Letteratura scientifica selezionata sul tema "Individual atmospheric particles"
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Articoli di riviste sul tema "Individual atmospheric particles"
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Liang, Zhancong, Yangxi Chu, Masao Gen e Chak K. Chan. "Single-particle Raman spectroscopy for studying physical and chemical processes of atmospheric particles". Atmospheric Chemistry and Physics 22, n. 5 (7 marzo 2022): 3017–44. http://dx.doi.org/10.5194/acp-22-3017-2022.
Testo completoAbstract (sommario):
Abstract. Atmospheric particles experience various physical and chemical processes and change their properties during their lifetime. Most studies on atmospheric particles, both in laboratory and field measurements, rely on analyzing an ensemble of particles. Because of different mixing states of individual particles, only average properties can be obtained from studies using ensembles of particles. To better understand the fate and environmental impacts of atmospheric particles, investigations on their properties and processes at a single-particle level are valuable. Among a wealth of analytic techniques, single-particle Raman spectroscopy provides an unambiguous characterization of individual particles under atmospheric pressure in a non-destructive and in situ manner. This paper comprehensively reviews the application of such a technique in the studies of atmospheric particles, including particle hygroscopicity, phase transition and separation, and solute–water interactions, particle pH, and multiphase reactions. Investigations on enhanced Raman spectroscopy and bioaerosols on a single-particle basis are also reviewed. For each application, we describe the principle and representative examples of studies. Finally, we present our views on future directions on both technique development and further applications of single-particle Raman spectroscopy in studying atmospheric particles.
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Huang, Yuanzhou, Fabian Mahrt, Shaun Xu, Manabu Shiraiwa, Andreas Zuend e Allan K. Bertram. "Coexistence of three liquid phases in individual atmospheric aerosol particles". Proceedings of the National Academy of Sciences 118, n. 16 (15 aprile 2021): e2102512118. http://dx.doi.org/10.1073/pnas.2102512118.
Testo completoAbstract (sommario):
Individual atmospheric particles can contain mixtures of primary organic aerosol (POA), secondary organic aerosol (SOA), and secondary inorganic aerosol (SIA). To predict the role of such complex multicomponent particles in air quality and climate, information on the number and types of phases present in the particles is needed. However, the phase behavior of such particles has not been studied in the laboratory, and as a result, remains poorly constrained. Here, we show that POA+SOA+SIA particles can contain three distinct liquid phases: a low-polarity organic-rich phase, a higher-polarity organic-rich phase, and an aqueous inorganic-rich phase. Based on our results, when the elemental oxygen-to-carbon (O:C) ratio of the SOA is less than 0.8, three liquid phases can coexist within the same particle over a wide relative humidity range. In contrast, when the O:C ratio of the SOA is greater than 0.8, three phases will not form. We also demonstrate, using thermodynamic and kinetic modeling, that the presence of three liquid phases in such particles impacts their equilibration timescale with the surrounding gas phase. Three phases will likely also impact their ability to act as nuclei for liquid cloud droplets, the reactivity of these particles, and the mechanism of SOA formation and growth in the atmosphere. These observations provide fundamental information necessary for improved predictions of air quality and aerosol indirect effects on climate.
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Iwata, Ayumi, e Atsushi Matsuki. "Characterization of individual ice residual particles by the single droplet freezing method: a case study in the Asian dust outflow region". Atmospheric Chemistry and Physics 18, n. 3 (7 febbraio 2018): 1785–804. http://dx.doi.org/10.5194/acp-18-1785-2018.
Testo completoAbstract (sommario):
Abstract. In order to better characterize ice nucleating (IN) aerosol particles in the atmosphere, we investigated the chemical composition, mixing state, and morphology of atmospheric aerosols that nucleate ice under conditions relevant for mixed-phase clouds. Five standard mineral dust samples (quartz, K-feldspar, Na-feldspar, Arizona test dust, and Asian dust source particles) were compared with actual aerosol particles collected from the west coast of Japan (the city of Kanazawa) during Asian dust events in February and April 2016. Following droplet activation by particles deposited on a hydrophobic Si (silicon) wafer substrate under supersaturated air, individual IN particles were located using an optical microscope by gradually cooling the temperature to −30 ∘C. For the aerosol samples, both the IN active particles and non-active particles were analyzed individually by atomic force microscopy (AFM), micro-Raman spectroscopy, and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Heterogeneous ice nucleation in all standard mineral dust samples tested in this study was observed at consistently higher temperatures (e.g., −22.2 to −24.2 ∘C with K-feldspar) than the homogeneous freezing temperature (−36.5 ∘C). Meanwhile, most of the IN active atmospheric particles formed ice below −28 ∘C, i.e., at lower temperatures than the standard mineral dust samples of pure components. The most abundant IN active particles above −30 ∘C were predominantly irregular solid particles that showed clay mineral characteristics (or mixtures of several mineral components). Other than clay, Ca-rich particles internally mixed with other components, such as sulfate, were also regarded as IN active particle types. Moreover, sea salt particles were predominantly found in the non-active fraction, and internal mixing with sea salt clearly acted as a significant inhibiting agent for the ice nucleation activity of mineral dust particles. Also, relatively pure or fresh calcite, Ca(NO3)2, and (NH4)2SO4 particles were more often found in the non-active fraction. In this study, we demonstrated the capability of the combined single droplet freezing method and thorough individual particle analysis to characterize the ice nucleation activity of atmospheric aerosols. We also found that dramatic changes in the particle mixing states during long-range transport had a complex effect on the ice nucleation activity of the host aerosol particles. A case study in the Asian dust outflow region highlighted the need to consider particle mixing states, which can dramatically influence ice nucleation activity.
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Ro, Chul-Un. "Quantitative energy-dispersive electron probe X-ray microanalysis of individual particles". Powder Diffraction 21, n. 2 (giugno 2006): 140–44. http://dx.doi.org/10.1154/1.2204068.
Testo completoAbstract (sommario):
An electron probe X-ray microanalysis (EPMA) technique using an energy-dispersive X-ray detector with an ultrathin window, designated low-Z particle EPM, has been developed. The low-Z particle EPMA allows the quantitative determination of concentrations of low-Z elements, such as C, N, and O, as well as higher-Z elements that can be analyzed by conventional energy-dispersive EPMA. The quantitative determination of low-Z elements (using full Monte Carlo simulations, from the electron impact to the X-ray detection) in individual environmental particles has improved the applicability of single-particle analysis, especially in atmospheric environmental aerosol research; many environmentally important atmospheric particles, e.g. sulfates, nitrates, ammonium, and carbonaceous particles, contain low-Z elements. The low-Z particle EPMA was applied to characterize loess soil particle samples of which the chemical compositions are well defined by the use of various bulk analytical methods. Chemical compositions of the loess samples obtained from the low-Z particle EPMA turn out to be close to those from bulk analyses. In addition, it is demonstrated that the technique can also be used to assess the heterogeneity of individual particles.
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Katrinak, Karen A., David W. Brekke e John P. Hurley. "Freeze-dried dispersions for automated SEM analysis of individual submicron airborne particulates". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 1 (agosto 1992): 408–9. http://dx.doi.org/10.1017/s0424820100122447.
Testo completoAbstract (sommario):
Individual-particle analysis is well established as an alternative to bulk analysis of airborne particulates. It yields size and chemical data on a particle-by-particle basis, information that is critical in predicting the behavior of air pollutants. Individual-particle analysis is especially important for particles with diameter < 1 μm, because particles in this size range have a disproportionately large effect on atmospheric visibility and health.
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Orlić, I., Y. K. Ng, F. Watt e S. M. Tang. "Nuclear microscopy of individual atmospheric aerosol particles". Journal of Aerosol Science 27 (settembre 1996): S661—S662. http://dx.doi.org/10.1016/0021-8502(96)00403-x.
Testo completo
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Schmitt, C. G., e A. J. Heymsfield. "Total Surface Area Estimates for Individual Ice Particles and Particle Populations". Journal of Applied Meteorology 44, n. 4 (1 aprile 2005): 467–74. http://dx.doi.org/10.1175/jam2209.1.
Testo completoAbstract (sommario):
Abstract Representations for the surface area of ice particles in terms of the projected area have been developed using two different methods. The first method uses ice particles that are imaged in situ and geometric calculations that are based on the outline of the two-dimensional image of the particle. The second method uses computer-generated ice particle shapes and calculates the total surface area analytically. The results of the second method compare reasonably well with the results of the first method. Surface area estimates for individual particles were combined with particle size distribution and projected area measurements from the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL)–Florida Area Cirrus Experiment (FACE) field project to give total surface area estimates for observed ice particle populations. Population surface area estimates were also made from balloon-borne replicator data collected during the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment, phase II (FIRE-II). A relationship between the particle population surface area and projected area (cloud extinction) has been derived. The total particle surface area for particle populations is estimated to be between 8 and 10 times the projected area or between 4 and 5 times the extinction and has a small dependence on the properties of the particle size distribution for particles observed in random orientations.
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Yoo, Hanjin, Li Wu, Hong Geng e Chul-Un Ro. "Physicochemical and temporal characteristics of individual atmospheric aerosol particles in urban Seoul during KORUS-AQ campaign: insights from single-particle analysis". Atmospheric Chemistry and Physics 24, n. 2 (19 gennaio 2024): 853–67. http://dx.doi.org/10.5194/acp-24-853-2024.
Testo completoAbstract (sommario):
Abstract. Single-particle analysis was conducted to characterize atmospheric aerosol particles collected at Olympic Park in Seoul, South Korea, as a part of the Korea–United States Air Quality (KORUS-AQ) campaign which was carried out during May–June 2016. The KORUS-AQ campaign aimed to understand the temporal and spatial characteristics of atmospheric pollution on the Korean Peninsula through an international cooperative field study. A total of 8004 individual particles from 52 samples collected between 23 May–5 June 2016 were investigated using a quantitative electron probe X-ray microanalysis (low-Z particle EPMA), resulting in the identification of seven major particle types. These included genuine and reacted mineral dust, sea-spray aerosols, secondary aerosol particles, heavy-metal-containing particles, combustion particles, Fe-rich particles, and others (particles of biogenic and humic-like substances – HULIS). Distinctly different relative abundances of individual particle types were observed during five characteristic atmospheric situations, namely (a) a mild haze event influenced by local emissions and air mass stagnation; (b) a typical haze event affected by northwestern air masses with a high proportion of sulfate-containing particles; (c) a haze event with a combined influence of northwestern air masses and local emissions; (d) a clean period with low particulate matter concentrations and a blocking pattern; and (e) an event with an enhanced level of heavy-metal-containing particles, with Zn, Mn, Ba, Cu, and Pb being the major species identified. Zn-containing particles were mostly released from local sources such as vehicle exhausts and waste incinerations, while Mn-, Ba-, and Cu-containing particles were attributed to metal alloy plants or mining. The results suggest that the morphology and chemical compositions of atmospheric aerosol particles in urban areas vary depending on their size, sources, and reaction or aging status and are affected by both local emissions and long-range air masses.
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Zelenay, V., R. Mooser, T. Tritscher, A. Křepelová, M. F. Heringa, R. Chirico, A. S. H. Prévôt et al. "Aging induced changes on NEXAFS fingerprints in individual combustion particles". Atmospheric Chemistry and Physics 11, n. 22 (24 novembre 2011): 11777–91. http://dx.doi.org/10.5194/acp-11-11777-2011.
Testo completoAbstract (sommario):
Abstract. Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing of the combustion exhaust gases is still a subject of discussion. In this work, individual soot particles emitted from two different vehicles, a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS spectra from the unprocessed particles and those resulting from exhaust photooxidation in the chamber revealed changes in the carbon functional group content. For the wood stove emissions, these changes were minor, related to the relatively mild oxidation conditions. For the EURO 2 transporter emissions, the most apparent change was that of carboxylic carbon from oxidized organic compounds condensing on the primary soot particles. For the EURO 3 car emissions oxidation of primary soot particles upon photochemical aging has likely contributed as well. Overall, the changes in the NEXAFS fingerprints were in qualitative agreement with data from an aerosol mass spectrometer. Furthermore, by taking full advantage of our in situ microreactor concept, we show that the soot particles from all three combustion sources changed their ability to take up water under humid conditions upon photochemical aging of the exhaust. Due to the selectivity and sensitivity of the NEXAFS technique for the water mass, also small amounts of water taken up into the internal voids of agglomerated particles could be detected. Because such small amounts of water uptake do not lead to measurable changes in particle diameter, it may remain beyond the limits of volume growth measurements, especially for larger agglomerated particles.
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Song, Y. C., H. J. Eom, H. J. Jung, M. A. Malek, H. K. Kim, H. Geng e C. U. Ro. "Investigation of aged Asian dust particles by the combined use of quantitative ED-EPMA and ATR-FTIR imaging". Atmospheric Chemistry and Physics 13, n. 6 (27 marzo 2013): 3463–80. http://dx.doi.org/10.5194/acp-13-3463-2013.
Testo completoAbstract (sommario):
Abstract. In our previous works, it was demonstrated that the combined use of quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), which is also known as low-Z particle EPMA, and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) imaging has great potential for a detailed characterization of individual aerosol particles. In this study, extensively chemically modified (aged) individual Asian dust particles collected during an Asian dust storm event on 11 November 2002 in Korea were characterized by the combined use of low-Z particle EPMA and ATR-FTIR imaging. Overall, 109 individual particles were classified into four particle types based on their morphology, elemental concentrations, and molecular species and/or functional groups of individual particles available from the two analytical techniques: Ca-containing (38%), NaNO3-containing (30%), silicate (22%), and miscellaneous particles (10%). Among the 41 Ca-containing particles, 10, 8, and 14 particles contained nitrate, sulfate, and both, respectively, whereas only two particles contained unreacted CaCO3. Airborne amorphous calcium carbonate (ACC) particles were observed in this Asian dust sample for the first time, where their IR peaks for the insufficient symmetric environment of CO32− ions of ACC were clearly differentiated from those of crystalline CaCO3. This paper also reports the first inland field observation of CaCl2 particles probably converted from CaCO3 through the reaction with HCl(g). HCl(g) was likely released from the reaction of sea salt with NOx/HNO3, as all 33 particles of marine origin contained NaNO3 (no genuine sea salt particle was encountered). Some silicate particles with minor amounts of calcium were observed to be mixed with nitrate, sulfate, and water. Among 24 silicate particles, 10 particles are mixed with water, the presence of which could facilitate atmospheric heterogeneous reactions of silicate particles including swelling minerals, such as montmorillonite and vermiculite, and nonswelling ones, such as feldspar and quartz. This paper provides detailed information on the physicochemical characteristics of these aged individual Asia dust particles through the combined use of the two single-particle analytical techniques, and using this analytical methodology it is clearly shown that internal mixing states of the aged particles are highly complicated.
Tesi sul tema "Individual atmospheric particles"
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El, Haber Manuella. "Rôle des surfactants sur la formation des nuages : impact de la composition des aérosols et tension de surface de particules individuelles d'aérosols atmosphériques". Electronic Thesis or Diss., Lyon 1, 2024. http://www.theses.fr/2024LYO10243.
Testo completoAbstract (sommario):
Dans l’atmosphère terrestre, les aérosols jouent un rôle crucial dans la diffusion et l’absorption des rayonnements solaires, et en tant que noyaux de condensation dans la formation des nuages. La vapeur d’eau se condense progressivement sur les particules d’aérosols, pour former des gouttelettes de nuage. Ce phénomène est régi par l’équation de Köhler dont un paramètre essentiel est la tension de surface. Pendant longtemps, ce paramètre n’a pourtant pas été pris en compte dans les modèles atmosphériques : la valeur de la tension de surface des aérosols a été considérée égale à celle de l’eau (~72.5 mN/m). Cependant, au cours dernières années, suite à la mise en évidence de la présence de tensioactifs à des concentrations significatives dans les aérosols atmosphériques, un intérêt croissant s’est porté sur la détermination de la tension de surface des particules d’aérosols atmosphériques. Ainsi dans la cadre de ce travail, les effets de la présence de composants d’intérêt atmosphérique tels les acides organiques (acide oxalique et acide glutarique) et les sels inorganiques (NaCl et (NH4)2SO4) sur la tension de surface de solutions de tensioactifs amphiphiles (TritonX100, Brij35, SDS, CTAC) ont été étudiés. Des comportements fortement non idéaux ont été observés pour la plupart des mélanges étudiés avec des synergies détectées dans certains cas. Les principaux composants atmosphériques augmentaient l'efficacité des tensioactifs amphiphiles. En parallèle, une technique de détermination de la tension de surface de particules atmosphériques individuelles microniques et submicroniques a été développée. L’application de la méthode micro Wilhelmy dans un microscope à force atomique (AFM) en employant une pointe cylindrique, a permis de quantifier la tension de surface des gouttelettes condensées sur des particules atmosphériques sous humidité relative contrôlée. Cette méthode a été validée par des mesures de la tension de surface sur des liquides de références et appliquée par suite sur divers prélèvements atmosphériques. Les valeurs de tensions de surface déterminées dans les particules atmosphériques individuelles sont inférieures à la tension de surface de l’eau. D’autre part, ces études ont montré que la condensation de l’eau sur ces particules d’aérosol est corrélée avec la tension de surface, pour une humidité relative de 82 ± 2 %. Ainsi, ce travail a permis pour la première fois de mesurer directement la tension de surface des particules individuelles atmosphériques et d’élucider l’effet de la tension de surface sur la formation de nuageIn Earth's atmosphere, aerosols play a crucial role in the diffusion and absorption of solar radiation, and as condensation nuclei in cloud formation. Water vapor gradually condenses on aerosol particles to form cloud droplets. This phenomenon is governed by the Köhler equation, where surface tension is a key parameter. For a long time, this parameter was not taken into account in atmospheric models: the surface tension value of aerosols was considered equal to that of water (~72.5 mN/m). However, significant concentrations of surfactants in atmospheric aerosols have been identified in recent years. Based on those results, there has been an increasing interest for determining the surface tension of atmospheric aerosol particles. In this work, the effects of the presence of typical aerosol components e.g., organic acids (oxalic acid and glutaric acid) and inorganic salts (NaCl and (NH4)2SO4) on the surface tension of amphiphilic surfactant solutions (TritonX100, Brij35, SDS, CTAC) were studied. Strong non-ideal behaviors were observed in most of the studied mixtures with synergies detected in some cases. The main atmospheric components increased the efficiency of the amphiphilic surfactants. In parallel, a technique for determining the surface tension of individual micron and submicron atmospheric particles was developed. The application of the micro Wilhelmy method in an atomic force microscope (AFM) using a cylindrical tip, made it possible to quantify the surface tension of droplets condensed on atmospheric particles under controlled relative humidity. This method was validated by surface tension measurements on reference liquids and subsequently applied to various atmospheric samples. The surface tension values determined in individual atmospheric particles are lower than the surface tension of water. Furthermore, these studies showed that the condensation of water on these aerosol particles is correlated with the surface tension, for a relative humidity of 82 ± 2%. Within this work, the surface tension of individual atmospheric particles was directly measured for the first time. Moreover, the effect of surface tension on cloud formation has been elucidated
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Fraund, Matthew. "Developing X-ray Spectromicroscopic Techniques to Quantitatively Determine Population Statistics and Individual Particle Composition of Complex Mixed Aerosols". Scholarly Commons, 2019. https://scholarlycommons.pacific.edu/uop_etds/3622.
Testo completoAbstract (sommario):
Aerosols are a major source of uncertainty in estimates of anthropogenic effects on global radiative forcing and can pose serious health concerns. While many instrumental techniques capable of analyzing aerosol samples are available, individual-particle spectromicroscopic techniques like the ones presented here are the only ones to offer morphological and compositional measurements together. Studying the composition and mixing state of aerosol populations allowed for important aspects to be uncovered, such as: aerosol source, formation mechanism, hygroscopicity, optical properties, level of aging, and inhalation dangers. Ambient aerosols from the Amazon, both biogenic and anthropogenic, were apportioned based on their individual composition. Recently discovered organic aerosols from the central United States were identified and their chemical properties were characterized. The lead fraction of mixed lead- and zinc-rich particles from Mexico City was speciated to determine the lead’s solubility and possible bioavailability. It is through the use of these powerful spectromicroscopic techniques that a better understanding of complex mixed aerosols was achieved.
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Unga, Florin. "Investigation of atmospheric aerosol mixing state effect on measured and retrieved optical characteristics : an approach integrating individual particle analysis, remote sensing and numerical simulations". Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10023/document.
Testo completoAbstract (sommario):
Les aérosols troposphériques influencent la composition chimique de l’atmosphère, le bilan radiatif terrestre et le climat. Après formation, les aérosols subissent des processus de vieillissement altérant leurs propriétés microphysiques et chimiques. L’étude de l’impact environnemental des aérosols à différentes échelles spatio-temporelles doit donc tenir compte des transformations physico-chimiques. Les objectifs poursuivis sont : (i) d’étudier par microscopie analytique électronique à balayage et en transmission la composition élémentaire et l'état de mélange des particules atmosphériques prélevées lors d'épisodes de charge élevée en aérosol ; (ii) d’analyser les effets des propriétés microphysiques sur les caractéristiques optiques mesurées et restituées par télédétection ; (iii) de proposer un paramétrage ainsi qu’une représentation de la composition et de la structure des particules dans les algorithmes de télédétection. Ces travaux portent sur des observations dans le Nord de la France et en Afrique de l’Ouest (Sénégal) dans le cadre du Labex CaPPA et des campagnes de terrain SHADOW. Sont inclues des analyses complémentaires de la composition chimique et de la structure de particules individuelles, de mesures in situ et par télédétection de particules urbano-industrielles, désertiques et de biomasse prélevées en surface et à différentes altitudes. Une série de simulations numériques ont été utilisées dans le but d'analyser la sensibilité des observations par télédétection à l’état de mélange des aérosols. Enfin, l'intégration d'un paramétrage de la structure en "core-shell" des particules dans les algorithmes de restitution est présentée en perspectiveTropospheric aerosols play an important role in atmospheric chemistry, Earth’s radiative budget and climate. After their generation, aerosol can suffer ageing processes and altering their physicochemical properties. An accurate accounting for these processes requires observations of the aerosol properties on different temporal and spatial scales. The current thesis work is dedicated to: (i) study of physicochemical properties and mixing state of individual particles by means of analytical scanning and transmission electron microscopy for aerosols collected during episodes of elevated aerosol loading; (ii) analysis of the effect of microphysical properties on optical characteristics as measured and retrieved by remote sensing; and (iii) investigation of possible parameterization of aerosol composition and structure in remote sensing algorithms. The work presents observations conducted in northern France and western Africa (Senegal) as part of Labex CaPPA project and SHADOW field campaigns. It includes simultaneous analyses of collected individual particles composition and structure, remote sensing and in situ observations of urban/industrial, Saharan dust and biomass burning particles near the surface and on different altitudes. A series of numerical simulation devoted to an analysis of sensitivity of remote sensing observations to aerosol mixing state is conducted. Insights on possible parameterization of aerosol core-shell structure in retrieval algorithms are finally presented
Capitoli di libri sul tema "Individual atmospheric particles"
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Zuev, V. E., A. A. Zemlyanov, Yu D. Kopytin e A. V. Kuzikovskii. "Low Energy (Subexplosive) Effects of Radiation on Individual Particles". In High-Power Laser Radiation in Atmospheric Aerosols, 21–54. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5219-5_2.
Testo completo
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Shattuck, T. W., M. S. Germani e P. R. Buseck. "Cluster Analysis of Chemical Compositions of Individual Atmospheric Particles Data". In ACS Symposium Series, 118–29. Washington, D.C.: American Chemical Society, 1985. http://dx.doi.org/10.1021/bk-1985-0292.ch009.
Testo completo
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Van Grieken, R., K. Gysels, S. Hoornaert, P. Joos, J. Osan, I. Szaloki e A. Worobiec. "Characterisation of Individual Aerosol Particles for Atmospheric and Cultural Heritage Studies". In Environmental Challenges, 215–28. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4369-1_19.
Testo completo
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Haszpra, Tímea, e Tamás Tél. "Individual Particle Based Description of Atmospheric Dispersion: a Dynamical Systems Approach". In CISM International Centre for Mechanical Sciences, 95–119. Vienna: Springer Vienna, 2016. http://dx.doi.org/10.1007/978-3-7091-1893-1_4.
Testo completo
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Ma, Chang-Jin, e Gong-Unn Kang. "The Chemical Nature of Individual Size-Resolved Raindrops and Their Residual Particles Collected During High Atmospheric Loading for PM2.5". In Rainfall - Extremes, Distribution and Properties. IntechOpen, 2019. http://dx.doi.org/10.5772/intechopen.84227.
Testo completo
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Young Koo, Hye, e Dahee Park. "Conductive Powder Synthesis Technology for Improving Electrical Conductivity by One-Pot Ultrasonic Spray Pyrolysis Process". In New Advances in Powder Technology [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108937.
Testo completoAbstract (sommario):
In this chapter, we will study the spray pyrolysis process, which is a bottom-up process, and examine the composite electrode powder synthesis process and properties of the core-shell structure. Generally, it is difficult to produce fine particles from metal powders using the top-down method. Thus, the liquid phase method, which is a bottom-up process, is mainly used. However, the liquid phase method has a problem in that impurities exist in the particles. In addition, it is difficult to control the precipitation when synthesizing powder using a solution containing several types of metal salts. The spray pyrolysis process introduced here made it possible to produce composite particles in a one-pot manner without any additional processes for synthesizing the core-shell structure. In the case of core-shell structure of Ag-glass composite powder, the specific resistance of the composite electrode was significantly lowered, compared to the electrode formed by mixing glass frits individually, which improved the dispersibility of the glass. In the case of Cu composite particles with a coating layer, both Ag and glass coating layers formed a passivation layer to improve atmospheric stability, and the introduction of a coating material also improved electrical properties.
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Bailey, Matthew P., e Joan T. Hallett. "Ice Crystals in Cirrus". In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0007.
Testo completoAbstract (sommario):
Cirrus is conventionally considered as cloud forming in the Earth's upper troposphere at temperatures somewhat below -40°C, composed of ice crystals and forming long, wispy trails. This characteristic shape, in the form of a curl of hair, results from evaporation in vertical shear of horizontal winds, and leads to its Latin name—originally proposed by Luke Howard in 1803. Here we address the nucleation, growth, and evaporation processes that influence the concentration and shape of individual particles and their role in specific atmospheric phenomena. To set the scene, figure 3.1 shows examples of such crystals collected by aircraft. In this chapter, we also address the radiation and dynamic environment in which crystals grow and subsequently evaporate. Crystal growth depends on the location of a crystal with respect to the cloud edge and the intervening cloud optical thickness; evaporation depends on larger scale processes as at fronts and cumulonimbus anvils and also at inversion interfaces where shear instability and resulting gravity waves produce significant effects over a range of scales. These effects lead to differing cloud radiative properties and ultimately control of the earth's radiation budget and overall climate (Liou 1986; Stephens et al. 1990; Liou and Takano 1994; Takano and Liou 1995; Mishchenko et al. 1996; Strauss et al. 1997; Macke et al. 1998). A growing crystal implies a supersaturated or supercooled environment with respect to the solid phase and can, in general, be considered as growth from either three-fold symmetry overlying a needle, (NASA DC-8,TOGA COARE,-48°C, deep tropical convection, 1993). The replica visually shows a uniformity of color in vertical illumination, indicating a thin crystal a few micrometers thick, uniform to ±0.05 μm. e. Replica of needles, small scalene and triangular three-fold symmetry plates, hexagonal plates, columns, and irregular crystals collected by D.L.R. Falcon in thin cirrus over the Alps, temperature -55°C, October 29,1992. (Courtesy Dr. P. Wendling.) f. Replica of crystals from the evaporating tip of a contrail formed 50 s earlier by the NASA 757 aircraft sampled from the NASA DC-8. Multiple trigonal symmetry crystals are present, with a 60° rotation (left side), along with hexagonal and scalene and triangle crystals, concentration 10/cm3. Clear sky environment over Kansas, temperature -52°C, 1840-1900Z, 4 May 1996.
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Suthar, Ankush H., e Purvi M. Pandya. "Controlling Asthma Due to Air Pollution". In Mathematical Models of Infectious Diseases and Social Issues, 1–22. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-3741-1.ch001.
Testo completoAbstract (sommario):
The health of our respiratory systems is directly affected by the atmosphere. Nowadays, eruption of respiratory disease and malfunctioning of lung due to the presence of harmful particles in the air is one of the most sever challenge. In this chapter, association between air pollution-related respiratory diseases, namely dyspnea, cough, and asthma, is analysed by constructing a mathematical model. Local and global stability of the equilibrium points is proved. Optimal control theory is applied in the model to optimize stability of the model. Applied optimal control theory contains four control variables, among which first control helps to reduce number of individuals who are exposed to air pollutants and the remaining three controls help to reduce the spread and exacerbation of asthma. The positive impact of controls on the model and intensity of asthma under the influence of dyspnea and cough is observed graphically by simulating the model.
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Khanna, S. Rajesh, A. Omprakash e A. Sivaprakasam. "ENVIRONMENTAL EFFECTS OF AIR POLLUTION AND THEIR THREATS TO HUMANS IN THE WORLD". In Futuristic Trends in Social Sciences Volume 3 Book 26, 150–62. Iterative International Publishers, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3baso26p7ch3.
Testo completoAbstract (sommario):
Air pollution is the greatest threat to public health on a worldwide basis, causing approximately 7 million premature deaths every year WHO Reports. The term "air pollution" refers to the process through which the atmosphere becomes contaminated with particles and substances that are either poisonous or polluting. It contributes to global warming, as well as environmental problems such as pollution and acid rain, as well as health problems such as cancer and respiratory disorders. Both air pollution and global warming have been accelerated by human activities like transportation, electricity generation, industry emissions, and agricultural burning. Individuals' and politicians' concerns about the quality of the air they breathe are frequently a driving force behind their efforts to address the climate issue. When we have a desire for clean air, we speed up the process of addressing climate change. In this age of industrialization, it is not possible to completely get rid of air pollution, but it is possible to cut back on it using a variety of methods. As part of an effort to cut down on the amount of pollution that is allowed to be discharged into the atmosphere, the government has established an air quality guideline and is continuing to work on laws to restrict emissions. Guidelines for reducing emissions of pollutants like sulphur dioxide-[S02], particulates [PM2.5, PM10], nitrogen oxides-[NOx], carbon monoxide-[CO], ozone-[O3], and lead-[Pb] have been established by the Environmental Protection Agency [EPA]
10
Munsif, Rabia, Muhammad Zubair, Ayesha Aziz e Muhammad Nadeem Zafar. "Industrial Air Emission Pollution: Potential Sources and Sustainable Mitigation". In Environmental Emissions. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.93104.
Testo completoAbstract (sommario):
Air of cities especially in the developing parts of the world is turning into a serious environmental interest. The air pollution is because of a complex interaction of dispersion and emission of toxic pollutants from manufactories. Air pollution caused due to the introduction of dust particles, gases, and smoke into the atmosphere exceeds the air quality levels. Air pollutants are the precursor of photochemical smog and acid rain that causes the asthmatic problems leading into serious illness of lung cancer, depletes the stratospheric ozone, and contributes in global warming. In the present industrial economy era, air pollution is an unavoidable product that cannot be completely removed but stern actions can reduce it. Pollution can be reduced through collective as well as individual contributions. There are multiple sources of air pollution, which are industries, fossil fuels, agro waste, and vehicular emissions. Industrial processes upgradation, energy efficiency, agricultural waste burning control, and fuel conversion are important aspects to reducing pollutants which create the industrial air pollution. Mitigations are necessary to reduce the threat of air pollution using the various applicable technologies like CO2 sequestering, industrial energy efficiency, improving the combustion processes of the vehicular engines, and reducing the gas production from agriculture cultivations.
Atti di convegni sul tema "Individual atmospheric particles"
1
Smart, Anthony E., e John B. Abbiss. "On-Board Correlator-Based Measurements of Particle Properties and Aircraft Velocity in the Upper Atmosphere". In Photon Correlation and Scattering. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/pcs.1992.tua5.
Testo completoAbstract (sommario):
The Titan Spectron Airborne Laser Transit Anemometer1,2,3 based on measurements of particle transit time between pairs of sheets, was designed to determine the relative velocity vector between an airborne vehicle and its surrounding medium. Measurements in the upper atmosphere from a NASA F-104 aircraft suggest that the instrument can also estimate the size distribution and concentration of atmospheric aerosol particles. The energy detected during transits of the sensing sheets by individual particles, together with current values of monitors originally intended for diagnostics and performance logging permits an estimate of the radius of each particle under well defined assumptions which are discussed below. Signals from up to 900 particles per second can be individually reported to the aircraft 1553 bus, with properly sampled statistics where there are more than 900 /s. A distribution of particle radius and an estimate of concentration may be derived from these data.
2
Schleicher, N., U. Kramar, S. Norra, V. Dietze, U. Kaminski, K. Cen, Y. Yu, Melissa Denecke e Clive T. Walker. "μ-Scale Variations Of Elemental Composition In Individual Atmospheric Particles By Means Of Synchrotron Radiation Based μ-XRF Analysis". In X-RAY OPTICS AND MICROANALYSIS: Proceedings of the 20th International Congress. AIP, 2010. http://dx.doi.org/10.1063/1.3399245.
Testo completo
3
Wang, A. Y. X., P. R. Munroe, A. T. T. Tran e M. M. Hyland. "3D Tomography of Plasma Sprayed Cr-Clad Ni on Alumina". In ITSC 2016, a cura di A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen e C. A. Widener. DVS Media GmbH, 2016. http://dx.doi.org/10.31399/asm.cp.itsc2016p0161.
Testo completoAbstract (sommario):
Abstract In this work, a mechanically clad NiCr powder feedstock was deposited on alumina substrates by atmospheric plasma arc spraying. The resultant splats were analyzed for features such as interfacial bonding, splat classification and, critically, Cr distribution. Using a slice-and-view sectioning technique in a dual-beam FIB-SEM system, a representative splat exhibiting discrete Ni and Cr regions was physically deconstructed then reconstructed with visualization software to analyze individual layers with the splat. Although the powder feedstock contained Ni particles clad with clusters of Cr, the splats solidified into distinct layers of Ni and Cr with no signs of interaction between them. A model formulated based on this observation shows that the distribution of Cr cladding on the Ni particulates influences the amount and location of Cr around the solidified Ni splats.
4
Sayindla, Sneha, Bjørnar Lund, Ali Taghipour, Benjamin Werner, Arild Saasen, Knud Richard Gyland, Zalpato Ibragimova e Jan David Ytrehus. "Experimental Investigation of Cuttings Transport With Oil Based Drilling Fluids". In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54047.
Testo completoAbstract (sommario):
Drilling fluids are very complex and are essential for safe and efficient drilling operations. It is vital for the drilling operator to be able to select an appropriate fluid for each individual well, including the decision of using oil-based or water-based fluids or “muds” (OBM or WBM). In this article we present results from a comparative study of three OBM’s which are based on the same fluid system (Versatec). This work is part of a larger investigation where the main objective is to identify and evaluate the difference in the hole cleaning capabilities of OBM’s and WBM’s with similar viscosity as measured by the API/ISO standards. This paper describes an experimental investigation of cuttings transport using flow loop laboratory tests without and with injected cuttings size particles using various industrial oil based fluids with varying density and viscosity. The flow loop includes a 10 meter long test section with 2″ OD free whirling rotating steel drillstring inside a 4″ ID wellbore made of concrete elements positioned inside a steel tubing. Sand particles were injected while circulating the drilling fluid through the test section. Experiments are conducted at atmospheric conditions, but are otherwise designed to represent downhole conditions as closely as possible with respect to fluid and particle properties, flow rates and geometry. Fluids are tested at different flow rates with and without rotation of drill string, with and without sand injection. This has allowed us to study the effects of flow rate and drill string rotation on hole cleaning capabilities of different fluids. The primary results are pressure drop, steady state sand bed height in a horizontal annulus versus fluid and cuttings rates for rotating and non-rotating drill string and in particular the critical rates for fully suspended flow. The results are interpreted in light of results from laboratory characterization of the same fluids, conducted as part of the same project. The results will increase understanding of the relationship between drilling fluid properties and hole cleaning performance. This will enable the development of improved drilling fluids, both operationally and environmentally. Such know-how will also be important in order to develop more accurate transport models.
5
Safin, Ruslan, Shamil Mukhametzyanov, Albina Safina, Nour Galyavetdinov e Valeriy Gubernatorov. "RESEARCH OF THE INFLUENCE OF THE MODE PARAMETERS OF THE WATER-VACUUM EXTRACTION PROCESS ON THE YIELD OF BIOLOGICALLY ACTIVE SUBSTANCES INONOTUS OBLIQUUS". In GEOLINKS Conference Proceedings. Saima Consult Ltd, 2021. http://dx.doi.org/10.32008/geolinks2021/b1/v3/19.
Testo completoAbstract (sommario):
Inonotus obliquus or chaga birch mushroom has a fairly wide range of applications in the cosmetic, food and pharmaceutical industries due to the wide range of biologically active substances it contains. The analysis of foreign and domestic studies testifies to the ongoing research in the field of extraction of valuable components from chaga, however, issues of intensification of processes and the development of new methods of extraction remain topical. One of these methods is the water-vacuum extraction of chaga, which consists in alternating the stages of the process at atmospheric and reduced pressure. The aim of the study is to determine the optimal time parameters of the individual stages of the water-vacuum extraction of chaga to optimize the operating parameters of the process. The object of the study was chaga collected in forest plantations in central Russia in the spring season, and crushed to particles ranging in size from 0.1 to 1.2 mm. The experiments were carried out on a laboratory version of a vacuum extraction unit, which allows for the classical infusion and extraction of chaga at various variations in the pressure of the medium. Studies have shown that preliminary evacuation of dry raw materials and the introduction of a rarefied medium into the process of water extraction of chaga makes it possible to intensify the extraction process and has a positive effect on the yield and activity of extractive substances. It has been established that the preliminary evacuation of crushed chaga makes it possible to increase the efficiency of subsequent extraction and to increase the yield of valuable components by 15-18%. The optimal time for this stage was 5 minutes. The effective duration of the infusion step at atmospheric pressure was 30 minutes, and the subsequent evacuation is expediently carried out for 10 minutes. Based on the results of the presented work, the optimal scheme for carrying out the process of water-vacuum extraction of chaga was determined.
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Zhang, Guohua, e Xinhui Bi. "An individual particle perspective for the atmospheric Processing of Particulate Imidazole Compounds". In Goldschmidt2023. France: European Association of Geochemistry, 2023. http://dx.doi.org/10.7185/gold2023.19085.
Testo completo
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Kanta, A. F., M. P. Planche, C. Coddet, G. Montavon, M. Vardelle e C. C. Berndt. "Atmospheric Plasma Spray Process Control". In ITSC2008, a cura di B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima e G. Montavon. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2008. http://dx.doi.org/10.31399/asm.cp.itsc2008p1417.
Testo completoAbstract (sommario):
Abstract Parametric drifts and fluctuations occur during plasma spraying. These drifts and fluctuations originate primarily from electrode wear and intrinsic plasma jet instabilities. One challenge is to control the manufacturing process by identifying the parameter interdependencies, correlations and individual effects on the in-flight particle characteristics. Such control is needed through methods that (i) consider the interdependencies that influence process variability and that also (ii) quantify the processing parameter-process response relationships. Artificial intelligence is proposed for thermal spray applications. The specific case of predicting plasma power parameters to manufacture grey alumina (Al2O3-TiO2, 13% by wt.) coatings was considered and the influence of the plasma spray process on the in-flight particle characteristics was investigated.
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Elsebaei, A., J. Heberlein, M. Elshaer e A. Farouk. "Comparison of In-Flight Particle Properties, Splat Formation, and Coating Microstructure for Regular and Nano-YSZ Powders". In ITSC2009, a cura di B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima e G. Montavon. ASM International, 2009. http://dx.doi.org/10.31399/asm.cp.itsc2009p0861.
Testo completoAbstract (sommario):
Abstract This work investigates the effect of atmospheric plasma spraying (APS) parameters on in-flight particle properties, splat morphology, and coating microstructure for conventional and nano-size YSZ powders. Particle temperature and velocity were measured using a dual-slit velocimeter and individual splats and coating microstructures were examined in a scanning electron microscope. The results show that total porosity increases with decreasing arc current and increasing stand-off distance and that conventional powder coatings have higher total porosity at higher arc currents than coatings made from nanopowder. The effect of substrate temperature on splat formation was also assessed. Splat flattening and circularity increase with increasing substrate temperature, particularly for nanopowders.
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Bach, F. W., K. Möhwald, K. Hartz, K. Bobzin, N. Bagcivan, I. Petkovic, J. Schein, G. Forster e S. Zimmermann. "Homogenization of Coating Properties in Atmospheric Plasma Spraying – Technical Objectives and First Results of a DFG Funded Research Group". In ITSC2008, a cura di B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima e G. Montavon. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2008. http://dx.doi.org/10.31399/asm.cp.itsc2008p0141.
Testo completoAbstract (sommario):
Abstract The disadvantage of plasma torches using conventional single cathode techniques is the occurrence of azimuthal and axial instabilities inside the plasma torch. This causes electrical power fluctuations which result in inhomogeneities of the plasma jet enthalpy and with that an uneven plasma particle interaction. Hence, variations in particle properties occur and consequently an uneven coating quality is produced. Using the triple-cathode technique these electrical power fluctuations were successfully reduced, resulting in a stationary plasma flow. Thus this technique appears to offer the potential to homogenize coating properties. Similar results have been shown for plasma torches with triple anode arrangements. The goal of this research group is to homogenize properties of plasma sprayed coatings using of 3-cathode and 3-anode technologies based on numerical simulations. The approach used is to subdivide the complete APS process into the areas plasma torch, free jet as well as coating formation and characteristics. By simulation of the individual areas and combination with experimental results the corresponding process parameters will be obtained for the desired coating properties.
10
Cornelius, Jason, Douglas Adams, Larry Young, Jack Langelaan, Tomas Opazo, Sven Schmitz, Lev Rodovskiy e Benjamin Villac. "Dragonfly - Aerodynamics during Transition to Powered Flight". In Vertical Flight Society 77th Annual Forum & Technology Display. The Vertical Flight Society, 2021. http://dx.doi.org/10.4050/f-0077-2021-16698.
Testo completoAbstract (sommario):
The Dragonfly lander will enter the Titan atmosphere following an approximate 7–10-year journey through space inside its aeroshell. After atmospheric entry, deployment of the main parachute, and heatshield release, the lander will begin its transition to powered flight (TPF). TPF is a maneuver sequence used for mid-air deployment of the Dragonfly rotorcraft lander. The sequence starts just after lander release with the rotors lightly loaded and finishes when a steadystate descent condition has been attained. Mid-air deployment of a multicopter unmanned aerial system is a multidisciplinary problem involving controller choice and tuning, trajectory planning and optimization, and computational fluid dynamics analyses. This paper is an introduction to the transition of rotor flow states in TPF from the windmill brake state, through the turbulent wake state and vortex ring state, and the successful emergence into a normal operating state. A particle swarm optimized controller’s nominal trajectory is plotted on a rotor aerodynamics state chart to show the trajectory’s path through the flow states along the TPF maneuver. Results of preliminary CFD simulations show the variance of individual rotor thrust and power in the early stages of TPF followed by a successful stabilization of rotor performance. Interactional aerodynamic studies also characterize the pre-release flowfield around the lander to be benign at the start of the maneuver. Additionally, results for the lander in steady axial descent show a previously observed coaxial rotor shielding phenomenon of the upper rotor from the effects of vortex ring state.
Rapporti di organizzazioni sul tema "Individual atmospheric particles"
1
EGR Cooler Fouling Reduction: A New Method for Assessment in Early Engine Development Phase. SAE International, marzo 2022. http://dx.doi.org/10.4271/022-01-0589.
Testo completoAbstract (sommario):
High pressure EGR provides NOx emission reduction even at low exhaust temperatures. To maintain a safe EGR system operation over a required lifetime, the EGR cooler fouling must not exceed an allowable level, even if the engine is operated under worst-case conditions. A reliable fouling simulation model represents a valuable tool in the engine development process, which validates operating and calibration strategies regarding fouling tendency, helping to avoid fouling issues in a late development phase close to series production. Long-chained hydrocarbons in the exhaust gas essentially impact the fouling layer formation. Therefore, a simulation model requires reliable input data especially regarding mass flow of long-chained hydrocarbons transported into the cooler. There is a huge number of different hydrocarbon species in the exhaust gas, but their individual concentration typically is very low, close to the detection limit of standard in-situ measurement equipment like GC-MS. Therefore, a new measurement and analysis approach has been developed, where the exhaust gas is guided to a metal foam collector, in which HC`s are deposited. The probe is then analyzed in a suited thermogravimetrical system (TGA) in nitrogen atmosphere, temperature range 25°C to 650°C. Analyzing the TGA curve, HC concentration data for 6 different boiling temperature ranges are obtained, provided to an adapted 1-d fouling simulation model. Using these data along with further input parameters like cooler geometry, gas temperature, pressure, flow, particle size distribution and coolant temperature, the simulation model has proven as a suitable tool to predict the fouling and identify engine settings for fouling reduction.