Modelling emission scenarios variations: an inert-mode CALGRID long-term application over the Florence metropolitan area to improve PM10-related air quality standards

The RAMS-CALMET-CALGRID modelling system developed by the LaMMA consortium has been used as a supporting tool in the framework of the "MODIVASET" project promoted by the Tuscan Regional Government with the aim of modelling emission scenarios variations. The system is based on the RAMS meteorological model forecasting and the CALGRID photochemical grid dispersion model, being suitably modified for the present work to be applied for inert pollutants. As a matter of fact, the attention was paid to particulate matter (PM10) primary component, as well as Nitrogen Dioxides (NOx), which is one of main precursors of PM10 secondary inorganic component. Both pollutants have been treated as inert ones. A one-year long-term application of RAMS-CALMET-CALGRID has been carried out over the Florence metropolitan area, Italy. The study area is 49x40 Km2 wide, featuring a 1-Km spaced 3-D computational grid. The main project's aim is to assess possible air quality improvements after a number of interventions on emission scenarios have been planned by local authorities. Therefore, basing on IRSE regional emission inventory, two PM10 and NOx emission scenarios have been set: a present one, updated to 2003, and a future one, projected to years 2010-2012, where "business as usual" emission variations are supposed to occur. All types of emission sources have been taken into account, i.e. point, line and area (split into 4 sub-categories) ones. This enabled single contributions brought by any to be assessed, as well as the overall one. Summarizing, a total of 28 run combinations (2 scenarios by 2 pollutants by 7 source categories) have been performed by the modelling system. CALGRID-calculated PM10 and NOx concentrations resulting from present and future emission scenarios have been compared, both in terms of spatial pattern over the study area and local one to a number of chemical stations. The final result was a general NOx concentration reduction in the order of 10÷35%, particularly effective over the Florence and Prato urban areas. On the contrary, primary PM10 concentrations proved to decrease, about 15% over the Florence urban area, as well as increase, 10÷15% over the mountainous area Northwest to Pistoia. Summarizing, the proper use of an integrated modelling system proved to be a fundamental tool for planning emission scenarios variations to improve air quality standards. Moreover, methodologies implemented and results achieved in the present paper are in agreement with other similar scenarios analysis works.