Eliana Pecorari

Using a photochemical model to assess the horizontal, vertical and time distribution of PM2.5 in a complex area: Relationships between the regional and local sources and the meteorological conditions

A photochemical transport model has been implemented to assess the PM(2.5) spatial and temporal distribution in Venice-Mestre. This is a large city of the eastern Po Valley, which is recognized having among the highest levels of many air pollutants in Europe. This study is a first attempt to evaluate PM(2.5) distribution in such a complex ecosystem strongly affected by several different environments (the adjacent Alps, the lagoon and the sea) that create a spatial discontinuity of climate. Model performance was tested with experimental results. Samples have been collected in three sites representative of different emission characteristics. A second simulation was performed with clean boundary conditions to check the influence of the background concentrations on the study domain. Local and regional contributions were found to be strongly dependent on seasonal conditions and on local meteorology. A further analysis was conducted to predict the PM(2.5) distribution with respect to air mass movements. The non-homogeneity of surfaces affects the Planetary Boundary Layer (PBL) behavior. This consequently influences the vertical distribution of PM(2.5) especially during cold seasons and on occasion of particular meteorological events.

Potentially Harmful Elements in the Atmosphere

The atmosphere represents a complex system influenced by the chemical and physical processes that occur at the Earth surface. These processes include emissions, transport, lifetimes and fates of several anthropogenic and biogenic/geogenic chemicals emitted from a wide variety of sources. Among these chemicals, some are considered air pollutants, i.e. any substance present in ambient air and likely to have harmful effects on human health and/or the environment as a whole. Metals, and in general elements, are natural components of the earth’s crust and constituents of all ecosystems. In the atmosphere, they are mainly related to particle phase but also they can be present in a liquid phase due to the dissolution of aerosol particles in the water drops. Whatever their origin, both natural and anthropogenic, most elements, and in particular heavy metals, are dangerous because they tend to bio-accumulate in the human body.