role in the improvement of the national output and improving living standards, reducing unemployment and reduction of nation debts [17,18]. The issue of economic growth has been greatly emphasized by many researchers [19][20][21][22] to be the result of carbon emissions. In the past years, there has been an intensification of environmental pollution in the Sub-Saharan Africa.…”