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1
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.
2
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.
3
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.
4
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.
5
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.
6
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.
11
Han, Yan, Lei Ding, Yingping Wang, Haiyang Zheng e Li Fang. "Shape Discrimination of Individual Aerosol Particles Using Light Scattering". Sensors 23, n. 12 (9 giugno 2023): 5464. http://dx.doi.org/10.3390/s23125464.
Testo completoAbstract (sommario):
We established an experimental apparatus by combining polarized light scattering and angle-resolved light scattering measurement technology to rapidly identify the shape of an individual aerosol particle. The experimental data of scattered light of Oleic acid, rod-shaped Silicon dioxide, and other particles with typical shape characteristics were analyzed statistically. To better study the relationship between the shape of particles and the properties of scattered light, the partial least squares discriminant analysis (PLS-DA) method was used to analyze the scattered light of aerosol samples based on the size screening of particles, and the shape recognition and classification method of the individual aerosol particle was established based on the analysis of the spectral data after nonlinear processing and grouping by particle size with the area under the receiver operating characteristic curve (AUC) as reference. The experimental results show that the proposed classification method has a good discrimination ability for spherical, rod-shaped, and other non-spherical particles, which can provide more information for atmospheric aerosol measurement, and has application value for traceability and exposure hazard assessment of aerosol particles.
12
Zhang, G., X. Bi, L. Li, L. Y. Chan, M. Li, X. Wang, G. Sheng, J. Fu e Z. Zhou. "Mixing state of individual submicron carbon-containing particles and their seasonal variation in urban Guangzhou, China". Atmospheric Chemistry and Physics Discussions 12, n. 12 (19 dicembre 2012): 32707–39. http://dx.doi.org/10.5194/acpd-12-32707-2012.
Testo completoAbstract (sommario):
Abstract. Growing evidence suggests that size-resolved mixing state of carbon-containing particles is very critical in determining their optical properties, atmospheric lifetime, and impact on the environment. However, still little is known about the mixing state of particles in urban area of Pearl River Delta (PRD) region, China. To investigate the mixing state of submicron carbon-containing particles, measurements were carried out during spring and fall periods of 2010 using a single particle aerosol mass spectrometer (SPAMS). Approximate 700 000 particles for each period were detected. This is the first report on the size-resolved mixing state of carbon-containing particles by direct observations in PRD region. Cluster analysis of single particle mass spectra was applied to identify carbon-containing particle classes. These classes represented ~80% and ~90% of all the detected particles for spring and fall periods, respectively. Carbon-containing particle classes mainly consisted of biomass/biofuel burning particles (Biomass), organic carbon (OC), fresh elemental carbon (EC-fresh), internally mixed OC and EC (ECOC), internally mixed EC with sulfate (EC-Sulfate), vanadium-containing ECOC (V-ECOC), and amines-containing particles (Amine). In spring, the top three ranked carbon-containing particle classes were ECOC (26.1%), Biomass (23.6%) and OC (10%), respectively. However, the fraction of Biomass particles increased remarkably and predominated (61.0%), while the fraction of ECOC (3.0%) and V-ECOC (0.1%) significantly decreased in fall. To highlight the influence of monsoon on the properties of carbon-containing particles in urban Guangzhou, their size distribution, mixing state, and aerosol acidity were compared between spring and fall seasons. In addition, a case study was also performed to investigate how the formation of fog and haze influenced the mixing state of carbon-containing particles. These results are of importance in understanding atmospheric chemistry and modeling direct and indirect forcing of carbon-containing particles.
13
Jeong, Gi Young, Mi Yeon Park, Konrad Kandler, Timo Nousiainen e Osku Kemppinen. "Mineralogical properties and internal structures of individual fine particles of Saharan dust". Atmospheric Chemistry and Physics 16, n. 19 (4 ottobre 2016): 12397–410. http://dx.doi.org/10.5194/acp-16-12397-2016.
Testo completoAbstract (sommario):
Abstract. Mineral dust interacts with incoming/outgoing radiation, gases, other aerosols, and clouds. The assessment of its optical and chemical impacts requires knowledge of the physical and chemical properties of bulk dust and single particles. Despite the existence of a large body of data from field measurements and laboratory analyses, the internal properties of single dust particles have not been defined precisely. Here, we report on the mineralogical organization and internal structures of individual fine ( < 5 µm) Saharan dust particles sampled at Tenerife, Canary Islands. The bulk of Tenerife dust was composed of clay minerals (81 %), followed by quartz (10 %), plagioclase (3 %), and K-feldspar (2 %). Cross-sectional slices of Saharan dust particles prepared by the focused ion beam technique were analyzed by transmission electron microscopy (TEM) to probe the particle interiors. TEM analysis showed that the most common particle type was clay-rich agglomerate, dominated by illite–smectite series clay minerals with subordinate kaolinite. Submicron grains of iron (hydr)oxides (goethite and hematite) were commonly dispersed through the clay-rich particles. The median total volume of the iron (hydr)oxide grains included in the dust particles was estimated to be about 1.5 % vol. The average iron content of clay minerals, assuming 14 wt % H2O, was determined to be 5.0 wt %. Coarse mineral cores, several micrometers in size, were coated with thin layers of clay-rich agglomerate. Overall, the dust particles were roughly ellipsoidal, with an average axial ratio of 1.4 : 1.0 : 0.5. The mineralogical and structural properties of single Saharan dust particles provide a basis for the modeling of dust radiative properties. Major iron-bearing minerals, such as illite–smectite series clay minerals and iron (hydr)oxides, were commonly submicron- to nano-sized, possibly enhancing their biogeochemical availability to remote marine ecosystems lacking micronutrients.
14
Fu, H., M. Zhang, W. Li, J. Chen, L. Wang, X. Quan e W. Wang. "Morphology, composition and mixing state of individual carbonaceous aerosol in urban Shanghai". Atmospheric Chemistry and Physics 12, n. 2 (16 gennaio 2012): 693–707. http://dx.doi.org/10.5194/acp-12-693-2012.
Testo completoAbstract (sommario):
Abstract. A total of 834 individual aerosol particles were collected during October and November 2010 in urban Shanghai, China. Particles were sampled under different weather and air quality conditions. Morphologies, compositions and mixing states of carbonaceous aerosols were investigated by transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX). Structures of some particles were verified using selected-area electron diffraction (SAED). Among the aerosol particles observed, carbonaceous aerosols were mainly categorized into four types: polymeric organic compound (POC), soot, tar ball, and biogenic particle. Based on the detailed TEM-EDX analysis, most of the particles were coated with secondary organic aerosols (SOA), which commonly formed through condensation or heterogeneous reactions of precursor gases on pre-existing particles. Aged particles were associated with days with low wind velocities, showed complex structures, and were bigger in size. The internally mixed particles of sulphates, organics and soot were encountered frequently. Such internally mixed particles may be preferentially formed during a stagnated air mass during serious pollution events, such as on 13 November. Although relative number counts varied with different species, sulphates (38–71%) and soot (11–22%) constituted the most dominant species observed in the samples. However, soil-derived particles (68%) were relatively more frequently observed on the sample collected on 12 November during a dust storm.
15
Fu, Yuzhen, Qinhao Lin, Guohua Zhang, Yuxiang Yang, Yiping Yang, Xiufeng Lian, Long Peng et al. "Impact of in-cloud aqueous processes on the chemical compositions and morphology of individual atmospheric aerosols". Atmospheric Chemistry and Physics 20, n. 22 (20 novembre 2020): 14063–75. http://dx.doi.org/10.5194/acp-20-14063-2020.
Testo completoAbstract (sommario):
Abstract. The composition, morphology, and mixing structure of individual cloud residues (RES) and interstitial particles (INT) at a mountaintop site were investigated. Eight types of particles were identified, including sulfate-rich (S-rich), S-organic matter (OM), aged soot, aged mineral dust, aged fly ash, aged metal, refractory, and aged refractory mixture. A shift of dominant particle types from S-rich (29 %) and aged soot (27 %) in the INT to aged refractory mixture (23 %) and S-OM (22 %) in the RES is observed. In particular, particles with organic shells are enriched in the RES (27 %) relative to the INT (12 %). Our results highlight that the formation of more oxidized organic matter in the cloud contributes to the existence of organic shells after cloud processing. The fractal dimension (Df), a morphologic parameter to represent the branching degree of particles, for soot particles in the RES (1.82 ± 0.12) is lower than that in the INT (2.11 ± 0.09), which indicates that in-cloud processes may result in less compact soot. This research emphasizes the role of in-cloud processes in the chemistry and microphysical properties of individual particles. Given that organic coatings may determine the particle hygroscopicity, activation ability, and heterogeneous chemical reactivity, the increase of OM-shelled particles upon in-cloud processes should have considerable implications.
16
Zhang, G., X. Bi, L. Li, L. Y. Chan, M. Li, X. Wang, G. Sheng, J. Fu e Z. Zhou. "Mixing state of individual submicron carbon-containing particles during spring and fall seasons in urban Guangzhou, China: a case study". Atmospheric Chemistry and Physics 13, n. 9 (7 maggio 2013): 4723–35. http://dx.doi.org/10.5194/acp-13-4723-2013.
Testo completoAbstract (sommario):
Abstract. Growing evidence suggests that the size-resolved mixing state of carbon-containing particles is very critical in determining their optical properties, atmospheric lifetime, and impact on the environment. However, still little is known about the mixing state of particles in the urban area of the Pearl River Delta (PRD) region, China. To investigate the mixing state of submicron carbon-containing particles, measurements were carried out during spring and fall periods of 2010 using a single-particle aerosol mass spectrometer (SPAMS). Approximately 700 000 particles for each period were detected. This is the first report on the size-resolved mixing state of carbon-containing particles by direct observations in the PRD region. Cluster analysis of single-particle mass spectra was applied to identify carbon-containing particle classes. These classes represented ~80% and ~90% of all the detected particles for spring and fall periods, respectively. Carbon-containing particle classes mainly consisted of biomass/biofuel burning particles (Biomass), organic carbon (OC), fresh elemental carbon (EC-fresh), internally mixed OC and EC (ECOC), internally mixed EC with sulfate (EC-Sulfate), vanadium-containing ECOC (V-ECOC), and amines-containing particles (Amine). In spring, the top three ranked carbon-containing particle classes were ECOC (26.1%), Biomass (23.6%) and OC (10%), respectively. However, the fraction of Biomass particles increased remarkably and predominated (61.0%), while the fraction of ECOC (3.0%) and V-ECOC (0.1%) significantly decreased in fall. To highlight the influence of monsoon on the properties of carbon-containing particles in urban Guangzhou, their size distributions, mixing state, and aerosol acidity were compared between spring and fall seasons. In addition, a case study was also performed to investigate how the formation of fog and haze influenced the mixing state of carbon-containing particles. These results could improve our understanding of the mixing state of carbon-containing particles, and may also be helpful in modeling the climate forcing of aerosol in the PRD region.
17
Fierce, Laura, Nicole Riemer e Tami C. Bond. "Toward Reduced Representation of Mixing State for Simulating Aerosol Effects on Climate". Bulletin of the American Meteorological Society 98, n. 5 (1 maggio 2017): 971–80. http://dx.doi.org/10.1175/bams-d-16-0028.1.
Testo completoAbstract (sommario):
Abstract Atmospheric aerosols affect Earth’s energy budget, and hence its climate, by scattering and absorbing solar radiation and by altering the radiative properties and the lifetime of clouds. These two major aerosol effects depend on the optical properties and the cloud-nucleating ability of individual particles, which, in turn, depend on the distribution of components among individual particles, termed the “aerosol mixing state.” Global models have moved toward including aerosol schemes to represent the evolution of particle characteristics, but individual particle properties cannot be resolved in global-scale simulations. Instead, models approximate the aerosol mixing state. The errors in climate-relevant aerosol properties introduced by such approximations may be large but have not yet been well quantified. This paper quantitatively addresses the question of to what extent the aerosol mixing state must be resolved to adequately represent the optical properties and cloud-nucleating properties of particle populations. Using a detailed benchmarking model to simulate gas condensation and particle coagulation, we show that, after the particles evolve in the atmosphere, simple mixing-state representations are sufficient for modeling cloud condensation nuclei concentrations, and we quantify the mixing time scale that characterizes this transformation. In contrast, a detailed representation of the mixing state is required to model aerosol light absorption, even for populations that are fully mixed with respect to their hygroscopic properties.
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Geng, H., J. Y. Ryu, S. Maskey, H. J. Jung e C. U. Ro. "Characterisation of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique". Atmospheric Chemistry and Physics 11, n. 3 (15 febbraio 2011): 1327–37. http://dx.doi.org/10.5194/acp-11-1327-2011.
Testo completoAbstract (sommario):
Abstract. A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyse individual aerosol particles collected in Incheon, Korea on 13–18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall 3600 individual particles in PM2.5-10 and PM1.0-2.5 fractions from 12 aerosol samples collected on haze and non-haze days were analysed. The analysed particles were classified, based on their X-ray spectral data together with their secondary electron images. The major particle types included organic carbon (OC), elemental carbon (EC), sea-salt, mineral dust (such as aluminosilicate, SiO2, CaCO3/CaMgCO3, etc.), (NH4)2SO4/NH4HSO4-containing, K-containing, Fe-rich and fly ash particles. Their relative number abundance results showed that OC particles were significantly increased while sea-salts and mineral dust particles were significantly decreased (especially in PM1.0-2.5 fraction) when haze occurred. For the other particle types (except Fe-rich particles in PM2.5-10 fraction), there were no significant differences in their relative abundances between haze and non-haze samples. On non-haze days, the nitrate-containing reacted sea-salt and mineral dust particles in PM1.0-2.5 fraction significantly outnumbered the sulfate-containing ones, whereas it was the reverse on haze days, implying that on haze days there were special sources or formation mechanisms for fine aerosol particles (≤2.5 μm in aerodynamic diameter). The emission of air pollutants from motor vehicles and stagnant meteorological conditions, such as low wind speed and high relative humidity, might be responsible for the elevated level of OC particles on haze days.
19
Lee, Hansol D., e Alexei V. Tivanski. "Atomic Force Microscopy: An Emerging Tool in Measuring the Phase State and Surface Tension of Individual Aerosol Particles". Annual Review of Physical Chemistry 72, n. 1 (20 aprile 2021): 235–52. http://dx.doi.org/10.1146/annurev-physchem-090419-110133.
Testo completoAbstract (sommario):
Atmospheric aerosols are suspended particulate matter of varying composition, size, and mixing state. Challenges remain in understanding the impact of aerosols on the climate, atmosphere, and human health. The effect of aerosols depends on their physicochemical properties, such as their hygroscopicity, phase state, and surface tension. These properties are dynamic with respect to the highly variable relative humidity and temperature of the atmosphere. Thus, experimental approaches that permit the measurement of these dynamic properties are required. Such measurements also need to be performed on individual, submicrometer-, and supermicrometer-sized aerosol particles, as individual atmospheric particles from the same source can exhibit great variability in their form and function. In this context, this review focuses on the recent emergence of atomic force microscopy as an experimental tool in physical, analytical, and atmospheric chemistry that enables such measurements. Remaining challenges are noted and suggestions for future studies are offered.
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Ono, Kohei, Yuki Mizushima, Masaki Furuya, Ryota Kunihisa, Nozomu Tsuchiya, Takeshi Fukuma, Ayumi Iwata e Atsushi Matsuki. "Direct Measurement of Adhesion Force of Individual Aerosol Particles by Atomic Force Microscopy". Atmosphere 11, n. 5 (10 maggio 2020): 489. http://dx.doi.org/10.3390/atmos11050489.
Testo completoAbstract (sommario):
A new method, namely, force–distance curve mapping, was developed to directly measure the adhesion force of individual aerosol particles by atomic force microscopy. The proposed method collects adhesion force from multiple points on a single particle. It also takes into account the spatial distribution of the adhesion force affected by topography (e.g., the variation in the tip angle relative to the surface, as well as the force imposed upon contact), thereby enabling the direct and quantitative measurement of the adhesion force representing each particle. The topographic effect was first evaluated by measuring Polystyrene latex (PSL) standard particles, and the optimized method was then applied on atmospherically relevant model dust particles (quartz, ATD, and CJ-1) and inorganic particles (ammonium sulfate and artificial sea salt) to inter-compare the adhesion forces among different aerosol types. The method was further applied on the actual ambient aerosol particles collected on the western coast of Japan, when the region was under the influence of Asian dust plume. The ambient particles were classified into sea salt (SS), silicate dust, and Ca-rich dust particles based on individual particle analysis (micro-Raman or Scanning Electron Microscope/Energy Dispersive X-ray Spectroscopy (SEM-EDX)). Comparable adhesion forces were obtained from the model and ambient particles for both SS and silicate dust. Although dust particles tended to show smaller adhesion forces, the adhesion force of Ca-rich dust particles was larger than the majority of silicate dust particles and was comparable with the inorganic salt particles. These results highlight that the original chemical composition, as well as the aging process in the atmosphere, can create significant variation in the adhesion force among individual particles. This study demonstrates that force–distance curve mapping can be used as a new tool to quantitatively characterize the physical properties of aerosol particles on an individual basis.
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Pietras, Bartłomiej Gabriel. "The Origin of Dust Particles in Atmospheric Air in Krakow (Poland) (Atmospheric Background)". Land 11, n. 2 (19 gennaio 2022): 155. http://dx.doi.org/10.3390/land11020155.
Testo completoAbstract (sommario):
For several decades air pollution in Krakow has been a serious and an unresolved environmental and social problem. The causes of high concentration of particulate matter, such as PM10 and PM2.5 in Krakow are both natural and anthropogenic. Nevertheless, the sources of dust pollution have not been fully determined yet. The main source of dust in Krakow is local emissions, however, particles from adjacent areas might also contribute significantly to the pollution. Transboundary dust should also be taken into account while investigating the problem. The aim of the study is to determine what type of particles are present in the atmospheric air in Krakow and to make an attempt at determining their sources. The analytical method applied in the study was the Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS). In addition, the HYSPLIT model was used for data analysis and for determination of particles source areas. The analysis of individual dust particles indicates that they are very diverse in terms of chemical composition and particle size. Moreover, the analysis shows that the particles are of various origins, such as anthropogenic and natural, as well as that some of them are formed in the air by chemical reactions. The analysis of particulate matter demonstrates that the majority of it consists of particles with a diameter of less than 1 μm. The concentration of very fine soot particles (nanoparticles) seems to be the highest, however, spherical aluminosilicate particles such as iron and titanium oxides are also found.
22
Turpin, Barbara J., Po-Fu Huang, Amy Roos e Peter H. McMurry. "Elemental analysis of single atmospheric particles influencing visibility at the grand canyon". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 1124–25. http://dx.doi.org/10.1017/s0424820100151453.
Testo completoAbstract (sommario):
Collection and preservation strategies and a routine analysis procedure were developed for elemental analysis of individual atmospheric particles using a scanning-transmission electron microscope (STEM) equipped with a super ultra-thin window energy dispersive x-ray detector. These techniques were applied to airborne particles collected at Meadview, AZ, a remote site just downriver of the Grand Canyon. Collection, preservation and beam damage issues of concern in electron microscopic analysis of atmospheric particles will be discussed. Aerosol compositions are usually determined from bulk particle measurements, and it is assumed that compounds are either internally mixed (all present in each particle) or externally mixed (particles each contain a single compound). Insight into the microscopic mixing characteristics of atmospheric aerosols will ultimately further the understanding of atmospheric particle transformation, visibility degradation, and the fate of airborne pollutants.Particles were collected in the summer of 1992 in three size fractions (1.0-0.5 μm, 0.5-0.26 μm, 0.26-0.12 μm in diameter) using a Hering Low Pressure Impactor and a 250 Å thick silver film substrate supported by a silver TEM grid.
23
Lin, Qinhao, Guohua Zhang, Long Peng, Xinhui Bi, Xinming Wang, Fred J. Brechtel, Mei Li et al. "In situ chemical composition measurement of individual cloud residue particles at a mountain site, southern China". Atmospheric Chemistry and Physics 17, n. 13 (12 luglio 2017): 8473–88. http://dx.doi.org/10.5194/acp-17-8473-2017.
Testo completoAbstract (sommario):
Abstract. To investigate how atmospheric aerosol particles interact with chemical composition of cloud droplets, a ground-based counterflow virtual impactor (GCVI) coupled with a real-time single-particle aerosol mass spectrometer (SPAMS) was used to assess the chemical composition and mixing state of individual cloud residue particles in the Nanling Mountains (1690 m a. s. l. ), southern China, in January 2016. The cloud residues were classified into nine particle types: aged elemental carbon (EC), potassium-rich (K-rich), amine, dust, Pb, Fe, organic carbon (OC), sodium-rich (Na-rich) and Other. The largest fraction of the total cloud residues was the aged EC type (49.3 %), followed by the K-rich type (33.9 %). Abundant aged EC cloud residues that mixed internally with inorganic salts were found in air masses from northerly polluted areas. The number fraction (NF) of the K-rich cloud residues increased within southwesterly air masses from fire activities in Southeast Asia. When air masses changed from northerly polluted areas to southwesterly ocean and livestock areas, the amine particles increased from 0.2 to 15.1 % of the total cloud residues. The dust, Fe, Pb, Na-rich and OC particle types had a low contribution (0.5–4.1 %) to the total cloud residues. Higher fraction of nitrate (88–89 %) was found in the dust and Na-rich cloud residues relative to sulfate (41–42 %) and ammonium (15–23 %). Higher intensity of nitrate was found in the cloud residues relative to the ambient particles. Compared with nonactivated particles, nitrate intensity decreased in all cloud residues except for dust type. To our knowledge, this study is the first report on in situ observation of the chemical composition and mixing state of individual cloud residue particles in China.
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Li, W. J., D. Z. Zhang, L. Y. Shao, S. Z. Zhou e W. X. Wang. "Individual particle analysis of aerosols collected under haze and non-haze conditions at a high-elevation mountain site in the North China plain". Atmospheric Chemistry and Physics 11, n. 22 (24 novembre 2011): 11733–44. http://dx.doi.org/10.5194/acp-11-11733-2011.
Testo completoAbstract (sommario):
Abstract. The North China plain is a region with megacities and huge populations. Aerosols over the highly polluted area have a significant impact on the regional and global climate. In order to investigate the physical and chemical characteristics of aerosol particles in elevated layers there, observations were carried out at the summit of Mt. Tai (1534 m a.s.l.) from 19 to 28 April, 2010, when the air masses were advected from the east (phase-I: 19–21 April), from the south (phase-II: 22–25 April), and from the northwest (phase-III: 26–28 April). Individual aerosol particles were identified with transmission electron microscopy (TEM), new particle formation (NPF) and growth events were monitored by a wide-range particle spectrometer, and ion concentrations in PM2.5 were analyzed. During phase-I and phase-II, haze layers caused by anthropogenic pollution were observed, and a high percentage of particles were sulfur-rich (47–49%). In phase-III, the haze disappeared due to the intrusion of cold air from the northwest, and mineral dust particles from deserts were dominant (43%). NPF followed by particle growth during daytime was more pronounced on hazy than on clear days. Particle growth during daytime resulted in an increase of particle geometric mean diameter from 10–22 nm in the morning to 56–96 nm in the evening. TEM analysis suggests that sulfuric acid and secondary organic compounds should be important factors for particle nucleation and growth. However, the presence of fine anthropogenic particles (e.g., soot, metal, and fly ash) embedded within S-rich particles indicates that they could weaken NPF and enhance particle growth through condensation and coagulation. Abundant mineral particles in phase-III likely suppressed the NPF processes because they supplied sufficient area on which acidic gases or acids condensed.
25
Pfeifer, Sascha, Thomas Müller, Kay Weinhold, Nadezda Zikova, Sebastiao Martins dos Santos, Angela Marinoni, Oliver F. Bischof et al. "Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution". Atmospheric Measurement Techniques 9, n. 4 (7 aprile 2016): 1545–51. http://dx.doi.org/10.5194/amt-9-1545-2016.
Testo completoAbstract (sommario):
Abstract. Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates, particle sizing, and the unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10 % to 20 % for particles in the range of 0.9 up to 3 µm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 µm in aerodynamic diameter should only be used with caution. For particles larger than 3 µm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. Particularly this uncertainty of the particle number size distribution must be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5–3 µm is needed.
26
Pfeifer, S., T. Müller, K. Weinhold, N. Zikova, S. Santos, A. Marinoni, O. F. Bischof et al. "Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution". Atmospheric Measurement Techniques Discussions 8, n. 11 (3 novembre 2015): 11513–32. http://dx.doi.org/10.5194/amtd-8-11513-2015.
Testo completoAbstract (sommario):
Abstract. Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates accuracy, particle sizing, and unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10–20 % for particles in the range of 0.9 up to 3 μm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 μm in aerodynamic diameter should be only used with caution. For particles larger than 3 μm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. This uncertainty of the particle number size distribution has especially to be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5–3 μm is needed.
27
Suzuki, K., T. Takii, B. Tomiyasu e Y. Nihei. "Characterization of individual complex particles in urban atmospheric environment". Applied Surface Science 252, n. 19 (luglio 2006): 7022–25. http://dx.doi.org/10.1016/j.apsusc.2006.02.173.
Testo completo
28
SEMENIUK, T., M. WISE, S. MARTIN, L. RUSSELL e P. BUSECK. "Water uptake characteristics of individual atmospheric particles having coatings". Atmospheric Environment 41, n. 29 (settembre 2007): 6225–35. http://dx.doi.org/10.1016/j.atmosenv.2007.04.001.
Testo completo
29
Ghosal, Sutapa, Peter K. Weber e Alexander Laskin. "Spatially resolved chemical imaging of individual atmospheric particles using nanoscale imaging mass spectrometry: insight into particle origin and chemistry". Anal. Methods 6, n. 8 (2014): 2444–51. http://dx.doi.org/10.1039/c3ay42012d.
Testo completoAbstract (sommario):
Knowledge of the spatially resolved composition of atmospheric particles is essential for differentiating between their surface versus bulk chemistry and understanding particle reactivity and the potential environmental impact.
30
Schumann, Ulrich, Robert Baumann, Darrel Baumgardner, Sarah T. Bedka, David P. Duda, Volker Freudenthaler, Jean-Francois Gayet et al. "Properties of individual contrails: a compilation of observations and some comparisons". Atmospheric Chemistry and Physics 17, n. 1 (10 gennaio 2017): 403–38. http://dx.doi.org/10.5194/acp-17-403-2017.
Testo completoAbstract (sommario):
Abstract. Mean properties of individual contrails are characterized for a wide range of jet aircraft as a function of age during their life cycle from seconds to 11.5 h (7.4–18.7 km altitude, −88 to −31 °C ambient temperature), based on a compilation of about 230 previous in situ and remote sensing measurements. The airborne, satellite, and ground-based observations encompass exhaust contrails from jet aircraft from 1972 onwards, as well as a few older data for propeller aircraft. The contrails are characterized by mean ice particle sizes and concentrations, extinction, ice water content, optical depth, geometrical depth, and contrail width. Integral contrail properties include the cross-section area and total number of ice particles, total ice water content, and total extinction (area integral of extinction) per contrail length. When known, the contrail-causing aircraft and ambient conditions are characterized. The individual datasets are briefly described, including a few new analyses performed for this study, and compiled together to form a contrail library (COLI). The data are compared with results of the Contrail Cirrus Prediction (CoCiP) model. The observations confirm that the number of ice particles in contrails is controlled by the engine exhaust and the formation process in the jet phase, with some particle losses in the wake vortex phase, followed later by weak decreases with time. Contrail cross sections grow more quickly than expected from exhaust dilution. The cross-section-integrated extinction follows an algebraic approximation. The ratio of volume to effective mean radius decreases with time. The ice water content increases with increasing temperature, similar to non-contrail cirrus, while the equivalent relative humidity over ice saturation of the contrail ice mass increases at lower temperatures in the data. Several contrails were observed in warm air above the Schmidt–Appleman threshold temperature. The emission index of ice particles, i.e., the number of ice particles formed in the young contrail per burnt fuel mass, is estimated from the measured concentrations for estimated dilution; maximum values exceed 1015 kg−1. The dependence of the data on the observation methods is discussed. We find no obvious indication for significant contributions from spurious particles resulting from shattering of ice crystals on the microphysical probes.
31
Li, W. J., e L. Y. Shao. "Observation of nitrate coatings on atmospheric mineral dust particles". Atmospheric Chemistry and Physics Discussions 8, n. 6 (14 novembre 2008): 19249–72. http://dx.doi.org/10.5194/acpd-8-19249-2008.
Testo completoAbstract (sommario):
Abstract. Nitrate compounds have recently received much attention because of their ability to alter the hygroscopic properties and cloud condensation nuclei (CCN) activity of mineral dust particles in the atmosphere. However, very little is known about specific characteristics of nitrate-coated mineral particles in an individual particle scale in field study. The sample collection was conducted during brown haze and dust episodes occurred between 24 May and 21 June 2007 in Beijing, northern China. The sizes, morphologies, and compositions of mineral dust particles together with their coatings were analyzed using transmission electron microscopy (TEM). 92% of the internally mixed mineral particles analyzed are covered with Ca-, Mg-, and Na-rich coatings, and 8% are associated with K- and S-rich coatings. The major coatings contain Ca, Mg, O, and N with minor amounts of S and Cl, suggesting that they are possibly nitrates mixed with less sulfates and chlorides. These nitrate coatings strongly relate with the presence of alkaline mineral components (e.g., calcite and dolomite) within individual mineral particles. Calcium sulfate particles with the diameter from 10 to 500 nm were also detected within Ca(NO3)2 and Mg(NO3)2 coatings. Our results indicate that mineral particles in brown haze episodes were involved in atmospheric heterogeneous reactions with two or more acidic gases (e.g., SO2, NO2, HCl, and HNO3). Mineral particles that acquire hygroscopic coatings tend to be more spherical and larger. Such changes enhance their light scattering and CCN activity, both of which have cooling effects on the climate.
32
Wang, Wenhua, Longyi Shao, Claudio Mazzoleni, Yaowei Li, Simone Kotthaus, Sue Grimmond, Janarjan Bhandari et al. "Measurement report: Comparison of wintertime individual particles at ground level and above the mixed layer in urban Beijing". Atmospheric Chemistry and Physics 21, n. 7 (7 aprile 2021): 5301–14. http://dx.doi.org/10.5194/acp-21-5301-2021.
Testo completoAbstract (sommario):
Abstract. Beijing has been suffering from frequent severe air pollution events, with concentrations affected significantly by the mixed-layer height. Major efforts have been made to study the physico-chemical properties, compositions, and sources of aerosol particles at ground level. However, little is known about the morphology, elemental composition, and mixing state of aerosol particles above the mixed layer. In this work, we collected individual aerosol particles simultaneously at ground level (2 m above ground) and above the mixed layer in urban Beijing (within the Atmospheric Pollution and Human Health in a Chinese Megacity, APHH-Beijing, 2016 winter campaign). The particles were analyzed offline by transmission electron microscopy coupled with energy dispersive X-ray spectroscopy. Our results showed that the relative number contribution of mineral particles to all measured particles was much higher during non-haze periods (42.5 %) than haze periods (18.1 %); in contrast, internally mixed particles contributed more during haze periods (21.9 %) than non-haze periods (7.2 %) at ground level. In addition, more mineral particles were found at ground level than above the mixed-layer height. Around 20 % of individual particles showed core–shell structures during haze periods, whereas only a few core–shell particles were observed during non-haze periods (2 %). The results showed that the particles above the mixed layer were more aged, with a larger proportion of organic particles originating from coal combustion. Our results indicate that a large fraction of the airborne particles above the mixed layer come from surrounding areas influenced by coal combustion activities. This source contributes to the surface particle concentrations in Beijing when polluted air is mixed down to the ground level.
33
Huffman, Donald R., Benjamin E. Swanson e J. Alex Huffman. "A wavelength-dispersive instrument for characterizing fluorescence and scattering spectra of individual aerosol particles on a substrate". Atmospheric Measurement Techniques 9, n. 8 (23 agosto 2016): 3987–98. http://dx.doi.org/10.5194/amt-9-3987-2016.
Testo completoAbstract (sommario):
Abstract. We describe a novel, low-cost instrument to acquire both elastic and inelastic (fluorescent) scattering spectra from individual supermicron-size particles in a multi-particle collection on a microscope slide. The principle of the device is based on a slitless spectroscope that is often employed in astronomy to determine the spectra of individual stars in a star cluster but had not been applied to atmospheric particles. Under excitation, most commonly by either a 405 nm diode laser or a UV light-emitting diode (LED), fluorescence emission spectra of many individual particles can be determined simultaneously. The instrument can also acquire elastic scattering spectra from particles illuminated by a white-light source. The technique also provides the ability to detect and rapidly estimate the number fraction of fluorescent particles that could contaminate a collection of non-fluorescent material, even without analyzing full spectra. Advantages and disadvantages of using black-and-white cameras compared to color cameras are given. The primary motivation for this work has been to develop an inexpensive technique to characterize fluorescent biological aerosol particles, especially particles such as pollen and mold spores that can cause allergies. An example of an iPhone-enabled device is also shown as a means for collecting data on biological aerosols at lower cost or by utilizing citizen scientists for expanded data collection.
34
Gaie-Levrel, F., S. Perrier, E. Perraudin, C. Stoll, N. Grand e M. Schwell. "Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies". Atmospheric Measurement Techniques 5, n. 1 (26 gennaio 2012): 225–41. http://dx.doi.org/10.5194/amt-5-225-2012.
Testo completoAbstract (sommario):
Abstract. A single particle instrument was developed for real-time analysis of organic aerosol. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized by using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE ranges from 0.1 to 90% for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. During optical detection, particle scattered light from the two diode lasers, is detected by two photomultipliers and the detected signals are used to trigger UV excimer laser (λ = 248 nm) used for one-step laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 × 10−15 kg (∼4 × 103 molecules). DOP particles were also used to test the overall operation of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first application of the instrument. Single particle mass spectra were obtained with an effective hit rate of 8%. Some of these mass spectra were found to be very different from one particle to another possibly reflecting chemical differences within the investigated indene SOA particles. Our study shows that an exhaustive statistical analysis, over hundreds of particles, and adapted reference mass spectra are further needed to understand the chemical meaning of single particle mass spectra of chemically complex submicrometer-sized organic aerosols.
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Gaie-Levrel, F., S. Perrier, E. Perraudin, C. Stoll, N. Grand e M. Schwell. "Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies". Atmospheric Measurement Techniques Discussions 4, n. 4 (4 luglio 2011): 4165–208. http://dx.doi.org/10.5194/amtd-4-4165-2011.
Testo completoAbstract (sommario):
Abstract. A single particle instrument has been developed for real-time analysis of organic aerosols. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE is ranging from 0.1 to 90 % for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. Scattered light is detected by two photomultipliers and the detected signals are used to trigger a UV excimer laser (λ = 248 nm) used for laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 attograms. DOP particles were also used to test the overall functioning of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first scientific application of the instrument. Single particle mass spectra are obtained with a global hit rate of 10 %. They are found to be very different from one particle to another, reflecting chemical differences of the analyzed particles, and most of the detected mass peaks are attributed to oxidized products of indene.
36
Du, Xubing, Qinhui Xie, Qing Huang, Xuan Li, Junlin Yang, Zhihui Hou, Jingjing Wang et al. "Development and characterization of a high-performance single-particle aerosol mass spectrometer (HP-SPAMS)". Atmospheric Measurement Techniques 17, n. 3 (13 febbraio 2024): 1037–50. http://dx.doi.org/10.5194/amt-17-1037-2024.
Testo completoAbstract (sommario):
Abstract. This study describes a high-performance single-particle mass spectrometry (HP-SPAMS) design in detail. The comprehensive improvements in the injection system, optical sizing system, mass spectrometry, and data acquisition system have improved particle detection efficiency and chemical analysis. The combination of an aerodynamic particle concentrator (APC) system and a wide range of aerodynamic lenses (ADLs) enables the concentration of particles in the 100–5000 nm range. Using an APC increases the instrument inlet flow by a factor of 3–5. The ion delayed-exaction technology of bipolar time-of-flight mass spectrometry improves the mass resolution by 2–3 times, allowing the differentiation of isobaric ions of different substances. Moreover, the four-channel data acquisition technology greatly enhances the dynamic range of mass spectrometry. The improved HP-SPAMS enhances the overall capability of the instrument in terms of particle detection number and scattering efficiency. Moreover, it improves accuracy and sensitivity for component identification of individual particles. The experimental performance of HP-SPAMS shows that the scattering efficiency of polystyrene latex microspheres is almost 70 %–100 % in the range of 300–3000 nm. Compared to the previous SPAMS, HP-SPAMS has a larger inlet flow rate and scattering efficiency and a higher laser frequency, which makes HP-SPAMS increase the effective number of particles detected and improve the temporal resolution of detection. For the analysis of individual particles, HP-SPAMS achieves an average mass spectral resolution of 2500 at m/z 208, which helps distinguish between most organic fragment ions and metal ions and facilitates the analysis of complex aerosol particles. For the analysis of individual particles, the increased resolution of the HP-SPAMS contributes to the differentiation of most organic fragment ions and metal ions and facilitates the evaluation of complex aerosol particles, in the case of atmospheric lead-containing particles. The improved detection efficiency and chemical analysis capability of HP-SPAMS will be of great importance for low-concentration aerosol detection and complex aerosol component analysis.
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Russell, Philip A. "The Analyses of Anthropogenic Atmospheric Particulates by EM". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 2 (12 agosto 1990): 547. http://dx.doi.org/10.1017/s0424820100136349.
Testo completoAbstract (sommario):
This presentation will summarize fourteen years of research on the physical and chemical nature of particulates suspended in the earths atmosphere utilizing scanning electron microscopy and, to a lesser extent, transmission electron microscopy. Topics to be discussed include (1) the rationale for using electron microscopy to study airborne particulates, (2) methods for collecting airborne particulates, (3) methods of analysis and (4) a summary of results. Examples will demonstrate how conclusions about the nature and source of collected particles can differ between bulk sample analyses and discrete particle analyses. Without the input from discrete particle analyses, bulk analytical techniques may produce serious errors in the apportionment of airborne particulates to specific sources.The scanning electron microscope (SEM) and transmission electron microscopy (TEM) have proven themselves to be the preferred instruments to use in the study of discrete fine particles because they permit sufficient resolution and analytical capabilities to examine the structure and chemistry of individual particles less than a few micrometers in diameter.
38
Chi, J. W., W. J. Li, D. Z. Zhang, J. C. Zhang, Y. T. Lin, X. J. Shen, J. Y. Sun et al. "Sea salt aerosols as a reactive surface for inorganic and organic acidic gases in the Arctic troposphere". Atmospheric Chemistry and Physics 15, n. 19 (12 ottobre 2015): 11341–53. http://dx.doi.org/10.5194/acp-15-11341-2015.
Testo completoAbstract (sommario):
Abstract. Sea salt aerosols (SSA) are dominant particles in the Arctic atmosphere and determine the polar radiative balance. SSA react with acidic pollutants that lead to changes in physical and chemical properties of their surface, which in turn alter their hygroscopic and optical properties. Transmission electron microscopy with energy-dispersive X-ray spectrometry was used to analyze morphology, composition, size, and mixing state of individual SSA at Ny-Ålesund, Svalbard, in summertime. Individual fresh SSA contained cubic NaCl coated by certain amounts of MgCl2 and CaSO4. Individual partially aged SSA contained irregular NaCl coated by a mixture of NaNO3, Na2SO4, Mg(NO3)2, and MgSO4. The comparison suggests the hydrophilic MgCl2 coating in fresh SSA likely intrigued the heterogeneous reactions at the beginning of SSA and acidic gases. Individual fully aged SSA normally had Na2SO4 cores and an amorphous coating of NaNO3. Elemental mappings of individual SSA particles revealed that as the particles ageing Cl gradually decreased, the C, N, O, and S content increased. 12C- mapping from nanoscale secondary ion mass spectrometry indicates that organic matter increased in the aged SSA compared with the fresh SSA. 12C- line scan further shows that organic matter was mainly concentrated on the aged SSA surface. These new findings indicate that this mixture of organic matter and NaNO3 on particle surfaces likely determines their hygroscopic and optical properties. These abundant SSA as reactive surfaces adsorbing inorganic and organic acidic gases can shorten acidic gas lifetime and influence the possible gaseous reactions in the Arctic atmosphere, which need to be incorporated into atmospheric chemical models in the Arctic troposphere.
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Niemi, J. V., S. Saarikoski, H. Tervahattu, T. Mäkelä, R. Hillamo, H. Vehkamäki, L. Sogacheva e M. Kulmala. "Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis". Atmospheric Chemistry and Physics 6, n. 12 (3 novembre 2006): 5049–66. http://dx.doi.org/10.5194/acp-6-5049-2006.
Testo completoAbstract (sommario):
Abstract. Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode (PM1~16 µg m−3, backward air mass trajectories from south-east), intermediate period (PM1~5 µg m−3, backtrajectories from north-east) and clean period (PM1~2 µg m−3, backtrajectories from north-west/north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM0.2–1 and PM1–3.3 size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM0.2–1 samples were 1) soot and 2) (ammonium)sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM0.2–1 samples were 0–12% and 83–97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high (26–48%) in the PM1–3.3 and PM3.3–11 samples, while the PM0.2–1 and PM1–3.3 samples contained elevated proportions of silicates (22–33%), metal oxides/hydroxides (1–9%) and tar balls (1–4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM1–3.3 samples contained mainly sea salt particles (67–89%) with a variable rate of Cl substitution (mainly by NO3−). During the intermediate period, the PM1–3.3 sample contained porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments (probably also biological origin) were highest in the PM3.3–11 samples (0–81% and 0–22%, respectively). The origin of different particle types and the effect of aging processes on particle composition and their hygroscopic and optical properties are discussed.
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Martínez-Villegas, Israel, Alma G. Mora-García, Haideé Ruiz-Luna, John McKelliget, Carlos A. Poblano-Salas, Juan Muñoz-Saldaña e Gerardo Trápaga-Martínez. "Swirling Effects in Atmospheric Plasma Spraying Process: Experiments and Simulation". Coatings 10, n. 4 (15 aprile 2020): 388. http://dx.doi.org/10.3390/coatings10040388.
Testo completoAbstract (sommario):
Experimental evidence of swirling effects in 3D trajectories of in-flight particles is presented based on static and dynamic footprints analysis as a function of stand-off distance of Al2O3 deposited employing a Metco-9MB torch. Swirling effects were validated with a proprietary computational fluid dynamics (CFD) code that considers an argon-hydrogen plasma stream, in-flight particles trajectories, both creating the spray cone, and particle impact to form a footprint on a fixed substrate located at different distances up to 120 mm. Static and dynamic footprints showed that swirl produces a slight deviation of individual particle trajectories and thus footprint rotation, which may affect coating characteristics.
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Cheng, Zezhen, Megan Morgenstern, Bo Zhang, Matthew Fraund, Nurun Nahar Lata, Rhenton Brimberry, Matthew A. Marcus et al. "Particle phase-state variability in the North Atlantic free troposphere during summertime is determined by atmospheric transport patterns and sources". Atmospheric Chemistry and Physics 22, n. 13 (13 luglio 2022): 9033–57. http://dx.doi.org/10.5194/acp-22-9033-2022.
Testo completoAbstract (sommario):
Abstract. Free tropospheric aerosol particles have important but poorly constrained climate effects due to transformations of their physicochemical properties during long-range transport. In this study, we investigate the chemical composition and provide an overview of the phase states of individual particles that have undergone long-range transport over the North Atlantic Ocean in June and July 2014, 2015, and 2017 to the Observatory of Mount Pico (OMP) in the Azores. The OMP is an ideal site for studying long-range-transported free tropospheric particles because local emissions have a negligible influence and contributions from the boundary layer are rare. We used the FLEXible PARTicle Lagrangian particle dispersion model (FLEXPART) to determine the origins and transport trajectories of sampled air masses and found that most of them originated from North America and recirculated over the North Atlantic Ocean. The FLEXPART analysis showed that the sampled air masses were highly aged (average plume age >10 d). Size-resolved chemical compositions of individual particles were probed using computer-controlled scanning electron microscopy with an energy-dispersive X-ray spectrometer (CCSEM-EDX) and scanning transmission X-ray microscopy with near-edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS). CCSEM-EDX results showed that the most abundant particle types were carbonaceous (∼ 29.9 % to 82.0 %), sea salt (∼ 0.3 % to 31.6 %), and sea salt with sulfate (∼ 2.4 % to 31.5 %). We used a tilted stage interfaced within an environmental scanning electron microscope (ESEM) to determine the phase states of individual submicron particles. We found that most particles (∼ 47 % to 99 %) were in the liquid state at the time of collection due to inorganic inclusions. Moreover, we also observed substantial fractions of solid and semisolid particles (∼ 0 % to 30 % and ∼ 1 % to 42 %, respectively) during different transport patterns and events, reflecting the particles' phase-state variability for different atmospheric transport events and sources. Combining phase state measurements with FLEXPART CO tracer analysis, we found that wildfire-influenced plumes can result in particles with a wide range of viscosities after long-range transport in the free troposphere. We also used temperature and RH values extracted from the Global Forecast System (GFS) along the FLEXPART-simulated path to predict the phase state of the particles during transport and found that neglecting internal mixing with inorganics would lead to an overestimation of the viscosity of free tropospheric particles. Our findings warrant future investigation aiming at the quantitative assessment of the influence of internal mixing on the phase states of the individual particles. This study also provides insights into the chemical composition and phase state of free tropospheric particles, which can help models to reduce uncertainties about the effects of ambient aerosol particles on climate.
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Yu, Hua, Weijun Li, Yangmei Zhang, Peter Tunved, Manuel Dall'Osto, Xiaojing Shen, Junying Sun, Xiaoye Zhang, Jianchao Zhang e Zongbo Shi. "Organic coating on sulfate and soot particles during late summer in the Svalbard Archipelago". Atmospheric Chemistry and Physics 19, n. 15 (15 agosto 2019): 10433–46. http://dx.doi.org/10.5194/acp-19-10433-2019.
Testo completoAbstract (sommario):
Abstract. Interaction of anthropogenic particles with radiation and clouds plays an important role in Arctic climate change. The mixing state of aerosols is a key parameter to influence aerosol radiation and aerosol–cloud interactions. However, little is known of this parameter in the Arctic, preventing an accurate representation of this information in global models. Here we used transmission electron microscopy with energy-dispersive X-ray spectrometry, scanning electron microscopy, nanoscale secondary ion mass spectrometry, and atomic forces microscopy to determine the size and mixing state of individual sulfate and carbonaceous particles at 100 nm to 2 µm collected in the Svalbard Archipelago in summer. We found that 74 % by number of non-sea-salt sulfate particles were coated with organic matter (OM); 20 % of sulfate particles also had soot inclusions which only appeared in the OM coating. The OM coating is estimated to contribute 63 % of the particle volume on average. To understand how OM coating influences optical properties of sulfate particles, a Mie core–shell model was applied to calculate optical properties of individual sulfate particles. Our result shows that the absorption cross section of individual OM-coated particles significantly increased when assuming the OM coating as light-absorbing brown carbon. Microscopic observations here suggest that OM modulates the mixing structure of fine Arctic sulfate particles, which may determine their hygroscopicity and optical properties.
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Tomlin, Jay M., Kevin A. Jankowski, Daniel P. Veghte, Swarup China, Peiwen Wang, Matthew Fraund, Johannes Weis et al. "Impact of dry intrusion events on the composition and mixing state of particles during the winter Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA)". Atmospheric Chemistry and Physics 21, n. 24 (14 dicembre 2021): 18123–46. http://dx.doi.org/10.5194/acp-21-18123-2021.
Testo completoAbstract (sommario):
Abstract. Long-range transport of continental emissions has a far-reaching influence over remote regions, resulting in substantial change in the size, morphology, and composition of the local aerosol population and cloud condensation nuclei (CCN) budget. Here, we investigate the physicochemical properties of atmospheric particles collected on board a research aircraft flown over the Azores during the winter 2018 Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA) campaign. Particles were collected within the marine boundary layer (MBL) and free troposphere (FT) after long-range atmospheric transport episodes facilitated by dry intrusion (DI) events. Chemical and physical properties of individual particles were investigated using complementary capabilities of computer-controlled scanning electron microscopy and X-ray spectromicroscopy to probe particle external and internal mixing state characteristics. Furthermore, real-time measurements of aerosol size distribution, cloud condensation nuclei (CCN) concentration, and back-trajectory calculations were utilized to help bring into context the findings from offline spectromicroscopy analysis. While carbonaceous particles were found to be the dominant particle type in the region, changes in the percent contribution of organics across the particle population (i.e., external mixing) shifted from 68 % to 43 % in the MBL and from 92 % to 46 % in FT samples during DI events. This change in carbonaceous contribution is counterbalanced by the increase in inorganics from 32 % to 57 % in the MBL and 8 % to 55 % in FT. The quantification of the organic volume fraction (OVF) of individual particles derived from X-ray spectromicroscopy, which relates to the multi-component internal composition of individual particles, showed a factor of 2.06 ± 0.16 and 1.11 ± 0.04 increase in the MBL and FT, respectively, among DI samples. We show that supplying particle OVF into the κ-Köhler equation can be used as a good approximation of field-measured in situ CCN concentrations. We also report changes in the κ values in the MBL from κMBL, non-DI=0.48 to κMBL, DI=0.41, while changes in the FT result in κFT, non-DI=0.36 to κFT, DI=0.33, which is consistent with enhancements in OVF followed by the DI episodes. Our observations suggest that entrainment of particles from long-range continental sources alters the mixing state population and CCN properties of aerosol in the region. The work presented here provides field observation data that can inform atmospheric models that simulate sources and particle composition in the eastern North Atlantic.
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Murphy, D. M., P. K. Hudson, D. J. Cziczo, S. Gallavardin, K. D. Froyd, M. V. Johnston, A. M. Middlebrook et al. "Distribution of lead in single atmospheric particles". Atmospheric Chemistry and Physics Discussions 7, n. 2 (13 marzo 2007): 3763–804. http://dx.doi.org/10.5194/acpd-7-3763-2007.
Testo completoAbstract (sommario):
Abstract. Three independent single particle mass spectrometers measured Pb in individual aerosol particles. These data provide unprecedented sensitivity and statistical significance for the measurement of Pb in single particles. This paper explores the reasons for the frequency of Pb in fine particles now that most gasoline is unleaded. Trace amounts of Pb were found in 5 to 25% of 250 to 3000 nm diameter particles sampled by both aircraft and surface instruments in the eastern and western United States. Over 5% of particles at a mountain site in Switzerland contained Pb. Particles smaller than 100 nm with high Pb content were also observed by an instrument that was only operated in urban areas. Lead was found on all types of particles, including Pb present on biomass burning particles from remote fires. Less common particles with high Pb contents contributed a majority of the total amount of Pb. Single particles with high Pb content often also contained alkali metals, Zn, Cu, Sn, As, and Sb. The association of Pb with Zn and other metals is also found in IMPROVE network filter data from surface sites. Sources of airborne Pb in the United States are reviewed for consistency with these data. The frequent appearance of trace Pb is consistent with widespread emissions of fine Pb particles from combustion sources followed by coagulation with larger particles during long-range transport. Industrial sources that directly emit Pb-rich particles also contribute to the observations. Clean regions of the western United States show some transport of Pb from Asia but most Pb over the United States comes from North American sources. Resuspension of Pb from soil contaminated by the years of leaded gasoline was not directly apparent.
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Murphy, D. M., P. K. Hudson, D. J. Cziczo, S. Gallavardin, K. D. Froyd, M. V. Johnston, A. M. Middlebrook et al. "Distribution of lead in single atmospheric particles". Atmospheric Chemistry and Physics 7, n. 12 (21 giugno 2007): 3195–210. http://dx.doi.org/10.5194/acp-7-3195-2007.
Testo completoAbstract (sommario):
Abstract. Three independent single particle mass spectrometers measured Pb in individual aerosol particles. These data provide unprecedented sensitivity and statistical significance for the measurement of Pb in single particles. This paper explores the reasons for the frequency of Pb in fine particles now that most gasoline is unleaded. Trace amounts of Pb were found in 5 to 25% of 250 to 3000 nm diameter particles sampled by both aircraft and surface instruments in the eastern and western United States. Over 5% of particles at a mountain site in Switzerland contained Pb. Particles smaller than 100 nm with high Pb content were also observed by an instrument that was only operated in urban areas. Lead was found on all types of particles, including Pb present on biomass burning particles from remote fires. Less common particles with high Pb contents contributed a majority of the total amount of Pb. Single particles with high Pb content often also contained alkali metals, Zn, Cu, Sn, As, and Sb. The association of Pb with Zn and other metals is also found in IMPROVE network filter data from surface sites. Sources of airborne Pb in the United States are reviewed for consistency with these data. The frequent appearance of trace Pb is consistent with widespread emissions of fine Pb particles from combustion sources followed by coagulation with larger particles during long-range transport. Industrial sources that directly emit Pb-rich particles also contribute to the observations. Clean regions of the western United States show some transport of Pb from Asia but most Pb over the United States comes from North American sources. Resuspension of Pb from soil contaminated by the years of leaded gasoline was not directly apparent.
46
Liu, S., L. M. Russell, D. T. Sueper e T. B. Onasch. "Organic particle types by single-particle measurements using a time-of-flight aerosol mass spectrometer coupled with a light scattering module". Atmospheric Measurement Techniques 6, n. 2 (1 febbraio 2013): 187–97. http://dx.doi.org/10.5194/amt-6-187-2013.
Testo completoAbstract (sommario):
Abstract. Chemical and physical properties of individual ambient aerosol particles can vary greatly, so measuring the chemical composition at the single-particle level is essential for understanding atmospheric sources and transformations. Here we describe 46 days of single-particle measurements of atmospheric particles using a time-of-flight aerosol mass spectrometer coupled with a light scattering module (LS-ToF-AMS). The light scattering module optically detects particles larger than 180 nm vacuum aerodynamic diameter (130 nm geometric diameter) before they arrive at the chemical mass spectrometer and then triggers the saving of single-particle mass spectra. 271 641 particles were detected and sampled during 237 h of sampling in single-particle mode. By comparing timing of the predicted chemical ion signals from the light scattering measurement with the measured chemical ion signals by the mass spectrometer for each particle, particle types were classified and their number fractions determined as follows: prompt vaporization (46%), delayed vaporization (6%), and null (48%), where null was operationally defined as less than 6 ions per particle. Prompt and delayed vaporization particles with sufficient chemical information (i.e., more than 40 ions per particle) were clustered based on similarity of organic mass spectra (using k-means algorithm) to result in three major clusters: highly oxidized particles (dominated by m/z 44), relatively less oxidized particles (dominated by m/z 43), and particles associated with fresh urban emissions. Each of the three organic clusters had limited chemical properties of other clusters, suggesting that all of the sampled organic particle types were internally mixed to some degree; however, the internal mixing was never uniform and distinct particle types existed throughout the study. Furthermore, the single-particle mass spectra and time series of these clusters agreed well with mass-based components identified (using factor analysis) from simultaneous ensemble-averaged measurements, supporting the connection between ensemble-based factors and atmospheric particle sources and processes. Measurements in this study illustrate that LS-ToF-AMS provides unique information about organic particle types by number as well as mass.
47
Berghof, M. I. A., G. P. Frank, S. Sjogren e B. G. Martinsson. "Inversion of droplet aerosol analyzer data for long-term aerosol-cloud interaction measurements". Atmospheric Measurement Techniques Discussions 6, n. 6 (29 novembre 2013): 10269–95. http://dx.doi.org/10.5194/amtd-6-10269-2013.
Testo completoAbstract (sommario):
Abstract. The droplet aerosol analyzer (DAA) was developed to study the influence of aerosol properties on clouds. It measures the ambient particle size of individual droplets and interstitial particles, the size of the dry (residual) particles after the evaporation of water, and the number concentration of the dry (residual) particles. A method was developed for the evaluation of DAA data to obtain the three-parameter dataset: ambient particle diameter, dry (residual) particle diameter and number concentration. First results from in-cloud measurements performed on the summit of Mt. Brocken in Germany are presented. Various aspects of the cloud aerosol dataset are presented, such as the number concentration of interstitial particles and cloud droplets, the dry residue particle size distribution, droplet size distributions, scavenging ratios due to cloud droplet formation and size-dependent solute concentrations. This dataset makes it possible to study clouds and the influence of the aerosol population on clouds.
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Li, Chenxi, e Peter H. McMurry. "Errors in nanoparticle growth rates inferred from measurements in chemically reacting aerosol systems". Atmospheric Chemistry and Physics 18, n. 12 (28 giugno 2018): 8979–93. http://dx.doi.org/10.5194/acp-18-8979-2018.
Testo completoAbstract (sommario):
Abstract. In systems in which aerosols are being formed by chemical transformations, individual particles grow due to the addition of molecular species. Efforts to improve our understanding of particle growth often focus on attempts to reconcile observed growth rates with values calculated from models. However, because it is typically not possible to measure the growth rates of individual particles in chemically reacting systems, they must be inferred from measurements of aerosol properties such as size distributions, particle number concentrations, etc. This work discusses errors in growth rates obtained using methods that are commonly employed for analyzing atmospheric data. We analyze “data” obtained by simulating the formation of aerosols in a system in which a single chemical species is formed at a constant rate, R. We show that the maximum overestimation error in measured growth rates occurs for collision-controlled nucleation in a single-component system in the absence of a preexisting aerosol, wall losses, evaporation or dilution, as this leads to the highest concentrations of nucleated particles. Those high concentrations lead to high coagulation rates that cause the nucleation mode to grow faster than would be caused by vapor condensation alone. We also show that preexisting particles, when coupled with evaporation, can significantly decrease the concentration of nucleated particles. This can lead to decreased discrepancies between measured growth rate and true growth rate by reducing coagulation among nucleated particles. However, as particle sink processes become stronger, measured growth rates can potentially be lower than true particle growth rates. We briefly discuss nucleation scenarios in which the observed growth rate approaches zero while the true growth rate does not.
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Wang, Bingbing, Daniel A. Knopf, Swarup China, Bruce W. Arey, Tristan H. Harder, Mary K. Gilles e Alexander Laskin. "Direct observation of ice nucleation events on individual atmospheric particles". Physical Chemistry Chemical Physics 18, n. 43 (2016): 29721–31. http://dx.doi.org/10.1039/c6cp05253c.
Testo completo
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Liu, S., L. M. Russell, D. T. Sueper e T. B. Onasch. "Organic particle types by single-particle measurements using a time-of-flight aerosol mass spectrometer coupled with a light scattering module". Atmospheric Measurement Techniques Discussions 5, n. 2 (25 aprile 2012): 3047–77. http://dx.doi.org/10.5194/amtd-5-3047-2012.
Testo completoAbstract (sommario):
Abstract. Chemical and physical properties of individual ambient aerosol particles can vary greatly, so measuring the chemical composition at the single-particle level is essential for understanding atmospheric sources and transformations. Here we describe 46 days of single-particle measurements of atmospheric particles using a time-of-flight aerosol mass spectrometer coupled with a light scattering module (LS-ToF-AMS). The light scattering module optically detects particles larger than 180 nm vacuum aerodynamic diameter (130 nm geometric diameter) (with size resolution of 5–10 defined as dΔd at full width at half maximum) before they arrive at the chemical mass detector and then triggers the saving of single-particle mass spectra. 271 641 particles were detected and sampled during 237 h of sampling in single particle mode. By comparing the timing of light scattering and chemical ion signals for each particle, particle types were classified and their number fractions determined as follows: prompt vaporization (49%), delayed vaporization (7%), and null (44%). LS-ToF-AMS provided the first direct measurement of the size-resolved collection efficiency (CE) of ambient particles, with an approximate 50% number-based CE for particles above detection limit. Prompt and delayed vaporization particles (147 357 particles) were clustered based on similar organic mass spectra (using K-means algorithm) to result in three major clusters: highly oxidized particles (dominated by m/z 44), relatively less oxidized particles (dominated by m/z 43), and particles associated with fresh urban emissions. Each of the three organic clusters had limited chemical properties of other clusters, suggesting that all of the sampled organic particle types were internally mixed to some degree; however, the internal mixing was never uniform and distinct particle types existed throughout the study. Furthermore, the single particle mass spectra and diurnal variations of these clusters agreed well with mass-based components identified (using factor analysis) from simultaneous ensemble-averaged measurements, supporting the connection between ensemble-based factors and atmospheric particle sources and processes. Measurements in this study illustrate that LS-ToF-AMS provides unique information about organic particle types by number as well as mass.