Promoting a better understanding of green infrastructure in urban planning to reduce air pollution exposure

Abstract

BACKGROUND AND AIM: Green infrastructure (GI) is seen as a win-win solution to air pollution, reducing pollutant concentrations and thus, improving human health. However, the effects of GI on air quality are still unclear, and questions have been raised about the effectiveness of GI in mitigating air pollution. Before making generalisations about the benefit of GI to air quality, it is crucial to consider the GI-characteristics that influence air quality. So, to enhance the mitigation of air pollution, a holistic understanding of the effects of GI in cities is essential.This research reviews the academic literature addressing GI-related characteristics in cities, creating a holistic framework. METHODS: The mechanisms by which GI is considered to influence air quality were identified. A specific literature review was then conducted for each mechanism to extract the associated GI-characteristics. A holistic framework was created to help guide decision-makers in using GI solutions for improved air quality. RESULTS:Four mechanisms were identified by which GI influences air quality: deposition, dispersion, absorption, and biogenic emissions. Deposition is influenced by leaf form and micromorphological traits. The structure of the street, the meteorological conditions and the shape of the GI influence dispersion. Stomata conductance and chemical properties of the pollutant influence absorption. Plant emissions such as biogenic volatile organic compounds and pollen should be considered and minimised by appropriate species selection. Thus, maximising the positive effect of GI in cities on air quality will be the product of understanding a range of chemical and physical mechanisms in a highly site-specific context. CONCLUSIONS:Complex interactions between GI and site characteristics should be considered to maximise the benefits of GI in improving air quality. This research contributes to the air pollution mitigation field, explicitly helping to inform decision making for more health-promoting urban settings by optimising the expected benefits of GI through a holistic understanding of their impacts. KEYWORDS: Air pollution, built environment, and green spaces