Source apportionment of PM10 in the Western Mediterranean based on observations from a cruise ship

Abstract Two intensive PM10 sampling campaigns were performed in the summers of 2009 and 2010 on the ship Costa Pacifica during cruises in the Western Mediterranean. Samples, mainly collected on an hourly basis, were analysed with different techniques (Particle Induced X-Ray Emission, PIXE; Energy Dispersive - X Ray Fluorescence, ED-XRF; Ion Chromatography, IC; Thermo-optical analysis) to retrieve the PM10 composition and its time pattern. The data were used for obtaining information about the sources of aerosol, with a focus on ship emissions, through apportionment using chemical marker compounds, correlation analysis and Positive Matrix Factorization (PMF) receptor modelling. For the campaign in 2010, 66% of the aerosol sulphate was found to be anthropogenic, only minor contributions of dust and sea salt sulphate were observed while the biogenic contribution, estimated based on the measurements of MSA, was found to be more important (26%), but influenced by large uncertainties. V and Ni were found to be suitable tracers of ship emissions during the campaigns. Four sources of aerosol were resolved by the PMF analysis; the source having the largest impact on PM10, BC and sulphate was identified as a mixed source, comprising emissions from ships. The correlations between sulphate and V and Ni showed the influence of ship emissions on sulphate in marine air masses. For the leg Palma–Tunis crossing a main ship route, the correlations between aerosol sulphate and V and Ni were particularly strong (r2 = 0.9 for both elements)

A new methodology to assess the performance and uncertainty of source apportionment models II: The results of two European intercomparison exercises

The performance and the uncertainty of receptor models (RMs) were assessed in intercomparison exercises employing real-world and synthetic input datasets. To that end, the results obtained by different practitioners using ten different RMs were compared with a reference. In order to explain the differences in the performances and uncertainties of the different approaches, the apportioned mass, the number of sources, the chemical profiles, the contribution-to-species and the time trends of the sources were all evaluated using the methodology described in Belis et al. (2015). In this study, 87% of the 344 source contribution estimates (SCEs) reported by participants in 47 different source apportionment model results met the 50% standard uncertainty quality objective established for the performance test. In addition, 68% of the SCE uncertainties reported in the results were coherent with the analytical uncertainties in the input data. The most used models, EPA-PMF v.3, PMF2 and EPA-CMB 8.2, presented quite satisfactory performances in the estimation of SCEs while unconstrained models, that do not account for the uncertainty in the input data (e.g. APCS and FA-MLRA), showed below average performance. Sources with well-defined chemical profiles and seasonal time trends, that make appreciable contributions (>10%), were those better quantified by the models while those with contributions to the PM mass close to 1% represented a challenge. The results of the assessment indicate that RMs are capable of estimating the contribution of the major pollution source categories over a given time window with a level of accuracy that is in line with the needs of air quality management

Brown carbon and thermal-optical analysis: A correction based onoptical multi-wavelength apportionment of atmospheric aerosols

reserved4siThermo-optical analysis is widely adopted for the quantitative determination of total, TC, organic, OC and elemental, EC, Carbon in aerosol samples collected on quartz fibre filters. Nevertheless, the methodology presents several issues in particular about the artefacts related to the formation of pyrolytic carbon. It is usually neglected the uncertainty due to the possible presence of brown carbon (BrC) in the sample under analysis, i.e. the optically active fraction of OC produced by biomass burning and with characteristics intermediate between OC and EC. We introduce here a novel correction to the standard thermooptical protocol based on the determination of the fraction of the sample absorbance due to the (possible) presence of BrC. This is achievable thanks to the coupled use of the Multi Wavelength Absorbance Analyser (MWAA) of the University of Genoa and a standard Sunset Inc. EC/OC analyser. Our correction provides a firmer OC/EC separation as well as an operative quantification of the BrC mass. The methodology has been validated against independent determination of the levoglucosan content in the same filters sent to the Sunset analysis. Corrections up to 23% in the OC and EC values, determined via the standard and new thermo-optical analysis, have been found in a set of PM10 (i.e. Particulate Matter with aerodynamic diameter less than 10 mm) samples collected wintertime at a mountain site in Northern Italy.mixedMassabò, D.; Caponi, L.; Bove, M.C.; Prati, P.Massabo', Dario; Caponi, L.; Bove, MARIA CHIARA; Prati, Paol

Size-resolved comprehensive characterization of airborne particulate matter

An update of a methodology to extract both the size-segregated source apportionment of atmospheric aerosol and the size distribution of each detected element or compound, is presented. The approach is based on the parallel use of standard low-volume samplers to collect particulate matter (PM) and of an Optical Particle Counter (OPC). The methodology was introduced and validated in previous works for the average size distribution of elemental components of PM: it has now been extended to PM compounds such as ions and carbonaceous aerosol (namely, organic end elemental carbon, OC and EC). Furthermore, the methodology has been now adopted in the frame of a field campaign, proving that it is able to provide not only an average size distribution but also information on the time evolution of the size distribution of specific PM species. Samples were collected in the urban area of Genoa (Italy) and their composition was measured by Energy Dispersive X-ray Fluorescence (ED-XRF), Ion Chromatography (IC) and Thermo-optical analysis. Positive Matrix Factorization (PMF) was applied to time series of daily concentration values in PM10 and PM2.5 (i.e. fraction of PM mass with aerodynamic diameter lower that 10 mm and 2.5 mm, respectively) to identify major PM sources, and both PM mass concentration and sizesegregated particle number concentration were apportioned. Seven and six sources were respectively resolved in PM10 and PM2.5, with processes related to secondary aerosol formation accounting for about 53% and 57% of PM levels in the two fractions. The new methodology is complementary to sizesegregated PM sampling, and it was actually tested against a 13-stage nanoMOUDI cascade impactor. Size distributions obtained with the new methodology and directly measured by the nanoMOUDI turned out to be in good agreement (R2 > 0.60) with discrepancies observed for SO4 only

Characterisation and source apportionment of PM10 in an urban background site in Lecce

The analysis reported in thiswork has been performed to characterise PM10concentrationmeasured in an urban background site in Lecce (Apulia region, Italy). PM10 concentration and its inorganic chemical composition have been studied using three procedures: a qualitative analysis of the correlation coefficients between the different species and of the crustal enrichment factor; the cluster analysis (CA) and the principal component analysis (PCA). The results of the three procedures are in good agreement. The five groups identified by the CA correspond to the five principal components obtained with the PCA and they reflect the results qualitatively inferred using the two-species correlation coefficients. The CA results helped in putting in evidence a correlation between Ni, V and sulphate that was less evident in the PCA. The relative abundance of V is larger with wind fromtheNNWdirectionswhere themain industrial sites of the region are located. This suggests the presence of anthropogenic inorganic secondary aerosol generated by a common source of V and SO2 that are likely the industrial releases and the ship emissions. The absolute PCA (APCA) allowed the quantitative apportionment of the five components observed: crustal matter (49.5%), secondary inorganic aerosol (24.1%), marine aerosol (6.3%), traffic (16.5%), and industrial (2.1%). Observed PM10 concentration clearly shows a seasonal pattern, opposite to the one observed in the northern and central Italy, with average PM10 larger in the warm season (spring and summer) with respect to the cold season as a consequence of the increase of crustal matter contribution likely due to the intrusion of African dust. These intrusions are more frequent in the warm season and have an influence on daily PM10 concentrations variable between 6% and 120% in this site. Correlation with meteorological data indicates that the more intense cases of intrusions of African dust happen with wind blowing from the SW direction. Average PM10 concentration decreases of about 23% during precipitation. The decrease ismainly due to the decrease in crustal matter contribution and secondary inorganic aerosol. The sum of the other three sources is almost not changing during precipitation