Modelling PM10 removal in three Italian coastal Metropolitan Cities along a latitudinal gradient

Air pollution is regarded as the largest environmental risk factor in Europe, and Particulate Matter (PM) is considered one of the most harmful pollutants. Among the Ecosystem Services (ESs) it provides, the Urban Green Infrastructure (UGI) is capable of capturing and adsorbing pollutants through removal mechanisms. As envisaged in the National Plan for Recovery and Resilience (PNRR), Italy has planned on investing about EUR 300 million of the Next Generation EU funds in urban reforestation programs that will target Italian Metropolitan Cities (MCs). Successful implementation of such interventions is underpinned by a thorough knowledge of the presence and distribution of existing vegetation and its capacity to deliver ESs. In the present study, we selected three Italian coastal MCs along a latitudinal gradient, namely Genoa, Bari, and Reggio Calabria, and assessed the regulating ES of PM removal by urban and peri-urban forests in both biophysical and monetary terms. In 2019, the total PM removal in the MCs of Genoa, Bari and Reggio Calabria amounted to 5,331, 363, and 4,248 Mg respectively, for a corresponding monetary value of EUR 536, 39, and 435 million. Our analyses were conducted on a seasonal basis and further aimed at investigating the role of functional diversity in ES provision. According to our findings, in all MCs the highest annual average PM removal efficiencies were exhibited by the evergreen broadleaves; deciduous broadleaves also displayed high efficiency values, despite being characterized by a marked seasonality caused by leaf abscission. Conifers proved less efficient, although our findings may indicate a good response to a condition of multi-stress. Maintaining a functionally-mixed species composition in the UGIs is desirable for guaranteeing the continuous provision of ESs throughout the year. In conclusion, our results provide useful insights to support the sustainable planning and management of UGIs, as envisaged by the United Nation's 2030 Agenda for Sustainable Development.