A practical green infrastructure intervention to mitigate air pollution in a UK school playground

Air pollution severely compromises children’s health and development, causing physical and mental implications. We have explored the use of site-specific green infrastructure (green barriers) in a school playground in Sheffield, UK, as an air-pollution-mitigation measure to improve children’s environment. The study assessed air quality pre-post intervention and compared it with two control sites. Nitrogen dioxide (NO2) and particulate matter <2.5 µm in size (PM2.5) concentration change was assessed via three methods: (1) continuous monitoring with fixed devices (de-seasonalised); (2) monthly monitoring with diffusion tubes (spatial analysis); (3) intermittent monitoring with a mobile device at children’s height (spatial analysis). De-seasonalised results indicate a reduction of 13% for NO2 and of 2% for PM2.5 in the school playground after two years of plant establishment. Further reductions in NO2 levels (25%) were observed during an exceptionally low mobility period (first COVID-19 lockdown); this is contrary to PM2.5 levels, which increased. Additionally, particles captured by a green barrier plant, Hedera helix ‘Woerner’, were observed and analysed using SEM/EDX techniques. Particle elemental analysis suggested natural and potential anthropogenic origins, potentially signalling vehicle traffic. Overall, green barriers are a valid complementary tool to improve school air quality, with quantifiable and significant air pollution changes even in our space-constrained site.