Les particules fines atmosphériques de taille nanométrique ont un effet important sur la qualité de l’air, le climat et la santé. Si l’effet est reconnu, la mesure quantitative de ces impacts reste un enjeu majeur. Les difficultés à surmonter sont reliées à la forte inhomogénéité des particules, tant sur la distribution spatio-temporelle de leur concentration que sur leur morphologie et leur taille. Le développement des méthodes de mesure optique à distance non invasives telles que le Lidar (Light Detection And Raging) participe à combler cette lacune. Ce travail met en oeuvre une méthodologie de télédétection de l’aérosol urbain, dans laquelle les interactions photons-matière de type élastique et non élastique sont considérées pour estimer les paramètres optiques des particules. L’état de polarisation de la lumière diffusée est également examiné permettant de sonder la phase thermodynamique des particules observées. L’étude a consisté à caractériser les performances de la détection lidar des aérosols urbains en considérant les propriétés spectrales et la polarisation de la diffusion optique dans le domaine ultraviolet-visible. La perturbation majeure de la mesure, la lumière solaire, a été précisément évaluée et minimisée en agissant sur la résolution spectrale de la mesure et sur la polarisation du faisceau laser émis. La validation de la télédétection des particules fines atmosphériques dans l’ultraviolet est présentée. Elle est basée sur une comparaison entre la mesure Lidar et des mesures par spectrométrie de masse (AMS : Aerosol Mass Spectroscopy). Finalement, sur les bases de ces travaux, un nouveau détecteur a été conçu, développé et ensuite évalué à partir de la station Lidar permanente du laboratoire. Ainsi de très faibles taux de dépolarisation de l’atmosphère dans le domaine de l’ultraviolet, de 0,33 %, ont pu être mesurés. Ceci ouvre des perspectives intéressantes sur l’étude de la dynamique physique des particules atmosphériques de taille nanométrique / Atmospheric particles of nanometric size have a significant effect on air quality, climate and health. If the effects are recognized, the quantification of their impacts remains a major challenge. The challenges are related to the strong inhomogeneity of the spatial and temporal distribution of morphology and size as well as the aerosol concentrations. Remote sensing methods such as LIDAR (Light Detection And Raging) contribute to filling this gap. This work implements a methodology for remote sensing of the urban aerosol, in which the elastic and inelastic interactions between photon and matter are considered to estimate the optical parameters of particles. The polarization state of scattered light is also examined to probe the thermodynamic phase of the particles. In this study we characterize the performance of urban aerosol lidar whereas the spectral and polarization properties of the backscattered light are considered in the ultraviolet and visible ranges. The sunlight which is the major disruption of the measurement was accurately assessed and minimized by controlling the spectral resolution of the detector and the polarization of the emitted laser beam. The validation of atmospheric fine particles detection by ultraviolet Lidar is presented. This validation is based on a comparison between the lidar measurements and those by mass spectrometry (AMS: Aerosol Mass Spectroscopy). Finally, on the basis of this work, a new detector was designed, developed and then evaluated. Thus very low rates of depolarization of the atmosphere (0.33%) in the ultraviolet range have been measured. This work leads to interesting perspectives on the study of the dynamics of atmospheric particles of nanometric size

Air pollutants and greenhouse gases are two groups of important trace components in the earth’s atmosphere that can affect local air quality, be detrimental to the human health and ecosystem, and cause climate change. Human activities, especially the energy use and energy production processes, are responsible for a significant share of air pollutants and greenhouse gases in the atmosphere. In this work, I specifically focused on characterizing air pollutants and greenhouse gas emissions from the on-road gasoline and diesel vehicles, which is an important energy use process that largely contributes to the urban air pollutions, and from the natural gas production systems, which is a major energy production process that has increased dramatically in recent years and is expected to have a long-lasting impact in the future. We conducted multi-seasonal measurements in the Fort Pitt Tunnel in Pittsburgh, PA to update the on-road vehicle emission factors, to measure the size distribution of vehicle emitted particulate matter (PM), and to quantify the volatility distributions of the vehicle emitter primary organic aerosol (POA). We also conducted mobile measurements in the Denver-Julesburg Basin, the Uintah Basin, and the Marcellus Shale to quantify facility-level VOC emission from natural gas production facilities, and I constructed a gridded (0.1° × 0.1°) methane emission inventory of natural gas production and distribution over the contiguous US. I found that the stricter emission standards were effective on regulating NOx and PM emissions of diesel vehicles and the NOx, CO and organic carbon (OC) emissions of gasoline vehicles, while the elemental carbon (EC) emissions of gasoline vehicles did not change too much over the past three decades. Vehicle-emitted particles may be largely externally mixed, and a large fraction of vehicle-emitted particles may be purely composed of volatile component. Vehicle-emitted smaller particles (10– 60 nm) are dominantly (over 75%) composed of volatile component. The size-resolved particles and particles emission factors for both gasoline and diesel vehicles are also reported in this work. I also found that the POA volatility distribution measured in the dynamometer studies can be applied to describe gas-particle partitioning of ambient POA emissions. The POA volatility distribution measured in the tunnel does not have significant diurnal or seasonal variations, which indicate that a single volatility distribution is adequate to describe the gas-particle partitioning of vehicle emitted POA in the urban environment. The facility-level VOC emission rates measured at gas production facilities in all three gas production fields are highly variable and cross a range of ~2-3 order of magnitudes. It suggests that a single VOC emission profile may not be able to characterize VOC emissions from all natural gas production facilities. My gridded methane emission inventory over the contiguous US show higher methane emissions over major natural gas production fields compared with the Environmental Protection Agency Inventory of US Greenhouse Gas Emission and Sinks (EPA GHGI) and the Emission Database for Global Atmospheric Research, version 4.2 (Edgar v4.2). The total methane emissions of the natural gas production and distribution sector estimated by my inventory are 74% and 20% higher than the Edgar v4.2 and EPA GHGI, respectively. I also run the GEOS-Chem methane simulation with my inventory and EPA GHGI and compare with the GOSAT satellite data, and results show that my inventory can improve the model and satellite comparison, but the improvement is very limited. The size-resolved emission factors of vehicle emitted particles and POA volatility distribution reported in this work can be applied by the chemical transport models to better quantify the contribution of vehicle emissions to the PM in the atmosphere. Since our measurement of VOC emissions of natural gas production facilities were conducted before EPA started to regulate VOC emissions from the O&NG production facilities in 2016, the facility-level VOC emission rates reported in this work can serve as the basis for future studies to test the effectiveness of the regulatory policies. The spatially resolved methane emission inventory of natural gas production and distribution constructed in this work can be applied to update the current default methane emission inventory of GEOS-Chem, and the updated methane emission inventory can be used as a better a priori emission field for top-down studies that inversely estimate methane emissions from atmospheric methane observation.

Microbial pathogens commonly transmitted through the aerosol route to surfaces, equipment, and hands in the clinical setting leads to costly and life threatening hospital-acquired infections (HAIs). Even with improved hand hygiene and surface disinfection, HAIs continue to persist in healthcare environments, warranting consideration of novel interventions to reduce the transmission risk of HAIs. This study quantitated the efficacy of ion generating passive air treatment (PAT) against viruses (MS2), bacteria (Escherichia coli), and bacterial spores (Bacillus thuringiensis) in a controlled environmental setting. Microorganisms were seeded into a 2.72 m3 chamber using a positive pressure nebulizing device to generate aerosolized droplets. The PAT unit was then turned on and seeded organisms were collected at various time points using impingers to concentrate the organisms into sterile aqueous solution. The microorganisms were enumerated using approved standard protocols developed in the Environment, Exposure Science, and Risk Assessment Center's laboratory at The University of Arizona. Three experiments were conducted to challenge the PAT unit. Experiment one evaluated the efficacy of the PAT unit over a single 10-minute period on microbial inactivation from the airborne environment following a single seeding; additionally, experiment one aimed to determine the efficacy of the PAT unit against viruses, bacteria, and bacterial spores on environmental surfaces; experiment two evaluated the efficacy of the PAT unit running continuously over a period of 6 hours following a single seeding; and experiment three evaluated the efficacy of the PAT unit running two continuously over a period of 5.25 hours following two seeding events. Bacterial spores from pre- and post-treatment with the PAT unit were collected and analyzed by scanning electron microscopy to assess structural differences. After a single seeding and 10 minutes of continuous treatment of the PAT unit, normalized average microbial log10 reductions of post-treatment compared to pre-treatment air concentrations were 1.67, 0.59, and 1.04 for MS2, B. thuringiensis spores, and E. coli, respectively. Differences in average log10 reductions between the control unit and the PAT unit were statistically significant for MS2 (p=0.009) and B. thuringiensis (p=0.0455), but not for E. coli (p=0.0565). The geometric mean log10 surface concentrations of MS2, B. thuringiensis, and E. coli after a single seeding and 10 minutes of continuous treatment of the PAT unit were 7.30 PFU/100 cm2, 5.90 CFU/100 cm2, and 2.74 CFU/100 cm2, respectively, compared to exposure of the control unit, 8.59 PFU/100 cm2, 6.03 CFU/100 cm2, and 4.96 CFU/100 cm2, respectively. There was a statistically significant difference between the mean log10 surface concentrations following 10 minutes of treatment with the control unit compared to the PAT unit for E. coli (p=0.002), but not for MS2 (p=0.3358) or B. thuringiensis (p=0.0866). After a single seeding and 6-hours of continuous treatment of the PAT unit, normalized average microbial log10 reductions of MS2 and B. thuringiensis were 1.43 and 1.32, respectively. The difference in average log10 reduction of all post-treatment samples between the control unit and the PAT unit was statistically significant for B. thuringiensis (p=0.0008) but not for MS2 (p=0.2568). After two seedings and 5.25 hours of continuous treatment of the PAT unit, normalized average microbial log10 reductions of MS2 and B. thuringiensis were 1.59 and 1.26, respectively. There was a statistically significant difference in the average log10 reductions between the control unit and the PAT unit for MS2 (p=0.002) and B. thuringiensis (p=0.0003). Scanning electron microscopy analysis identified visual modification to B. thuringiensis spores following treatment with the PAT unit. In this study, the tested ion generating PAT unit was effectively able to reduce airborne microbial concentrations between 1-2 log10 in a controlled chamber environment within 10 minutes and up to 6 hours of treatment. The implications of this study suggest that ion producing PAT systems may represent a beneficial supplement to cleaning and disinfection practices in the reduction of pathogen contamination from the airborne and fomite-airborne routes.

[pt] No litoral brasileiro, do Rio Grande do Norte até Rio de Janeiro, se encontram os mais importantes depósitos de areias monazíticas No litoral do Município de São Francisco de Itabapoana, no estado de Rio de Janeiro, encontram-se importantes jazidas de areias monazíticas, e na vila de Buena, situada neste município, se encontra uma usina de beneficiamento de areias monazíticas. Nela são obtidos concentrados de ilmenita, zirconita, rutilo e monazita utilizando separadores letrostáticos, eletromagnéticos e gravimétricos (espirais, planos inclinados e mesas vivratorias). Com o objetivo de caracterizar a exposição dos habitantes desta vila a partículas de poeira na fração respirável foram coletadas amostras de aerossóis usando impactadores em cascata, amostradores portáteis com ciclone e amostras de bioindicadores. As amostras foram analisadas pelo método PIXE (Particle Induced X ray Emission) para determinação da concentração dos metais e do MMAD (Mass Median Aerodinamic Diameter), por PDMS (Plasma Desorption Mass Spectrometry) para identificação dos compostos presentes. As amostras de aerossóis coletadas com amostradores portáteis e de bioindicadores foram analisadas para determinação da concentração dos isótopos das séries naturais do tório e urânio. Os resultados indicam que os habitantes estão expostos a partículas contendo metais na fração respirável do aerossol geradas por fontes tanto antropogênicas , quanto naturais. As amostras de bioindicadores indicam os habitantes da vila tem estado expostos a radionuclídeos das séries naturais do tório e urânio nos últimos 15 anos. / [en] The main deposit of mineral sands in Brasil occur from the Rio Grande do Norte State to Rio de Janeiro State. The main commercial deposit is located in Buena, a village at São Francisco de Itabapoana, Rio de Janeiro State. In buena there is a plant that process minerals sands to obtain ilmenite, zirconite, rutile and monazite concentrates. This plant belongs to the Industrias Nucleares Brasileiras (INB). Close to this plant there is a small village. Aerosols samples were collected using cascade impactors and cyclones in order to characterize human exposure to airborne particles in the respirable fraction. Lichens samples were also collected. The samples were analyzed by PIXE (Particle Induced X ray Emission) for determination of elemental mass concentration and MMAD (Mass Median Aerodynamic Diameter). PDMS (Plasma Desorption Mass Spectrometry) allows the identification of the chemicals compounds present in the samples. The concentrations of radionuclides from the thorium and uranium natural series were also determined. The results show that the inhabitants were espoused to airborne particles in the respirable fraction of aerosols from natural and anthropogenic sources. The lichens samples indicate that the inhabitants have been exposed to radionuclides from the thorium and uranium natural series since last 15 years.

Les travaux présentés dans ce manuscrit sont consacrés à l'étudie du un petit instrument sophistiqué de mesure d'épaisseur optique : ODS (Optical Depth Sensor) a été conçu pour étudier l'atmosphère martienne et terrestre. L'une de ses principales missions consiste à fournir des mesures journalières de l'épaisseur optique des aérosols (AOD: Aerosol Optical Depth) et de détecter et caractériser les nuages optiquement minces à l'aube et au crépuscule. Les méthodes d'analyses sont basées sur l'utilisation de tables d'intensité reproduisant les signaux observés ODS en fonction de différents paramètres clés. Ces tables ont été réalisées à l'aide d'un code de transfert radiatif dans une géométrie en plans parallèles pour l'estimation de l'opacité des poussières, tandis que les propriétés des nuages sont issues d'un modèle de type Monte-Carlo en géométrie sphérique. Le premier objectif de ce travail a consisté à développer les algorithmes d'analyses nécessaires à l'étude du signal d'ODS. / The work presented in this manuscript is devoted to the development of reliable retrieval procedures for a lightweight and sophisticated optical depth sensor (ODS) which measures alternatively scattered flux at zenith and the sum of the direct flux and the scattered flux in the blue and red wavelength ranges. The ODS sensor is dedicated to Mars and Earth atmosphere and its principal goals are perform measurements of the daily mean aerosol optical depth (AOD) and retrieve the altitude and optical depth of high altitude clouds at twilight. The retrieval procedure is based on the use of look-up tables of intensities reproducing the signals that should be observed by ODS, as a function of different key parameters. For the estimation of AOD, the look-up tables are obtained by using a plane-parallel radiative transfer code, while for the study of cloud properties a Monte-Carlo radiative transfer code in spherical geometry is used.

LIDAR is the optical equivalent of RADAR. A LIDAR facility has been established at Rhodes University using a flashlamp-pumped dye laser as the transmitter and a photomultiplier tube at the focus of a searchlight mirror as the receiver. The setting up of the receiver and transmitter as well as the design and construction of the photon counting electronics is described. The LIDAR has been used to measure aerosol scattering ratios and temperature profiles in the stratosphere and these results are presented with the algorithms and software used to reduce the data. Finally some recommendations are made for future work

Le développement des applications industrielles relatives aux nanotechnologies entraîne un accroissement du nombre et de la variété de déchets contenant des nanomatériaux générés par l'industrie, les consommateurs et les laboratoires de R&D. Des familles de matériaux émergents incorporant des nano-objets se développent de manière significative alors que l’adéquation des filières de fin de vie (recyclage et élimination) n’est que récemment évaluée vis-à-vis des risques potentiels liés aux nanomatériaux. Les nanocomposites - dont la fin de vie est susceptible d'être prise en charge par l'incinération - font l'objet de cette thèse. L’objectif est d’une part de connaître le devenir des nano-objets (incorporés dans le nanocomposite) lors de l’incinération du nanocomposite ; et d’autre part de connaître leur comportement dans la chambre de combustion. Les essais d’incinération ont été réalisés à l’échelle laboratoire dans un four tubulaire et un cône calorimètre spécialement modifiés dans le but de contrôler les paramètres clés de l’incinération. Les suivis temporels des concentrations en gaz et des concentrations en nombre de l’aérosol de combustion ainsi que l’imagerie en microscopie électronique nous ont permis d’étudier les émissions et la décomposition thermique. Par ailleurs, l’influence de différents paramètres tels que la température de combustion, l’oxygénation de l’échantillon, le taux d’incorporation et la nature du nano-objet incorporé, sur la nature des émissions, a été étudiée. Enfin, pour faciliter l’utilisation des résultats au niveau opérationnel, un arbre décisionnel a été proposé aux décideurs publics et aux exploitants d’unité d’incinération. / Nanocomposites have been widely studied and produced since the end of the nineties. These trendy materials containing nanomaterials are expected to end up in incineration waste plants due to the lack of specific recovery procedures. The aim of this work is to investigate the behavior and the fate of the nano-objects from nanocomposites during their incineration and to give insights on potential environmental risk related to the incineration of waste containing nanomaterials. Incineration tests have been performed at lab-scale using a specific tubular furnace and a cone calorimeter which have been modified in order to control the key incineration parameters within both the combustion and post-combustion zones. The influence of the nano-objects presence on the combustion mechanisms (aerosol release and decomposition) is investigated. It seems necessary to address the issue of the fate of nano-objects incorporated initially in the polymer: are they destroyed, do they undergo changes during their stay in the incinerator furnace, and where are they are released ? The combustion residues and the combustion aerosol (collected downstream the incinerator) have been characterized using various techniques devoted to the analysis of aerosols. Furthermore, it has been studied the influence of different parameters (temperature of combustion, oxygen rate, loading of nano-objects, type of nano-objects) on the nature of emissions. Finally, a decision tree has been proposed to decision-makers and incineration plant managers in order to facilitate the use of the results on an operational level.

La région arctique est particulièrement sensible au changement climatique. Aux latitudes polaires, les nuages arctiques ont un effet important sur le bilan radiatif à la surface. La première partie de ce travail est constitué de l’intercomparaison instrumentale au sol à la station PUY en Mai 2013. Les mesures ont montré une bonne corrélation entre les diamètres effectifs et les distributions en taille des gouttelettes d’eau obtenus par les instruments, mais avec des biais systématiques sur les concentrations. Ces biais ont été reliés à l’estimation du volume d’échantillonnage et nous avons donc proposé une méthode consistant à normaliser les données par rapport à un instrument qui réalise des mesures intégrées. D’autre part, le FSSP et le FM ont fait l’objet d’expériences visant à évaluer l’influence de l’angle de déviation par rapport au vent extérieur et de la vitesse du vent. La seconde partie de ce travail a pour objet la campagne de mesure qui s’est déroulée à la station du Mont-Zeppelin, Ny-Alesund, Svalbard, de Mars à Mai 2012 dans le cadre du projet CLIMSLIP. Une comparaison a été effectuée entre un cas « pollué », avec des masses d’air provenant d’Asie de l’Est et d’Europe, et un cas « propre », dont les sources d’aérosols sont majoritairement locales et ne dépassent pas l’Europe du Nord. Les résultats ont montré que le cas pollué possède des concentrations en BC, aérosols et gouttes plus élevées, un mode accumulation plus important, un diamètre de gouttes plus faible et une fraction d’activation plus élevée. Enfin, le premier et le second effet indirect des aérosols ont pu être quantifiés. / The arctic region is especially sensitive to climate change. At high latitudes, arctic clouds have an important effect on the surface radiative budget. The first part of this work consists in a ground based cloud instrumentation intercomparison in the PUY station in May 2013. The measurements showed a good correlation between the effective diameters and the droplet size distributions obtained by the instruments, but with a systematical bias on the concentrations. These biases have been relied to the assessment of the sampling volume and we thus proposed a methodology to standardize the data according to an ensemble of particles probe. Moreover, the FSSP and the FM have been the subject of experiments to assess the influence of the deflection angle according to exterior wind and the wind speed. The second part of this work is about the measurement campaign at the Mount-Zeppelin station, Ny-Alesund, Svalbard, from March to May 2012 in the frame of the CLIMSLIP project. A comparison has been performed between a « polluted » case, with air masses coming from East Asia and Europe, and a « clean » case, where the aerosol sources are predominantly local and do not exceed the northern Europe. The results showed that the polluted case possessed higher concentrations in BC, aerosols and drops, an accumulation mode more important, weaker droplet diameters and higher activation fraction. Finally, the first and second aerosol indirect effects have been quantified.

Pour évaluer la gravité d'un accident de feu de boîte à gants dans une installation nucléaire, il est important de connaitre le terme source, qui est la quantité de matière radioactive mise en jeu. On cherche à identifier les phénomènes à l'origine de la libération de contaminants particulaires lors de la dégradation thermique de ces boîtes à gants. Deux matériaux (alumine et carbure de tungstène) ont été retenus pour simuler le comportement du contaminant considéré, le dioxyde de Plutonium. Deux dispositifs expérimentaux ont été conçus afin de contaminer et de dégrader thermiquement des plaques de Plexiglas (PMMA). Un ensemble d'essais à petite échelle a également permis de mieux comprendre les phénomènes à l'origine de la libération ou du piégeage des particules. La masse volumique du matériau utilisé a un impact direct sur l'émission des particules, la granulométrie des particules a un impact lorsque la dégradation thermique est rapide (flux thermique élevé). Ceci s'explique par l'interaction entre les particules émises et l'écoulement en proche paroi, phénomène qui a pu être observé expérimentalement. Une modélisation numérique de la situation étudiée a été réalisée et a permis de reproduire partiellement les résultats expérimentaux. Des améliorations peuvent encore être apportées, notamment sur la représentation du phénomène de piégeage des particules dans la matrice polymère. Cette étude pourra également donner des éclaircissements sur la problématique de l'émission des nanoparticules lors de la combustion de polymères nanochargés. / In order to assess the consequences of a glove box fire occurring in a nuclear facility, it is important to gather information on the source term, the amount of radioactive material that can be emitted to the environment. The objective is to identify the different phenomenon contributing to the release of radioactive particles from the surface of glove box materials undergoing pyrolysis. Two materials (alumina and tungsten carbide) were chosen as possible surrogates of the considered radioactive material, which is Plutonium dioxide. Two experimental facilities were designed to generate deposit on Plexiglas (PMMA) plates and burn them. Several small-scale experiments were also conducted to obtain knowledge of the phenomenon causing the release or trapping of the particles. Material density was found to have a direct impact on the release of particles, while particle size distribution had an impact only for fast thermal degradation (corresponding to high external heat flux). The reason is the strong interaction between the particles and the air flow close to the sample surface, which has been observed experimentally. A theoretical model of the problem was constructed, it was able to reproduce the experimental results, albeit partially. Improvements can be made, especially on the modelling of the trapping of particle by the polymer matrix. This study could help in understanding the problematic of nanoparticle emission from burning nanomaterials.

La formation de nouvelles particules est un processus complexe à l’origine d’une fraction importante des concentrations en nombre de particules observées dans l’atmosphère. En jouant le rôle de noyau de condensation (CCN) pour la formation des gouttelettes de nuage, les particules issues de ce processus impactent le bilan radiatif terrestre. Fréquemment observée et documentée à basse altitude, la formation de nouvelles particules a plus rarement fait l’objet d’études à haute altitude. L’analyse des données obtenues en 2012 à la plus haute station du monde, Chacaltaya (5240 m, Bolivie) révèle une fréquence d’observation annuelle du processus remarquablement élevée (64%), avec de nombreux évènements multiples. Les mesures conduites à la station du puy de Dôme (1465 m, ACTRIS, GAW) qui bénéficie d’un dispositif instrumental rare ont plus particulièrement permis de mettre en évidence le déroulement du processus en troposphère libre. Une analyse complète de l’extension verticale du processus rendue possible grâce aux données aéroportées obtenues au-dessus du bassin Méditerranéen dans le cadre du projet HYMEX (MISTRALS, automne 2012) a montré qu’en plus d’être observé à haute altitude, le processus de formation de nouvelles particules semblait y être clairement favorisé, avec une probabilité d’observation multipliée par 10 au-dessus de 1000 m. De plus, à ces altitudes le processus de formation de nouvelles particules pourrait être une source importante de CCN, comme le suggèrent les résultats obtenus à Chacaltaya, où dans 68% des évènements analysés les particules formées atteignent des diamètres suffisants pour jouer le rôle de CCN. La diversité des environnements associés aux bases de données utilisées a également permis d’apporter des éléments relatifs à la compréhension du processus du point de vue de la charge des embryons formés, de l’identité des précurseurs gazeux impliqués et des paramètres atmosphériques influençant le processus. Ces éléments sont déterminants pour une prise en compte optimale du processus de formation de nouvelles particules dans les modèles. / New particle formation (NPF) results from a complex sequence of multiple processes and contributes to an important fraction of the total atmospheric aerosol number concentration. After they grow, newly formed particles can act as cloud condensation nuclei (CCN), and thus have indirect effect on the Earth radiative balance through cloud related radiative processes. While NPF has often been observed and studied at low altitudes, the occurrence of the process is poorly documented in the literature for high altitude sites. We report a high annual frequency of the NPF process (64%) at the highest measurement site in the world, Chacaltaya (5240 m, Bolivia), in 2012, with frequent multiple events. At the puy de Dôme station (1465 m, ACTRIS, GAW), the occurrence of NPF in the free troposphere was detected using a unique instrumental setup. A complete analysis of the vertical extension of the NPF process was performed based on airborne measurements conducted above the Mediterranean basin in the frame of the HYMEX project (MISTRALS, September – November 2012). Our observations suggest that NPF could be favored at high altitudes with a probability of occurrence increased by 10 above 1000 m. At these altitudes, NPF could significantly contribute to the production of CCN, since 68% of the analyzed events show particle growth up to CCN sizes at Chacaltaya. The high number of observations recorded in various environments also contributed to improve our knowledge regarding the charge of the nucleated clusters, the identity of the gaseous precursors and the atmospheric parameters influencing the NPF process. This will allow a better parameterization of the NPF process in modelling tools.