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Events of very high concentrations of 7Be cosmogenic radionuclide have been recorded at low-elevation surface stations in the subpolar regions of Europe during the cold season. With an aim to investigate the mechanisms responsible for those peak 7Be events, and in particular to verify if they are associated with the fast descent of stratospheric air masses occurring during sudden stratospheric warming (SSW) events, we analyze 7Be observations at six sampling sites in Fennoscandia during January–March 2003 when very high 7Be concentrations were observed and the Arctic vortex was relatively unstable as a consequence of several SSW events. We use the GEOS-Chem chemistry and transport model driven by the MERRA-2 meteorological reanalysis to simulate tropospheric 7Be over northern Europe. We show that the model reasonably reproduces the temporal evolution of surface 7Be concentrations observed at the six sampling sites. Our analysis of model simulations, surface 7Be observations, atmospheric soundings of ozone and temperature and surface ozone measurements indicates that the 7Be peak observed in late February 2003 (between 20 and 28 February 2003) at the six sampling sites in Fennoscandia was associated with downward transport of stratospheric vortex air that originated during an SSW that occurred a few days earlier (between 18 and 21 February 2003).

This paper concerns an in-depth analysis of an exceptional incursion of mineral dust over southern Europe in late March 2020 (27–30 March 2020). This event was associated with an anomalous circulation pattern leading to several days of PM10 (particulate matter with an aerodynamic diameter less than 10 µm) exceedances in connection with a dust source located in central Asia; this is a rare source of dust for Europe, which is more frequently affected by dust outbreaks from the Sahara Desert. The synoptic meteorological configuration was analyzed in detail, and the aerosol evolution during the transit of the dust plume over northern Italy was assessed at high time resolution by means of optical particle counting at three stations, namely Bologna, Trieste, and Mt. Cimone, allowing for the revelation of the transport timing among the three locations. Back-trajectory analyses supported by Copernicus Atmosphere Monitoring Service (CAMS) maps allowed for the location of the mineral dust source area in the Aralkum region. Therefore, the event was analyzed by observing the particle number size distribution with the support of chemical composition analysis. It is shown that the PM10 exceedance recorded is associated with a large fraction of coarse particles, which is in agreement with mineral dust properties. Both the in situ number size distribution and the vertical distribution of the dust plume were cross-checked using lidar ceilometer and aerosol optical depth (AOD) data from two nearby stations and showed that the dust plume (in contrast to those originating from the Sahara Desert) traveled close to the ground (up to a height of about 2 km). The limited mixing layer height caused by high concentrations of absorbing and scattering aerosols caused the mixing of mineral dust with other locally produced ambient aerosols, thereby potentially increasing its morbidity effects.

An experimental field campaign is designed to unveil mechanisms responsible for turbulent exchange processes when mechanical and thermal effects are entwined. The focus is an urban street canyon with a mean aspect ratio H/W of 1.65 in the business centre of a mid-size Italian city (H is the mean building height and W is the mean canyon width). The exchange processes can be characterized by time scales and time-scale ratios specific to either mechanical or thermal process. Time scales describe the mixing caused by momentum and heat exchange within different canyon layers, while their rates are surrogates of their efficacy. Given that homogeneous mixing does not always occur within the canyon, several time scales are estimated at different levels, showing that mechanical and thermal processes may both contribute to enhance mixing. By computing mechanical time scales, it is found that the fastest mixing occurs at the canyon rooftop level for perpendicular or oblique wind directions, while slow mixing occurs for parallel directions. Thermal processes are faster than the mechanical ones and are particularly efficient for perpendicular wind directions. By calculating the time-scale ratios, exchange processes are found to facilitate mixing for most wind directions and to regulate the pollutant-concentration variability in the canyon. This variability can be associated with the local-circulation regime, demarcated as thermally driven or inertially driven using a buoyancy parameter, i.e., the ratio between thermal and inertial forcings. Using this approach, a generalization of the results is proposed, enabling the extension of the current investigation to different street-canyon aspect ratios.

Terrestrial gamma radiation is mostly due to radionuclides in soil and rocks, primarily the 238U, 235U and 232Th radioactive families and 40K. This radiation contributes 15% to public exposure from all ionizing radiation sources, considering global population. Moreover, it can be used to estimate radon flux and included as one of the quantities relevant to the geogenic radon hazard model. Therefore, effort has been put into developing maps of terrestrial gamma dose rate at the regional, national or European scale, using different input data and methods. In the present work, two distinct approaches to map terrestrial gamma dose rate have been tested in the Euganean Hills district of NE Italy. The first one is based on 41 in situ measurements of ambient dose equivalent rates using a rate meter equipped with a NaI scintillator probe. The second one estimates terrestrial gamma dose rate from the U, Th and K activity concentrations in rock samples collected at the same locations of the dose rates measurements. The results obtained indicate good agreement between the two approaches, and as such suggest that the UNSCEAR 2008 prescription to derive ambient dose equivalent rate from laboratory gamma measurements produces reliable data, provided that cosmic and fall-out contributions are included. Moreover, the study proved that mapping the ambient dose equivalent rate (or terrestrial gamma dose rate) using only one database – i.e. either measured data or estimates derived from radionuclide activity concentration – yields valid results.

The natural radionuclide beryllium-7 (Be-7) is produced in the upper levels of the atmosphere and is transported to the surface on carrier aerosols. Therefore, among other factors, the abundance of Be-7 in the surface air is governed by the rate of its production and large-scale air transport. The North Atlantic Oscillation (NAO) index, which quantifies the surface sea-level pressure difference between the Subtropical (Azores) High and Subpolar low, exerts large effects on precipitation and circulation patterns in Europe. With an aim to look closely into the interrelations between the Be-7 specific activity in the surface air, sunspot number (as a proxy for the production signal), and NAO index, this paper investigates their long-term time series over 28 years, between February 1987 and December 2014. The Be-7 specific activity was recorded in Vienna (48.22 ºN; 16.35 ºE; 193 m a.s.l.), Austria, and stored in the Radioactivity Environmental Monitoring databank (REMdb) that is created and supported by the European Commission-Joint Research Centre in Ispra, Italy. The sunspot number (SN) data were downloaded from SILSO (Royal Observatory of Belgium, Brussels, Belgium), while the NAO records were retrieved from the Climate Prediction Centre of the National Oceanic and Atmospheric Administration, USA. Since the temporal resolution of the Be-7 measurements varied between six and eight days, they were first linearly interpolated into an array of weekly data, and then, the daily SN and NAO data were averaged into weekly records to match the Be-7 data. Next, Pearson’s correlation analysis and wavelet transform were used to analyse the time series. The low Pearson’s correlation coefficients between the Be-7 specific activity in the surface air and SN (-0.15207) on one hand, and the NAO index and SN (0.13512) on the other hand, imply a lack of direct linear interrelations between these variables. The Pearson’s correlation coefficient between the Be-7 specific activity in the surface air and NAO index is even lower (-0.05904). However, the Be-7 specific activity wavelet spectrum shows a pronounced annual period, and looking further into the link between the Be-7 specific activity and NAO index at this characteristic periodicity, reveals a prominent pattern. Specifically, the wavelet coherence levels between these two parameters show variations that seem to be in agreement with the 11-year solar cycle: the coherence increases as the sunspot number transitions between its extremes, and it decreases around the maxima and minima in sunspot number. Further, phase difference shows that at the one-year periodicity, the Be-7 specific activity always lags behind the NAO index. The phase difference ranges between 2 and 6 months; it reaches the minimum around the solar activity extremes, and the maximum in-between. These findings imply that, although weak, the signature of sunspot number can be seen in the wavelet coherence level between the Be-7 specific activity and NAO index.

Cooling towers (CTs) are used to dissipate excess heat from water by evaporation, common in large facilities as hospital, companies, and hotels. The main risk attributed to CTs is represented by Legionella, a Gram-negative bacterium associated with a severe form of pneumonia known as Legionnaires' disease (LD). The infection route is by inhalation of aerosols reaching the lower respiratory tract. Despite several events associated with CTs, the knowledge in this field is still limited. The aim of this study was to develop a predictive model of bioaerosol dispersion using PM10 particles as a proxy, to generate risk maps of Legionella spread in the surrounding area in several weather and microbiological conditions. The Legionella contamination in the CT basin was 40938 ± 24523 cfu/L, with four peaks independent of the season, associated with an increase in air minimum temperature values (+1–2 °C) and a high relative humidity (66–100%) preceded by rainfall (0.2–30.6 mm/day). The model revealed that the most extensive bioaerosol spread is predicted in winter and summer, with an increase in Legionella risk at a distance of up to 1.5 km from the CT. This method represents a novel integrated approach for the prevention and management of LD risk in CTs.

Mineral dust represents one of the main components of particulate matter (PM) in the Mediterranean area. The rapid identification of Saharan dust events in PM samples is desirable and required for several reasons, including their role in direct effect on climate by radiative forcing as well as their adverse effects on human health. For this purpose, the feasibility of UV–Vis Diffuse Reflectance Spectroscopy (UV–Vis DRS) is described as a rapid, inexpensive and non-destructive method of analysis of PM filters. The method developed allows to parameterize the PM filter colors and to obtain semiquantitative data related to iron oxide minerals, mainly hematite and goethite, two of the most representative minerals of Saharan dust in the Mediterranean area. The obtained results were validated based on the correlation between the spectrophotometric data of iron oxides from the membranes with the quantitative assessment of the concentration of iron by Particle Induced X-ray Emission (PIXE). Moreover, colorimetric parameterization allows setting up a classification approach for filters with potential for a posteriori use of this data in the study of the optical behavior of aerosol particles in the air. In this work, it is demonstrated how, as the concentration of iron mineral oxides and especially of hematite increases, the extent of redness color in PM filters grows up. Therefore, this technique can be extremely useful for a rapid, cheap and unambiguous identification of Saharan dust events in PM filters. The diagnosis of Saharan dust events was performed on PM10 filters with a strong mineral dust component and demonstrated with the residence time analysis of back-trajectory ensembles, proving the reliability of this non-destructive methodology. This method has the potential to be adopted by the Environmental Protection Agencies, although further evaluations are necessary and currently underway to assess their applicability not only for PM filters sampled in remote stations but also in urban stations affected by both anthropogenic pollution and Saharan dust events.

Aim of the present study is to explore how the chemical composition of particulate matter (PM) and meteorological conditions combine in shaping the air microbiome in Savona (Italy), a medium-size, heavily inhabited urban settlement, hosting a wide range of industrial activities. In particular, the air microbiome and PM10 were monitored over six months in 2012. During that time, the air microbiome was highly dynamic, fluctuating between different compositional states, likely resulting from the aerosolization of different microbiomes emission sources. According to our findings, this dynamic process depends on the combination of local meteorological parameters and particle emission sources, which may affect the prevalent aerosolized microbiomes, thus representing further fundamental tools for source apportionment in a holistic approach encompassing chemical as well as microbiological pollution. In particular, we showed that, in the investigated area, industrial emissions and winds blowing from the inlands combine with an airborne microbiome which include faecal microbiomes components, suggesting multiple citizens’ exposure to both chemicals and microorganisms of faecal origin, as related to landscape exploitation and population density. In conclusion, our findings support the need to include monitoring of the air microbiome compositional structure as a relevant factor for the final assessment of local air quality.

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 physico-chemical 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.

In this work, the climatic impacts of modifying urban surface characteristics are examined for the medium-sized city of Vantaa, Finland, in the current climate and in a projected future climate of 2040–2069. In simulations with the SURFEX air-surface interaction model with a horizontal resolution of 500 m, the fraction of green spaces and relatively sparsely built suburban-type land use was increased at the expense of more densely built commercial and industrial areas. The influence of this land use intervention was found to be rather modest but comparable to the effects of the expected climate change under the RCP8.5 greenhouse gas scenario. For temperature, the climate change is the dominating effect, while wind speed is mainly controlled by surface characteristics. For relative humidity, climate change and the imposed intervention are of comparable importance. The results of this sensitivity study are intended to support policy makers by assessing the potential impact of altering the urban layout in order to improve thermal comfort or as a countermeasure to climate warming in a high-latitude city.

Events of very high concentrations of 7Be cosmogenic radionuclide have been recorded in the subpolar regions of Europe during the cold season. With an aim to investigate the mechanisms responsible for those peak 7Be events, and in particular to verify if they are associated with the fast descent of stratospheric air masses occurring during sudden stratospheric warming (SSWs), we analyse 7Be observations at six sampling sites in Scandinavia during January–March 2003 when very high 7Be concentrations were observed and the Arctic vortex was relatively unstable as a consequence of several SSWs. We use the GEOS-Chem chemistry and transport model driven by the MERRA-2 meteorological reanalysis to simulate tropospheric 7Be over Northern Europe. We show that the model reasonably reproduces the temporal evolution of surface 7Be concentrations observed at the six sampling sites. Our analysis of model simulations, surface 7Be observations, as well as atmospheric soundings of ozone and temperature indicates that the 7Be peak observed in late February 2003 (between 20 and 28 February 2003) at the six sampling sites in Scandinavia was associated with downward transport of stratospheric vortex air originated during SSW that occurred a few days before the peak (18–21 February 2003).

In the volcanic area of the Euganean Hills district (100 km2), the indoor radon often exceeds the threshold level of 300 Bq/m3 stipulated by the Council Directive 2013/59/Euratom, thus suggesting the need to investigate the possible link between observed radon concentrations and the local geology (Trotti et al., 1998,1999; Strati et al., 2014). More recently, statistical and geostatistical analysis on rock samples identified high U, Th and K concentrations associated with areas characterised by trachyte and rhyolite lithologies (Tositti et al., 2017). With this contribution, we completed our investigation on the natural radioactivity in the Euganean Hills district extending the rocks dataset, performing on-site soil gas survey, and considering other important factors which can locally increase the radon occurrence, such as hydrothermal alterations, types of soils (e.g., geochemistry or presence of organic matters), and faults. Furthermore, we elaborated a Geogenic Radon Potential map to assess the local spatial relationships between the measured soil gas radon concentrations and seven proxy-variables: fault density (FD), total gamma radiation dose (TGDR), 220Rn (Tn), digital terrain mode (SLOPE), moisture index (MI), heat load index (HLI) and soil permeability (PERM). Empirical Bayesian Regression Kriging (EBRK) was used to develop the most accurate hazard map of the considered area, thus, providing the local administration an up-to-date decisional tool for the land use planning. For the high radon emission measured, the high density of dwelling, and its geomorphological features, the Euganean Hills district represented a very meaningful case of study. Trotti, F., Tanferi, A., Lanciai, M., Mozzo, P., Panepinto, V., Poli, S., Predicatori, F., Righetti, F., Tacconi, A., Zorzine, R., 1998. Mapping of areas with elevated indoor radon levels in Veneto. Radiat. Prot. Dosim. 78 (1), 11–14.Trotti, F., Tanferi, A., Bissolo, F., Fustegato, R., Lanciai, M., Mozzo, P., Predicatori, F., Querini, P., Righetti, F., Tacconi, A., 1999. A Survey to Map Areas with Elevated Indoor Radon Levels in Veneto, Radon in the Living Environment, 19-23 April 1999, Athens, Greece, 859–868.Strati V., Baldoncini M., Bezzon G.P, Broggini C., Buso G.P., Caciolli A., Callegari I., Carmignani L, Colonna T, Fiorentini G., Guastaldi E., Kaçeli Xhixhaf M., Mantovani F, Menegazzo R., Moub L., Rossi Alvarez C., Xhixha G., Zanon A., 2014. Total natural radioactivity, Veneto (Italy). Journal of Maps, Vol. 11, Issue 4, 545–551. http://doi.org/10.1080/17445647.2014.923348.Tositti L., Cinelli G., Brattich E., Galgaro A., Mostacci D., Mazzoli C., Massironi M., Sassi R., 2017. Assessment of lithogenic radioactivity in the Euganean Hills magmatic district (NE Italy). J. Environ. Radioact. 166, 259–269. https://doi.org/10.1016/j.jenvrad.2016.07.011

The Euganean Hills of North East Italy have long been recognised as an area characterized by a higher than average natural radiation background. This is due to two main reasons: a) primary lithogenic radiation due to rhyolitic and trachytic outcrops, which are “acidic alkaline” magmatic rocks potentially enriched in uranium and thorium; b) secondary sources related to a geothermal field – widely exploited for spa tourism in the area since the Roman age – producing surface release of radon-enriched fluids. Though radioactivity levels in the Euganean district have been often investigated in the past – including recent works aimed at assessing the radiation doses from radon and/or total gamma radiation – no effort has been put so far into producing a thorough assessment linking radiation protection data to geological-structural features (lithology, faults, water, organic matter content, etc.). This work represents the first part of the interdisciplinary project “Geological and geochemical control on Radon occurrence and natural radioactivity in the Euganean Hills district (North-Eastern Italy)”, aimed at producing detailed results of the actual radiation levels in connection mainly with lithological parameters. A detailed sampling strategy, based on lithostratigraphy, petrology and mineralogy, has been adopted. The 151 rock samples collected were analyzed by high resolution γ-ray spectrometry with ex situ HPGe detectors. Statistical and geostatistical analyses were performed, and outlier values of U and Th – possibly associated with anomalies in the geological formation – were identified. U, Th and K concentration maps were developed using both the entire database and then again after expunging the outliers; the two were then compared. In all maps the highest values can be associated to trachyte and rhyolite lithologies, and the lowest ones to sedimentary formations. The external dose due to natural radionuclides in the soil – the so called terrestrial gamma dose rate – has been calculated using the U, Th and K distribution measured in the bedrock samples.

Green infrastructure (GI) in urban areas may be adopted as a passive control system to reduce airpollutant concentrations. However, current dispersion models offer limited modelling options to evaluate its impact on ambient pollutant concentrations. The scope of this review revolves around the following question: how can GI be considered in readily available dispersion models to allow evaluation of its impacts on pollutant concentrations and health risk assessment? We examined the published literature on the parameterisation ofdeposition velocitiesand datasets for bothparticulate matterandgaseous pollutantsthat are required for deposition schemes. We evaluated the limitations of different air pollution dispersion models at two spatial scales –microscale(i.e. 10–500 m) and macroscale (i.e. 5–100 km) - in considering the effects of GI onair pollutantconcentrations and exposure alteration. We conclude that the deposition schemes that represent GI impacts in detail are complex, resource-intensive, and involve an abundant volume of input data. An appropriate handling of GI characteristics (such as aerodynamic effect, deposition of air pollutants and surface roughness) in dispersion models is necessary for understanding the mechanism of air pollutant concentrations simulation in presence of GI at different spatial scales. The impacts of GI on air pollutant concentrations and health risk assessment (e.g., mortality, morbidity) are partly explored. The i-Tree tool with the BenMap model has been used to estimate the health outcomes of annually-averaged air pollutant removed by deposition over GI canopies at the macroscale. However, studies relating air pollution health risk assessments due to GI-related changes in short-term exposure, via pollutant concentrations redistribution at the microscale and enhanced atmospheric pollutant dilution by increasedsurface roughnessat the macroscale, along with deposition, are rare. Suitable treatments of all physical and chemical processes in coupled dispersion-deposition models and assessments against real-world scenarios are vital for health risk assessments.

Here we explore how the chemical composition of particulate matter (PM) and meteorological conditions combine in shaping the air microbiome in a heavily inhabited industrial urban settlement. During the observation time, the air microbiome was highly dynamic, fluctuating between different compositional states, likely resulting from the aerosolization of different microbiomes emission sources. This dynamic process depends on the combination of local meteorological parameters and particle emission sources, which may affect the prevalent aerosolized microbiomes. In particular, we showed that, in the investigated area, industrial emissions and winds blowing from the inlands combine with an airborne microbiome that includes faecal microbiomes components, suggesting multiple citizens’ exposure to both chemicals and microorganisms of faecal origin, as related to landscape exploitation and population density. In conclusion, our findings support the need to include monitoring of the air microbiome compositional structure as a relevant factor for the final assessment of local air quality.

Low-cost sensors based on the optical particle counter (OPC) are increasingly being used to collect particulate matter (PM) data at high space and time resolution. In spite of their huge explorative potential, practical guidelines and recommendations for their use are still limited. In this work, we outline a few best practices for the optimal use of PM low-cost sensors based on the results of an intensive field campaign performed in Bologna (44&deg, 30&prime, N, 11&deg, 21&prime, E, Italy) under different weather conditions. Briefly, the performances of a series of sensors were evaluated against a calibrated mainstream OPC with a heated inlet, using a robust approach based on a suite of statistical indexes capable of evaluating both correlations and biases in respect to the reference sensor. Our results show that the sensor performance is sensibly affected by both time resolution and weather with biases maximized at high time resolution and high relative humidity. Optimization of PM data obtained is therefore achievable by lowering time resolution and applying suitable correction factors for hygroscopic growth based on the inherent particle size distribution.

Travel demand management measures/policies are important to sustain positive changes among individuals' travel behaviour. An integrated agent-based microsimulation platform provides a rich framework for examining such interventions to assess their impacts using indicators about demand as well as supply side. This paper presents an approach, where individual schedules, derived from a lighter version of an activity-based model, are fed into a MATSIM simulation framework. Simulations are performed for two European cities i.e. Hasselt (Belgium), Bologna (Italy). After calibrating the modelling framework against aggregate traffic counts for the base case, the impacts of a few traffic management policies (restricting car access, increase in bus frequency) are examined. The results indicate that restricting car access is more effective in terms of reducing traffic from the network and also shifting car drivers/passengers to other modes of travel. The enhancement of bus infrastructure in relation to increase in frequency caused shifting of bicyclist towards public transport, which is an undesirable result of the policy if the objective is to improve sustainability and environment. In future research, the framework will be enhanced to integrate emission and air dispersion models to ascertain effects on air quality as a result of such interventions., Comment: Post-print

Many industrial by-products contain Naturally Occurring Radioactive Materials (NORM) that normally represent a cost in terms of monitoring, risk management and storage. When included in new mix designs of bricks, these materials may become a valuable sustainable resource. Before marketing, companies involved in development and commercialization of these new building materials ensure safety related to radiation, usually by assessing radon-related risk. According to the Council Directive 2013/59/Euratom, both raw materials and final products used in building constructions need to be tested for activity concentration. The present work explores the radionuclide concentration and the radon exhalation of bricks obtained recycling different types of potentially radioactive wastes: i) trachyte as by-product resulting from quarrying operations, and ii) two different types of industrial sludge derived from ceramic tiles industry. Raw materials were studied to foresee any potential radioactive risk derived from their use as secondary raw materials, while bricks were investigated to assess the influence of mineralogy and texture on their radioactive properties and their effective radon-risk. The results obtained here show that, although radon emanation in bricks is primarily determined by radionuclide concentration in the raw materials, textural features significantly affect radon mobility and exhalation.

The abatement performance of photocatalytic coatings on NOx concentrations in real-world street canyons remains an open question considering the very different conclusions reached by the few previous field studies. To fill this gap, an intensive experimental campaign was carried out in summer 2018 in the outskirts of Bologna in Italy. The experimental design involved two parallel street canyons in an open-air controlled environment fully instrumented for measuring air pollutant concentrations, meteorological and turbulence variables in presence of a photocatalytic coating. Specifically, the coating utilized TiO2 photocatalysts. Several controlled pollutant release experiments with a known pollutant source were conducted within the two canyons, of which one coated with TiO2 and the other free (reference canyon). The comparison of observations in the two canyons indicated a distinct behavior of airflows, leading to higher concentrations in the coated canyon. Three independent methods were developed to demonstrate the abatement performance of the coatings in an open-air controlled environment. The first method involved the comparison of the two canyons before and after the application of the coating; the second one regarded the derivation of normalized concentrations to remove the effect of the different geometry and dilution volume of the canyons; the third method involved dispersion modeling simulations conducted during the controlled pollutant release experiments. All the three methods demonstrated a photocatalytic reduction of NOx in the range of 14–21%, suggesting the potential effect of photocatalysis under real weather conditions.

The complex interaction between the Urban Heat Island (UHI), local circulation, and air quality requires new methods of analysis. To this end, this study investigates the multiple scale nature of the UHI and its relationship with flow and pollutant dispersion in urban street canyons with and without the presence of vegetation. Two field experimental campaigns, one in summer and one in winter, were carefully designed in two parallel urban street canyons in the city of Bologna (44&deg, 29&prime, N, 11&deg, 20&prime, E, Italy) characterized by a similar orientation with respect to the impinging background flow but with a different aspect ratio and a different presence of vegetation. In addition to standard meteorological variables, the dataset collected included high-resolution flow data at three levels and concentration data of several pollutants. The UHI has been evaluated by combining surface temperature of building facades and ground surfaces acquired during two intensive thermographic campaigns with air temperature from several stations in order to verify the presence of intra-city neighborhood scale UHIs additional to the more classical urban&ndash, rural temperature differences. The presence of trees together with the different morphologies was shown to mitigate the UHI intensity of around 40% by comparing its value in the center of the city free of vegetation and the residential area. To capture the multiple-scale nature of UHI development, a simple relationship for the UHI convergence velocity, used as a surrogate for UHI strength, is proposed and used to establish the relationship with pollutant concentrations. The reliability of the proposed relationship has been verified using a Computational Fluid Dynamics (CFD) approach. The existence of a robust relationship between UHI strength and pollutant concentration may indicate that the positive effect of mitigation solutions in improving urban thermal comfort likely will also positively impact on air pollution. These results may be useful for a quick assessment of the pollutant accumulation potential in urban street canyons.

This study provides an analysis of a five-year time series chemical composition of the bulk deposition (2009–2013), collected within a farm surrounded by industrial and urban settlements in a semi-rural area of the Po Valley, with the aim of characterizing potential emission sources affecting precipitation composition at the site. Most monitoring efforts in this region, recognized as one of the most polluted in the world both due to the intense industrialisation and urbanisation as well as to frequent air stagnation conditions, are presently devoted more to gaseous and particulate pollutants than to precipitation chemistry. The bulk deposition samples were very concentrated in chemical species, both acidic and alkaline, high compared to other polluted sites in the world and to locations in the same district. The mean ions concentrations (in μeq l−1) are: NO3 − (243) > SO4 2− (220) > PO4 3− (176) > Cl− (153) > NO2 − (29) > F− (2.6); NH4 + (504) > Ca2+ (489) > K+ (151) > Na+ (127) > Mg2+ (127). pH data shows a trend toward slightly alkaline conditions attributed to the large presence of ammonium and crustal elements, in spite of high concentrations of nitrates and sulphates. The relevant concentrations of Ca2+ and Mg2+ further suggests that these alkaline conditions might be due to the correspondingly significant concentrations of carbonates/bicarbonates in our dataset. While back-trajectories analysis suggests the stronger importance of local resuspension over long-range transport, statistical analyses on ion composition highlight the key role exerted by agricultural activity, especially in the case of NH4 +, K+, Ca2+ and PO4 3− (especially linked to fertilisation practices and soil resuspension due to mechanical operations). Apart from Na+ and Cl− ions which correlate well as expected, indicating their likely common origin from marine salt, the identification of the origin of the other ions is very complex due to the contribution of diverse local sources, such as industrial and residential settlements.

This work aims at determining the characteristics and the preferred source regions of stratospheric air masses at the Mt. Cimone World Meteorological Organization-Global Atmosphere Watch station located in the Italian northern Apennines (44°11′N, 10°42′E, 2165 m above sea level) , a site which is considered representative of Southern Europe-Mediterranean free troposphere. Source regions of high concentrations of 7Be, 7Be/210Pb, and O3 and regions originating high potential vorticity values are analyzed by means of trajectory statistical methods applied over the time series collected in the period of 1998–2011 to this aim. Our analysis points out the frequent occurrence of stratosphere-to-troposphere exchange in the North America and northern Atlantic region, which can be linked to the usual location of the polar-front and subtropical jet streams in these two regions, but also to the tropopause discontinuity and to the high cyclogenetic activity in the Atlantic region. High 7Be concentrations associated with trajectories of high-latitude origin descend from high altitudes to the study site, while at midlatitudes trajectories arrive from relatively lower levels. The geographical distribution of the tropopause crossing of air masses before arriving the study site points out particularly to Greenland. Our results also suggest the importance of the interaction between upper level disturbances and the Alps mountain range as a driver for stratosphere-to-troposphere exchange. In this case, the time between the tropopause crossing and the arrival at the elevated study site is less than 24 h and frequently below 6 h. The Atlas range in northern Africa plays a similar role though with lower influence.

We apply the Global Modeling Initiative (GMI) chemistry and transport model driven by NASA's MERRA assimilated meteorological data to simulate the seasonal variations in two radionuclide aerosol tracers (terrigenous 210Pb and cosmogenic 7Be) at the WMO-GAW station of Mt. Cimone (44°12′ N, 10°42′ E; 2165 m a.s.l.; Italy), which is representative of free-tropospheric conditions most of the year, during 2005 with an aim to understand the roles of transport and precipitation scavenging processes in controlling their seasonality. The total precipitation field in the MERRA data set is evaluated with the Global Precipitation Climatology Project (GPCP) observations, and generally good agreement is found. The model reproduces reasonably the observed seasonal pattern of 210Pb concentrations, characterized by a wintertime minimum due to lower 222Rn emissions and weaker uplift from the boundary layer and summertime maxima resulting from strong convection over the continent. The observed seasonal behavior of 7Be concentrations shows a winter minimum, a summer maximum, and a secondary spring maximum. The model captures the observed 7Be pattern in winter–spring, which is linked to the larger stratospheric influence during spring. However, the model tends to underestimate the observed 7Be concentrations in summer, partially due to the sensitivity to spatial sampling in the model. Model sensitivity experiments indicate a dominant role of precipitation scavenging (vs. dry deposition and convection) in controlling the seasonality of 210Pb and 7Be concentrations at Mt. Cimone.

This work regards a comprehensive analysis of the overall distribution of 7Be activity concentrations in Spain and the synoptic meteorological conditions associated with the highest 7Be peaks (>8 mBq/m3). The use of four sampling stations (Barcelona, Bilbao, Madrid, and Sevilla) included in REMdb, with different latitudinal location, as well as the relatively long time period used in this study (2001e2010), allowed to improve the understanding of 7Be spatio-temporal distribution in Spain. The comparison of the 7Be activity concentrations mean values indicated a north-south gradient (from 3.1 ± 1.1 mBq/m3 in Bilbao to 4.0 ± 1.8 mBq/m3 in Sevilla), even though not statistically significant (as indicated by the t-test). However, the analysis of frequency distributions and temporal evolutions of 7Be activity concentrations have suggested the presence of two main areas, namely northern (Bilbao and Barcelona) and southern (Sevilla) Spain. The identification and analysis of periods associated with the highest values of 7Be have allowed studying the different synoptic patterns associated with stratosphericetropospheric transport (STT). In particular, three episodes (one in the north and two in the south) potentially associated with vigorous STT have been identified and analysed in detail. The results displayed that the omega block configuration, extending either over western Russia and Scandinavia or into the Atlantic Ocean, forced the prevailing jet stream to the northeast and south of Spain respectively with subsequent subsidence. In summer, this blocking configuration at high latitudes was combined with the presence of the Azores high pressure system to the west of Spain, affecting the 7Be activity concentration recorded in the south.

This paper describes the aerosol measurement setup and results obtained during the BEXUS18 (Balloon-borne Experiments for University Students) stratospheric balloon within the A5-Unibo (Advanced Atmospheric Aerosol Acquisition and Analysis) experiment performed on 10 October 2014 in northern Sweden (Kiruna). The experimental setup was designed and developed by the University of Bologna with the aim of collecting and analyzing vertical profiles of atmospheric ions and particles together with atmospheric parameters (temperature, relative humidity, and pressure) all along the stratospheric ascent of the BEXUS18 stratospheric balloon. Particle size distributions were measured with the MeteoModem Light Optical Aerosol Counter (LOAC) and air ion density was measured with a set of two commercial and portable ion counters. Though the experimental setup was based upon relatively low-cost and light-weight sensors, vertical profiles of all the parameters up to an altitude of about 27 km were successfully collected. The results obtained are useful for elucidating the relationships between aerosols and charged particles between ground level and the stratosphere, with great potential in collecting and adding useful information in this field, also in the stratosphere where such measurements are rare. In particular, the equipment detected coherent vertical profiles for particles and ions, with a particularly strong correlation between negative ions and fine particles, possibly resulting from proposed associations between cosmic rays and ions as previously suggested. In addition, the detection of charged aerosols in the stratosphere is in agreement with the results obtained by a previous flight and with simulations conducted with a stratospheric ion–aerosol model. However, further measurements under stratospheric balloon flights equipped with a similar setup are needed to reach general conclusions about such important issues.

Since 2015, a scientific collaboration network between the University of Belgrade, the University of Bologna and the Radioactive Monitoring Environmental (REM) group of the European Commission Joint Research Centre – Ispra, has addressed the characterisation of the beryllium-7 concentration in the surface air recorded across Europe, and its link with meteorological conditions. A set of studies carried out over this period has been based on the beryllium-7 activity measurements collected and validated by the Radioactivity Monitoring Environmental Data Bank (REMdb) (https://rem.jrc.ec.europa.eu/RemWeb/Index.aspx). REMdb makes accessible and understandable to a wider audience radioactivity measurements made by all European Member States in the air, water, milk, and mixed diet. Thus, the scientific community is given research opportunities to exploit a unique collection of almost 5 million environmental radioactivity measurements taken across Europe since 1988. Our collaboration has also investigated other sets of multidecadal beryllium-7 activity concentrations: 1) sampled in Serbia and measured at the Vinča Institute of Nuclear Sciences, and 2) sampled in Slovenia and measured at the Jožef Stefan Institute. This paper compiles our current understanding of the abundance of beryllium-7, which is a naturally occurring radionuclide, in the surface air in Europe. Beryllium-7 is produced in the upper troposphere-lower stratosphere (UT-LS) region, where it attaches to fine aerosols and is then transported through the atmosphere. Due to its origin, it is considered a good tracer of air mass history, and it can be used as an indicator of different processes in the atmosphere, such as vertical exchange across the UT-LS region. Based on a number of our previous studies, we here give an overall picture of the beryllium-7 activity concentration distribution in Europe. We describe its general decrease from the south of the continent towards the polar region, different periodicities and outliers identified in the time series, and we make an effort to identify the underlying driving mechanisms that give rise to this distribution. We also look into temporal trends that show a statistically significant increase in the beryllium-7 surface concentration. Since temperature is one of the major factors that influence this radionuclide’s abundance in the air, we speculate that the trends are affected by the global increase in temperature. For that reason, we intend to further inquire into the possibility of using the beryllium-7 surface concentration as an indicator of climate change.

The activity concentrations of beryllium-7, a natural radiotracer that is considered as a tracer of the strato-spheric-tropospheric exchange, shows a distinct behaviour in Northern Europe compared to the central and southern parts of the continent. In this study, we use the measurements collected at four sampling stations in Scandinavia (Ivalo, Umea, Kista, Risoe) between 2001 and 2010 and investigate their trends, periodicities and residuals with the aim to further understand the common features in the beryllium-7 data records in northern sampling sites. The beryllium-7 activity concentrations exhibit statistically significant positive trends that range from an average value of 1.50%/year to an average value of 2.96%/year. We detect a one-year periodicity in all the sites, and in the southernmost site, Risoe in Denmark, additional higher-frequency harmonics. In the residual time series, we find outliers that represent occurrences of extremely high beryllium-7 activity concentration. Cross-correlations of the beryllium-7 residuals across the four sites decrease with increasing distance; similarly, as indicated by local Hurst exponents the records exhibit long-range correlations that weaken towards the end of the investigated period. To investigate the causes of the detected trends, we also calculate correlations between beryllium-7 and factors related to its production, transport and removal from the atmosphere: in particular, cross-correlations of the beryllium-7 residuals with residuals in sunspot number, local temperature, atmospheric pressure and precipitation, as well as Arctic Oscillation index and North Atlantic Oscillation index. Most of the obtained correlations, however, are not statistically significant, highlighting the need to analyse a longer time period in order to evaluate the impact of different factors on the airborne beryllium-7 activity concentration.

Informational interventions are important to bring positive changes in attitudes and perception among individuals. In relation to the individual’s mobility behavior, habits, attitudes, and perceptions are difficult to change. Therefore, it is vital to identify relatively soft aspects of travel behavior with a potential to reduce the negative impacts of mobility on the environment and individual health. This paper provides a methodological framework and describes the development of a computational algorithm that helps to identify soft changes in the travel behavior. The algorithm is based on a variety of different data sources such as activity-travel diaries and related constraint information, meteorological conditions, bicycle and public transport supply data, and emissions and air pollutant concentrations data. A variety of rules that are part of the algorithm are derived from the transport modeling literature, where constraints and factors were examined for activity-travel decisions. Three major aspects of activitytravel behavior, such as reduced car use, cold start of car engines, and participation in non-mandatory outdoor activities are considered in assessing pro-environmental potential. The algorithm is applied to collected small datasets from citizens of Hasselt (Belgium), Bologna (Italy), and Guildford (UK). A significant replaceable potential for car trips within 3 km to cycling and car trips to public transport has been found. The replaceable potential of excessive cold starts and participation in non-mandatory outdoor activities were also found, to some extent, to bring positive changes in the environment. In future research, these identified potentials are reported back to individuals with their consequence as part of a mobility-based informational intervention. This project has received funding from the European Union Horizon 2020 research and innovation program under grant agreement no. 689954.

The present study analyses the peak 210Pb activity concentrations observed all over the 1998–2011 period at the WMO-GAW high altitude site of Mt. Cimone (44.18N, 10.7E, 2165 m asl; Italy) in terms of meteorological conditions, links with other atmospheric species and population dose rate associated with this radiotracer. The highest 210Pb events mainly occurred in the warm period and were associated with prolonged anticyclonic conditions, high temperatures, and low relative humidity values. A correlation with the seasonal pattern of the mixing height was also observed, suggesting the importance of thermal convection promoting uplift of warm air from the atmospheric boundary layer (ABL), transporting high concentrations of 222Rn and thus 210Pb. The main sources of high 210Pb concentrations were identified by means of clusters of back-trajectories applied at three different heights. Sources located at east (central Europe), at west (Spain and France) and south (northern Africa) of Mt. Cimone were distinguished. The clusters obtained at the three heights were compared in order to study the extent between ABL and free troposphere during the highest 210Pb events: a wide influence of the strong coupling among atmospheric vertical layers on 210Pb activity concentrations increases was demonstrated. The annual effective dose from the potential inhalation of this radionuclide during the peak concentration episodes was also calculated. The average dose increase during the selected events represents only a small fraction of the total dose from all sources; these results are nevertheless useful for providing information on natural background dose contribution from inhalation which is required for the accurate assessment of dosimetric conditions in the case of nuclear emergencies.

Motivated by the increasing interest on passive control solutions to lower pollutant concentrations in cities, this paper introduces a novel methodology to demonstrate the potential of photocatalytic coatings in abating air pollution in real-world urban environments. The methodology introduced in this paper is based on an original application of Computational Fluid Dynamic (CFD) modelling to simulate the effect of photocatalytic coatings in real yet simplified urban setting. The numerical approach is validated against observations gathered during an ad-hoc designed intensive experimental campaign performed in a real urban area in the city of Bologna, Italy (44.5075 N, 11.3514E), under semi-controlled conditions. Comparison of the model output with observations show a concentration reduction in the range 10–20%. After validation and choice of the proper model set-up, numerical simulations are analyzed by focusing on the mechanisms enhancing the flow circulation within the canyon, an effect that may increase the effect of coatings within street canyons. Results show that application of photocatalytic coatings can give pollutant reductions up to 50% in a confined region close to the walls. A parametrization for the pollutant reduction within the street canyon is suggested to summarize these results, providing a characterization of the photocatalytic coatings performances as a function of the geometric characteristic of the street canyon.

Seasonal and spatial patterns of extremely high beryllium-7 surface concentration recorded over the 2001-2010 period across Europe are investigated. The beryllium-7 measurements for 14 sites are taken from the Radioactivity Environmental Monitoring Database. The maxima and minima in the annual cycle of the beryllium-7 surface concentration occur later in the year as the latitude of the measurement site decreases. Extremely high beryllium-7 surface concentrations are defined here as values greater than the 95th percentile in each measurement site. Most of the extremes occur over the March-August period. At least 10 % of the total number of extremes appear during autumn and winter, with an exception of Vienna, where all the extremes took place during spring and summer. The regional spread of extremes common to pairs of measurement sites points to an existence of three distinct regions in Europe: north of 55°N, between 45°N and 55°N, and south of 45°N. Although the beryllium-7 concentration records are significantly correlated across all the investigated sites, the strongest correlations are found within the identified regions. Sezonska i prostorna raspodela ekstremno visokih specifičnih aktivnosti berilijuma-7 u prizemnom sloju atmosfere analizirane su u ovom radu. Merenja tokom 2001-2010. godine na 14 evropskih stanica preuzeta su iz REMdb-baze podataka Monitoring radioaktivnosti u životnoj sredini. Prvo su razmotreni godišnji ciklusi specifične aktivnosti berilijuma-7 koji pokazuju da se godišnje maksimalne i minimalne srednje mesečne vrednosti pomeraju ka kasnijim mesecima kako se smanjuje geografska širina merne stanice. Za ekstremno visoke vrednosti specifične aktivnosti berilijuma-7 uzete su vrednosti veće od 95-og percentila, koji je izračunat za svaku stanicu posebno. Najveći broj ovih ekstrema događa se od marta do avgusta, a najmanje 10 % od ukupnog broja ekstrema tokom jeseni i zime. Izuzetak je merna stanica Beč na kojoj su se svi ekstremi dogodili tokom proleća i leta. Rasprostranjenost ekstrema koji su zajednički za parove mernih mesta, ukazuje da postoje tri različita regiona u Evropi: severno od 55°N, između 45°N i 55°N, i južno od 45°N. Iako su merenja specifične aktivnosti berilijuma-7 značajno korelisana za sve analizirane stanice, najveći koeficijenti korelacije dobijeni su u okviru ovih regiona.

Vulsini Volcanic district in Northern Latium (Central Italy) is characterized by high natural radiation background resulting from the high concentrations of uranium, thorium and potassium in the volcanic products. In order to estimate the radon radiation risk, a series of soil gas radon measurements were carried out in Bolsena, the principal urban settlement in this area NE of Rome. Soil gas radon concentration ranges between 7 and 176 kBq/m(3) indicating a large degree of variability in the NORM content and behavior of the parent soil material related in particular to the occurrence of two different lithologies. Soil gas radon mapping confirmed the existence of two different areas: one along the shoreline of the Bolsena lake, characterized by low soil radon level, due to a prevailing alluvial lithology; another close to the Bolsena village with high soil radon level due to the presence of the high radioactive volcanic rocks of the Vulsini volcanic district. Radon risk assessment, based on soil gas radon and permeability data, results in a map where the alluvial area is characterized by a probability to be an area with high Radon Index lower than 20 %, while probabilities higher than 30 % and also above 50 % are found close to the Bolsena village.

The long-term contemporary 210Pb time series acquired during the period 2004–2011 at two distant sites of different altitude in the Mediterranean basin, El Arenosillo (40 m a.s.l. in southwestern Spain) and Mt. Cimone (2165 m a.s.l. in northern Italy), are analyzed and compared. Besides being considered a tracer of continental air masses, 210Pb radionuclide is also a proxy of fine stable aerosol. For this reason, the measurements of PM10 mass concentrations collected at the same time and the corresponding 210Pb/PM10 ratio at the two sites are considered to gain better insights into the origin and size of the particles. Three statistical trajectory methods are applied to identify and characterize the 210Pb source regions at the two sites. The three methods yield similar outcomes in the source identification, which strengthens the robustness of our results. In addition to the importance of the transport from areas of continental Europe, this study highlights the relevant role of the Mediterranean Sea as a major 210Pb reservoir layer associated to the aged air masses that accumulate in the western Mediterranean basin. The analysis of the sources points out the significant influence of northern Africa to 210Pb increases at both sites as well, even though the most intensive episodes are not of Saharan origin.

Relationships are analysed between advection pathways and atmospheric composition at the high-mountain station of Mt. Cimone (Italy), between 1998 and 2011. Back-trajectory cluster analysis identifies eight main advection pathways. A connection is demonstrated between the seasonality of airmass transport and atmospheric composition. Temporal trends and correlation of variables, flow types and teleconnection indices show, among other, decreasing trends of 210Pb (a radionuclide of crustal origin; −0.008 mBq m−3 year−1) as well as PM10 (−0.15 μg m−3 year−1), indicating that previously observed downward PM10 trends in Europe may actually be attributable to a combination of meteorological factors and decreasing anthropogenic emissions. The detection of a positive (negative) correlation of these tracers with Western (Arctic) air masses, showing significant downward (upward) trends at the study site, further confirms our findings. Lastly, relationships between teleconnection indices and atmospheric transport types/atmospheric variables are further analysed, focusing on large-scale atmospheric circulation indices and regional low-frequency atmospheric circulation pathways, the Mediterranean Oscillation and the Western Mediterranean Oscillation. The analysis reveals the important influence of such regional indices on the advection pathways.

The maxima in a large dataset of the beryllium-7 specific activities measured in surface air in Helsinki, Finland, over 25 years (1987-2011), are analysed. The measurements at this station were performed with a varying temporal resolution: weekly until 1999, and daily, or once in two days, in the subsequent years, with a final dataset consisting of more than 4000 measurements. These data are stored by the online Radioactivity Environmental Monitoring (REM) Database. The beryllium-7 extremes in this dataset are defined as events with the beryllium-7 specific activity above the 95thpercentile, or in other words, as the maximum 5 % of the measured values. Specifically, for the Helsinki data set, this threshold is 4.82·10-3 Bq m-3. The beryllium-7 specific activity in Helsinki shows a seasonal pattern with the monthly means above 2.00·10-3 Bq m-3 during the warm season (April–September), and below 2.00·10-3 Bq m-3during the cold season (October–March). The analysis of the extremes shows that 90 % occurred in the warm season, and the remaining 10 % in the cold season. The occurrence of the extreme beryllium-7 events during the cold season is therefore of particular interest, and these “cold extremes” are analysed in more detail. Amongst the cold extremes, three extreme episodes are identified. These episodes, which occurred in March 1999, February 2003 and February 2005, show extremely high berrylium-7 specific activities measured over several consecutive days. Potential vorticity and surface temperature maps over Europe are investigated in attempt to find underlying mechanisms that cause high concentrations of beryllium-7 in surface air during the cold season.

Under the terms of Article 36 of the Euratom Treaty, European Union Member States (MSs) shall periodically communicate to the European Commission (EC) information on environmental radioactivity levels. These results have been introduced into the Radioactivity Environmental Monitoring database (REMdb) of the EC Joint Research Centre (JRC) sited in Ispra (Italy) (https://rem.jrc.ec.europa.eu/RemWeb/). The initial purpose of the REMdb was to bring together environmental radioactivity data produced in the aftermath of the Chernobyl accident, and to store them in a harmonised manner. Thus the database has two main objectives: 1) to collect the environmental radioactivity data gathered through the national environmental monitoring programs of the MSs to prepare comprehensive annual monitoring reports; and 2) to keep a historical record of the radiological accidents for scientific studies. Nowadays, containing nearly two million records of radioactivity levels in milk, water, air and mixed diet received from the MSs, the REMdb offers the scientific community dealing with environmental radioactivity endless research opportunities. The records stored in REMdb prior to 2007 are fully public, while the access to the data from the 2007-2015 period can be granted only after explicit request. This fact makes the REMdb a useful and unique pillar on which to perform environmental radioactivity studies at the European level, and which can be considered as a liaison platform between national and international scientific groups conducting collaborative research. Example of collaboration: Analysis of 7Be surface concentrations As a valuable proof of this use, the present work provides an overview of the research activity undertaken by a friendly scientific collaboration network created by the University of Belgrade, the University of Bologna and the REM group of the JRC in the study of the 7Be surface concentrations recorded across Europe. These sets of results represent one of the first attempts to better understand the 7Be distribution in Europe, as well as the impact of tropopause height (TPH) and other meteorological parameters exert on it.First, spatial and temporal distribution of the 7Be specific activity in surface air was carried out using the long-term database (1984–2011) of 34 sampling sites, focusing on describing the impact of the latitude and solar cycle on yearly and monthly concentrations (Hernández-Ceballos et al., 2015). Further, a cluster analysis was instead applied to identify spatial patterns in 7Be concentrations in Europe: results showed the presence of three distinguishable cluster groups (south, central and north of Europe) with clear differences between concentrations in both intensity and time trends, and with a latitudinal distribution of the sampling stations (Hernández-Ceballos et al., 2016a). These regions were also identified in an analysis of seasonal and spatial patterns of extremely high 7Be surface concentration (values above 95th percentile in each site) recorded over the 2001–2010 period across Europe (Ajtić et al., 2016a). This study reported that most of the extremes occur over the March–August period, while at least 10 % of the total number of extremes take place during autumn and winter. In Ajtić et al., 2016b these “cold extremes” were analysed in more detail, showing three meteorological scenarios associated with their occurrence in northern Europe. In these works, the impact of TPH on 7Be, and therefore, on the spatial distribution of 7Be in Europe, was also suggested. The influence of TPH on 7Be was further investigated in a separate study (Hernández-Ceballos et al., 2016b), which showed a larger TPH influence on 7Be during summer and a large spatial variability of TPH on 7Be levels with a clear gap between southern and northern Europe in the area of the polar front jet.

A severe PM10 episode was observed at the high elevation observatory of Mt. Cimone (2165 m a.s.l.) in the period of 13th-15th March 2004; during the event PM10 reached the maximum concentration (80 μg m−3 against an average of 8.8 ± 8.0 μg m−3) between 1998 and 2011. Meteo-synoptical analysis allowed to ascribe this event to a long lasting and highly coherent Saharan dust outbreak, starting at the beginning of March. The peculiar synoptic configuration causing this massive transport of dust was characterized by a steep gradient between an upper level trough extending to low latitudes with a minimum centred over the North-Western Algerian coast and a Saharan high extending all over the Mediterranean Sea with an elongated north-eastward tongue, whose synergic effect led to a peculiar funnel-shaped dust plume. During the period Mt. Cimone was located exactly along its main axis. The event was first analysed in association with simultaneous more or less conventional compositional parameters such as 7Be, 210Pb, and ozone. Subsequently, it was characterized in details both in terms of time and space evolution. The former aspect was investigated using number densities of fine and coarse particles obtained through an Optical Particle Counter which allowed to follow the event evolution at the sub-daily time scale while PM10 membrane gravimetric analysis was limited by the 48-h sampling schedule suggesting the value of 80 μg m−3 recorded is even potentially smoothed down by sampling duration. Besides precise timing, optical counting enabled to detect the inception and development of the event through a steep and simultaneous increase of both coarse and fine particle number densities. Although the former increase was much more relevant, the latter occurrence is much less frequently documented for Saharan Dust events: a clear increase of particles in all the diameter ranges from 0.3 μm (lower limit of an OPC) up to 5.0 μm was observed during the event. The spatial extension of the event was also examined by means of the analysis of the AERONET ground-based sun photometer data from the Venice station for the event. Results confirmed a relevant increase of coarse particles over a distance of more than 150 km. Interestingly AERONET data indicates a more significant variation in the scattering properties of the aerosol rather than in the absorbing ones in connection with the arrival of the Saharan dust, an observation that within the intrinsic limitations of inverse methods to derive aerosol's optical properties is in agreement with some previous observations showing that dust in the Saharan desert region is much less absorbing than previously measured.

Ms. Ref. No.: JENVRAD-D-11-00380R2 The follow-up of Fukushima radioactive plume resulting from the 11th March 2011 devastating tsunami is discussed for two Italian stations in the northern Apennines: Mt. Cimone (Modena) and Montecuccolino (Bologna). Radioactivity data collected at both stations are described, including comparison between local natural background of airborne particulate and artificial radioactivity referable to the arrival of the radioactive plume and its persistence and evolution. Analysis of back-trajectories was used to confirm the arrival of artificial radionuclides following atmospheric transport and processing. The Fukushima plume was first detected on 3rd April 2011 when high volume sampling revealed the presence of the artificial radionuclides 131I, 137Cs and 134Cs. The highest activity concentrations of these nuclides were detected on 5th April 2011 at the Montecuccolino site. Fukushima radioactivity data at the two stations were usually comparable, suggesting a good vertical mixing of the plume; discrepancies were occasional and attributed to different occurrence of wet removal, typically characterized by a scattered spatial pattern. To understand the relevance to the local population of the extra dose due to the Fukushima plume, atmospheric activities of the related artificial nuclides were compared to those of the main natural radionuclides in ambient particulate, and found to be lower by over one order of magnitude. Radiation doses referable to Fukushima, maximized for a whole year occurrence at the highest activity level observed at our stations in the weeks affected by the Japanese plume, were estimated at 1.1 μSv/year.

none 13 si The Fukushima-labeled air mass arrival, and later the cesium-134 (134Cs), cesium-137 (137Cs) and particulate iodine-131 (hereafter noted 131Ip) maximum levels were registered in Europe at different dates depending on the location. Most of those data were obtained at low-altitude sampling areas. Here, we compare the airborne levels registered at different high-altitude European locations (from 850 m to about 3500 m). The integrated 137Cs activity concentration was not uniform with regard to the altitude even after a long travel time/distance from Japan. Moreover, the relation of integrated 137Cs vs. altitude showed a linear decrease up to an altitude of about 3000 m. A similar trend was noticed for 131Ip (particulate fraction) while it increased above 3000 m. Comparison with 7Be activity concentration showed that, as far as the high altitude location is concerned, the 137Cs and 134Cs maximum concentrations corresponded to the 7Be maximum, suggesting downdraft movements from high tropospheric or stratospheric layers to be responsible for 137,134Cs increase and peak values. This was also confirmed by high potential vorticity and low relative humidity registered during the peak values. Masson, Olivier; Bieringer, Jacqueline; Brattich, Erika; Dalheimer, Axel; Estier, Sybille; Penev, Ilia; Ringer, Wolfgang; Schlosser, Clemens; Steinkopff, Thomas; Steinmann, Philipp; Tositti, Laura; Beek, Pieter Van; Vismes-Ott, Anne de Masson, Olivier; Bieringer, Jacqueline; Brattich, Erika; Dalheimer, Axel; Estier, Sybille; Penev, Ilia; Ringer, Wolfgang; Schlosser, Clemens; Steinkopff, Thomas; Steinmann, Philipp; Tositti, Laura; Beek, Pieter Van; Vismes-Ott, Anne de

We apply the Global Modeling Initiative (GMI) chemistry and transport model driven by the NASA’s MERRA assimilated meteorological data to simulate the seasonal variations of two radionuclide aerosol tracers (terrigenous 210Pb and cosmogenic 7Be) at the WMO-GAW station of Mt. Cimone (44°12’ N, 10°42’ E, 2165 m a.s.l., Italy), which is representative of free-tropospheric conditions most of the year, during 2005 with an aim to understand the roles of transport and precipitation scavenging processes in controlling their seasonality. The total precipitation field in the MERRA data set is evaluated with the Global Precipitation Climatology project (GPCP) observations, and a generally good agreement is found. The model reproduces reasonably the observed seasonal pattern of 210Pb concentrations, characterized by a wintertime minimum due to lower 222Rn emissions and weaker uplift from the boundary layer and summertime maxima resulting from strong convection over the continent. The observed seasonal behavior of 7Be concentrations shows a winter minimum, a summer maximum, and a secondary spring maximum. The model captures the observed 7Be pattern in winter-spring, which is linked to the larger stratospheric influence during spring. However, the model tends to underestimate the observed 7Be concentrations in summer, partially due to the sensitivity to spatial sampling in the model. Model sensitivity experiments indicate a dominant role of precipitation scavenging (versus dry deposition and convection) in controlling the seasonality of 210Pb and 7Be concentrations at Mt. Cimone.