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Wintertime air pollution affects air quality of Arctic and sub-Arctic urban areas, because of the coupling between strong local emissions for residential heating and energy production and poor atmospheric dispersion associated with a stratified planetary boundary layer. Aerosols represent priority pollutants in such environments, and their behaviour in the Arctic wintertime boundary layer not only impacts air quality but also determines deposition on snow or ice surfaces, leading to chemical and physical modifications in the snowpack. The interactions between boundary layer meteorology and air pollution were the focus of the international ALPACA (Alaskan Layered Pollution and Chemical Analysis) field campaign held in January and February 2022 in Fairbanks (AK, USA). The aim of the present work is to analyse the fluxes of atmospheric particles in at a urban background site in Fairbanks, based on continuous observations of aerosol concentration, size distributions, and size-segregated deposition velocities. The EC system was installed at the suburban site of UAF (University of Alaska Farm), located nearby the foothills bordering the city basin. The main micrometeorological parameters and fluxes (wind field, friction velocity, turbulent kinetic energy, and sensible heat flux) were characterized in terms of boundary layer conditions (occurrence of thermal inversions, dynamic stratifications, vertical wind shear, slope currents, coherent turbulence structures). The aerosol eddy covariance system was based on a condensation particle counter (CPC) - able to measure particles down to 5 nm in diameter - and an Optical Particle Counter Optical Particle Counter (OPC) for evaluating particle fluxes in the accumulation mode (0.25 < dp < 0.8 μm) and quasi-coarse mode (0.8 < dp < 3 μm). The median number concentration was 13 E+3 cm−3, 76 cm−3 and 0.3 cm−3 for ultrafine, accumulation and quasi-coarse particles mode, with higher concentrations found at low wind speeds. The particle fluxes showed a net emission pattern for the ultrafine, accumulation and quasi-coarse dimensional mode, especially in daytime, with average values of 203, 0.3, and 0.02 cm-2 s-1 respectively. Deposition periods were observed most frequently for air masses from the city located to the east, while local emission sources due to traffic lead emission fluxes, especially in the accumulation mode. We discuss the particle flux measurements in the context of parallel aerosol and gaseous pollutants determined by fixed and mobile platforms (a tethered balloon and a car) as well as of determinations of depositions in the snow pack across the Fairbanks area.

The Alaskan Layered Pollution and Chemical Analysis (ALPACA) field campaign investigated the sources and processing of wintertime urban pollution in Fairbanks, Alaska in January and February 2022. Several sites located around the city of Fairbanks collected data to study the underexplored cold and dark wintertime dynamical, physical and chemical processes driving air pollution, both outdoors and indoors. We deployed a tethered balloon system at a farm field site near the University of Alaska (UAF) to specifically investigate the vertical layering of pollution and influence of different emission altitudes on surface pollution levels.The study site is located in a suburban area, west of downtown Fairbanks. Observational efforts there focused mainly on surface exchanges and the vertical distribution of pollutants in relation to the boundary layer structure, specifically under stable (inversion) conditions. Instruments at the UAF-farm provided continuous ground measurements of aerosol physical, optical and chemical properties, trace gases (O3, CO, N2O) and meteorology. The newly designed Modular Multiplatform Air Compatible Measurement System (MoMuCAMS) was deployed with a tethered-balloon (helikite) to sample air up to 350 m above ground level, providing information on the vertical distribution and mixing processes of atmospheric pollutants. Instruments onboard MoMuCAMS provided information on aerosol characteristics (particle number concentration, size distribution, absorption coefficient and chemical composition), trace gases (CO2, O3, CO, N2O, NOx), and meteorology. MoMuCAMS performed 21 flights between January 26 and February 25, 2021, collecting roughly 140 individual profiles of varying altitude under different boundary layer conditions, intercepting pollution plumes at different heights and of different composition. Given the suburban location of the study site, we measured the influence of polluted air from the city and “cleaner” air from more remote origins.We will show how the vertical structure of the atmosphere and the frequently occurring temperature inversions affect transport and dispersion of pollution at different heights and how different meteorological conditions affect local air circulation and pollution at the study site.

The ALPACA (Alaskan Layered Pollution and Chemical Analysis) field campaign (January-February 2022) aimed to collect new data to document Arctic wintertime air pollution. State of the art instrumentation was deployed in Fairbanks, Alaska to characterise inorganic/organic aerosols, vertical layering and mixing of aerosols and precursors, and meteorology at sites influenced by local anthropogenic emissions and background Arctic Haze.Vertical profiles of the boundary layer composition were collected from an instrumented tethered ballon (helikite) deployed at the UAF-Farm site in West Fairbanks. The Helikite payload included instruments dedicated to the characterisation of particles (concentration, composition, size distribution) and to measurement of trace gases with dedicated analysers for O3, CO and CO2 and a MICROMEGAS instrument. MICROMEGAS is a light-weight package based on low-cost Alphasense electrochemical sensors for trace gases (CO/O3/NO/NO2). This instrument was also deployed on the ground close to reference-grade trace gas analysers at the CTC measurement site in downtown Fairbanks, and onboard a vehicle for 2D-mapping of pollution within and around Fairbanks.Low-cost electrochemical sensors are sensitive to temperature and humidity and require careful calibration and validation. We first introduce the calibration method based on multi-linear regression with the collocated CTC reference measurements. The performance (biases, correlation coefficients, RMSDs) of the calibrated data are then evaluated against CTC observations not used for the calibration. Cases of vertical helikite profiles with polluted layers related to specific dynamical conditions (temperature inversions, wind regimes…) are investigated. Tracer-tracer relationships (CO, NO, NO2 versus CO2 ; NOx versus Ox) together with meteorological observations are used to examine air mass origins (domestic combustion, vehicles, power plants), as well as dilution and chemical transformation of the sampled pollution plumes.

A seven-week field campaign took place in Fairbanks, Interior of Alaska, during January and February 2022, in the framework of the Alaskan Layered Pollution And Chemical Analysis (ALPACA) international project. A compact Doppler Lidar was deployed (Leosphere WindCube v2) to profile winds in the atmospheric boundary layer from 40 to 290 m above ground level (a.g.l.). The first objective of this project was to study the influence of strong atmospheric stratification and temperature inversion layering on air pollution. For this purpose, the Lidar was first installed in the urban canopy downtown Fairbanks city (~3.5 weeks). The second objective was to study the influence of shallow cold flows (SCF) on surface-based temperature inversions and the energy budget. Therefore, the Lidar was then re-deployed in a suburban site located nearby the foothills bordering the city, at the outlet of a small valley. Measurements on this site also included surface turbulence by eddy-covariance, radiative fluxes and temperature profiles, both in-situ during tethered balloon launches and remote sensing using a Microwave Radiometer.The conditions for operating a near-infrared Doppler Lidar were very stringent, as Arctic environments are generally pristine, except for urban areas in wintertime. However, the wind dataset availability up to 100 m a.g.l. was ~47% at the urban site and ~30% at the suburban site. The relationship between Lidar performance and aerosol size distribution is under evaluation at both sites, using observations from Scanning Mobility Particle Sizers. At the suburban site, the SCF descending from the nearby valley was regularly visible, with wind speeds reaching 5-6 m.s-1 at 40 m a.g.l. Cases of continuous flow lasting for more than 24 hours were observed, during which the SCF depth remained stable and very shallow (40 to 60 m a.gl.). Pulsated episodes also occurred, that could be as short as 2 hours, and were characterized by a more variable SCF depth (up to 100 m a.g.l.). The local and regional conditions triggering the onset, variability and characteristics of the SCF are under investigation. Another unexpected observation was made: at both sites, snow precipitations were always found to be associated with ascending winds (up to 1.2 m.s-1). To improve our understanding of the dynamical processes highlighted by the Lidar wind observations, the Polar-WRF (Weather Research and Forecasting) model will be run at a very high resolution (~1 km). The focus will be to investigate, and potentially improve, the ability of the Polar-WRF surface layer and land-surface model (via the roughness length for momentum and the stability functions) to reproduce the surface energy budget, the very and weakly stable regimes and the transition between the two at the SCF onset in a continental, high-latitude context.

Optical properties of surface aerosols at Dome C, Antarctica, in 2007–2013 and their potential source areas are presented. Scattering coefficients (σsp) were calculated from measured particle number size distributions with a Mie code and from filter samples using mass scattering efficiencies. Absorption coefficients (σap) were determined with a three-wavelength Particle Soot Absorption Photometer (PSAP) and corrected for scattering by using two different algorithms. The scattering coefficients were also compared with σsp measured with a nephelometer at the South Pole Station (SPO). The minimum σap was observed in the austral autumn and the maximum in the austral spring, similar to other Antarctic sites. The darkest aerosol, i.e., the lowest single-scattering albedo ωo≈0.91, was observed in September and October and the highest ωo≈0.99 in February and March. The uncertainty of the absorption Ångström exponent αap is high. The lowest αap monthly medians were observed in March and the highest in August–October. The equivalent black carbon (eBC) mass concentrations were compared with eBC measured at three other Antarctic sites: the SPO and two coastal sites, Neumayer and Syowa. The maximum monthly median eBC concentrations are almost the same (∼3±1 ng m−3) at all these sites in October–November. This suggests that there is no significant difference in eBC concentrations between the coastal and plateau sites. The seasonal cycle of the eBC mass fraction exhibits a minimum f(eBC) ≈0.1 % in February–March and a maximum ∼4 %–5 % in August–October. Source areas were calculated using 50 d FLEXPART footprints. The highest eBC concentrations and the lowest ωo were associated with air masses coming from South America, Australia and Africa. Vertical simulations that take BC particle removal processes into account show that there would be essentially no BC particles arriving at Dome C from north of latitude 10∘ S at altitudes m. The main biomass-burning regions Africa, Australia and Brazil are more to the south, and their smoke plumes have been observed at higher altitudes than that, so they can get transported to Antarctica. The seasonal cycle of BC emissions from wildfires and agricultural burning and other fires in South America, Africa and Australia was calculated from data downloaded from the Global Fire Emissions Database (GFED). The maximum total emissions were in August–September, but the peak of monthly average eBC concentrations is observed 2–3 months later in November, not only at Dome C, but also at the SPO and the coastal stations. The air-mass residence-time-weighted BC emissions from South America are approximately an order of magnitude larger than from Africa and Oceania, suggesting that South American BC emissions are the largest contributors to eBC at Dome C. At Dome C the maximum and minimum scattering coefficients were observed in austral summer and winter, respectively. At the SPO σsp was similar to that observed at Dome C in the austral summer, but there was a large difference in winter, suggesting that in winter the SPO is more influenced by sea-spray emissions than Dome C. The seasonal cycles of σsp at Dome C and at the SPO were compared with the seasonal cycles of secondary and primary marine aerosol emissions. The σsp measured at the SPO correlated much better with the sea-spray aerosol emission fluxes in the Southern Ocean than σsp at Dome C. The seasonal cycles of biogenic secondary aerosols were estimated from monthly average phytoplankton biomass concentrations obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite sensor data. The analysis suggests that a large fraction of the biogenic scattering aerosol observed at Dome C has been formed in the polar zone, but it may take a month for the aerosol to be formed, be grown and get transported from the sea level to Dome C.

Optical properties of surface aerosols at Dome C, Antarctica in 2007–2013 and their potential source areas are presented. Scattering coefficients (σsp) were calculated from measured particle number size distributions with a Mie code and from filter samples using mass scattering efficiencies. Absorption coefficients (σap) were determined with a 3-wavelength Particle Soot Absorption Photometer (PSAP) and corrected for scattering by using two different algorithms. The scattering coefficients were also compared with σsp measured with a nephelometer at the South Pole Station (SPO). The minimum σap was observed in the austral autumn and the maximum in the austral spring, similar to other Antarctic sites. The darkest aerosol, i.e., the lowest single scattering albedo ωo ≈ 0.91 was observed in September and October and the highest ωo ≈ 0.99 in February and March. The uncertainty of the absorption Ångström exponent αap is high. The lowest αap monthly medians were observed in March and the highest in August–October. The equivalent black carbon (eBC) mass concentrations were compared with eBC measured at three other Antarctic sites: the SPO and two coastal sites, Neumayer and Syowa. The maximum monthly median eBC concentrations are almost the same (≈ 3 ± 1 ng m−3) at all these sites in October–November. This suggests that there is no significant difference in eBC between the coastal and plateau sites. The seasonal cycle of the eBC mass fraction exhibits a minimum f(eBC) ≈ 0.1 % in February–March and a maximum ≈ 4–5 % in August–October. Source areas were calculated using 50-day FLEXPART footprints. The highest eBC concentrations and the lowest ωo were associated with air masses coming from South America, Australia and Africa. Vertical simulations that take BC particle removal processes into account show that there would be essentially no BC particles arriving at Dome C from north of latitude 10° S at altitudes sp was similar to that observed at Dome C in the austral summer but there was a large difference in winter, suggesting that in winter SPO is more influenced by sea spray emissions than Dome C. The seasonal cycles of σsp at Dome C and at the SPO were compared with the seasonal cycles of secondary and primary marine aerosol emissions. The σsp measured at SPO correlated much better with the sea-spray aerosol emission fluxes in the Southern Ocean than σsp at Dome C. The seasonal cycles of biogenic secondary aerosols were estimated from monthly average phytoplankton biomass concentrations obtained from the CALIOP satellite sensor data. The analysis suggests that a large fraction of the biogenic scattering aerosol observed at Dome C has been formed in the polar zone but it may take a month for the aerosol to be formed, grown and get transported from the sea level to Dome C.

We describe and implement a data selection algorithm aimed at identifying background atmospheric CO2 observations from in situ continuous measurements. Several selection criteria for detecting the background data have been developed and are currently used: the main objective of this work was to define a common methodology to extract the atmospheric background signal minimizing heterogeneities due to the use of different selection algorithms. The algorithm used in this study, (BaDS, Background Data Selection) was tested and optimized using data (from 2014 to 2018) from four Italian stations characterized by markedly different environmental conditions (i.e., mountain, coastal and marine): Plateau Rosa (PRS), Mt. Cimone (CMN), Capo Granitola (CGR) and Lampedusa (LMP). Their locations extend from the Alps to the central Mediterranean. The adopted algorithm proved to be effective in separating the local/regional from the background signal in the CO2 time series. About 6% of the data at LMP, 11% at PRS, 20–38% at CMN and 65% at CGR were identified as non-background. LMP and PRS can be used as reference sites for the central Mediterranean, while CMN and CGR were more impacted by regional sources and sinks. Finally, we discuss a possible application of BaDS screened data.

In this work, we present and analyze a dataset of near-surface NO and NO2 observations carried out at the Mt. Cimone WMO/GAW global station (CMN, Italy, 2165 m a.s.l.) from 2015 to 2019. The purpose of this work is to provide a first characterization of NO and NO2 variability over different time scales, as well as to obtain preliminary information about transport processes able to affect the observed variability. NO was characterized by a peak in February–March (mean value: 0.08 ppb), while in summer the typical levels were near or lower than the detection limit. NO2 values maximized in winter (0.32–0.37 ppb) and minimized in summer (0.21 ppb in June). The evident NO and NO2 diel cycles point towards a joint role of vertical transport of air masses from the regional planetary boundary layer (PBL) and photochemistry. We combined nighttime observations (less affected by direct transport from the regional PBL) and 3D back-trajectories, calculated by the FLEXTRA model (2015 -2018), to analyze how long-range atmospheric circulation could impact NO2 observations. Even if some caveats should be considered when commenting results from back-trajectory analysis (i.e. NOx removal by oxidation processes not represented, possible residual impact of regional PBL air masses, impact of adding/removing a single year from the analysis), some robust outcomes can be considered: the atmospheric transport from northern Africa and the Mediterranean basin was tagged to baseline NO2 values, while the highest values were related to atmospheric circulation overpassing central/western Europe (spring) and North Italy (spring and summer). Less robust relationship were found between high NO2 values and air masses passing over central/western Europe (winter) and eastern Europe (winter and summer). On the other side, mountain thermal wind regime represents an important process for the occurrence of high NO2 events by transporting polluted air masses from the regional PBL to CMN. Our analysis suggested that it is not possible to define a unique set of O3/NOx threshold values able to discriminate the photochemical ages of air masses as done in previous studies; these values must be tuned as a function of the season and, possibly, of the measurement site. Finally, we segregated CMN observations as a function of conditions representative for the presence of free tropospheric- or PBL-affected air masses: higher NOx were observed under conditions representative for the transport of air masses from the regional PBL; the differences between the two regimes are maximized in winter for NO and in summer-autumn for NO2.

The increasing exposure to air pollutants associated with the world-wide process of urbanization is among the most important risk factors for human health. In this context, the development of green infrastructures has gained interest for providing new win-win solutions for improving air quality and urban climate. In the present work, we have characterized an innovative, engineered green infrastructure, the CityTree (CT), in a real urban setting. Abatement rate of priority pollutants (PMx, NOx, black carbon) by a CT unit was determined, during three intensive field campaigns in the city of Modena (Italy). The measurements of the air filtered through the CT (active mode) showed significant reductions in particulate matter concentration: 19–23% for PM10 aerosol mass, 15–20% for PM2.5, 11–13% for PM1, 38% for ultrafine particle number concentration and 17% for black carbon concentration. The measurements in passive mode (with ventilation off) enabled the estimation of the deposition velocities of aerosol particles and gases onto the device surface. The average deposition velocities for PM10 and NOx observed for the CT mosses fall in the range reported in the scientific literature for other types of green surfaces (e.g., grass lawns, hedges). A comparison of the pollutant removal efficiency between passive and active CT mode was performed. The aerosol removal efficiency of the CT resulted from ~3 to almost 20 times higher in filtration than in deposition mode, according to the selected aerosol parameter. These results indicate that moss bio-filters can be more effective in removing air pollutants than standard green infrastructures for in situ applications.

Several studies investigated the possible impacts of the restriction measures related to the containment of the spread of the COrona VIrus Disease (COVID-19) to atmospheric ozone (O3) at global, regional, and local scales during 2020. O3 is a secondary pollutant with adverse effects on population health and ecosystems and with negative impacts on climate, acting as greenhouse gas. Most of these studies focused on spring 2020 (i.e. March–May) and on observations in the planetary boundary layer (PBL), mostly in the vicinity of urban agglomerates. Here, we analyzed the variability of O3 above the PBL of northern Italy in 2020 by using continuous observations carried out at a high mountain WMO/GAW global station in Italy (Mt. Cimone–CMN; 44°12' N, 10°42' E, 2165 m a.s.l.). Low O3 monthly anomalies were observed during spring (MAM) and summer (JJA), when periods of low O3 intertwined with periods with higher O3, within climatological ranges. A similar variability was observed for O3 precursors like NO2 and 15 anthropogenic non-methane volatile organic carbons, but the systematic O3 anomalies were not reflected in these variables. The analysis of meteorological variables and diel O3 cycles did not suggest major changes in the vertical transport related to the thermal circulation system in the mountain area. The analysis of five days back-trajectories suggested that the observed O3 anomalies cannot be explained by differences in the synoptic-scale circulation with respect to the previous years alone. On the other hand, the characterization of two transport patterns (i.e. air masses from the regional PBL or from the free troposphere) and the analysis of back-trajectories suggested an important contribution of transport from the continental PBL during the periods with the lowest O3 at CMN. When proxies of air mass transport from the regional PBL are considered, a lower NOx content was pointed out with respect to the previous years, suggesting a lower O3 production in a NOx-limited atmosphere. Our study suggested for the first time that, during MAM and JJA 2020, the reduced anthropogenic emissions related to the COVID-19 restrictions lowered the amount of this short-lived climate forcer/pollutant at remote locations above the PBL over northern Italy. This work suggests the importance of limiting anthropogenic precursor emissions for decreasing the O3 amount at remote locations and in upper atmospheric layers., Environmental Research Letters, 16 (7), ISSN:1748-9326, ISSN:1748-9318

The Mediterranean basin is considered a global hot-spot region for climate change and air-quality. CO2 is the single most-important anthropogenic greenhouse gas (GHG) in the atmosphere, accounting approximatively for ∼63% of the anthropogenic radiative forcing by long-lived GHG. According to Le Quérée et al. (2018), the increasing of the atmospheric CO2 mixing ratios in the global atmosphere is driven by fossil fuel and cement production.In order to reduce GHG emissions and taking into account the needs for economy and society development, schemes of regulation and emission trading have been adopted at international, national, and city levels. The implementation of these regulation, to achieve the goal successfully, needs scientific evidence and information provided on consistent datasets. In the last year, efforts are dedicated to set up harmonized reference networks at difference scales (WMO/GAW, AGAGE, ICOS).In this work, we analysed a set of continuous long-term measurements of CO2 carried out at 4 atmospheric observatories in Italy belonging to the WMO/GAW network and spanning from the Alpine region to central Mediterranean Sea: Plateau Rosa (western Italian Alps, 3480 m a.s.l.), Mt. Cimone (northern Apennines, 2165 m a.s.l.), Capo Granitola (southern Sicily coastline) and Lampedusa Island. Mt. Cimone is also a “class-2” ICOS station, while Plateau Rosa and Lampedusa are in the labelling process. Starting time of GHG observations range from 1979 for Mt. Cimone to 2015 for Capo Granitola. Due to their different locations and ecosystems, they provide useful hints to investigate CO2 variability on different latitudinal and altitudinal ranges in the Mediterranean basin and to study of natural and anthropogenic-related processes able to affect the observed variability.The study addresses primarily differences in daily and seasonal cycles at the different sites, and implemented a procedure to identify background conditions called BaDSfit (Background Data Selection for Italian stations; Trisolino et al., submitted). This methodology was originally used at Plateau Rosa station (Apadula, 2019) and it is based on the Mauna Loa data selection method (Tans and Thoning, 2008). BaDSfit consist of three steps and an optimization of the procedure was carried out with a sensitivity study. Marked differences among the daily cycles at the various sites exist. The effect of the data selection on the seasonal and diurnal cycle and long-term evolution is investigated. The BaDSfit lead to a more coherent diurnal and seasonal evolution of the different datasets, is able to identify background condition and allows the separation of local/regional scale from large scale phenomena in the CO2 time series.

In this work, eight years (2006–2013) of continuous measurements of near-surface ozone (O3) at the WMO/GAW contributing station “Concordia” (DMC, 75°06’S, 123°20’E, 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., 2008–2013), 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 “deep” 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 “synoptic” scales rather than “local” 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 “deep” 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.

In the framework of the National Project of Interest NextData, we developed automatic procedures for the flagging and formatting of trace gases, atmospheric aerosols and meteorological data to be submitted to the World Data Centers (WDCs) of the Global Atmosphere Watch program of the World Meteorological Organization (WMO/GAW). In particular, the atmospheric Essential Climate Variables (ECVs) covered in this work are observations of near-surface trace gas concentrations, aerosol properties and meteorological variables, which are under the umbrella of the World Data Center for Greenhouse Gases (WDCGG), the World Data Center for Reactive Gases, and the World Data Center for Aerosol (WDCRG and WDCA). We developed an overarching processing chain to create a number of data products (data files and reports) starting from the raw data, finally contributing to increase the maturity of these measurements. To this aim, we implemented specific routines for data filtering, flagging, format harmonization, and creation of data products, useful for detecting instrumental problems, particular atmospheric events and quick data dissemination towards stakeholders or citizens. Currently, the automatic data processing is active for a subset of ECVs at 5 measurement sites in Italy. The system represents a valuable tool to facilitate data originators towards a more efficient data production. Our effort is expected to accelerate the process of data submission to WMO/GAW or to other reference data centers or repositories. Moreover, the adoption of automatic procedures for data flagging and data correction allows to keep track of the process that led to the final validated data, and makes data evaluation and revisions more efficient by improving the traceability of the data production process.

Outdoor air pollution is responsible for more than 4 million premature deaths worldwide and its contribution is particularly severe in industrial contaminated sites, where epidemiological studies highlight often mortality rate larger than the national average. In the framework of the CISAS project, this study investigates spatial and temporal variability of air pollution across three industrial contaminated sites in southern Italy, classified as “High Risk Area of Environmental Crisis”: Crotone, Milazzo and Priolo. The environmental analysis employed three investigation approaches: - meteorological characterization of the sites with analyses of local air mass circulation; - statistical evaluation of the continuous measurements of gaseous pollutants and PM concentration; - determination of mass concentration and detailed speciation of the chemical components of atmospheric particulate matter during intensive field campaigns. Continuous trace gases and aerosol measurements (including NOx, SO2, O3, NMHC, PM10 and PM2.5) over the period 2016-2018 were analysed, and specific intensive field experiments (2016-2017), representative of winter and summer conditions, were carried out in order to determine PM10 and PM2.5 chemical composition. The analyses of PM components (ions, elemental composition, trace organic pollutants, organic carbon, and elemental carbon) show concentrations typical of rural and urban areas. The results concerning gaseous pollutants and PM concentration showed a general compliance of the concentrations of some regulated species with the limits set by the EU Ambient Air Quality (AAQ) Directive. However, in particular in the industrial areas of Milazzo and Priolo, the analysis here reported highlights the need for a stringent regulation on NMHC ambient concentration and composition, further investigation of fine particle composition and atmospheric processing, and a deeper understanding of the role of anthropogenic emissions on ozone formation, also considering the World Health Organization (WHO) limits.

The Col Margherita (MRG) Observatory is a high-altitude background station located in the Eastern Italian Alps. Its elevation and distance from major anthropogenic and natural sources make it ideal for monitoring baseline mercury levels and investigating its geochemical cycles. In this work, total gaseous mercury (TGM), ozone (O3) and meteorological variables were studied to investigate seasonal and diurnal variability of TGM measurements from March 2018 to May 2019. We found that the year-round mean TGM concentration was 1.8 times higher than the annual atmospheric mercury measurements previously reported during the GMOS project at the same measurement site. The seasonal variation of TGM was characterized by high values in spring and summer and lower values in winter. A systematic diel pattern of TGM was obtained, with low concentrations during the daytime and higher concentrations in the late evening. Spatial patterns and temporal changes in TGM, back- trajectories (BTs) and planetary boundary layer (PBL) analysis showed that total gaseous mercury levels were influenced by local meteorology, as well as regional and long-range transport of air masses. The lowest TGM concentrations in winter are associated with high wind speeds, low boundary layer height and cleaner air masses originating from the Western sector. Conversely, the highest TGM concentrations in spring and summer were attributed to polluted air masses passing over North-eastern and Continental Europe and were probably favoured by the higher PBL height. During the snow cover season, investigation of TGM peak events also demonstrated the potential influence of re-emission processes of previously reactive mercury deposition over snow surfaces.

Comparison of fine and coarse fractions in terms of sources and dynamics is scarce in southeast Mediterranean countries; differences are relevant because of the importance of natural sources like sea spray and Saharan dust advection, because most of the monitoring networks are limited to PM10. In this work, the main seasonal variabilities of sources and processes involving fine and coarse PM (particulate matter) were studied at the Environmental-Climate Observatory of Lecce (Southern Italy). Simultaneous PM2.5 and PM10 samples were collected between July 2013 and July 2014 and chemically analysed to determine concentrations of several species: OC (organic carbon) and EC (elemental carbon) via thermo-optical analysis, 9 major ions via IC, and 23 metals via ICP-MS. Data was processed through mass closure analysis and Positive Matrix Factorization (PMF) receptor model characterizing seasonal variabilities of nine sources contributions. Organic and inorganic secondary aerosol accounts for 43% of PM2.5 and 12% of PM2.5–10 with small seasonal changes. SIA (secondary inorganic aerosol) seasonal pattern is opposite to that of SOC (secondary organic carbon). SOC is larger during the cold period, sulphate (the major contributor to SIA) is larger during summer. Two forms of nitrate were identified: NaNO3, correlated with chloride depletion and aging of sea-spray, mainly present in PM2.5–10; NH4NO3 more abundant in PM2.5. Biomass burning is a relevant source with larger contribution during autumn and winter because of the influence of domestic heating, however, is not negligible in spring and summer, because of the contributions of fires and agricultural practices. Mass closure analysis and PMF results identify two soil sources: crustal associated to long range transport and carbonates associated to local resuspended dust. Both sources contributes to the coarse fraction and have different dynamics with crustal source contributing mainly in high winds from SE conditions and carbonates during high winds from North direction.

An air ion spectrometer (AIS) was deployed for the first time at the Concordia station at Dome C (75°06′ S, 123°23′ E; 3220 m a. s. l. ), Antarctica during the period 22 December 2010–16 November 2011 for measuring the number size distribution of air ions. In this work, we present results obtained from this air ion data set together with aerosol particle and meteorological data. The main processes that modify the number size distribution of air ions during the measurement period at this high-altitude site included new particle formation (NPF, observed on 85 days), wind-induced ion formation (observed on 36 days), and ion production and loss associated with cloud/fog formation (observed on 2 days). For the subset of days when none of these processes seemed to operate, the concentrations of cluster ions (0.9–1.9 nm) exhibited a clear seasonality, with high concentrations in the warm months and low concentrations in the cold. Compared to event-free days, days with NPF were observed with higher cluster ion concentrations. A number of NPF events were observed with restricted growth below 10 nm, which were termed as suppressed NPF. There was another distinct feature, namely a simultaneous presence of two or three separate NPF and subsequent growth events, which were named as multi-mode NPF events. Growth rates (GRs) were determined using two methods: the appearance time method and the mode fitting method. The former method seemed to have advantages in characterizing NPF events with a fast GR, whereas the latter method is more suitable when the GR was slow. The formation rate of 2 nm positive ions (J2+) was calculated for all the NPF events for which a GR in the 2–3 nm size range could be determined. On average, J2+ was about 0.014 cm−3 s−1. The ion production in relation to cloud/fog formation in the size range of 8–42 nm seemed to be a unique feature at Dome C, which has not been reported elsewhere. These ions may, however, either be multiply charged particles but detected as singly charged in the AIS, or be produced inside the instrument, due to the breakage of cloud condensation nuclei (CCN), possibly related to the instrumental behaviour under the extremely cold condition. For the wind-induced ion formation, our observations suggest that the ions originated more likely from atmospheric nucleation of vapours released from the snow than from mechanical charging of shattered snow flakes and ice crystals.

Mercury (Hg) and its compounds have long been known to be toxic to human health and the environment, whilst ozone (O3) is highly relevant to the Earth's climate, ecosystems and human health. Measurements of Hg and O3 in alpine environments are pivotal when evaluating air quality in natural ecosystems as well as when trying to understand regional and synoptic atmospheric transport regimes and advection of air pollutant to the Alps. This study is crucial for the evaluation of the Hg exchange processes between soil and atmosphere in a high altitude alpine environment, where increasing Hg snowpack concentrations occur during winter time, followed by Hg release to the overlying atmosphere during spring and summer time snowmelt events. In this context, evaluating the gas phase reaction between elemental mercury and ozone is essential. All the experimental activities were performed at the CNR-IDPA atmospheric observatory at Col Margherita (CMA) that is located in the Italian southeastern Alps, a UNESCO protected region far from anthropogenic and natural sources of air pollutants (altitude 2543 m a.s.l., 46°22'0.6" N, 11°47'30.9" E). The observatory is equipped with a complete weather station. Total Gaseous Mercury (TGM) was measured from March to August 2018 using a Tekran 2537B (Tekran Inc.), a mercury analyzer that alternately samples TGM on two gold traps and determines it using cold vapor atomic fluorescence spectrometry (CVAFS). During the same period, near-surface O3 measurements were performed with a Thermo 49c UV photometric analyzer (Thermo Corp.), according to WMO/GAWguidelines. For the purpose of the present study, daily and monthly levels of hourly Hg and O3 concentrations were assessed. Relationships with meteorological parameters (T, RH, P, WS, WD, solar radiation, snow) were investigated by performing a back trajectory atmospheric reanalysis using HYSPLIT for the duration of the measurement campaign. The results showed that Hg concentrations increase, on average, from spring to summer, with some episodes of rapid daytime increase or decrease of atmospheric Hg that could be related to both the O3 variability and specific weather conditions.

Measurements of Hg and O3 in alpine environments are pivotal when evaluating air quality in natural ecosystems as well as when trying to understand regional and synoptic atmospheric transport regimes and advection of air pollutant to the Alps. This study is crucial for the evaluation of Hg exchange processes between soil and atmosphere in a high-altitude alpine environment, where increasing Hg snowpack concentrations occur during winter time, followed by Hg release to the overlying atmosphere during spring and summer time snowmelt. In this context, evaluating the gas phase reaction between elemental mercury and ozone is essential. All the experimental activities were performed at the CNR-IDPA atmospheric observatory at Col Margherita (CMA) that located in the Italian South Eastern Alps, a UNESCO protected region far from anthropogenic and natural sources of air pollutants (altitude 2543 m a.s.l., 46°22'0.6" N, 11°47'30.9" E). Local meteorological conditions, ozone and Total Gaseous Mercury (TGM) has been measured from March 2018 to present. The TGM was monitored using a Tekran 2537B (Tekran Inc.) using the same protocols as used for the GMOS project. Near-surface O3 measurements were taken with a Thermo 49c UV photometric analyzer (Thermo Corp.), following WMO/GAW guidelines. In the present study, daily and monthly levels of hourly Hg and O3 concentrations were assessed and compared the meteorological parameters (i.e. T, RH, P, WS, WD, Solar Radiation, Snowpack). These mercury results obtained during the iGOSP ERA-Planet project were then compared with data taken during GMOS covering the same periods in 2014 and 2015. Notable events were investigated by performing back trajectory atmospheric reanalysis using HYSPLIT. The results showed that Hg concentrations increase, on average, from spring to summer, with some episodes of rapid daytime increase or decrease of atmospheric Hg that could be related to both the O3 variability and specific weather conditions. Another confounder is the presumed release of Hg from freshly deposited snow in the winter months resulting in a large local variability.

Nowadays a recognized need for accurate observations of atmospheric aerosols (AEs) and reactive gases (RGs) exists in the framework of regional, national and global near-surface networks based on permanent or mobile measurement stations. In this context, a paramount and not-trivial issue is related to the correct execution of continuous sampling of ambient air and its subsequent distribution to measurement analyzers hosted inside the stations. Sampling artifacts must be minimized for obtaining reliable pictures of ambient air composition. To respond to this need, a suite of novel &ldquo, smart&rdquo, and relatively low-cost systems for the continuous sampling of ambient air was developed in the framework of the 2012&ndash, 2015 I-AMICA Project. These systems were designed to execute AE and RG measurements according with WMO/GAW and ACTRIS recommendations and standard operation procedures. A particular attention was dedicated to the stabilization and control of the sampling flow rates and temperatures. The analysis of one full year of operations at the WMO/GAW regional station of Capo Granitola (GAW ID: CGR, Italy), allowed to conclude that these systems are effective in meeting the technical requirements for correct execution of AE and RG measurements.

In the framework of the National Project of Interest Nextdata, we developed procedures for the automatic flagging and formatting of trace gas, atmospheric aerosol and meteorological data to be submitted to Global Atmosphere Watch programme by the World Meteorological Organization (WMO/GAW). In this work, we describe a first prototype of a centralized system to support Italian atmospheric observatories towards a more efficient and objective data production and subsequent submission to WMO/GAW World Data Centers (WDCs). In particular, the atmospheric variables covered by this work were focused on near-surface trace gases, aerosol properties and (ancillary) meteorological parameters which are under the umbrella of the World Data Center for Greenhouse Gases (WDCGG, see https://ds.data.jma.go.jp/gmd/wdcgg/), World Data Center for Reactive Gases and World Data Center for Aerosol (WDCRG and WDCA, see http://ebas.nilu.no). For different Essential Climate Variables (ECVs), we developed specific routines for data filtering, flagging, format harmonization and creation of data products (i.e. plot of raw and valid-corrected-averaged ECV data and internal instrument parameters) useful for detecting instrumental problems or atmospheric events. A special suite of products based on the temporal aggregation of valid ECV data (like the “calendar” or “timevariation” products) were implemented for quick data dissemination towards stakeholders or citizens Currently, the automatic processing of data is active for a subset of ECVs and 4 measurement sites in Italy. The Nextdata system does not generate “consolidated” data to be directly submitted to WDCs, but it represents a valuable tool to facilitate data providers towards a more efficient data production for those data streams. Our effort is expected to accelerate the process of data submission to GAW/WMO or to other reference data centers or repositories as well as to make the data flagging more “objective”, which means that it is based on a set of well-defined selection criteria and not strictly related to the subjective judgment of station operators. Moreover, the adoption of automatic procedures for data flagging and data correction allows to keep track of the process that led to the final validated data, and makes data evaluation and revisions more efficient.

This work focuses on the near-surface O3 variability over the eastern Antarctic Plateau. In particular, eight years (2006–2013) of continuous observations at the WMO/GAW contributing station “Concordia” (Dome C–DMC: 75°06′S, 123°20′E, 3280 m) are presented, in the framework of the Italian Antarctic Research Programme (PNRA). First, the characterization of seasonal and diurnal O3 variability at DMC is provided. Then, for the period of highest data coverage (2008–2013), we investigated the role of specific atmospheric processes in affecting near-surface summer O3 variability, when O3 enhancement events (OEEs) are systematically observed at DMC (average monthly frequency peaking up to 60% in December). As deduced by a statistical selection methodology, these OEEs are affected by a significant interannual variability, both in their average O3 values and in their frequency. To explain part of this variability, we analyzed OEEs as a function of specific atmospheric variables and processes: (i) total column of O3 (TCO) and UV-A irradiance, (ii) long-range transport of air masses over the Antarctic Plateau (by Lagrangian back-trajectory analysis – LAGRANTO), (iii) occurrence of “deep” stratospheric intrusion events (by using the Lagrangian tool STLEFLUX). The overall near-surface O3 variability at DMC is controlled by a day-to-day pattern, which strongly points towards a dominating influence of processes occurring at “synoptic” scales rather than “local” processes. Even if previous studies suggested an inverse relationship between OEEs and TCO, we found a slight tendency for the annual frequency of OEEs to be higher when TCO values are higher over DMC. The annual occurrence of OEEs at DMC seems related to the total time spent by air masses over the Antarctic plateau before their arrival to DMC, suggesting the accumulation of photochemically-produced O3 during the transport, rather than a more efficient local production. Moreover, the identification of recent (i.e., 4-day old) stratospheric intrusion events by STEFLUX suggested only a minor influence (up to 3% of the period, in November) of “deep” events on the variability of near-surface summer O3 at DMC. © 2018 The Authors

We present a characterization of reactive gases (RG: O3, NO, NO2,SO2, CO) and methane (CH4) variability in the central Mediterranean basin,analyzing in situ measurements at three new permanent WMO/GAW Observatories in Southern Italy: Capo Granitola – CGR (Sicily), Lamezia Terme – LMT (Calabria) and Lecce – ECO (Apulia). At all the measurement sites, a combination of the breeze wind system (especially at CGR and LMT),PBL dynamics, anthropogenic/natural emissions, and photochemistry lead the appearance of well-defined diurnal cycles for the observed RG. According to O3/NOx variability, local emissions appeared to influence CGR and LMT (no NOx data were available for ECO during the period of study) in 4% and 20% of the hourly data, nearby sources in 39% and 40%, remote sources in 31% and 14%, while background O3/NOx were observed in 26% of cases for both the stations. Most of the background O3/NOx were observed during daytime, when offshore air masses usually affected the measurement sites. Local sources of CH4 at CGR can be related to biogenic (oxic) emissions from biomasses along the coastline, while emissions from live stocks can represent a local source of CH4 at LMT. Finally, we provide first hints about the export of O3 from Sicily/Southern Italy to the Mediterranean Sea by comparing simultaneous observations at CGR and Lampedusa (LMP), a small island in the middle of the Strait of Sicily where a WMO/GAW Regional Station is located. In summer,O3 increased by some 7 ppb for transport times lower than 48 h, while no statistical significant differences were observed for travel time longer than 48. This would suggest that photochemical O3 production occurred within air-mass travelling from CGR to LMP, but also that the central Mediterranean MBL represents a O3 sink for relatively aged air-masses.

For most parts of the year the Antarctic Plateau has a surface temperature inversion with strength c. 20 K. Under such conditions the warmer air at the top of the inversion layer contributes more to the clear sky atmospheric longwave radiation at surface level than does the colder air near the ground. Hence, it is more appropriate to relate longwave irradiance (LWI) to the top of the inversion layer temperature (Tm) than to the ground level temperature (Tg). Analysis of radio soundings carried out at Dome C and South Pole during 2006–08 shows that the temperature at 400 m above the surface (T400) is a good proxy for Tm and is linearly related to Tg with correlation coefficients greater than 0.8. During summer, radiosonde measurements show almost isothermal conditions, hence T400 still remains a good proxy for the lower troposphere maximum temperature. A methodology is presented to parameterize the clear sky effective emissivity in terms of the troposphere maximum temperature, using ground temperature measurements. The predicted LWI values for both sites are comparable with those obtained using radiative transfer models, while for Dome C the bias of 0.8 W m-2 and the root mean square (RMS) of 6.2 W m-2 are lower than those calculated with previously published parametric equations.

Variations in total ozone column and sun exposures able to cause erythema and damage the DNA molecules were observed by the narrow-band filter radiometer UV-RAD in Bologna, Italy from 2005 to 2010. The ozone columns determined from the UV-RAD measurements were found to be close to those provided by the satellite Ozone Monitoring Instrument (OMI) showing an average discrepancy of 1% with standard deviation of ± 6%. Analysis of the data highlights a well-marked annual cycle of the ozone column variations while the oscillations with periods of 8, 18 and 34 months present much smaller amplitudes. The influence of the frequency of solar irradiance measurements on the accuracy of the evaluated daily exposure dose has been studied and it was found that time intervals no longer than 5-10 min between the measurements of erythema and DNA damage effective UV irradiances provide a satisfactory assessment of the corresponding daily exposures. The latter do not present significant year-to-year variations for the period under study, while their annual distributions show slight changes likely due to the specific cloud cover and ozone column variability for different years. The annual erythemal exposure dose for 2007-2010 varied between 603.7 and 638.1 kJ m(-2), while the corresponding sun exposure affecting DNA changed from 6.38 to 7.91 kJ m(-2).

In this paper we present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC) concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard). The campaign lasted 2 years (2011–2012) and resulted in 200 vertical profiles measured during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground to put on a firmer grounds the analysis of the vertical profiles. The collected experimental data allowed a classification of the vertical profiles into different typologies which allowed to describe a seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behaviour was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude in function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the summer Arctic affecting the climate.

The object of this study was to investigate the different modal behavior of ultrafine aerosol particles collected at the Gruvebadet observatory located in Ny-lesund (Svalbard Islands, 78A degrees 55'N, 11A degrees 56'E). Aerosol particle size distribution was measured in the size range from 10 to 470 nm typically from the beginning of spring to the beginning of fall during four (non-consecutive) years (2010, 2011, 2013 and 2014). The median concentration for the whole period taken into account was 214 particles cm(-3), oscillating between the median maximum in July with a concentration of 257 particles cm(-3) and a median minimum in April with 197 particles cm(-3). The median total number concentration did not present a well-defined seasonal behavior, as shown by contrast looking at the sub/modal number concentration, where distinct trends appeared in the predominant accumulation concentration recorded during April/May and the preponderant concentration of Aitken particles during the summer months. Lastly, the short side-by-side spring 2013 campaign performed at the Zeppelin observatory with a differential mobility particle sizer was characterized by an aerosol concentration mean steady difference between the two instruments of around 14 %, thereby supporting the reliability of the device located at Gruvebadet.

Aerosol samplings were performed both at ground level and at different heights upon the Ny-Alesund polar station in June–July 2012 using a tethered balloon equipped with a sampling pump and meteorological sensors. The samples were analyzed by ion chromatography and scanning electron microscopy to characterize the sources and the evolution of the aerosol particles in the planetary boundary layer. The results show the main contribution of long-range over local/regional transported particles and sediments in the aerosols in the period of interest. Among the long-range sources, a main contribution was represented by Siberian local soils and regional wildfires which provided typical particles (metal oxides, calcareous grains), and ion species (nss-K+, nss-SO4 2−) to the aerosols. Among the local sources, a main contribution was represented by fly ash emitted by the cruise ships frequently landing around Ny-Alesund during summer. Another aspect which results from aerosol particle characterization is the clear stratification of the planetary boundary layer upon Ny-Alesund. This typical feature, which has been already documented in spring on the same site (Moroni et al. 2015), is quite effective also in summertime despite the higher potential of local dust production and the lower atmospheric stability characterizing this period.

A novel airborne gondola was developed to profile the Arctic boundary layer exploiting a tethered balloon system. A number of aerosol instrumentations were customized and deployed in the gondola for two test campaigns conducted in Ny-Ålesund in September 2014 and April–May 2015. The performances of the instrumental setup have been characterized and will be described in the present paper. An illustration of the main results and a discussion of the main phenomenology will be also presented. Briefly, the tethered balloon systems demonstrates the capability of successfully lifting up to 15 kg of scientific payload, featuring a power autonomy of about 3 h of continuous measurements with one battery. We demonstrate for the first time on a tethered balloon the capability of measuring at the same time aerosol light scattering, absorption coefficients and size distribution, which is very promising for deducing the aerosol optical properties as a function of height along the probed atmospheric column.

The present report shortly summarises the conclusions about the ozone column and solar UV irradiance variability that were achieved through the analysis of the data obtained from the narrow-band filter radiometer UV-RAD, operating at Ny-Alesund from 2008 to 2014. The polar summer gives the opportunity to register the solar irradiance 24 h per day during several months that provides comparatively long continuous time series as regards for the short- (diurnal) and medium-term (monthly) variations. To exclude the hypothesis about the artificial nature of the large amplitudes registered in the short-term ozone column variations, which can be due to the measurement or methodological errors, they were related to the corresponding variations in the solar UV radiation. In addition, these oscillations were studied using the methods developed for the analysis of non-linear dynamical systems that revealed a complex chaotic interaction between the ozone column and five other atmospheric factors. This approach leads to the conclusion that the short-term variations can be predicted for 10–20 h if a long history is available. The effect of a sporadic phenomenon, such as the ozone depletion event, occurred over Arctic in the spring of 2011, which can be considered an impulse perturbation of the medium-term ozone variations, on the mid-latitude ozone column and surface solar UV irradiance has been studied by analysing the data collected from six surface stations.

From November 2004 to December 2007, size-segregated aerosol samples were collected all-year-round at Dome C (East Antarctica) by using PM10 and PM2.5 samplers, and multi-stage impactors. The data set obtained from the chemical analysis provided the longest and the most time-resolved record of sea spray aerosol (sea salt Na+) in inner Antarctica. Sea spray showed a sharp seasonal pattern. The highest values measured in winter (Apr–Nov) were about ten times larger than in summer (Dec–Mar). For the first time, a size-distribution seasonal pattern was also shown: in winter, sea spray particles are mainly sub-micrometric, while their summer size-mode is around 1–2 μm. Meteorological analysis on a synoptic scale allowed the definition of atmospheric conditions leading sea spray to Dome C. An extreme-value approach along with specific environmental based criteria was taken to yield stronger fingerprints linking atmospheric circulation (means and anomalies) to extreme sea spray events. Air mass back-trajectory analyses for some high sea spray events allowed the identification of two major air mass pathways, reflecting different size distributions: micrometric fractions for transport from the closer Indian-Pacific sector, and sub-micrometric particles for longer trajectories over the Antarctic Plateau. The seasonal pattern of the SO 4 2 − /Na+ ratio enabled the identification of few events depleted in sulphate, with respect to the seawater composition. By using methanesulphonic acid (MSA) profile to evaluate the biogenic SO 4 2 − contribution, a more reliable sea salt sulphate was calculated. In this way, few events (mainly in April and in September) were identified originating probably from the “frost flower” source. A comparison with daily-collected superficial snow samples revealed that there is a temporal shift between aerosol and snow sea spray trends. This feature could imply a more complex deposition processes of sea spray, involving significant contribution of wet and diamond dust deposition, but further work has to be carried out to rule out the effect of wind re-distribution and to have more statistic significance.

An updated set of time series of derived aerosol optical depth (AOD) and Angstrom’s exponent a from a number of Arctic and Antarctic stations was analyzed to determine the long-termvariations of these two parameters. The Arctic measurements were performed at Ny-Alesund (1991e2010), Barrow (1977e2010) and some Siberian sites (1981e1991). The data were integrated with Level 2.0 AERONET sun-photometer measurements recorded at Hornsund, Svalbard, and Barrow for recent years, and at Tiksi for the summer 2010. The Antarctic data-set comprises sun-photometer measurements performed at Mirny (1982e2009), Neumayer (1991e2004), and Terra Nova Bay (1987e2005), and at South Pole (1977e2010). Analyses of

Downwelling and upwelling shortwave and longwave radiation components from six active polar sites, taking part of the Baseline Surface Radiation Network (BSRN), were selected for the period of the last International Polar Year (March 2007 to March 2009), and included in the BSRN-IPY dataset, along with metadata and supplementary data for some of the stations. Two sites, located at Svalbard archipelago (Ny Ålesund) and Alaska (Barrow), represent Arctic sea-level conditions. Four Antarctic stations represent both sea-level (Dronning Maud Land and Cosmonaut Sea) and high-elevation conditions (South Pole and East Antarctic Plateau). The BSRN-IPY dataset content and quality are discussed. The dataset is now available at doi:10.1594/PANGAEA.737668, and can be used for free after accepting the BSRN data release guidelines. The dataset has been summarized as monthly averages and subject to further evaluation according to strict criteria not previously applied.

Bone is an important mineral source for the entire organism especially for Ca, P, Na and trace elements like Sr, Mg, Zn and it is the reservoir for the storage and mobilization of many important ions required for the metabolic activity of the organism. The concentration of these elements are influenced by the individual diet and the content of some trace elements can be utilized as indicators of the diet of ancient populations. Bones from three differents archaeological sites found in Lombardy, Northern Italy, were investigated: (A) Roman necropolis found in Milan active from the 1st century B.C. to the 2nd century A.D; (B) Burial of the Longobard family found in Campione d'Italia (North of Lombardy) active between the 7th and 9th century A.D.; (C) Medieval necropolis of a Longobard community, found in a village near Cremona (SE of Lombardy) active in the 7th century A.D. Structures of bones and their trace element content seem to put in evidence on some differences in the way of life of the three investigated groups.