A PM10 chemically characterised nation-wide dataset for Italy. Geographical influence on urban air pollution and source apportionment

: Urban textures of the Italian cities are peculiarly shaped by the local geography generating similarities among cities placed in different regions but comparable topographical districts. This suggested the following scientific question: can such different topographies generate significant differences on the PM10 chemical composition at Italian urban sites that share similar geography despite being in different regions? To investigate whether such communalities can be found and are applicable at Country-scale, we propose here a novel methodological approach. A dataset comprising season-averages of PM10 mass concentration and chemical composition data was built, covering the decade 2005-2016 and referring to urban sites only (21 cities). Statistical analyses, estimation of missing data, identification of latent clusters and source apportionment modelling by Positive Matrix Factorization (PMF) were performed on this unique dataset. The first original result is the demonstration that a dataset with atypical time resolution can be successfully exploited as an input matrix for PMF obtaining Country-scale representative chemical profiles, whose physical consistency has been assessed by different tests of modelling performance. Secondly, this dataset can be considered a reference repository of season averages of chemical species over the Italian territory and the chemical profiles obtained by PMF for urban Italian agglomerations could contribute to emission repositories. These findings indicate that our approach is powerful, and it could be further employed with datasets typically available in the air pollution monitoring networks

Results of the first European Source Apportionment intercomparison for Receptor and Chemical Transport Models

In this study, the performance of the source apportionment model applications were evaluated by comparing the model results provided by 44 participants adopting a methodology based on performance indicators: z-scores and RMSEu, with pre-established acceptability criteria. Involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), provided a unique opportunity to cross-validate them. In addition, comparing the modelled source chemical profiles, with those measured directly at the source contributed to corroborate the chemical profile of the tested model results. The most used RM was EPA- PMF5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) and more difficulties are observed with SCE time series (72% of RMSEu accepted). Industry resulted the most problematic source for RMs due to the high variability among participants. Also the results obtained with CTMs were quite comparable to their ensemble reference using all models for the overall average (>92% of successful z-scores) while the comparability of the time series is more problematic (between 58% and 77% of the candidates’ RMSEu are accepted). In the CTM models a gap was observed between the sum of source contributions and the gravimetric PM10 mass likely due to PM underestimation in the base case. Interestingly, when only the tagged species CTM results were used in the reference, the differences between the two CTM approaches (brute force and tagged species) were evident. In this case the percentage of candidates passing the z-score and RMSEu tests were only 50% and 86%, respectively. CTMs showed good comparability with RMs for the overall dataset (83% of the z-scores accepted), more differences were observed when dealing with the time series of the single source categories. In this case the share of successful RMSEu was in the range 25% - 34%.JRC.C.5-Air and Climat

Determination of metals, metalloids and non-volatile ions in airborne particulate matter by a new two-step sequential leaching procedure Part A: Experimental design and optimisation

The optimisation of a micro-analytical two-step sequential leaching procedure for the determination of non-volatile ions (NO3-, SO42-, Cl-, Na+, Mg2+, NH4+ and Ca2+) and of 17 elements (Al, As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, S, Se, V, Zn, Sb, Si and Ti) in two fractions-extract and residue-on the same sample of air particulate matter is described. The two-step method was tested on the SRM NIST 1648 for equivalence with two reference methods, the EMEP procedure for ions extraction and the EN 12341 standard for the elemental determination of the PM10 and is suitable for application to small sample amounts (less than 1 mg of particulate matter is needed), i.e. those collected by daily low volume filter-sampling. Performance times of the procedure were optimised to meet the target of routine application for large scale monitoring samples. A single ultrasonic-assisted extraction of air particulate matter is performed in 0.01 M acetate buffer at pH 4.5, followed by IC ions analysis and ICP-OES elemental analysis of the extract and by ICP-OES elemental analysis of the mineralized residue after dissolution by microwave-assisted digestion with a HNO3/H2O2 mixture. Using a pH buffered extracting solvent was preferred to water or diluted acid solutions to improve the reproducibility of metals extraction with respect to existing leaching methods; the influence of pH, nature and concentration of the buffer solution and extraction time on analytes concentration in the extract is discussed. Values of ions extraction and elements recoveries resulted fairly equivalent with those obtained by the reference methods. The study was also extended to some non-certified elements (Mg, S. Sb, Si and Ti) for their environmental significance. Elements recoveries were obtained as sum of the extract and residue fractions and were comparable with those obtained by direct dissolution. Standard deviations were within 10% for almost all detected ions and elements. (c) 2005 Elsevier B.V. All rights reserved

Determination of metals and non volatile ions in airbone particulate matter by a new two-step sequential leaching procedure. Part B: validation on equivalent real samples

Due to the lack of proper standard materials for airborne particulate matter collected on filters, a validation scheme was developed, which is here described, to the aim of testing the application of leaching procedures performing both ions and elemental determinations on real samples of airborne particulate matter collected on filters. The scheme has been developed on a two-step leaching method (extraction in acetate buffer and acid dissolution of residue) previously developed by authors and consists of two series of tests to be run on n pairs of equivalent parallel samples filter-collected. The first series of tests aims to assess on real samples the equivalence between results obtained by the tested procedure with those obtained by the EMEP ions extraction and the EN 12341 standard methods, whereas the second aims to evaluate the reproducibility of analytical results of elemental determination in the leached and dissolved fractions; in the latter case data reliability is also evaluated as a function of the environment-intrinsic variability of real samples. To avoid errors due to sampling differences data from filter pairs were standardized both by gravimetric determination of loaded filters, according to the EN 12341 standard and by the rate [SO42-](A)/[SO42-](B), where [SO42-] indicate the soluble sulphate concentration in the extract; in the latter case values improved for all elements and in both fractions. Results of equivalence with standard methods and reproducibility tests are evaluated as mean relative percentage differences (Delta%) and percentage elements recoveries (R%). The application of the validation scheme to the two-step leaching method is here discussed for non-volatile ions and for 17 elements detected on 22 pairs of low-volume collected PM10 samples on Teflon filters. (c) 2005 Elsevier B.V. All rights reserved

Source apportionment by multivariate analysis of fine and coarse airborne particulate matter in the Lazio region (Italy)

Assessment of source contributions to the atmospheric concentrations of airborne particulate matter (PM) affecting a defined area holds a key role, both in expanding knowledge of the influence of local/regional sources on the physical - chemical characteristics of collected particles and in providing scientific support to the effectiveness of measures to be taken by authorities towards air quality improvement. Source apportionment by statistical methods comprises the use of factor analysis (FA) and of multi-linear regression analysis (MLRA). The combined application of these methods to data of PM chemical composition helps, indeed, the identification of predominant particle source categories and the apportionment of their relative contributions to the collected PM. To this purpose, the analytical procedure to be used for the chemical characterization of PM samples has to provide the most possible complete information on particles composition, so that concentration data of both major and trace PM components can be included in the FA-MLRA analysis. Within the “Polveri Fini” (Fine Dust) project, aimed to investigate the contributions to PM in the Lazio region (Italy) from local sources and medium-long range transport, 24-h PM10 and PM2.5 samples were daily collected on quartz and Teflon filters over 1 year (Oct. 2004-July 2005). PM samples were characterized for chemical composition by a proper analytical scheme. By this scheme PM samples collected on quartz are analysed for the elemental and organic carbon content (EC/OC) by a thermal-optical analyser; PM samples collected on Teflon are first analysed by ED-XRF for major elements and then chemically leached into an extract and a mineralised residual fractions by a two-step leaching procedure, previously developed and validated by our lab. In the extract solution ions and soluble elements are determined by IC and ICP-AES, and the residual elements solution is also analysed by ICP-AES. A set of about 1000 PM10 and PM2.5 samples and 25 chemical components was investigated by FA-MLRA. Results about the chemical characterisation of the collected samples are discussed together with the main important sources affecting atmospheric particles in the Lazio region; these have been identified as crustal components, sea-salt, anthropogenic combustion, secondary compounds. For each main source category, the back-trajectories of the air masses have been determined and statistically evaluated

Two-stage chemical fractionation method for the analysis of elements and non-volatile inorganic ions in PM10 samples: Application to ambient samples collected in Rome (Italy)

A two-stage micro-analytical scheme for the determination of metals and ions in atmospheric particulate matter collected on only one Teflon filter was developed. In the first stage the collected particles are chemically fractionated for their solubility in a pH-buffered extracting solution; in the second stage the residue is mineralised. The major non-volatile inorganic ions (Cl, NO3 , SO4 2, Na+, NH4 +, Ca2+, Mg2+) are determined in the first fraction by ion-chromatography (IC), while metals and metalloids (Al, As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, S, Sb, Se, Si, Ti, V, Zn) are determined in both the acetate extractable and the mineralised residual fractions by inductively coupled plasma optical emission spectroscopy (ICP-OES). The procedure was applied to ambient 24-h PM10 samples collected on Teflon filters during two field campaigns carried out at two sites in the area of Rome (Italy). The variations in the chemical composition of the collected particles during the two periods were interpreted in the light of the dilution properties of the lower atmosphere and of the back-trajectories of the air masses. The difference in the results between the two locations was interpreted in the light of their proximity to the emission sources. It was found that the acetate extractable and the mineralised residual fraction of some metals exhibit a different temporal pattern, suggesting the existence of different emission sources of the two fractions

Enhancement of source traceability of atmospheric PM by elemental chemical fractionation

During a 1-year study (‘‘Fine dust’’ Project) funded by the Lazio regional government (Italy), about 1000 daily PM10 and PM2.5 samples collected from six sites in the region were subjected to chemical fractionation based on differences in elemental solubility. In this way, it was possible to achieve meaningful characterization of the elemental composition of individual samples. For most of the investigated elements, we found significant differences between the extracted and the mineralized residual fraction. In general, fine particulate was best characterized by the composition of the extracted fraction, while coarse particles from traffic-related sources were best characterized using residues. For several metals (Cd, Pb, Sn, Sb and V) having a critical environmental impact, this result was particularly clear. The application of Principal Component Analysis (PCA) and receptor modelling (PCR) to the data set allowed us to evidence the enhancement of selectivity towards different emission sources that is obtained when chemical fractionated data are considered instead of total element content. Chemical fractionation seems to generate very selective markers for specific emission sources and in particular for re-suspended road dusts, one of the main factors responsible for the increase of elemental concentrations in urban areas

Carrier-mediated transport of aminoacids through bulk liquid membranes

Abstract: A novel carrier, the N-methyl, N-dodecyl-ephedrinium ion, was studied for the selective transport of some aromatic amino acids [phenylalanine (Phe), histidine (His) and tryptophan (Trp)] through bulk liquid membranes. Investigations of the main parameters limiting the aided transport of the amino acids were carried out. Transport rates that resulted were affected by the amino acid lipophilicity, the pH variations of feed and receiving solutions, the concentration, and the nature of countertransport ions. Further results indicate that the carrier can interact with amino acids by ion pairing and nonionic interactions. Membrane selectivity showed to be strictly related to kinetics of the amino acid release at the membrane/receiving interface, and its results were satisfactory when the receiving solution was kept in acidic conditions. In these conditions, when a mixture of the three amino acids was used as the feed solution, the transport rate of phenylalanine was over three times higher with respect to tryptophan, while the transport of histidine was almost completely damped down