The importance of local scale for assessing, monitoring and predicting of air quality in urban areas

• Environmental Area Strategy is an integrated methodology focused on the neighbourhood size.
• It is shown the effectiveness of street trees in the PM10 removal.
• Street trees are able to reduce the 57% of annual total PM10 emissions.
• The neighbourhood represents an useful size for urban air quality assessment.
• Integrated planning would lead to greater mitigation of urban air quality.

The importance of the spatial scale for counteracting urban air pollution is highlighted in this work. In particular, the concept of Environmental Areas is used here in a wider sense than the current one. The Environmental Area is an area where the traffic conditions are more favourable for walkability and cycling compared to those of private motor vehicles. This work extends this concept to integrate several approaches coming from dimensional analysis, ecology, urban planning and transport engineering, to define a suitable spatial scale for an estimation of the PM10 removal through the street trees. Results highlight that, within the monitored area (the Monteverde neighbourhood, Rome—Italy), the street trees are able to remove 0.142 t ha−1 year−1 of PM10 (about the 57% of the total particulate emission) with a re-suspension from plant canopies of 4%. Results have also demonstrated how is important an effective management of trees and the choice of appropriate trees made in according to the leaves' characteristics but also related to urban context in which trees are placed. We highlight that integrated planning among different elements of the public urban space is of great importance for ameliorating the urban liveability. Moreover, we remark that this Environmental Areas-based approach contributes to promote in citizens a greater knowledge of the territory and awareness of the dynamics that affect it and consequently a wider participation to public decisions concerning the choice, implementation and management of the street trees, reduction of car-based mobility and increase of pedestrian and cyclist mobility.