Atmos. Chem. Phys. Discuss., 12, 16377-16406, 2012
© Author(s) 2012. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Factors determining the formation of secondary inorganic aerosol: a case study in the Po Valley (Italy)
S. Squizzato1, M. Masiol1, A. Brunelli1, S. Pistollato2, E. Tarabotti2, G. Rampazzo1, and B. Pavoni1
1DAIS – Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca' Foscari Venezia, Dorsoduro 2137, 30123 Venice, Italy
2Dipartimento Provinciale di Venezia, Agenzia Regionale per la Prevenzione e Protezione Ambientale del Veneto, Via Lissa 6, 30174 Mestre, Italy

Abstract. Physicochemical properties of aerosol were investigated by analyzing the inorganic water soluble content in PM2.5 samples collected in the eastern part of the Po Valley (Italy). In this area the EU limits for many air pollutants are frequently exceeded as a consequence of local sources and regional-scale transport of secondary inorganic aerosol precursors. Nine PM2.5-bound major inorganic ions (F-, Cl-, NO3-, SO42-, Na+, NH4+, K+, Mg2+, Ca2+) were monitored over one year in three sites categorized as semi-rural background, urban background and industrial. The acidic properties of the PM2.5 were studied by applying the recently developed E-AIM thermodynamic model 4. The experimental data were also examined in relation to the levels of gaseous precursors of SIA (SO2, NOx, NO, NO2) and on the basis of some environmental conditions having an effect on the secondary aerosols generation processes. A chemometric procedure using cluster analysis on experimental [NH4+]/[SO42-] molar ratio and NO3- concentration has been applied to determine the conditions needed for ammonium nitrate formation in different chemical environments. Finally, some considerations on the secondary inorganic aerosol formation and the most relevant weather conditions concerning the sulfate-nitrate-ammonium system were also discussed. The methods used can be easily applied to other environments to evaluate the physicochemical characteristics of aerosols and the climatic conditions necessary for the formation of ammonium sulfate and ammonium nitrate aerosols.

Citation: Squizzato, S., Masiol, M., Brunelli, A., Pistollato, S., Tarabotti, E., Rampazzo, G., and Pavoni, B.: Factors determining the formation of secondary inorganic aerosol: a case study in the Po Valley (Italy), Atmos. Chem. Phys. Discuss., 12, 16377-16406, doi:10.5194/acpd-12-16377-2012, 2012.
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