Urban green and its relation with air pollution: ecological studies in the Metropolitan area of Rome

Abstract

Tropospheric ozone (O3) and Particulate Matter (PM) have become a major concern in most
European cities. In particular, in Italy the O3 concentrations exceed the limits established for the protection of
both human health and vegetation. More integrative studies are revealing that urban trees could concretely
help in improving air quality, not only because of their well known aesthetic and recreational benefit, but also
for their capability to reduce air temperature and to remove air pollutants. This reduction takes place both
directly, by dry deposition to plant surfaces and uptake through stomata, and indirectly, by mitigation of the
urban heat island intensity by canopy transpiration and building shading, that lowers the activity of chemical
reactions that led to the formation of photochemical pollutants in air. This is of particular importance
especially for those cities located in the Mediterranean Basin, whose urban vegetation is often characterized
by VOC-emitting species that can contribute significantly to the O3 formation and destruction dynamics. The
aim of this paper is to present a short review of ecological research performed on vegetation of the
metropolitan area of Rome, at different spatial and temporal scale, in order to evaluate the functional role of
urban green to monitor and improve urban air quality. In the frame of the project HEREPLUS (EU FP7), all of
this information, opportunely integrated with climatic and pollutant data, will be implemented in a GIS and,
by the use of geo-statistical methods, the ameliorating effect of urban vegetation will be quantified and
mapped.