PM modelling assessment in Northern Italy C. Carnevale, G. Finzi, M. Volta Dipartimento di Elettronica per l’Automazione Università degli Studi di Brescia

Study domain 300x300km2 Milan domain

GAMES modelling system Diagnostic Model Output Land use Topography Local Measurements Radiosounding Emission inventories Meterological Model Emission Model Temporal Profiles 3D wind and temperature fields Turbolence and Boundary Layer parameters Emission Fields Initial and Boundary condition Pre-processors Boundary and Initial condition TCAM VOC/PM speciation Profiles 3D concentration fields Continental model output System Evaluation Tool

TCAM model Gas phase chemical mechanisms: SAPRC90, SAPRC97, COCOH97, CBIV 21 aerosol chemical species 10 Size classes Size varying during the simulation Fixed-Moving approach Processes involved: Condensation/Evaporation Nucleation Aqueous Chemistry TCAM is a multi-phase model implementing different chemical mechanism based on both lumped molecule and lumped structure approaches. The model includes 21 aerosol chemical compounds: 12 inorganics (H2O, SO4=, NH4+, Cl-, NO3-, Na+, H+, SO2(aq), H2O2(aq), O3(aq), crustal and elemental carbon) and 9 organics (a generic primary organic species and 8 classes of secondary organics), each split in 10 granulometric classes. The TCAM describes the particle dynamics by means of a fixed-moving approach. The particles of each size bin are considered composed by an internal core containing the non-volatile material (like elemental carbon, crustal and dust). The volatile material (like water, sulphate, ammonia and organic species) is supposed to reside in an outer shell of the particle whose dimension is evaluated by the model at each time step on the basis of the total mass and of the total number of suspended particles. Both shell and core fraction are supposed to be internally mixed. The processes considered by the model are: the condensation and evaporation of inorganic and organic compounds, the nucleation and the aqueous chemistry. Shell Core

TCAM simulation [CityDeltaII] base case simulation: 300 x 300 km2, 60 x 60 cells, cell resolution: 5x5 km2 11 vertical layers emission and meteorological fields: JRC initial and boundary conditions: EMEP simulation period: 1999 For the modelling application the domain has been divided into a grid of 60x60 square cells, with horizontal resolution of 5x5km2. The domain height is set to 4900 m above the terrain; 11 levels with growing height have been chosen: the lowest level is 20 m high. Simulations have been performed processing the meteorological and the emission fields provided by JRC and the initial and boundary conditions provided by a nesting procedure from the results of the EMEP Unified Model working at European scale. With these features the 1999 base case scenario has been simulated and validated in the frame of the CityDelta project, supplying pollutant hourly concentration fields. The run of a summer (6 months) simulation takes a few days of CPU time and this explains why TCAM cannot be directly integrated in an optimization procedure that should process hundreds of model runs. Keeping the same meteorology, two emission control scenarios (CLE - current legislation and MFR - most feasible reduction) reducing ozone precursor emissions up to 2010 have been simulated. The three scenario simulated ozone concentration have been used for the calibration of the source-receptor models.

winter PM10 mean concentrations (mg/m3) sulphate EC ammonium nitrate OC

summer PM10 mean concentrations (mg/m3) sulphate EC ammonium nitrate OC

PM10 modelling profiles 29.8 25.0 75.5 42.7 44.8 32.7 mg/m3

PM2.5 modelling profiles 26.2 20.7 67.5 35.4 39.6 27.4 mg/m3

conclusions higher concentrations in winter relevant PM secondary inorganic fraction in all sites significant winter EC+OC fraction in urban and industrial sites good agreement between model simulation chemical profiles and experimental campaign data might the model simulations be useful to support experimental campaigns?