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Abstract: X-ray Absorption Spectroscopy (XAS), X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis (TGA) and Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM–EDS) techniques were used to determine the composition and the speciation of Fe and Mn in road dust samples collected in the Traforo del San Bernardo highway tunnel. Principal Component Analysis and Least Square Fitting on the XANES region of the absorption spectra and structural refinements on the EXAFS part of the spectra were applied to obtain complementary information on the speciation, average oxidation state, and local structure of Fe and Mn. XRD indicated the presence of silica, calcite, gypsum, and of various phyllosilicates. TGA analysis confirmed the presence of phyllosilicates and also detected a significant amount of organic phases. These findings indicate the co-presence of particles of natural origin along with the organic phases related to vehicular gas exhausts emission. On the other hand, XAS analysis showed that iron is mainly present in the Fe3O4 and FeCl3 forms, which can be considered to have both anthropic origin, i.e., exhaust emission and salt used to prevent ice formation, respectively. [Copyright &y& Elsevier]

• A complex mineralogical assemblage was revealed. • Fe(II) and Fe(III) species were detected in a variety of coordination environments. • The Fe oxidation state and speciation is not affected by water. • Significant changes were evidenced as a function of particle granulometry. • Ashes surface features may prevent direct exposure to mobile and toxic Fe(II). Volcanic ashes particles are subjected to substantial modification during explosive eruptions. The mineralogical and compositional changes have important consequences on the environment and human health. Nevertheless, the relationship between the speciation of iron (Fe) and the mineralogical composition and particle granulometry of the ashes, along with their interaction with water, are largely unknown. In particular, the Fe oxidation state and the possible formation of new Fe-bearing phases in presence of S, Cl, and F in the plume are key points to assess the impact of the ashes. Fragmental material ejected during volcanic activity (tephra) in 2013, was collected on the Mt. Etna (Italy) and investigated using a multi-technique approach that included conventional Electron Paramagnetic Resonance (EPR), high field EPR (HFEPR), EchoEPR, and Fe K-edge X-ray Absorption Spectroscopy (XAS). These element-selective techniques allowed obtaining a detailed information on the oxidation state and coordination environment of Fe, and of its speciation in the ash samples as a function of the granulometry. A complex mineralogical assemblage, consisting of variable amounts of nanometric crystalline Fe inclusions in a glass matrix, and of Fe-oxides and Fe-sulfur phases was revealed. A risk assessment of the ashes is attempted. [ABSTRACT FROM AUTHOR]

The appropriate selection of representative pure compounds to be used as reference is a crucial step for successful analysis of X-ray absorption near edge spectroscopy (XANES) data, and it is often not a trivial task. This is particularly true when complex environmental matrices are investigated, being their elemental speciation a priori unknown. In this paper, an investigation on the speciation of Cu, Zn, and Sb based on the use of conventional (stoichiometric compounds) and non-conventional (environmental samples or relevant certified materials) references is explored. This method can be useful in when the effectiveness of XANES analysis is limited because of the difficulty in obtaining a set of references sufficiently representative of the investigated samples. Road dust samples collected along the bridge connecting Venice to the mainland were used to show the potentialities and the limits of this approach. [ABSTRACT FROM AUTHOR]