Quantifying the effect of urban tree planting on concentrations and depositions of PM10 in two UK conurbations

Trees are efficient scavengers of particulate matter and are characterised by higher rates of dry deposition than other land types. To estimate the potential of urban tree planting for the mitigation of urban PM10 concentrations, an atmospheric transport model was used to simulate the transport and deposition of PM10 across two UK conurbations (the West Midlands and Glasgow). Tree planting was simulated by modifying the land cover database, using GIS techniques and field surveys to estimate reasonable planting potentials. The model predicts that increasing total tree cover in West Midlands from 3.7% to 16.5% reduces average primary PM10 concentrations by 10% from 2.3 to 2.1 μg m−3 removing 110 ton per year of primary PM10 from the atmosphere. Increasing tree cover of the West Midlands to a theoretical maximum of 54% by planting all available green space would reduce the average PM10 concentration by 26%, removing 200 ton of primary PM10 per year. Similarly, for Glasgow, increasing tree cover from 3.6% to 8% reduces primary PM10 concentrations by 2%, removing 4 ton of primary PM10 per year. Increasing tree cover to 21% would reduce primary PM10 air concentrations by 7%, removing 13 ton of primary PM10 per year.