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Light-absorbing aerosols (LAA) impact the atmosphere by heating it. Their effect in the Arctic was investigated during two summer Arctic oceanographic campaigns (2018 and 2019) around the Svalbard Archipelago in order to unravel the differences between the Arctic background and the local anthropic settlements. Therefore, the LAA heating rate (HR) was experimentally determined. Both the chemical composition and high-resolution measurements highlighted substantial differences between the Arctic Ocean background (average eBC concentration of 11.7 ± 0.1 ng/m3) and the human settlements, among which the most impacting appeared to be Tromsø and Isfjorden (mean eBC of 99.4 ± 3.1 ng/m3). Consequently, the HR in Isfjorden (8.2 × 10−3 ± 0.3 × 10−3 K/day) was one order of magnitude higher than in the pristine background conditions (0.8 × 10−3 ± 0.9 × 10−5 K/day). Therefore, we conclude that the direct climate impact of local LAA sources on the Arctic atmosphere is not negligible and may rise in the future due to ice retreat and enhanced marine traffic.

La tesi esplora le correlazioni fra composizione chimica del particolato emesso in frenata e alcuni fattori quali: i) le combinazioni di materiali che compongono l'interfaccia tribologica; ii) le condizioni di guida; iii) le frazioni dimensionali in cui vengono prodotti i particolati, This thesis reports on the correlations between the compositional features of the particulates produced by brakes and several determining or modulating factors, such as: i) The starting material composing the friction couple; ii) the driving conditions; and iii) the dimensional fractions in which the particulates are generated and emitted.

Biomass burning related aerosol episodes are becoming a serious threat to the radiative balance of the Arctic region. Since early July 2017 intense wildfires were recorded between August and September in Canada and Greenland, covering an area up to 4674 km2 in size. This paper describes the impact of these biomass burning (BB) events measured over Svalbard, using an ensemble of ground-based, columnar, and vertically-resolved techniques. BB influenced the aerosol chemistry via nitrates and oxalates, which exhibited an increase in their concentrations in all of size fractions, indicating the BB origin of particles. The absorption coefficient data (530 nm) at ground reached values up to 0.6 Mm-1, highlighting the impact of these BB events when compared to average Arctic background values, which do not exceed 0.05 Mm-1. The absorption behavior is fundamental as implies a subsequent atmospheric heating. At the same time, the AERONET Aerosol Optical Depth (AOD) data showed high values at stations located close to or in Canada (AOD over 2.0). Similarly, increased values of AODs were then observed in Svalbard, e.g., in Hornsund (daily average AODs exceeded 0.14 and reached hourly values up to 0.5). Elevated values of AODs were then registered in Sodankyla and Andenes (daily average AODs exceeding 0.150) a few days after the Svalbard observation of the event highlighting the BB columnar magnitude, which is crucial for the radiative impact. All the reported data suggest to rank the summer 2017 plume of aerosols as one of the biggest atmosphere related environmental problems over Svalbard region in last 10 years.

Biomass burning related aerosol episodes are becoming a serious threat to the radiative balance of the Arctic region. Since early July 2017 intense wildfires were recorded between August and September in Canada and Greenland, covering an area up to 4674 km2 in size. This paper describes the impact of these biomass burning (BB) events measured over Svalbard, using an ensemble of ground-based, columnar, and vertically-resolved techniques. BB influenced the aerosol chemistry via nitrates and oxalates, which exhibited an increase in their concentrations in all of size fractions, indicating the BB origin of particles. The absorption coefficient data (530 nm) at ground reached values up to 0.6 Mm–1, highlighting the impact of these BB events when compared to average Arctic background values, which do not exceed 0.05 Mm–1. The absorption behavior is fundamental as implies a subsequent atmospheric heating. At the same time, the AERONET Aerosol Optical Depth (AOD) data showed high values at stations located close to or in Canada (AOD over 2.0). Similarly, increased values of AODs were then observed in Svalbard, e.g., in Hornsund (daily average AODs exceeded 0.14 and reached hourly values up to 0.5). Elevated values of AODs were then registered in Sodankylä and Andenes (daily average AODs exceeding 0.150) a few days after the Svalbard observation of the event highlighting the BB columnar magnitude, which is crucial for the radiative impact. All the reported data suggest to rank the summer 2017 plume of aerosols as one of the biggest atmosphere related environmental problems over Svalbard region in last 10 years

Questo studio si focalizza sulla concentrazione e sul comportamento di composti organici in atmosfera nella Regione Lombardia, un'area critica per l'inquinamento atmosferico, e nel Mare del Nord. L'attenzione sarà incentrata su composti potenzialmente tossici per la salute umana (come gli idrocarburi policiclici aromatici - IPA) e composti che possono fornire informazioni sulle sorgenti di emissione (come gli alcani). La corretta identificazione delle sorgenti dell’inquinamento consente di progettare strategie di abbattimento adeguate per migliorare la qualità dell'aria. I campioni, sia in fase particolata che in fase gassosa, raccolti a Milano sono stati analizzati per studiare la ripartizione di fase di IPA semi-volatili e di alcani lineari in diverse stagioni. Poiché una delle fonti più importanti del particolato in Lombardia durante tutto l'anno è costituita dalle emissioni autoveicolari, è stato effettuato un confronto tra le concentrazioni e la composizione chimica del particolato raccolto a Milano, in due siti con carichi di traffico diversi, al fine di valutare l'effetto della zona a traffico limitato (ZTL). Oltre alle emissioni autoveicolari, le emissioni relative alle attività aeroportuali hanno destato grande interesse negli ultimi anni; l'aviazione civile è, infatti, uno dei settori in più rapida crescita dell'economia globale. In Lombardia si trova l'aeroporto internazionale di Milano-Malpensa che rappresenta il principale aeroporto del nord Italia e il secondo aeroporto italiano per traffico passeggeri dopo quello di Roma-Fiumicino. All'interno dell'aeroporto è stata realizzata una campagna di campionamento per studiare il contributo delle attività aeroportuali alle emissioni dei principali inquinanti atmosferici e valutare l'impatto di queste attività sui comuni dell'area circostante. L'inquinamento atmosferico, tuttavia, è un problema che non riguarda solo i siti urbani; gli inquinanti possono, infatti, essere trasportati su lunghe dista, This study is focused on the atmospheric concentration and the behavior of specific organic compounds in the Lombardy Region, a critical area for atmospheric pollution, and in the North Sea. The attention will be focused on compounds that are potentially toxic for human health (such as Polycyclic Aromatic Hydrocarbons- PAHs) and that can give information on their emission source (such as alkanes). The correct identification of the anthropogenic pollutant sources would allow to design suitable abatement strategies to improve the air quality. Samples of atmospheric particulate and gaseous phases collected in Milan were analyzed to study the atmospheric gas/particle partitioning of semi-volatile PAHs and n-alkanes in different seasons. Since one of the most important source of the particulate matter in Lombardy Region during all the year is vehicle exhausts, a comparison between the concentrations and the chemical composition of particulate matter collected in Milan, at two sites with different traffic loads, was performed for the purpose of evaluating the effect of the Low Emission Zone. In addition to car exhausts, emissions related to airport activities aroused great interest in recent years since civil aviation is one of the fastest-growing sectors of the global economy. In the Lombardy region is located the international airport of Milan-Malpensa that represents the main airport of northern Italy and the second Italian airport for passenger traffic after that of Rome-Fiumicino. A sampling campaign was performed inside the airport, in order to study the contribution of airport activities to the emissions of the main atmospheric pollutants and to assess the impact of these activities on the surrounding area. Air pollution, however, is a problem not only for urban sites; pollutants can, in fact, be transported over long distances and thus contribute to the air pollution of remote sites. The study of atmospheric pollutants in remote sites can provide information on th

Light absorbing aerosols (LAA) absorb sunlight and heat the atmosphere. This work presents a novel methodology to experimentally quantify the heating rate (HR) induced by LAA into an atmospheric layer. Multiwavelength aerosol absorption measurements were coupled with spectral measurements of the direct, diffuse and surface reflected radiation to obtain highly time-resolved measurements of HR apportioned in the context of LAA species (black carbon, BC; brown carbon, BrC; dust), sources (fossil fuel, FF; biomass burning, BB), and as a function of cloudiness. One year of continuous and time-resolved measurements (5 min) of HR were performed in the Po Valley. We experimentally determined (1) the seasonal behavior of HR (winter 1.83 ± 0.02 K day-1; summer 1.04 ± 0.01 K day-1); (2) the daily cycle of HR (asymmetric, with higher values in the morning than in the afternoon); (3) the HR in different sky conditions (from 1.75 ± 0.03 K day-1 in clear sky to 0.43 ± 0.01 K day-1 in complete overcast); (4) the apportionment to different sources: HRFF (0.74 ± 0.01 K day-1) and HRBB (0.46 ± 0.01 K day-1); and (4) the HR of BrC (HRBrC: 0.15 ± 0.01 K day-1, 12.5 ± 0.6% of the total) and that of BC (HRBC: 1.05 ± 0.02 K day-1; 87.5 ± 0.6% of the total).

We present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC) concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard). The campaign lasted 2 years (2011-2012) and resulted in 200 vertical profiles measured by means of a tethered balloon (up to 1200 m a.g.l.) during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground. The collected experimental data allowed a classification of the vertical profiles into different typologies, which allowed us to describe the seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behavior was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude as a function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes to be constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the Arctic summer, affecting the climate.

Il traffico veicolare è considerato una delle principali fonti di inquinamento atmosferico nelle aree urbane, tanto da indurre le autorità competenti a disporre blocchi del traffico. La città di Milano, a partire da gennaio 2012, ha istituito AREA C, un sistema di accesso a pagamento alla zona centrale della città per limitare il numero dei veicoli circolanti nell’area centrale della città e migliorarne la vivibilità. Scopo di questo studio è valutare quale effetto ha avuto l’introduzione della zona a traffico limitato (ZTL) su Idrocarburi Policiclici Aromatici (IPA), Elemental Carbon (EC), alcani lineari ed i principali ioni presenti nel PTS di Milano in e fuori Area C. Il particolato totale sospeso (PTS) utilizzato per questa ricerca è stato campionato in due siti rappresentativi dell’atmosfera urbana milanese, uno interno ad area C (via San Vittore, SV) e uno esterno ad essa (Torre Breda, Università degli studi di Milano-Bicocca, TB ), non si evidenziano differenze nelle concentrazioni. L’EC è utilizzato come marker primario della sorgente traffico. I risultati ottenuti mostrano una netta riduzione dell’EC in ZTL del 36%. Le concentrazioni di IPA nel periodo autunnale sono in media 2,56 ng/m3. I risultati mostrano che esiste una buona correlazione (R2= 0,86) per quanto riguarda la concentrazione degli IPA nei due siti TB e SV, con una diminuzione passando dal sito esterno alla ZTL a quello interno (riduzione media del 25%). Nei due siti, il modello di distribuzione degli IPA è lo stesso. Sono stati monitorati anche gli ossi-IPA, in particolare l’1,9-benz-10-antrone ed il Benzo(a)antracene-7,12- dione. Anche in questo caso si nota una diminuzione delle concentrazioni nel sito SV, all’interno della ZTL, del 19%. Gli alcani lineari sono presenti in concentrazioni che vanno da un minimo di 20 ng/m3 ad un massimo di 70 ng/m3 (somma da C20 a C32). I più abbondanti risultano gli alcani dispari, in particolare il C29, con un’abbondanza pari al 15% rispetto al

We present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC) concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard). The campaign lasted 2 years (2011–2012) and resulted in 200 vertical profiles measured by means of a tethered balloon (up to 1200 m a.g.l.) during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground. The collected experimental data allowed a classification of the vertical profiles into different typologies, which allowed us to describe the seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behavior was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude as a function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes to be constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the Arctic summer, affecting the climate.

During the 2013 Arctic campaign, direct measurements and size-segregated samplings of atmospheric aerosol were carried out from March to September at the Gruvebadet observatory in Ny-Ålesund (78°56′N, 11°56′E; Svalbard Islands). Continuous size distribution measurements (104 size classes) were performed both in the nano- (TSI-SMPS system) and micro-metric (TSI-APS device) range with a resolution of 10 min. Aerosol sampling was carried out on daily basis (PM10 fraction, 00:01–23:59 UTC) and with a 4-day resolution (four-stage cascade impactor). A back-trajectory analysis was performed for specific events to understand transport processes and possible source areas of aerosol reaching Ny-Ålesund. Aerosol samples were analyzed for ion composition (inorganic cations and anions, selected organic anions) by a three-chromatograph system after extraction in ultra-sonic bath. Special attention was spent in identifying and interpreting the seasonal pattern of natural and anthropic chemical markers. Sea spray aerosol was evenly distributed along all the sampling period with maxima related to wind speed. Its size distribution peaks in 1.0–2.5 or 2.5–10 µm, depending on the transport conditions and distance from source areas. Anthropic sulfate dominates the spring aerosol load (Arctic Haze), both in acidic form (H2SO4) and in partially or totally neutralized ammonium salts. Biogenic contributions, marked by methanesulfonic acid, are relatively relevant in late spring–early summer and are distributed in the finest aerosol fraction (<1.0 µm).

The quantification of the hygroscopic properties of atmospheric aerosols is important to understand several processes they are involved in, such as clouds formation, their interaction with solar radiation and the penetration of particles in the human respiratory track. In addition, the interaction of deposited aerosols with surfaces depends on their physical state, too; thus, characterizing their phase transitions as a function of their chemical composition is key to understanding the effects they have on materials (e.g. printed circuits, cultural heritage artifacts). In order to investigate the hygroscopic properties of aerosols, an electrical conductance method in an Aerosol Exposure Chamber was developed for the determination of the phase transitions of PM2.5 aerosol samples during relative humidity cycles. The obtained Deliquescence and Crystallization Relative Humidity (DRH and CRH) were put in relation with the ionic chemical composition of the analyzed samples: it was found that seasonal chemical variations result in seasonal trends for DRH and CRH, too. The implications of these results for Free-Cooled Data Centers, for the understanding of the role of particles in stone-decay processes of cultural heritage artifacts and for the common algorithms used in the remote sensing of particulate matter concentrations were evaluated. The ionic fraction characterisation was also used as an input for a state-of-the-art equilibrium aerosol model (E-AIM) to simulate the DRH of the samples. Some discrepancies were evidenced in the comparison of experimental and modelled values, because the hygroscopic properties of the organic components need to be included too. In order to effectively account for their contribute, current aerosol models need to be refined with accurate hygroscopicity measurements on organic compounds of increasing molecular complexity and their mixtures with common electrolytes. Such measurements are essential for understanding and modelling the microphy

Many properties of atmospheric aerosols, such as optical and chemical behavior, are strictly affected by their ability to adsorb moisture from the atmosphere, i.e. hygroscopicity, and to change their physical phase. Indeed, aerosols deliquesce when a solid-to-liquid phase transition occurs due to an increase in relative humidity (RH) conditions; the opposite process, i.e. crystallization, implies a decrease in RH. Whereas aerosols hygroscopicity is widely studied, the lack of a well-standardized method which allows to characterized the overall behavior of PMx fraction, leaded most of the authors to investigate the phase transitions of simplified aerosol systems, such as pure or simple mixture of compounds, and not real atmospheric aerosols which are extremely complex in chemical composition. Thus, the aim of this work is to describe a new conductance method which allows the identification of the phase transition of atmospheric aerosols sampled as PM2.5 fraction in a urban site (Milan, Po Valley, Italy). In addition, seasonal variability of deliquescence and crystallization relative humidity (DRH and CRH, respectively) is discussed in connection with the variability of chemical composition. The results highlights that atmospheric aerosols show a hysteresis when RH conditions are increased up to DRH and then decreased. In particular, deliquescence occurs at higher RH values in respect of CRH, since crystallization is kinetically-dependent and it occurs at supersaturated conditions. The averaged hysteresis amplitude is found to account about 14% RH and nitrates and sulfates content is found to mainly drive the deliquescence and crystallization conditions. The obtained data are then used to estimate the atmospheric aerosols physical state estimated on the basis of the RH conditions and history in Milan for the 2006-2014 period. Thus, the results are discussed to different applications. Firstly, the implications for energy saving of data centers are shown. Since this cen

The PhD work is focused on the interactions between atmospheric particulate matter (PM) and stone surfaces, particularly with reference to the decay phenomena that can happen as a consequence of PM deposition. Laboratory studies have been focused on the relationship between PM’s chemical composition and the decay hazards to which the stone surfaces subjected to PM deposition are exposed. A new evaluation method has been proposed. The method exploits experimental measurements of deliquescence and crystallization relative humidity (DRH and CRH, which depend on the chemical composition) with the goal to compute hazard indicators for exposed stone substrates, like time of wetness (TOW) and number of dissolution crystallization cycles (Ncy). Experimental measurements of DRH and CRH have been carried out in an Aerosol Exposure Chamber with a conductance method. It has been point out that different decay mechanisms can be potentially active, depending on the season, as a result of a synergic effect between climatic characteristics and chemical composition of PM. In Milan, winter is characterized by high time of wetness (89±11%) and low number of cycles (3±3 cycles/month). Conversely, summer is characterized by low time of wetness (20±13%) and high number of cycles (11±5 cycles/month). Interestingly, spring and fall resulted the most dangerous seasons for outdoor-exposed stones, since they presented both high time of wetness and number of cycles. The field activity has been focused on the set up of a new exposure method, named “deposition box”, which can collect dry PM deposits on different kind of materials. Several sampling campaigns have been performed, some with a seasonal timescale, other over a longer period, in two different exposure sites placed in Milan: Torre Sarca and Villa Necchi Campiglio. A novel method, based on scanning electron microscope images, has been developed to carry out the dimensional characterization of deposed particles. A significant presence of

Daily PM10 aerosol samples were collected at the Gruvebadet observatory, Ny-Ålesund (Svalbard Islands), during the spring-summer 2014 Italian Arctic Campaign. A total of 136 samples were analysed for ion (inorganic anions and cations, selected organic anions) composition aiming to evaluate the seasonal pattern of sulfate, as a key component of the Arctic haze. Ionic balances indicated a strong sulfate seasonality with mean spring concentration about 1.5 times higher than that measured in summer. The spring and summer aerosol was almost neutral, indicating that ammonia was the major neutralizing agent for atmospheric acidic species. The linear regression between sulfate from potential acidic sources (non-sea salt sulfate and non-crustal sulfate) and ammonium indicated that the mean sulfate/ammonium ratio was intermediate between semi-(NH4HSO4) and complete ((NH4)2SO4) neutralization. Using sea-salt sodium as sea-spray marker, non-sea-salt calcium as crustal marker and methanesulfonic acid as biogenic marker, a detailed source apportionment for sulfate was carried out. The anthropogenic input (calculated as the differences between total sulfate and the sum of sea-salt, crustal and biogenic contributes) was found to be the most relevant contribution to the sulfate budget in the Ny-Ålesund aerosol in summer and, especially, in spring. In this last season, crustal, sea-salt, biogenic and anthropogenic sources accounted for 3.3, 12.0, 11.5 and 74.8 %, respectively.

Atmospheric aerosols deliquescence and crystallization relative humidity (DRH and CRH) are rarely measured compared to the worldwide number of hygroscopicity measurements; this feature comes from the lack of an efficient method able to capture the whole complexity of chemical composition of aerosols. Despite this, the knowledge of both DRH and CRH are crucial for a correct parameterization of the aerosol hygroscopic growth used in different applications, among which the remote sensing is very important. In this paper, a newly developed technique (direct current conductance method) was applied in an aerosol chamber to Milan PM2.5 samples, to identify aerosol DRH and CRH both during winter and summer. These results were compared with those independently obtained by gravimetric measurements conducted in the chamber using a microbalance. Microbalance data allowed also the determination of the mass hygroscopic growth factor on the collected PM2.5 samples.Results evidenced first a good agreement between the two methods (RMSE = 2.7% and 2.3% for DRH and CRH, respectively). Collected data evidenced the hysteresis behavior of ambient particles and variability in both DRH and CRH between the two seasons. Summer samples showed higher DRH and CRH (on average 71.4 ± 1.0% RH and 62.6 ± 1.2% RH, respectively) than the winter ones (on average 55.2 ± 0.7% RH and 46.9 ± 0.6% RH). This behavior was related to the higher content of sulfates during the summer season. Conversely, the mass hygroscopic growth factor at 90% RH was higher for winter samples (2.76 ± 0.06) with respect to the summer ones (1.91 ± 0.11).Since hysteresis behavior affects optical properties of aerosols, when RH conditions are within the loop, the hygroscopic growth factor could be assigned in a wrong way. Thus, the growth factor was calculated within the hysteresis loop for both upper and lower branches: results showed that difference in hygroscopic growth factor could reach up the 24%.

Recent epidemiological evidence support the hypothesis that health effects from inhalation of air particles are governed by more than just particle mass, since specific chemical components have been identified as important contributors to mortality and hospitality admissions.We studied the chemical composition and the oxidative potential (OP) of total suspended particle (TSP) samples from Milan at two sites with different traffic loads: a site in the low emission zone (LEZ) and a traffic site (TR) outside. Two a-cellular assays; dithiothreitol (OPDTT) and 2',7' dichlorofluorescin (OPDCFH) were used to characterize the OP of the soluble fraction of particles.TSP samples from LEZ showed significantly lower concentrations of traffic-related chemical components compared to TR. The decrease in the concentrations from TR to LEZ was maximum for EC, with a LEZ/TR ratio of 0.64 (±0.18), and a significant reduction (p < 0.01) was also observed for PAHs (LEZ/TR = 0.73 ± 0.16), elements (Mn, Cu, Zn, Cd, Pb: LEZ/TR ranged between 0.64 and 0.82), OC (LEZ/TR = 0.85 ± 0.12) and NH4+ (LEZ/TR = 0.92 ± 0.07).OP measures, expressed as OP/m3 or OP/mg, were comparable between sites both for OPDTT and OPDCFH, thus not showing any significant impact of local traffic on OP values at sites. OPDTT and OPDCFH showed contrasting seasonal and daily trends, indicating that the two a-cellular assays gave complementary information on the OP of particles in Milan. The two OP assays resulted to be sensitive to different chemical properties of PM samples. OPDTT correlated positively only with Global Radiation (Spearman's rs = 0.38, p < 0.05), which could be considered as a proxy for high concentrations of secondary oxidizing organics, while OPDCFH was related to various PM chemical species, mainly correlated with total mass (rs = 0.65; p < 0.01), elements (e.g. Zn, rs = 0.67; As, rs = 0.65; p < 0.01) and the sum of sulfate and nitrate (rs = 0.63; p < 0.01), a proxy for secondary aerosol