Browsing by Author "Rinaldi, Matteo"
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- ItemEvidence for ambient dark aqueous SOA formation in the Po Valley, Italy(München : European Geopyhsical Union, 2016) Sullivan, Amy P.; Hodas, Natasha; Turpin, Barbara J.; Skog, Kate; Keutsch, Frank N.; Gilardoni, Stefania; Paglione, Marco; Rinaldi, Matteo; Decesari, Stefano; Facchini, Maria Cristina; Poulain, Laurent; Herrmann, Hartmut; Wiedensohler, Alfred; Nemitz, Eiko; Twigg, Marsailidh M.; Collett, Jeffrey L. Jr.Laboratory experiments suggest that water-soluble products from the gas-phase oxidation of volatile organic compounds can partition into atmospheric waters where they are further oxidized to form low volatility products, providing an alternative route for oxidation in addition to further oxidation in the gas phase. These products can remain in the particle phase after water evaporation, forming what is termed as aqueous secondary organic aerosol (aqSOA). However, few studies have attempted to observe ambient aqSOA. Therefore, a suite of measurements, including near-real-time WSOC (water-soluble organic carbon), inorganic anions/cations, organic acids, and gas-phase glyoxal, were made during the PEGASOS (Pan-European Gas-AeroSOls-climate interaction Study) 2012 campaign in the Po Valley, Italy, to search for evidence of aqSOA. Our analysis focused on four periods: Period A on 19–21 June, Period B on 30 June and 1–2 July, Period C on 3–5 July, and Period D on 6–7 July to represent the first (Period A) and second (Periods B, C, and D) halves of the study. These periods were picked to cover varying levels of WSOC and aerosol liquid water. In addition, back trajectory analysis suggested all sites sampled similar air masses on a given day. The data collected during both periods were divided into times of increasing relative humidity (RH) and decreasing RH, with the aim of diminishing the influence of dilution and mixing on SOA concentrations and other measured variables. Evidence for local aqSOA formation was only observed during Period A. When this occurred, there was a correlation of WSOC with organic aerosol (R2 = 0.84), aerosol liquid water (R2 = 0.65), RH (R2 = 0.39), and aerosol nitrate (R2 = 0.66). Additionally, this was only observed during times of increasing RH, which coincided with dark conditions. Comparisons of WSOC with oxygenated organic aerosol (OOA) factors, determined from application of positive matrix factorization analysis on the aerosol mass spectrometer observations of the submicron non-refractory organic particle composition, suggested that the WSOC differed in the two halves of the study (Period A WSOC vs. OOA-2 R2 = 0.83 and OOA-4 R2 = 0.04, whereas Period C WSOC vs. OOA-2 R2 = 0.03 and OOA-4 R2 = 0.64). OOA-2 had a high O ∕ C (oxygen ∕ carbon) ratio of 0.77, providing evidence that aqueous processing was occurring during Period A. Key factors of local aqSOA production during Period A appear to include air mass stagnation, which allows aqSOA precursors to accumulate in the region; the formation of substantial local particulate nitrate during the overnight hours, which enhances water uptake by the aerosol; and the presence of significant amounts of ammonia, which may contribute to ammonium nitrate formation and subsequent water uptake and/or play a more direct role in the aqSOA chemistry.
- ItemGlobal relevance of marine organic aerosol as ice nucleating particles(Katlenburg-Lindau : EGU, 2018) Huang, Wan Ting Katty; Ickes, Luisa; Tegen, Ina; Rinaldi, Matteo; Ceburnis, Darius; Lohmann, UlrikeIce nucleating particles (INPs) increase the temperature at which supercooled droplets start to freeze. They are therefore of particular interest in mixed-phase cloud temperature regimes, where supercooled liquid droplets can persist for extended periods of time in the absence of INPs. When INPs are introduced to such an environment, the cloud can quickly glaciate following ice multiplication processes and the Wegener–Bergeron–Findeisen (WBF) process. The WBF process can also cause the ice to grow to precipitation size and precipitate out. All of these processes alter the radiative properties. Despite their potential influence on climate, the ice nucleation ability and importance of different aerosol species is still not well understood and is a field of active research. In this study, we use the aerosol–climate model ECHAM6-HAM2 to examine the global relevance of marine organic aerosol (MOA), which has drawn much interest in recent years as a potentially important INPs in remote marine regions. We address the uncertainties in emissions and ice nucleation activity of MOA with a range of reasonable set-ups and find a wide range of resulting MOA burdens. The relative importance of MOA as an INP compared to dust is investigated and found to depend strongly on the type of ice nucleation parameterisation scheme chosen. On the zonal mean, freezing due to MOA leads to relative increases in the cloud ice occurrence and in-cloud number concentration close to the surface in the polar regions during summer. Slight but consistent decreases in the in-cloud ice crystal effective radius can also be observed over the same regions during all seasons. Regardless, MOA was not found to affect the radiative balance significantly on the global scale, due to its relatively weak ice activity and a low sensitivity of cloud ice properties to heterogeneous ice nucleation in our model.
- ItemThe impact of biomass burning and aqueous-phase processing on air quality: A multi-year source apportionment study in the Po Valley, Italy(Katlenburg-Lindau : EGU, 2020) Paglione, Marco; Gilardoni, Stefania; Rinaldi, Matteo; Decesari, Stefano; Zanca, Nicola; Sandrini, Silvia; Giulianelli, Lara; Bacco, Dimitri; Ferrari, Silvia; Poluzzi, Vanes; Scotto, Fabiana; Trentini, Arianna; Poulain, Laurent; Herrmann, Hartmut; Wiedensohler, Alfred; Canonaco, Francesco; Prévôt, André S.H.; Massoli, Paola; Carbone, Claudio; Facchini, Maria Cristina; Fuzzi, SandroThe Po Valley (Italy) is a well-known air quality hotspot characterized by particulate matter (PM) levels well above the limit set by the European Air Quality Directive and by the World Health Organization, especially during the colder season. In the framework of Emilia-Romagna regional project "Supersito", the southern Po Valley submicron aerosol chemical composition was characterized by means of high-resolution aerosol mass spectroscopy (HR-AMS) with the specific aim of organic aerosol (OA) characterization and source apportionment. Eight intensive observation periods (IOPs) were carried out over 4 years (from 2011 to 2014) at two different sites (Bologna, BO, urban background, and San Pietro Capofiume, SPC, rural background), to characterize the spatial variability and seasonality of the OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA accounts for averages of 45 ± 8 % (ranging from 33 % to 58 %) and 46 ± 7 % (ranging from 36 % to 50 %) of the total non-refractory submicron particle mass (PM1-NR) at the urban and rural sites, respectively. Primary organic aerosol (POA) comprises biomass burning (23±13 % of OA) and fossil fuel (12±7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more significant at the rural site (urban / rural concentration ratio of 0.67), but it is also an important source of POA at the urban site during the cold season, with contributions ranging from 14 % to 38 % of the total OA mass. Secondary organic aerosol (SOA) contributes to OA mass to a much larger extent than POA at both sites throughout the year (69 ± 16 % and 83 ± 16 % at the urban and rural sites, respectively), with important implications for public health. Within the secondary fraction of OA, the measurements highlight the importance of biomass burning aging products during the cold season, even at the urban background site. This biomass burning SOA fraction represents 14 %-44 % of the total OA mass in the cold season, indicating that in this region a major contribution of combustion sources to PM mass is mediated by environmental conditions and atmospheric reactivity. © 2020 Author(s).
- ItemSize-resolved aerosol composition at an urban and a rural site in the Po Valley in summertime: implications for secondary aerosol formation(München : European Geopyhsical Union, 2016) Sandrini, Silvia; van Pinxteren, Dominik; Giulianelli, Lara; Herrmann, Hartmut; Poulain, Laurent; Facchini, Maria Cristina; Gilardoni, Stefania; Rinaldi, Matteo; Paglione, Marco; Turpin, Barbara J.; Pollini, Francesca; Bucci, Silvia; Zanca, Nicola; Decesari, StefanoThe aerosol size-segregated chemical composition was analyzed at an urban (Bologna) and a rural (San Pietro Capofiume) site in the Po Valley, Italy, during June and July 2012, by ion-chromatography (major water-soluble ions and organic acids) and evolved gas analysis (total and water-soluble carbon), to investigate sources and mechanisms of secondary aerosol formation during the summer. A significant enhancement of secondary organic and inorganic aerosol mass was observed under anticyclonic conditions with recirculation of planetary boundary layer air but with substantial differences between the urban and the rural site. The data analysis, including a principal component analysis (PCA) on the size-resolved dataset of chemical concentrations, indicated that the photochemical oxidation of inorganic and organic gaseous precursors was an important mechanism of secondary aerosol formation at both sites. In addition, at the rural site a second formation process, explaining the largest fraction (22 %) of the total variance, was active at nighttime, especially under stagnant conditions. Nocturnal chemistry in the rural Po Valley was associated with the formation of ammonium nitrate in large accumulation-mode (0.42–1.2 µm) aerosols favored by local thermodynamic conditions (higher relative humidity and lower temperature compared to the urban site). Nocturnal concentrations of fine nitrate were, in fact, on average 5 times higher at the rural site than in Bologna. The water uptake by this highly hygroscopic compound under high RH conditions provided the medium for increased nocturnal aerosol uptake of water-soluble organic gases and possibly also for aqueous chemistry, as revealed by the shifting of peak concentrations of secondary compounds (water-soluble organic carbon (WSOC) and sulfate) toward the large accumulation mode (0.42–1.2 µm). Contrarily, the diurnal production of WSOC (proxy for secondary organic aerosol) by photochemistry was similar at the two sites but mostly affected the small accumulation mode of particles (0.14–0.42 µm) in Bologna, while a shift to larger accumulation mode was observed at the rural site. A significant increment in carbonaceous aerosol concentration (for both WSOC and water-insoluble carbon) at the urban site was recorded mainly in the quasi-ultrafine fraction (size range 0.05–0.14 µm), indicating a direct influence of traffic emissions on the mass concentrations of this range of particles.