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Secondary inorganic aerosol in the Milan area: assessing the role of the main emission sources

pubblicazioni - Articolo

Secondary inorganic aerosol in the Milan area: assessing the role of the main emission sources

the main emission sources Guido Pirovano*, Marco Bedogni **, Sergio Casadei** Urban and regional Air Quality. Advances in chemistry transport modelling: experiences in USA and Italy Milano, 6 Novembre 2008 PRESENTAZIONE POWER POINT * CESI RICERCA ** AMA AGENZIA MOBILITA’ E AMBIENTE DI MILANO Fine particulate is now widely recognised as the main threat to human health from air pollution. Recent review studies have highlighted that 20-30% of the European urban population lives in cities where EU air quality limit values for PM10 were exceeded between 1997 and 2004 (EEA, 2007). Due to its peculiar meteorological conditions, the Milan area is subject to very critical conditions with frequent exceedances of the air quality standards. Moreover, specific field campaigns have clearly highlighted that secondary compounds represent the most relevant fraction of background PM concentrations at both urban and rural sites (Lonati et. al., 2005). In order to better understand the key processes underlying the development of the secondary aerosol fraction in the Milan area, the CAMx model (Environ, 2006) has been applied over the whole year 2004. CAMx has been implemented jointly to the PSAT (Yarwood et al., 2004) algorithm that allows to discriminate the contribution of different emission sectors and areas to the modelled PM concentrations. More precisely, this work describes the results of the CAMx modelling system simulations, performed over a 300×300 km 2 domain focused on the Milan area, in the framework of the CityDelta III project (http://aqm.jrc.it/citydelta). Due to a clear lacking in the CAMx reconstruction of the SOA concentration, the analysis has been focused only on the secondary inorganic compounds. In particular, thanks to the ability of the PSAT algorithm, a quantitative evaluation of the role played by the different sources as well as an analysis of the transformation paths have been carried out and discussed. Obtained results highlighted that road transport is the most relevant sector contributing more than 25% to the PM10 yearly mean in Milan, followed by agriculture and domestic heating. The source apportionment analysis also revealed that more than 80% of the PM10 is due to emissions outside of Milan. The analysis has also highlighted that the contribution of the city emissions drops very quickly moving outside the city, being less than 3% by 40 km far from Milan. Finally, the investigation of the conversion ratios put in evidence that SIA production arises in a very complex framework and the relationship between gas precursors can give rise to locally different behaviours in function of several factor such as: the absolute amount of emission precursors; the relative weight of the different precursors; the region extent; the plume age; the meteorological conditions. Examples of such a variability will be illustrated and discussed. EEA, 2007. Air pollution in Europe 1990-2004. EEA report, 2-2007. ENVIRON Corporation, 2006. User’s guide to the Comprehensive Air quality Model with extension (CAMX) ver 4.42. Technical report. Lonati, G., Giugliano, M., Butelli, P., Romele, L., Tardivo, R., 2005. Major chemical components of PM2.5 in Milan (Italy). Atmospheric Environment 39, 1925–1934. Yarwood G., R. Morris, and G. Wilson, 2004. Particulate Matter Source Apportionment Technology (PSAT) in the CAMx Photochemical Model. NATO International Technical Meeting, Banff, Canada (October 2004)

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