Estimating the removal of atmospheric particulate pollution by the urban tree canopy of London, under current and future environments

Urban green space and particularly the tree canopy have been highlighted as offering a mitigation potential against atmospheric particulate pollution. In this paper current and future particulate (PM10) deposition to the urban tree canopy of the Greater London Authority (GLA) was estimated. A modelling approach was used based on the Urban Forest Effects Model (UFORE) and a modified version. Here we give evidence showing that these deposition models can be adapted to run from annual mean meteorological and PM10 concentration data, thus providing a methodology to examine future scenarios. Depending on the modelling approach, the urban canopy of the GLA is currently estimated to remove between 852 and 2121 tonnes of PM10 annually; representing between 0.7% and 1.4% of PM10 from the urban boundary layer. Estimates of PM10 removal which take into account a planned increased in tree cover, from the current 20% to 30% of the GLA land area, suggest deposition of 1109–2379 tonnes (1.1–2.6% removal) by the year 2050. The evidence provided here suggests that the targeting of tree planting in the most polluted areas of the GLA and particularly the use of street trees which have the greatest exposure to PM10, would have the greatest benefit to future air quality. The increased deposition would be greatest if a larger proportion of coniferous to broadleaved trees were used at such sites.