Ultrafine particles and PM1 measurements in a hot-spot pollution area : size distribution, mass closure and source apportionment

In urban areas, ultrafine particles and PM1 are of great concern because can deeply enter the respiratory system strongly affecting human health. Hot-spot pollution areas are peculiar sites where source emissions and meteorological conditions foster particulate matter accumulation and very high aerosol concentrations are often registered. The Po Valley is one of the main hot-spot pollution areas in Europe, especially during wintertime. Despite the high levels of PM registered in the area, little knowledge on PM1 and ultrafine particles composition and sources is available, apart from a couple of studies carried out by our group in 2002 and 2004 in the same area. This work aimed at a detailed physical and chemical characterisation of PM1 and ultrafine particles and at singling out major sources contributing to the high concentrations observed in the urban area. A critical comparison to the results obtained during the previous PM1 campaigns will be also shown. PM1 was sampled at an urban background station in Milan, Italy, during winter 2011-2012. Parallel PM1 sampling was carried out twice a day (07-16, 19-04) on PTFE and quartz fibre filters using two low-volume samplers for a total of about 300 samples. Mass concentration was determined by the gravimetric technique and all the PM1 samples were chemically characterised for elements, inorganic ions, levoglucosan, EC/OC and water soluble organic compounds. BC determination was also carried out on both PTFE and quartz fibre filters by a polar photometer (Vecchi et al., 2010; Vecchi et al., 2012). Moreover, BC concentrations in PM1 were monitored with a 5 minute resolution by a MAAP. The ultrafine fraction was characterised for number size distribution by an optical particle counter (range 0.25-32 \u3bcm in 31 size bins) and a differential mobility particle scanner (8-700 nm in 31 size bins). Moreover, parallel samplings using multistage cascade impactors (Dekati-SDI and nanoMOUDI) were collected on different substrates (polycarbonate membranes and quartz fibre filters) to gain information on the size-segregated chemical composition (elements, ions, and carbonaceous components). It is noteworthy that the detailed characterisation of size-segregated PM required the optimisation of the analytical techniques because of the small quantities of material to analyse and of the peculiarities of the PM deposits. Ancillary information on atmospheric dispersion conditions was available by 222Rn measurements and the main meteorological parameters (temperature, pressure, RH, solar radiation, wind speed and direction) were also monitored at the sampling site. PM1 data will be used to resolve the main sources in the area using Positive Matrix Factorization. This is important to develop suitable and efficient abatement strategies in an area heavily affected by high PM levels. Results obtained for size-segregated samples will be analysed using the MICRON inversion model aiming at the identification of the size-distribution modes for the different chemical components. These modes can track different formation processes adding useful information to the results obtained by PMF on the PM1 samples. Figure 1: example of DMPS data (Milan, 21 Jan 2012) Vecchi, R., Bernardoni, V., Broccoletti, S., Canepa, P., Cuccia, E., Massab\uf2, D., Paganelli, C., Piazzalunga, A., Prati, P., and Valli, G. (2010). Abstract 11E2, International Aerosol Conference 2010, Helsinki, August 29 - September 3, 2010. Vecchi, R., Valli, G., Bernardoni, V., Paganelli, C., and Piazzalunga, A. (2012). Abstract, European Aerosol Conference 2012, Granada, 2 \u2013 7 September, 201

‘Concentration and the chemical characterization of PM10 and PM2.5 in all the Italian territory’

In order to studying the concentration and the chemical characterization of atmospheric particulate in the different season in all the Italian territory, inside the SITECOS project (PRIN 2004), a gravimetric sampling campaigns have been conducted. The PM10 and PM2.5 samplings were placed at the same time in different sites along the Italian peninsula. The sampling sites were: Bari, Taranto, Pollino (m.1800, remote site), Catania, Sesto Fiorentino, Florence, Arezzo, Grosseto, Capannori-LU, Prato, Montale-PT (rural site), Bologna and Monte Cimone (m.2100, remote site on Italian Apennines), Padua, Milan, San Colombano (m.2300, remote site on Italian Alps), Trieste and San Rocco a Muggia (TS). Daily PM2.5 and PM10 samples have been collected, to do a \u201csampling bank \u201c, available for a further chemical / physical / toxicological characterization of atmospheric particulate Samples have been chemically characterized according to their main species: PAHs, inorganic ions and EC/OC in the PM2.5 samples; elements in the PM10 samples. In the Padana plain (Milan, Bologna, Padua) the PM concentration is uniform and a strong seasonal trend is observed, with the highest values in winter time and the lowest values in summer while PM concentration in S. Colombano and Monte Cimone sites show an opposite seasonality, with the highest values in summer and the lowest ones in winter. These data show a slight evolution during the winter\u2019s day because of the height of the dispersion layer, in connection with microclimatic parameters; for example in Milan city during acute cases of pollution, the height is no more that 300m (Ferrero et al., 2006). Remote sites of S. Colombano and Monte Cimone in the winter time are above the boundary layer while during summer period they are on it. In the center of Italy PM seasonality concentration is less important while in the South Italy and in Sicily there is any seasonal trend. The reasons are, in part, linked to the different meteoclimatic features present in the Italian peninsula. Chemical composition data show a significant differences. In the North of Italy there is a strong seasonality of ionic component; in particular, during the winter, the Nitrate concentration is higher than the Sulfate one while the situation is opposed in summer. Ammonium does not show a strong seasonality, but it remains pretty constant; the same applies to Carbon. In the South of Italy cities, SO , NO 3 - and NH 4 + , primary component of inorganic ions, they do not show a seasonality with a Sulfate concentration that is always higher than Nitrates. In the center of Italy the seasonality is less marked thanks to the inorganic ions. Sulfate and Nitrate are similar from a percentage point of view. Also PAHs (expressed in weight/weight, quality of particulate), in the Padana plain, shows a strong seasonality, with a high percentage in the winter season and a lower one in summer (Ravindra et al., 2006). Over the year concentrations are constant in South of Italy, while in the center area, the seasonality is less strong. The vehicles traffic source is estimated to be one of the main PM source in the Padana plain, while in the South of Italy there are other sources like photochemistry reactivity, Saharan Dust events, etc. These results show a different role of PM sources along the Italian peninsula and they carry fundamental information for a correct management of the complex problem on a national scale. Ferrero, L., Lazzati, Z., Lo Porto, C., Perrone, M.G., Petraccone, S., Sangiorgi, G., Bolzacchini, E., (2006) Vertical distribution of particulate matter in the urban atmosphere of Milan. Poster. International Aerosol Conference 2006. Ravindra, K., Bencs, L., Wauters, E., Hoog, J., Deutsch, F., Roekens, E., Bleux, N., Berghmans, P., Van Grieken, R., (2006) Seasonal and sitespecific variation in vapour and aerosol phase PAHs over Flanders (Belgium) and their relation with anthropogenic activities. Atmospheric Environment 40 (2006) 771-785