Iron Speciation of Natural and Anthropogenic Dust by Spectroscopic and Chemical Methods

In this work, we have characterized the iron local structure in samples of two different types of atmospheric dust using X-ray absorption spectroscopy and selective leaching experiments. Specifically, we have investigated samples of long-range transported Saharan dust and freshly emitted steel plant fumes with the aim of individuating possible fingerprints of iron in the two cases. Findings include (1) prevalence of octahedral coordinated Fe 3 + for all samples; (2) presence of 6-fold coordinated Fe 3 + , aluminosilicates and iron oxy(hydr)oxides in Saharan dust and (3) of Fe-bearing spinel-like structures in the industrial fumes; (4) general predominance of the residual insoluble fraction with a notable difference: 69% for Saharan dust and 93% for steel production emissions, associated with aluminosilicates and non-reducible iron oxy(hydr)oxides, and Fe spinels, respectively. The remarkable differences between the X-ray absorption spectroscopy (XAS) spectra and leaching test results for the two sample types suggest the possibility to exploit the present approach in more complex cases. To this aim, two additional case studies of mixed aerosol samples are presented and discussed

Mineralogical and Chemical Records of Icelandic Dust Sources Upon Ny-Ålesund (Svalbard Islands)

This work aims to identify the geochemical and mineralogical markers of Icelandic dust and to differentiate it from the dust of local origin deposited at the Ny-Ålesund station. We characterized representative sediment samples from Iceland and Svalbard and compared them to a set of aerosol samples collected in Ny-Ålesund to check the existence and type of the mineralogical markers. The sediment samples were analyzed by X-ray diffraction (XRD) to detect the mineralogical constrain of the geochemical markers. Both aerosol and sediment samples were examined by scanning electron microscopy coupled with EDS microanalysis (SEM-EDS) and image analysis to detect and to provide a morpho-chemical characterization of the mineralogical markers of dust provenance. Comparison between local and Icelandic sediments reveals the metal oxide particles as the most representative and distinguishing mineralogical/phase markers for Iceland dust sources. In particular, we have considered the magnetite-chromite and the magnetite-ülvospinel associations as marker facies of the tholeiitic magmatic series and the presence of volcanic glass as a further indicator of provenance from Iceland. The morphochemical characteristics of the metal oxide particles in the aerosol samples compared to those of the sediment samples have proved to be a powerful tool to separate Icelandic dust from other sources for dust. In particular, the small size, higher grain boundary complexity and lower Fe/Cr ratios suggest the influence of anthropogenic sources, well in accordance with the results of air mass backward trajectories which reveal a main contribution from industrialized areas in Eurasia. This study shows the reliability of the geochemical characterization of the metal oxide particles for the identification of the source regions of dust. In addition it provides an evidence that Icelandic dust can be transported long range to Svalbard confirming the importance of High Latitude Dust sources. © 2018 Moroni, Arnalds, Dagsson-Waldhauserová, Crocchianti, Vivani and Cappelletti.OA and PD-W was funded by the Icelandic Research Fund (Rannis) Grant No. 152248-051 and supported by Vinir Vatnajokuls. DC, BM, and SC was funded by the project SIDDARTA (CUP project id: I52F17001230001).Peer Reviewe

Monitoring Urban Particulate Matter On A Mobile Platform: Statistical Tools For High Frequency And Large Data Analysis.

Descriptive statistical tools for high frequency observations of particulate matters in the PMetro experiment

Iron Speciation of Natural and Anthropogenic Dust by Spectroscopic and Chemical Methods

In this work, we have characterized the iron local structure in samples of two different types of atmospheric dust using X-ray absorption spectroscopy and selective leaching experiments. Specifically, we have investigated samples of long-range transported Saharan dust and freshly emitted steel plant fumes with the aim of individuating possible fingerprints of iron in the two cases. Findings include (1) prevalence of octahedral coordinated Fe 3 + for all samples; (2) presence of 6-fold coordinated Fe 3 + , aluminosilicates and iron oxy(hydr)oxides in Saharan dust and (3) of Fe-bearing spinel-like structures in the industrial fumes; (4) general predominance of the residual insoluble fraction with a notable difference: 69% for Saharan dust and 93% for steel production emissions, associated with aluminosilicates and non-reducible iron oxy(hydr)oxides, and Fe spinels, respectively. The remarkable differences between the X-ray absorption spectroscopy (XAS) spectra and leaching test results for the two sample types suggest the possibility to exploit the present approach in more complex cases. To this aim, two additional case studies of mixed aerosol samples are presented and discussed

Analysis of multi-year near-surface ozone observations at the WMO/GAW \u201cConcordia\u201d station, Antarctica

In this work, eight years (2006\u20132013) of continuous measurements of near-surface ozone (O3) at the WMO/GAW contributing station \u201cConcordia\u201d (DMC, 75\ub006\u2019S, 123\ub020\u2019E, 3280 m a.s.l.) are presented, and the role of specific atmospheric processes in affecting O3 variability is investigated. In particular, during the period of highest data coverage (i.e., 2008\u20132013), O3 enhancement events (OEEs) were systematically observed at DMC, affecting 11.6% of the dataset. As deduced by a statistical selection methodology, the OEEs are affected by a significant interannual variability, both in the average and in the frequency of O3 values. To explain part of this variability, OEEs were analyzed as a function of: (i) total column of O3 and UV-A irradiance variability, (ii) long-range transport of air masses over the Antarctic plateau (by using LAGRANTO), and (iii) occurrence of \u201cdeep\u201d stratospheric intrusion events (by using STEFLUX). The overall O3 concentrations are controlled by a day-to-day variability, which indicates the dominating influence of processes occurring at \u201csynoptic\u201d scales rather than \u201clocal\u201d processes. Despite previous studies indicated an inverse relationship between OEEs and TCO, we found that the annual frequency of OEEs was higher when TCO values at DMC were higher than usual. The annual occurrence of OEEs at DMC was also related to the total time spent by air masses over the Antarctic plateau before their arrival at DMC, suggesting that the accumulation of photochemically-produced O3 during the transport dominated the local O3 production. Lastly, the influence of \u201cdeep\u201d stratospheric intrusion events at DMC was analyzed, and it was observed that this contribution played only a marginal role (the highest frequency observed was 3% of the period, in November). This latter point, i.e., the frequency and seasonality of stratosphere-to-troposphere (STE) events, and the relative influence of specific transport mechanisms, as well as snow chemistry, are still under debate. These topics will be investigated in the STEAR (Stratosphere-to-Troposphere Exchange in the Antarctic Region) project, starting in 2020 and funded by the Italian Antarctic Research Program (PNRA). In particular, STEAR will provide an assessment of STE events in Antarctica, by using both continuous observations (e.g., O3 and Beryllium-7) at DMC, and modeling outputs. In addition to DMC measurements, simultaneous atmospheric composition datasets will be analyzed at Antarctic coastal observatories, i.e., the Mario Zucchelli (MZS) and Jang Bogo (JBS) stations

Iron speciation in different Saharan dust advections and effect of the procedural blank on the results from X-ray Absorption Spectroscopy and selective leaching experiments

In this work, we applied X-ray Absorption Spectroscopy (XAS) and selective leaching experiments for investigating iron speciation in different dust advections collected on different unwashed quartz fiber filters. XAS analysis evidenced a predominance of Fe(III) in 6-fold coordination for Saharan dust and a trend towards Fe(II) and 4-fold coordination in the order: Saharan dust, mixed Saharan, and non-Saharan aerosol samples. The role of the sampling substrate was evaluated explicitly, including in the analysis a set of blank filters. We were able to pinpoint the possible contribution to the overall XAS spectrum of the residual Fe on quartz as the concentration decrease towards the blank value. In particular, the filter substrate showed a negligible effect on the structural trend mentioned above. Furthermore, selective leaching experiments evidenced a predominance of the residual fraction on Fe speciation and indicated the lowest Fe concentrations for which the blank contribution is <20% are 1 mg for the first three steps of the procedure (releasing the acid-labile, reducible and oxidizable phases, respectively) and 10 mg for the last step (dissolving the insoluble residuals)

Characteristics and Extent of Particulate Matter Emissions of a Ropeway Public Mobility System in the City Center of Perugia (Central Italy)

Minimetrò (MM) is a ropeway public mobility system that has been in operation in the city of Perugia for about ten years to integrate with urban mobility and lighten vehicular traffic in the historic city center. The purpose of this work was to evaluate the impact of MM as a source of pollutants in the urban context, and the exposure of people in the cabins and the platforms along the MM line. These topics have been investigated by means of intensive measurement and sampling campaigns performed in February and June 2015 on three specific sites of the MM line representative of different sources and levels of urban pollution. Stationary and dynamic measurements of particle size distribution, nanoparticle and black carbon aerosol number and mass concentrations measurements were performed by means of different bench and portable instruments. Aerosol sampling was carried out using low volume and high-volume aerosol samplers, and the samples nalysed by off-line methods. Results show that MM is a considerable source of atmospheric particulate matter having characteristics very similar to those of the common urban road dust in Perugia. In the lack of clear indications on road dust effect, the contribution of MM to the aerosol in Perugia cannot be neglected

Deposition processes over complex topographies: experimental data meets atmospheric modelling

The present paper describes the assessment of the atmospheric deposition processes in a basin valley through a multidisciplinary approach based on the data collected within an extensive chemical-physical characterization of the soils, combined with the local meteorology. Surface soil cores were collected on a NNW-SSE transect across the Terni basin (Central Italy), between the Monti Martani and the Monti Sabini chains (956 m a.s.l.), featuring the heavily polluted urban and industrial enclave of Terni on its bottom. Airborne radiotracers, namely 210Pb and 137Cs, have been used to highlight atmospheric deposition. We observed an increased deposition flux of 210Pb and 137Cs at sites located at the highest altitudes, and the associated concentration profiles in soil allowed to evaluate the role of atmospheric deposition. We also obtained a comprehensive dataset of stable anthropogenic pollutants of atmospheric origin that showed heterogeneity along the transect. The behavior has been explained by the local characteristic of the soil, by seeder-feeder processes promoted by the atmospheric circulation, and was reconciled with the concentration profile of radiotracers by factor analysis. Finally, the substantial impact of the local industrial activities on soil profiles and the role of the planetary boundary layer has been discussed and supported by simulations employing a Lagrangian dispersion model