Carbonaceous aerosols represent a significant component of atmospheric aerosol, with implications for climate and human health. The recent EU Directive 2024/2881 highlights the need to monitor emerging pollutants like black carbon more effectively. This study presents an brief field campaign at an urban background site aimed at characterizing carbonaceous aerosols. Daily samples of PM10 and PM2.5 were analyzed using a Sunset thermal-optical analyzer to determine organic and elemental carbon (OC, EC), while real-time equivalent black carbon (eBC) was measured with three independent instruments: MAAP, AE33, and Giano BC1. Total carbon (TC) was monitored using an online TCA08 thermo-catalytic analyzer. The average concentration of PM10 was 17.1 µg/m3 and 10.4 µg/m3 for PM2.5. On average, OC and EC represented 16.5% and 3.6% of PM10 mass, and 22.6% and 5.5% of PM2.5. SOC accounted for 36% of OC. The in situ Mass Absorption Cross-section (MAC), recalculated for the ECO site, was between 8.0 and 12.2 m2/g. eBC concentrations were modulated by the daily evolution of the planetary boundary-layer height and combustion sources. The apportionment of eBC was 65% from fossil fuel and 35% from biomass burning. Biomass-burning emissions were further confirmed by optical measurements, with BrC contributing 35% of absorption at 370 nm.

Oxidative potential (OP) is a potential indicator of negative health effects of particulate matter (PM). To address mitigation strategies, there is need of understanding how natural and anthropogenic sources influence OP at different sites. This work investigates spatial and seasonal variabilities of PM2.5 and PM10 concentrations, composition, and oxidative potential (OPDTTV, obtained with DTT assay), simultaneously at 22 sites in a central Mediterranean area in south Italy. Source apportionment using PMF5 allowed to evaluate the contributions of eight sources: traffic, biomass burning (BB), nitrate, sulphate-rich, marine, crustal, carbonates/construction, and industrial (only for PM2.5). Nitrate, traffic, and BB had larger contributions during the cold season and presented spatial variability with exclusion of nitrate. Industrial contributions did not have relevant seasonal or spatial variability. The other sources had an opposite trend with larger values during the warm season but only sulphate-rich had non-negligible spatial variability. OPDTTV had relevant spatial variability only during the cold season. Four sources had statistically significant contributions to OPDTTV: traffic, BB, sulphate-rich, and crustal (in descending order). The use of soluble and insoluble fractions of OC and Ca in PMF5 allowed a better separation between traffic and BB sources and allowed to determine the role of local construction works. The results may have implications in future policies for mitigation strategies of OP targeting specific sources categories.

Atmospheric particulate matter (PM) is one of the major risks for global health. The exact mechanisms of toxicity are still not completely understood leading to contrasting results when different toxicity metrics are compared. In this work, PM10 was collected at three sites for the determination of acellular oxidative potential (OP), intracellular oxidative stress (OSGC), cytotoxicity (MTT assay), and genotoxicity (Comet assay). The in vitro tests were done on the A549 cell line. The objective was to investigate the correlations among acellular and intracellular toxicity indicators, the variability among the sites, and how these correlations were influenced by the main sources by using PMF receptor model coupled with MLR. The OPDTTV, OSGCV, and cytotoxicity were strongly influenced by combustion sources. Advection of African dust led to lower-than-average intrinsic toxicity indicators. OPDTTV and OSGCV showed site-dependent correlations suggesting that acellular OP may not be fully representative of the intracellular oxidative stress at all sites and conditions. Cytotoxicity correlated with both OPDTTV and OSGCV at two sites out of three and the strength of the correlation was larger with OSGCV. Genotoxicity was correlated with cytotoxicity at all sites and correlated with both, OPDTTV and OSGCV, at two sites out of three. Results suggest that several toxicity indicators are useful to gain a global picture of the potential health effects of PM.

Exposure to atmospheric particulate matter (PM) is recognized as a human health risk factor of great concern. The present work aimed to study the cellular mechanisms underlying cytotoxic effects of airborne particulate matter <10 µm in size (PM10), sampled in an urban background site from January to May 2020, on A549 cells. In particular, the study addressed if PM10 exposure can be a main factor in the induction of the Apoptotic Volume Decrease (AVD), which is one of the first events of apoptosis, and if the generation of intracellular oxidative stress can be involved in the PM10 induction of apoptosis in A549 cells. The cytotoxicity of PM10 samples was measured by MTT test on cells exposed for 24 h to the PM10 aqueous extracts, cell volume changes were monitored by morphometric analysis of the cells, apoptosis appearance was detected by annexin V and the induction of intracellular oxidative stress was evaluated by the ROS sensitive CM-H2DCFDA fluorescent probe. The results showed cytotoxic effects ascribable to apoptotic death in A549 cells exposed for 24 h to aqueous extracts of airborne winter PM10 samples characterized by high PM10 value and organic carbon content. The detected reduced cell viability in winter samples ranged from 55% to 100%. Normotonic cell volume reduction (ranging from about 60% to 30% cell volume decrease) after PM10 exposure was already detectable after the first 30 min clearly indicating the ability of PM10, mainly arising from biomass burning, to induce Apoptotic Volume Decrease (AVD) in A549 cells. AVD was prevented by the pre-treatment with 0.5 mM SITS indicating the activation of Cl− efflux presumably through the activation of VRAC channels. The exposure of A549 cells to PM10 aqueous extracts was able to induce intracellular oxidative stress detected by using the ROS-sensitive probe CM-H2DCFDA. The PM10-induced oxidative stress was statistically significantly correlated with cell viability inhibition and with apoptotic cell shrinkage. It was already evident after 15 min exposure representing one of the first cellular effects caused by PM exposure. This result suggests the role of oxidative stress in the PM10 induction of AVD as one of the first steps in cytotoxicity.

Many countries imposed lockdown (LD) to limit the spread of COVID-19, which led to a reduction in the emission of anthropogenic atmospheric pollutants. Several studies have investigated the effects of LD on air quality, mostly in urban settings and criteria pollutants. However, less information is available on background sites, and virtually no information is available on particle number size distribution (PNSD). This study investigated the effect of LD on air quality at an urban background site representing a near coast area in the central Mediterranean. The analysis focused on equivalent black carbon (eBC), particle mass concentrations in different size fractions: PM2.5 (aerodynamic diameter Da < 2.5 mu m), PM10 (Da < 10 mu m), PM10-2.5 (2.5 < Da < 10 mu m); and PNSD in a wide range of diameters (0.01-10 mu m). Measurements in 2020 during the national LD in Italy and period immediately after LD (POST-LD period) were compared with those in the corresponding periods from 2015 to 2019. The results showed that LD reduced the frequency and intensity of high-pollution events. Reductions were more relevant during POST-LD than during LD period for all variables, except quasi-ultrafine particles and PM10-2.5. Two events of long-range transport of dust were observed, which need to be identified and removed to determine the effect of LD. The decreases in the quasi-ultrafine particles and eBC concentrations were 20%, and 15-22%, respectively. PM2.5 concentration was reduced by 13-44% whereas PM10-2.5 concentration was unaffected. The concentration of accumulation mode particles followed the behaviour of PM2.5, with

Although cities are an important source of aerosol particles, aerosol number flux measurements over urban areas are scarce. These measurements are however important as they can allow us to identify the different sources/sinks of aerosol particles and quantify their emission contributions. Therefore, they can help us to understand the aerosol impacts on human health and climate, and to design effective mitigation strategies through the reduction of urban aerosol emissions. In this work we analyze the aerosol number concentrations and fluxes for particles with diameters larger than 2.5 nm measured by eddy covariance technique at an urban area (Granada city, Spain) from November 2016 to April 2018. This is the first study of particle number flux in an urban area in the Iberian Peninsula and is one of the few current studies that report long-term aerosol number flux measurements. The results suggest that, on average, Granada urban area acted as a net source for atmospheric aerosol particles with median particle number flux of 150 x 10(6) m(-2) s(-1). Downward negative fluxes were observed in only 12% of the analyzed data, and most of them were observed during high aerosol load conditions. Both aerosol number fluxes and concentrations were maximum in winter and 50% larger than those measured in summer due to the increased emissions from domestic heating, burning of residual agricultural waste in the agricultural area surrounding the site, as well as to the lower aerosol dilution effects during winter. The analysis of the seasonal diurnal variability of the aerosol number concentration revealed the significant impact of traffic emissions on aerosol population over Granada urban area in all seasons. It also shows the impact of domestic heating and agricultural waste burning emissions in winter as well as the influence of new particle formation processes in summer and spring seasons. Closer analysis by wind sector demonstrated that both aerosol concentrations and fluxes from urban sector (where high density of anthropogenic sources is located) were lower than those from rural sector (which includes agricultural area but also the main highway of the city). This evidences the strong impact of aerosol emissions from traffic circulating on the highway on aerosol population over our measurement site.

Airborne transmission of SARS-CoV-2 has been object of debate in the scientific community since the beginning of COVID-19 pandemic. This mechanism of transmission could arise from virus-laden aerosol released by infected individuals and it is influenced by several factors. Among these, the concentration and size distribution of virus-laden particles play an important role. The knowledge regarding aerosol transmission increases as new evidence is collected in different studies, even if it is not yet available a standard protocol regarding air sampling and analysis, which can create difficulties in the interpretation and application of results. This work reports a systematic review of current knowledge gained by 73 published papers on experimental determination of SARS-CoV-2 RNA in air comparing different environments: outdoors, indoor hospitals and healthcare settings, and public community indoors. Selected papers furnished 77 datasets: outdoor studies (9/77, 11.7%) and indoor studies (68/77. 88.3%). The indoor datasets in hospitals were the vast majority (58/68, 85.3%), and the remaining (10/68, 14.7%) were classified as community indoors. The fraction of studies having positive samples, as well as positivity rates (i.e. ratios between positive and total samples) are significantly larger in hospitals compared to the other typologies of sites. Contamination of surfaces was more frequent (in indoor datasets) compared to contamination of air samples; however, the average positivity rate was lower compared to that of air. Concentrations of SARS-CoV-2 RNA in air were highly variables and, on average, lower in outdoors compared to indoors. Among indoors, concentrations in community indoors appear to be lower than those in hospitals and healthcare settings.

The work deals with identification/quantification of genetic material (RNA) of SARS-CoV-2 in air in different locations in Italy. This is an extremely important aspect to investigate the risks of airborne transmission and the role of this mechanism of transmission on the development of pandemic.

The aim of this work was characterization of airborne particulates in the port city of Rijeka in order to evaluate impact of ship emissions on air quality. Samples of airborne particulates were collected with a ten stages cascade impactor during two campaigns: autumn and spring. A total of 16 weekly samples were analyzed on mass concentration, ions, metals and carbonaceous species (EC, OC, WSOC). Distribution of airborne fractions showed a bimodal distribution, with two maxima: one in coarse, and other in fine fraction. Source apportionment using PMF receptor model identified six sources of airborne particulates in Rijeka: crustal, biomass burning, sea salt, traffic/metal industry, combustion/SIA and HFO burning, i.e., ship emission (contribution 3%). The contribution of ship traffic to primary emission of particulate matter, using vanadium as tracer, indicated a twofold increase for PM10 and PM2.5 relative to 2012?14. An unusual desert dust event was registered in autumn campaign.

COVID-19 pandemic raised a debate regarding the role of airborne transmission. Information regarding virus-laden aerosol concentrations is still scarce in community indoors and what are the risks for general public and the efficiency of restriction policies. This work investigates, for the first time in Italy, the presence of SARS-CoV-2 RNA in air samples collected in different community indoors (one train station, two food markets, one canteen, one shopping centre, one hair salon, and one pharmacy) in three Italian cities: metropolitan city of Venice (NE of Italy), Bologna (central Italy), and Lecce (SE of Italy). Air samples were collected during the maximum spread of the second wave of pandemic in Italy (November and December 2020). All collected samples tested negative for the presence of SARS-CoV-2, using both real-time RT-PCR and ddPCR, and no significant differences were observed comparing samples taken with and without customers. Modelling average concentrations, using influx of customers' data and local epidemiological information, indicated low values (i.e. < 0.8 copies m-3 when cotton facemasks are used and even lower for surgical facemasks). The results, even if with some limitations, suggest that the restrictive policies enforced could effectively reduce the risk of airborne transmissions in the community indoor investigated, providing that physical distance is respected.

A source apportionment study was performed on PM10 samples collected in four sites nearby the largest Italian coal-fired power plant (SE Italy). A multi-model approach, based on integration of receptor (Positive Matrix Factorization - PMF, Chemical Mass Balance - CMB) and dispersion (CALPUFF) models, estimated the contribution of the power plant to primary PM10 and to secondary ammonium sulphate. Maximum PM10 daily concentrations were observed at all sites during winter period, with exceedances of the daily legislation threshold mainly due to biomass burning and road traffic. Chemical analysis explained about 55% of PM10 in the Brindisi area, 62% in the Lecce area. Eight PM sources were identified: crustal and power plant, resuspended dust, traffic, secondary ammonium sulphate, secondary nitrate, marine, biomass burning and harbour – industrial, with a reasonable comparability between receptor models outputs. Combining the information from receptor and dispersion models, the average contribution of the power plant to primary PM10 was 2% (±1%) of PM10 for Lecce site and 3% (±1%) as average of the three sites of Brindisi province. The contribution to secondary ammonium sulphate was ranging between 1.3% (±0.3%) of PM10 and 1.7% (±0.4%). These results were compared with those obtained using the same approach in the area close to Torrevaldaliga Nord (TVN) coal-fired power plant. Results indicate a lower primary contribution to PM10 of the TVN station, likely associated to lower PM emissions at the stack of TVN station and different heights of release, comparable contributions to secondary ammonium sulphate founded.

The COVID-19 disease spread at different rates in the different countries and in different regions of the same country, as happened in Italy. Transmission by contact or at close range due to large respiratory droplets is widely accepted, however, the role of airborne transmission due to small respiratory droplets emitted by infected individuals (also asymptomatic) is controversial. It was suggested that outdoor airborne transmission could play a role in determining the differences observed in the spread rate. Concentrations of virus-laden aerosol are still poorly known and contrasting results are reported, especially for outdoor environments. Here we investigated outdoor concentrations and size distributions of virus-laden aerosol simultaneously collected during the pandemic, in May 2020, in northern (Veneto) and southern (Apulia) regions of Italy. The two regions exhibited significantly different prevalence of COVID-19. Genetic material of SARS-CoV-2 (RNA) was determined, using both real time RT-PCR and ddPCR, in air samples collected using PM10 samplers and cascade impactors able to separate 12 size ranges from nanoparticles (diameter D < 0.056 µm) up to coarse particles (D > 18 µm). Air samples tested negative for the presence of SARS-CoV-2 at both sites, viral particles concentrations were <0.8 copies m−3 in PM10 and <0.4 copies m−3 in each size range investigated. Outdoor air in residential and urban areas was generally not infectious and safe for the public in both northern and southern Italy, with the possible exclusion of very crowded sites. Therefore, it is likely that outdoor airborne transmission does not explain the difference in the spread of COVID-19 observed in the two Italian regions.

Diesel exhaust is hazardous to human health. In time, this has led the EU to impose on manufacturers lower and lower emission standards. These limits are very challenging in particular for nitrogen oxides (NOx) emitted by diesel-fueled vehicles. For the town of Milan (Italy), we used a complex modeling system that takes into account the NOx emissions from vehicular traffic and other urban sources, as well as their dispersion and chemical transformations in the atmosphere related to meteorological parameters. The traffic emissions in the Milan urban area were estimated using the geometric and structural characteristics of the road network, whereas the traffic flows were provided by the Environment and Territory Mobility Agency. Car emissions were estimated by the official European method COPERT 5. The nitrogen dioxide (NO2) concentrations were estimated under two scenarios: the actual scenario with real emissions and the Diesel Emission Standards Compliance (DESC) scenario. Using a recent meta-analysis, limited to European studies, we evaluated the relationship between NO2 concentrations and natural mortality. For the actual scenario, the NO2 annual concentration mean was 44.3 µg/m3, whereas under the DESC hypothetical scenario, this would have been of 37.7 µg/m3. This “extra” exposure of 6.6 µg/m3 of NO2 leads to a yearly excess of 574 “natural” deaths. Diesel emissions are very difficult to limit and are harmful for exposed people. This suggests that specific policies, including traffic limitations, need to be developed and enforced in urban environments.

Long and short-term exposure to atmospheric particulate matter (PM) has detrimental effects on human health. The effective mechanisms leading to PM toxicity are still not fully understood, even if it is known that physical-chemical properties, strongly influenced by sources and atmospheric processes, are known to play an important role. In this work, PM10 samples were collected, at an urban background site in southern Italy, to determine cytotoxicity (using MTT test on A549 cells), genotoxicity (using the comet assay), and intracellular oxidative stress on A549 cells exposed for 24 h to aqueous extracts of PM10 samples. Organic carbon (OC) and elemental carbon (EC) content of PM10 and acellular determination of oxidative potential with DTT assay were performed to compare results of acellular and cellular biological assays. Cellular (OSGCV and MTTV) and acellular (OPDTTV) outcomes, normalized in volume, are well correlated (statistically significant results) with carbon content suggesting that combustion sources play an important role in determining cellular oxidative stress and cytotoxicity of PM10. Even if the number of data is limited, genotoxicity results are well correlated (Pearson r > 0.95) with OSGCV and MTTV, and a weaker, but statistically significant correlation was observed with OPDTTV. OSGCV is well correlated with the cell mortality observed with the MTTV test and a lower, but still statistically significant correlation is observed between MTTV and OPDDTV. A statistically significant correlation was found between OPDTTV and OSGCV results. When the outcomes of the cellular and acellular assay are compared normalized in mass (i.e., intrinsic values), the correlations become significantly weaker suggesting that the different sources acting on the site produces particulate matter with different toxicological potential influencing differently the biological tests studied.

The spread of SARS-CoV-2 by contact (direct or indirect) is widely accepted, but the relative importance of airborne transmission is still controversial. Probability of outdoor airborne transmission depends on several parameters, still rather uncertain: virus-laden aerosol concentrations, viability and lifetime, minimum dose necessary to transmit the disease. In this work, an estimate of outdoor concentrations in northern Italy (region Lombardia) was performed using a simple box model approach, based on an estimate of respiratory emissions, with a specific focus for the cities of Milan and Bergamo (Italy). In addition, the probability of interaction of virus-laden aerosol with pre-existing particles of different sizes was investigated. Results indicate very low (<1 RNA copy/m(3)) average outdoor concentrations in public area, excluding crowded zones, even in the worst case scenario and assuming a number of infects up to 25% of population. On average, assuming a number of infects equal to 10% of the population, the time necessary to inspire a quantum (i.e. the dose of airborne droplet nuclei required to cause infection in 63% of susceptible persons) would be 31.5 days in Milan (range 2.7-91 days) and 51.2 days in Bergamo (range 4.4-149 days). Therefore, the probability of airborne transmission due to respiratory aerosol is very low in outdoor conditions, even if it could be more relevant for community indoor environments, in which further studies are necessary to investigate the potential risks. We theoretically examined if atmospheric particles can scavenge virus aerosol, through inertial impact, interception, and Brownian diffusion. The probability was very low. In addition, the probability of coagulation of virus-laden aerosol with pre-existing atmospheric particles resulted negligible for accumulation and coarse mode particles, but virus-laden aerosol could act as sink of ultrafine particles (around 0.01 mu m in diameter). However, this will not change significantly the dynamics behaviour of the virus particle or its permanence time in atmosphere.

Shipping contributions to atmospheric particulate matter were estimated by an approach based on high temporal resolution measurements of mass and number size distribution, correlated with meteorological and ship movements data, in two Adriatic harbours. Trends of contributions are discussed. Contribution to particle number concentrations (PNC) was 3–4 times larger than that to PM2.5. In Venice, strategies for reduction of shipping emissions were effective in lowering the PM2.5 primary impact, while PNC contribution was significant in Brindisi. The maximum contribution was found to ultrafine particles (UFP), followed by a minimum at diameters between 1 and 1.5 µm and a growth in the coarse range.

• Chemical characterisation of aerosol was performed in 12 size ranges. • Source apportionment of Venice size-segregated aerosol was carried out. • Impact of ship traffic was studied for the first time on particles below 1 μm. • Impact of ship traffic is higher in nanoparticles compared to larger particles.

Continuous measurements of particle number size distributions in the size range from 10 nm to 800 nm were performed from 2015 to 2019 at the ECO Environmental-Climate Observatory of Lecce (Global Atmosphere Watch Programme/Aerosol, Clouds and Trace Gases Research Infrastructure (GAW/ACTRIS) regional station). The main objectives of this work were to investigate the daily, weekly and seasonal trends of particle number concentrations and their dependence on meteorological parameters gathering information on potential sources. The highest total number concentrations were observed during autumn-winter with average values nearly twice as high as in summer. More than 52% of total particle number concentration consisted of Aitken mode (20 nm < particle diameter (Dp) < 100 nm) particles followed by accumulation (100 nm < Dp < 800 nm) and nucleation (10 nm < Dp < 20 nm) modes representing, respectively, 27% and 21% of particles. The total number concentration was usually significantly higher during workdays than during weekends/holidays in all years, showing a trend likely correlated with local traffic activities. The number concentration of each particle mode showed a characteristic daily variation that was different in cold and warm seasons. The highest concentrations of the Aitken and accumulation particle mode were observed in the morning and the late evening, during typical rush hour traffic times, highlighting that the two-particle size ranges are related, although there was significant variation in the number concentrations. The peak in the number concentrations of the nucleation mode observed in the midday of spring and summer can be attributed to the intensive formation of new particles from gaseous precursors. Based on Pearson coefficients between particle number concentrations and meteorological parameters, temperature, and wind speed had significant negative relationships with the Aitken and accumulation particle number concentrations, whereas relative humidity was positively correlated. No significant correlations were found for the nucleation particle number concentrations.

Detailed information on in-harbour shipping contribution to size segregated particles in coastal cities are scarce, especially in the busy Mediterranean basin. This poses issues for human exposure and air quality in urban harbour agglomerates, where only criteria pollutants (i.e. PM10 and/or PM2.5) are usually monitored. In this work, particle number and mass size distributions, in a large size range (0.01-31 μm), were obtained in two coastal cities of northern Adriatic Sea: Venice (Italy) and Rijeka (Croatia). Three size ranges were investigated: nanoparticles (diameter D < 0.25 μm); fine particles (0.25 1 μm). Absolute concentrations were larger in Venice for all size ranges showing, using analysis of daily trends, a large influence of local meteorology and boundary-layer dynamics. Contribution of road transport was larger (in relative terms) in Rijeka compared to Venice. The highest contributions of shipping were in Venice, mainly because of the larger ship traffic. Maximum impact was on nanoparticles 7.4% (Venice) and 1.8% (Rijeka), the minimum was on fine range 1.9% (Venice) and <0.2% (Rijeka) and intermediate values were found in the coarse fraction 1.8% (Venice) and 0.5% (Rijeka). Contribution of shipping to mass concentration was not distinguishable from uncertainty in Rijeka (<0.2% for PM1, PM2.5, and PM10) and was about 2% in Venice. Relative contributions as function of particles size show remarkable similitudes: a maximum for nanoparticles, a quick decrease and a successive secondary maximum (2-3 times lower than the first) in the fine range. For larger diameters, the relative contributions reach a minimum at 1-1.5 μm and there is a successive increase in the coarse range. Size distributions showed a not negligible contribution of harbour emissions to nanoparticle and fine particle number concentrations, compared to PM2.5 or PM10, indicating them as a better metric to monitor shipping impacts compared to mass concentrations (PM2.5 or PM10).

Observations of turbulent aerosol fluxes are fundamental to understand basic transport processes that govern changes of particle concentrations in the atmospheric boundary layer. The turbulent surface-atmosphere exchange of atmospheric particles can be quantified using several methods, including the eddy-covariance (EC) method and spectral flux estimation methods such as wavelet analysis and multiresolution decomposition. In this work, turbulent time series obtained by EC measurements in two different cities, Lecce (Italy) and Innsbruck (Austria), are spectrally analysed applying wavelet analysis and multiresolution decomposition, and the respective turbulent spectra are compared in these two European cities to quantify the contributions to turbulent fluxes in both the time and the frequency domains. As expected, particle emission is dominant in both cities following a similar diurnal cycle. Multiresolution decomposition reveals a similar cospectral peak of particle fluxes in both cities, with a median normalized frequency of n = 0.087 in Lecce and n = 0.086 in Innsbruck. Wavelet analysis shows that the 2-20 s time scales contribute very strongly to the particle flux in Lecce, while in Innsbruck the 20-200 s time scales are clearly dominant. In both cities, larger-sized eddies contribute only sporadically to turbulent aerosol fluxes. These results suggest that spectral similarity of urban particle number fluxes holds, to a large extent, even when comparing two very different urban environments and different meteorological conditions.