Air Pollution Abatement Performances of Green Infrastructure in Open Road and Built-up Street Canyon Environments – A Review

Intensifying the proportion of urban green infrastructure has been considered as one of the remedies for air pollution levels in cities, yet the impact of numerous vegetation types deployed in different built environments has to be fully synthesised and quantified. This review examined published literature on neighbourhood air quality modifications by green interventions. Studies were evaluated that discussed personal exposure to local sources of air pollution under the presence of vegetation in open road and built-up street canyon environments. Further, we critically evaluated the available literature to provide a better understanding of the interactions between vegetation and surrounding built-up environments and ascertain means of reducing local air pollution exposure using green infrastructure. The net effects of vegetation in each built-up environment are also summarised and possible recommendations for the future design of green infrastructure are proposed. In a street canyon environment, high-level vegetation canopies (trees) led to a deterioration in air quality, while low-level green infrastructure (hedges) improved air quality conditions. For open road conditions, wide, low porosity and tall vegetation leads to downwind pollutant reductions while gaps and high porosity vegetation could lead to no improvement or even deteriorated air quality. The review considers that generic recommendations can be provided for vegetation barriers in open road conditions. Green walls and roofs on building envelopes can also be used as effective air pollution abatement measures. The critical evaluation of the fundamental concepts and the amalgamation of key technical features of past studies by this review could assist urban planners to design and implement green infrastructures in the built environment

Air pollution and meteorology monitoring report. Deliverable 5.2. Project iSCAPE, Grant Agreement number: 689954

This report documents good quality meteorological and air pollution data obtained as result of the experimental field campaigns carried out in the different iSCAPE cities, namely Bologna, Dublin, Guildford and Vantaa. We recall that these cities are those with a focus on \u201cphysical\u201d interventions, or rather on the evaluation of the impacts of Passive Control Systems (PCSs) on air pollution mitigation through the analysis of environmental data gathered during different monitoring campaigns, as described in D3.3. Other iSCAPE cities focused instead on behavioral interventions (Hasselt) and infrastructural solutions (Bottrop). The data obtained so far were carefully checked for their quality and their usage is twofold. From one hand measured data will be used for the validation of the model simulations run as part of other WPs (e.g. WP4 and WP6) and, on the other hand, they will provide the scientific basis to establish the efficacy of different PCSs including low boundary walls and green infrastructure (trees and hedges), in each city. Specifically, regarding this last goal, preliminary results show a strong dependency of the impact of the different PCSs on the local morphology of the analyzed urban environment and the local meteorological conditions impacts, leading to both mitigation and deterioration effects of air pollution. It is worth to recall that this is a preliminary version of the report which will be updated later by the end of the project when all the monitoring activities will be completed, and further analyses of the results will be carried out meanwhile. The instrumental setup and protocols, along with the description of the experimental sites, already presented in D3.3, are here summarized and updated. This report also provides some preliminary results about the efficacy of the different PCSs in contrasting/reducing air pollution and/or reducing the UHI (Urban Heat Island) effect at urban level, especially in the city of Bologna, where as noted in D1.4 and thoroughly studied in D6.1, the UHI phenomenon is large and show very strong diurnal variations. To this end, and for the purpose of detailing and analyzing the UHI phenomenon at the street/neighborhood scale, within the experimental campaigns conducted in Bologna, two intensive thermographic campaigns were performed, and this report presents the preliminary results obtained, which show well the efficacy of trees as regards the thermal comfort within the urban environment. This fulfils the objective of detailing air pollution levels and meteorological conditions in the target cities, as measured within the different pilots

The nexus between air pollution, green infrastructure and human health

Cities are constantly evolving and so are the living conditions within and between them. Rapid urbanization and the ever-growing need for housing have turned large areas of many cities into concrete landscapes that lack greenery. Green infrastructure can support human health, provide socio-economic and environmental benefits, and bring color to an otherwise grey urban landscape. Sometimes, benefits come with downsides in relation to its impact on air quality and human health, requiring suitable data and guidelines to implement effective greening strategies. Air pollution and human health, as well as green infrastructure and human health, are often studied together. Linking green infrastructure with air quality and human health together is a unique aspect of this article. A holistic understanding of these links is key to enabling policymakers and urban planners to make informed decisions. By critically evaluating the link between green infrastructure and human health via air pollution mitigation, we also discuss if our existing understanding of such interventions is sufficient to inform their uptake in practice. Natural science and epidemiology approach the topic of green infrastructure and human health very differently. The pathways linking health benefits to pollution reduction by urban vegetation remain unclear and the mode of green infrastructure deployment is critical to avoid unintended consequences. Strategic deployment of green infrastructure may reduce downwind pollution exposure. However, the development of bespoke design guidelines is vital to promote and optimize greening benefits, and measuring green infrastructure's socio-economic and health benefits are key for their uptake. Greening cities to mitigate pollution effects is on the rise and these need to be matched by scientific evidence and appropriate guidelines. We conclude that urban vegetation can facilitate broad health benefits, but there is little empirical evidence linking these benefits to air pollution reduction by urban vegetation, and appreciable efforts are needed to establish the underlying policies, design and engineering guidelines governing its deployment

The nexus between air pollution, green infrastructure and human health

Cities are constantly evolving and so are the living conditions within and between them. Rapid urbanization and the ever-growing need for housing have turned large areas of many cities into concrete landscapes that lack greenery. Green infrastructure can support human health, provide socio-economic and environmental benefits, and bring color to an otherwise grey urban landscape. Sometimes, benefits come with downsides in relation to its impact on air quality and human health, requiring suitable data and guidelines to implement effective greening strategies. Air pollution and human health, as well as green infrastructure and human health, are often studied together. Linking green infrastructure with air quality and human health together is a unique aspect of this article. A holistic understanding of these links is key to enabling policymakers and urban planners to make informed decisions. By critically evaluating the link between green infrastructure and human health via air pollution mitigation, we also discuss if our existing understanding of such interventions is enabling their uptake in practice. Both the natural science and epidemiology approach the topic of green infrastructure and human health very differently. The pathways linking health benefits to pollution reduction by urban vegetation remain unclear and that the mode of green infrastructure deployment is critical to avoid unintended consequences. Strategic deployment of green infrastructure may reduce downwind pollution exposure. However, the development of bespoke design guidelines is vital to promote and optimize greening benefits and measuring green infrastructure’s socio-economic and health benefits are key for their uptake. Greening cities to mitigate pollution effects is on the rise and these needs to be matched by scientific evidence and appropriate guidelines. We conclude that urban vegetation can facilitate broad health benefits, but there is little empirical evidence linking these benefits to air pollution reduction by urban vegetation, and appreciable efforts are needed to establish the underlying policies, design and engineering guidelines governing its deployment