The chemical and phase compositions of particles produced by laser ablation (266 nm Nd:YAG) of silicate NIST glasses and zircon were studied by SIMS and HR-TEM techniques. The data suggest that the formation of phases of different mineralogy and/or chemical composition from the original sample at the ablation site can result in elemental fractionation (non-stoichiometric sampling) in material delivered to the ICP-MS for quantitative analysis. Evidence of the element fractionation is preserved in chemically zoned ejecta deposited around the ablation pit. The chemical composition and mineralogy of particles varies with particle size so that the efficiency of transport of particles also plays a role in elemental fractionation. During the first 250 pulses in a typical ablation experiment using a 266 nm laser, particle sizes are mainly <2.5 μm; thereafter they decrease to <0.3 μm. Pb and U are fractionated significantly during the ablation of both silicate glass and zircon. During the ablation of glass, both micron-sized, melt-derived, spherical particles, and nm-sized, condensate-derived particle clusters, are produced; the very smallest particles (<0.04 μm) have anomalously high Pb/U ratios. For zircon, both larger (0.2–0.5 μm) spherical particles and agglomerates of smaller (∼0.005 μm) particles produced by ablation are mixtures of amorphous and crystalline materials, probably zircon, baddeleyite (ZrO₂) and SiO₂. Evidence for thermal decomposition of zircon to baddeleyite and SiO₂ is preserved in the wall of the ablation pit, and may lead to the commonly observed increase in Pb/U recorded during laser ablation ICP-MS analysis. It follows that a matrix-matched external calibration is essential for achieving highly precise and accurate laser (266 nm wavelength) ablation ICP-MS analysis of Pb and U in silicate samples.

Among the nitrated and oxygenated PAHs (NPAHs, OPAHs) are some of the most hazardous substances to the public health, mainly due to their carcinogenicity and oxidative potential. Despite these concerns the concentrations and fate of NPAHs and OPAHs in the atmospheric environment are largely unknown. Ambient air concentrations of 18 NPAHs, 5 quinones and 5 other OPAHs were determined at two urban and one regional background site in central Europe. At one of the urban sites, the total (gas and particulate) concentrations of Σ10OPAHs were 10.0±9.2 ng/m3 in winter and 3.5±1.6 ng/m3 in summer. The gradient to the regional background site exceeded one order of magnitude. Σ18NPAH concentrations were typically one order of magnitude lower than OPAHs. Among OPAHs, 9-fluorenone and (9,10)-anthraquinone were the most abundant species, accompanied by benzanthrone in winter. (9,10)-anthraquinone represented two thirds of quinones. We found that a large fraction of the target substance particulate mass was carried by submicrometer particles. The derived inhalation bioaccessibility in the PM10 size fraction is found ≈5% of the total ambient concentration of OPAHs and up to ≈2% for NPAHs. For 9-fluorenone and (9,10)-anthraquinone, up to 86 and 18%, respectively, were found at the rural site. Our results indicate that water solubility could function as a limiting factor for bioaccessibility of inhaled particulate NPAHs and OPAHs, without considerable effect of surfactant lipids and proteins in the lung lining fluid

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.JRC.H.2-Air and Climat