Secondary inorganic aerosol evaluation: Application of a transport chemical model in the eastern part of the Po Valley

- A photochemical model has been used to study SIA distribution in the Po Valley.
- Good performance has been reached in spatial and temporal distribution.
- Concentrations were related to gaseous precursors and to the emission sources.
- Relation between model overestimation, input and boundary conditions was discussed.
- Specific ratios and a no-boundary simulation were used to assess SIA formation.

Secondary inorganic aerosol (SIA) represents an important component of fine particulate matter in Europe. A photochemical model has been used to assess the distribution of secondary inorganic ions (sulfate, nitrate and ammonium) in the eastern part of the Po Valley, close to Venice. Specific meteorological and environmental conditions and very highly urbanized and industrialized areas make this domain one of the most polluted in Europe. Several studies have been conducted to assess particulate matter (PM10 and PM2.5) areal distribution. However, SIA formation dynamics are still a research subject especially in the transition environments, where the changes in the orography and in the land-use can affect air mass movements and atmospheric composition. This paper is a first attempt to simulate SIA distribution by using a photochemical model in the sea/land Venice transition area. Moreover, a modeling approach with clean boundary conditions has been used to check local and regional influence on SIA levels in the domain. Results reveal that, despite the importance of regional influences, local formation processes are important in SIA distribution especially during warm periods. SO42− and NH4+ are more linked to emission sources distribution than NO3− that tends to be more diffused in the study area. The use of a photochemical model, suitably tested in a such complex area, can improve air pollution knowledge and can help in air quality decision making.