Air pollution in a microclimate; the impact of different green barriers on the dispersion

This paper studies the impact of different green barriers on the dispersion of air pollution in a neighbourhood. The study was performed with reference to air quality conditions in Manchester, UK. Manchester experiences a high level of NO₂. Measured results showed that the average annual concentration level in 2018 was very close to the limit defined by European Union legislation. Maximum and minimum NO₂ concentrations occurred during the winter and summer, respectively. Simulations of the dispersion of air pollution in a hypothetical neighbourhood showed that NO₂ level was decreased by the increase of air temperature during the simulated day. In four perturbation scenarios, hedges and trees with different heights were added to the neighbourhood as green barriers. Hedges increased the pollution level near the street at the pedestrian level as a result of the reduced wind speed. The simulations demonstrated that using the trees facilitated the dispersion of pollution.