Heavy Metal Modelling Study over Italy: Effects of Grid Resolution, Lateral Boundary Conditions and Foreign Emissions on Air Concentrations

Heavy metals (HMs) are pollutants that have both anthropogenic and natural sources. In the last decade, the European Commission (EC) has imposed limit and target values for some of them that are toxic both for humans and for the environment. This study aims to assess the HM concentrations over Italy by means of the atmospheric modelling system (AMS) of the MINNI project. The AMS is based on the chemical transport model (CTM) FARM. The sensitivity of model simulations to horizontal grid resolution, lateral boundary conditions and the contribution of emissions from neighbouring countries has been also evaluated. The simulations have been carried out for the year 2005 considering a spatial resolution of 20 km over the Italian domain and 4 km over northern Italy (Po Valley). The CTM has been extended to take into account the HMs considered by EC directives such as arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb). Both anthropogenic and natural emissions have been considered in this study. Model results have been compared with available observations. Results show realistic concentration of HMs and suggest the importance of using boundary conditions, while foreign emissions have less impact. In addition, the present work highlights the necessity of more observations in space and time for a comprehensive validation of the model. High-resolution simulation gives more realistic pattern with respect to the low-resolution one for the highly polluted areas. However, future improvements require a better knowledge of the space/time distribution of the emissions, currently not available.