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Research shows pollution dispersion in cities is improved by trees

Trees in cities throughout the UK could be significantly improving the quality of the air we breathe by decreasing pollution levels for pedestrians, researchers Department of Physics and Astronomy have suggested in a new study.

The team found that trees have a regionally beneficial impact by increasing turbulence and reducing ambient concentrations of road traffic emissions – by seven per cent in Leicester City at pedestrian height on average.

While previous studies have suggested that trees trap pollution by constructing wind flow in street canyons, the new study focuses on the effectiveness of trees at dispersing road traffic emissions on a city scale.

PhD researcher Antoine Jeanjean who led the research said: “Predicting the concentration of air pollutants is essential for monitoring air quality in cities. We focused the study on the city centre of Leicester where you have a high density of buildings and traffic.

“Our fears of trees trapping pollution around streets were revealed to be unfounded. In some situation they can increase pollution locally but on average their impact is beneficial in terms of pollutants dispersion.”

The research team looked at ways trees could help to reduce air pollution in cities. To do this, they created a model with aerial mapping company Bluesky based on 3D representation of the city of Leicester with buildings, road and trees databases.

The study found that while trees reduced air quality in some street canyons in the city of Leicester by trapping pollution, they globally decrease the amount of pollutants around pedestrians within the city as a whole.

A video of Dr Roland Leigh from the Department of Physics and Astronomy discussing air quality research is available here:

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