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1

Nucleation of atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

A significant fraction of the total number of particles present in the atmosphere is formed originally by nucleation from the gas phase. Binary nucleation of sulphuric acid and water, ternary nucleation of sulphuric acid, water and ammonia and ion-induced nucleation are thought to be the most important aerosol nucleation processes in the atmosphere. Within the last two decades, instrumentation to observe and characterize nucleation has improved greatly and numerous observations of nucleation have been made including quantification of the nucleation rate, characterization of the growth process and first chemical characterizations of the freshly formed particles. Nucleation has been observed at many different places in the atmosphere: in the boundary layer, in the free troposphere, in remote locations, in coastal areas, in boreal forests as well as urban areas and pollution plumes. In most cases gaseous sulphuric acid is assumed to be the key precursor gas. After nucleation, other supersaturated substances, especially low vapour pressure organics often take part in the subsequent aerosol growth. Iodine oxides seem to be responsible for nucleation observed in some coastal areas. Recent advances in modelling allow for a kinetic treatment of the nucleation process based on measured thermochemical data for the cluster formation. Considerable improvement over the classical nucleation treatment is expected from this approach. A detailed understanding of atmospheric aerosol nucleation processes is needed as the freshly formed particles directly influence the number concentration and size distribution of the atmospheric aerosol. The formation of clouds and precipitation is affected and influences on climate are anticipated. Anthropogenic emissions influence atmospheric aerosol nucleation processes considerably. Despite the comprehensive research efforts, substantial inconsistencies remain and conflicting results of laboratory studies, model studies as well as atmospheric observations persist. Several key questions about the predictability of atmospheric nucleation in general, about the substances, that take part in nucleation and subsequent growth and about the size and composition of the critical cluster, have not been resolved so far. To cite this article: J. Curtius, C. R. Physique 7 (2006).

Curtius, Joachim

2006-11-01

2

Images reveal that atmospheric particles can undergo liquidliquid phase separations  

E-print Network

, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particlesImages reveal that atmospheric particles can undergo liquidĀ­liquid phase separations Yuan Youa aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles

3

PARTICLE ROTATIONS IN GRANULAR MATERIALS  

Microsoft Academic Search

Particle rotations can have a dominant influence on the behavior of granular materials, particularly in materials with circular or spherical particles. The paper briefly reviews experimental evidence of the magnitude and variability of particle rotations and their effect on a granular material's stiffness and strength. Evidence of rotational patterning is reported from DEM simulations of a large square assembly of

Matthew R. Kuhn; Katalin Bagi

4

Educational Materials in Atmospheric Chemistry  

NSDL National Science Digital Library

Professor Daniel J. Jacob of Harvard University has compiled this very fine set of educational materials that deal with various aspects of atmospheric chemistry. He draws these resources from his own teaching experience, along with offering slides, presentations, and information from his own introductory textbook on the subject. Visitors can click through sections that contain resources such as Power Point presentations on halogen chemistry, aerosols, and global biogeochemical cycles. Professor Jacob has also been kind enough to include several versions of his 1999 textbook titled "Introduction to Atmosphere Chemistry" for general consideration and use. Finally, the site also contains resources on chemical transport models intended for graduate students.

Jacob, Daniel J., 1958-

2008-04-16

5

Educational Materials in Atmospheric Chemistry  

NSDL National Science Digital Library

Professor Daniel J. Jacob of Harvard University has compiled this very fine set of educational materials that deal with various aspects of atmospheric chemistry. He draws these resources from his own teaching experience, along with offering slides, presentations, and information from his own introductory textbook on the subject. Visitors can click through sections that contain resources such as Power Point presentations on halogen chemistry, aerosols, and global biogeochemical cycles. Professor Jacob has also been kind enough to include several versions of his 1999 textbook titled "Introduction to Atmosphere Chemistry" for general consideration and use. Finally, the site also contains resources on chemical transport models intended for graduate students.

Jacob, Daniel J., 1958-

6

The Effects of Atmospheric Particles on Climate  

NSDL National Science Digital Library

This video illustrates how atmospheric particles, or aerosols (such as black carbon, sulfates, dust, fog), can affect the energy balance of Earth regionally, and the implications for surface temperature warming and cooling.

Thinktv; Domain, Teachers'

7

Vapor scavenging by atmospheric aerosol particles  

SciTech Connect

Particle growth due to vapor scavenging was studied using both experimental and computational techniques. Vapor scavenging by particles is an important physical process in the atmosphere because it can result in changes to particle properties (e.g., size, shape, composition, and activity) and, thus, influence atmospheric phenomena in which particles play a role, such as cloud formation and long range transport. The influence of organic vapor on the evolution of a particle mass size distribution was investigated using a modified version of MAEROS (a multicomponent aerosol dynamics code). The modeling study attempted to identify the sources of organic aerosol observed by Novakov and Penner (1993) in a field study in Puerto Rico. Experimentally, vapor scavenging and particle growth were investigated using two techniques. The influence of the presence of organic vapor on the particle`s hydroscopicity was investigated using an electrodynamic balance. The charge on a particle was investigated theoretically and experimentally. A prototype apparatus--the refractive index thermal diffusion chamber (RITDC)--was developed to study multiple particles in the same environment at the same time.

Andrews, E.

1996-05-01

8

Sources and transformations of atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Aerosol particles are an important component of the Earth-Atmosphere system because of their influence on the radiation budget both directly (through absorption and scattering) and indirectly (through cloud condensation nuclei (CCN) activity). The magnitude of the raditaive forcing attributed to the direct and indirect aerosol effects is highly uncertain, leading to large uncertainties in projections of global climate change. Real-time measurements of aerosol properties are a critical step toward constraining the uncertainties in current global climate modeling and understanding the influence that anthropogenic activities have on the climate. The objective of the work presented in this thesis is to gain a more complete understanding of the atmospheric transformations of aerosol particles and how such transformations influence the direct and indirect radiative effects of the particles. The work focuses on real-time measurements of aerosol particles made with the Aerodyne Aerosol Mass Spectrometer (AMS) developed in collaboration with the Boston College research group. A key feature of the work described is the development of a light scattering module for the AMS. Here we present the first results obtained with the integrated light scattering - AMS system. The unique and powerful capabilities of this new instrument combination are demonstrated through laboratory experiments and field deployments. Results from two field studies are presented: (1) The Northeast Air Quality Study (NEAQS), in the summer of 2004, conducted at Chebogue Point, Nova Scotia and (2) The Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign conducted in and around Mexico City, Mexico in March of 2006. Both field studies were designed to study the transformations that occur within pollution plumes as they are transported throughout the atmosphere. During the NEAQS campaign, the pollution plume from the Northeastern United States was intercepted as it was transported towards Europe. In this study, particles were highly processed prior to sampling, with residence times of a few days in the atmosphere. The MILAGRO campaign focused on the evolution of the Mexico City plume as it was transported north. During this study, regional and locally emitted particles were measured with residence times varying from minutes to days in the atmosphere. In both studies, the light scattering - AMS system provided detailed information about the density and composition of single particles, leading to important insights into how atmospheric processing transforms the particle properties. In Mexico City, the light scattering-AMS system was used for the first time as a true single particle mass spectrometer and revealed specific details about the atmospheric processing of primary particles from combustion sources. To quantify the radiative effects of the particles on climate, the processing and ultimate fate of primary emissions (often containing black carbon or soot) must be understood. To provide a solid basis for the interpretation of the data obtained during the field studies, experiments were conducted with a well characterized soot generation-sampling system developed by the Boston College research group. The laboratory soot source was combined with the light scattering - AMS system and a Cloud Condensation Nuclei Counter (CCNC) to measure the change in cloud-forming activity of soot particles as they are processed in the atmosphere. Because of the importance of black carbon in the atmosphere, several instruments have been developed to measure black carbon. In July of 2008, an intercomparison study of 18 instruments was conducted in the Boston College laboratory, with soot particles produced and processed to mimic a wide range of atmospherically-relevant conditions. Transformations in the physical, chemical, and optical properties of soot particles were monitored with the combined suite of aerosol instrumentation. Results from the intercomparison study not only calibrated the different instruments used in the study, but also provided criti

Cross, Eben Spencer

9

Particle heated atmospheres of magnetic white dwarfs  

NASA Astrophysics Data System (ADS)

We discuss the particle heating of magnetic atmospheres in AM Her stars. For small accretion rates cyclotron losses can balance the energy input due to Coulomb encounters within one mean free path of the infalling protons and no shock forms. We solve the radiative transfer in the target atmosphere and present for the first time temperature structure and cyclotron spectra of a particle heated atmosphere as solution of an LTE stellar atmosphere code. We find temperature inversions between the heated outer layers and the photosphere up to three orders of magnitude depending on the accretion rate, the white dwarf mass and the magnetic field strength. The spectra show strong cyclotron line emission in the optical/IR, an optically thick continuum in the UV/XUV regime and a weak, optically thin bremsstrahlung component at X-ray energies. Passing through the colder outer parts of the atmosphere, the cyclotron lines develop strong self absorption in the first two or three harmonics generating strongly deformed line profiles, clearly different from those in previous isothermal models.

Woelk, U.; Beuermann, K.

1992-03-01

10

Review: Model particles in atmospheric optics  

NASA Astrophysics Data System (ADS)

This review paper provides an overview over model geometries for computing light scattering by small particles. The emphasis is on atmospheric optics, although much of this review will also be relevant to neighbouring fields, in particular to astronomy. Various morphological particle properties are discussed, such as overall nonsphericity, pristine shapes, aggregation, and different forms of inhomogeneity, e.g. porous and compact inhomogeneous morphologies, as well as encapsulated aggregates. Models employed to reproduce the optical properties of complex particles range from strongly simplified to highly realistic and morphologically sophisticated model geometries. Besides reviewing the most recent literature, we discuss the idea behind models of varying degree of complexity with regard to the intended use of the models. Applications range from fundamental studies of light scattering processes to routine applications of particle optics look-up tables in operational modelling systems.

Kahnert, Michael; Nousiainen, Timo; Lindqvist, Hannakaisa

2014-10-01

11

Particle Suspension Mechanisms - Supplemental Material  

SciTech Connect

This supplemental material provides a brief introduction to particle suspension mechanisms that cause exfoliated skin cells to become and remain airborne. The material presented here provides additional context to the primary manuscript and serves as background for designing possible future studies to assess the impact of skin cells as a source of infectious aerosols. This introduction is not intended to be comprehensive and interested readers are encouraged to consult the references cited.

Dillon, M B

2011-03-03

12

Genotoxicity of organic extracts from atmospheric particles  

SciTech Connect

Experiments to evaluate the genotoxic potentialities of urban air particles sampled in Paris (France) after organic solvent extraction have been carried out using four in vitro genotoxicity tests. The two bacterial tests (the Ames test and the SOS Chromotest) demonstrate the genotoxicity of the organic extracts of atmospheric particles; two additional tests (induction of 6-thioguanine mutants and sister chromatid exchanges), carried out on V79 Chinese hamster cells, also confirm these potentialities. These results show clearly that particulate organic extracts induce point mutations in both bacteria and mammalian cells, or the cellular response (SOS repair) to these mutations in bacteria; likewise, they are responsible for clastogenic effects in mammalian cells. Genotoxicity is due either to direct genotoxic chemicals or to active metabolic products of the action of microsomal enzymes. The optimalization of testing procedures is discussed in order to appreciate the contribution of genotoxicity tests to the study of atmospheric pollution.

Courtois, Y.A.; Min, S.; Lachenal, C.; Jacquot-Deschamps, J.M.; Callais, F.; Festy, B.

1988-01-01

13

Phase of atmospheric secondary organic material affects its reactivity  

PubMed Central

The interconversion of atmospheric organic particles among solid, semisolid, and liquid phases is of keen current scientific interest, especially for particles of secondary organic material (SOM). Herein, the influence of phase on ammonia uptake and subsequent particle-phase reactions was investigated for aerosol particles of adipic acid and ?-pinene ozonolysis SOM. The nitrogen content of the particles was monitored by online mass spectrometry for increasing ammonia exposure. Solid and semisolid adipic acid particles were inert to the ammonia uptake for low RH (< 5%). For the solid particles, ammonia exposure at high relative humidity (RH; > 94%) induced a first-order deliquescence phase transition into aqueous particles. Solid particles exposed to supersaturated (RH > 100%) conditions and cycled back to high RH (> 94%), thereby becoming acidic metastable particles, underwent a gradual second-order transition upon ammonia exposure to form aqueous, partially neutralized particles. For ?-pinene SOM, ammonia exposure at low RH increased the particle-phase ammonium content by a small amount. Mass spectrometric observations suggest a mechanism of neutralization and co-condensation of acidic gas-phase species, consistent with a highly viscous semisolid upon which adsorption occurs. At high RH the ammonium content increased greatly, indicative of rapid diffusion and absorption in a liquid environment. The mass spectra indicated the production of organonitrogen compounds, possibly by particle-phase reactive chemistry. The present results demonstrate that phase can be a key regulator of the reactivity of atmospheric SOM particles. PMID:23045632

Kuwata, Mikinori; Martin, Scot T.

2012-01-01

14

Nucleation and Growth of Atmospheric Particles  

SciTech Connect

New particle formation (NPF) in the atmospheric is a two-step process: Nucleation leads to the birth of stable nuclei that subsequently grow to sizes that can be detected and affect the atmosphere’s radiative properties. Our group is studying both of these processes. Our nucleation research is largely supported by NSF and involves measurements of neutral molecular clusters formed by nucleation with a new custom-designed mass spectrometer (the Cluster-CIMS) and measurements of nanoparticle size distributions as small as 1 nm with a new aerosol spectrometer (the DEG SMPS). These measurements are providing new insights into aspects of cluster behavior that affect nucleation rates. The U.S. DOE supports our research on nanoparticle growth rates. This research couples physical and chemical measurements of aerosol properties and behavior. The TDCIMS, which enables real-time measurements of composition for freshly nucleated particles as small as 8 nm and was developed with support from DOE, is the most important tool in this work. Our most important discoveries about processes that affect growth rates are summarized in a recent PNAS article (doi:10.1073/pnas.0912127107). In short, this work has shown that alkylammonium-carboxylate salts, formed, for example, by reactions between amines and carboxylic acids, account for 20–50% of the mass of freshly nucleated particles in locations that include Atlanta, Mexico City, Boulder, and Hyytiälä, while sulfates account for only about 10%. These newly discovered compounds help to explain the high growth rates of freshly nucleated particles that have been observed around the globe and help to explain why nucleation is an important atmospheric process, not just a scientific curiosity. Our poster will provide an overview of this work.

McMurry, P.; Kuang, C.; Barsanti, K.; Eisele, F.; Friedli, H.; Scheckman, J.; Titcombe, M.; Williams, B.; Zhao, J.; Smith, J.

2010-03-15

15

Images reveal that atmospheric particles can undergo liquid-liquid phase separations  

NASA Astrophysics Data System (ADS)

A large fraction of submicron atmospheric particles contain both organic material and inorganic salts. As the relative humidity cycles in the atmosphere, these mixed particles can undergo a range of phase transitions, possibly including liquid-liquid phase separation. If liquid-liquid phase separation occurs, the gas-particle partitioning of atmospheric semi-volatile organic compounds, the scattering and absorption of solar radiation, and the uptake of reactive gas species on atmospheric particles may be affected. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two non-crystalline phases in particles generated from samples collected on multiple days in Atlanta, Georgia, and in particles generated in the laboratory using simulated atmospheric conditions. These results show that atmospheric particles can undergo liquid-liquid phase separations.

Bertram, A. K.; You, Y.; Renbaum-Wolff, L.; Carreras-Sospedra, M.; Hiranuma, N.; Smith, M.; Zhang, X.; Weber, R.; Shilling, J. E.; Dabdub, D.; Martin, S. T.

2012-12-01

16

Atmospheric Tar Balls: Particles from Biomass and Biofuel Burning  

NASA Technical Reports Server (NTRS)

Tar balls are amorphous, carbonaceous spherules that occur in the tropospheric aerosol as a result of biomass and biofuel burning. They form a distinct group of particles with diameters typically between 30 and 500 nm and readily identifiable with electron microscopy. Their lack of a turbostratic microstructure distinguishes them from soot, and their morphology and composition (approximately 90 mol% carbon) renders them distinct from other carbonaceous particles. Tar balls are particularly abundant in slightly aged (minutes to hours old) biomass smoke, indicating that they likely form by gas-to-particle conversion within smoke plumes. The material of tar balls is initially hygroscopic; however, the particles become largely insoluble as a result of free radical polymerization of their organic molecules. Consequently, tar balls are primarily externally mixed with other particle types, and they do not appreciably increase in size during aging. When tar balls coagulate with water-bearing particles, their material may partly dissolve and no longer be recognizable as distinct particles. Tar balls may contain organic compounds that absorb sunlight. They are an important, previously unrecognized type of carbonaceous (organic) atmospheric particle.

Posfai, Mihaly; Gelencser, Andras; Simonics, Renata; Arato, Krisztina; Li, Jia; Hobbs, Peter V.; Buseck, Peter R.

2004-01-01

17

Characterization of individual complex particles in urban atmospheric environment  

NASA Astrophysics Data System (ADS)

The origins of carrier particles of complex particles (iron-rich particles) collected from the urban atmospheric environment near to road traffic and a railroad were investigated from the detailed surface information using FE-SEM/EDS and TOF-SIMS analyses. From the FE-SEM/EDS analyses, the iron-rich particles were classified into two typical types (spherical type and non-spherical type). From the TOF-SIMS measurements, the characteristic secondary ions of spherical type of iron-rich particles were 23Na + and 39K +. The minor components of non-spherical type were Al, Ca and Ba. On the other hand, we carried out TOF-SIMS measurement to materials of rail origin and brake origin. From the comparison of these spectra pattern, it seemed that the spherical type of iron-rich particles was emitted from the rail origin. We concluded that the origin of non-spherical type of iron-rich particles were brake pad of vehicles.

Suzuki, K.; Takii, T.; Tomiyasu, B.; Nihei, Y.

2006-07-01

18

ATMOSPHERIC PROCESSES AND EFFECTS ON MATERIALS  

EPA Science Inventory

These two chapters summarize the effects expected from the depletion of stratospheric ozone by the presence of CFCs. he two areas considered by these two reports are materials damage and atmospheric processes. ncreased UV can affect materials in the following ways: (1) corrosion ...

19

Images reveal that atmospheric particles can undergo liquid-liquid phase separations  

SciTech Connect

A large fraction of submicron atmospheric particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere, these mixed particles can undergo a range of phase transitions, possibly including liquid-liquid phase separation. If liquid-liquid phase separation occurs, the gas-particle partitioning of atmospheric semi-volatile organic compounds, the scattering and absorption of solar radiation, and the uptake of reactive gas species on atmospheric particles will be affected, with important implications for climate predictions. The actual occurrence of these types of phase transitions within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we observe the coexistence of two non-crystalline phases in particles generated from real-world samples collected on multiple days in Atlanta, Georgia, and in particles generated in the laboratory using atmospheric conditions. These results reveal that atmospheric particles can undergo liquid-liquid phase separations. Using a box model, we show that liquid-liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 in the Atlanta region, due to decreased particle uptake of N2O5.

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L.; Zhang, Xiaolu; Weber, Rodney; Shilling, John E.; Dabdub, Donald; Martin, Scot T.; Bertram, Allan K.

2012-07-30

20

Catching Comet's Particles in the Earth's Atmosphere by Using Balloons  

NASA Astrophysics Data System (ADS)

The project is intended to catch cometary particles in the atmosphere by using balloons. The investigation is based upon knowledge that the Earth crosses the comet’s tails during the year. One can catch these particles at different altitudes in the atmosphere. So, we will be able to gradually advance in the ability to launch balloons from low to high altitudes and try to catch particles from different comet tails. The maximum altitude that we have to reach is 40 km. Both methods - distance observation and cometary samples from mission Stardust testify to the presence of organic components in comet’s particles. It would be useful to know more details about this organic matter for astrobiology; besides, the factor poses danger to the Earth. Moreover, it is important to prove that it is possible to get fundamental scientific results at low cost. In the last 5 years launching balloons has become popular and this movement looks like hackers’ one - as most of them occur without launch permission to airspace. The popularity of ballooning is connected with low cost of balloon, GPS unit, video recording unit. If you use iPhone, you have a light solution with GPS, video, picture and control function in one unit. The price of balloon itself begins from $50; it depends on maximum altitude, payload weight and material. Many university teams realized balloon launching and reached even stratosphere at an altitude of 33 km. But most of them take only video and picture. Meanwhile, it is possible to carry out scientific experiments by ballooning, for example to collect comet particles. There is rich experience at the moment of the use of mineral, chemical and isotopic analysis techniques and data of the comet’s dust after successful landing of StarDust capsule with samples in 2006. Besides, we may use absolutely perfect material to catch particles in the atmosphere, which was used by cosmic missions such as Stardust and Japanese Hayabusa. As to balloon launches, we could use Indian Space Research Organization experience that launched a balloon to stratosphere in 2009 and successfully caught particles with organics at an altitude of 42 km. The main aim of the project is to catch cometary particles by using balloons and to make this method steady and reliable. Why are the comet particles interesting? The nature of a comet is full of puzzles; many researchers think that comets may give keys to the origin of the Solar System and origin of life on the Earth. 2014 and 2015 are special years for comet science: mission Rozetta will reach the vicinity of the comet 67P/Churyumov-Gerasimenko - 10 years after leaving the Earth. Using astronomic data, one may choose date for ballooning, specify the altitude of comet particles by photometry and laser measurement of particle outburst. After height measurement one may launch a balloon. For example, for Draconids particles (Parent comet: 21PGiacobini-Zinner) the expected time of outburst maximum - hence that for catching is 22:42 UT, October 6, 2014. The best conditions for catching will be in Greenland and extreme north-eastern part of North America. Draconids are very convenient for the initial stage of the project - the altitude of observed Draconids outburst is 10 km. One may catch them above 10 km, e.g. 10500 m. We consider ballooning is quite a good method to get experimental data as an additional technique in comparison with big space missions. Moreover, it might be a part of cosmic mission to other planets such as Mars and Venus. The approach of the project is to make targeting catch of comet particles. The method consists of choosing the right place and time for ballooning.

Potashko, Oleksandr; Viso, Michel

21

Images reveal that atmospheric particles can undergo liquid-liquid phase separations  

PubMed Central

A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid–liquid phase separation. If liquid–liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid–liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid–liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid–liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 due to decreased particle uptake of N2O5. PMID:22847443

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah J.; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L.; Zhang, Xiaolu; Weber, Rodney J.; Shilling, John E.; Dabdub, Donald; Martin, Scot T.; Bertram, Allan K.

2012-01-01

22

Wear of hard materials by hard particles  

SciTech Connect

Hard materials, such as WC-Co, boron carbide, titanium diboride and composite carbide made up of Mo2C and WC, have been tested in abrasion and erosion conditions. These hard materials showed negligible wear in abrasion against SiC particles and erosion using Al2O3 particles. The WC-Co materials have the highest wear rate of these hard materials and a very different material removal mechanism. Wear mechanisms for these materials were different for each material with the overall wear rate controlled by binder composition and content and material grain size.

Hawk, Jeffrey A.

2003-10-01

23

Dielectric particle injector for material processing  

NASA Technical Reports Server (NTRS)

A device for use as an electrostatic particle or droplet injector is disclosed which is capable of injecting dielectric particles or droplets. The device operates by first charging the dielectric particles or droplets using ultraviolet light induced photoelectrons from a low work function material plate supporting the dielectric particles or droplets, and then ejecting the charged particles or droplets from the plate by utilizing an electrostatic force. The ejected particles or droplets are mostly negatively charged in the preferred embodiment; however, in an alternate embodiment, an ion source is used instead of ultraviolet light to eject positively charged dielectric particles or droplets.

Leung, Philip L. (Inventor)

1992-01-01

24

Capture of Meteoric Material by Mesospheric Ice Particles  

NASA Astrophysics Data System (ADS)

In the Earth's polar summer mesosphere, the co-existence of ice and meteoric material gives rise to complex particle processes. A charge-dependent coagulation model has been developed to describe the interaction between these mesospheric players. Substantial capture rates are found for both metal atoms and smoke particles of meteoric origin. This results in a local atmospheric depletion of meteoric material and a typical mass mixing ratios of 0.1% to 1% meteoric material in the ice. This affects both charging properties and optical properties of noctilucent clouds and related particle phenomena. Open questions concern the "processing" of the meteoric material in the ice and the fate of accumulated metal species and charges upon ice sublimation at the end of the life cycle of mesospheric clouds.

Gumbel, J.; Megner, L. S.; Hedin, J.

2013-12-01

25

Material flammability in space exploration atmospheres  

NASA Astrophysics Data System (ADS)

In order to reduce the risk of decompression sickness associated with extravehicular activity, NASA is designing the next generation of exploration vehicles with a different cabin pressure and oxygen concentration than used previously. This work explores how the flammability of solid materials changes in this new environment. One method to evaluate material flammability is by its ease of ignition. To this end, piloted ignition delay tests were conducted in a small-scale wind tunnel subject to this new space exploration atmosphere (SEA -- 58.6 kPa and 32% oxygen) and compared to similar tests in standard atmospheric conditions. In these tests, polymethylmethacylate (PMMA) was exposed to a range of oxidizer flow velocities and externally applied heat fluxes. It was found that the ignition time was reduced by 27% in the intended space exploration atmosphere. It was also noted that the critical heat flux for ignition decreases in exploration atmospheres. These results show that materials are more susceptible to ignition than in current spacecraft atmospheres. To further explore the effect of pressure and oxygen concentration, tests were performed for a wide range of pressures and oxygen concentrations. In all oxygen concentrations tested, the ignition delay time was seen to decrease with pressure, reach a minimum, and then increase with further reduction in pressure creating a classic u-shaped curve. No ignition was seen at sufficiently low pressures. The no ignition pressure depended on the oxygen concentration. Increasing the oxygen concentration uniformly decreases the ignition time; however, no significant differences were seen in oxygen concentrations above 24%. These results indicate there are several competing mechanisms controlling the ignition time. By reducing the pressure, the heat transfer coefficient and the mass flow rate of fuel to reach the lean flammability limit are reduced. Conversely, a reduction in pressure increases the gas-phase chemical induction time. The competition between these three mechanisms is responsible for the u-shaped dependence of ignition time on total pressure. In addition to gaining insight into the effect of pressure on piloted ignition, these results have practical applications including high altitude structures and airplane cabins.

McAllister, Sara Suzanne

26

Charged and Neutral Particle Interactions on Aerospace Materials  

SciTech Connect

Various candidate aircraft and spacecraft materials were analyzed and compared in a neutron environment using the Monte Carlo N-Particle (MCNP) transport code and in Galactic Cosmic Ray (GCR) and Trapped environments using the HZETRN code. These candidate materials are being used in aerospace vehicles, have been tested in particle beams, or seemed reasonable to analyze in this manner before deciding to manufacture and test them. This analysis shows that hydrogen bearing materials are better than the metal alloys for reducing the number of reflected and transmitted particles. It also shows that neutrons above 1 MeV are reflected out of the face of the slab better when larger quantities of carbon are present in the material. If a neutron absorber is added to the material, fewer neutrons are transmitted through and reflected from the material. This analysis focused on combinations of scatterers and absorbers to optimize these reaction channels on the higher energy neutron component. The absorber addition did not substantially change the charged particle transmission from the value obtained for polyethylene. The ultimate goal of this type of analysis is the selection of a layered material or material type that will optimize dose, dose equivalent, and electronic error rates inside the vehicle (and outside the vehicle if necessary for the mission). This analysis focuses on how the different material types and additives behave in the atmospheric and space related particle fields. As a secondary issue, as the amount of hydrogen bearing materials increase, larger fluxes of thermal neutrons are expected. It has been observed experimentally that large thicknesses of hydrogen bearing materials increase the error rates per neutron that occurs in SRAM memory chips. This effect is still being investigated, but it has been narrowed down to the larger mean neutron energy produced by the hydrogen bearing material. (authors)

Singleterry, R.C. Jr.; Thibeault, Sheila A. [NASA Langley Research Center, Hampton, VA 23681 (United States); Wilkins, Richard; Huff, Harold [Center for Applied Radiation Research, Prairie View A and M University, Prairie View, TX 77446 (United States)

2002-07-01

27

The radiation in the atmosphere during major solar particle events  

NASA Astrophysics Data System (ADS)

Major solar particle events can give rise to greatly enhanced radiation throughout the entire atmosphere including at aircraft altitudes. These particle events are very hard to predict and their effect on aircraft is difficult to calculate. A comprehensive model of the energetic radiation in the atmosphere has been developed based on a response matrix of the atmosphere to energetic particle incidence. This model has previously been used to determine the spectral form of several ground level neutron events including February 56 and September/October 1989. Significant validation of the model has been possible using CREAM data flying onboard Concorde during the September/October 1989 events. Further work has been carried out for this solar maximum, including estimates of the solar particle spectra during the July 2000, April 2001, and October 2003 events and comparisons of predicated atmospheric measurements with limited flight data. Further CREAM data has being obtained onboard commercial airlines and high altitude business jets during quiet time periods. In addition, the atmospheric radiation model, along with solar particle spectra, have been used to calculate the neutron flux and dose rates along several commercial aircraft flight paths including London - LA. The influence of suppression on cut-off rigidity by geomagnetic storms is examined and shows that the received flight dose during disturbed periods can be significantly enhanced compared with quiet periods.

Clucas, S.; Dyer, C.; Lei, F.

28

The radiation in the atmosphere during major solar particle events  

NASA Astrophysics Data System (ADS)

Major solar particle events can give rise to greatly enhanced radiation throughout the entire atmosphere including at aircraft altitudes. These particle events are very hard to predict and their effect on aircraft is difficult to calculate. A comprehensive model of the energetic radiation in the atmosphere has been developed based on a response matrix of the atmosphere to energetic particle incidence. This model has previously been used to determine the spectral form of several ground level neutron events including February 1956 and September/October 1989. Significant validation of the model has been possible using CREAM data flying onboard Concorde during the September/October 1989 events. Further work has been carried out for the current solar maximum, including estimates of the solar particle spectra during the July 2000, April 2001, and October 2003 events and comparisons of predicted atmospheric measurements with limited flight data. Further CREAM data have been obtained onboard commercial airlines and high altitude business jets during quiet time periods. In addition, the atmospheric radiation model, along with solar particle spectra, have been used to calculate the neutron flux and dose rates along several commercial aircraft flight paths including London to Los Angeles. The influence of rigidity cut-off suppression by geomagnetic storms is examined and shows that the received flight dose during disturbed periods can be significantly enhanced compared with quiet periods.

Clucas, Simon N.; Dyer, Clive S.; Lei, Fan

29

Viscosity of -pinene secondary organic material and implications for particle growth and reactivity  

E-print Network

of the atmosphere (1). These particles can influence climate by scat- tering and absorbing solar radiation (directViscosity of -pinene secondary organic material and implications for particle growth and reactivity, CA, and approved March 22, 2013 (received for review November 9, 2012) Particles composed

30

Ionization of the atmosphere caused by energetic particles  

NASA Astrophysics Data System (ADS)

Energetic particles from different sources are precipitating into the atmosphere, causing ionization and different chemical follow-ups. Focussing on low and mid-energies, this presentation will concentrate on the solar and magnetospheric particle spectrum, representing the particle forcing from the thermosphere down to the tropopause. While the precipitation of solar particles can be described in simple patterns, the magnetospheric precipitation is intensively modulated by the geomagnetic field, varying with latitude, longitude, geomagnetic disturbance, and MLT, ending up in a fluctuating auroral oval. Modeling the resulting ionization consequently is confronted with numerous challenges, ranging from sparse measurements (in-situ measuring satellites vs. global coverage), contaminated detectors, strong flux variation in space and time and finally the conversion of flux measurements into (3D) ionization profiles. This presentation will give an overview of the general setup, discuss main aspects in modeling particle precipitation and present some recent advances with the help of the Atmospheric Ionization Module OSnabrueck (AIMOS). AIMOS is based on a Geant4 Monte-Carlo Simulation for particle interactions with the atmosphere and in-situ particle measurements from the POES and GOES satellites.

Maik Wissing, Jan; Kallenrode, May-Britt

31

Dispersion of aerosol particles in the atmosphere: Fukushima  

NASA Astrophysics Data System (ADS)

Investigation of dispersion and deposition of aerosol particles in the atmosphere is an essential issue, because they have an effect on the biosphere and atmosphere. Moreover, aerosol particles have different transport properties and chemical and physical transformations in the atmosphere compared to gas phase air pollutants. The motion of a particle is described by a set of ordinary differential equations. The large-scale dynamics in the horizontal direction can be described by the equations of passive scalar advection, but in the vertical direction a well-defined terminal velocity should be taken into account as a term added to the vertical wind component. In the planetary boundary layer turbulent diffusion has an important role in the particle dispersion, which is taken into account by adding stochastic terms to the deterministic equations above. Wet deposition is also an essential process in the lower levels of the atmosphere, however, its precise parameterization is a challenge. For the simulations the wind field and other necessary data were taken from the ECMWF ERA-Interim database. In the case of the Fukushima Daiichi nuclear disaster (March-April 2011) radioactive aerosol particles were also released in the planetary boundary layer. Simulations (included the continuous and varying emission from the nuclear power plant) will be presented for the period of 14-23 March. Results show that wet deposition also has to be taken into consideration in the lower levels of the atmosphere. Furthermore, dynamical system characteristics are evaluated for the aerosol particle dynamics. The escape rate of particles was estimated both with and without turbulent diffusion, and in both cases when there was no wet deposition and also when wet deposition was taken into consideration.

Haszpra, Tķmea; Lagzi, Istvįn; Tél, Tamįs

2013-04-01

32

Scattering and Absorption by Nonspherical Particles in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

The atmospheres of Mars, the giant planets, and Titan all support populations of nonspherical particles. Analyses of observations of these atmospheres therefore rely on an understanding of the optical properties of nonspherical particles. We can glean information on particle size and composition from the wavelength dependence of the optical depth and from the shape of the forward peak of the scattering phase function. Additional information comes from polarization measurements which have been especially fruitful for Titan's haze. The Mars atmosphere contains mineral dust particles with effective radii near 1.6 micro meters, and water ice particles with radii between about 1 and 4 micro meters. The uppermost tropospheric hazes in Jupiter and Saturn are composed of ice crystals of ammonia, water and possibly traces of ammonium hydrosulfide, Methane ice and hydrogen sulfide ice are present in the atmospheres of Uranus and Neptune. Size estimation for these hazes in the giant planets is difficult, and even the expected spectral signatures are elusive, Titan's haze is both forward scattering and strongly polarized - a combination which points toward a fractal aggregate struc1.ure of 10 - 100 or more organic monomers whose radius is about 0.06 micro meters. Polar stratospheric hazes on Jupiter and Saturn also display this characteristic.

West, Robert A.

2005-01-01

33

Evolution of Soot Particle Morphology and Mixing State in the Atmosphere  

NASA Astrophysics Data System (ADS)

Soot particles (aka black carbon) impact the environment and climate by affecting Earth's radiation balance, cloud microphysics, and atmospheric chemistry. The complex morphology and mixing state of soot particles influence their optical properties and therefore their radiative forcing, the particles' transport, lifecycle, and heterogeneous chemistry. How soot morphology and mixing state alter during transport from the source to remote areas is still not well understood. While aging, soot particles can change shape, oxidize and mix, and become coated by organic and inorganic materials. In this study, we investigate the morphological and mixing state evolution of single soot particles in different stages of their 'life' in the atmosphere. This analysis will include an overview of several samples collected in various locations and atmospheric conditions: 1) particles freshly emitted near freeway on-ramps in Southern Michigan (USA); 2) particles emitted in two biomass burning events in New Mexico (USA), one close to the sampling location and another hundreds of miles away; 3) particles in the urban atmosphere of Mexico City and in the uplifted boundary layer captured on the top of the Pico de Tres Padres Mountain (on the north edge of Mexico City); 4) particles collected in the Sacramento urban area and the Sierra Nevada foothills (CA, USA); 5) particles collected in Detling (UK), and mostly transported from London, and 6) long-range transported particles in the free troposphere and collected at the Pico Mountain Observatory, located near the top of the Pico Volcano in the Azores (Portugal). We analyzed a large number of individual particles using electron microscopy and X-ray spectroscopy followed by image analysis. The projected structural properties of soot particles were characterized using size (maximum length, maximum width, and area equivalent diameter) and shape descriptors (e.g., aspect ratio, roundness, and convexity). The particle mass-fractal dimensions were determined using the ensemble method. The mixing state was analyzed by classifying soot particles based on visual inspection of coating and morphology. Soot particles freshly emitted by anthropogenic sources show less coating and more open chain-like structures; on the other hand biomass burning and long-range transported soot particles appear to be mostly coated and exhibit very compacted shapes. However, soot processing in urban atmospheres results in a complex mixture of coated and uncoated particles with a variety of morphologies and mixing states.

Mazzoleni, C.; China, S.; Sharma, N.; Gorkowski, K.; Dubey, M.; Aiken, A. C.; Zaveri, R. A.; Salvadori, N.; Chakrabarty, R. K.; Moosmuller, H.; Onasch, T. B.; Herndon, S.; Williams, L. R.; Liu, S.; Dzepina, K.; Helmig, D.; Hueber, J.; Fialho, P. J.; Mazzoleni, L. R.; kumar, S.; Dziobak, M.; Wright, K.

2013-12-01

34

Submicron particle characteristics of atmospheres in a long highway tunnel.  

PubMed

This study used a scanning mobility particle sizer (SMPS) to measure and categorize submicron atmospheric particles in the 14-737-nm size range for ambient and urban roadside air and for air in the Hsuehshan Tunnel (12.9 km), Taiwan. Principal component analysis, traffic flow, and particle size distributions were used to identify the emission characteristics of light-duty vehicles (LDV) with the SMPS data. In the Hsuehshan Tunnel, the particle size from the majority of emissions discharged by LDV is approximately 20-60 nm, and the maximum particle number can reach up to 2.5?×?10(5). In contrast, submicron particle size distribution for urban roadsides is mostly 14-200 nm, and the maximum particle number is approximately 4?×?10(4) with the particle number for most particle sizes being below 1,200. The submicron particle size distribution at the ambient air station was unimodal with a mode sizes at 30-50 nm with the maximum particle number of 3,000. PMID:24939711

Hwa, Mei-Yin; Yu, Tai-Yi

2014-10-01

35

Discrimination of airborne material particles from light scattering (TAOS) patterns  

NASA Astrophysics Data System (ADS)

Two-dimensional angle-resolved optical scattering (TAOS) is an experimental method which collects the intensity pattern of monochromatic light scattered by a single, micron-sized airborne particle. In general, the interpretation of these patterns and the retrieval of the particle refractive index, shape or size alone, are difficult problems. The solution proposed herewith relies on a learning machine (LM): rather than identifying airborne particles from their scattering patterns, TAOS patterns themselves are classified. The LM consists of two interacting modules: a feature extraction module and a linear classifier. Feature extraction relies on spectrum enhancement, which includes the discrete cosine Fourier transform and non-linear operations. Linear classification relies on multivariate statistical analysis. Interaction enables supervised training of the LM. The application described in this article aims at discriminating the TAOS patterns of single bacterial spores (Bacillus subtilis) from patterns of atmospheric aerosol and diesel soot particles. The latter are known to interfere with the detection of bacterial spores. Classification has been applied to a data set with more than 3000 TAOS patterns from various materials. Some classification experiments are described, where the size of training sets has been varied as well as many other parameters which control the classifier. By assuming all training and recognition patterns to come from the respective reference materials only, the most satisfactory classification result corresponds to ? 20% false negatives from Bacillus subtilis particles and <= 11% false positives from environmental and diesel particles.

Crosta, Giovanni F.; Pan, Yong-Le; Videen, Gorden; Aptowicz, Kevin B.; Chang, Richard K.

2013-05-01

36

Atmospheric cosmic rays and solar energetic particles at aircraft altitudes  

Microsoft Academic Search

Galactic cosmic rays, which are thought to be produced and accelerated by a variety of mechanisms in the Milky Way galaxy, interact with the solar wind, the earth's magnetic field, and its atmosphere to produce hadron, lepton, and photon fields at aircraft altitudes that are quite unlike anything produced in the laboratory. The energy spectra of these secondary particles extend

D. F. Smart

1996-01-01

37

Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K  

NASA Astrophysics Data System (ADS)

Ice formation induced by atmospheric particles through heterogeneous nucleation is not well understood. Onset conditions for heterogeneous ice nucleation and water uptake by particles collected in Los Angeles and Mexico City were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). Four dominant particle types were identified including soot associated with organics, soot with organic and inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn-containing particles apportioned to emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Above 230 K, significant differences in onsets of water uptake and immersion freezing of different particle types were observed. Below 230 K, particles exhibited high deposition ice nucleation efficiencies and formed ice atRHicewell below homogeneous ice nucleation limits. The data suggest that water uptake and immersion freezing are more sensitive to changes in particle chemical composition compared to deposition ice nucleation. The data demonstrate that anthropogenic and marine influenced particles, exhibiting various chemical and physical properties, possess distinctly different ice nucleation efficiencies and can serve as efficient IN at atmospheric conditions typical for cirrus and mixed-phase clouds.

Wang, Bingbing; Laskin, Alexander; Roedel, Tobias; Gilles, Mary K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

2011-11-01

38

Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K  

NASA Astrophysics Data System (ADS)

Ice formation induced by atmospheric particles through heterogeneous nucleation is not well understood. Onset conditions for heterogeneous ice nucleation and water uptake by particles collected in Los Angeles and Mexico City were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). Four dominant particle types were identified including soot associated with organics, soot with organic and inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn-containing particles apportioned to emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Above 230 K, significant differences in onsets of water uptake and immersion freezing of different particle types were observed. Below 230 K, particles exhibited high deposition ice nucleation efficiencies and formed ice atRHicewell below homogeneous ice nucleation limits. The data suggest that water uptake and immersion freezing are more sensitive to changes in particle chemical composition compared to deposition ice nucleation. The data demonstrate that anthropogenic and marine influenced particles, exhibiting various chemical and physical properties, possess distinctly different ice nucleation efficiencies and can serve as efficient IN at atmospheric conditions typical for cirrus and mixed-phase clouds.

Wang, Bingbing; Laskin, Alexander; Roedel, Tobias; Gilles, Mary K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

2012-09-01

39

Atmospheric Condensational Properties of Ultrafine Chain and Fractal Aerosol Particles  

NASA Technical Reports Server (NTRS)

The purpose for the research sponsored by this grant was to lay the foundations for qualitative understanding and quantitative description of the equilibrium vapor pressure of water vapor over the irregularly shaped, carbonaceous particles that are present in the atmosphere. This work apparently was the first systematic treatment of the subject. Research was conducted in two complementary components: 1. Calculations were performed of the equilibrium vapor pressure of water over particles comprised of aggregates of spheres in the 50-200 nm radius range. The purposes of this work were two-fold. First, since no systematic treatment of this subject had previously been conducted, its availability would be directly useful for quantitative treatment for a limited range of atmospheric aerosols. Second, it would provide qualitative indications of the effects of highly irregular particle shape on equilibrium vapor pressure of aggregates comprised of smaller spheres.

Marlow, William H.

1997-01-01

40

Size and composition distribution of atmospheric particles in southern California  

SciTech Connect

Continuous measurements of single particle size and chemical composition in the atmosphere are made using aerosol time-of-flight mass spectrometers (ATOFMS) operated alongside more conventional reference air sampling instruments at a network of three urban air monitoring sites in southern California. Electrical aerosol analyzers and optical particle counters are employed to acquire continuous particle size distribution data, and inertial impactor and bulk filter samples with 4-h resolution are taken for determination of particle size and chemical composition. Filter and impactor samples also are taken upwind of the air basin at Santa Catalina Island in order to characterize background air quality. The airborne particle size and composition distribution as measured by the cascade impactors at inland sites differ from that over the ocean principally due to depletion of sea salt particles accompanied by the addition of fine carbon-containing particles and secondary aerosol nitrate. Data from the ATOFMS systems create a continuous time series of sodium-, ammonium-, nitrate-, and carbon-containing particle counts that provide a high-resolution view of differences in particle composition as a function of location in the air basin. Results show that the characteristic peak in the Los Angeles area aerosol mass distribution in the 0.2--0.3-{micro}m size range observed during the 1987 SCAQS experiments has been reduced, consistent with reductions in diesel soot and elemental carbon emissions since that time.

Hughes, L.S.; Allen, J.O.; Kleeman, M.J. [and others] [and others

1999-10-15

41

Particle motion in atmospheric boundary layers of Mars and Earth  

NASA Technical Reports Server (NTRS)

To study the eolian mechanics of saltating particles, both an experimental investigation of the flow field around a model crater in an atmospheric boundary layer wind tunnel and numerical solutions of the two- and three-dimensional equations of motion of a single particle under the influence of a turbulent boundary layer were conducted. Two-dimensional particle motion was calculated for flow near the surfaces of both Earth and Mars. For the case of Earth both a turbulent boundary layer with a viscous sublayer and one without were calculated. For the case of Mars it was only necessary to calculate turbulent boundary layer flow with a laminar sublayer because of the low values of friction Reynolds number; however, it was necessary to include the effects of slip flow on a particle caused by the rarefied Martian atmosphere. In the equations of motion the lift force functions were developed to act on a single particle only in the laminar sublayer or a corresponding small region of high shear near the surface for a fully turbulent boundary layer. The lift force functions were developed from the analytical work by Saffman concerning the lift force acting on a particle in simple shear flow.

White, B. R.; Iversen, J. D.; Greeley, R.; Pollack, J. B.

1975-01-01

42

Impact of aerosols and atmospheric particles on plant leaf proteins  

NASA Astrophysics Data System (ADS)

Aerosols and atmospheric particles can diffuse and absorb solar radiation, and directly affect plant photosynthesis and related protein expression. In this study, for the first time, we performed an extensive investigation of the effects of aerosols and atmospheric particles on plant leaf proteins by combining Geographic Information System and proteomic approaches. Data on particles with diameters of 0.1-1.0 ?m (PM1) from different locations across the city of Beijing and the aerosol optical depth (AOD) over the past 6 years (2007-2012) were collected. In order to make the study more reliable, we segregated the influence of soil pollution by measuring the heavy metal content. On the basis of AOD and PM1, two regions corresponding to strong and weak diffuse solar radiations were selected for analyzing the changes in the expression of plant proteins. Our results demonstrated that in areas with strong diffuse solar radiations, plant ribulose bisphosphate carboxylase was expressed at higher levels, but oxygen evolved in enhancer protein and light-harvesting complex II protein were expressed at lower levels. The expression of ATP synthase subunit beta and chlorophyll a-b binding protein were similar in both regions. By analyzing the changes in the expression of these leaf proteins and their functions, we conclude that aerosols and atmospheric particles stimulate plant photosynthesis facilitated by diffuse solar radiations.

Yan, Xing; Shi, Wen Z.; Zhao, Wen J.; Luo, Na N.

2014-05-01

43

Internally mixed atmospheric aerosol particles: Hygroscopic growth and light scattering  

NASA Astrophysics Data System (ADS)

Internally mixed aerosol particles consisting of one or more hygroscopic compounds can contain both solid and liquid parts, the details depending on the relative humidity (RH). The solid-to-liquid transition of such particles as the RH increases influences their light-scattering properties through changes in particle shape, size, and refractive index. Most techniques used to analyze ambient aerosol particles do not have the ability to view both solid and liquid phases within individual particles. Using a transmission electron microscope fitted with an environmental cell (ETEM), we analyzed laboratory-prepared and ambient aerosol samples. Our results suggest that solid inclusions inside aqueous droplets at high RH values (e.g., >65%) are likely to be common in atmospheric particles. In order to assess the effects of such inclusions, we calculated their combined light-scattering efficiencies using a discrete dipole approximation (DDA). The results show differences compared to those from a core-shell model, with an average increase in light scattering of ˜20%. The results demonstrate that the combination of ETEM measurements of ambient particles with DDA calculations yields new insights into the effects of inclusions on the light-scattering properties of internally mixed particles.

Freney, Evelyn J.; Adachi, Kouji; Buseck, Peter R.

2010-10-01

44

Modelling of externally mixed particles in the atmosphere  

NASA Astrophysics Data System (ADS)

Particles present in the atmosphere have significant impacts on climate as well as on human health. Thus, it is important to accurately simulate and forecast their concentrations. Most commonly used air quality models assume that particles are internally mixed, largely for computational reasons. However, this assumption is disproved by measurements, especially close to sources. In fact, the externally-mixed properties of particles are important for aerosol source identification, radiative effects and particle evolution. In this study, a new size-composition resolved aerosol model is developed. It can solve the aerosol dynamic evolution for external mixtures taking into account the processes of coagulation, condensation and nucleation. Both the size of particles and the mass fraction of each chemical compound are discretized. For a given particle size, particles of different chemical composition may co-exist. Aerosol dynamics is solved in each grid cell by splitting coagulation and condensation/evaporation-nucleation processes. For the condensation/evaporation, surface equilibrium between gas and aerosol is calculated based on ISORROPIA and the newly developed H2O (Hydrophilic/Hydrophobic Organic) Model. Because size and chemical composition sections evolve during condensation/evaporation, concentrations need to be redistributed on fixed sections after condensation/evaporation to be able to use the model in 3 dimensions. This is done based on the numerical scheme HEMEN, which was initially developed for size redistribution. Chemical components can be grouped into several aggregates to reduce computational cost. The 0D model is validated by comparison to results obtained for internally mixed particles and the effect of mixing is investigated for up to 31 species and 4 aggregates. The model will be integrated into the air quality modeling platform POLYPHEMUS to investigate its performance in modeling air quality by comparing with observations during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) campaign in July 2009.

ZHU, Shupeng; Sartelet, Karine; Seigneur, Christian

2014-05-01

45

Acidic sulfate particles in the winter Arctic atmosphere  

NASA Astrophysics Data System (ADS)

Particle samples were collected by aircraft in the vicinity of Barrow, Alaska, the North Pole, and over the North Atlantic north of Bodo, Norway, during March and April, 1983 as part of the Atmospheric Gas and Aerosol Sampling Program. The sulfate concentrations and aerosol acidities from each of the regions were similar. The average sulfate concentration was 3.2 ± 1.3 µg m-3. The aerosol acidity was equivalent to 41 ± 13% of the sulfate.

Lazrus, Allan L.; Ferek, Ronald J.

46

Field and Laboratory Studies of Reactions between Atmospheric Water Soluble Organic Acids and Inorganic Particles  

SciTech Connect

Atmospheric inorganic particles undergo complex heterogeneous reactions that change their physicochemical properties. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of chlorides with inorganic acids, such as nitric and sulfuric acids [1-2]. Recently, we showed that NaCl can react with water soluble organic acids (WSOA) and release gaseous hydrochloric acid (HCl) resulting in formation of organic salts [3]. A similar mechanism is also applicable to mixed WSOA/nitrate particles where multi-phase reactions are driven by the volatility of nitric acid. Furthermore, secondary organic material, which is a complex mixture of carboxylic acids, exhibits the same reactivity towards chlorides and nitrates. Here, we present a systematic study of reactions between atmospheric relevant WSOA, SOM, and inorganic salts including NaCl, NaNO3, and Ca(NO3)2 using complementary micro-spectroscopy analysis.

Wang, Bingbing; Kelly, Stephen T.; Sellon, Rachel E.; Shilling, John E.; Tivanski, Alexei V.; Moffet, Ryan C.; Gilles, Mary K.; Laskin, Alexander

2013-06-25

47

Measurements of the physical properties of particles in the urban atmosphere  

Microsoft Academic Search

Measurements of the physical properties of particles in the atmosphere of a UK urban area have been made, including particle number count by condensation nucleus counters with different lower particle size cut-offs; particle size distributions using a Scanning Mobility Particle Sizer; total particle Fuchs surface area using an epiphaniometer and particle mass using Tapered Element Oscillating Micro-balance (TEOM) instruments with

Roy M Harrison; Marcus Jones; Gareth Collins

1999-01-01

48

Quantitative ED-EPMA of Individual Particles and its Application for Characterization of Atmospheric Aerosol Particles  

NASA Astrophysics Data System (ADS)

An electron probe X-ray microanalysis (EPMA) technique using an energy-dispersive X-ray detector with an ultra-thin window, named low-Z particle EPMA, 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 (ED-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. In addition, an expert system that can perform chemical speciation from the elemental composition data obtained by the low-Z particle EPMA has been developed. The low-Z particle EPMA was applied to characterize K-feldspar particle samples of which the chemical compositions are well defined by the use of various bulk analytical methods. Chemical compositions of the K-feldspar samples obtained from the low-Z particle EPMA turn out to be very close to those from bulk analyses. The low-Z particle EPMA technique has been applied for the characterization of atmospheric aerosol particle samples, including Asian dust, urban, and indoor particulate samples: (1) The extent of chemical modification of Asian dust particles sampled in Chuncheon and Incheon, Korea, during several Asian dust storm events occurred in 2002-2006 was investigated. Mixing of Asian dust with air pollutants and sea-salts strongly depends on the characteristics of Asian dust storm events such as air-mass backward trajectories. For instance, no significant chemical modification of mineral dust corresponded to fast moving air-masses at high altitudes. Inversely, extensive chemical modification was correlated with longer residence times over the continent (interaction with anthropogenic emissions) and in marine atmosphere (coagulation with deliquesced sea-salts). (2) Six urban aerosol samples collected in a megacity of Korea, namely Incheon, during a period of March 9-15, 2006 were characterized. Many different particle types, such as "soil-derived particles", "reacted sea-salts", "reacted CaCO3-containing particles", "genuine sea-salts", "reacted sea-salts + others", "Fe-containing particles", "anthropogenic organics", (NH4)2SO4, "K-containing particles", and "fly ashes", can be identified and their emission source, transport, and reactivity in the air can be elucidated. Also, different characteristics of the samples were clearly revealed. (3) When the technique was applied for the characterization of indoor subway station aerosols, it was observed that iron-containing particles are predominant. Agglomerated iron-containing particles, nano-size particles adsorbed on the other particles, and partially oxidized iron particles were frequently encountered, which implies that Iron-containing particles are generated mainly by the friction between break pad, wheel, and rails.

Ro, C.

2008-12-01

49

Toxicity of atmospheric particle-bound PAHs: an environmental perspective.  

PubMed

Atmospheric polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that represent a risk not only to humans, but to all living organisms. High-molecular weight PAHs are more toxic than lighter relatives, and also have a higher tendency to bind onto air particles (i.e., particle matter, PM). PM is a major constituent of air pollution. Adequate assessment of the biological impact of PM requires the analysis, not only of the effects on human health, but also on the environment. Since the aquatic systems work as a natural sink to these air pollutants, assessing the effects of particle-bound PAHs on aquatic organisms may further characterize its potential aquatic toxicity, also providing simple and low-cost alternative assays to investigate PM biological effects in vivo. We review the current scientific literature, addressing the atmospheric PAHs fate, transformation and deposition, pertinent particle-bound PAHs toxicity data, and the potential aquatic toxic burden. Conceptual and experimental procedures that could improve future investigations and risk assessments are also considered. PMID:24595747

Mesquita, Sofia Raquel; L van Drooge, Barend; Barata, Carlos; Vieira, Natividade; Guimarćes, Laura; Pińa, Benjamin

2014-10-01

50

Effects of energetic particle precipitation on the atmospheric electric circuit  

SciTech Connect

The solar particle event (SPE) of August 1972 is one of the largest that has occurred in the last 20 years. Since it is so well documented, it can serve as a good example of a major perturbation to the atmospheric electric system. In this paper, ion production rates and conductivities from the ground to 80 km at the peak intensity of the event on August 4 and for 30, 35, and 40 km for the 6-day duration of the event are presented. At the peak of the event, the proton and electron precipitation currents, the ohmic current, and the vertical electric field are calculated inside the polar cap. The particle precipitation currents at this time greatly exceed the normal air earth current at altitudes above 30 km and produce reversals in the vertical electric field at 28 km and above. Calculations are presented of the vertical electric field at altitudes near 30 km where balloon measurements were made. Good agreement between the calculated and the measured vertical electric field verifies our ability to calculate disturbed conductivities at these altitudes from satellite measurements of proton spectra incident on the atmosphere. Despite the fact that at the peak of the event the vertical electric field near 30 km was shorted out by the solar particles and that the current carried by the solar particles exceeded the fair weather air-earth current density in the stratosphere by large factors, it is concluded that the largest effect of an SPE of this magnitude on the atmospheric electric circuit is due to the Forbush decrease in the galactic cosmic ray flux rather than to the large increase in solar proton flux.

Reagan, J.B.; Meyerott, R.E.; Evans, J.E.; Imhof, W.L.; Joiner, R.G.

1983-04-20

51

Properties of submicron particles in Atmospheric Brown Clouds  

NASA Astrophysics Data System (ADS)

The Atmospheric Brown Clouds (ABC) is an important problem of this century. Investigations of last years and satellite data show that the ABC (or brown gas, smog, fog) cover extensive territories including the whole continents and oceans. The brown gas consists of a mixture of particles of anthropogenic sulfates, nitrates, organic origin, black carbon, dust, ashes, and also natural aerosols such as sea salt and mineral dust. The brown color is a result of absorption and scattering of solar radiation by the anthropogenic black carbon, ashes, the particles of salt dust, and nitrogen dioxide. The investigation of the ABC is a fundamental problem for prevention of degradation of the environment. At present in the CIS in-situ investigations of the ABC are carried out on Lidar Station Teplokluchenka (Kyrgyz Republic). Here, we present the results of experimental investigation of submicron (nanoscale) particles originating from the ABC and the properties of the particles. Samples of dust precipitating from the ABC were obtained at the area of Lidar Station Teplokluchenka as well as scientific station of the Russian Academy of Sciences near Bishkek. The data for determination of the grain composition were obtained with the aid of the scanning electron microscopes JEOL 6460 LV and Philips XL 30 FEG. Analysis of the properties of the particles was performed by means of the X-ray diffraction using diffractometer Siemens D5000. The images of the grains were mapped. The investigation allows us to get (after the image processing) the grain composition within the dust particle size range of 60 nm to 700 ?m. Distributions of nano- and microscale particles in sizes were constructed using Rozin-Rammler coordinates. Analysis of the distributions shows that the ABC contain submicron (nanoscale) particles; 2) at higher altitudes the concentration of the submicron (nanoscale) particles in the ABC is higher than at lower altitudes. The chemical compositions of the particles are shown to be close to those typical for the ABC. We present also the results of the study of morphology and mineralogical composition of the obtained particles as well as their magnetic properties. This study was supported by the Division of Earth Sciences, Russian Academy of Sciences (research program "Nanoscale particles in nature and technogenic products: conditions of existence, physical and chemical properties, and mechanisms of formation") and by ISTC (project No. KR-1522).

Adushkin, V. V.; Chen, B. B.; Dubovskoi, A. N.; Friedrich, F.; Pernik, L. M.; Popel, S. I.; Weidler, P. G.

2010-05-01

52

INVESTIGATIONS OF HYGROSCOPIC GROWTH AND PHASE TRANSITIONS OF ATMOSPHERIC PARTICLES BY NONCONTACT  

E-print Network

.bnl.gov ABSTRACT Aerosol particles (nanometer to micrometer sized particles suspended in air) affect atmosphericINVESTIGATIONS OF HYGROSCOPIC GROWTH AND PHASE TRANSITIONS OF ATMOSPHERIC PARTICLES BY NONCONTACT to accurate climate modeling. The processes by which initially hydrophobic particles become hygroscopic

53

DERIVATION OF DAMAGE FUNCTIONS FOR ATMOSPHERIC DEGRADATION OF MATERIALS  

EPA Science Inventory

The information in the pape is directed to those who develop and use damage functions which relate atmospheric degradation of materials to various causal agents in the atmosphere. Such relationships must be quantified mathematically as part of the overall cost-benefit considerati...

54

Neutrons for probing the ice nucleation on atmospheric soot particles  

NASA Astrophysics Data System (ADS)

Soot resulting from combustion of kerosene in aircraft engines can act as condensation nuclei for water/ice in the atmosphere and promote the formation of contrails that turn into artificial cirrus clouds and affect the climate. The mechanisms of nucleation of water/ice particles are not well identified. Studies "in situ" are difficult to realize, so we try to determine by neutron diffraction the nucleation of water/ice adsorbed on soot collected at the outlet of an aircraft engine combustor within the conditions of the upper troposphere. The results are compared with those obtained on model laboratory soot. The comparison highlights the role of chemical impurities and structural defects of original aircraft engine soot on the nucleation of water/ice in atmospheric conditions.

Demirdjian, B.; Tishkova, V.; Ferry, D.

2012-11-01

55

Phase Transitions and Phase Miscibility of Mixed Particles of Ammonium Sulfate, Toluene-Derived Secondary Organic Material,  

E-print Network

related to air quality and climate. The phases of particles containing secondary organic materials (SOMsPhase Transitions and Phase Miscibility of Mixed Particles of Ammonium Sulfate, Toluene ABSTRACT: The phase states of atmospheric particles influence their roles in physicochemical processes

56

Graphene: from materials science to particle physics  

E-print Network

Since its discovery in 2004, graphene, a two-dimensional hexagonal carbon allotrope, has generated great interest and spurred research activity from materials science to particle physics and vice versa. In particular, graphene has been found to exhibit outstanding electronic and mechanical properties, as well as an unusual low-energy spectrum of Dirac quasiparticles giving rise to a fractional quantum Hall effect when freely suspended and immersed in a magnetic field. One of the most intriguing puzzles of graphene involves the low-temperature conductivity at zero density, a central issue in the design of graphene-based nanoelectronic components. While suspended graphene experiments have shown a trend reminiscent of semiconductors, with rising resistivity at low temperatures, most theories predict a constant or even decreasing resistivity. However, lattice field theory calculations have revealed that suspended graphene is at or near the critical coupling for excitonic gap formation due to strong Coulomb intera...

Drut, Joaquķn E; Tölö, Eero

2010-01-01

57

Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions  

NASA Astrophysics Data System (ADS)

The results on heterogeneous ozonation of a phenylurea pesticide, isoproturon, under atmospheric conditions are presented for the first time in the present study. The study was carried out using an experimental device previously adopted and validated for the heterogeneous reactivity of organics toward ozone (Pflieger et al., 2011). Isoproturon was adsorbed on silica particles via a liquid-to-solid equilibrium with a load far below a monolayer (0.02% by weight/surface coverage of 0.5%). The rate constants were estimated by measuring the consumption of the organic (dark, T = 26 °C, RH < 1%). The experimental data were fitted by both the modified Langmuir-Hinshelwood and the Eley-Rideal patterns, resulting in atmospheric lifetimes of heterogeneous ozonation of 4 and 6 days, respectively (for 40 ppb of O3). Parameters, such as the number and the quantity of pesticides adsorbed on the solid support, which can significantly influence the heterogeneous kinetics, were investigated as well. The results obtained suggest that the organic compound is adsorbed in multilayer aggregates on the aerosol even though submonolayer coverage is assumed. The presence of a second herbicide, trifluralin, together with isoproturon on the aerosol surface does not affect the kinetics of ozonation, indicating that both compounds are adsorbed on different surface sites of silica particles.

Pflieger, Maryline; Grgi?, Irena; Kitanovski, Zoran

2012-12-01

58

Drift movement of aerosol particles in field of atmospheric gravity waves  

Microsoft Academic Search

Internal gravity waves exert an influence on the energetics and dynamics of the upper layers of the atmosphere. Their influence on the motion of fine particles in the atmosphere is clarified. This is important in analyzing the reactions of particles of natural atmospheric aerosol to wave perturbations of the IGW type. The behavior of artificial clouds of tiny metallized bodies

S. K. Rozenfeld

1984-01-01

59

An evaluation of optical particle counter measurements of the dry deposition of atmospheric aerosol particles  

Microsoft Academic Search

Eddy correlation flux measurements of total atmospheric aerosol particulates were collected over a grass surface at Champaign, Illinois, in June 1982. PMS ASAS-300A and Royco 225 optical particle counters were used as sensors to measure fluxes in four size ranges from 0.15 to 2.5 mum. The fluxes were quite variable, both in time and between sensors. The sensor signals are

Paul C. Katen; John M. Hubbe

1985-01-01

60

Wood-based building materials and atmospheric carbon emissions  

Microsoft Academic Search

This study investigates the global impact of wood as a building material by considering emissions of carbon dioxide to the atmosphere. Wood is compared with other materials in terms of stored carbon and emissions of carbon dioxide from fossil fuel energy used in manufacturing. An analysis of typical forms of building construction shows that wood buildings require much lower process

Andrew H Buchanan; S. Bry Levine

1999-01-01

61

Energetic particle energy deposition in Titan's upper atmosphere  

NASA Astrophysics Data System (ADS)

Titan’s upper atmosphere has been observed to be variable on a pass-by-pass basis. During the nominal mission where the Cassini Ion and Neutral Mass Spectrometer (INMS) only sampled the northern hemisphere this variability was initially believed to be tied to solar drivers manifest in latitudinal variations in the thermal structure of the upper atmosphere. However, when Cassini delved into the southern hemisphere the latitudinal dependence was not present in the data. Recently, Westlake et al. (2011) showed that the pass-by-pass variability is correlated with the deviations in the plasma environment as identified by Rymer et al. (2009) and Simon et al. (2010). Furthermore, the studies of Westlake et al. (2011) and Bell et al. (2011) showed that Titan’s upper atmosphere responds to changes in the ambient magnetospheric plasma on timescales of roughly one Titan day (16 Earth days). We report on recent studies of energy deposition in Titan’s upper atmosphere. Previous studies by Smith et al. (2009), Cravens et al. (2008), Tseng et al. (2008), and Shah et al. (2009) reported on energetic proton and oxygen ion precipitation. Back of the envelope calculations by Sittler et al. (2009) showed that magnetospheric energy inputs are expected to be of the order of or greater than the solar processes. We report on further analysis of the plasma environment around Titan during the flybys that the INMS has good data. We utilize data from the Magnetospheric Imaging Instrument to determine how the magnetospheric particle population varies from pass to pass and how this influences the net magnetospheric energy input prior to the flyby. We also report on enhanced energetic neutral atom emissions during select highly energetic passes. References: Bell, J., et al.: “Simulating the time-dependent response of Titan's upper atmosphere to periods of magnetospheric forcing”. Geophys. Res. Lett., Vol. 38, L06202, 2011. Rymer, A. M., et al.: “Discrete classification and electron energy spectra of Titan’s varied magnetospheric environment”. Geophys. Res. Lett., Vol. 36, L15109, 2009. Simon, S., et al.: “Titan’s highly dynamic magnetic environment: A systematic survey of Cassini magnetometer observations from flybys TA-T62”. Planet. Space. Sci., Vol 58, pp. 1230-1251, 2010. Sittler, E., et al.: “Energy deposition processes in Titan’s upper atmosphere and its induced magnetosphere”. In Titan from Cassini-Huygens. 2009. Tseng, W.-L, et al.: “Exospheric heating by pickup ions at Titan”. Adv. Space Res. Vol 42. Pp 54-60, 2008. Westlake, J. H., et al.: “Titan’s thermospheric response to various plasma environments”. J. Geophys. Res., Vol. 116, A03

Westlake, J. H.; Smith, H. T.; Mitchell, D. G.; Paranicas, C. P.; Rymer, A. M.; Bell, J. M.; Waite, J. H., Jr.; Mandt, K. E.

2012-04-01

62

A test-particle model of the atmosphere/ionosphere system of Saturn's main rings  

E-print Network

A test-particle model of the atmosphere/ionosphere system of Saturn's main rings M. Bouhram,1 R. E pass of the Cassini orbiter near the A and B rings of Saturn, formed mainly by H2O ice particles. Crary (2006), A test-particle model of the atmosphere/ionosphere system of Saturn's main rings, Geophys

Johnson, Robert E.

63

Microbiology and atmospheric processes: the role of biological particles in cloud physics  

Microsoft Academic Search

As part of a series of papers on the sources, distribution and potential impact of biological particles in the atmosphere, this paper introduces and summarizes the potential role of biological particles in atmospheric clouds. Biological particles like bacteria or pollen may be active as both cloud condensation nuclei (CCN) and heterogeneous ice nuclei (IN) and thereby can contribute to the

O. Möhler; P. J. Demott; G. Vali; Z. Levin

2007-01-01

64

Heterogeneous oxidation of atmospheric aerosol particles by gas-phase radicals  

Microsoft Academic Search

Atmospheric aerosol particles play pivotal roles in climate and air quality. Just as chemically reduced gases experience oxidation in the atmosphere, it is now apparent that solid and liquid atmospheric particulates are also subject to similar oxidative processes. The most reactive atmospheric gas-phase radicals, in particular the hydroxyl radical, readily promote such chemistry through surficial interactions. This Review looks at

I. J. George; J. P. D. Abbatt

2010-01-01

65

Hyperspectral material identification on radiance data using single-atmosphere or multiple-atmosphere modeling  

NASA Astrophysics Data System (ADS)

Reflectance-domain methods convert hyperspectral data from radiance to reflectance using an atmospheric compensation model. Material detection and identification are performed by comparing the compensated data to target reflectance spectra. We introduce two radiance-domain approaches, Single atmosphere Adaptive Cosine Estimator (SACE) and Multiple atmosphere ACE (MACE) in which the target reflectance spectra are instead converted into sensor-reaching radiance using physics-based models. For SACE, known illumination and atmospheric conditions are incorporated in a single atmospheric model. For MACE the conditions are unknown so the algorithm uses many atmospheric models to cover the range of environmental variability, and it approximates the result using a subspace model. This approach is sometimes called the invariant method, and requires the choice of a subspace dimension for the model. We compare these two radiance-domain approaches to a Reflectance-domain ACE (RACE) approach on a HYDICE image featuring concealed materials. All three algorithms use the ACE detector, and all three techniques are able to detect most of the hidden materials in the imagery. For MACE we observe a strong dependence on the choice of the material subspace dimension. Increasing this value can lead to a decline in performance.

Mariano, Adrian V.; Grossmann, John M.

2010-11-01

66

Graphene: from materials science to particle physics  

E-print Network

Since its discovery in 2004, graphene, a two-dimensional hexagonal carbon allotrope, has generated great interest and spurred research activity from materials science to particle physics and vice versa. In particular, graphene has been found to exhibit outstanding electronic and mechanical properties, as well as an unusual low-energy spectrum of Dirac quasiparticles giving rise to a fractional quantum Hall effect when freely suspended and immersed in a magnetic field. One of the most intriguing puzzles of graphene involves the low-temperature conductivity at zero density, a central issue in the design of graphene-based nanoelectronic components. While suspended graphene experiments have shown a trend reminiscent of semiconductors, with rising resistivity at low temperatures, most theories predict a constant or even decreasing resistivity. However, lattice field theory calculations have revealed that suspended graphene is at or near the critical coupling for excitonic gap formation due to strong Coulomb interactions, which suggests a simple and straightforward explanation for the experimental data. In this contribution we review the current status of the field with emphasis on the issue of gap formation, and outline recent progress and future points of contact between condensed matter physics and Lattice QCD.

Joaquķn E. Drut; Timo A. Lähde; Eero Tölö

2010-11-02

67

Effect of atmospheric electricity on dry deposition of airborne particles from atmosphere  

NASA Astrophysics Data System (ADS)

The electric mechanism of dry deposition is well known in the case of unattached radon daughter clusters that are unipolar charged and of high mobility. The problematic role of the electric forces in deposition of aerosol particles is theoretically examined by comparing the fluxes of particles carried by different deposition mechanisms in a model situation. The electric mechanism of deposition appears essential for particles of diameter 10-200 nm in conditions of low wind speed. The electric flux of fine particles can be dominant on the tips of leaves and needles even in a moderate atmospheric electric field of a few hundred V m -1 measured over the plane ground surface. The electric deposition is enhanced under thunderclouds and high voltage power lines. Strong wind suppresses the relative role of the electric deposition when compared with aerodynamic deposition. When compared with diffusion deposition the electric deposition appears less uniform: the precipitation particulate matter on the tips of leaves and especially on needles of top branches of conifer trees is much more intensive than on the ground surface and electrically shielded surfaces of plants. The knowledge of deposition geometry could improve our understanding of air pollution damage to plants.

Tammet, H.; Kimmel, V.; Israelsson, S.

68

Concentrations of PAHs in atmospheric particles (PM-10) and roadside soil particles collected in Kuala Lumpur, Malaysia  

NASA Astrophysics Data System (ADS)

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles and roadside soil particles were measured at eight locations in the city center and the suburb of Kuala Lumpur, Malaysia. Atmospheric particles were collected using high-volume PM-10 sampler on glass fiber filters over 24 h average sampling period. Both types of samples were extracted with dichloromethane by ultrasonic agitation. The extracts were then fractionated on an alumina-silica column and the aromatic fraction was subjected to gas chromatography-mass spectrometric (GC-MS) analysis. Total PAH concentrations in the atmospheric particles and roadside soil particles were found to be 6.28±4.35 ng m -3 and 0.22±0.11 ?g g -1, respectively. Benzo[ g, h, i]perylene and coronene were found to be the most abundant PAHs in airborne particles at all locations. The most abundant PAHs in the roadside soil particles were fluoranthene, pyrene and phenanthrene.

Omar, Nasr Yousef M. J.; Abas, M. Radzi Bin; Ketuly, Kamal Aziz; Tahir, Norhayati Mohd

69

Formation of highly porous aerosol particles by atmospheric freeze-drying in ice clouds  

PubMed Central

The cycling of atmospheric aerosols through clouds can change their chemical and physical properties and thus modify how aerosols affect cloud microphysics and, subsequently, precipitation and climate. Current knowledge about aerosol processing by clouds is rather limited to chemical reactions within water droplets in warm low-altitude clouds. However, in cold high-altitude cirrus clouds and anvils of high convective clouds in the tropics and midlatitudes, humidified aerosols freeze to form ice, which upon exposure to subsaturation conditions with respect to ice can sublimate, leaving behind residual modified aerosols. This freeze-drying process can occur in various types of clouds. Here we simulate an atmospheric freeze-drying cycle of aerosols in laboratory experiments using proxies for atmospheric aerosols. We find that aerosols that contain organic material that undergo such a process can form highly porous aerosol particles with a larger diameter and a lower density than the initial homogeneous aerosol. We attribute this morphology change to phase separation upon freezing followed by a glass transition of the organic material that can preserve a porous structure after ice sublimation. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. We find that highly porous aerosol particles scatter solar light less efficiently than nonporous aerosol particles. Using a combination of satellite and radiosonde data, we show that highly porous aerosol formation can readily occur in highly convective clouds, which are widespread in the tropics and midlatitudes. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges. PMID:24297908

Adler, Gabriela; Koop, Thomas; Haspel, Carynelisa; Taraniuk, Ilya; Moise, Tamar; Koren, Ilan; Heiblum, Reuven H.; Rudich, Yinon

2013-01-01

70

Analysis of Atmospheric Particles Deposited onto Mesquite Leaves in the Central Arizona -Phoenix LTER Area  

E-print Network

Analysis of Atmospheric Particles Deposited onto Mesquite Leaves in the Central Arizona - Phoenix statistics for large data sets: Applications to individual aerosol particles. Anal. Chem., 63, 2646) Urban fluid mechanics: Air circulation and contaminant dispersion in cities. Environmental Fluid

Hall, Sharon J.

71

Electromagnetic properties of Permendur granular composite materials containing flaky particles  

NASA Astrophysics Data System (ADS)

Electromagnetic properties of Permendur (Fe50Co50 alloy) granular composite materials containing flaky particle have been studied from the RF to microwave frequency range. Properties of the flaky particle composites were compared with the spherical particle ones. The electrical conductivity of the flaky particle composite was higher than that of the spherical particle composite at the same particle content. An insulator to metal transition was observed at the percolation threshold ?c in both composites. The ?c of the flaky particle composite was lower than that of the spherical one. The relative complex permittivity indicates that the insulating state has dielectric properties. For the spherical particle composite, the permittivity enhancement caused by particle cluster formation can be described by the effective cluster model (ECM). The enhancement of the dielectric constant in the flaky particle composite is larger than the ECM prediction. A negative permittivity spectrum indicating a low frequency plasmonic state was observed in the metallic 70 vol. % flaky particle composite. The relative complex permeability spectra of the flaky particle composite are different from those of the spherical one. The flaky particle composite shows a larger permeability value and lower permeability dispersion frequency than the spherical particle composite. Negative permeability spectra were observed in the both composite materials. The negative permeability frequency band of the flaky particle composite is lower than that of the spherical particle composite owing to the demagnetizing field effect.

Kasagi, Teruhiro; Tsutaoka, Takanori; Hatakeyama, Kenichi

2014-10-01

72

Seasonal differences of the atmospheric particle size distribution in a metropolitan area in Japan.  

PubMed

We compared the effect of ambient temperature observed in two different seasons on the size distribution and particle number concentration (PNC) as a function of distance (up to ~250 m) from a major traffic road (25% of the vehicles are heavy-duty diesel vehicles). The modal particle diameter was found between 10 and 30 nm at the roadside in the winter. However, there was no peak for this size range in the summer, even at the roadside. Ambient temperature affects both the atmospheric dilution ratio (DR) and the evaporation rate of particles, thus it affects the decay rate of PNC. We corrected the DR effect in order to focus on the effect of particle evaporation on PNC decay. The decay rate of PNC with DR was found to depend on the season and particle diameter. During the winter, the decay rate for smaller particles (<30 nm) was much higher (i.e., the concentration decreased significantly against DR), whereas it was low during the summer. In contrast, for particles >30 nm in diameter, the decay rate was nearly the same during both seasons. This distinction between particles less than or greater than 30 nm in diameter reflects differences in particle volatility properties. Mass-transfer theory was used to estimate evaporation rates of C20-C36 n-alkane particles, which are the major n-alkanes in diesel exhaust particles. The C20-C28 n-alkanes of 30-nm particles completely evaporate at 31.2 °C (summer), and their lifetime is shorter than the transport time of air masses in our region of interest. Absence of the peak at 10-30 nm and the low decay rate of PNC <30 nm in diameter in the summer were likely due to the evaporation of compounds of similar volatilities comparable to the C20-C36 n-alkanes from particles near the exhaust pipes of vehicles, and complete evaporation of semivolatile materials before they reached the roadside. These results suggest that the lifetime of particles <30 nm in diameter depends on the ambient temperature, which differs between seasons. This leads us to conclude that these particles show distinctly different spatial distributions depending on the season. PMID:22960110

Fujitani, Yuji; Kumar, Prashant; Tamura, Kenji; Fushimi, Akihiro; Hasegawa, Shuich; Takahashi, Katsuyuki; Tanabe, Kiyoshi; Kobayashi, Shinji; Hirano, Seishiro

2012-10-15

73

Investigating The Ionization of The Earth's Atmosphere At Large Energetic Particle Events  

NASA Astrophysics Data System (ADS)

To investigate the influence of energetic particle events on the terrestrial atmosphere (e.g. due to ionization and/or hadronic interaction) a number of aspects are under consideration, such as the species of the precipitating particles, their energies, fluences as well as a repetition rate of events. In preparation of a refined model of precipitating charged particle interactions with the atmosphere, we calculate the ionization in the earth's atmosphere for well- known recent events (e.g. the Bastille Day event on July 14, 2000) of high particle fluences by using computer simulations of the earth's atmosphere and in situ measured particle intensities. The changes in atmospheric chemistry derieved from this ionization are described in the accompanying contribution of M. von König et al. (Modelling the influence of large energetic particle events on the chemical composition of the middle and upper atmosphere). Although very effective for atmospheric chemistry, these events are too rare and too short-lived to contribute significantly to the atmospheric NOx budget on a long-time basis. However, McCracken et al. (2001) suggests from nitrate depositions in ice- cores that solar particle events have occured more frequently and with a higher in- tensity in historical times, and thus may have led to a greater impact than the events discussed above. Therefore, we evaluate the influence of large historical energetic particle events, such as NOx and Ozone behaviour due to atmospheric ionization at Carrington's white light flare in 1859.

Wolff, E.; Burrows, J.; Kallenrode, M.-B.; von König, M.; Künzi, K. F.; Quack, M.

74

Reference Material of Defined Particle Size: Quartz, BCR No. 132,  

National Technical Information Service (NTIS)

The report gives details of the Commission of the European Communities, Community Bureau of Reference (BCR) certification campaign on Reference Materials (RM) 132 which is a reference material of defined particle size distribution. The mass fraction of pa...

R. Wilson, D. Gould

1985-01-01

75

Atmospheric particles retrieval using satellite remote sensing: Applications for sandstorms and volcanic clouds  

Microsoft Academic Search

This thesis is concerned with atmospheric particles produced by sandstorms and volcanic eruptions. Three studies were conducted in order to examine particle retrieval methodology, and apply these towards an improved understanding of large-scale sandstorms. A thermal infrared remote sensing retrieval method developed by Wen and Rose [1994], which retrieves particle sizes, optical depth, and total masses of silicate particles in

Yingxin Gu

2004-01-01

76

Atmospheric corrosion of materials used in the civil construction industry  

Microsoft Academic Search

Purpose – The purpose of this study was to select an atmospheric corrosion evaluation methodology and to establish a range of relative corrosion penetration and\\/or progress values, which could be used as reference in the selection of materials for the civil construction industry. Design\\/methodology\\/approach – Salt spray, field tests, accelerated cyclic tests and accelerated field tests were used to evaluate

Egnalda Pereira da Silva; Evandro de Azevedo Alvarenga; Maria das Mercźs Reis de Castro; Vanessa de Freitas Cunha Lins

2006-01-01

77

Novel applications of atmospheric pressure plasma on textile materials  

Microsoft Academic Search

Various applications of atmospheric pressure plasma are investigated in conjunction with polymeric materials including paper, polypropylene non-woven fabric, and cotton. The effect of plasma on bulk and surface properties is examined by treating both cellulosic pulp and prefabricated paper with various plasma-gas compositions. After treatment, pulp is processed into paper and the properties are compared. The method of pulp preparation

Carrie Elizabeth Cornelius

2009-01-01

78

Fragmentation Energetics of Clusters Relevant to Atmospheric New Particle Formation  

SciTech Connect

The exact mechanisms by which small clusters form and grow in the atmosphere are poorly understood, but this process may significantly impact cloud condensation nuclei number concentrations and global climate. Sulfuric acid is the key chemical component to new particle formation, but basic species such as ammonia are also important. However, few laboratory experiments address the kinetics or thermodynamics of acid and base incorporation into small clusters. This work utilizes a Fourier transform ion cyclotron resonance mass spectrometer equipped with surface-induced dissociation (FTICR-SID) to investigate time- and collision energy-resolved fragmentation of positively charged ammonium bisulfate clusters. Critical energies for dissociation are obtained from Rice-Ramsperger-Kassel-Marcus/Quasi-Equilibrium Theory (RRKM/QET) modeling of the experimental data and are compared to quantum chemical calculations of the thermodynamics of cluster dissociation. Fragmentation of ammonium bisulfate clusters occurs by two pathways: 1) a two-step pathway whereby the cluster sequentially loses ammonia followed by sulfuric acid and 2) a one-step pathway whereby the cluster loses an ammonium bisulfate molecule. Experimental critical energies for loss of an ammonia molecule and loss of an ammonium bisulfate molecule are higher than the thermodynamic values. If cluster growth is considered the reverse of cluster fragmentation, these results require the presence of an activation barrier to describe the incorporation of ammonia into small acidic clusters and suggest that kinetically (i.e. diffusion) limited growth should not be assumed. An important corollary is that models of atmospheric NPF should be revised to consider activation barriers to individual chemical steps along the growth pathway.

Bzdek, Bryan R.; Depalma, Joseph W.; Ridge, Douglas P.; Laskin, Julia; Johnston, Murray V.

2013-02-27

79

Charged and Neutral Particle Interactions on Aerospace Materials  

Microsoft Academic Search

Various candidate aircraft and spacecraft materials were analyzed and compared in a neutron environment using the Monte Carlo N-Particle (MCNP) transport code and in Galactic Cosmic Ray (GCR) and Trapped environments using the HZETRN code. These candidate materials are being used in aerospace vehicles, have been tested in particle beams, or seemed reasonable to analyze in this manner before deciding

R. C. Jr. Singleterry; Sheila A. Thibeault; Richard Wilkins; Harold Huff

2002-01-01

80

Simulation of particle fluxes and cosmogenic nuclide production in the Earth's atmosphere  

Microsoft Academic Search

A purely physical model for the simulation of cosmic ray particle interactions with the Earth's atmosphere and subsequent production and transport of secondary particles is presented. Neutron and proton spectra as a function of the coordinate in the atmosphere were calculated using a GEANT\\/MCNP-based code system. The calculated neutron fluxes are in good agreement with experimental data based on neutron

J. Masarik; J. Beer

1999-01-01

81

A criterion for new particle formation in the sulfur-rich Atlanta atmosphere  

Microsoft Academic Search

A simple dimensionless parameter, L, is shown to determine whether or not new particle formation can occur in the atmosphere on a given day. The criterion accounts for the probability that clusters, formed by nucleation, will coagulate with preexisting particles before they grow to a detectable size. Data acquired in an intensive atmospheric measurement campaign in Atlanta, Georgia, during August

P. H. McMurry; M. Fink; H. Sakurai; M. R. Stolzenburg; R. L. Mauldin; J. Smith; F. Eisele; K. Moore; S. Sjostedt; D. Tanner; L. G. Huey; J. B. Nowak; E. Edgerton; D. Voisin

2005-01-01

82

Status and potential of atmospheric plasma processing of materials  

SciTech Connect

This paper is a review of the current status and potential of atmospheric plasma technology for materials processing. The main focus is the recent developments in the area of dielectric barrier discharges with emphasis in the functionalization of polymers, deposition of organic and inorganic coatings, and plasma processing of biomaterials. A brief overview of both the equipment being used and the physicochemical reactions occurring in the gas phase is also presented. Atmospheric plasma technology offers major industrial, economic, and environmental advantages over other conventional processing methods. At the same time there is also tremendous potential for future research and applications involving both the industrial and academic world.

Pappas, Daphne [United States Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

2011-03-15

83

Generation of nano roughness on fibrous materials by atmospheric plasma  

NASA Astrophysics Data System (ADS)

Atmospheric plasma technology finds novel applications in textile industry. It eliminates the usage of water and of hazard liquid chemicals, making production much more eco-friendly and economically convenient. Due to chemical effects of atmospheric plasma, it permits to optimize dyeing and laminating affinity of fabrics, as well as anti-microbial treatments. Other important applications such as increase of mechanical resistance of fiber sleeves and of yarns, anti-pilling properties of fabrics and anti-shrinking property of wool fabrics were studied in this work. These results could be attributed to the generation of nano roughness on fibers surface by atmospheric plasma. Nano roughness generation is extensively studied at different conditions. Alternative explanations for the important practical results on textile materials and discussed.

Kulyk, I.; Scapinello, M.; Stefan, M.

2012-12-01

84

Atmospheric giant particles (iberulites) from African desert soils and human health  

NASA Astrophysics Data System (ADS)

Earth is twice as dusty as in 19th century. The amount of soil dust in the Earth's atmosphere has doubled over the last century. The circum-Mediterranean area has one of the highest dust accretion rates in the world. The larger deserts (Sahara, Gobi, Badai Jaran, etc.) are the primary sources of mobilized desert-dust top soil that move great distances through the troposphere each year. Erosion, atmospheric transport, and dust-sized soil particles deposition to earth's surface are important process in aeolian environments. Atmospheric dust is associated to global climate change. Iberulites are giant microspherulitic particles (87.9 × 27.6 µm) rounded and reddish, generated in the atmosphere (troposphere) by coalescence of smaller particles, finally falling to the earth's surface. The name comes from the Iberian Peninsula where they were discovered. An iberulite is a co-association with axial geometry, consisting of well-defined mineral grains, together with non-crystalline compounds, structured around a coarse-grained core with a smectite rind, only one vortex and pinkish color formed in the troposphere by complex aerosol-water-gas interactions. Sedimentable dust ("dry deposition") in the city of Granada (Spain) for 17 African dust intrusion events occurring in the summer months of 2010 has been studied. In all samples were detected (SEM, stereomicroscope) iberulites. Total dust and the iberulites are composed mainly by mineral particles of different nature (XRD and SEM-EDX) and size less than 10µm (laser technique), implying dangerousness by inhalation. In the total dust the dominant mineral is dolomite [CaMg(CO3)2], abundant in the surroundings of the city; in the iberulites dominates the quartz (SiO2), which indicates Saharan origin. The iberulites and the total dust are associated with metals (ICP-MS) that have a capacity to transport electrons with a high toxic potential in the body. The concentration of Cu and Pb in total dust were 5 and 2.5 times higher than the soil background values of Granada province. In the iberulites we have detected (SEM-EDX) biological material (bacteria, diatoms, nanoplankton, etc.) which allows to emit a hypothesis about their role as vectors (atmospherical "shuttles") for alloctonous diseases. Recently has been observed the role of Saharan dust in the relationship between particulate matter and short-term daily mortality among the elderly in Madrid (Spain).

Pįrraga, Jesśs; Delgado, Gabriel; Bech, Jaume; Martķn-Garcķa, Juan Manuel; Delgado, Rafael

2013-04-01

85

Analysis of Atmospheric Particles Deposited onto Mesquite Leaves in the Central Arizona -Phoenix LTER Area  

E-print Network

the transport paths of particles from distant sources. Validating and improving air quality models. The spatialAnalysis of Atmospheric Particles Deposited onto Mesquite Leaves in the Central Arizona - Phoenix) Multivariate statistics for large data sets: Applications to individual aerosol particles. Anal. Chem., 63

Hall, Sharon J.

86

BNL-67852-AB CHARACTERIZATION OF ORGANICS IN ATMOSPHERIC PARTICLES BY SINGLE  

E-print Network

-MS utilizes a reflectron time-of-flight mass spectrometer for single particle composition analysis. The resolving power of the instrument in mass-to-charge units is 1000. The TOF- MS spectra are digitizedBNL-67852-AB CHARACTERIZATION OF ORGANICS IN ATMOSPHERIC PARTICLES BY SINGLE PARTICLE MASS

87

Effects of Sodium Chloride Particles, Ozone, UV, and Relative Humidity on Atmospheric Corrosion of Silver  

E-print Network

Effects of Sodium Chloride Particles, Ozone, UV, and Relative Humidity on Atmospheric Corrosion The corrosion of Ag contaminated with NaCl particles in gaseous environments containing humidity and ozone in the presence of ozone and UV light. Unlike bare Ag i.e., with no NaCl particles on the surface , Ag with Na

88

Use of Atmospheric Glow Discharge Plasma to Modify Spaceport Materials  

NASA Technical Reports Server (NTRS)

Numerous materials used in spaceport operations require stringent evaluation before they can be utilized. It is critical for insulative polymeric materials that any surface charge be dissipated as rapidly as possible to avoid Electrostatic Discharges (ESD) that could present a danger. All materials must pass the Kennedy Space Center (KSC) standard electrostatic test [1]; however several materials that are considered favorable for Space Shuttle and International Space Station use have failed. Moreover, to minimize contamination of Mars spacecraft, spacecraft are assembled under cleanroom conditions and specific cleaning and sterilizing procedures are required for all materials. However, surface characteristics of these materials may allow microbes to survive by protecting them from sterilization and cleaning techniques. In this study, an Atmospheric Pressure Glow Discharge Plasma (APGD) [2] was used to modify the surface of several materials. This allowed the materials surface to be modified in terms of hydrophilicity, roughness, and conductivity without affecting the bulk properties. The objectives of this study were to alter the surface properties of polymers for improved electrostatic dissipation characteristics, and to determine whether the consequent surface modification on spaceport materials enhanced or diminished microbial survival.

Trigwell, S.; Shuerger, A. C.; Buhler, C. R.; Calle, C. J.

2006-01-01

89

Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles.  

PubMed

Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations. PMID:24833386

Riccobono, Francesco; Schobesberger, Siegfried; Scott, Catherine E; Dommen, Josef; Ortega, Ismael K; Rondo, Linda; Almeida, Joćo; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; David, André; Downard, Andrew; Dunne, Eimear M; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Hansel, Armin; Junninen, Heikki; Kajos, Maija; Keskinen, Helmi; Kupc, Agnieszka; Kürten, Andreas; Kvashin, Alexander N; Laaksonen, Ari; Lehtipalo, Katrianne; Makhmutov, Vladimir; Mathot, Serge; Nieminen, Tuomo; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud P; Santos, Filipe D; Schallhart, Simon; Seinfeld, John H; Sipilä, Mikko; Spracklen, Dominick V; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Tsagkogeorgas, Georgios; Vaattovaara, Petri; Viisanen, Yrjö; Vrtala, Aron; Wagner, Paul E; Weingartner, Ernest; Wex, Heike; Wimmer, Daniela; Carslaw, Kenneth S; Curtius, Joachim; Donahue, Neil M; Kirkby, Jasper; Kulmala, Markku; Worsnop, Douglas R; Baltensperger, Urs

2014-05-16

90

Oxidation Products of Biogenic Emissions Contribute to Nucleation of Atmospheric Particles  

E-print Network

Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations.

Riccobono, Francesco; Baltensperger, Urs; Worsnop, Douglas R; Curtius, Joachim; Carslaw, Kenneth S; Wimmer, Daniela; Wex, Heike; Weingartner, Ernest; Wagner, Paul E; Vrtala, Aron; Viisanen, Yrjö; Vaattovaara, Petri; Tsagkogeorgas, Georgios; Tomé, Antonio; Stratmann, Frank; Stozhkov, Yuri; Spracklen, Dominick V; Sipilä, Mikko; Praplan, Arnaud P; Petäjä, Tuukka; Onnela, Antti; Nieminen, Tuomo; Mathot, Serge; Makhmutov, Vladimir; Lehtipalo, Katrianne; Laaksonen, Ari; Kvashin, Alexander N.; Kürten, Andreas; Kupc, Agnieszka; Keskinen, Helmi; Kajos, Maija; Junninen, Heikki; Hansel, Armin; Franchin, Alessandro; Flagan, Richard C; Ehrhart, Sebastian; Duplissy, Jonathan; Dunne, Eimear M; Downard, Andrew; David, André; Breitenlechner, Martin; Bianchi, Federico; Amorim, Antonio; Almeida, Joćo; Rondo, Linda; Ortega, Ismael K; Dommen, Josef; Scott, Catherine E; Vrtala, Aron; Santos, Filipe D; Schallhart, Simon; Seinfeld, John H; Sipila, Mikko; Donahue, Neil M; Kirkby, Jasper; Kulmala, Markku

2014-01-01

91

Process for application of powder particles to filamentary materials  

NASA Technical Reports Server (NTRS)

This invention is a process for the uniform application of polymer powder particles to a filamentary material in a continuous manner to form a uniform composite prepreg material. A tow of the filamentary material is fed under carefully controlled tension into a spreading unit, where it is spread pneumatically into an even band. The spread filamentary tow is then coated with polymer particles from a fluidized bed, after which the coated filamentary tow is fused before take-up on a package for subsequent utilization. This process produces a composite prepreg uniformly without imposing severe stress on the filamentary material, and without requiring long, high temperature residence times for the polymer.

Baucom, Robert M. (inventor); Snoha, John J. (inventor); Marchello, Joseph M. (inventor)

1991-01-01

92

Particle sizes and composition of Mars atmospheric dust based upon Viking and Mariner 9 observations  

NASA Technical Reports Server (NTRS)

Mars atmospheric dust can play an important role in the thermal structure of the Mars atmosphere during periods of high dust loading. However, the radiative properties of Mars atmospheric dust remain uncertain due to uncertain definitions of the dust composition and size distribution. The analysis by Toon et al., of Mariner 9 IRIS spectra during the 1971-1972 global dust storm indicated a reasonable match between the modeled 9-micron absorption of montmorillinite and the observed 9-micron absorption. Toon et al. also determined that an effective (cross-section weighted) mean radius of 2.5 microns (R(sub mode) = 0.4 microns) provided a consistent fit of montmorillinite to the IRIS dust spectra at 9 microns. Pollack et al. analyzed Viking lander observations of atmospheric extinction and scattering at visible-near IR wavelengths (0.5-1.0 microns), and obtained consistency with the Toon et al. dust size distribution when the effects of nonspherical particle shapes were included. An additional, minor (1 percent) component of visible-ultraviolet absorbing material was required to model the derived visible (0.86) and ultraviolet (0.4-0.6) single-scattering albedos of the dust, since montmorillinite does not absorb sufficiently in this wavelength region. A combined analysis of the Viking IRTM and Mariner 9 observations was conducted to reassess the model of Mars atmospheric ultraviolet-to-infrared measurements of dust absorption and scattering. The optical constants for palagonite are incorporated in a doubling-adding radiative transfer model of the Mars atmosphere to simulate Mariner 9 IRIS spectra as well as the Viking IRTM IR band observations. Visible and ultraviolet single-scattering albedos based on the Hansen and Travis Mie scattering code were also derived. A tentative conclusion is that smaller dust particles (R(sub mode) = 0.15 microns, cross-section weighted mean R = 1.2 microns) composed of palagonite provide a much improved fit to the Mariner 9 IRIS spectra; agreement with the observed ratio of visible-to-infrared extinction opacities; and ultraviolet and visible single-scattering albedos comparable to their observed values.

Clancy, R. T.; Lee, S. W.; Gladstone, G. R.

1993-01-01

93

Estimates of atmospheric deposition of submicron particle-associated combustion derived organic contaminants to Chesapeake Bay  

SciTech Connect

Once emitted into the atmosphere, combustion derived organic contaminants partition between gaseous and particle phases. In order to estimate the wet and dry removal of contaminants from the atmospheric to surface waters, it is necessary to measure gaseous and particle-associated contaminant concentrations because the deposition mechanisms of each phase differ. The authors estimate dry and wet depositional fluxes of polycyclic aromatic hydrocarbons (PAH) as a function of large and small particles to provide insight to the contribution of small particles to the overall atmospheric flux of organic contaminants to surface waters. Utilizing data gathered from concurrent measurements of 10 PAHs associated with particles in rain an in the atmosphere adjacent to Chesapeake Bay, and from PAH particle-size distribution data recently collected at Egbert, Ontario, calculated non-crustal PAH dry particle fluxes range from 40 to as high as 160 ng/m{sup 2}/month. Despite the lower estimated deposition velocity for noncrustal particles relative to that for partially crustal particles, non-crustal PAH particle fluxes are about a factor of five larger than those calculated for particles with a partial crustal component. Monthly wet fluxes of submicron particles range from 12 to 260 ng/m{sup 2}/month and in contrast to dry periods, are similar to those for large particles. Their calculations suggest that the atmospheric loading of submicron particle associated PAHs on an annual basis during dry and wet periods are significant due to the high concentrations of contaminants in this size range in both air and rain.

Leister, D.L. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Organic Analytical Research Division; [Univ. of Maryland, Solomons, MD (United States). Chesapeake Biological Lab.; Baker, J.E. [Univ. of Maryland, Solomons, MD (United States). Chesapeake Biological Lab.

1994-12-31

94

Chemical Bonding and Structural Information of Black CarbonReference Materials and Individual Carbonaceous AtmosphericAerosols  

SciTech Connect

The carbon-to-oxygen ratios and graphitic nature of a rangeof black carbon standard reference materials (BC SRMs), high molecularmass humic-like substances (HULIS) and atmospheric particles are examinedusing scanning transmission X-ray microscopy (STXM) coupled with nearedge X-ray absorption fine structure (NEXAFS) spectroscopy. UsingSTXM/NEXAFS, individual particles with diameter>100 nm are studied,thus the diversity of atmospheric particles collected during a variety offield missions is assessed. Applying a semi-quantitative peak fittingmethod to the NEXAFS spectra enables a comparison of BC SRMs and HULIS toparticles originating from anthropogenic combustion and biomass burns,thus allowing determination of the suitability of these materials forrepresenting atmospheric particles. Anthropogenic combustion and biomassburn particles can be distinguished from one another using both chemicalbonding and structural ordering information. While anthropogeniccombustion particles are characterized by a high proportion ofaromatic-C, the presence of benzoquinone and are highly structurallyordered, biomass burn particles exhibit lower structural ordering, asmaller proportion of aromatic-C and contain a much higher proportion ofoxygenated functional groups.

Hopkins, Rebecca J.; Tivanski, Alexei V.; Marten, Bryan D.; Gilles, Mary K.

2007-04-25

95

Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples  

Microsoft Academic Search

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 µm equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(2SO4,and such particles were enriched

Xiande Liu; Piet Van Espen; Freddy Adams; Jan Cafmeyer; Willy Maenhaut

2000-01-01

96

Erosion tests of materials by energetic particle beams  

SciTech Connect

The internal components of magnetic fusion devices must withstand erosion from and high heat flux of energetic plasma particles. The selection of materials for the construction of these components is important to minimize contamination of the plasma. In order to study various materials' comparative resistance to erosion by energetic particles and their ability to withstand high heat flux, water-cooled copper swirl tubes coated or armored with various materials were subjected to bombardment by hydrogen and helium particle beams. Materials tested were graphite, titanium carbide (TiC), chromium, nickel, copper, silver, gold, and aluminum. Details of the experimental arrangement and methods of application or attachment of the materials to the copper swirl tubes are presented. Results including survivability and mass losses are discussed.

Schechter, D.E.; Tsai, C.C.; Sluss, F.; Becraft, W.R.; Hoffman, D.J.

1985-01-01

97

Thermal conductivity measurements of particulate materials: 5. Effect of bulk density and particle shape  

NASA Astrophysics Data System (ADS)

Thermal conductivities were measured with a line-heat source for three particulate materials with different particle shapes under low pressures of a carbon dioxide atmosphere and various bulk densities. Less than 2 ?m kaolinite exhibited a general decrease in thermal conductivity with increasing bulk density. For the range of atmospheric pressures appropriate for Mars, a reduction in porosity of 24% decreased the thermal conductivity by 24%. Kaolinite manifests considerable anisotropy with respect to thermal conductivity. As the particles align the bulk thermal conductivity measured increasingly reflects the thermal conductivity of the short axis. When kyanite is crushed, it forms blady particles that will also tend to align with increasing bulk density. Without any intrinsic anisotropy, however, kyanite particles, like other particulates exhibit an increase in thermal conductivity with increasing bulk density. Under Martian atmospheric pressures, a reduction in porosity of 30% produces a 30% increase in thermal conductivity. Diatomaceous earth maintains a very low bulk density due to the highly irregular shape of the individual particles. A decrease in porosity of 17% produces an increase in thermal conductivity of 27%. The trends in thermal conductivity with bulk density, whether increasing or decreasing, are often not smooth. Whether oscillations in the trends presented in this paper and elsewhere have any physical significance or whether they are merely artifacts of the precision error is unclear. Clarification of this question may not be possible without higher-precision measurements from future laboratories and further development of theoretical modeling.

Presley, Marsha A.; Christensen, Philip R.

2010-07-01

98

Influence of starting material particle size on pellet surface roughness.  

PubMed

The purpose of this study was to investigate the effect of pelletization aids, i.e., microcrystalline cellulose (MCC) and cross-linked polyvinyl pyrrolidone (XPVP), and filler, i.e., lactose, particle size on the surface roughness of pellets. Pellets were prepared from powder blends containing pelletization aid/lactose in 1:3 ratio by extrusion-spheronization. Surface roughness of pellets was assessed quantitatively and qualitatively using optical interferometry and scanning electron microscopy, respectively. Both quantitative and qualitative surface studies showed that surface roughness of pellets depended on the particle size of XPVP and lactose used in the formulation. Increase in XPVP or lactose particle size resulted in rougher pellets. Formulations containing MCC produced pellets with smoother surfaces than those containing XPVP. Furthermore, surface roughness of the resultant pellets did not appear to depend on MCC particle size. Starting material particle size was found to be a critical factor for determining the surface roughness of pellets produced by extrusion-spheronization. Smaller particles can pack well with lower peaks and valleys, resulting in pellets with smoother surfaces. Similar surface roughness of pellets containing different MCC grades could be due to the deaggregation of MCC particles into smaller subunits with more or less similar sizes during wet processing. Hence, for starting materials that deaggregate during the wet processing, pellet surface roughness is influenced by the particle size of the material upon deaggregation. PMID:24198222

Sarkar, Srimanta; Ang, Bee Hwee; Liew, Celine Valeria

2014-02-01

99

Secondary Cosmic Ray Particles Due to GCR Interactions in the Earth's Atmosphere  

SciTech Connect

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface. Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

Battistoni, G.; /Milan U. /INFN, Milan; Cerutti, F.; /CERN; Fasso, A.; /SLAC; Ferrari, A.; /CERN; Garzelli, M.V.; /Milan U. /INFN, Milan; Lantz, M.; /Goteborg, ITP; Muraro, S. /Milan U. /INFN, Milan; Pinsky, L.S.; /Houston U.; Ranft, J.; /Siegen U.; Roesler, S.; /CERN; Sala, P.R.; /Milan U. /INFN, Milan; ,

2009-06-16

100

Secondary Cosmic Ray Particles due to GCR Interactions in the Earth's Atmosphere  

SciTech Connect

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface.Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

Battistoni, G.; Garzelli, M. V.; Muraro, S.; Sala, P. R. [University of Milano, Department of Physics, and INFN, Milan (Italy); Cerutti, F.; Ferrari, A.; Roesler, S. [CERN, Geneva (Switzerland); Fasso, A. [SLAC, Stanford, CA (United States); Lantz, M. [Chalmers University, Department of Fundamental Physics, Goteborg (Sweden); Pinsky, L. S. [University of Houston, Department of Physics, Houston, TX (United States); Ranft, J. [Siegen University, Fachbereich 7-Physik, Siegen (Germany)

2008-01-24

101

Secondary Cosmic Ray particles due to GCR interactions in the Earth's atmosphere  

E-print Network

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface. Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

G. Battistoni; F. Cerutti; A. Fassņ; A. Ferrari; M. V. Garzelli; M. Lantz; S. Muraro; L. S. Pinsky; J. Ranft; S. Roesler; P. R. Sala

2007-11-13

102

Atmospheric Environment 37 (2003) 14351449 Sampling methods used for the collection of particle-phase  

E-print Network

Atmospheric Environment 37 (2003) 1435Ā­1449 Sampling methods used for the collection of particle. In this paper detailed comparisons between filter-based carbonaceous aerosol sampling methods are made

103

Simulation on particle crushing of tailings material under high pressure  

NASA Astrophysics Data System (ADS)

With continuous increase of the high tailings dam, it has an important practical and theoretical significance to study the mechanical characteristics of the tailings material under high pressures. It is indicated that strength envelopes of the tailings material have a remarkable nonlinear characteristics through the triaxial test under high pressures. A further study stated that the particle crushing has a critical effect on the mechanical behavior of the tailings material. In order to quantitatively research its influence, the grain size distribution of the tailings material is analyzed for pre-and post-test and the particle crushing of the tailings material is measured. The particle flow code is employed to simulate and monitor the sample during testing. Firstly, a model which considers the particle crushing is built under the plane strain condition. Then, a series of biaxial numerical tests of the tailings specimen are simulated by using the model. It is found that the simulation result agrees with the triaxial test. Finally, a law between the particle crushing and strain of the tailings material under different confining pressures is obtained.

Liu, Hai-ming; Liu, Yi-ming; Yang, Chun-he; Cao, Jing

2013-06-01

104

Heterogeneous Atmospheric Aerosol Production by Acid Catalyzed Particle-Phase Reactions  

Microsoft Academic Search

According to evidence from our laboratory, acidic surfaces on atmospheric aerosols lead to potentially multifold increases in secondary organic aerosol (SOA) mass. Experimental observations using a multichannel flow reactor, Teflon (polytetrafluoroethylene) film bag batch reactors, and outdoor Teflon-film smog chambers strongly confirm that inorganic acids, such as sulfuric acid, catalyze particle-phase heterogeneous reactions of atmospheric organic carbonyl species. The net

Myoseon Jang; Nadine M. Czoschke; Sangdon Lee; Richard M. Kamens

2002-01-01

105

An alpha particle experiment for chemical analysis of the Martian surface and atmosphere.  

NASA Technical Reports Server (NTRS)

An alpha particle experiment similar to the one performed successfully on the Surveyor lunar missions is described. It is designed to provide a chemical analysis of the Martian surface and atmosphere. Analyses of rocks of known and unknown compositions have been made under simulated Martian conditions. The accuracies attained are generally comparable to those of the Surveyor lunar analyses. Improvements have been achieved in determining carbon and oxygen, so that a few per cent of water or carbonates in rocks can be detected. Some aspects of the integration of such an experiment with the spacecraft, a possible mission profile, and some other problems associated with a soft-landing mission to Mars are discussed. The importance of such a chemical analysis experiment in answering current questions about the nature and history of Martian surface material and its suitability for life processes is presented.

Economou, T. E.; Turkevich, A. L.; Patterson, J. H.

1973-01-01

106

The composition of atmospheric coarse particles at an urban and non-urban site  

NASA Astrophysics Data System (ADS)

The composition of four samples of atmospheric coarse particles (> 6 ?m diameter) was determined by morphology using an optical microscope. Two samples were from a rural site and two from an urban site in the midwestern United States. The urban samples represented a heavily industrial sector and a commercial sector of the urban area. The contributions of various sources to total mass concentration were compared. Results indicate that limestone and silicates were the main source of material at the non-urban site. Anthropogenic sources, represented by flyash and coal, were present in the industrial sector sample and rubber tire was present in the commercial sector sample. The mass median diameters (MMD) for different components were as follows: limestone (20 ?m), silicates (12 ?m), coal, flyash and iron oxide (12 ?m) and rubber tire (25 ?m).

Noll, K. E.; Draftz, R.; Fang, K. Y. P.

107

PD-FiTE - an efficient method for calculating gas / liquid equilibria in atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Assessing the impact of atmospheric aerosol particles on the environment requires adequate representation of appropriate key processes within large scale models. In the absence of primary particulate material, interactions between the atmospheric gaseous components and particles means that the chemical nature of the particles is largely determined by the availability of condensable gaseous material, such as sulphuric and nitric acids, and by the ambient environmental conditions. Gas to particle mass transfer of semi-volatile components,driven by a difference in equilibrium and actual partial pressures above an aerosol particle, is an important factor in determining the evolving chemical composition of the particle and is necessary for predicting aerosol loading and composition. The design of an appropriate framework required for parameterizations of key variables is challenging. These thermodynamic frameworks are often numerically very complex, resulting in significant computational expense. Three dimensional chemical and aerosol transport models demand that computational expense be kept at a minimum,resulting in a trade-off between accuracy and efficiency. To calculate the equilibrium vapour pressure above a solution requires treatment of solution nonideality. This is manifest through activity coefficients of components pertinent to each condensing specie. However, activity coefficients are complex functions of the solution composition. Parameterisation of activity coefficients provides the main focus of this work largely because reducing the numerical complexity whilst retaining a good level of accuracy is very challenging. The approach presented here, the hybrid Partial Derivative Fitted Taylor Expansion (PDFiTE) (Topping et al 2008), builds on previously reported work, with an aim to derive parameters for an accurate and computationally efficient framework through coupling with a complex thermodynamic model. Such a reduction in complexity is important as it is necessary to further include an as yet unspecified number of condensing organic species, thus increasing the computational burden of any existing framework. Using this coupled approach we derive optimised model parameters describing the interaction between different chemical components, resulting in a significant increase in computational performance, in some cases giving a four fold decrease in the required number of floating point operations, whilst remaining accurate. Overall, comparisons with the most accurate inorganic activity coefficient model available (Clegg et al1998) and an existing parameterisation (MTEM) (Zaveri et al 2005) indicate that the methodology behind PD-FiTE gives an increase in accuracy for calculating the vapour pressure of all condensing gases when averaged over the parameterisation space of the system H+-NH4+-Na+-SO42--HSO4--NO3--Cl-. Following this, the reduced parameterisation is coupled into a combined chemistry / microphysical aerosol model in a dynamical simulation of aerosol composition. This demonstrates the robustness of our model and also demonstrates the implications of its use. As a simple test case we investigate the response of a typical marine aerosol passing through a polluted environment. This shows the robustness of PD-FiTE and illustrates its usefulness in capturing the fine details of important phenomena such as the outgassing of HCl in response to HNO3 uptake by sea-salt particles. Further, since semi-volatile organic compounds are ubiquitous and secondary organic aerosol is thought to be a major fraction of submicron aerosol mass, the inclusion of organic compounds into the framework will be reported. References: Clegg, S. L., et al. (1992), Thermodynamics of Multicomponent, Miscible, Ionic-Solutions .2. Mixtures Including Unsymmetrical Electrolytes,Journal of Physical Chemistry, 96, 9470-9479. Topping, D.O. et al (2008). An Efficient and Accurate Scheme for the Partitioning of Atmospheric Semi-Volatile Components - 1 Inorganic Compounds. Submitted to Journal of Geophysical Research. Zaveri, R. A., et al. (2005),

Topping, D.; Lowe, D.; McFiggans, G.; Barley, M.

2009-04-01

108

[Atmospheric particle formation events in Nanjing during summer 2010].  

PubMed

Feature of aerosol particle number concentration, condition and impact factor of new particle formation (NPF) were investigated in Nanjing during summer. In this study, aerosol particle number concentration and gaseous pollutants (O3, SO2 and NO2) measurements were carried out by Wide-Range Particle Spectrometer (WPS) and Differential Optical Absorption Spectroscopy (DOAS) in July 2010. Combining with observations from Automatic Weather Station and Backward Trajectory Simulation, the condition and impact factor of NPF were discussed. Results showed that the averaged 10-500 nm particle number concentration was 1.7 x 10(4) cm(-3), similar to some typical observation values in North American and Europe; the 10-25 nm particle number concentration accounted for 25% of the total number concentration. Six NPF events occurred during observation. We analyzed that stable wind speed and direction, strong solar radiation promoted the NPF. The humidity during NPF event varied from 50% to 70%. Results indicated that clean ocean air mass brought from easterly and southerly wind promoted the NPF by Backward Trajectory Model Simulation. During the NPF event, the 10 - 25 nm particle number concentration positively correlated with the concentration of SO2, and negatively correlated with O3, whereas poorly correlated with NO2. PMID:22624358

Wang, Hong-Lei; Zhu, Bin; Shen, Li-Juan; Kang, Han-Qing; Diao, Yi-Wei

2012-03-01

109

Determining the sources of atmospheric particles in Shanghai, China, from magnetic and geochemical properties  

Microsoft Academic Search

The study describes an investigation into the sources of atmospheric particles collected at 11 sites across Shanghai, China, during one week in November 1998. Source ascription is based on mineral magnetic and geochemical properties, and a chemical mass balance (CMB) model. The CMB model shows that the main contributions to total suspended particles (TSPs) are products of coal combustion, with

Jiong Shu; John A. Dearing; Andrew P. Morse; Lizhong Yu; Nu Yuan

2001-01-01

110

Scanning Electron Microanalysis and Analytical Challenges of Mapping Elements in Urban Atmospheric Particles  

EPA Science Inventory

Elemental mapping with energy-dispersive X-ray spectroscopy (EDX) associated with scanning electron microscopy is highly useful for studying internally mixed atmospheric particles. Presented is a study of individual particles from urban airsheds and the analytical challenges in q...

111

The atmospheric cosmic- and solar energetic particle radiation environment at aircraft altitudes  

Microsoft Academic Search

Galactic cosmic rays interact with the solar wind, the earth's magnetic field and its atmosphere to produce hadron, lepton and photon fields at aircraft altitudes. In addition to cosmic rays, energetic particles generated by solar activity bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have

K. O'Brien; W. Friedberg; D. F. Smart; H. H. Sauer

1998-01-01

112

Quantitative characterization of spatial distribution of particles in materials: Application to materials processing  

NASA Technical Reports Server (NTRS)

Most engineering materials contain second phase particles or fibers which serve to reinforce the matrix phase. The effect of reinforcements on material properties is usually analyzed in terms of the average volume fraction and spacing of reinforcements, quantities which are global microstructural characteristics. However, material properties can also depend on local microstructural characteristics; for example, on how uniformly the reinforcing phase is distributed in the material. The analysis method will then be applied to a materials processing problem to discover how processing parameters can be selected to maximize redistribution of the reinforcing phase during processing. Several mathematical analysis methods could be adapted to the problem of characterizing the distribution of particles in materials. A tessellation-based method was selected. In the first phase of the investigation, a software package was written to automate the analysis. Typical results are shown. The analysis technique allows the degree to which particles are clustered together, the size and spacing of particle clusters, and the particle density in clusters to be found. The analysis methods were applied to computer-generated distributions and to a few real particle-containing materials. Methods for analyzing a nonuniform particle distribution in a material can be applied to two broad classes of materials science problems: understanding how the resulting particle distribution affects properties. The analysis method described is applied to a materials processing problem: how to select extrusion conditions to maximize the redistribution of reinforcing particles that are initially nonuniformly distributed. In addition, the tessellation-based method to analyze star distributions in spiral galaxies was adapted, illustrating the diverse types of problems to which the analysis method can be applied.

Parse, J. B.; Wert, John A.

1990-01-01

113

Investigation of the Importance of Atmospheric Dust Content on Particle Spectra on the Surface of Mars  

NASA Astrophysics Data System (ADS)

The Mars Science Laboratory mission successfully landed the Curiosity Rover inside Gale Crater on the surface of Mars on August 6, 2012. The mission's science goals are to determine the past and present habitability of Mars, to search for the building blocks of life, to investigate the surface composition and long-term surface and atmospheric processes and to analyze the Martian radiation environment. For analyzing the radiation environment, Curiosity carries the Radiation Assessment Detector. Its goals are to measure the energetic particle spectra on the surface of Mars, to determine dose and dose equivalent rate, to determine radiation hazard and mutagenic influence, to determine chemical and isotopic effects of energetic particles and to enable validation of atmospheric transmission models. In order to fully understand the influence of the highly variable Martian climate, we simulate the process of particle transportation through the Martian atmosphere. We have applied different atmospheric models available through a climate database which include a widely varying range of conditions. This enables us to study the the effect of atmospheric variables such as air density and dust content on the particle spectra at the surface of Mars. We present a comparison of particle spectra resulting from different atmospheric conditions. The results are discussed and the implications in the context of the MSL mission and possible future missions are presented.

Appel, J.; Lohf, H.; Guo, J.; Kohler, J.; Wimmer-Schweingruber, R. F.; Ehresmann, B.; Zeitlin, C. J.; Rafkin, S. C.; Matthiae, D.; Hassler, D.; Burmeister, S.; Boehm, E.; Boettcher, S.; Brinza, D.; Martin, C.; Reitz, G.

2013-12-01

114

Meteoric Material - One of the Least Explored Components of Planetary Atmospheres  

Microsoft Academic Search

Interplanetary dust particles (IDPs) continuously impact all the planets and their satellites in the solar system. In all planetary atmospheres IDPs leave their imprint as aerosols or smoke particles that are left behind when the IDPs do not ablate completely or when the ablated vapors recondense. In addition, in all atmospheres they produce ionization layers comprised of metallic ions, predominantly

J. I. Moses; J. M. Grebowsky; W. D. Pesnell; A. L. Weisman

2001-01-01

115

Studies of meteoric smoke particles in the middle and upper atmosphere using a Whole Atmosphere Community Climate Model  

NASA Astrophysics Data System (ADS)

We have developed the first global model of meteoric metals in the atmosphere by combining three components: the Whole Atmosphere Community Climate Model (WACCM), a description of the neutral and ion-molecule chemistry of six metals (Na, Fe, K, Mg, Si and Ca) based on ~200 chemical reactions, and a treatment of the injection of meteoric constituents into the atmosphere by considering the astronomical properties of the meteoric influx. This model performs reasonably well in simulating the main features of the atomic metal layers (i.e., peak densities, total column abundances, seasonal variability) in the mesosphere/lower thermosphere region compared with the currently available measurements made by satellite and lidar. The WACCM model including these six metals also simulates the neutral and ionized metal--containing species as well as individual dominant reservoir species (FeOH, Mg(OH)2, NaHCO3 and Si(OH)4) below 90 km. Therefore, the self-consistent model is able to generate meteoric smoke particles (MSPs) explicitly because these are predominantly composed of ablated Fe, Mg, Na and Si. The microphysical processes of the MSPs are calculated by the CARMA (Community Aerosol and Radiation Model for Atmosphere) module in WACCM to allow for the coagulation of aerosol/dust particles. We will present the modelled global distribution of MSPs and discuss some key dynamical and chemical processes controlling the distribution of MSPs in the middle and upper atmosphere.

FENG, W.; Plane, J. M.; Chipperfield, M.; Marsh, D. R.; Janches, D.; Bardeen, C.

2013-12-01

116

The Interior Analysis and 3-D Reconstruction of Internally-Mixed Light-Absorbing Atmospheric Particles  

Microsoft Academic Search

Carbon-containing atmospheric particles may either absorb solar or outgoing long-wave radiation or scatter solar radiation, and thus, affect Earth's radiative balance in multiple ways. Light-absorbing carbon that is common in urban air particles such as industrial coke dust, road dust, and diesel soot, often exists in the same particle with other phases that contain, for example, aluminum, calcium, iron, and

J. M. Conny; S. M. Collins; I. Anderson; A. Herzing

2010-01-01

117

Martian particle size based on thermal inertia corrected for elevation-dependent atmospheric properties  

NASA Technical Reports Server (NTRS)

Thermal inertia is commonly used to derive physical properties of the Martian surface. If the surface is composed of loosely consolidated grains, then the thermal conductivity derived from the inertia can theoretically be used to compute the particle size. However, one persistent difficulty associated with the interpretation of thermal inertia and the derivation of particle size from it has been the degree to which atmospheric properties affect both the radiation balance at the surface and the gas conductivity. These factors vary with atmospheric pressure so that derived thermal inertias and particle sizes are a function of elevation. By utilizing currently available thermal models and laboratory information, a fine component thermal inertia map was convolved with digital topography to produce particle size maps of the Martian surface corrected for these elevation-dependent effects. Such an approach is especially applicable for the highest elevations on Mars, where atmospheric back radiation and gas conductivity are low.

Bridges, N. T.

1993-01-01

118

[Characterization of ultrafine particle size distribution in the urban atmosphere of Hangzhou in spring].  

PubMed

Continuous measurement and analysis of the atmospheric ultrafine particle number concentration were performed in Hangzhou from March to May, 2012 by using the fast mobility particle sizer (FMPS). The result showed that daily number concentration of nucleation mode (5.6-20 nm), Aitken mode (20-100 nm), and accumulation mode (100-560 nm) particles, and total particles were 0.84 x 10(4), 1.08 x 10(4), 0.47 x 10(4) and 2.38 x 10(4) cm(-3) respectively. The concentration of Aitken mode particles was higher than that of other mode particles in sunny day. The nucleation mode and Aitken mode particles usually started to increase around 10:00-11:00 and ended up after 3-4 h. This indicated the solar radiation promoted the formation of new particles. Human activities caused the concentration distribution of each mode particles having an obvious difference between workdays and weekends. Combined with the meteorological factors, analysis showed that the wind speed and wind direction also directly influenced particulate concentration. The analysis of particulate concentration and visibility showed that the concentration of accumulation mode particles had a negative relationship with the atmospheric visibility, while those of nucleation mode and Aitken mode particles had a slight influence on it. PMID:24812930

Xie, Xiao-Fang; Sun, Zai; Yang, Wen-Jun

2014-02-01

119

Surface modification of polymeric materials by cold atmospheric plasma jet  

NASA Astrophysics Data System (ADS)

In this work we report the surface modification of different engineering polymers, such as, polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) by an atmospheric pressure plasma jet (APPJ). It was operated with Ar gas using 10 kV, 37 kHz, sine wave as an excitation source. The aim of this study is to determine the optimal treatment conditions and also to compare the polymer surface modification induced by plasma jet with the one obtained by another atmospheric pressure plasma source - the dielectric barrier discharge (DBD). The samples were exposed to the plasma jet effluent using a scanning procedure, which allowed achieving a uniform surface modification. The wettability assessments of all polymers reveal that the treatment leads to reduction of more than 40° in the water contact angle (WCA). Changes in surface composition and chemical bonding were analyzed by x-ray photoelectron spectroscopy (XPS) and Fourier-Transformed Infrared spectroscopy (FTIR) that both detected incorporation of oxygen-related functional groups. Surface morphology of polymer samples was investigated by Atomic Force Microscopy (AFM) and an increase of polymer roughness after the APPJ treatment was found. The plasma-treated polymers exhibited hydrophobic recovery expressed in reduction of the O-content of the surface upon rinsing with water. This process was caused by the dissolution of low molecular weight oxidized materials (LMWOMs) formed on the surface as a result of the plasma exposure.

Kostov, K. G.; Nishime, T. M. C.; Castro, A. H. R.; Toth, A.; Hein, L. R. O.

2014-09-01

120

Modelling the formation of organic particles in the atmosphere  

NASA Astrophysics Data System (ADS)

A modelling study investigating the formation of organic particles from inorganic, thermodynamically stable clusters was carried out. A recently-developed theory, the so-called nano-Köhler theory, which describes a thermodynamic equilibrium between a nanometer-size cluster, water and water-soluble organic compound, was implemented in a dynamical model along with a treatment of the appropriate aerosol and gas-phase processes. The obtained results suggest that both gaseous sulphuric acid and organic vapours contribute to organic particle formation. The initial growth of freshly-nucleated clusters having a diameter around 1 nm is driven by condensation of gaseous sulphuric acid and by a lesser extent cluster self-coagulation. After the clusters have reached sizes of around 2 nm in diameter, low-volatile organic vapours start to condense spontaneously into the clusters, thereby accelerating their growth to detectable sizes. A shortage of gaseous sulphuric acid or organic vapours limit, or suppress altogether, the particle formation, since freshly-nucleated clusters are rapidly coagulated away by pre-existing particles. The obtained modelling results were applied to explaining the observed seasonal cycle in the number of aerosol formation events in a continental forest site.

Anttila, T.; Kerminen, V.-M.; Kulmala, M.; Laaksonen, A.; O'Dowd, C.

2003-12-01

121

Atmospheric tar balls: Particles from biomass and biofuel burning  

Microsoft Academic Search

“Tar balls” are amorphous, carbonaceous spherules that occur in the tropospheric aerosol as a result of biomass and biofuel burning. They form a distinct group of particles with diameters typically between 30 and 500 nm and readily identifiable with electron microscopy. Their lack of a turbostratic microstructure distinguishes them from soot, and their morphology and composition (?90 mol % carbon)

Mihįly Pósfai; Andrįs Gelencsér; Renįta Simonics; Krisztina Arató; Jia Li; Peter V. Hobbs; Peter R. Buseck

2004-01-01

122

Numerical Investigation of Light Scattering by Atmospheric Particles  

E-print Network

with the discrete dipole approximation (DDA). The PSTD outperforms the DDA for particles with refractive indices larger than 1.4, and ones with smaller refractive indices by large sizes (e.g. size parameters larger than 60 for a refractive index of 1.2). The results...

Liu, Chao

2013-07-12

123

Strong atmospheric new particle formation in winter, urban Shanghai, China  

NASA Astrophysics Data System (ADS)

Particle size distributions in the range of 1.34-615.3 nm were recorded from 25 November 2013 to 25 January 2014 in urban Shanghai, using a combination of one nano Condensation Nucleus Counter system (nCNC), one nano-Scanning Mobility Particle Sizer (SMPS), and one long-SMPS. Measurements of sulfur dioxide by an SO2 analyzer with pulsed UV fluorescence technique allowed calculation of sulfuric acid proxy. In addition, concentrations of ammonia were recorded with a Differential Optical Absorption Spectroscopy (DOAS). During this 62-day campaign, 13 NPF events were identified with strong burst of sub-3 nm particles and subsequent fast growth of newly formed particles. The observed nucleation rate (J1.34), formation rate of 3 nm particles (J3), and condensation sink (CS) were 112.4-271.0 cm-3 s-1, 2.3-19.2 cm-3 s-1, and 0.030-0.10 s-1, respectively. Subsequent cluster/nanoparticle growth showed a clear size dependence, with average values of GR1.35~1.39 (from the bin of 1.34-1.37 nm to the bin of 1.37-1.41 nm), GR1.39~1.46 (from 1.37-1.41 to 1.41-1.52 nm), GR1.46~1.70 (from 1.41-1.52 to 1.52-1.89 nm), GR1.70~2.39 (from 1.52-1.89 to 1.89-3.0 nm), GR2.39~7 (from 1.89-3.0 to 7 nm), and GR7~20 (from 7 to 20 nm) being 1.6 ± 1.0, 1.4 ± 2.2, 7.2 ± 7.1, 9.0 ± 11.4, 10.9 ± 9.8, and 11.4 ± 9.7 nm h-1, respectively. Correlation between nucleation rate (J1.34) and sulfuric acid proxy indicates that nucleation rate J1.34 was proportional to a 0.64 power of sulfuric acid proxy. Correlation between nucleation rate (J1.34) and gas-phase ammonia suggests that ammonia was associated with NPF events. The calculated sulfuric acid proxy was sufficient to explain the subsequent growth of 1.34-3 nm particles, but insufficient for particles exceeding this size range. Qualitatively, NPF events in urban Shanghai likely occur on days with low levels of PM2.5.

Xiao, S.; Wang, M. Y.; Yao, L.; Kulmala, M.; Zhou, B.; Yang, X.; Chen, J. M.; Wang, D. F.; Fu, Q. Y.; Worsnop, D. R.; Wang, L.

2014-10-01

124

Method and apparatus for making articles from particle based materials  

DOEpatents

A method and apparatus are disclosed for the production of articles made of a particle-based material; e.g., ceramics and sintered metals. In accordance with the invention, a thermally settable slurry containing a relatively high concentration of the particles is conveyed through an elongate flow area having a desired cross-sectional configuration. The slurry is heated as it is advanced through the flow area causing the slurry to set or harden in a shape which conforms to the cross-sectional configuration of the flow area. The material discharges from the flow area as a self-supporting solid of near net final dimensions. The article may then be sintered to consolidate the particles and provide a high density product. 10 figs.

Moorhead, A.J.; Menchhofer, P.A.

1995-12-19

125

Viscoelastic material functions of noncolloidal suspensions with spherical particles  

E-print Network

siloxane , incorporated with 10%Ā­60% by volume of hollow and spherical glass beads. The material functions , Metzner 1985 , Kamal and Mutel 1985 , Khan and Prud'homme 1987 and Barnes 1989 . A significant body particles, the shear viscosity of the suspension increases with the volume fraction of the glass beads

126

Exoelectronic emission of particles of lunar surface material  

NASA Technical Reports Server (NTRS)

A secondary electron multiplier was used to study the thermostimulated exoelectronic emission of particles of lunar surface material returned by the Soviet Luna 16 automatic station. The natural exoemission from fragments of slag, glass, anorthosite, and a metallic particle was recorded in the isochronic and isothermal thermostimulation regimes. The temperature of emission onset depended on the type of regolith fragment. For the first three particles the isothermal drop in emission is described by first-order kinetic equations. For the anorthosite fragment, exoemission at constant temperature is characterized by a symmetric curve with a maximum. These data indicate the presence of active surface defects, whose nature can be due to the prehistory of the particles.

Mints, R. I.; Alimov, V. I.; Melekhin, V. P.; Milman, I. I.; Kryuk, V. I.; Kunin, L. L.; Tarasov, L. S.

1974-01-01

127

Qualitative multiplatform microanalysis of individual heterogeneous atmospheric particles from high-volume air samples.  

PubMed

High-resolution microscopic analysis of individual atmospheric particles can be difficult, because the filters upon which particles are captured are often not suitable as substrates for microscopic analysis. Described here is a multiplatform approach for microscopically assessing chemical and optical properties of individual heterogeneous urban dust particles captured on fibrous filters during high-volume air sampling. First, particles embedded in fibrous filters are transferred to polished silicon or germanium wafers with electrostatically assisted high-speed centrifugation. Particles are clustered in an array of deposit areas, which allows for easily locating the same particle with different microscopy instruments. Second, particles with light-absorbing and/or light-scattering behavior are identified for further study from bright-field and dark-field light-microscopy modes, respectively. Third, particles identified from light microscopy are compositionally mapped at high definition with field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Fourth, compositionally mapped particles are further analyzed with focused ion-beam (FIB) tomography, whereby a series of thin slices from a particle are imaged, and the resulting image stack is used to construct a three-dimensional model of the particle. Finally, particle chemistry is assessed over two distinct regions of a thin FIB slice of a particle with energy-filtered transmission electron microscopy (TEM) and electron energy-loss spectroscopy associated with scanning transmission electron microscopy (STEM). PMID:25220253

Conny, Joseph M; Collins, Sean M; Herzing, Andrew A

2014-10-01

128

Atmospheric fate and transport of fine volcanic ash: Does particle shape matter?  

NASA Astrophysics Data System (ADS)

Volcanic ash presents hazards to infrastructure, agriculture, and human and animal health. In particular, given the economic importance of intercontinental aviation, understanding how long ash is suspended in the atmosphere, and how far it is transported has taken on greater importance. Airborne ash abrades the exteriors of aircraft, enters modern jet engines and melts while coating interior engine parts causing damage and potential failure. The time fine ash stays in the atmosphere depends on its terminal velocity. Existing models of ash terminal velocities are based on smooth, quasi-spherical particles characterized by Stokes velocity. Ash particles, however, violate the various assumptions upon which Stokes flow and associated models are based. Ash particles are non-spherical and can have complex surface and internal structure. This suggests that particle shape may be one reason that models fail to accurately predict removal rates of fine particles from volcanic ash clouds. The present research seeks to better parameterize predictive models for ash particle terminal velocities, diffusivity, and dispersion in the atmospheric boundary layer. The fundamental hypothesis being tested is that particle shape irreducibly impacts the fate and transport properties of fine volcanic ash. Pilot studies, incorporating modeling and experiments, are being conducted to test this hypothesis. Specifically, a statistical model has been developed that can account for actual volcanic ash size distributions, complex ash particle geometry, and geometry variability. Experimental results are used to systematically validate and improve the model. The experiments are being conducted at the Flow Physics Facility (FPF) at UNH. Terminal velocities and dispersion properties of fine ash are characterized using still air drop experiments in an unconstrained open space using a homogenized mix of source particles. Dispersion and sedimentation dynamics are quantified using particle image velocimetry (PIV). Scanning Electron Microscopy (SEM) of ash particles collected in localized deposition areas is used to correlate the PIV results to particle shape. In addition, controlled wind tunnel experiments are used to determine particle fate and transport in a turbulent boundary layer for a mixed particle population. Collectively, these studies will provide an improved understanding of the effects of particle shape on sedimentation and dispersion, and foundational data for the predictive modeling of the fate and transport of fine ash particles suspended in the atmosphere.

White, C. M.; Allard, M. P.; Klewicki, J.; Proussevitch, A. A.; Mulukutla, G.; Genareau, K.; Sahagian, D. L.

2013-12-01

129

Gas-mediated charged particle beam processing of nanostructured materials  

NASA Astrophysics Data System (ADS)

Gas mediated processing under a charged particle (electron or ion) beam enables direct-write, high resolution surface functionalization, chemical dry etching and chemical vapor deposition of a wide range of materials including catalytic metals, optoelectronic grade semiconductors and oxides. Here we highlight three recent developments of particular interest to the optical materials and nanofabrication communities: fabrication of self-supporting, three dimensional, fluorescent diamond nanostructures, electron beam induced deposition (EBID) of high purity materials via activated chemisorption, and post-growth purification of nanocrystalline EBID-grown platinum suitable for catalysis applications.

Lobo, C. J.; Martin, A. A.; Elbadawi, C.; Bishop, J.; Aharonovich, I.; Toth, M.

2014-03-01

130

Origin of nitrocatechols and alkylated-nitrocatechols in atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Biomass burning constitutes one of the major sources of aerosol particles in most of the environments during winter. If a lot of information is available in the literature on the primary fraction of biomass burning aerosol particles, almost nothing is known regarding the formation of Secondary Organic Aerosol (SOA) from the chemical mixture emitted by this source. Recently methylated nitrocatechol have been identified in atmospheric particles collected in winter. These compounds are strongly associated with biomass burning tracers such as levoglucosan and are suspected to be of secondary origin since they can be formed through the oxidation of cresol significantly emitted by biomass burning. However, nitrocatechols are particularly difficult to analyze using classical techniques like HPLC-MS or GC-MS. In the present study, we adopt a new analytical approach. Direct analysis in real time (DART), introduced by Cody et al. (2005), allows direct analysis of gases, liquids, solids and materials on surfaces. Thus, for particles collected onto filters, the sample preparation step is simplified as much as possible, avoiding losses and reducing to the minimum the analytical procedure time. Two analytic modes can be used. In positive mode, [MH]+ ions are formed by proton transfer reaction ; whereas in negative ionization mode, [MH]-, M- and [MO2]- ions are formed. DART source enables soft ionization and produces simple mass spectra suitable for analysis of complex matrices, like organic aerosol, in only a few seconds. For this study, the DART source was coupled to a Q-ToF mass spectrometer (Synapt G2 HDMS, Waters), with a mass resolution up to 40 000. The analysis of atmospheric aerosol samples, collected in Marseille during winter 2011 (APICE project), with the DART/Q-ToF approach highlighted the abundance of nitrocatechols and alkylated nitrocatechols. Their temporal trends were also very similar to those of levoglucosan or dihydroabietic acid well known tracers of biomass burning aerosol. If their biomass burning origin's is clearly established, their secondary origin remains still not totally clear. Smog chamber experiments were then conducted in the PSI facilities to investigate the aging of biomass burning emissions. The analysis of samples collected during these experiments using the DART/Q-ToF approach, confirmed that nitrocatechols and methylated nitrocatechols originate from biomass burning processes. More importantly our results confirm that nitrocatechols and their methylated derivatives are quasi exclusively from secondary origin. Considering the abundance of biomass burning primary aerosol, and the large fraction of unexplained SOA, this result is of prime importance. Cody. R., Laramée J. Nilles J. and Durst H. : Direct Analysis in Real Time (DARTtm) Mass Spectrometry, JOEL news, 2005, 40, 1, 8-12. Kitanovski Z., Grgic I., Yasmeen F., Claeys M. and Cusak A.: Development of a liquid chromatographic method based on ultraviolet-visible and electrospray ionization mass spectrometric detection for the identification of nitrocatechols and related tracers ion biomass burning atmospheric organic aerosol, Rapid Communication in Mass Spectrometry, 2012, 26, 793-804. Iinuma Y., Boge O., Grafe R. and Herrmann H.: Methyl-nitrocatechols : Atmospheric tracer coumpounds for biomass burnig secondary organic aerosols, Environmental Science and Technology, 2010, 44, 8453-8459.

Marchand, Nicolas; Sylvestre, Alexandre; Ravier, Sylvain; Detournay, Anais; Bruns, Emily; Temime-Roussel, Brice; Slowik, Jay; El Haddad, Imad; Prevot, Andre

2013-04-01

131

HIGHWAY MOTOR VEHICLES AS SOURCES OF ATMOSPHERIC PARTICLES: PROJECTED TRENDS 1977 TO 2000  

EPA Science Inventory

Highway motor vehicle emissions contribute to the total atmospheric particulate burden. The possible health and welfare effects of these emissions depend upon their composition and concentration in the atmosphere, the exposure of man and materials, and in some instances the lengt...

132

Effect of atmospheric conditions on operation of terahertz systems for remote detection of ionizing materials  

NASA Astrophysics Data System (ADS)

This study was motivated by a new concept of remote detection of concealed radioactive materials by using a high power terahertz (THz) wave beam, which can be focused in a small spot where the wave electric field exceeds the breakdown threshold. In the presence of seed electrons in such a volume, this focusing can initiate the avalanche breakdown. Typically, an ambient density of free electrons is assumed to be at the level of one particle per cubic centimeter. So, when a breakdown-prone volume is smaller than 1 cm3, there should be significant difference between the breakdown rates in the case of presence of additional sources of ionization versus its absence. Since the flux density of gamma rays emitted by radioactive materials rapidly falls with the distance from the source, while the intensity of THz waves also decreases with the distance due to wave attenuation in the atmosphere, it is important to find an optimal location of the breakdown to be initiated for a given distance between a radioactive material and a THz antenna. This problem is analyzed in a given paper with the account for not only atmospheric attenuation of THz waves but also the air turbulence.

Nusinovich, Gregory S.; Kashyn, Dmytro G.; Tatematsu, Yoshinori; Idehara, Toshitaka

2014-01-01

133

Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere  

NASA Astrophysics Data System (ADS)

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei. Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes. Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases. However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere. It is thought that amines may enhance nucleation, but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.

Almeida, Joćo; Schobesberger, Siegfried; Kürten, Andreas; Ortega, Ismael K.; Kupiainen-Määttä, Oona; Praplan, Arnaud P.; Adamov, Alexey; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; David, André; Dommen, Josef; Donahue, Neil M.; Downard, Andrew; Dunne, Eimear; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Guida, Roberto; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Henschel, Henning; Jokinen, Tuija; Junninen, Heikki; Kajos, Maija; Kangasluoma, Juha; Keskinen, Helmi; Kupc, Agnieszka; Kurtén, Theo; Kvashin, Alexander N.; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Leppä, Johannes; Loukonen, Ville; Makhmutov, Vladimir; Mathot, Serge; McGrath, Matthew J.; Nieminen, Tuomo; Olenius, Tinja; Onnela, Antti; Petäjä, Tuukka; Riccobono, Francesco; Riipinen, Ilona; Rissanen, Matti; Rondo, Linda; Ruuskanen, Taina; Santos, Filipe D.; Sarnela, Nina; Schallhart, Simon; Schnitzhofer, Ralf; Seinfeld, John H.; Simon, Mario; Sipilä, Mikko; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Vaattovaara, Petri; Viisanen, Yrjo; Virtanen, Annele; Vrtala, Aron; Wagner, Paul E.; Weingartner, Ernest; Wex, Heike; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Yli-Juuti, Taina; Carslaw, Kenneth S.; Kulmala, Markku; Curtius, Joachim; Baltensperger, Urs; Worsnop, Douglas R.; Vehkamäki, Hanna; Kirkby, Jasper

2013-10-01

134

Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere.  

PubMed

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei. Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes. Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases. However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere. It is thought that amines may enhance nucleation, but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation. PMID:24097350

Almeida, Joćo; Schobesberger, Siegfried; Kürten, Andreas; Ortega, Ismael K; Kupiainen-Määttä, Oona; Praplan, Arnaud P; Adamov, Alexey; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; David, André; Dommen, Josef; Donahue, Neil M; Downard, Andrew; Dunne, Eimear; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Guida, Roberto; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Henschel, Henning; Jokinen, Tuija; Junninen, Heikki; Kajos, Maija; Kangasluoma, Juha; Keskinen, Helmi; Kupc, Agnieszka; Kurtén, Theo; Kvashin, Alexander N; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Leppä, Johannes; Loukonen, Ville; Makhmutov, Vladimir; Mathot, Serge; McGrath, Matthew J; Nieminen, Tuomo; Olenius, Tinja; Onnela, Antti; Petäjä, Tuukka; Riccobono, Francesco; Riipinen, Ilona; Rissanen, Matti; Rondo, Linda; Ruuskanen, Taina; Santos, Filipe D; Sarnela, Nina; Schallhart, Simon; Schnitzhofer, Ralf; Seinfeld, John H; Simon, Mario; Sipilä, Mikko; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Vaattovaara, Petri; Viisanen, Yrjo; Virtanen, Annele; Vrtala, Aron; Wagner, Paul E; Weingartner, Ernest; Wex, Heike; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Yli-Juuti, Taina; Carslaw, Kenneth S; Kulmala, Markku; Curtius, Joachim; Baltensperger, Urs; Worsnop, Douglas R; Vehkamäki, Hanna; Kirkby, Jasper

2013-10-17

135

Single particle size and fluorescence spectra from emissions of burning materials in a tube furnace to simulate burn pits  

NASA Astrophysics Data System (ADS)

A single-particle fluorescence spectrometer (SPFS) and an aerodynamic particle sizer were used to measure the fluorescence spectra and particle size distribution from the particulate emissions of 12 different burning materials in a tube furnace to simulate open-air burning of garbage. Although the particulate emissions are likely dominated by particles <1 ?m diameter, only the spectra of supermicron particles were measured here. The overall fluorescence spectral profiles exhibit either one or two broad bands peaked around 300-450 nm within the 280-650 nm spectral range, when the particles are illuminated with a 263-nm laser. Different burning materials have different profiles, some of them (cigarette, hair, uniform, paper, and plastics) show small changes during the burning process, and while others (beef, bread, carrot, Styrofoam, and wood) show big variations, which initially exhibit a single UV peak (around 310-340 nm) and a long shoulder in visible, and then gradually evolve into a bimodal spectrum with another visible peak (around 430-450 nm) having increasing intensity during the burning process. These spectral profiles could mainly derive from polycyclic aromatic hydrocarbons with the combinations of tyrosine-like, tryptophan-like, and other humic-like substances. About 68 % of these single-particle fluorescence spectra can be grouped into 10 clustered spectral templates that are derived from the spectra of millions of atmospheric aerosol particles observed in three locations; while the others, particularly these bimodal spectra, do not fall into any of the 10 templates. Therefore, the spectra from particulate emissions of burning materials can be easily discriminated from that of common atmospheric aerosol particles. The SFFS technology could be a good tool for monitoring burning pit emissions and possibly for distinguishing them from atmospheric aerosol particles.

Pan, Yong-Le; Houck, Joshua D. T.; Clark, Pamela A.; Pinnick, Ronald G.

2013-08-01

136

Observations of linear dependence between sulfate and nitrate in atmospheric particles  

NASA Astrophysics Data System (ADS)

measurements of water-soluble inorganic ionic species in ambient atmospheric particles were conducted at Shanghai, Hangzhou, and Guangzhou sampling sites in China during the period of 2009-2011. The relation between sulfate and nitrate in particulate matter (PM10 and PM2.5) was examined based on these measurements. Results showed that the mass fraction of sulfate was strongly negatively correlated with that of nitrate in atmospheric particles on most of the sampling days, especially when sulfate and nitrate made up the vast majority of the total soluble anions and cations (Na+, K+, Ca2+, and Mg2+) made a small contribution to the total water-soluble ions, revealing that the formation mechanisms of sulfate and nitrate in the atmosphere are highly correlated, and there exists a significant negative correlation trend between sulfate and nitrate mass fractions in the atmospheric particles. We found that local meteorological conditions presented opposite influences on the mass fractions of sulfate and nitrate. Further analysis indicated that the two mass fractions were modulated by the neutralizing level of atmospheric aerosols, and the negative correlation could be found in acidic atmospheric particles. Strong negative correlation was usually observed on clear days, hazy days, foggy days, and respirable particulate air pollution days, whereas poor negative correlation was often observed during cloud, rain, snow, dust storm, and suspended dust events. The results can help to better understand the formation mechanisms of atmospheric sulfate and nitrate during air pollution episodes and to better explain field results of atmospheric chemistry concerning sulfate and nitrate.

Kong, Lingdong; Yang, Yiwei; Zhang, Shuanqin; Zhao, Xi; Du, Huanhuan; Fu, Hongbo; Zhang, Shicheng; Cheng, Tiantao; Yang, Xin; Chen, Jianmin; Wu, Dui; Shen, Jiandong; Hong, Shengmao; Jiao, Li

2014-01-01

137

A diffusion model for use with directional samplers. [particle dispersion in atmosphere  

NASA Technical Reports Server (NTRS)

The paper presents a mathematical model for describing dispersion processes of airborne particles in the atmosphere. The process is described as a superposition of independent Brownian motion processes with drifts and a boundary at zero. It is assumed that the terrain is flat and of a homogeneous roughness. All sources are assumed to be point sources. The time dependencies of emission rates, wind speed, wind direction, and atmospheric conditions are taken into account.

Anbar, D.

1978-01-01

138

Electron Spectroscopy for Chemical Analysis (ESCA) study of atmospheric particles  

NASA Technical Reports Server (NTRS)

The results of analyses by ESCA (Electron Spectroscopy for Chemical Analysis) on several Nuclepore filters which were exposed during air pollution studies are presented along with correlative measurements by Neutron Activation Analysis and Scanning Electron Microscopy. Samples were exposed during air pollution studies at Norfolk, Virginia and the NASA Kennedy Space Center (KSC). It was demonstrated that with the ESCA technique it was possible to identify the chemical (bonding) state of elements contained in the atmospheric particulate matter collected on Nuclepore filters. Sulfur, nitrogen, mercury, chlorine, alkali, and alkaline earth metal species were identified in the Norfolk samples. ESCA binding energy data for aluminum indicated that three chemically different types of aluminum are present in the launch and background samples from NASA-KSC.

Dillard, J. G.; Seals, R. D.; Wightman, J. P.

1979-01-01

139

Particles, environments, and possible ecologies in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

The possible existence of indigenous Jovian organisms is investigated by characterizing the relevant physical environment of Jupiter, discussing the chromophores responsible for the observed coloration of the planet, and analyzing some permissible ecological niches of hypothetical organisms. Values of the eddy diffusion coefficent are estimated separately for the convective troposphere and the more stable mesosphere, and equilibrium condensation is studied for compounds containing Na, Cl, or both. The photoproduction of chromophores and nonequilibrium organic molecules is analyzed, and the motion of hypothetical organisms is examined along with the diffusion of metabolites and the consequent growth of organisms. Four kinds of organisms are considered: primary photosynthetic autotrophs ('sinkers'), larger autotrophs or heterotrophs that actively maintain their pressure level ('floaters'), organisms that seek out others ('hunters'), and organisms that live at almost pyrolytic depths ('scavengers'). It is concluded that ecological niches for sinkers, floaters, and hunters appear to exist in the Jovian atmosphere.

Sagan, C.; Salpeter, E. E.

1976-01-01

140

Investigation of abrasive action of atmospheric particles on the reflectance of mirrors  

SciTech Connect

The effect of atmospheric dust particles on the reflectance of solar-installation mirrors with front and rear reflection is investigated as a function of particle time, speed, dimensions, and angle of attack. It is shown that the atmospheric dust borne in the air and transported by the mountain-valley circulation winds characteristic of Central Asia present no danger to mirrors. Strong winds with driven dust (dust storms) cause damage to the surfaces of mirrors, especially those using front reflection. It is undesirable to locate solar installations in areas with frequent jet winds and loose soil (sand). 9 refs.

Zakhidov, R.A.; Ismanzhanov, A.

1980-01-01

141

Viscosity of ?-pinene secondary organic material and implications for particle growth and reactivity.  

PubMed

Particles composed of secondary organic material (SOM) are abundant in the lower troposphere. The viscosity of these particles is a fundamental property that is presently poorly quantified yet required for accurate modeling of their formation, growth, evaporation, and environmental impacts. Using two unique techniques, namely a "bead-mobility" technique and a "poke-flow" technique, in conjunction with simulations of fluid flow, the viscosity of the water-soluble component of SOM produced by ?-pinene ozonolysis is quantified for 20- to 50-?m particles at 293-295 K. The viscosity is comparable to that of honey at 90% relative humidity (RH), similar to that of peanut butter at 70% RH, and at least as viscous as bitumen at ?30% RH, implying that the studied SOM ranges from liquid to semisolid or solid across the range of atmospheric RH. These data combined with simple calculations or previous modeling studies are used to show the following: (i) the growth of SOM by the exchange of organic molecules between gas and particle may be confined to the surface region of the particles for RH ? 30%; (ii) at ?30% RH, the particle-mass concentrations of semivolatile and low-volatility organic compounds may be overpredicted by an order of magnitude if instantaneous equilibrium partitioning is assumed in the bulk of SOM particles; and (iii) the diffusivity of semireactive atmospheric oxidants such as ozone may decrease by two to five orders of magnitude for a drop in RH from 90% to 30%. These findings have possible consequences for predictions of air quality, visibility, and climate. PMID:23620520

Renbaum-Wolff, Lindsay; Grayson, James W; Bateman, Adam P; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J; Shilling, John E; Martin, Scot T; Bertram, Allan K

2013-05-14

142

Viscosity of ?-pinene secondary organic material and implications for particle growth and reactivity  

PubMed Central

Particles composed of secondary organic material (SOM) are abundant in the lower troposphere. The viscosity of these particles is a fundamental property that is presently poorly quantified yet required for accurate modeling of their formation, growth, evaporation, and environmental impacts. Using two unique techniques, namely a “bead-mobility” technique and a “poke-flow” technique, in conjunction with simulations of fluid flow, the viscosity of the water-soluble component of SOM produced by ?-pinene ozonolysis is quantified for 20- to 50-?m particles at 293–295 K. The viscosity is comparable to that of honey at 90% relative humidity (RH), similar to that of peanut butter at 70% RH, and at least as viscous as bitumen at ?30% RH, implying that the studied SOM ranges from liquid to semisolid or solid across the range of atmospheric RH. These data combined with simple calculations or previous modeling studies are used to show the following: (i) the growth of SOM by the exchange of organic molecules between gas and particle may be confined to the surface region of the particles for RH ? 30%; (ii) at ?30% RH, the particle-mass concentrations of semivolatile and low-volatility organic compounds may be overpredicted by an order of magnitude if instantaneous equilibrium partitioning is assumed in the bulk of SOM particles; and (iii) the diffusivity of semireactive atmospheric oxidants such as ozone may decrease by two to five orders of magnitude for a drop in RH from 90% to 30%. These findings have possible consequences for predictions of air quality, visibility, and climate. PMID:23620520

Renbaum-Wolff, Lindsay; Grayson, James W.; Bateman, Adam P.; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J.; Shilling, John E.; Martin, Scot T.; Bertram, Allan K.

2013-01-01

143

Effect of energetic particles on the Earth's upper atmosphere during geomagnetic polarity transitions  

NASA Astrophysics Data System (ADS)

During a geomagnetic polarity transition, the configuration and strength of the Earth's geomagnetic field can differ very much from the current state. This has consequences not only for the large-scale current systems, but also for the distribution of high-energy particle precipitation into the middle atmosphere, and therefore, for the composition of the middle atmosphere during and after large energetic particle events. Observations of the Earth's magnetic field during the last century show an increase of variability and a decrease of magnetic field strength. It has been argued that this might imply that a new polarity transition of the Earth's magnetic field is preparing to occur. This work is a multi-institutional collaboration aiming at modeling the magnetosphere during polarity transitions, the resulting energetic particle fluxes, and their effect on the middle atmospheric ozone concentration. We use MHD simulations and parametric modeling of the paleomagnetosphere to determine the geomagnetic field configuration for different transition scenarios. Particle orbits are traced and the resulting particle fluxes are used as input parameters in Monte-Carlo simulations of the mesospheric and stratospheric energy deposition and ionization. The effects on the composition of the middle atmosphere are investigated by means of a two-dimensional photochemistry and transport model. Although these models describe very different physical processes, links can be established through well-defined interfaces, and the chain of models allows us to study the global consequences of geomagnetic field reversals on system Earth.

Zieger, B.; Vogt, J.; Stadelmann, A.; Sinnhuber, M.; Kuenzi, K. F.; Kallenrode, M.-B.; Heber, B.; Glassmeier, K.-H.; Burrows, J. P.

144

The Interior Analysis and 3-D Reconstruction of Internally-Mixed Light-Absorbing Atmospheric Particles  

NASA Astrophysics Data System (ADS)

Carbon-containing atmospheric particles may either absorb solar or outgoing long-wave radiation or scatter solar radiation, and thus, affect Earth’s radiative balance in multiple ways. Light-absorbing carbon that is common in urban air particles such as industrial coke dust, road dust, and diesel soot, often exists in the same particle with other phases that contain, for example, aluminum, calcium, iron, and sulfur. While the optical properties of atmospheric particles in general depend on overall particle size and shape, the inhomogeneity of chemical phases within internally-mixed particles may also greatly affect particle optical properties. In this study, a series of microscopic approaches were used to identify individual light-absorbing coarse-mode particles and to assess their interior structure and composition. Particle samples were collected in 2004 from one of the U.S. EPA’s Los Angeles Particulate Matter Supersites, and were likely affected substantially by road dust and construction dust. First, bright-field and dark-field light microscopy and computer-controlled scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDX) were used to distinguish predominantly light-absorbing carbonaceous particles from other particle types such as mineral dust, sea salt, and brake wear. Second, high-resolution SEM-EDX elemental mapping of individual carbonaceous particles was used to select particles with additional elemental phases that exhibited spatial inhomogeneity. Third, focused ion-beam SEM (FIB-SEM) with EDX was used to slice through selected particles to expose interior surfaces and to determine the spatial distribution of element phases throughout the particles. Fourth, study of the interior phases of a particle was augmented by the transmission electron microscopy (TEM) of a thin section of the particle prepared by FIB-SEM. Here, electron energy loss spectroscopy with TEM was used to study chemical bonding in the carbonaceous phase. Finally, automated serial slicing and imaging in the FIB-SEM generated a stack of secondary electron images of the particles’ interior surfaces that allowed for the 3-D reconstruction of the particles, a process known as FIB tomography. Interior surface of light-absorbing carbonaceous particle from FIB-SEM analysis.

Conny, J. M.; Collins, S. M.; Anderson, I.; Herzing, A.

2010-12-01

145

Ionization of the Earth's Upper Atmosphere in Large Energetic Particle Events  

NASA Astrophysics Data System (ADS)

Energetic charged particles ionize the upper terrestrial atmosphere. Sofar, chemical consequences of precipitating particles have been discussed for solar protons with energies up to a few hundred MeV. We present a refined model for the interaction of energetic particles with the atmosphere based on a Monte-Carlo simulation. The model includes higher energies and other particle species, such as energetic solar electrons. Results are presented for well-known solar events, such as July 14, 2000, and are extrapolated to extremely large events, such as Carrington's white light flare in 1859, which from ice cores has been identified ass the largest impulsive NO3 event in the interval 1561 -- 1994 (McCracken et al., 2001).

Wolff, E.; Burrows, J.; Kallenrode, M.; von Koenig, M.; Kuenzi, K. F.; Quack, M.

2001-12-01

146

Characteristics of atmospheric ice nucleating particles associated with biomass burning in the US: Prescribed burns and wildfires  

NASA Astrophysics Data System (ADS)

improved understanding of atmospheric ice nucleating particles (INP), including sources and atmospheric abundance, is needed to advance our understanding of aerosol-cloud-climate interactions. This study examines diverse biomass burning events to better constrain our understanding of how fires impact populations of INP. Sampling of prescribed burns and wildfires in Colorado and Georgia, U.S.A., revealed that biomass burning leads to the release of particles that are active as condensation/immersion freezing INP at temperatures from -32 to -12°C. During prescribed burning of wiregrass, up to 64% of INP collected during smoke-impacted periods were identified as soot particles via electron microscopy analyses. Other carbonaceous types and mineral-like particles dominated INP collected during wildfires of ponderosa pine forest in Colorado. Total measured nINP and the excess nINP associated with smoke-impacted periods were higher during two wildfires compared to the prescribed burns. Interferences from non-smoke sources of INP, including long-range transported mineral dust and local contributions of soils and plant materials lofted from the wildfires themselves, presented challenges in using the observations to develop a smoke-specific nINP parameterization. Nevertheless, these field observations suggest that biomass burning may serve as an important source of INP on a regional scale, particularly during time periods that lack other robust sources of INP such as long-range transported mineral dust.

McCluskey, Christina S.; DeMott, Paul J.; Prenni, Anthony J.; Levin, Ezra J. T.; McMeeking, Gavin R.; Sullivan, Amy P.; Hill, Thomas C. J.; Nakao, Shunsuke; Carrico, Christian M.; Kreidenweis, Sonia M.

2014-09-01

147

BIOCOMPATIBLE FLUORESCENT MICROSPHERES: SAFE PARTICLES FOR MATERIAL PENETRATION STUDIES  

SciTech Connect

Biocompatible polymers with hydrolyzable chemical bonds have been used to produce safe, non-toxic fluorescent microspheres for material penetration studies. The selection of polymeric materials depends on both biocompatibility and processability, with tailored fluorescent properties depending on specific applications. Microspheres are composed of USFDA-approved biodegradable polymers and non-toxic fluorophores and are therefore suitable for tests where human exposure is possible. Micropheres were produced which contain unique fluorophores to enable discrimination from background aerosol particles. Characteristics that affect dispersion and adhesion can be modified depending on use. Several different microsphere preparation methods are possible, including the use of a vibrating orifice aerosol generator (VOAG), a Sono-Tek atomizer, an emulsion technique, and inkjet printhead. Applications for the fluorescent microspheres include challenges for biodefense system testing, calibrants for biofluorescence sensors, and particles for air dispersion model validation studies.

Farquar, G; Leif, R

2009-07-15

148

Occurrence and photostability of 3-nitrobenzanthrone associated with atmospheric particles  

NASA Astrophysics Data System (ADS)

The occurrence of the carcinogenic and extremely mutagenic compound, 3-nitrobenzanthrone, in extracts of ambient particulate matter has been investigated at a semi-rural sampling location. A total of seventeen 24-h samples and fourteen 12-h samples were analyzed for their content of 3-nitrobenzanthrone. 3-Nitrobenzanthrone was unambiguously detected in one-fourth of the samples in the lower pg m -3 range (mean=17.1±14.8 or 9.8±4.2 pg m -3 excluding one high value), but in the majority of the samples no signal due to 3-nitrobenzanthrone was observed. By comparison with the levels of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) and other air pollution components, it is suggested that 3-nitrobenzanthrone is a directly emitted primary pollutant and that it is not formed in the atmosphere to a significant degree. The photodegradation of 3-nitrobenzanthrone was studied in order to understand the low levels of this compound in ambient air. In the presence of a radical sensitizer, anthraquinone, the degradation rate of 3-nitrobenzanthrone is comparable to that of 1-nitropyrene (NP), a directly emitted nitro-PAH present in ambient air in significantly higher levels than 3-nitrobenzanthrone. The rate of direct photolysis is slightly smaller than that for 1NP. The conclusion of this study is that the dominant sources of 3-nitrobenzanthrone are unidentified combustion processes from which it is emitted in relatively small amounts. Accordingly, 3-nitrobenzanthrone should mainly be considered a health problem at locations close to these sources.

Feilberg, Anders; Ohura, Takeshi; Nielsen, Torben; Poulsen, Morten West Bach; Amagai, Takashi

149

Understanding Atmospheres Culture, materiality and the texture of the in-between  

E-print Network

1 Understanding Atmospheres Culture, materiality and the texture of the in-between Friday, March 16 The art of the stage set as a paradigm for an aesthetics of atmospheres _________________ 10.35 Coffee.05 Coffee break 15.15 Benjamin Morris: The Open University Air today, gone tomorrow? Local atmosphere

150

Hygroscopic growth of atmospheric aerosol particles based on active remote sensing and radiosounding measurements  

NASA Astrophysics Data System (ADS)

A new methodology based on combining active and passive remote sensing and simultaneous and collocated radiosounding data to study the aerosol hygroscopic growth effects on the particle optical and microphysical properties is presented. The identification of hygroscopic growth situations combines the analysis of multiespectral aerosol particle backscatter coefficient and particle linear depolarization ratio with thermodynamic profiling of the atmospheric column. We analysed the hygroscopic growth effects on aerosol properties, namely the aerosol particle backscatter coefficient and the volume concentration profiles, using data gathered at Granada EARLINET station. Two study cases, corresponding to different aerosol loads and different aerosol types, are used for illustrating the potential of this methodology. Values of the aerosol particle backscatter coefficient enhancement factors range from 2.10 ± 0.06 to 3.90 ± 0.03, being similar to those previously reported in the literature. Differences in the enhancement factor are directly linked to the composition of the atmospheric aerosol. The largest value of the aerosol particle backscatter coefficient enhancement factor corresponds to the presence of sulphate and marine particles that are more affected by hygroscopic growth. On the contrary, the lowest value of the enhancement factor corresponds to an aerosol mixture containing sulphates and slight traces of mineral dust. The Hänel parameterization is applied to these case studies, obtaining results within the range of values reported in previous studies, with values of the ? exponent of 0.56 ± 0.01 (for anthropogenic particles slightly influenced by mineral dust) and 1.07 ± 0.01 (for the situation dominated by anthropogenic particles), showing the convenience of this remote sensing approach for the study of hygroscopic effects of the atmospheric aerosol under ambient unperturbed conditions. For the first time, the retrieval of the volume concentration profiles for these cases using the Lidar Radiometer Inversion Code (LIRIC) allows us to analyse the aerosol hygroscopic growth effects on aerosol volume concentration, observing a stronger increase of the fine mode volume concentration with increasing relative humidity.

Granados-Muńoz, M. J.; Navas-Guzmįn, F.; Bravo-Aranda, J. A.; Guerrero-Rascado, J. L.; Lyamani, H.; Valenzuela, A.; Titos, G.; Fernįndez-Gįlvez, J.; Alados-Arboledas, L.

2014-10-01

151

Mathematical modeling of atmospheric fine particle-associated primary organic compound concentrations  

Microsoft Academic Search

An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources characterized included noncatalyst- and catalyst-equipped autos, diesel trucks, paved road

Wolfgang F. Rogge; Lynn M. Hildemann; Monica A. Mazurek; Glen R. Cass; Bernd R. T. Simoneit

1996-01-01

152

Mathematical modeling of atmospheric fine particle-associated primary organic compound concentrations  

Microsoft Academic Search

An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources characterized included noncatalyst- and catalyst-equipped diesel trucks, paved road dust,

Wolfgang F. Rogge; Lynn M. Hildemann; Monica A. Mazurek; Glen R. Cass; Bernd R. T. Simoneit

1996-01-01

153

A fast atmospheric turbulent parameters estimation using particle filtering. Application to LIDAR  

E-print Network

A fast atmospheric turbulent parameters estimation using particle filtering. Application to LIDAR. Doppler LIDAR, is typically used to get this kind of information because it can make fast, distant on simulated Doppler LIDAR measurements, in tree-dimensional modeling. 1. Introduction In various activities

Baehr, Christophe

154

An updated simulation of particle fluxes and cosmogenic nuclide production in the Earth's atmosphere  

E-print Network

to calculate the cosmogenic radionuclide production rate, models have to be developed that describe transport from the atmosphere into the various archives. A review of the most frequently used models extended our model, using new cosmic ray and nuclear data. Therefore, we revised particle fluxes

Wehrli, Bernhard

155

Particle Induced X-Ray Emission Analysis of Atmospheric Aerosols Collected in Upstate New York  

Microsoft Academic Search

Elemental analysis of atmospheric aerosols collected in the historic Stockade District of Schenectady, New York, was performed using particle induced X-ray emission (PIXE) spectroscopy. This is part of a systematic study in the Mohawk River Valley of upstate New York to identify the sources and understand the transport, transformation, and effects of airborne pollutants and the connection between aerosols, the

Colin Gleason; Charles Harrington; Katie Schuff; Scott Labrake; Michael Vineyard

2009-01-01

156

Morphology and Chemical composition of Atmospheric Particles over Semi-Arid region (Jaipur, Rajasthan) of India  

NASA Astrophysics Data System (ADS)

Uncertainties associated with the radiative forcing of atmospheric dust particles is highest, owing to lack of region-specific dust morphology (particle shape, size) and mineralogy (chemical composition) database, needed for modeling their optical properties (Mishra and Tripathi, 2008). To fill this gap for the Indian region, we collected atmospheric particles (with aerodynamic size <5um, PM5 and a few bulk particles; TSP) from seven sites of Jaipur and nearby locales (semi-arid region, in the vicinity of Thar Desert of Rajasthan) at varying altitude, during late winters of ca. 2012. PM5 particles were collected on Teflon filters (for bulk chemical analyses), while pure Tin substrates (~1×1 mm2) were used for investigating individual particle morphology. Using Scanning Electron Microscope equipped with Energy Dispersive X ray (SEM-EDX) facility at NPL, images of individual particles were recorded and the morphological parameters (e.g. Aspect ratio; AR, Circulatory parameter; CIR.) were retrieved following Okada et al. (2001), whereas chemical compositions of individual particles were determined by EDX and bulk samples by X ray fluorescence (XRF). The geometrical size distributions of atmospheric particles were generated for each site. Based on NIST (National Institute of Standard and Technology, USA) morphology database, the site-specific individual particle shapes reveal predominance of "Layered" (calcite and quartz rich), "Angular" structures (quartz rich) and "Flattened" particles over all the sites. Particles were found to be highly non-spherical with irregular shapes (CIR varying from 1 to 0.22 with median value ~0.76; AR varying from 1 to 5.4 with median value ~1.64). Noteworthy to mention, that unit values of AR and CIR represent spherical particles. Chemical analyses of PM5 particles revealed dominance of crustal elements e.g. Si, Al, Fe, Ca, Mg, in general. Particles over Kukas Hill (27.027° N, 75.919° E; ~800 MAGL) showed highest Fe mass fractions (~43%), i.e. a key element (in form of hematite; Fe2O3) for solar (visible) energy absorption and thus heating the atmosphere. The retrieved morphological parameters help to construct particle shape and number size distribution that are highly useful to reduce the uncertainty in radiative forcing of dust particles appreciably when combined with particle chemical composition as suggested by Kalashnikova and Sokolik (2004). References : Mishra, S. K., and S. N. Tripathi (2008), Modeling optical properties of mineral dust over the Indian Desert, J. Geophys. Res., 113, D23201, 19 PP., doi:10.1029/2008JD010048. Okada, K., J. Heintzenberg, K. Kai, and Y. Qin (2001), Shape of atmospheric mineral particles collected in three Chinese arid-regions, Geophys. Res. Lett., 28, 3123-3126 Kalashnikova OV, Sokolik IN. (2004) Modeling the radiative properties of nonspherical soil-derived mineral aerosols, J Quant Spectrosc Radiat Transfer, 87, 137-66.

Mishra, S. K.; Agnihotri, R.; Yadav, P.; Singh, S.; Tawale, J. S.; Rashmi, R.; Prasad, M.; Arya, B. C.; Mishra, N.

2012-12-01

157

Surfactant-free latex spheres for size calibration of mobility particle sizers in atmospheric aerosol applications  

NASA Astrophysics Data System (ADS)

Scanning mobility particle sizers (SMPS) are common instruments in laboratory and field aerosol studies. They are, however, complex instruments whose accuracy depends in part on reproducible size calibration. The commonly recommended calibration procedure uses polystyrene latex spheres in a solution with surfactant added to minimize coagulation of the particles. The surfactant can contribute significantly to the overall particle number size distribution and in some cases overlap the peak due to the latex spheres. We describe here the application of surfactant-free latex spheres which to the best of our knowledge have not been used in atmospheric applications before but which have significant advantages, including ease of use and cost.

Kidd, Carla; Perraud, Véronique; Finlayson-Pitts, Barbara J.

2014-01-01

158

Particle characterization at the Cape Verde atmospheric observatory during the 2007 RHaMBLe intensive  

NASA Astrophysics Data System (ADS)

The chemical characterization of filter high volume (HV) and Berner impactor (BI) samples PM during RHaMBLe (Reactive Halogens in the Marine Boundary Layer) 2007 shows that the Cape Verde aerosol particles are mainly composed of sea salt, mineral dust and associated water. Minor components are nss-salts, OC and EC. The influence from the African continent on the aerosol constitution was generally small but air masses which came from south-western Europe crossing the Canary Islands transported dust to the sampling site together with other loadings. The mean mass concentration was determined for PM10 to 17 ?g/m3 from impactor samples and to 24.2 ?g/m3 from HV filter samples. Non sea salt (nss) components of PM were found in the submicron fractions and nitrate in the coarse mode fraction. Bromide was found in all samples with much depleted concentrations in the range 1-8 ng/m3 compared to fresh sea salt aerosol indicating intense atmospheric halogen chemistry. Loss of bromide by ozone reaction during long sampling time is supposed and resulted totally in 82±12% in coarse mode impactor samples and in filter samples in 88±6% bromide deficits. A chloride deficit was determined to 8% and 1% for the coarse mode particles (3.5-10 ?m; 1.2-3.5 ?m) and to 21% for filter samples. During 14 May with high mineral dust loads also the maximum of OC (1.71?g/m3) and EC (1.25 ?g/m3) was measured. The minimum of TC (0.25 ?g/m3) was detected during the period 25 to 27 May when pure marine air masses arrived. The concentrations of carbonaceous material decrease with increasing particle size from 60% for the ultra fine particles to 2.5% in coarse mode PM. Total iron (dust vs. non-dust: 0.53 vs. 0.06 ?g m3), calcium (0.22 vs. 0.03 ?g m3) and potassium (0.33 vs. 0.02 ?g m3) were found as good indicators for dust periods because of their heavily increased concentration in the 1.2 to 3.5 ?m fraction as compared to their concentration during the non-dust periods. For the organic constituents, oxalate (78-151 ng/m3) and methanesulfonic acid (MSA, 25-100 ng/m3) are the major compounds identified. A good correlation between nss-sulphate and MSA was found for the majority of days indicating active DMS chemistry and low anthropogenic influences.

Müller, K.; Lehmann, S.; van Pinxteren, D.; Gnauk, T.; Niedermeier, N.; Wiedensohler, A.; Herrmann, H.

2010-03-01

159

Improving Atmospheric Plasma Spraying of Zirconate Thermal Barrier Coatings Based on Particle Diagnostics  

NASA Astrophysics Data System (ADS)

Lanthanum zirconate (La2Zr2O7) has been proposed as a promising material for thermal barrier coatings. During atmospheric plasma spraying (APS) of La2Zr2O7 a considerable amount of La2O3 can evaporate in the plasma flame, resulting in a non-stoichiometric coating. As indicated in the phase diagram of the La2O3-ZrO2 system, in the composition range of pyrochlore structure, the stoichiometric La2Zr2O7 has the highest melting point and other compositions are eutectic. APS experiments were performed with a TriplexPro™-200 plasma torch at different power levels to achieve different degrees of evaporation and thus stoichiometry. For comparison, some investigations on gadolinium zirconate (Gd2Zr2O7) were included, which is less prone to evaporation and formation of non-stoichiometry. Particle temperature distributions were measured by the DPV-2000 diagnostic system. In these distributions, characteristic peaks were detected at specific torch input powers indicating evaporation and solidification processes. Based on this, process parameters can be defined to provide stoichiometric coatings that show good thermal cycling performance.

Mauer, Georg; Sebold, Doris; Vaßen, Robert; Stöver, Detlev

2012-06-01

160

UV polarization lidar for remote sensing new particles formation in the atmosphere.  

PubMed

Understanding new particles formation in the free troposphere is key for air quality and climate change, but requires accurate observation tools. Here, we discuss on the optical requirements ensuring a backscattering device, such as a lidar, to remotely observe nucleation events promoted by nonspherical desert dust or volcanic ash particles. By applying the Mie theory and the T-matrix code, we numerically simulated the backscattering coefficient of spherical freshly nucleated particles and nonspherical particles. We hence showed that, to remotely observe such nucleation events with an elastic lidar device, it should operate in the UV spectral range and be polarization-resolved. Two atmospheric case studies are proposed, on nucleation events promoted by desert dust, or volcanic ash particles. This optical pathway might be useful for climate, geophysical and fundamental purposes, by providing a range-resolved remote observation of nucleation events. PMID:24922365

David, Grégory; Thomas, Benjamin; Dupart, Yoan; D'Anna, Barbara; George, Christian; Miffre, Alain; Rairoux, Patrick

2014-05-01

161

Studies on nanosecond pulsed atmospheric pressure discharge with particle-in-cell Monte Carlo collision simulation  

SciTech Connect

Nanosecond pulsed atmospheric pressure discharge becomes an active research topic because of its promising prospect of applications in many areas. To understand its dynamics, the discharge process was studied by one-dimensional implicit particle-in-cell Monte Carlo collision (PIC-MCC) simulation coupled with a particle renormalization algorithm, in which multiple electron Monte Carlo collisions per step were considered to improve the computation efficiency. In the simulation, the effects of discharge conditions such as plateau voltage, pulse rise time, and initial charged particle density were investigated. It is found that the plateau voltage in the pulse waveform is a major factor controlling the final charged particle density in the plasma bulk, and the built-up time and steady thickness of cathode sheath are proportional to the pulse rise time, whereas reversely proportional to the initial charged particle density.

Yang Chenguang; Duan Lian; Xu Yongyue; Wang Xinbing; Zuo Duluo [Wuhan National Laboratory for Optoelectronics and College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

2012-09-15

162

Atmospherically stable nanoscale zero-valent iron particles formed under controlled air contact: characteristics and reactivity.  

PubMed

Atmospherically stable NZVI (nanoscale zero-valent iron) particles were produced by modifying shell layers of Fe(H2) NZVI particles (RNIP-10DS) by using a controlled air contact method. Shell-modified NZVI particles were resistant to rapid aerial oxidation and were shown to have TCE degradation rate constants that were equivalent to 78% of those of pristine NZVI particles. Fe(H2) NZVI particles that were vigorously contacted with air (rapidly oxidized) showed a substantially compromised reactivity. Aging of shell-modified particles in water for one day resulted in a rate increase of 54%, implying that depassivation of the shell would play an important role in enhancing reactivity. Aging of shell-modified particles in air led to rate decreases by 14% and 46% in cases of one week and two months of aging, respectively. A series of instrumental analyses using transmission electron microscopy, X-ray diffractography, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure showed that the shells of modified NZVI particles primarily consisted of magnetite (Fe(3)O(4)). Analyses also implied that the new magnetite layer produced during shell modification was protective against shell passivation. Aging of shell-modified particles in water yielded another major mineral phase, goethite (alpha-FeOOH), whereas aging in air produced additional shell phases such as wustite (FeO), hematite (alpha-Fe(2)O(3)), and maghemite (gamma-Fe(2)O(3)). PMID:20136088

Kim, Hong-Seok; Ahn, Jun-Young; Hwang, Kyung-Yup; Kim, Il-Kyu; Hwang, Inseong

2010-03-01

163

The generation of diesel exhaust particle aerosols from a bulk source in an aerodynamic size range similar to atmospheric particles  

PubMed Central

The influence of diesel exhaust particles (DEP) on the lungs and heart is currently a topic of great interest in inhalation toxicology. Epidemiological data and animal studies have implicated airborne particulate matter and DEP in increased morbidity and mortality due to a number of cardiopulmonary diseases including asthma, chronic obstructive pulmonary disorder, and lung cancer. The pathogeneses of these diseases are being studied using animal models and cell culture techniques. Real-time exposures to freshly combusted diesel fuel are complex and require significant infrastructure including engine operations, dilution air, and monitoring and control of gases. A method of generating DEP aerosols from a bulk source in an aerodynamic size range similar to atmospheric DEP would be a desirable and useful alternative. Metered dose inhaler technology was adopted to generate aerosols from suspensions of DEP in the propellant hydrofluoroalkane 134a. Inertial impaction data indicated that the particle size distributions of the generated aerosols were trimodal, with count median aerodynamic diameters less than 100 nm. Scanning electron microscopy of deposited particles showed tightly aggregated particles, as would be expected from an evaporative process. Chemical analysis indicated that there were no major changes in the mass proportion of 2 specific aromatic hydrocarbons (benzo[a]pyrene and benzo[k]fluoranthene) in the particles resulting from the aerosolization process. PMID:19337412

Cooney, Daniel J; Hickey, Anthony J

2008-01-01

164

Soil-derived sulfate in atmospheric dust particles at Taklimakan desert  

NASA Astrophysics Data System (ADS)

Dust-associated sulfate is believed to be a key species which can alter the physical and chemical properties of dust particles in the atmosphere. Its occurrence in the particles has usually been considered to be the consequence of particles' aging in the air although it is present in some crustal minerals. Our observation at the north and south edge of Taklimakan desert, one of the largest dust sources in the Northern Hemisphere, during a dust episode in April 2008 revealed that sulfate in atmospheric dust samples most likely originated directly from surface soil. Its TSP, PM10 and PM2.5 content was proportional to samples' mass and comprised steadily about 4% in the differently sized samples, the ratio of elemental sulfur to iron was approximately constant 0.3, and no demonstrable influence of pollutants from fossil fuel combustion and biomass burning was detected. These results suggest that sulfate could be substantially derived from surface soil at the desert area and the lack of awareness of this origin may impede accurate results in any investigation of atmospheric sulfur chemistry associated with Taklimakan dust and its subsequent local, regional and global effects on the atmosphere.

Wu, Feng; Zhang, Daizhou; Cao, Junji; Xu, Hongmei; An, Zhisheng

2012-12-01

165

Polynuclear aromatic hydrocarbon degradation by heterogeneous reactions with N 2O 5 on atmospheric particles  

NASA Astrophysics Data System (ADS)

The degradation of particulate polynuclear aromatic hydrocarbons (PAH) on atmospheric soot particles in the presence of gas phase dinitrogen pentoxide (N 2O 5) was explored. Dilute diesel and wood soot particles containing PAH were reacted with˜10ppm of N 2O 5 in a 200 ? continuous stirred tank reactor (CSTR). To provide a stable source of particles for reaction in the CSTR, diesel or wood soot particles were injected at night into a 25 m 3 Teflon outdoor chamber. The large chamber served as a reservoir for the feed aerosol, and the aerosol could then be introduced at a constant flow rate into the CSTR. PAH-N 2O 5 heterogeneous rate constants for wood soot at 15°C ranged from2 × 10 -18to5 × 10 -18 cm 3 molecules -1 s -1. For diesel soot the rate constants at 16°C were higher and ranged from5 × 10 -18to30 × 10 -18 cm 3 molecules -1 s -1. Comparisons with other studies suggest that sunlight is the most important factor which influences PAH decay. This is followed by ozone, NO 2, N 2O 5 and nitric acid. The rate constants of nitro-PAH formation from a parent PAH and N 2O 5 were of the order of1 × 10 -19-1 × 10 -18 molecules -1s -1. The uncertainty associated with all of these rate constants is± a factor of 3. Given, however, the small magnitude of the rate constants and the low levels of N 2O 5 present in the atmosphere, we concluded that PAH heterogeneous reactions with gas phase N 2O 5 degrade particle-bound PAH or to form nitro-PAH from PAH are not very important. (Direct application of the specific rate constants derived in this study to ambient atmospheres should not be undertaken unless the ambient particle size distributions and chemical composition of the particles are similar to the ones reported in this study.)

Kamens, Richard M.; Guo, Jiazhen; Guo, Zhishi; McDow, Stephen R.

166

Processing of atmospheric particles caught in the act via STXM/NEXAFS  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols are an important focus of environmental research due to their effect on climate and human health. Among their main constituents are mineral dust and organic particles. Both types of particles directly and indirectly affect our climate through scattering and absorption of radiation and through acting as cloud condensation nuclei respectively. Organic particles are also of significant concern with respect to their health effects. Mineral dust particles in addition serve as a primary external iron source to the open ocean and the bioavailability of iron from these particles is highly dependent on the oxidation state of the metal. The environmental impact of atmospheric particles depends on their physical and chemical properties, which might change upon chemical ageing. In this study we therefore investigated the changes in chemical composition and morphology of mineral dust and organic particle proxies (Arizona test dust and shikimic acid, respectively) upon in situ exposure to ozone or nitrogen oxides in presence of humidity. This was achieved by monitoring changes at the C and O K-edges as well as the metal L-edges via scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Measurements were conducted at the PolLux beamline at Swiss Light Source. All experiments were conducted in an environmental micro reactor, designed specifically for the end station, to enable the investigation in situ. We observed oxidation of shikimic acid particles in situ during exposure to ozone at different humidities, whereby humidity was found to be a critical factor controlling the rate of the reaction. We also obtained well resolved iron distribution maps from the individual submicrometer size mineral dust particles before and after exposure to nitrogen oxides.

Steimer, S.; Lampimäki, M.; Grzinic, G.; Coz, E.; Watts, B.; Raabe, J.; Ammann, M.

2012-12-01

167

Investigation of fine atmospheric particle surfaces and lung lining fluid interactions using XPS  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy (XPS) was used to determine surface chemical composition of atmospheric particles before and after immersion in saline and bronchoalveolar lavage fluid (BALF). Atmospheric particulate matter (PM 2.5) was collected on PTFE filters from clean air, outdoor urban and smoke-filled indoor sites. Low particle loads were present from the clean air site and the particle surface consisted of carbon, Cl - and oxide species. An increase in particle load was observed for the outdoor urban site with C?(C, H) compounds dominating the particle surface. There was a significant contribution from C?(O, N) and C?O/COO-functionalities as well as oxides with traces of NO 3-, NH 4+, amide, SiC and SO 42- present. A further increase in particle load was observed for the smoke-filled indoor site. The surface consisted of 97% C?(C, H) compounds with traces of oxide, amide and SiO 2. The particle load was reduced in all cases after immersion in saline mainly due to removal of loosely bound particles, especially for carbon. Changes in surface composition of the particles were also observed with removal of Cl - from the clean air site, NO 3-, NH 4+, amide, SO 42- and SiC from the urban air site and SiO 2 from the indoor smoke site; these species were deemed to be bio-available. Similar results were obtained after immersion in BALF. However, there was evidence of interaction of constituents from BALF with particles collected from the outdoor urban and indoor smoke sites. A strong amide signal was observed on particles remaining on the filter after immersion in BALF suggesting that possibly proteins or other N-containing biomolecular species from BALF were adsorbed on the surface of these particles. The surface concentrations of amide, oxide, C?(O, N) and C?O/COO - varied between outdoor urban and indoor smoke particles after immersion in BALF. This infers that a different interaction is occurring between BALF constituents and outdoor urban and indoor smoke particles, respectively.

Kendall, Michaela; Hutton, Bernie M.; Tetley, Terry D.; Nieuwenhuijsen, Mark J.; Wigzell, Edward; Jones, Frances H.

2001-07-01

168

Development progress of the Materials Analysis and Particle Probea)  

NASA Astrophysics Data System (ADS)

The Materials Analysis and Particle Probe (MAPP) is a compact in vacuo surface science diagnostic, designed to provide in situ surface characterization of plasma facing components in a tokamak environment. MAPP has been implemented for operation on the Lithium Tokamak Experiment at Princeton Plasma Physics Laboratory (PPPL), where all control and analysis systems are currently under development for full remote operation. Control systems include vacuum management, instrument power, and translational/rotational probe drive. Analysis systems include onboard Langmuir probes and all components required for x-ray photoelectron spectroscopy, low-energy ion scattering spectroscopy, direct recoil spectroscopy, and thermal desorption spectroscopy surface analysis techniques.

Lucia, M.; Kaita, R.; Majeski, R.; Bedoya, F.; Allain, J. P.; Boyle, D. P.; Schmitt, J. C.; Onge, D. A. St.

2014-11-01

169

Measuring the spectral emissivity of thermal protection materials during atmospheric reentry simulation  

NASA Technical Reports Server (NTRS)

Hypersonic spacecraft reentering the earth's atmosphere encounter extreme heat due to atmospheric friction. Thermal Protection System (TPS) materials shield the craft from this searing heat, which can reach temperatures of 2900 F. Various thermophysical and optical properties of TPS materials are tested at the Johnson Space Center Atmospheric Reentry Materials and Structures Evaluation Facility, which has the capability to simulate critical environmental conditions associated with entry into the earth's atmosphere. Emissivity is an optical property that determines how well a material will reradiate incident heat back into the atmosphere upon reentry, thus protecting the spacecraft from the intense frictional heat. This report describes a method of measuring TPS emissivities using the SR5000 Scanning Spectroradiometer, and includes system characteristics, sample data, and operational procedures developed for arc-jet applications.

Marble, Elizabeth

1996-01-01

170

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Hazardous atmospheres and substances (see also Ā§ 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2010-07-01

171

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Hazardous atmospheres and substances (see also Ā§ 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2012-07-01

172

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Hazardous atmospheres and substances (see also Ā§ 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2011-07-01

173

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Hazardous atmospheres and substances (see also Ā§ 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2013-07-01

174

Assessment of atmospheric ultrafine carbon particle-induced human health risk based on surface area dosimetry  

NASA Astrophysics Data System (ADS)

Evidence shows a strong correlation between human mortality/morbidity and atmospheric ultrafine carbon particle (UFCP with aerodynamic diameter <18 nm). Theoretical and experimental studies have attempted to use mass concentration/dose as exposure dosimetry to construct the dose-response relationships. Yet little attention has been given to the problem of using surface area dosimetry in UFCP-related risk assessment. We introduced an integrated risk assessment framework based on surface area dosimetry to estimate the adverse health potential risk exposed to atmospheric UFCP. We used the neutrophil cells elevation effect as adverse health effect endpoint. We reanalyzed the published data of UFCP particle diameter ( dp) and associated specific surface area (SSA) to reconstruct their relationship through log-linear regression method. Our results show that smaller particle size ( dp < 51 nm) demonstrated steep slope (ln SSA = 11.0-2.03 ln dp), whereas larger particle size ( dp > 51 nm) was found close to the theoretical relationship (ln SSA = 8.65-1.20 ln dp). We applied the modeled relationships to estimate the surface area doses of human inhaled particles in specific scenarios or subgroups. Our findings show that Adult and Youth subgroups in northern Taiwan region posed the highest potential risk, indicating that the median 10% exceedance risks are 39.6 (95%CI: 36.4-42.9) fold compared to control based on neutrophil cells elevation effect. The result provides a preliminary aspect for discussing the human health adverse effect exposed to atmospheric UFCP for specific groups based on particle surface area dosimetry.

Chio, Chia-Pin; Liao, Chung-Min

175

Dynamics of Space Particles and Spacecrafts Passing by the Atmosphere of the Earth  

PubMed Central

The present research studies the motion of a particle or a spacecraft that comes from an orbit around the Sun, which can be elliptic or hyperbolic, and that makes a passage close enough to the Earth such that it crosses its atmosphere. The idea is to measure the Sun-particle two-body energy before and after this passage in order to verify its variation as a function of the periapsis distance, angle of approach, and velocity at the periapsis of the particle. The full system is formed by the Sun, the Earth, and the particle or the spacecraft. The Sun and the Earth are in circular orbits around their center of mass and the motion is planar for all the bodies involved. The equations of motion consider the restricted circular planar three-body problem with the addition of the atmospheric drag. The initial conditions of the particle or spacecraft (position and velocity) are given at the periapsis of its trajectory around the Earth. PMID:24396298

Prado, Antonio Fernando Bertachini de Almeida; Golebiewska, Justyna

2013-01-01

176

Models for close-in atmospheric dispersion, explosive releases, and particle deposition  

SciTech Connect

Relatively simple models are presented to simulate close-in atmospheric dispersion, explosive releases, and particle deposition. Close-in generally refers to distances less than 50 m downwind from the source. These models assume simple gas dispersion (no chemical reactions, neutral buoyancy) and that particles behave as a gas expect they can be removed from the plume by a simple, deposition-velocity mechanism. These models have been combined into a QuickBASIC program (INEXPLC.BAS) and its PC executable form (INEXPLC.EXE). These programs, along with sample input and output files, are available from the author.

Bloom, S.G.

1993-10-06

177

BIOCOMPATIBLE FLUORESCENT MICROSPHERES: SAFE PARTICLES FOR MATERIAL PENETRATION STUDIES  

SciTech Connect

Biocompatible polymers with hydrolyzable chemical bonds are being used to produce safe, non-toxic fluorescent microspheres for material penetration studies. The selection of polymeric materials depends on both biocompatibility and processability, with tailored fluorescent properties depending on specific applications. Microspheres are composed of USFDA-approved biodegradable polymers and non-toxic fluorophores and are therefore suitable for tests where human exposure is possible. Micropheres are being produced which contain unique fluorophores to enable discrimination from background aerosol particles. Characteristics that affect dispersion and adhesion can be modified depending on use. Several different microsphere preparation methods are possible, including the use of a vibrating orifice aerosol generator (VOAG), a Sono-Tek atomizer, an emulsion technique, and inkjet printhead. The advantages and disadvantages of each method will be presented and discussed in greater detail along with fluorescent and charge properties of the aerosols. Applications for the fluorescent microspheres include challenges for biodefense system testing, calibrants for biofluorescence sensors, and particles for air dispersion model validation studies.

farquar, G; Leif, R

2008-09-12

178

Solar wind and high energy particle effects in the middle atmosphere  

NASA Astrophysics Data System (ADS)

The solar wind variability and high energy particle effects in the neutral middle atmosphere are not much known. These factors are important in the high latitude upper mesosphere, lower thermosphere energy budget. They influence temperature, composition (minor constituents of nitric oxide, ozone), circulation (wind system) and airflow. The vertical and latitudinal structures of such effects, mechanisms of downward penetration of energy and questions of energy abundance are largely to be solved. The most important recent finding seems to be the discovery of the role of highly relativistic electrons in the middle atmosphere at L = 3 - 8 (Baker et al., 1987). The solar wind and high energy particle flux variability appear to form a part of the chain of possible Sun-weather (climate) relationships. The importance of such studies in the nineties is emphasized by their role in big international programs STEP and IGBP - Global Change.

Lastovicka, Jan

1989-09-01

179

The transmission of differing energy beta particles through various materials  

SciTech Connect

The transmission of beta particles is frequently calculated in the same fashion as that of gamma rays, where the mass attenuation coefficient is defined by the slope of the exponential function. Numerous authors have used this approximation including Evans (1955), Loevinger (1952), and Chabot et. al. (1988). Recent work by McCarthy et. al. (1995) indicated that the exponential function seemed to fit well over a particular region of the transmission curve. Upon further investigation, the author decided to verify McCarthy`s results by the use of different absorber materials and attempt to reproduce the experiments. A theoretical method will be used to estimate the transmission of the beta particles through the three absorbers, aluminum, zirconium, and iron. An alternate Monte Carlo code, the Electron Gamma Shower version 4 code (EGS4) will also be used to verify that the experiment is approximating a pencil beam of beta particles. Although these two methods offer a good cross check for the experimental data, they pose a conflict in regards to the type of beam that is to be generated. The experimental lab setup uses a collimated beam of electrons that will impinge upon the absorber, while the codes are written using a pencil beam. A minor discrepancy is expected to be observed in the experimental results and is currently under investigation by McCarthy. The results of this project supported the theory that the beta mass attenuation coefficient was accurately represented by the slope of an exponential function, but only for that particular region of the transmission curve that has a minimal absorber thickness. By fitting the data beyond 50% of the beta particle range this theory does not hold true. The theory generated by McCarthy (1995) and the EGS4 Monte Carlo code indicated that the transmission curve for a pencil beam was not accurately represented by an exponential function. The results of this experiment appeared to provide additional support to this assumption.

Quayle, D.R.

1996-04-01

180

Determination of low-z elements in atmospheric aerosols by charged-particle-induced nuclear reactions  

Microsoft Academic Search

Nuclear reactions induced by charged particles are used to determine total carbon, nitrogen, and oxygen in atmospheric aerosols. These simple activation methods are quite sensitive, nondestructive, and require only a short amount of beam time (one minute in most cases) for each sample analysis. The method for determination of nitrogen in aerosols uses a proton beam to induce the Ā¹ā“N(p,..cap

Clemenson

1979-01-01

181

Transient luminous event phenomena and energetic particles impacting the upper atmosphere: Russian space experiment programs  

Microsoft Academic Search

In Russia several space missions are now planned to study transient luminous events in the atmosphere and high-energy charged particles at satellite altitudes. The experimental goal is to investigate the origin of the high-energy electrons and gamma ray quanta for specific transient luminous events (TLEs) and their role in the ionosphere-magnetosphere system. Simultaneous measurements of electrons at the orbit of

M. I. Panasyuk; V. V. Bogomolov; G. K. Garipov; O. R. Grigoryan; Y. I. Denisov; B. A. Khrenov; P. A. Klimov; L. L. Lazutin; S. I. Svertilov; N. N. Vedenkin; I. V. Yashin; S. I. Klimov; L. M. Zeleny; V. S. Makhmutov; Y. I. Stozkov; N. S. Svirzhevsky; V. V. Klimenko; E. A. Mareev; Y. V. Shlyugaev; V. E. Korepanov; I. H. Park; H. I. Salazar; H. Rothkaehl

2010-01-01

182

Assessment of atmospheric ultrafine carbon particle-induced human health risk based on surface area dosimetry  

Microsoft Academic Search

Evidence shows a strong correlation between human mortality\\/morbidity and atmospheric ultrafine carbon particle (UFCP with aerodynamic diameter <18nm). Theoretical and experimental studies have attempted to use mass concentration\\/dose as exposure dosimetry to construct the dose-response relationships. Yet little attention has been given to the problem of using surface area dosimetry in UFCP-related risk assessment. We introduced an integrated risk assessment

Chia-Pin Chio; Chung-Min Liao

2008-01-01

183

Modelling The Influence of Large Energetic Particle Events On The Chemical Composition of The Middle and Upper Atmosphere  

NASA Astrophysics Data System (ADS)

Ionisation due to extraterrestrial charged particle precipitation leads to the formation of NOx and HOx in the stratosphere and mesosphere. Both NOx and HOx formation will alter the composition of the upper atmosphere significantly, as both are involved in katalytic ozone destruction cycles. While HOx, however, is extremely short-lived in the upper stratosphere and consequently, will affect the atmospheric composition only during particle precipitation events, NOx is believed to exist for months after big particle events, and thus could be transported down into the lower stratosphere during polar winter. Where and how far extraterrestrial charged particles can penetrate into the atmosphere however is determined by the strengths and form of the Earth geomagnetic field. We use a 2 D chemistry, transport and radiation model to investigate how large energetic particle events will affect the upper atmosphere NOx and HOx budget, and conse- quently, stratospheric and mesospheric ozone. The derivation of atmospheric ionisa- tion due to energetic particle precipitation is described in the accompanying contri- bution of Wolff et al., 'Investigating the ionization of the Earth's atmosphere at large energetic particle events'. Further model studies are carried out to investigate the in- fluence of large variations in the Earth magnetic field on the chemical composition of the atmosphere.

von Koenig, M.; Burrows, J.; Chipperfield, M.; Jackman, C.; Kallenrode, M.-B.; Kuenzi, K. F.; Quack, M.; Wolff, E.

184

Air Pollution by Particles  

Microsoft Academic Search

Many environmental scientists suspect that dry deposits are as destructive to materials and the environment as acid rain or snow. Much new information has been uncovered in the past 10 years about the sources and possible effects of atmospheric particles. Acidic particles in the atmosphere are known to reduce visibility and damage materials. Ingenious methods have now demonstrated that the

Robert W. Shaw

1987-01-01

185

Supplementary material to "Volcanism and the Atmosphere" 30 November 2012  

E-print Network

is a Magnitude 7 event like the Tambora AD 1815 #12;- 2 - eruption, which may have a return period of about 200 effects of volcanic eruptions. Eos, 83, 472]. Ten years later we can review those recommendations in light into the atmosphere during a volcanic eruption? It has long been known that volcanic SO2 introduced

Robock, Alan

186

Organic films on atmospheric aerosol particles, fog droplets, cloud droplets, raindrops, and snowflakes  

NASA Astrophysics Data System (ADS)

If surface-active organic molecules are present as surface films, the transfer of gases into the atmospheric water system could be impeded, evaporation could be slowed, and the aqueous chemical reactions could be influenced. The results of new measurements of the surface tension of aqueous solutions of common atmospheric organic compounds (beta-pinene, n-hexanol, eugenol, and anethole) are reported, and it is shown that the compounds produce films with properties similar to those of the better known surfactants. It is concluded that organic films are probably common on atmospheric aerosol particles and that they may occur under certain circumstances on fog droplets, cloud droplets, and snowflakes. If they are present, they will increase the lifetimes of aerosol particles, fog droplets, and cloud droplets, both by inhibiting water vapor evaporation and by reducing the efficiency with which these atmospheric components are scavenged. It is thought likely that the transport of gaseous molecules into and out of the aqueous solution will be impeded by factors of several hundred or more when organic films are present.

Gill, P. S.; Graedel, T. E.; Weschler, C. J.

1983-05-01

187

Atmospheric amines - Part II. Thermodynamic properties and gas/particle partitioning  

NASA Astrophysics Data System (ADS)

Amines enter the atmosphere from a wide range of sources, but relatively little is known about their atmospheric behavior, especially their role in gas/particle partitioning. In Part I of this work ( Ge et al., 2011) a total of 154 amines, 32 amino acids and urea were identified as occurring in the atmosphere, based upon a survey of the literature. In this work we compile data for the thermodynamic properties of the amines which control gas/particle partitioning (Henry's Law constant, liquid vapor pressure, acid dissociation constant, activity coefficient and solubility in water), and also estimate the solid/gas dissociation constants of their nitrate and chloride salts. Prediction methods for boiling point, liquid vapor pressure, acid dissociation constant and the solubility of the amines in water are evaluated, and used to estimate values of the equilibrium constants where experimental data are lacking. Partitioning of amines into aqueous aerosols is strongly dependent upon pH and is greatest for acidic aerosols. For several common amines the tendency to partition to the particle phase is similar to or greater than that of ammonia. Our results are presented as tables of values of thermodynamic equilibrium constants, which are also incorporated into the Extended Aerosol Inorganics Model ( E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) to enable gas/aerosol partitioning and other calculations to be carried out.

Ge, Xinlei; Wexler, Anthony S.; Clegg, Simon L.

2011-01-01

188

Evidence for propagation of aerobic bacteria in particles suspended in gaseous atmospheres. [Terrestrial microorganism contamination of Jupiter atmosphere  

NASA Technical Reports Server (NTRS)

One factor involved in the possibility that airborne microbes might contaminate the Jovian atmosphere is whether microbes have the capacity to propagate in air. Prior to these studies, the evidence was that the airborne state was lethal to microbes. An aerosol of aerobic bacteria was mixed with another containing C-14-glucose, and the presence of C-14-CO2 was subsequently detected, which indicates that the airborne cells were metabolically active. In the same type of experiment, it was shown that thymidine was incorporated into the acid-insoluble fraction of samples, indicating the formation of DNA. It was also shown, both by an increase in the numbers of viable cells and a parallel increase in particle numbers, that at least two new generations of cells could occur. Evidence for propagation of anaerobic bacteria has so far been negative.

Dimmick, R. L.; Chatigny, M. A.; Wolochow, H.; Straat, P.

1977-01-01

189

Viscosity of ?-pinene secondary organic material and implications for particle growth and reactivity  

SciTech Connect

Particles composed of secondary organic material (SOM) are abundant in the lower troposphere and play important roles in climate, air quality, and health. The viscosity of these particles is a fundamental property that is presently poorly quantified for conditions relevant to the lower troposphere. Using two new techniques, namely a bead-mobility technique and a poke-flow technique, in conjunction with simulations of fluid flow, we measure the viscosity of the watersoluble component of SOM produced by ?-pinene ozonolysis. The viscosity is comparable to that of honey at 90% relative humidity (RH), comparable to that of peanut butter at 70% RH and greater than or comparable to that of bitumen for ? 30% RH, implying that the studied SOM ranges from liquid to semisolid/solid at ambient relative humidities. With the Stokes-Einstein relation, the measured viscosities further imply that the growth and evaporation of SOM by the exchange of organic molecules between the gas and condensed phases may be confined to the surface region when RH ? 30%, suggesting the importance of an adsorption-type mechanism for partitioning in this regime. By comparison, for RH ? 70% partitioning of organic molecules may effectively occur by an absorption mechanism throughout the bulk of the particle. Finally, the net uptake rates of semi-reactive atmospheric oxidants such as O3 are expected to decrease by two to five orders of magnitude for a change in RH from 90% to ? 30% RH, with possible implications for the rates of chemical aging of SOM particles in the atmosphere.

Renbaum-Wolff, Lindsay; Grayson, James W.; Bateman, Adam P.; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J.; Shilling, John E.; Martin, Scot T.; Bertram, Allan K.

2013-05-14

190

Distribution of encapsulated materials in colloidal particles and its impact on oxidative stability of encapsulated materials.  

PubMed

The oxidative stability of encapsulated product is a critical parameter in many products from food to pharmaceutical to cosmetic industries. The overall objective of this study was to correlate differences in the distribution pattern of encapsulated material within solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) with the relative susceptibility of these materials to undergo oxidation. The distribution of an encapsulated lipid soluble dye (Nile Red) in SLNs and NLCs was quantitatively measured using fluorescence imaging. The relative susceptibility of the encapsulated material to react with free radicals generated in the aqueous phase and oxygen from the ambient environment was measured using peroxyl radical and oxygen sensitive fluorescent dyes encapsulated in the lipid phase of colloidal particles respectively. Imaging measurements demonstrate a significant exclusion of the encapsulated dye molecules from the lipid core of SLNs as compared to NLCs. Imaging results also showed significant differences in the intraparticle distribution of encapsulated dye between NLCs containing 1 and 10% liquid lipid. On the basis of these differences in distribution, we hypothesized that the relative susceptibility of encapsulated material to peroxyl radicals and oxygen would be in the order SLNs > 1% NLC > 10% NLC. Measurement of relative susceptibility of peroxyl radical sensitive dye encapsulated in SLNs and NLCs to peroxyl radicals generated in the aqueous phase validated the proposed hypotheses. However, the susceptibility of encapsulated oxygen sensitive dye to ambient oxygen was not significantly different between SLNs and NLCs. The results of this study demonstrate that difference in distribution pattern of encapsulated material within colloidal particles can significantly influence the susceptibility of encapsulated material to react with free radicals. Overall, this study demonstrates a comprehensive approach to characterize the susceptibility of encapsulated materials in colloidal particles to oxidation processes. PMID:22616688

Tikekar, Rohan V; Nitin, N

2012-06-26

191

49 CFR 195.581 - Which pipelines must I protect against atmospheric corrosion and what coating material may I use?  

Code of Federal Regulations, 2011 CFR

...must I protect against atmospheric corrosion and what coating material may I...HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.581 Which pipelines...must I protect against atmospheric corrosion and what coating material may...

2011-10-01

192

49 CFR 195.581 - Which pipelines must I protect against atmospheric corrosion and what coating material may I use?  

Code of Federal Regulations, 2010 CFR

...must I protect against atmospheric corrosion and what coating material may I...HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.581 Which pipelines...must I protect against atmospheric corrosion and what coating material may...

2010-10-01

193

49 CFR 195.581 - Which pipelines must I protect against atmospheric corrosion and what coating material may I use?  

Code of Federal Regulations, 2012 CFR

...must I protect against atmospheric corrosion and what coating material may I...HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.581 Which pipelines...must I protect against atmospheric corrosion and what coating material may...

2012-10-01

194

49 CFR 195.581 - Which pipelines must I protect against atmospheric corrosion and what coating material may I use?  

Code of Federal Regulations, 2013 CFR

...must I protect against atmospheric corrosion and what coating material may I...HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.581 Which pipelines...must I protect against atmospheric corrosion and what coating material may...

2013-10-01

195

Probing new physics with long-lived charged particles produced by atmospheric and astrophysical neutrinos  

NASA Astrophysics Data System (ADS)

As suggested by some extensions of the standard model of particle physics, dark matter may be a super-weakly-interacting lightest stable particle, while the next-to-lightest particle (NLP) is charged and metastable. One could test such a possibility with neutrino telescopes, by detecting the charged NLPs produced in high-energy neutrino collisions with Earth matter. We study the production of charged NLPs by both atmospheric and astrophysical neutrinos; only the latter, which is largely uncertain and has not been detected yet, was the focus of previous studies. We compute the resulting fluxes of the charged NLPs, compare those of different origins and analyze the dependence on the underlying particle physics set-up. We point out that, even if the astrophysical neutrino flux is very small, atmospheric neutrinos, especially those from the prompt decay of charmed mesons, may provide a detectable flux of NLP pairs at neutrino telescopes such as IceCube. We also comment on the flux of charged NLPs expected from proton-nucleon collisions and show that, for theoretically motivated and phenomenologically viable models, it is typically subdominant and below detectable rates.

Ando, Shin'ichiro; Beacom, John F.; Profumo, Stefano; Rainwater, David

2008-04-01

196

Chemical Imaging Analysis of Environmental Particles Using the Focused Ion Beam/Scanning Electron Microscopy Technique: Microanalysis Insights into Atmospheric Chemistry of Fly Ash  

SciTech Connect

Airborne fly ash from coal combustion may represent a source of bioavailable iron (Fe) in the open ocean. However, few studies have been made focusing on Fe speciation and distribution in coal fly ash. In this study, chemical imaging of fly ash has been performed using a dual-beam FIB/SEM (focused ion beam/scanning electron microscope) system for a better understanding of how simulated atmospheric processing modify the morphology, chemical compositions and element distributions of individual particles. A novel approach has been applied for cross-sectioning of fly ash specimen with a FIB in order to explore element distribution within the interior of individual particles. Our results indicate that simulated atmospheric processing causes disintegration of aluminosilicate glass, a dominant material in fly ash particles. Aluminosilicate-phase Fe in the inner core of fly ash particles is more easily mobilized compared with oxide-phase Fe present as surface aggregates on fly ash spheres. Fe release behavior depends strongly on Fe speciation in aerosol particles. The approach for preparation of cross-sectioned specimen described here opens new opportunities for particle microanalysis, particular with respect to inorganic refractive materials like fly ash and mineral dust.

Chen, Haihan; Grassian, Vicki H.; Saraf, Laxmikant V.; Laskin, Alexander

2013-01-21

197

Gas/particle partitioning of PCDD/F compounds in the atmosphere of Istanbul.  

PubMed

Gas/particle partitioning of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) compounds in the ambient atmosphere were investigated at three different sites (urban-industrial, urban and sub-urban) in ?stanbul. Average gas and particle phase concentrations were measured as 133fgm(-3) and 1605fgm(-3), respectively. Gas phase concentrations of polychlorinated dibenzo-p-dioxin/furan (PCDD/F) compounds were determined to be 128fgm(-3), 50fgm(-3), 153fgm(-3) during summer season and 204fgm(-3), 164fgm(-3), 154fgm(-3) during winter season for the respective three sampling sites. Particle phase concentrations were determined to be 287fgm(-3), 176fgm(-3), 160fgm(-3) during summer and 6586fgm(-3), 2570fgm(-3) and 1861fgm(-3) during winter season for those three sampling sites. Chlorination level and molecular weight of congeners affected gas/particle partitioning of PCDD/F compounds. Gas phase percentages of 2,3,7,8-TCDD and OCDD concentrations were determined to be 47% and 1% respectively. A relatively high correlation was found between total particle matter (TPM) and particle phase PCDD/F concentration during winter season. PMID:25290170

Saral, Arslan; Gunes, Gulten; Karadeniz, Aykut; Goncaloglu, Bulent Ilhan

2015-01-01

198

Influence of radioactivity on surface charging and aggregation kinetics of particles in the atmosphere.  

PubMed

Radioactivity can influence surface interactions, but its effects on particle aggregation kinetics have not been included in transport modeling of radioactive particles. In this research, experimental and theoretical studies have been performed to investigate the influence of radioactivity on surface charging and aggregation kinetics of radioactive particles in the atmosphere. Radioactivity-induced charging mechanisms have been investigated at the microscopic level, and heterogeneous surface potential caused by radioactivity is reported. The radioactivity-induced surface charging is highly influenced by several parameters, such as rate and type of radioactive decay. A population balance model, including interparticle forces, has been employed to study the effects of radioactivity on particle aggregation kinetics in air. It has been found that radioactivity can hinder aggregation of particles because of similar surface charging caused by the decay process. Experimental and theoretical studies provide useful insights into the understanding of transport characteristics of radioactive particles emitted from severe nuclear events, such as the recent accident of Fukushima or deliberate explosions of radiological devices. PMID:24308778

Kim, Yong-Ha; Yiacoumi, Sotira; Lee, Ida; McFarlane, Joanna; Tsouris, Costas

2014-01-01

199

Evidences for New Particle Formation in the Arctic as a Part of TOPSE Atmospheric Nucleation Event  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of ultrafine particles and precursor gases show evidences of new particle formation over a wide range of latitude in the free tropospheric Arctic region. However, the exact mechanism of new particle formation is uncertain. In this study, in-situ measurements taken during deployment 3 (Flight 16, March 7, 2000, Churchill-Churchill, 13:25-18:33 GMT) as a part of Tropospheric Ozone Production about Spring Equinox (TOPSE) experiment, over Western Canada were used for comparison with the model predictions. Using a combination of satellite derived brightness temperature, air parcel backward trajectory information, in-situ measurements of aerosol and precursor gases and aerosol microphysical model [Tripathi et al., 2004] driven by parameterized ion induced nucleation [Modgil et al., 2005], we have investigated the plausible mechanism responsible for, and factors leading to, new particle formation in the middle to upper troposphere during TOPSE atmospheric nucleation event. The reasonable agreement between model predicted and observed ultrafine particles of diameter 3 to 4 nm and 3 to 8 nm suggest that new particle formation is likely to occur by ion induced nucleation mechanism during TOPSE nucleation event. A significant finding is that the lowering of pre-existing particle surface, in the region of cloud outflow, triggered particle nucleation in this region. These studies indicate that, at typical middle to upper tropospheric conditions of Arctic, ion mechanism is an important source of ultrafine particles and these freshly particles can grow to act as cloud condensation nuclei (CCN), which have implications for cloud radiative properties. References Modgil, M. S., Sanjeev Kumar, S. N. Tripathi, and E. R. Lovejoy, A parameterization of ion-induced nucleation of sulfuric acid and water for atmospheric conditions, J. Geophys. Res., In press, 2005. Tripathi, S. N., X. P. Vancassel, R. G. Grainger, and H. L. Rogers, A Fast Stratospheric Aerosol Microphysical Model (SAMM): H2SO4-H2O Aerosol Development and Validation, AOPP Memorandum 2004.1, Department of Physics, University of Oxford, 2004. http://www.atm.ox.ac.uk/main/research/technical.html

Tripathi, S. N.; Kanawade, V. P.

2005-12-01

200

Venus Atmospheric Maneuverable Platform (VAMP) — Stowage/Deployment Concepts and Materials Investigation  

NASA Astrophysics Data System (ADS)

This presentation discusses the continued development of the Northrop Grumman/L'GARDE team's long-lived, maneuverable platform to explore the Venus upper atmosphere. It focuses on vehicle stowage and deployment concepts, and materials investigation.

Bolisay, L. B.; Barnes, N. C.; Sokol, D. H.; Lee, G. J.; Polidan, R. S.

2014-06-01

201

Atmospherically relevant experiments on new particle formation in the CERN CLOUD chamber (Invited)  

NASA Astrophysics Data System (ADS)

It is generally agreed that sulfuric acid is a major player in atmospheric new particle formation, however, the concentrations of sulfuric acid in the boundary layer of the ambient atmosphere are not sufficient for pure binary nucleation together with water. Therefore, other ingredients are needed to explain the observed new particle formation rates. A two-fold approach is required here: on the one hand field studies providing evidence for such additional components are to be performed, and on the other hand, laboratory experiments need to investigate the effects of such additional components. The latter has for a long time been hampered by our inability to provide a sufficiently clean environment for such experiments. With the CLOUD chamber at CERN, a number of such experiments have been performed, giving insight into the role of such additional components. Ammonia was shown to enhance the nucleation rates by several orders of magnitude compared to pure binary nucleation, however, was still insufficient to match the observed nucleation rates in the boundary layer (Kirkby et al., 2011). This paper will report on the results of experiments using dimethylamine, or oxidation products of either pinanediol or alpha-pinene as additional components. The experiments were performed in the presence or absence of ions from galactic cosmic rays, as well as with an enhanced ion concentration achieved with a pion bean provided by the CERN Proton Synchrotron. The formation of charged and neutral clusters as well as of new particles was followed by a wide variety of instruments, providing insight into the mechanism of new particle formation. Reference: Kirkby, J., et al., Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation, Nature 476, 429-433 (2011).

Baltensperger, U.; Almeida, J.; Riccobono, F.; Schobesberger, S.; Kirkby, J.

2013-12-01

202

Modelling Contribution of Biogenic VOCs to New Particle Formation in the Jülich Plant Atmosphere Chamber  

NASA Astrophysics Data System (ADS)

Biogenic VOCs are substantially emitted from vegetation to atmosphere. The oxidation of BVOCs by OH, O3, and NO3 in air generating less volatile compounds may lead to the formation and growth of secondary organic aerosol, and thus presents a link to the vegetation, aerosol, and climate interaction system (Kulmala et al, 2004). Studies including field observations, laboratory experiments and modelling have improved our understanding on the connection between BVOCs and new particle formation mechanism in some extent (see e.g. Tunved et al., 2006; Mentel et al., 2009). Nevertheless, the exact formation process still remains uncertain, especially from the perspective of BVOC contributions. The purpose of this work is using the MALTE aerosol dynamics and air chemistry box model to investigate aerosol formation from reactions of direct tree emitted VOCs in the presence of ozone, UV light and artificial solar light in an atmospheric simulation chamber. This model employs up to date air chemical reactions, especially the VOC chemistry, which may potentially allow us to estimate the contribution of BVOCs to secondary aerosol formation, and further to quantify the influence of terpenes to the formation rate of new particles. Experiments were conducted in the plant chamber facility at Forschungszentrum Jülich, Germany (Jülich Plant Aerosol Atmosphere Chamber, JPAC). The detail regarding to the chamber facility has been written elsewhere (Mentel et al., 2009). During the experiments, sulphuric acid was measured by CIMS. VOC mixing ratios were measured by two GC-MS systems and PTR-MS. An Airmodus Particle size magnifier coupled with a TSI CPC and a PH-CPC were used to count the total particle number concentrations with a detection limit close to the expected size of formation of fresh nanoCN. A SMPS measured the particle size distribution. Several other parameters including ozone, CO2, NO, Temperature, RH, and flow rates were also measured. MALTE is a modular model to predict new aerosol formation in the lower troposphere, developed by Boy, et al. (2006). We first evaluate the modelled results with measurements, and further we investigate the influence of different order of magnitude of terpene mixing ratios, especially isoprene and monoterpenes to the most important parameter of new particles formation, i.e. the formation rate (J1). Also, the influence of varying organic source rates on the sulphuric acid concentration available for particle formation is discussed. M. Boy et al., (2006). Atmos. Chem. Phys., 6, 4499-4517. M. Kulmala et al., (2004). Atmos. Chem. Phys., 4, 557-562. P. Tunved et al., (2006). Science, 14, 261-263. Th. F. Mentel et al., (2009). Atmos. Chem. Phys., 9, 4387-4406.

Liao, L.; Boy, M.; Mogensen, D.; Mentel, T. F.; Kleist, E.; Kiendler-Scharr, A.; Tillman, R.; Kulmala, M. T.; Dal Maso, M.

2012-12-01

203

Nanostructured Materials Synthesis Using Hypersonic Plasma Particle Deposition  

NASA Astrophysics Data System (ADS)

We (Work performed with P. H. McMurry, J. V. R. Heberlein, N. Rao and H. J. Lee) report a new deposition process in which ultrafine particles nucleate in a thermal plasma undergoing a supersonic expansion and are deposited on a substrate by hypersonic impaction. The objective of this process is to produce nanostructured material at high rates without having to collect and process a loose powder. Preliminary experiments in which silicon was synthesized by injecting vapor-phase silicon tetrachloride into an argon-hydrogen plasma produced in 20 minutes a deposit measuring approximately 1.3 mm thick and 5 mm in diameter, for a linear growth rate of about 1 um/s. In these experiments the plasma was generated by a DC torch operating at 200 A and 40 V. Flow rates were: argon, 35 slm; hydrogen, 4 slm; and SiCl_4, 0.2 slm. In previous experiments with similar operating conditions footnote N Rao, B. Micheel, D. Hansen, C. Fandrey, M. Bench, S. Girshick, J. Heberlein and P. McMurry, J. Mater. Res. 10, 2973 (1995); N. Rao, S. Girshick, J. Heberlein, P. McMurry, S. Jones, D. Hansen and B. Micheel, Plasma Chem. Plasma Process. 15, 581 (1995), the expansion of this mixture through a converging nozzle produced a silicon aerosol with a number-mean particle diameter of about 10 nm. In the present experiments the boron nitride nozzle was lengthened from 5 mm to 10 mm. The pressure was 66 kPa (500 torr) upstream of the nozzle and 0.3 kPa (2.5 torr) in the deposition chamber, driving a hypersonic flow which is capable of depositing particles down to about 3 nm in diameter by inertial impaction. The particle deposition process was recorded by a telemicroscope video camera, and deposits were characterized by scanning electron microscopy, x-ray diffraction, atomic force microscopy, and energy-dispersive x-ray analysis. The grain size of the deposit is expected to depend on substrate temperature, an effect which we are presently studying.

Girshick, Steven L.

1996-10-01

204

Regional modeling of the atmospheric fate and transport of benzene and diesel particles.  

PubMed

The Community Multiscale Air Quality model (CMAQ) was modified to simulate the atmospheric fate and transport of benzene and diesel particles. We simulated the July 11-15, 1995 period over a domain covering the eastern United States with a 12-km horizontal resolution and a finer (4 km) resolution over a part of the northeastern United States that includes Washington, DC and New York City. The meteorological fields were obtained from a simulation conducted earlier with the mesoscale model MM5. Gridded emission files for benzene and diesel particles were developed using the SMOKE modeling system. The results of the model simulations showed that benzene concentrations were commensurate with available measurements. Over the 4-km resolution domain, a comparison between simulated and measured 24-h average concentrations showed a fractional error of 0.46, a fractional bias of 0.14, and a coefficient of determination (r2) of 0.25. A comparison between simulated benzene hourly concentrations in New York City and in the Brigantine Wilderness Area, NJ, showed that urban concentrations were greater than the remote area concentrations by a factor of 2-5. The results of the diesel particle simulations showed spatial and temporal patterns that were similar to those obtained for benzene. However, because of the lesser contribution of on-road mobile sources to diesel particle emissions compared to benzene emissions, diesel particle concentrations showed stronger gradients between urban areas and remote areas. A comparison between diesel particle concentrations in New York City and in the Brigantine Wilderness Area, NJ, showed that the urban concentrations were greater than the remote area concentrations by a factor of 2-10. Assuming that diesel particles consist of 50% "elemental" carbon (EC), the simulated EC concentrations were in close agreement (within 10%) with the measured concentration in the urban area (Washington, DC) but were significantly lower than the measured EC concentrations in the remote area (Brigantine Wilderness Area). This result suggests that other sources beside diesel fuel engines contribute to atmospheric EC concentrations and that EC may not be a good surrogate for diesel particles. A comparison of both benzene and diesel particle simulated concentrations between an urban area (New York City) and a remote area (Brigantine Wilderness Area) shows that, at a spatial resolution of 4 km, the regional background may contribute from 10 to 20% to the peak concentrations. These results suggest that the regional background may not be negligible and should be taken into account in urban air toxics studies. PMID:14655713

Seigneur, Christian; Pun, Betty; Lohman, Kristen; Wu, Shiang-Yuh

2003-11-15

205

Carbonaceous particles in the atmosphere and precipitation of the Nam Co region, central Tibet.  

PubMed

A continuous air and precipitation sampling for carbonaceous particles was conducted in a field observatory beside Nam Co, Central Tibetan Plateau during July of 2006 through January of 2007. Organic carbon (OC) was the dominant composition of the carbonaceous particles both in the atmosphere (1660 ng/m3) and precipitation (476 ng/g) in this area, while the average elemental carbon (BC) concentrations in the atmosphere and precipitation were only 82 ng/m3 and 8 ng/g, respectively. Very high OC/BC ratio suggested local secondary organic carbon could be a dominant contribution to OC over the Nam Co region, while BC could be mainly originated from Southern Asia, as indicated by trajectory analysis and aerosol optical depth. Comparison between the BC concentrations measured in Lhasa, those at "Nepal Climate Observatory at Pyramid (NCO-P)" site on the southern slope of the Himalayas, and Nam Co suggested BC in the Nam Co region reflected a background with weak anthropogenic disturbances and the emissions from Lhasa might have little impact on the atmospheric environment here, while the pollutants from the Indo-Gangetic Basin of Southern Asia could be transported to the Nam Co region by both the summer monsoon and the westerly. PMID:21235163

Ming, Jing; Xiao, Cunde; Sun, Junying; Kang, Shichang; Bonasoni, Paolo

2010-01-01

206

Thermal conductivity measurements of particulate materials: 4. Effect of bulk density for granular particles  

Microsoft Academic Search

Thermal conductivities were measured with a line-heat source for three granular particulates of different particle sizes under low pressures of a carbon dioxide atmosphere and various bulk densities. A 25–30 ?m size fraction of crushed quartz exhibited a small, linear increase in thermal conductivity with increasing bulk density. For the range of atmospheric pressures appropriate for Mars, doubling the bulk

Marsha A. Presley; Philip R. Christensen

2010-01-01

207

Asian dust particles converted into aqueous droplets under remote marine atmospheric conditions  

PubMed Central

The chemical history of dust particles in the atmosphere is crucial for assessing their impact on both the Earth’s climate and ecosystem. So far, a number of studies have shown that, in the vicinity of strong anthropogenic emission sources, Ca-rich dust particles can be converted into aqueous droplets mainly by the reaction with gaseous HNO3 to form Ca(NO3)2. Here we show that other similar processes have the potential to be activated under typical remote marine atmospheric conditions. Based on field measurements at several sites in East Asia and thermodynamic predictions, we examined the possibility for the formation of two highly soluble calcium salts, Ca(NO3)2 and CaCl2, which can deliquesce at low relative humidity. According to the results, the conversion of insoluble CaCO3 to Ca(NO3)2 tends to be dominated over urban and industrialized areas of the Asian continent, where the concentrations of HNO3 exceed those of HCl ([HNO3/HCl] >  ? 1). In this regime, CaCl2 is hardly detected from dust particles. However, the generation of CaCl2 becomes detectable around the Japan Islands, where the concentrations of HCl are much higher than those of HNO3 ([HNO3/HCl] <  ? 0.3). We suggest that elevated concentrations of HCl in the remote marine boundary layer are sufficient to modify Ca-rich particles in dust storms and can play a more important role in forming a deliquescent layer on the particle surfaces as they are transported toward remote ocean regions. PMID:20921372

Tobo, Yutaka; Zhang, Daizhou; Matsuki, Atsushi; Iwasaka, Yasunobu

2010-01-01

208

Measurements of the mass absorption cross section of atmospheric soot particles using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Soot particles are a major absorber of shortwave radiation in the atmosphere. The mass absorption cross section is an essential quantity to describe this light absorption process. This work presents new experimental data on the mass absorption cross section of soot particles in the troposphere over Central Europe. Mass absorption cross sections were derived as the ratio between the light absorption coefficient determined by multiangle absorption photometry (MAAP) and the soot mass concentration determined by Raman spectroscopy. The Raman method is sensitive to graphitic structures present in the particle samples and was calibrated in the laboratory using Printex®90 model particles. Mass absorption cross sections were determined for a number of seven observation sites, ranging between 3.9 and 7.4 m2 g-1depending on measurement site and observational period. The highest values were found in a continentally aged air mass in winter, where soot particles were assumed to be mainly internally mixed. Our values are in the lower range of previously reported values, possibly due to instrumental differences to the former photometer and mass measurements. Overall, a value of 5.3m2 g-1from orthogonal regression over all samples is considered to be representative for the soot mass absorption cross section in the troposphere over Central Europe.

Nordmann, S.; Birmili, W.; Weinhold, K.; Müller, K.; Spindler, G.; Wiedensohler, A.

2013-11-01

209

Scattering particles in nightside limb observations of Venus’ upper atmosphere by Venus Express VIRTIS  

NASA Astrophysics Data System (ADS)

Nightside infrared limb spectra of the Venus upper atmosphere, obtained by Venus Express VIRTIS, show strong scattering of thermal radiation. This scattering of upward-going radiation into the line-of-sight is dominant below 82.5 km even at a wavelength of 5 ?m, which is indicative of relatively large particles. We show that 1 ?m-sized sulfuric acid particles (also known as mode 2 particles) provide a good fit to the VIRTIS limb data at high altitudes. We retrieve vertical profiles of the mode 2 number density between 75 and 90 km at two latitude ranges: 20-30°N and 47-50°N. Between 20 and 30°N, scattering by mode 2 particles is the main source of radiance for altitudes between 80 and 85 km. Above altitudes of 85 km smaller particles can also be used to fit the spectra. Between 47 and 50°N mode 2 number densities are generally lower than between 20 and 30°N and the profiles show more variability. This is consistent with the 47-50° latitude region being at the boundary between the low latitudes and high latitudes, with the latter showing lower cloud tops and higher ultraviolet brightness (Titov, D.V., Taylor, F.W., Svedhem, H., Ignatiev, N.I., Markiewicz, W.J., Piccioni, G., Drossart, P. [2008]. Nature 456, 620-623).

de Kok, R.; Irwin, P. G. J.; Tsang, C. C. C.; Piccioni, G.; Drossart, P.

2011-01-01

210

Characterization of Complex Organic Compounds Formed in Simulated Planetary Atmospheres by the Action of High Energy Particles  

NASA Astrophysics Data System (ADS)

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase

Kobayashi, Kensei; Kaneko, Takeo; Saito, Takeshi

1999-01-01

211

Atmospheric heterogeneous reaction of acetone: Adsorption and desorption kinetics and mechanisms on SiO 2 particles  

Microsoft Academic Search

Acetone plays an important role in photooxidation processes in the atmosphere. Up to date, little is known regarding the heterogeneous\\u000a fate of acetone. In this study, the adsorption and desorption processes of acetone on SiO2 particles, which are the major constituent of mineral dust in the atmosphere, have been investigated for the first time under\\u000a the simulated atmospheric conditions, using

ChongYu Jie; ZhongMing Chen; HongLi Wang; Wei Hua; CaiXia Wang; Shuang Li

2008-01-01

212

Quantitative determination of low-Z elements in single atmospheric particles on boron substrates by automated scanning electron microscopy-energy-dispersive X-ray spectrometry.  

PubMed

Atmospheric aerosols consist of a complex heterogeneous mixture of particles. Single-particle analysis techniques are known to provide unique information on the size-resolved chemical composition of aerosols. A scanning electron microscope (SEM) combined with a thin-window energy-dispersive X-ray (EDX) detector enables the morphological and elemental analysis of single particles down to 0.1 microm with a detection limit of 1-10 wt %, low-Z elements included. To obtain data statistically representative of the air masses sampled, a computer-controlled procedure can be implemented in order to run hundreds of single-particle analyses (typically 1000-2000) automatically in a relatively short period of time (generally 4-8 h, depending on the setup and on the particle loading). However, automated particle analysis by SEM-EDX raises two practical challenges: the accuracy of the particle recognition and the reliability of the quantitative analysis, especially for micrometer-sized particles with low atomic number contents. Since low-Z analysis is hampered by the use of traditional polycarbonate membranes, an alternate choice of substrate is a prerequisite. In this work, boron is being studied as a promising material for particle microanalysis. As EDX is generally said to probe a volume of approximately 1 microm3, geometry effects arise from the finite size of microparticles. These particle geometry effects must be corrected by means of a robust concentration calculation procedure. Conventional quantitative methods developed for bulk samples generate elemental concentrations considerably in error when applied to microparticles. A new methodology for particle microanalysis, combining the use of boron as the substrate material and a reverse Monte Carlo quantitative program, was tested on standard particles ranging from 0.25 to 10 microm. We demonstrate that the quantitative determination of low-Z elements in microparticles is achievable and that highly accurate results can be obtained using the automatic data processing described here compared to conventional methods. PMID:16131082

Choėl, Marie; Deboudt, Karine; Osįn, Jįnos; Flament, Pascal; Van Grieken, René

2005-09-01

213

The Effect of Particle Size on Iron Solubility in Atmospheric Aerosols  

NASA Astrophysics Data System (ADS)

The long range transport of mineral dust aerosols, which contain approximately 3% iron by mass, results in an estimated 14-16 Tg of iron deposited into the oceans annually; however, only a small percentage of the deposited iron is soluble. In high-nutrient, low chlorophyll ocean regions iron solubility may limit phytoplankton primary productivity. Although the atmospheric transport processes of mineral dust aerosols have been well studied, the role of particle size has been given little attention. In this work, the effect of particle size on iron solubility in atmospheric aerosols is examined. Iron-containing minerals (illite, kaolinite, magnetite, goethite, red hematite, black hematite, and quartz) were separated into five size fractions (10-2.5, 2.5-1, 1-0.5, 0.5-0.25, and <0.25?m) and extracted into buffer solutions simulating environments in the transport of aerosol particles for 150 minutes. Particle size was confirmed by scanning electron microscopy (SEM). Soluble iron content of the extracted mineral solutions was determined by inductively coupled plasma-mass spectrometry (ICP-MS). Extracted mineral solutions were also analyzed for Fe(II) and Fe(III) content using a ferrozine/UV-VIS method. Preliminary results show that differences in solution composition are more important than differences in size. When extracted into acetate and cloudwater buffers (pH 4.25-4.3), < 0.3% of the Fe in iron oxides (hematite, magnetite, and goethite) is transferred to solution as compared to ~0.1-35% for clays (kaolinite and illite). When extracted into a marine aerosol solution (pH 1.7), the percentage of Fe of the iron oxides and clays transferred to solution increases to approximately 0.5-3% and 5-70%, respectively. However, there is a trend of increased %Fe in the minerals transferred to solution in the largest and smallest size fractions (~0.01-0.3% and ~0.5-35% for iron oxides and clays, respectively), and decreased %Fe in the minerals transferred to solution in the mid-range size fraction (~0.01-0.08% and ~0.1-1% for iron oxides and clays, respectively) when extracted into the acetate and cloudwater buffers. When extracted into the marine aerosol solution the %Fe in the minerals transferred to solution increases with decreasing particle size (from ~0.7% to ~2% and ~10 to 70% in iron oxides and clays, respectively). By examining the role of particle size, this work will provide a more complete understanding of iron dissolution during atmospheric transport of mineral dust aerosols.

Marcotte, A. R.; Majestic, B. J.; Anbar, A. D.; Herckes, P.

2012-12-01

214

Students 'Weigh' Atmospheric Pollution.  

ERIC Educational Resources Information Center

Describes a procedure developed by students that measures the mass concentration of particles in a polluted urban atmosphere. Uses a portable fan and filters of various materials. Compares students' data with official data. (DDR)

Caporaloni, Marina

1998-01-01

215

The link between atmospheric radicals and newly formed particles at a spruce forest site in Germany  

NASA Astrophysics Data System (ADS)

It has been claimed for more than a century that atmospheric new particle formation is primarily influenced by the presence of sulphuric acid. However, the activation process of sulphuric acid related clusters into detectable particles is still an unresolved topic. In this study we focus on the PARADE campaign measurements conducted during August/September 2011 at Mt. Kleiner Feldberg in central Germany. During this campaign a set of radicals, organic and inorganic compounds and oxidants and aerosol properties were measured or calculated. We compared a range of organic and inorganic nucleation theories, evaluating their ability to simulate measured particle formation rates at 3 nm in diameter (J3) for a variety of different conditions. Nucleation mechanisms involving only sulphuric acid tentatively captured the observed noon-time daily maximum in J3, but displayed an increasing difference to J3 measurements during the rest of the diurnal cycle. Including large organic radicals, i.e. organic peroxy radicals (RO2) deriving from monoterpenes and their oxidation products in the nucleation mechanism improved the correlation between observed and simulated J3. This supports a recently proposed empirical relationship for new particle formation that has been used in global models. However, the best match between theory and measurements for the site of interest was found for an activation process based on large organic peroxy radicals and stabilized Criegee intermediates (sCI). This novel laboratory derived algorithm simulated the daily pattern and intensity of J3 observed in the ambient data. In this algorithm organic derived radicals are involved in activation and growth and link the formation rate of smallest aerosol particles with OH during daytime and NO3 during nighttime. Because of the RO2s lifetime is controlled by HO2 and NO we conclude that peroxy radicals and NO seem to play an important role for ambient radical chemistry not only with respect to oxidation capacity but also for the activation process of new particle formation. This is supposed to have significant impact of atmospheric radical species on aerosol chemistry and should to be taken into account when studying the impact of new particles in climate feedback cycles.

Bonn, B.; Bourtsoukidis, E.; Sun, T. S.; Bingemer, H.; Rondo, L.; Javed, U.; Li, J.; Axinte, R.; Li, X.; Brauers, T.; Sonderfeld, H.; Koppmann, R.; Sogachev, A.; Jacobi, S.; Spracklen, D. V.

2013-10-01

216

The link between atmospheric radicals and newly formed particles at a spruce forest site in Germany  

NASA Astrophysics Data System (ADS)

It has been claimed for more than a century that atmospheric new particle formation is primarily influenced by the presence of sulfuric acid. However, the activation process of sulfuric acid related clusters into detectable particles is still an unresolved topic. In this study we focus on the PARADE campaign measurements conducted during August/September 2011 at Mt Kleiner Feldberg in central Germany. During this campaign a set of radicals, organic and inorganic compounds and oxidants and aerosol properties were measured or calculated. We compared a range of organic and inorganic nucleation theories, evaluating their ability to simulate measured particle formation rates at 3 nm in diameter (J3) for a variety of different conditions. Nucleation mechanisms involving only sulfuric acid tentatively captured the observed noon-time daily maximum in J3, but displayed an increasing difference to J3 measurements during the rest of the diurnal cycle. Including large organic radicals, i.e. organic peroxy radicals (RO2) deriving from monoterpenes and their oxidation products, in the nucleation mechanism improved the correlation between observed and simulated J3. This supports a recently proposed empirical relationship for new particle formation that has been used in global models. However, the best match between theory and measurements for the site of interest was found for an activation process based on large organic peroxy radicals and stabilised Criegee intermediates (sCI). This novel laboratory-derived algorithm simulated the daily pattern and intensity of J3 observed in the ambient data. In this algorithm organic derived radicals are involved in activation and growth and link the formation rate of smallest aerosol particles with OH during daytime and NO3 during night-time. Because the RO2 lifetime is controlled by HO2 and NO we conclude that peroxy radicals and NO seem to play an important role for ambient radical chemistry not only with respect to oxidation capacity but also for the activation process of new particle formation. This is supposed to have significant impact of atmospheric radical species on aerosol chemistry and should be taken into account when studying the impact of new particles in climate feedback cycles.

Bonn, B.; Bourtsoukidis, E.; Sun, T. S.; Bingemer, H.; Rondo, L.; Javed, U.; Li, J.; Axinte, R.; Li, X.; Brauers, T.; Sonderfeld, H.; Koppmann, R.; Sogachev, A.; Jacobi, S.; Spracklen, D. V.

2014-10-01

217

Exploiting an atmospheric model for automated invariant material identification in hyperspectral imagery  

Microsoft Academic Search

The measured spectral radiance signature for a material can vary significantly due to atmospheric conditions and scene geometry. We show using a statistical analysis of a comprehensive physical model that the variation in a material's spectral signature lies in a low-dimensional space. The spectral radiance model includes reflected solar and sky radiation as well as path radiance. Signature variability is

David Slater; Glenn Healey

1998-01-01

218

Influence of atmospheric pressure plasma treatment on various fibrous materials: Performance properties and surface adhesion analysis  

Microsoft Academic Search

Atmospheric pressure plasma treatment using oxygen gas was applied to wool fibrous materials. The plasma-treated fibrous materials were characterised using advanced instrumental techniques including scanning electron microscopy and X-ray photoelectron spectroscopy. They were also tested for performance properties including tensile and tearing strength as well as change in yellowness using international standard testing methods. Wettability analysis was conducted to study

S. Y. Cheng; C. W. M. Yuen; C. W. Kan; K. K. L. Cheuk; W. A. Daoud; P. L. Lam; W. Y. I. Tsoi

2010-01-01

219

Growth of atmospheric nano-particles by heterogeneous nucleation of organic vapor  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosols is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size (~3 nm). Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect) may prevent ambient organics from condensing on these small clusters. Here, the contribution of organics to the initial cluster growth is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size leads to positive cluster number flux. This positive flux drives the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered the minimum particle size that can be grown through condensation. The conventional approach neglects the contribution from the cluster concentration gradient, and underestimates the cluster survival probabilities by a factor of up to 60 if early growth of clusters is due to both condensation of sulfuric acid and heterogeneous nucleation of organic vapors.

Wang, J.; McGraw, R. L.; Kuang, C.

2013-07-01

220

Assessment of metal concentrations in atmospheric particles from Burnaby Lake, British Columbia, Canada  

NASA Astrophysics Data System (ADS)

Trace metals were assessed in atmospheric particulates at Burnaby Lake, in the greater Vancouver area of British Columbia to assess concentrations, particle size distributions and deposition rates to an urban watershed. Week-long samples were collected over a period of 18 weeks in 1995 using a 13 stage low pressure impactor (LPI). Samples were analysed using inductively coupled plasma atomic emission spectroscopy (ICP). Aluminum, boron, calcium, iron, magnesium, manganese, sodium and strontium had a similar time series pattern and particle size distribution. For these metals, maximum concentrations occurred during weeks of low precipitation and exhibited a large peak in mid June. Their particle size distribution was mostly dominated by a large peak between 1.7-18.4 ?m with a secondary peak at <0.08 ?m. Metal concentrations were generally one to three orders of magnitude higher than those measured in a rural location 100 km away from Burnaby Lake but similar to those measured in urban Taipei, Taiwan. Concentrations of the highly toxic metals, arsenic, cadmium and lead were within current air quality guidelines, however boron exceeded the Ontario Ministry of Environment ambient air quality standard in two of the 16 samples. Deposition velocities ranged between 0.22 and 13 cm s -1 with the largest values corresponding to the coarse particle mode. Mean deposition rates ranged between 4.0 ?g m -2 d -1 and 650 mg m -2 d -1. Depending on the metal, yearly loadings to the watershed ranged from 90 kg to several thousand tonnes. Calcium, aluminum, boron and magnesium had the highest metal loadings to the watershed. Manganese also had relatively high loadings, a reflection of the high traffic density in the area. The relatively high metal deposition rates indicate that metal contribution from atmospheric sources may represent a significant portion of the total metal load to the Burnaby Lake watershed.

Brewer, R.; Belzer, W.

221

Exploiting an atmospheric model for automated invariant material identification in hyperspectral imagery  

NASA Astrophysics Data System (ADS)

The measured spectral radiance signature for a material can vary significantly due to atmospheric conditions and scene geometry. We show using a statistical analysis of a comprehensive physical model that the variation in a material's spectral signature lies in a low-dimensional space. The spectral radiance model includes reflected solar and sky radiation as well as path radiance. Signature variability is introduced by effects such as solar occlusion and variation in the concentrations of atmospheric gases aerosols. The MODTRAN 3.5 code was employed for computing radiative transfer aspects of the model. Using the new model, we develop a maximum likelihood algorithm for automatic material identification that is invariant to atmospheric conditions and scene geometry. We demonstrate the algorithm for the identification of exposed and concealed material samples in HYDICE imagery.

Slater, David; Healey, Glenn

1998-07-01

222

Critical current densities under action of charged particles on the structural materials  

Microsoft Academic Search

The method of critical current densities allows treating the experimental values of the erosion coefficients and scattering rate in the plasma-ion technological processes. An area of charged particle interaction with a material could be represented as the area in which a direct conversion of energy from a particle to the material and the area of heat propagation into the material

G. I. Kostyuk

2008-01-01

223

Molecular understanding of atmospheric particle formation from sulfuric acid and large oxidized organic molecules  

PubMed Central

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiälä boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions. PMID:24101502

Schobesberger, Siegfried; Junninen, Heikki; Bianchi, Federico; Lonn, Gustaf; Ehn, Mikael; Lehtipalo, Katrianne; Dommen, Josef; Ehrhart, Sebastian; Ortega, Ismael K.; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Hutterli, Manuel; Duplissy, Jonathan; Almeida, Joao; Amorim, Antonio; Breitenlechner, Martin; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Kajos, Maija; Keskinen, Helmi; Kirkby, Jasper; Kupc, Agnieszka; Kurten, Andreas; Kurten, Theo; Laaksonen, Ari; Mathot, Serge; Onnela, Antti; Praplan, Arnaud P.; Rondo, Linda; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Sipila, Mikko; Tome, Antonio; Tsagkogeorgas, Georgios; Vehkamaki, Hanna; Wimmer, Daniela; Baltensperger, Urs; Carslaw, Kenneth S.; Curtius, Joachim; Hansel, Armin; Petaja, Tuukka; Kulmala, Markku; Donahue, Neil M.; Worsnop, Douglas R.

2013-01-01

224

Aerosol Measurements in the Atmospheric Surface Layer at L'Aquila, Italy: Focus on Biogenic Primary Particles  

NASA Astrophysics Data System (ADS)

Two year measurements of aerosol concentration and size distribution (0.25 ?m < d < 30 ?m) in the atmospheric surface layer, collected in L'Aquila (Italy) with an optical particle counter, are reported and analysed for the different modes of the particle size distribution. A different seasonal behaviour is shown for fine mode aerosols (largely produced by anthropogenic combustion), coarse mode and large-sized aerosols, whose abundance is regulated not only by anthropogenic local production, but also by remote natural sources (via large scale atmospheric transport) and by local sources of primary biogenic aerosols. The observed total abundance of large particles with diameter larger than 10 ?m is compared with a statistical counting of primary biogenic particles, made with an independent technique. Results of these two observational approaches are analysed and compared to each other, with the help of a box model driven by observed meteorological parameters and validated with measurements of fine and coarse mode aerosols and of an atmospheric primary pollutant of anthropogenic origin (NOx). Except in winter months, primary biogenic particles in the L'Aquila measurement site are shown to dominate the atmospheric boundary layer population of large aerosol particles with diameter larger than 10 ?m (about 80 % of the total during summer months), with a pronounced seasonal cycle, contrary to fine mode aerosols of anthropogenic origin. In order to explain these findings, the main mechanisms controlling the abundance and variability of particulate matter tracers in the atmospheric surface layer are analysed with the numerical box-model.

Pitari, Giovanni; Coppari, Eleonora; De Luca, Natalia; Di Carlo, Piero; Pace, Loretta

2014-09-01

225

Aerosol Measurements in the Atmospheric Surface Layer at L'Aquila, Italy: Focus on Biogenic Primary Particles  

NASA Astrophysics Data System (ADS)

Two year measurements of aerosol concentration and size distribution (0.25 ?m < d < 30 ?m) in the atmospheric surface layer, collected in L'Aquila (Italy) with an optical particle counter, are reported and analysed for the different modes of the particle size distribution. A different seasonal behaviour is shown for fine mode aerosols (largely produced by anthropogenic combustion), coarse mode and large-sized aerosols, whose abundance is regulated not only by anthropogenic local production, but also by remote natural sources (via large scale atmospheric transport) and by local sources of primary biogenic aerosols. The observed total abundance of large particles with diameter larger than 10 ?m is compared with a statistical counting of primary biogenic particles, made with an independent technique. Results of these two observational approaches are analysed and compared to each other, with the help of a box model driven by observed meteorological parameters and validated with measurements of fine and coarse mode aerosols and of an atmospheric primary pollutant of anthropogenic origin (NOx). Except in winter months, primary biogenic particles in the L'Aquila measurement site are shown to dominate the atmospheric boundary layer population of large aerosol particles with diameter larger than 10 ?m (about 80 % of the total during summer months), with a pronounced seasonal cycle, contrary to fine mode aerosols of anthropogenic origin. In order to explain these findings, the main mechanisms controlling the abundance and variability of particulate matter tracers in the atmospheric surface layer are analysed with the numerical box-model.

Pitari, Giovanni; Coppari, Eleonora; De Luca, Natalia; Di Carlo, Piero; Pace, Loretta

2014-03-01

226

Particle Induced X-Ray Emission Analysis of Atmospheric Aerosols Collected in Upstate New York  

NASA Astrophysics Data System (ADS)

Elemental analysis of atmospheric aerosols collected in the historic Stockade District of Schenectady, New York, was performed using particle induced X-ray emission (PIXE) spectroscopy. This is part of a systematic study in the Mohawk River Valley of upstate New York to identify the sources and understand the transport, transformation, and effects of airborne pollutants and the connection between aerosols, the deposition of pollution, and the uptake of pollutants by wildlife and vegetation. The atmospheric aerosols were collected with a nine-stage cascade impactor that allows for the analysis of the particulate matter as a function of particle size. The samples were bombarded with 2-MeV proton beams from the Union College Pelletron Accelerator and the energy spectra of the X-rays were measured with a silicon drift detector. The X-ray spectra were analyzed using GUPIX software to extract the elemental concentrations of the particulate matter. The sample collection and analysis will be described, and preliminary results will be presented.

Gleason, Colin; Harrington, Charles; Schuff, Katie; Labrake, Scott; Vineyard, Michael

2009-10-01

227

The effect of atmospheric aerosol particles and clouds on net ecosystem exchange in the Amazon  

NASA Astrophysics Data System (ADS)

Carbon cycling in the Amazon is closely linked to atmospheric processes and climate in the region as a consequence of the strong coupling between the atmosphere and biosphere. This work examines the effects of changes in net radiation due to atmospheric aerosol particles and clouds on the net ecosystem exchange (NEE) of CO2 in the Amazon region. Some of the major environmental factors affecting the photosynthetic activity of plants, such as air temperature and relative humidity, were also examined. An algorithm for clear-sky irradiance was developed and used to determine the relative irradiance, f, which quantifies the percentage of solar radiation absorbed and scattered due to atmospheric aerosol particles and clouds. Aerosol optical depth (AOD) was calculated from irradiances measured with the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, onboard the Terra and Aqua satellites, and was validated with ground-based AOD measurements from AERONET (Aerosol Robotic Network) sun photometers. Carbon fluxes were measured using eddy covariance technique at the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) flux towers. Two sites were studied: the Jaru Biological Reserve (RBJ), located in Rondonia, and the Cuieiras Biological Reserve at the K34 LBA tower (located in a preserved region in the central Amazon). Analysis was performed continuously from 1999 to 2009 at K34 and from 1999 to 2002 at RBJ, and includes wet, dry and transition seasons. In the Jaru Biological Reserve, a 29% increase in carbon uptake (NEE) was observed when the AOD ranged from 0.10 to 1.5 at 550 nm. In the Cuieiras Biological Reserve, the aerosol effect on NEE was smaller, accounting for an approximate 20% increase in NEE. High aerosol loading (AOD above 3 at 550 nm) or high cloud cover leads to reductions in solar flux and strong decreases in photosynthesis up to the point where NEE approaches zero. The observed increase in NEE is attributed to an enhancement (~50%) in the diffuse fraction of photosynthetic active radiation (PAR). The enhancement in diffuse PAR can be done through increases in aerosols and/or clouds. In the present study, it was not possible to separate these two components. Significant changes in air temperature and relative humidity resulting from changes in solar radiation fluxes under high aerosol loading were also observed at both sites. Considering the long-range transport of aerosols in the Amazon, the observed changes in NEE for these two sites may occur over large areas in the Amazon, significantly altering the carbon balance in the largest rainforest in the world.

Cirino, G. G.; Souza, R. A. F.; Adams, D. K.; Artaxo, P.

2014-07-01

228

Photochemistry of iron(III)-carboxylato complexes in aqueous atmospheric particles  

NASA Astrophysics Data System (ADS)

Iron is always present in the atmosphere in concentrations from ~10-9 M (clouds, rain) up to ~10-3 M (fog, particles). Sources are mainly mineral dust emissions. Iron complexes are very good absorbers in the UV-VIS actinic region and therefore photo-chemically reactive. Iron complex photolysis leads to radical production and can initiate radical chain reactions, which is related to the oxidizing capacity of the atmosphere. These radical chain reactions are involved in the decomposition and transformation of a variety of chemical compounds in cloud droplets and deliquescent particles. Additionally, the photochemical reaction itself can be a degradation pathway for organic compounds with the ability to bind iron. Iron-complexes of atmospherically relevant coordination compounds like oxalate, malonate, succinate, glutarate, tartronate, gluconate, pyruvate and glyoxalate have been investigated in laboratory experiments. Iron speciation depends on the iron-ligand ratio and the pH. The most suitable experimental conditions were calculated with a speciation program (Visual Minteq). The solutions were prepared accordingly and transferred to a 1 cm quartz cuvette and flash-photolyzed with an excimer laser at wavelengths 308 or 351 nm. Photochemically produced Fe2+ has been measured by spectrometry at 510 nm as Fe(phenantroline)32+. Fe2+ overall effective quantum yields have been calculated with the concentration of photochemically produced Fe2+ and the measured energy of the excimer laser pulse. The laser pulse energy was measured with a pyroelectric sensor. For some iron-carboxylate systems the experimental parameters like the oxygen content of the solution, the initial iron concentration and the incident laser energy were systematically altered to observe an effect on the overall quantum yield. The dependence of some quantum yields on these parameters allows in some cases an interpretation of the underlying photochemical reaction mechanism. Quantum yields of malonate, glutarate and gluconate complexes lie in the range of 0.02

Weller, Christian; Herrmann, Hartmut

2010-05-01

229

Particle impact damping: influence of material and size  

E-print Network

of Vibration and Acoustics 114, 101-15. Structural damping enhancement via non-obstructive particle impact damping technique. 8. R. D. Friend and V. K. Kinra 2000 Journal of Sound and Vibration 233(1), 93- 118. Particle impact damping. 28... of Vibration and Acoustics 114, 101-15. Structural damping enhancement via non-obstructive particle impact damping technique. 8. R. D. Friend and V. K. Kinra 2000 Journal of Sound and Vibration 233(1), 93- 118. Particle impact damping. 28...

Marhadi, Kun Saptohartyadi

2005-02-17

230

Particle/vapor concentrations and distributions of PAHs in the atmosphere of southern Chesapeake Bay  

SciTech Connect

Atmospheric PAH concentrations were measured at four sites characterized as rural (Haven Beach), semiurban (York River), urban (Hampton), and industrialized (Elizabeth River) areas as part of a study to quantify gaseous exchange fluxes across the air-water interface of southern Chesapeake Bay. Aerosol particle-associated PAH concentrations were similar at all sites; however, PAH vapor concentrations in the urban areas were as much as a factor of 50 greater than those at the rural site. Mean total PAH concentrations ranged from 7.87 ng/m{sup 3} at the rural site to 92.8 ng/m{sup 3} at the urban site. Daily total PAH concentrations ranged from 1.60 to 198 ng/m{sup 3}. Exponential increases in PAH vapor concentrations with temperature were observed at the non-rural sites, suggesting volatilization from contaminated surfaces during warmer weather; whereas PAH vapor concentrations at the rural Haven Beach site exhibited little seasonal variability. Aerosol particle-associated PAH levels were similar at all sites and increased in winter due to the temperature dependence of vapor-particle partitioning, increased sources from combustion of fossil fuel and wood for home heating, and cold condensation of source vapors to background aerosols as air masses are dispersed to remote regions. Plots of log K{sub d} vs. log P{sub sat,SC1} indicate PAH partitioning is not at equilibrium in rural areas of Southern Chesapeake Bay. In addition, plots of log K{sub d} vs. 1/T for individual PAHs indicate difference particle characteristics or partitioning processes influence particle/vapor distributions at the urban and rural sites.

Gustafson, K.E. [Univ. of West Florida, Pensacola, FL (United States). Inst. for Coastal and Estuarine Research; Dickhut, R.M. [Coll. of William and Mary, Gloucester Point, VA (United States)

1995-12-31

231

Hygroscopic properties of smoke-generated organic aerosol particles emitted in the marine atmosphere  

NASA Astrophysics Data System (ADS)

During the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE), a plume of organic aerosol was produced by a smoke generator and emitted into the marine atmosphere from aboard the R/V Point Sur. In this study, the hygroscopic properties and the chemical composition of the plume were studied at plume ages between 0 and 4 h in different meteorological conditions. In sunny conditions, the plume particles had very low hygroscopic growth factors (GFs): between 1.05 and 1.09 for 30 nm and between 1.02 and 1.1 for 150 nm dry size at a relative humidity (RH) of 92%, contrasted by an average marine background GF of 1.6. New particles were produced in large quantities (several 10 000 cm-3), which lead to substantially increased cloud condensation nuclei (CCN) concentrations at supersaturations between 0.07 and 0.88%. Ratios of oxygen to carbon (O : C) and water-soluble organic mass (WSOM) increased with plume age: from < 0.001 to 0.2, and from 2.42 to 4.96 ?g m-3, respectively, while organic mass fractions decreased slightly (~ 0.97 to ~ 0.94). High-resolution aerosol mass spectrometer (AMS) spectra show that the organic fragment m/z 43 was dominated by C2H3O+ in the small, new particle mode and by C3H7+ in the large particle mode. In the marine background aerosol, GFs for 150 nm particles at 40% RH were found to be enhanced at higher organic mass fractions: an average GF of 1.06 was observed for aerosols with an organic mass fraction of 0.53, and a GF of 1.04 for an organic mass fraction of 0.35.

Wonaschütz, A.; Coggon, M.; Sorooshian, A.; Modini, R.; Frossard, A. A.; Ahlm, L.; Mülmenstädt, J.; Roberts, G. C.; Russell, L. M.; Dey, S.; Brechtel, F. J.; Seinfeld, J. H.

2013-10-01

232

Retrieving of Microphysical Properties of Spheroidal Particles in the Atmosphere-Surface System  

NASA Astrophysics Data System (ADS)

In this presentation, we continue our study of the Levenberg-Marquardt algorithm [1, 2] as a tool for retrieval of properties of particles, suspended in the plane-parallel atmosphere coupled with the reflecting surface [3]. The effect of polarization of light is included. The Levenberg-Marquardt algorithm provides an iterative solution to the problem of minimization of a function over a space of its parameters. Each iteration involves solution of the forward problem and computation of the Jacobian matrix (the derivatives of signal over optical parameters). The recently developed code APC (Atmospheric Polarization Computations) is used to solve the forward problem [4, 5]. We use O.Dubovik's et al. [6] package to simulate scattering by spheroidal particles. Unlike for the purely spherical particles (Mie scattering), the Jacobian matrix for spheroids is computed numerically. We will consider retrievals over the land and the ocean with the bidirectional polarization distribution functions from [7-8]. Using MISR observation geometry and spectral bands [9] as an example, we will discuss the problem of convergence of iterations, sensitivity of the algorithm to the initial guess, the signal-to-noise ratio, and the geometry of observation. Possible ways of acceleration of iterations will be discussed, as well as the role of polarization in the retrieval process. References: 1. Levenberg K, Q. App. Math., 1944, V.2, P.164. 2. Marquardt D, J. Appl. Math., 1963, V.11, N.2, P.431. 3. Korkin S, Lyapustin A, AGU 2012, A23A-011. 4. Korkin S et al., JQSRT, 2013, V.127, P.1 5. ftp://climate1.gsfc.nasa.gov/skorkin/ 6. Dubovik O et al., Geophys. Res. Letters, 2006, V.111, D11208. 7. Ota Y, et al., JQSRT, 2010, V.111, P.878. 8. Nadal F, Breon F-M, IEEE Trans. Geos. Rem. Sens., 1999, V.37, N.3, P.1709. 9. http://www-misr.jpl.nasa.gov/Mission/misrInstrument/

Korkin, S.; Lyapustin, A.

2013-12-01

233

Atmospheric trace element concentrations in total suspended particles near Paris, France  

NASA Astrophysics Data System (ADS)

To evaluate today's trace element atmospheric concentrations in large urban areas, an atmospheric survey was carried out for 18 months, from March 2002 to September 2003, in Saclay, nearby Paris. The total suspended particulate matter (TSP) was collected continuously on quartz fibre filters. The TSP contents were determined for 36 elements (including Ag, Bi, Mo and Sb) using two analytical methods: Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The measured concentrations were in agreement within the uncertainties with the certified values for the polycarbonate reference material filter SRM-2783 (National Institute for Standard Technology NIST, USA). The measured concentrations were significantly lower than the recommended atmospheric concentrations. In 2003, the Pb atmospheric level at Saclay was 15 ng/m 3, compared to the 500 ng/m 3 guideline level and to the 200 ng/m 3 observed value in 1994. The typical urban background TSP values of 1-2, 0.2-1, 4-6, 10-30 and 3-5 ng/m 3 for As, Co, Cr, Cu and Sb, respectively, were inferred from this study and were compared with the literature data. The typical urban background TSP concentrations could not be realised for Cd, Pb and Zn, since these air concentrations are highly influenced by local features. The Zn concentrations and Zn/Pb ratio observed in Saclay represented a characteristic fingerprint of the exceptionally large extent of zinc-made roofs in Paris and its suburbs. The traffic-related origin of Ba, Cr, Cu, Pb and Sb was demonstrated, while the atmospheric source(s) of Ag was not identified.

Ayrault, Sophie; Senhou, Abderrahmane; Moskura, Mélanie; Gaudry, André

2010-09-01

234

Children exposure to atmospheric particles in indoor of Lisbon primary schools  

NASA Astrophysics Data System (ADS)

Evidence continues to emerge showing that poor Indoor Air Quality (IAQ) can cause illness requiring absence from schools, and can cause acute health symptoms that decrease students' performance. Since children spend on average 7-11 h per weekday at school, the IAQ in classrooms is expected to play a key role in the assessment of the effects of their personal exposure to air pollution. Within this context the present study was conducted in order to fulfill three primary objectives 1) to measure the levels and the element composition of PM 2.5 and PM 2.5-10, in three primary schools placed in Lisbon, in order to assess the children exposure to these pollutants; 2) to study the relationship between indoor and outdoor atmospheric particles concentrations and 3) to investigate the sources of high aerosols concentrations in classrooms. In the studied classrooms, the concentrations of coarse particles significantly exceeded the ambient levels. Element concentrations suggested that the physical activity of students highly contributed to the re-suspension of sedimented particles. The high levels of CO 2 indicated that in these schools the ventilation was inadequate. This fact contributed to the establishment of poor IAQ.

Almeida, Susana Marta; Canha, Nuno; Silva, Ana; Freitas, Maria do Carmo; Pegas, Priscilla; Alves, Célia; Evtyugina, Margarita; Pio, Casimiro Adrićo

2011-12-01

235

Material removal mode affected by the particle size in fluid jet polishing.  

PubMed

As a newly developed ultrasmooth polishing technique, fluid jet polishing (FJP) has been widely used for optical glass polishing. The size of the particle in the polishing slurry has a great influence on the material removal rate and quality of the processed surface. The material removal mode affected by the particle size is investigated in detail. Particle trajectories with different size are calculated by numerical simulations in the FJP process. Simulation results demonstrate that the particle with large size will seriously deviate from the fluid streamline and almost impact on the workpiece along a straight line in the initial incident direction. The larger is the particle size, the more deviation will occur. Impact models are established based on different particle trajectories. A polishing experiment was conducted to verify the feasibility of the mode. Experiment results show that the particle size has a great influence on the material removal mode in FJP with the same process parameters. Material is removed in the plastic mode with higher removal rate and worse surface roughness for a larger-sized particle, while the material removal occurring in the elastic mode has a much lower removal rate and smoother surface for the smaller-sized particle. Material is removed by chemical impact reaction between the particle and the surface within the elastic mode, and a smooth surface with no damage is obtained after the FJP process. PMID:24513743

Peng, Wenqiang; Guan, Chaoliang; Li, Shengyi

2013-11-20

236

Optical materials for surface-enhanced Raman applications based on sol-gel encapsulated gold particles  

Microsoft Academic Search

A photochemical method of producing nanometer gold particles in optically transparent sol-gel silicate materials is described. Organometallic gold precursor compounds are dissolved in the sol and encapsulated in the growing silicate network. Irradiation of the doped monoliths with ultraviolet light causes the photodeposition of gold particles within the silica gel or xerogel. The particles are characterized by their electronic absorption

Fatemeh Akbarian; Bruce S. Dunn; Jeffrey I. Zink

1994-01-01

237

Atmosphere  

NSDL National Science Digital Library

What is this atmosphere that surrounds the Earth? This instructional tutorial, part of an interactive laboratory series for grades 8-12, introduces students to the structure, effects, and components of the atmosphere. Here students investigate the composition of the atmosphere; effects of temperature, pressure, and ozone; the greenhouse effect; and how Earth compares with other planets. Interactive activities present students with opportunities to explore ideas and answer questions about the atmosphere, including its structure, the making of ozone, rocket launching, and measuring the atmosphere. Pop-up boxes provide additional information on topics such as dust, rain, and atmospheric composition. Students complete a final written review of six questions about the atmosphere. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

238

Atmospheric new particle formation and the potential role of organic peroxides  

NASA Astrophysics Data System (ADS)

New particle formation in the atmosphere belongs to the currently most discussed aspects of atmospheric aerosols with significant implications for cloud formation and microphysics, once these particles have grown beyond about 50 nm in particle diameter. If these particles act as cloud condensation or ice nuclei they can affect the radiation budget at the Earths surface and cause climate couplings important to understand when aiming to predict climate change scenarios. One aspect widely discussed is the potential contribution of organic trace gases from anthropogenic and biogenic sources. In this study we analysed datasets from a Central European measurement station in Germany in a spruce forest approximately 800 m above sea level and a distance of about 20 km to Frankfurt (southeast). Continuous particle size distribution measurements were classified in nucleation-event or not and unidentified and intercompared to meteorological and basic trace gas observations. Additionally meteorological backtrajektories calculated by the German Weather Service for the station every 12 hours have been considered. These led to the following conclusions: Nucleation was most likely if (A) the air has not get significantly into touch with the surface within the last days, or if (B) at least human impact was minor and the air faced forest surfaces mainly (northwest). As observed already in Hyytiälä (Finland) nucleation appeared, when the relative humidity and ambient water vapour mixing ratio were low, ozone was high and the condensation sink was small. A further important point was the amount of global radiation measured at the Taunus Observatory (Mt. Kleiner Feldberg). The higher the radiation, the more likely a nucleation event and the more intense. Temperature impacted on the intensity of nucleation, i.e. the higher the temperature the more intense the event, but did not directly affect the occurrence of an event or not, if a threshold value of ca. -6 °C was exceeded. This latter observation indicates a potential role of biogenic volatile organic compounds (VOCs) as their emission is strongly coupled to temperature. Because of our observations in the laboratory and beacuse of observed nighttime events, we approximated the concentration of different radicals, e.g. OH, HO2 and RO2. The values of RO2 and especially the ones of biogenic (e.g. terpene) origin showed a good correlation with new particle formation occurrence and seemed to be one essential point of several to allow new particle formation to occur. This might be an indication of the important role of the biosphere and its stress effects for the particle formation process. The seasonality observed for the time period since February 2008 displayed two maxima in May and August, September with a minimum in June, when the weather conditions were more humid and is in line with the observations made above. July and August displayed the higest HO2 concentrations, which will act as a sink for the organic peroxy radicals. In connection to the supressive effect of water vapour on terpene induced nucleating molecules (secondary ozonides) this might serve as an explanation for the commonly observed summer minimum in nucleation events.

Trawny, Katrin; Bonn, Boris; Jacobi, Stefan

2010-05-01

239

Modeling of dust-particle behavior for different materials in plasmas  

SciTech Connect

The behavior of dust particles made of different fusion-related materials (Li, Be, B, C, Fe, Mo, or W) in tokamak plasmas is simulated using the dust transport code DUSTT [A. Pigarov et al., Phys. Plasmas 12, 122508 (2005)]. The dependencies of the characteristic lifetime of dust particles on plasma parameters are compared for the different dust materials. The dynamics of dust particles in the tokamak edge plasma is studied and the effects of dust material on the acceleration, heating, and evaporation/sublimation of particles are analyzed.

Tanaka, Y.; Pigarov, A. Yu.; Smirnov, R. D.; Krasheninnikov, S. I.; Ohno, N.; Uesugi, Y. [Division of Electrical Engineering and Computer Science, Kanazawa University, Kakuma, Kanazawa 920-1192 (Japan); Department of Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, California 92093 (United States); EcoTopia Science Institute, Nagoya University, Furo-cho 464-8601 (Japan); Department of Electrical and Electronic Engineering, Kanazawa University, Kakuma, Kanazawa 920-1192 (Japan)

2007-05-15

240

Hygroscopic properties of organic aerosol particles emitted in the marine atmosphere  

NASA Astrophysics Data System (ADS)

During the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE), a plume of organic aerosol was produced and emitted into the marine atmosphere from aboard the research vessel R/V Point Sur. In this study, the hygroscopic properties and the chemical composition of the plume were studied at plume ages between 0 and 4 h in different meteorological conditions. In sunny conditions, hygroscopic growth factors (GFs) at a relative humidity (RH) of 92% were low, but increased at higher plume ages: from 1.05 to 1.09 for 30 nm and from 1.05 to 1.1 for 150 nm dry size (contrasted by an average marine background GF of 1.6). Simultaneously, ratios of oxygen to carbon (O:C) increased from < 0.001 to 0.2, water-soluble organic mass (WSOM) concentrations increased from 2.42 to 4.96 ?g m-3, and organic mass fractions decreased slightly (~ 0.97 to ~ 0.94). New particles were produced in large quantities (several 10 000 cm-3), which lead to substantially increased cloud condensation nuclei (CCN) concentrations at supersaturations between 0.07-0.88%. High-resolution aerosol mass spectrometer (AMS) spectra show that the organic fragment m/z 43 was dominated by C2H3O+ in the small particle mode and by C3H7+ in the large particle mode. In the marine background aerosol, GFs for 150 nm particles at 40% RH were found to be enhanced at higher organic mass fractions. An average GF of 1.06 was observed for aerosols with an organic mass fraction of 0.53, a GF of 1.04 for an organic mass fraction of 0.35.

Wonaschütz, A.; Coggon, M.; Sorooshian, A.; Modini, R.; Frossard, A. A.; Ahlm, L.; Mülmenstädt, J.; Roberts, G. C.; Russell, L. M.; Dey, S.; Brechtel, F. J.; Seinfeld, J. H.

2013-05-01

241

Material response to particle impact during abrasive jet machining of alumina ceramics  

Microsoft Academic Search

Abrasive jet machining (AJM), a specialized form of shot blasting, attracts much attention as a hopeful micro-machining method for hard, brittle materials such as structural ceramics. The present paper attempts to identify the material response of alumina ceramics to the abrasive particle impact in the AJM process. Three kinds of commercial abrasive particles were utilized to dimple the sintered alumina

Manabu Wakuda; Yukihiko Yamauchi; Shuzo Kanzaki

2003-01-01

242

Ignition Resistance of Polymeric Materials to Particle Impact in High-Pressure Oxygen  

NASA Technical Reports Server (NTRS)

Particle impact ignition has been the primary cause of numerous fires in oxygen systems. This ignition phenomenon is known to occur where particles are present in high-velocity gas, and where impact occurs on a flammable material. The particle impact ignition behavior of many metals has been widely studied, but the particle impact ignition behavior of polymeric materials is relatively unknown. Particle impact ignition in polymeric materials is a concern as these materials are commonly used in component seat and seal applications, where high-velocity particle impacts can occur. This study evaluates several polymeric materials and compares the minimum temperature required for ignition (threshold temperature) of these materials: Kel-F 81 (CTFE), Teflon (PTFE), PEEK, Vespel SP-21, and Nylon 6/6. The materials were configured as targets in the White Sands Test Facility high-velocity particle impact test system. Gaseous oxygen was flowed at 4000 psi and sonic velocity, and the targets were impacted with 2000-micron aluminum 2017 particles. This paper discusses the results of these tests and ranks the materials according to their threshold temperatures at these conditions.

Forsyth, Elliot T.; Stolzfus, Joel M.; Fries, Joseph (Technical Monitor)

2000-01-01

243

Preparation of Polyhedral Graphite Particles by Arc Discharge under Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

Polyhedral graphite particles (PGPs) were synthesized by arc discharge method under atmospheric pressure in the relatively short electrode gap distance of 1 mm, while graphene flakes and turbostratic graphite were found by increasing the electrode gap distance. The selective synthesis of nano-sized carbon allotropes was controlled by the contribution of carbon ions and carbon radicals with the change of the electrode gap distance. The formation mechanism of PGPs and other carbon allotropes were proposed according to the experimental results. The low concentration of carbon ions to carbon radicals contributes to the formation of PGPs. In contrast, relatively high concentration of carbon ions to carbon radicals contributes to the formation of graphene flakes and turbostratic graphite.

Liang, Feng; Shimizu, Tasuku; Tanaka, Manabu; Choi, Sooseok; Watanabe, Takayuki

2013-01-01

244

Gas-to-Particle Conversion in Surface Discharge Nonthermal Plasmas and Its Implications for Atmospheric Chemistry  

PubMed Central

This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed. PMID:22163781

Kim, Hyun-Ha; Ogata, Atsushi

2011-01-01

245

Heterogeneous Combustion Particles with Distinctive Light-Absorbing and Light-Scattering Phases as Mimics of Internally-Mixed Ambient Atmospheric Particles  

NASA Astrophysics Data System (ADS)

Particles with heterogeneously-distributed light-absorbing and light-scattering phases were generated from incomplete combustion or thermal decomposition to mimic real atmospheric particles with distinctive optical properties. Individual particles and particle populations were characterized microscopically. The purpose was to examine how optical property measurements of internally-mixed ambient air particles might vary based on the properties of laboratory-generated particles produced under controlled conditions. The project is an initial stage in producing reference samples for calibrating instrumentation for monitoring climatically-important atmospheric aerosols. Binary-phase particles containing black carbon (BC) and a metal or a metal oxide phase were generated from the thermal decomposition or partial combustion of liquid fuels at a variety of temperatures from 600 °C to 1100 °C. Fuels included mixtures of toluene or isooctane and iron pentacarbonyl or titanium tetrachloride. Scanning electron microscopy with energy-dispersive x-ray spectroscopy revealed that burning the fuels at different temperatures resulted in distinctive differences in morphology and carbon vs. metal/metal oxide composition. Particles from toluene/Fe(CO)5 thermal decomposition exhibited aggregated morphologies that were classified as dendritic, soot-like, globular, or composited (dendritic-globular). Particles from isooctane/TiCl4 combustion were typically spherical with surface adducts or aggregates. Diameters of the BC/TiO2 particles averaged 0.68 ?m to 0.70 ?m. Regardless of combustion temperature, the most abundant particles in each BC/TiO2 sample had an aspect ratio of 1.2. However, for the 600 °C and 900 °C samples the distribution of aspect ratios was skewed toward much larger ratios suggesting significant chainlike aggregation. Carbon and titanium compositions (wt.) for the 600 °C sample were 12 % and 53 %, respectively. In contrast, the composition trended in the opposite direction for the 900 °C sample with carbon at 57 % and titanium at 27 %.

Conny, J. M.; Ma, X.; Gunn, L. R.

2011-12-01

246

Atmospheric particles retrieval using satellite remote sensing: Applications for sandstorms and volcanic clouds  

NASA Astrophysics Data System (ADS)

This thesis is concerned with atmospheric particles produced by sandstorms and volcanic eruptions. Three studies were conducted in order to examine particle retrieval methodology, and apply these towards an improved understanding of large-scale sandstorms. A thermal infrared remote sensing retrieval method developed by Wen and Rose [1994], which retrieves particle sizes, optical depth, and total masses of silicate particles in the volcanic cloud, was applied to an April 07, 2001 sandstorm over northern China, using MODIS. Results indicate that the area of the dust cloud observed was 1.34 million km2, the mean particle radius of the dust was 1.44 mum, and the mean optical depth at 11 mum was 0.79. The mean burden of dust was approximately 4.8 tons/km2 and the main portion of the dust storm on April 07, 2001 contained 6.5 million tons of dust. The results are supported by both independent remote sensing data (TOMS) and in-situ data for a similar event in 1998, therefore suggesting that the technique is appropriate for quantitative analysis of silicate dust clouds. This is the first quantitative evaluation of annual and seasonal dust loading in 2003 produced by Saharan dust storms by satellite remote sensing analysis. The retrieved mean particle effective radii of 2003 dust events are between 1.7--2.6 mum which is small enough to be inhaled and is hazardous to human health. The retrieved yearly dust mass load is 658--690 Tg, which is ˜45% of the annual global mineral dust production. Winter is the heaviest dust loading season in the year 2003, which is more than 5 times larger than that in the summer season in 2003.The mean optical depths at 11 mum in the winter season (around 0.7) are higher than those in the summer season (around 0.5). The results could help both meteorologists and environmental scientists to evaluate and predict the hazard degree caused by Saharan dust storms. (Abstract shortened by UMI.)

Gu, Yingxin

247

Risk Assessment Related to Atmospheric Polycyclic Aromatic Hydrocarbons in Gas and Particle Phases near Industrial Sites  

PubMed Central

Background: Inhalation is one of the main means of human exposure to polycyclic aromatic hydrocarbons (PAHs) because of their ubiquitous presence in the atmosphere. However, most studies have considered only PAHs found in the particle phase and have omitted the contribution of the gas-phase PAHs to the risk. Objective: We estimated the lifetime lung cancer risk from PAH exposure by inhalation in people living next to the largest chemical site in Southern Europe and the Mediterranean area. Methods: We determined 18 PAHs in the atmospheric gas and particle phase. We monitored the PAHs for 1 year in three locations near the chemical site in different seasons. We used toxic equivalence factors to calculate benzo[a]pyrene (BaP) equivalents (BaP-eq) for individual PAHs and applied the World Health Organization unit risk (UR) for BaP (UR = 8.7 × 10–5) to estimate lifetime cancer risks due to PAH exposures. Results: We observed some spatial and seasonal variability in PAH concentrations. The contribution of gas-phase PAHs to the total BaP-eq value was between 34% and 86%. The total estimated average lifetime lung cancer risk due to PAH exposure in the study area was 1.2 × 10–4. Conclusions: The estimated risk was higher than values recommended by the World Health Organization and U.S. Environmental Protection Agency but lower than the threshold value of 10–3 that is considered an indication of definite risk according to similar risk studies. The results also showed that risk may be underestimated if the contributions of gas-phase PAHs are not considered. PMID:21478082

Ramirez, Noelia; Cuadras, Anna; Marce, Rosa Maria

2011-01-01

248

Fragmentation and Growth Energetics of Clusters Relevant to Atmospheric New Particle Formation  

NASA Astrophysics Data System (ADS)

The exact mechanisms by which small clusters form and grow in the atmosphere are poorly understood, but this process may significantly impact cloud condensation nuclei number concentrations and global climate. Sulfuric acid is the key chemical component to new particle formation. However, basic species such as ammonia are also important. Few laboratory experiments address the kinetics or thermodynamics of acid and base incorporation into small clusters. This work utilizes a Fourier transform ion cyclotron resonance mass spectrometer equipped with surface-induced dissociation (FTICR-SID) to investigate time- and collision energy-resolved fragmentation of positively charged ammonium bisulfate clusters. The assumption underlying the experiment is that cluster growth can be considered the reverse of cluster fragmentation. Critical energies for fragmentation are obtained from Rice-Ramsperger-Kassel-Marcus/Quasi-Equilibrium Theory (RRKM/QET) modeling of the experimental data and are compared to quantum chemical calculations of the thermodynamics of cluster fragmentation. Fragmentation of ammonium bisulfate clusters occurs by two pathways: 1) a two-step pathway whereby the cluster sequentially loses ammonia followed by sulfuric acid and 2) a one-step pathway whereby the cluster loses an ammonium bisulfate molecule. Experimental critical energies for loss of an ammonia molecule and loss of an ammonium bisulfate molecule are higher than the thermodynamic values. If cluster growth is considered the reverse of cluster fragmentation, these results suggest that these clusters can grow by first adding sulfuric acid and then adding ammonia. Additionally, these results suggest the presence of an activation barrier to describe the incorporation of ammonia into small acidic clusters and therefore imply that kinetically (i.e. diffusion) limited growth should not be assumed. An important corollary is that models of atmospheric new particle formation should be revised to consider activation barriers to individual chemical steps along the growth pathway.

Bzdek, B. R.; DePalma, J. W.; Ridge, D. P.; Laskin, J.; Johnston, M. V.

2013-12-01

249

Influences of fireworks on chemical characteristics of atmospheric fine and coarse particles during Taiwan's Lantern Festival  

NASA Astrophysics Data System (ADS)

In recent years, the celebration activities of various folk-custom festivals have been getting more and more attention from the citizens in Taiwan. Festivities throughout the whole island are traditionally accompanied by loud and brightly colored firework displays. Among these activities, the firework displays during Taiwan's Lantern Festival in Kaohsiung harbor is one of the largest festivals in Taiwan each year. Therefore, it is of importance to investigate the influence of fireworks displays on the ambient air quality during the Taiwan's Lantern Festival. Field measurements of atmospheric particulate matter (PM) were conducted on February 9th-11th, 2009 during Taiwan's Lantern Festival in Kaohsiung City. Moreover, three kinds of fireworks powders obtained from the same manufacturing factory producing Kaohsiung Lantern Festival fireworks were burned in a self-designed combustion chamber to determine the physicochemical properties of the fireworks' particles and to establish the source profile of firework burning. Several metallic elements of PM during the firework display periods were notably higher than those during the non-firework periods. The concentrations of Mg, K, Pb, and Sr in PM2.5 during the firework periods were 10 times higher than those during the non-firework periods. Additionally, the Cl-/Na+ ratio was approximately 3 during the firework display periods as Cl- came from the chlorine content of the firework powder. Moreover, the OC/EC ratio increased up to 2.8. Results obtained from PCA and CMB receptor modeling showed that major sources of atmospheric particles during the firework display periods in Kaohsiung harbor were fireworks, vehicular exhausts, soil dusts and marine sprays. Particularly, on February 10th, the firework displays contributed approximately 25.2% and 16.6% of PM10 at two downwind sampling sites, respectively.

Tsai, Hsieh-Hung; Chien, Li-Hsing; Yuan, Chung-Shin; Lin, Yuan-Chung; Jen, Yi-Hsiu; Ie, Iau-Ren

2012-12-01

250

Detection of preferential particle orientation in the atmosphere: Development of an alternative polarization lidar system  

NASA Astrophysics Data System (ADS)

Increasing interest in polarimetric characterization of atmospheric aerosols has led to the development of complete sample-measuring (Mueller) polarimeters that are capable of measuring the entire backscattering phase matrix of a probed volume. These Mueller polarimeters consist of several moving parts, which limit measurement rates and complicate data analysis. In this paper, we present the concept of a less complex polarization lidar setup for detection of preferential orientation of atmospheric particulates. On the basis of theoretical considerations of data inversion stability and propagation of measurement uncertainties, an optimum optical configuration is established for two modes of operation (with either a linear or a circular polarized incident laser beam). The conceptualized setup falls in the category of incomplete sample-measuring polarimeters and uses four detection channels for simultaneous measurement of the backscattered light. The expected performance characteristics are discussed through an example of a typical aerosol with a small fraction of particles oriented in a preferred direction. The theoretical analysis suggests that achievable accuracies in backscatter cross-sections and depolarization ratios are similar to those with conventional two-channel configurations, while in addition preferential orientation can be detected with the proposed four-channel system for a wide range of conditions.

Geier, Manfred; Arienti, Marco

2014-12-01

251

Acidic gases and nitrate and sulfate particles in the atmosphere in the city of Guadalajara, México.  

PubMed

Atmospheric concentrations of nitrous acid, nitric acid, nitrate and sulfate particles were obtained in this study from April to June 2008 in the center of the city of Guadalajara, while concentrations of ozone, sulfur dioxide, nitrogen dioxide and meteorological parameters (temperature and relative humidity), were acquired by the Secretarķa del Medio Ambiente para el Desarrollo Sustentable del Estado de Jalisco (SEMADES). The results showed that nitric acid (2.7 ?g m(-3)) was 2.7 times higher than nitrous acid (1.0 ?g m(-3)). The sulfur dioxide (SO(2)) concentration indicated an opposite trend to sulfate (SO(4) (2-)), with the average concentration of SO(2) (6.9 ?g m(-3)) higher in almost the entire period of study. The sulfur conversion ratio (Fs, 24.9%) and nitrogen conversion ratio (Fn, 6.2%), were revealed to be similar to that reported in other urban areas during warm seasons. It is also noted that ozone is not the main oxidizer of nitrogen dioxide and sulfur dioxide. This determination was made by taking into account the slightly positively correlation determined for Fn (r(2) = 0.084) and Fs (r(2) = 0.092) with ozone that perhaps suggests there are other oxidizing species such as the radical OH, which are playing an important role in the processes of atmospheric oxidation in this area. PMID:22358115

Saldarriaga-Noreńa, Hugo; Waliszewski, Stefan; Murillo-Tovar, Mario; Hernįndez-Mena, Leonel; de la Garza-Rodrķguez, Iliana; Colunga-Urbina, Edith; Cuevas-Ordaz, Rosalva

2012-05-01

252

Be-7 nuclei produced by galactic cosmic rays and solar energetic particles in the earth's atmosphere  

NASA Astrophysics Data System (ADS)

Be-7 radioactive nuclei with a half-life of 53.3 days result from spallation reactions of galactic cosmic rays(GCR) and solar energetic particles (SEP) with N and O nuclei in the Earth's atmosphere. We calculate the average global production of Be-7 in the atmosphere by GCR and SEP The result indicates that an intense SEP event produces a large amount of Be-7 in the polar stratosphere and part of them could be transported to the surface at lower latitudes. The ground-level measurement of Be-7 in Japan exhibits the possibility of enhancement in the Be-7 radioactivity associated with the intense SEP event on July 14, 2000. In addition, the present experiment shows seasonal variations in the surface Be-7 concentration which peaks in spring and autumn. We discuss the possible air mass mixing between the stratosphere and troposphere to explain the measured seasonal variations. The surface concentration of Pb-210 nuclei indicates a similar trend to that of Be-7 and we suggest two possible explanations.

Yoshimori, M.; Hirayama, H.; Mori, S.; Sasaki, K.; Sakurai, H.

253

Micrometer-sized hygroscopic particles in the atmosphere: Aircraft measurement in the Arctic  

NASA Astrophysics Data System (ADS)

Aircraft measurements of concentrations and size distributions of nuclei between 1 and 11 ?m diameter were made in cloud-free air at altitudes below 6.2 km (approximately -30°C), using a new instrument (the cloudscope) north of Barrow, Alaska, during the First International Satellite Cloud Climatology Project Regional Experiment/Arctic Clouds Experiment (FIRE III/ACE) in May 1998. Data were obtained at various flight levels in the vicinity of a Canadian icebreaker frozen into and moving with the Arctic Ocean ice field. Ice field movements caused the frozen ocean surface to develop leads that were visible from the aircraft. Particles were collected at the stagnation point of a forward facing 3 mm diameter optical flat maintained at or above stagnation point temperatures. Images from a 425 ?m × 320 ?m area were video-recorded, and concentrations were corrected for collection efficiency based on ambient airspeed, temperature, and assumed particle density. At low ambient relative humidities, crystallized particles were collected directly, and their hygroscopic character was determined by observing growth characteristics following flight into regions of higher relative humidity. Solution drops collected at high relatively humidities were crystallized with controlled heating to approximately a hemispherical shape. Particles with a dry diameter greater than 1 ?m, the detection threshold, to 11 ?m were found at concentrations up to 4 L-1. Concentrations were variable with altitude, and on occasion no particles were observed for periods up to 1 hour about 50 L of air. Concentrations sufficient to initiate coalescence drizzle as clouds form were observed and may be of importance in ice nucleation. Comparisons with cloud condensation nuclei (CCN) measurements (providing the collected droplets) show that on occasion the large particles (providing the collector drops) comprised a significant component of the mass of hygroscopic material. There is a gap in measurement of particles having known hygroscopic properties in that measurements of CCN have an upper limit of 0.3 ?m dry diameter and the cloudscope has a lower limit of 1 ?m; substantial mass of hygroscopic material could lie within this range.

Meyers, Matthew B.; Hallett, John

2001-12-01

254

Shadow-insensitive material detection/classification with atmospherically corrected hyperspectral imagery  

NASA Astrophysics Data System (ADS)

Shadow-insensitive detection or classification of surface materials in atmospherically corrected hyperspectral imagery can be achieved by expressing the reflectance spectrum as a linear combination of spectra that correspond to illumination by the direct sum and by the sky. Some specific algorithms and applications are illustrated using HYperspectral Digital Imagery Collection Experiment (HYDICE) data.

Adler-Golden, Steven M.; Levine, Robert Y.; Matthew, Michael W.; Richtsmeier, Steven C.; Bernstein, Lawrence S.; Gruninger, John H.; Felde, Gerald W.; Hoke, Michael L.; Anderson, Gail P.; Ratkowski-, Anthony

2001-08-01

255

Shadow-insensitive material detection\\/classification with atmospherically corrected hyperspectral imagery  

Microsoft Academic Search

Shadow-insensitive detection or classification of surface materials in atmospherically corrected hyperspectral imagery can be achieved by expressing the reflectance spectrum as a linear combination of spectra that correspond to illumination by the direct sum and by the sky. Some specific algorithms and applications are illustrated using HYperspectral Digital Imagery Collection Experiment (HYDICE) data.

Steven M. Adler-Golden; Robert Y. Levine; Michael W. Matthew; Steven C. Richtsmeier; Lawrence S. Bernstein; John H. Gruninger; Gerald W. Felde; Michael L. Hoke; Gail P. Anderson; Anthony Ratkowski

2001-01-01

256

HEAT GENERATION OF SPENT BED MATERIALS FROM ATMOSPHERIC FLUIDIZED-BED COMBUSTION OF COAL  

EPA Science Inventory

The report describes an experimental investigation of the hydration process of spent bed material (with a calcium/sulfur ratio of 3) from an atmospheric fluidized bed combustor for maximum temperature, rate of temperature rise, and controllability of temperature rise with various...

257

Effects of the Particle Size and the Firing Atmosphere on Electrical Properties in PNN-PZT Thick Films  

Microsoft Academic Search

Pb(Ni \\/3Nb \\/3)O3?PbZrO3?PbTiO3 (PNN-PZT) thick films were screen-printed on platinized alumina substrates and fired at 800–1000°C under PbO atmosphere or in air. Effects of the starting particle size and the firing atmosphere on the microstructure and electrical properties of the thick films were investigated. Attrition milling produced smaller particle size than ball milling. Thick films prepared from attrition-milled powders showed

CHAE IL CHEON; JEONG SEOG KIM; TAE SONG KIM

2004-01-01

258

Characterisation of atmospheric deposited particles during a dust storm in urban areas of Eastern Australia.  

PubMed

The characteristics of dust particles deposited during the 2009 dust storm in the Gold Coast and Brisbane regions of Australia are discussed in this paper. The study outcomes provide important knowledge in relation to the potential impacts of dust storm related pollution on ecosystem health in the context that the frequency of dust storms is predicted to increase due to anthropogenic desert surface modifications and climate change impacts. The investigated dust storm contributed a large fraction of fine particles to the environment with an increased amount of total suspended solids, compared to dry deposition under ambient conditions. Although the dust storm passed over forested areas, the organic carbon content in the dust was relatively low. The primary metals present in the dust storm deposition were aluminium, iron and manganese, which are common soil minerals in Australia. The dust storm deposition did not contain significant loads of nickel, cadmium, copper and lead, which are commonly present in the urban environment. Furthermore, the comparison between the ambient and dust storm chromium and zinc loads suggested that these metals were contributed to the dust storm by local anthropogenic sources. The potential ecosystem health impacts of the 2009 dust storm include, increased fine solids deposition on ground surfaces resulting in an enhanced capacity to adsorb toxic pollutants as well as increased aluminium, iron and manganese loads. In contrast, the ecosystem health impacts related to organic carbon and other metals from dust storm atmospheric deposition are not considered to be significant. PMID:23712117

Gunawardena, Janaka; Ziyath, Abdul M; Bostrom, Thor E; Bekessy, Lambert K; Ayoko, Godwin A; Egodawatta, Prasanna; Goonetilleke, Ashantha

2013-09-01

259

Size distributions and characteristics of atmospheric inorganic particles by regional comparative study in Urban Osaka, Japan  

NASA Astrophysics Data System (ADS)

Size distributions and characteristics of atmospheric inorganic particles at two different monitoring sites were statistically compared in order to survey site-specific original sources of the particulate constituents. The average concentration difference of fine and coarse particles between the sites was, respectively, 1.4 and 4.7 ?g/m 3, and coarse particulate Fe, Mn, Zn and Pb were significantly high at the heavy traffic-flow site. Coarse particulate Zn and Pb form a closely related cluster group but Mn belongs to another independent group together with Fe. Comparative study for the Zn/Pb ratio possibly suggested that the regional differences of Zn and Pb were derived from road dust components and this might be caused essentially by tire wears and previous lead additives, respectively. On the contrary, the differences of coarse particulate Fe and Mn might be commonly and directly affected by industrial sources such as iron-steel factories close to the heavy traffic-flow site.

Funasaka, Kunihiro; Sakai, Mamoru; Shinya, Masanao; Miyazaki, Takeji; Kamiura, Toshikazu; Kaneco, Satoshi; Ohta, Kiyohisa; Fujita, Tadao

260

The origins of liner material in a shaped charge jet particle  

SciTech Connect

An improved high resolution LaGrangean tracer particle technique (using 198 identified tracer particles arranged as 99 particle pairs) has been used with an Eulerian Code (MESA 2D) to determine the locations in the jet to which liner material flows from various tagged locations in the liner, during the collapse, jet formation and jet stretching process. Time dependent strain and strain rate data has been computed, using the identified particle pairs of LaGrangean tracer particles as linear strain gauges. Sharp radial gradients of strain and strain rate have been found in the jet, with the liner material flowing nearest the jet axis being subjected to the highest strains and strain rates. Liner material from many extended initial locations along the liner can be traced by this method to jet locations corresponding to individual jet particles. The new quantitative data derived is illustrated with selected examples whose interpretation is discussed.

Zernow, L. [Zernow Technical Services, Inc., San Dimas, CA (United States); Chapyak, E.J.; Meyer, K.A. [Los Alamos National Lab., NM (United States); Zernow, R.H. [Applied Research Associates, Inc., Lakewood, CO (United States)

1992-02-01

261

The origins of liner material in a shaped charge jet particle  

SciTech Connect

An improved high resolution LaGrangean tracer particle technique (using 198 identified tracer particles arranged as 99 particle pairs) has been used with an Eulerian Code (MESA 2D) to determine the locations in the jet to which liner material flows from various tagged locations in the liner, during the collapse, jet formation and jet stretching process. Time dependent strain and strain rate data has been computed, using the identified particle pairs of LaGrangean tracer particles as linear strain gauges. Sharp radial gradients of strain and strain rate have been found in the jet, with the liner material flowing nearest the jet axis being subjected to the highest strains and strain rates. Liner material from many extended initial locations along the liner can be traced by this method to jet locations corresponding to individual jet particles. The new quantitative data derived is illustrated with selected examples whose interpretation is discussed.

Zernow, L. (Zernow Technical Services, Inc., San Dimas, CA (United States)); Chapyak, E.J.; Meyer, K.A. (Los Alamos National Lab., NM (United States)); Zernow, R.H. (Applied Research Associates, Inc., Lakewood, CO (United States))

1992-01-01

262

Autofluorescence of atmospheric bioaerosols - fluorescent biomolecules, biological standard particles and potential interferences  

NASA Astrophysics Data System (ADS)

Primary biological aerosol particles (PBAP) such as pollen, fungal spores, bacteria, biogenic polymers and debris from larger organisms are known to influence atmospheric chemistry and physics, the biosphere and public health. PBAP account for up to ~30% of fine and up to ~70% of coarse particulate matter in urban, rural and pristine environment and are released with estimated emission rates of up to ~1000 Tg/a [1]. Continuous measurements of the abundance, variability and diversity of PBAP have been difficult until recently, however. The application of on-line instruments able to detect autofluorescence from biological particles in real-time has been a promising development for the measurement of PBAP concentrations and fluxes in different environments [2,3]. The detected fluorescent biological aerosol particles (FBAP) can be regarded as a subset of PBAP, although the exact relationship between PBAP and FBAP is still being investigated. Autofluorescence of FBAP is usually a superposition of fluorescence from a mixture of individual fluorescent molecules (fluorophores). Numerous biogenic fluorophores such as amino acids (e.g., tryptophan, tyrosine), coenzymes (e.g., NAD(P)H, riboflavin) and biopolymers (e.g., cellulose) emit fluorescent light due to heterocyclic aromatic rings or conjugated double bonds within their molecular structures. The tryptophan emission peak is a common feature of most bioparticles because the amino acid is a constituent of many proteins and peptides. The influence of the coenzymes NAD(P)H and riboflavin on the autofluorescence of bacteria can be regarded as an indicator for bacterial metabolism and has been utilized to discriminate between viable and non-viable organisms [4]. However, very little information is available about other essential biofluorophores in fungal spores and pollen. In order to better understand the autofluorescence behavior of FBAP, we have used fluorescence spectroscopy and fluorescence microscopy to analyze standard bioparticles (pollen, fungal spores, and bacteria) as well as atmospherically relevant chemical substances. We found varying levels of fluorescent emission and significant differences in the spectral properties of major PBAP classes. The combination will support the quantitative interpretation of data obtained by real-time FBAP instrumentation [5]. [1] Elbert, W., Taylor, P. E., Andreae, M. O., & Pöschl, U. (2007). Atmos. Chem. Phys., 7, 4569-4588. [2] Huffman, J. A., Treutlein, B., & Pöschl, U. (2010). Atmos. Chem. Phys., 10, 3215-3233. [3] Pöschl, U., et al. (2010). Science, 329, 1513-1516. [4] Lakowicz, J., Principles of fluorescence spectroscopy, Plenum publishers, New York, 1999. [5] Pöhlker, C., Huffman, J. A., & Pöschl, U., (2012). Atmos. Meas. Tech., 5, 37-71.

Pöhlker, C.; Huffmann, J. A.; Pöschl, U.

2012-04-01

263

Light scattering at small angles by atmospheric irregular particles: modelling and laboratory measurements  

NASA Astrophysics Data System (ADS)

We investigated the behaviour of light scattering by particulates of various sizes (0.1 ?m to 100 ?m) at a small scattering angle. It was previously shown that for a small angle, the scattered intensities are weakly dependent upon the particulates' nature (Renard et al., 2010). Particles found in the atmosphere exhibit roughness that leads to large discrepancies with the classical Mie solution in terms of scattered intensities in the low angular set-up. This article focuses on building an effective theoretical tool to predict the behaviour of light scattering by real particulates at a small scattering angle. We expose both the classical Mie theory and an adaptation to the case of rough particulates with a fairly simple roughness parametrisation. An experimental device was built, corresponding to the angular set-up of interest (low scattering angle and therefore low angular aperture), and measurements are presented that confirm the theoretical results with a good agreement. It is found that the differences between the classical Mie solution and actual measurements, especially for large particulates, can be attributed to the roughness of particulates. It is also found that, in this low angular set-up, saturation of the scattered intensities occurs for relatively small values of the roughness parameter. This confirms the low variability in the scattered intensities for particulates of different kinds. A direct interest of this study is a broadening of the dynamic range of optical counters: using a small angle of aperture for measurements allows greater dynamics in terms of particle size, and thus enables a single device to observe a broad range of particle sizes whilst utilising the same electronics.

Lurton, T.; Renard, J.-B.; Vignelles, D.; Jeannot, M.; Akiki, R.; Mineau, J.-L.; Tonnelier, T.

2013-08-01

264

Application of the dissipative particle dynamics simulation method to materials  

Microsoft Academic Search

Dissipative particle dynamics (DPD) is an important simulation methodology with a broad range of applications to the simulation of complex fluids. In our group it has been used to study the phase behaviour and kinetics of order-disorder transitions in block copolymers [1], dynamics in polymer [2] and surfactant [3] solutions, and the microhydrodynamics of droplet removal from surfaces [4]. This

Janette Jones; Patrick Warren

2002-01-01

265

Use of an electron accelerator to produce nanopowders by evaporation of initial materials at atmospheric pressure  

NASA Astrophysics Data System (ADS)

High-purity nanodispersed powders with extraordinary properties that can be used in various technologies (electronics, catalysis, ceramics, modification of composite rheology, and so on) can be produced by evaporation of various initial materials at atmospheric pressure. In particular, the authors succeeded in producing nanodispersed powders of oxides [including silicon dioxide and oxide (SiO 2 and SiO) and magnesium (MgO), aluminum (Al 2 O 3), and cuprous (Cu 2 O) oxides], metals [including tantalum (Ta), molybdenum (Mo), aluminum (Al), silver (Ag), and some others] in various atmospheres, semiconductors [including silicon (Si)], nitrides [including aluminum (AlN) and titanium (TiN) nitrides], and other materials. It is important for the developed production process that the main component of the setup (an industrial accelerator) is capable of creating high temperatures for evaporation of any refractory materials. The production process has high efficiency and productivity (reaching several kilograms of oxides per hour).

Bardakhanov, S. P.; Korchagin, A. I.; Kuksanov, N. K.; Lavrukhin, A. V.; Salimov, R. A.; Fadeev, S. N.; Cherepkov, V. V.

2007-02-01

266

Connections between atmospheric sulphuric acid and new particle formation during QUEST III-IV campaigns in Heidelberg and Hyytiälä  

Microsoft Academic Search

This study investigates the connections between atmospheric sulphuric acid and new particle formation during QUEST III and BACCI\\/QUEST IV campaigns. The campaigns have been conducted in Heidelberg (2004) and Hyytiälä (2005), the first representing a polluted site surrounded by deciduous forest, and the second a rural site in a boreal forest environment. We have studied the role of sulphuric acid

I. Riipinen; S.-L. Sihto; M. Kulmala; F. Arnold; M. Dal Maso; W. Birmili; K. Saarnio; K. Teinilä; V.-M. Kerminen; A. Laaksonen; K. E. J. Lehtinen

2007-01-01

267

Connections between atmospheric sulphuric acid and new particle formation during QUEST III IV campaigns in Heidelberg and Hyytiälä  

Microsoft Academic Search

This study investigates the connections between atmospheric sulphuric acid and new particle formation during QUEST III and BACCI\\/QUEST IV campaigns. The campaigns have been conducted in Heidelberg (2004) and Hyytiälä (2005), the first representing a polluted site surrounded by deciduous forest, and the second a rural site in a boreal forest environment. We have studied the role of sulphuric acid

I. Riipinen; S.-L. Sihto; M. Kulmala; F. Arnold; M. Dal Maso; W. Birmili; K. Saarnio; K. Teinilä; V.-M. Kerminen; A. Laaksonen; K. E. J. Lehtinen

2006-01-01

268

VIABLE BACTERIAL AEROSOL PARTICLE SIZE DISTRIBUTIONS IN THE MIDSUMMER ATMOSPHERE AT AN ISOLATED LOCATION IN THE HIGH DESERT CHAPARRAL  

EPA Science Inventory

The viable bacterial particle size distribution in the atmosphere at the Hanford Nuclear Reservation, Richland, WA during two 1-week periods in June 1992, was observed at three intervals during the day (morning, midday and evening) and at three heights (2, 4, and 8 m) above groun...

269

The relationships between high latitude convection reversals and the energetic particle morphology observed by the Atmosphere Explorer  

NASA Technical Reports Server (NTRS)

Simultaneous measurements of the auroral zone particle precipitation and the ion convection velocity by Atmosphere Explorer show a consistent difference between the location of the poleward boundary of the auroral particle precipitation and the ion convection reversal. The difference of about 1.5 degrees of invariant latitude is such that some part of the antisunward convection lies wholly within the auroral particle precipitation region. The nature of the convection reversals within the precipitation region suggests that in this region the convection electric field is generated on closed field lines that connect in the magnetosphere to the low latitude boundary layer.

Heelis, R. A.; Winningham, J. D.; Hanson, W. B.; Burch, J. L.

1980-01-01

270

Chemical Imaging and Stable Isotope Analysis of Atmospheric Particles by NanoSIMS (Invited)  

NASA Astrophysics Data System (ADS)

Chemical imaging analysis of the internal distribution of chemical compounds by a combination of SEM-EDX, and NanoSIMS allows investigating the physico-chemical properties and isotopic composition of individual aerosol particles. Stable sulphur isotope analysis provides insight into the sources, sinks and oxidation pathways of SO2 in the environment. Oxidation by OH radicals, O3 and H2O2 enriches the heavier isotope in the product sulphate, whereas oxidation by transition metal ions (TMI), hypohalites and hypohalous acids depletes the heavier isotope in the product sulphate. The isotope fractionation during SO2 oxidation by stabilized Criegee Intermediate radicals is unknown. We studied the relationship between aerosol chemical composition and predominant sulphate formation pathways in continental clouds in Central Europe and during the wet season in the Amazon rain forest. Sulphate formation in continental clouds in Central Europe was studied during HCCT-2010, a lagrangian-type field experiment, during which an orographic cloud was used as a natural flow-through reactor to study in-cloud aerosol processing (Harris et al. 2013). Sulphur isotopic compositions in SO2 and H2SO4 gas and particulate sulphate were measured and changes in the sulphur isotope composition of SO2 between the upwind and downwind measurement sites were used to determine the dominant SO2 chemical removal process occurring in the cloud. Changes in the isotopic composition of particulate sulphate revealed that transition metal catalysis pathway was the dominant SO2 oxidation pathway. This reaction occurred primarily on coarse mineral dust particles. Thus, sulphate produced due to in-cloud SO2 oxidation is removed relatively quickly from the atmosphere and has a minor climatic effect. The aerosol samples from the Amazonian rainforest, a pristine tropical environment, were collected during the rainy season. The samples were found to be dominated by SOA particles in the fine mode and primary biological aerosol particles in the coarse mode (Pöhlker et al. 2012). We applied STXM-NEXAFS analysis, SEM-EDX analysis and NanoSIMS analysis to investigate the morphology, chemical composition and isotopic composition of aerosol samples. Biogenic salt particles emitted from active biota in the rainforest were found to be enriched in the heavier sulphur isotope, whereas particles with a high organic mass fraction modified by condensation of VOC oxidation products and/or cloud processing were significantly depleted in the heavier sulphur isotope compared to the seed particles. This indicates either a depleted gas phase source of sulphur dioxide contributed to the sulphate formation via the H2O2, O3 or OH oxidation pathway or an unaccounted reaction pathway which depletes the heavier isotope in the product sulphate contributes to the secondary sulphate formation in the pristine Amazon rainforest. Harris, E., et al., Science 340, 727-730, 2013 Pöhlker, C., Science 337, 1075-1078, 2012

Sinha, B.; Harris, E. J.; Pöhlker, C.; Wiedemann, K. T.; van Pinxteren, D.; Tilgner, A.; Fomba, K. W.; Schneider, J.; Roth, A.; Gnauk, T.; Fahlbusch, B.; Mertes, S.; Lee, T.; Collett, J. L.; Shiraiwa, M.; Gunthe, S. S.; Smith, M.; Artaxo, P. P.; Gilles, M.; Kilcoyne, A. L.; Moffet, R.; Weigand, M.; Martin, S. T.; Poeschl, U.; Andreae, M. O.; Hoppe, P.; Herrmann, H.; Borrmann, S.

2013-12-01

271

Application of the dissipative particle dynamics simulation method to materials  

NASA Astrophysics Data System (ADS)

Dissipative particle dynamics (DPD) is an important simulation methodology with a broad range of applications to the simulation of complex fluids. In our group it has been used to study the phase behaviour and kinetics of order-disorder transitions in block copolymers [1], dynamics in polymer [2] and surfactant [3] solutions, and the microhydrodynamics of droplet removal from surfaces [4]. This contribution will introduce the DPD method and illustrate its use with a variety of examples drawn from our work in this area. References : [1] R. D. Groot and T. J. Madden, Dynamic simulation of diblock copolymer microphase separation, J. Chem. Phys. 108, 8713 (1998); R. D. Groot, T. J. Madden and D. J. Tildesley, On the role of hydrodynamic interactions in block copolymer microphase separation, J. Chem. Phys. 110, 9739 (1999). [2] N. A. Spenley, Scaling laws for polymers in dissipative particle dynamics, Europhys. Lett. 49, 534 (2000). [3] S. Jury et al, Simulation of amphiphilic mesophases using dissipative particle dynamics, Phys. Chem. Chem. Phys. 1, 2051 (1999); P. Prinsen and P. B. Warren, Mesoscale simulations of surfactant dissolution and mesophase formation, in preparation. [4] J. L. Jones et al, Dynamics of a drop at a liquid / solid interface in simple shear fields: a mesoscopic simulation study., Faraday Disc. 112, 129 (1999).

Jones, Janette; Warren, Patrick

2002-03-01

272

A model for the abrasive wear of metallic matrix particle-reinforced materials  

Microsoft Academic Search

In the present paper a model for the abrasive wear of metallic matrix reinforced materials is presented. The model is based on a generalisation to multiphase materials of the Rabinowicz equation, by considering separately the contributions of the reinforcement particles and of the matrix to material loss. The predictions of the model are discussed and compared with experimental results obtained

R. Colaēo; R. Vilar

2003-01-01

273

Measurements of aerosol-cloud interactions, including on-line particle chemical composition, at the Jungfraujoch Global Atmospheric Watch Station  

NASA Astrophysics Data System (ADS)

The Global Atmospheric Watch research laboratory is located in the Sphinx building, 3580 m asl; 46.55oN, 7.98oE on the Jungfraujoch in the Swiss Alps. The site is exposed to a wide range of conditions and frequently samples long range transported lower free tropospheric air, and is exposed to cloudy conditions. The Paul Scherrer Institute have previously developed a dual inlet system that allows measurements of the total sub-micron aerosol population (dry residuals and interstitial particles) and interstitial particles alone to be made alternately every few minutes. During July 2002 an Aerodyne Aerosol Mass Spectrometer was coupled to the dual inlet and was used to sample the composition of both the total particle distribution and the interstitial fraction and hence derive the mass loadings of the dry droplet residuals. In out of cloud conditions the aerosol composition can be linked to air mass history and age of the air mass. Microphysical measurements include cloud droplet size distributions made using an FSSP and also a new phase Doppler anemometry system. A comparison between these probes will be made. Two different types of cloud droplet spectra were observed. In the first type a large number of cloud droplets were measured with a single, narrow drop size distribution and modal diameter of around 10 um. In the second type, a bimodal cloud droplet spectrum occurred with a smaller mode (by number) at around 20 um, in addition to the 10 um mode. The aerosol mass spectrometry shows that the composition of the residuals from the two spectrum types is very different, the former type being composed mainly of sulphate, the latter a combination of nitrate, sulphate and organic material. We have also shown that the organic material observed is highly oxidized. We argue that the bimodality arises as a result of mixing of cloud droplets below the site that have been activated separately: the larger a less numerous mode in the widespread strato-cumulus forming under low updraught conditions, the smaller more numerous mode forming during vigorous orographic lift from the valley below the mountain ridge.

Coe, H.; Allan, J. D.; Alfarra, M. R.; Williams, P. I.; Bower, K. N.; Gallagher, M. W.; Choularton, T. W.; Weingartner, E.; Corrigan, C.; Baltensperger, U.

2003-04-01

274

Surface Treatment of Polymers by Simultaneous Exposure to Vacuum UV and Nanometer-Sized Particles in Helium Atmosphere  

NASA Astrophysics Data System (ADS)

A new surface treatment for polymers in helium at atmospheric pressure for making bonds between surfaces and painting over polymer surfaces was demonstrated. In one-atmospheric helium gas, which was transparent for vacuum UV light at wavelengths between 60 and 80 nm, polymer surfaces were exposed simultaneously to vacuum UV (VUV) and ablated particles from the plasma on a carbon target irradiated with a high-intensity pulse YAG laser. Considering the breakdown threshold and VUV intensity, the optimum irradiation intensity of YAG laser was about 4 GW/cm2. The adhesive properties of polymer surfaces exposed to VUV and particles ablated by 4 GW/cm2 laser irradiation in one-atmospheric helium gas were improved. This result should expand new applications of polymers, and apply to almost all polymers scientifically and industrially.

Azuma, Hirozumi; Takeuchi, Akihiro; Kamiya, Nobuo; Ito, Tadashi; Narita, Takeshi; Tachi, Kazuyuki; Motohiro, Tomoyoshi

2006-03-01

275

Photochemistry of iron(III)-carboxylato complexes in aqueous atmospheric particles - Laboratory experiments and modeling studies  

NASA Astrophysics Data System (ADS)

Iron is always present in the atmosphere in concentrations from ~10-9 M (clouds, rain) up to ~10-3 M (fog, particles). Sources are mainly mineral dust emissions. Iron complexes are very good absorbers in the UV-VIS actinic region and therefore photo-chemically reactive. Iron complex photolysis leads to radical production and can initiate radical chain reactions, which is related to the oxidizing capacity of the atmosphere. These radical chain reactions are involved in the decomposition and transformation of a variety of chemical compounds in cloud droplets and deliquescent particles. Additionally, the photochemical reaction itself can be a degradation pathway for organic compounds with the ability to bind iron. Iron-complexes of atmospherically relevant coordination compounds like oxalate, malonate, succinate, glutarate, tartronate, gluconate, pyruvate and glyoxalate have been investigated in laboratory experiments. Iron speciation depends on the iron-ligand ratio and the pH. The most suitable experimental conditions were calculated with a speciation program (Visual Minteq). The solutions were prepared accordingly and transferred to a 1 cm quartz cuvette and flash-photolyzed with an excimer laser at wavelengths 308 or 351 nm. Photochemically produced Fe2+ has been measured by spectrometry at 510 nm as Fe(phenantroline)32+. Fe2+ overall effective quantum yields have been calculated with the concentration of photochemically produced Fe2+ and the measured energy of the excimer laser pulse. The laser pulse energy was measured with a pyroelectric sensor. For some iron-carboxylate systems the experimental parameters like the oxygen content of the solution, the initial Iron concentration and the incident laser energy were systematically altered to observe an effect on the overall quantum yield. The dependence of some quantum yields on these parameters allows in some cases an interpretation of the underlying photochemical reaction mechanism. Quantum yields of malonate, glutarate and gluconate complexes lie in the range of 0.02 < ? < 0.10, whereas succinate, tartronate, pyruvate and glyoxalate systems have values between 0.16 < ? < 1.26. All quantum yields include contributions from secondary thermal reactions. Furthermore, an attempt was made to differentiate between contributions of individual iron-oxalato complexes to the overall measured quantum yield. The formation and photolysis of the iron-carboxylate complexes and the subsequent reactions of the resulting compounds have been implemented in CAPRAM 3.0 (Chemical Aqueous Phase Radical Mechanism). Modeling studies were performed to investigate the effects of the expanded iron photochemistry on oxidant budgets, the iron redox-cycling and the processing of secondary organic acids in cloud droplets and deliquescent particles under different environmental conditions. The model studies have shown that, i.e. for pyruvic acid under urban conditions, the photolysis of the iron-pyruvate complex can contribute with about 40 % significantly to the overall degradation flux and represents thus an important loss pathway beside the radical oxidation pathways.

Weller, C.; Tilgner, A.; Herrmann, H.

2010-12-01

276

Autofluorescence of atmospheric bioaerosols - Biological standard particles and the influence of environmental conditions  

NASA Astrophysics Data System (ADS)

Primary biological aerosol particles (PBAP) such as pollen, fungal spores, bacteria, biogenic polymers and debris from larger organisms are known to influence atmospheric chemistry and physics, the biosphere and public health. PBAP can account for up to ~30% of fine and up to ~70% of coarse particulate matter in urban, rural and pristine environment and are released with estimated emission rates of up to ~1000 Tg/a [1]. Continuous measurements of the abundance, variability and diversity of PBAP have been difficult until recently, however. The application of on-line instruments able to detect autofluorescence from biological particles in real-time has been a promising development for the measurement of PBAP concentrations and fluxes in different environments [2,3]. The detected fluorescent biological aerosol particles (FBAP) can be regarded as a subset of PBAP, although the exact relationship between PBAP and FBAP is still being investigated. Autofluorescence of FBAP is usually a superposition of fluorescence from a mixture of individual fluorescent molecules (fluorophores). Numerous biogenic fluorophores such as amino acids (e.g., tryptophan, tyrosine), coenzymes (e.g., NAD(P)H, riboflavin) and biopolymers (e.g., cellulose) emit fluorescent light due to heterocyclic aromatic rings or conjugated double bonds within their molecular structures. The tryptophan emission peak is a common feature of most bioparticles because the amino acid is a constituent of many proteins and peptides. The influence of the coenzymes NAD(P)H and riboflavin on the autofluorescence of bacteria can be regarded as an indicator for bacterial metabolism and has been utilized to discriminate between viable and non-viable organisms [4]. However, very little information is available about other essential biofluorophores in fungal spores and pollen. In order to better understand the autofluorescence behavior of FBAP, we have used fluorescence spectroscopy and fluorescence microscopy to analyze standard bioparticles (pollen, fungal spores, and bacteria) as well as atmospherically relevant chemical substances. We addressed the sensitivity and selectivity of autofluorescence based online techniques. Moreover, we investigated the influence of environmental conditions, such as relative humidity and oxidizing agents in the atmosphere, on the autofluorescence signature of standard bioparticles. Our results will support the molecular understanding and quantitative interpretation of data obtained by real-time FBAP instrumentation [5,6]. [1] Elbert, W., Taylor, P. E., Andreae, M. O., & Pöschl, U. (2007). Atmos. Chem. Phys., 7, 4569-4588. [2] Huffman, J. A., Treutlein, B., & Pöschl, U. (2010). Atmos. Chem. Phys., 10, 3215-3233. [3] Pöschl, U., et al. (2010). Science, 329, 1513-1516. [4] Lakowicz, J., Principles of fluorescence spectroscopy, Plenum publishers, New York, 1999. [5] Pöhlker, C., Huffman, J. A., & Pöschl, U., (2012). Atmos. Meas. Tech., 5, 37-71. [6] Pöhlker, C., Huffman, J. A., Förster J.-D., & Pöschl, U., (2012) in preparation.

Pöhlker, Christopher; Huffman, J. Alex; Förster, Jan-David; Pöschl, Ulrich

2013-04-01

277

Atmospheric effects of energetic particle precipitation in the Arctic winter 1978-1979 revisited  

NASA Astrophysics Data System (ADS)

The Limb Infrared Monitor of the Stratosphere (LIMS) measured polar stratospheric enhancements of NO2 mixing ratios due to energetic particle precipitation (EPP) in the Arctic winter of 1978-1979. Recently reprocessed LIMS data are compared to more recent measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) to place the LIMS measurements in the context of current observations. The amount of NOx (NO + NO2) entering the stratosphere that has been created by EPP in the mesosphere and lower thermosphere (EPP-NOx) has been quantified for the 1978-1979 and 2002-2003 through 2008-2009 Arctic winters. The NO2 enhancements in the LIMS data are similar to those in MIPAS and ACE-FTS data in the Arctic winters of 2002-2003, 2004-2005, 2006-2007, and 2007-2008. The largest enhancement by far is in 2003-2004 (˜2.2 Gmol at 1500 K), which is attributed to a combination of elevated EPP and unusual dynamics that led to strong descent in the upper stratosphere/lower mesosphere in late winter. The enhancements in 2005-2006 and 2008-2009, during which large stratospheric NOx enhancements were caused by a dynamical situation similar to that in 2003-2004, are larger than in all the other years (except 2003-2004) at 3000 K. However, by 2000 K the enhancements in 2005-2006 (2008-2009) are on the same order of magnitude as (smaller than) all other years. These results highlight the importance of the timing of the descent in determining the potential of EPP-NOx for reaching the middle stratosphere.

Holt, L. A.; Randall, C. E.; Harvey, V. L.; Remsberg, E. E.; Stiller, G. P.; Funke, B.; Bernath, P. F.; Walker, K. A.

2012-03-01

278

Atmospheric Effects of Energetic Particle Precipitation in the Arctic Winter 1978-1979 Revisited  

NASA Technical Reports Server (NTRS)

The Limb Infrared Monitor of the Stratosphere (LIMS) measured polar stratospheric enhancements of NO2 mixing ratios due to energetic particle precipitation (EPP) in the Arctic winter of 1978-1979. Recently reprocessed LIMS data are compared to more recent measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) to place the LIMS measurements in the context of current observations. The amount of NOx (NO + NO2) entering the stratosphere that has been created by EPP in the mesosphere and lower thermosphere (EPP-NOx) has been quantified for the 1978-1979 and 2002-2003 through 2008-2009 Arctic winters. The NO2 enhancements in the LIMS data are similar to those in MIPAS and ACE-FTS data in the Arctic winters of 2002-2003, 2004-2005, 2006-2007, and 2007-2008. The largest enhancement by far is in 2003-2004 (approximately 2.2 Gmol at 1500 K), which is attributed to a combination of elevated EPP and unusual dynamics that led to strong descent in the upper stratosphere/lower mesosphere in late winter. The enhancements in 2005-2006 and 2008-2009, during which large stratospheric NOx enhancements were caused by a dynamical situation similar to that in 2003 2004, are larger than in all the other years (except 2003-2004) at 3000 K. However, by 2000 K the enhancements in 2005-2006 (2008-2009) are on the same order of magnitude as (smaller than) all other years. These results highlight the importance of the timing of the descent in determining the potential of EPP-NOx for reaching the middle stratosphere.

Holt, L. A.; Randall, C. E.; Harvey, V. L.; Remsberg, E. E.; Stiller, G. P.; Funke, B.; Bernath, P. F.; Walker, K. A.

2012-01-01

279

A model of the atmospheric metal deposition by cosmic dust particles  

NASA Astrophysics Data System (ADS)

We have developed a model of the deposition of meteoric metals in Earth's atmosphere. The model takes as input the total mass influx of material to the Earth and calculates the deposition rate at all altitudes through solution of the drag and subliminal equations in a Monte Carlo-type computation. The diffusion equation is then solved to give steady state concentration of complexes of specific metal species and kinetics are added to calculate the concentration of individual complexes. Concentrating on sodium, we calculate the Na(D) nightglow predicted by the model, and by introduction of seasonal variations in lower tropospheric ozone based on experimental results, we are able to duplicate the seasonal variation of mid-latitude nightglow data.

McNeil, W. J.

1993-11-01

280

Laboratory and Field Testing of an Automated Atmospheric Particle-Bound Reactive Oxygen Species Sampling-Analysis System  

PubMed Central

In this study, various laboratory and field tests were performed to develop an effective automated particle-bound ROS sampling-analysis system. The system uses 2? 7?-dichlorofluorescin (DCFH) fluorescence method as a nonspecific, general indicator of the particle-bound ROS. A sharp-cut cyclone and a particle-into-liquid sampler (PILS) were used to collect PM2.5 atmospheric particles into slurry produced by a DCFH-HRP solution. The laboratory results show that the DCFH and H2O2 standard solutions could be kept at room temperature for at least three and eight days, respectively. The field test in Rochester, NY, shows that the average ROS concentration was 8.3 ± 2.2 nmol of equivalent H2O2?m?3 of air. The ROS concentrations were observed to be greater after foggy conditions. This study demonstrates the first practical automated sampling-analysis system to measure this ambient particle component. PMID:21577270

Wang, Yungang; Hopke, Philip K.; Sun, Liping; Chalupa, David C.; Utell, Mark J.

2011-01-01

281

Angular particle impingement studies of thermoplastic materials at normal incidence  

NASA Technical Reports Server (NTRS)

Scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluorethylene (PTFE), and ultra-high-molecular-weight polyethylene (UHMWPE). Erosion was caused by a jet of angular microparticles of crushed glass at normal incidence. Material built up above the original surface on all of the materials. As erosion progressed, this buildup disappeared. UHMWPE was the most resistant material and PMMA the least. The most favorable properties for high erosion resistance were high values of ultimate elongation, maximum service temperature, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibited incubation, acceleration, and steady-state periods. PMMA also exhibited a deceleration period, and an incubation period with deposition was observed for UHMWPE.

Rao, P. V.; Buckley, D. H.

1985-01-01

282

Morphological structure of atmospheric aerosols on the basis of laboratory studies of single levitated H2SO4\\/NH3\\/H2O aerosol particles  

Microsoft Academic Search

Atmospheric aerosols are of high interest due to their radiative properties, their possible role as CCNs and heterogeneous chemical processes on their surfaces. However, heterogeneous reactions on solid aerosol surfaces or ice surfaces are not well understood. In general heterogeneous chemistry on solid atmospheric particles can be influenced by liquid films on these particles. Thereby diffusion kinetics and solubility are

C. A. Colberg; U. K. Krieger; Th. Peter

2003-01-01

283

Waveguides in three-dimensional photonic bandgap materials for particle-accelerator on a  

E-print Network

Waveguides in three-dimensional photonic bandgap materials for particle-accelerator on a chip, Nano Center, 348 Via Pueblo Mall, Stanford, California 94305, USA 3 SLAC National Accelerator@physics.anu.edu.au Abstract: The quest for less costly and more compact high-energy particle accelerators

Byer, Robert L.

284

Effects of cement particle size distribution on performance properties of Portland cement-based materials  

Microsoft Academic Search

The original size, spatial distribution, and composition of Portland cement particles have a large influence on hydration kinetics, microstructure development, and ultimate properties of cement-based materials. In this paper, the effects of cement particle size distribution on a variety of performance properties are explored via computer simulation and a few experimental studies. Properties examined include setting time, heat release, capillary

Dale P. Bentz; Edward J. Garboczi; Claus J. Haecker; Ole M. Jensen

1999-01-01

285

1 INTRODUCTION Asphalt mixtures are composite materials that consist of solid particles, viscous binder/fluid  

E-print Network

1 INTRODUCTION Asphalt mixtures are composite materials that consist of solid particles, viscous between three different length scales, i.e. micro-, meso- and macro-scale. The interaction between the mortar (composition Modeling of Asphalt and experiments with a discrete particles method T.J. Ormel & V

Luding, Stefan

286

High-loading effect of surface-modified inorganic particles in polymer materials  

Microsoft Academic Search

Recently fine-particle technology has been extending its application not only to existing multiphase metals, paint and coatings, but also to other wider industrial fields (such as polymers, ceramics, etc.). In the polymer industries, inorganic particles (mica, talc, calcium carbonate, etc.) are combined to polymer materials in order to improve the stiffness and thermal stability, but the lack of affinity at

Kazuta Mitsuishi; Tatsumi Yabuki; Soji Kodama; Hitoshi Kawasaki

1989-01-01

287

Thermoelectric figure of merit of a material consisting of semiconductor or metal particles  

SciTech Connect

It is found that the dimensionless thermoelectric figure of merit of a material consisting of a large number of ball-shaped semiconductor or metal particles can be much more than unity. The introduction of an insulator into the space between the particles is shown to sharply increase the power of the converter of heat energy into electric current energy.

Kharlamov, V. F., E-mail: kharl@ostu.ru [Orel State Technical University (Russian Federation)

2013-07-15

288

Materials with a desired refraction coefficient can be made by embedding small particles  

E-print Network

A method is proposed to create materials with a desired refraction coefficient, possibly negative one. The method consists of embedding into a given material small particles. Given $n_0(x)$, the refraction coefficient of the original material in a bounded domain $D \\subset \\R^3$, and a desired refraction coefficient $n(x)$, one calculates the number $N(x)$ of small particles, to be embedded in $D$ around a point $x \\in D$ per unit volume of $D$, in order that the resulting new material has refraction coefficient $n(x)$.

A. G. Ramm

2007-06-15

289

Modeling of in situ ultrafine atmospheric particle formation in the eastern United States  

NASA Astrophysics Data System (ADS)

The creation of new atmospheric particles from in situ nucleation influences climate through cloud-aerosol interactions and may negatively impact human health. Although recent observations show that nucleation is widespread in the eastern United States, the corresponding pathways remain uncertain. Combining extensive field measurements in Pittsburgh, Pennsylvania, with an aerosol dynamics and chemistry model assuming ternary NH3-H2SO4-H2O nuclei formation, we show excellent model-measurement agreement and predictive capability. The ternary NH3-H2SO4-H2O nucleation model is successful in predicting the presence or lack of nucleation on 19 out of 19 days with complete data sets in July 2001 and on 25 out of 29 days in January 2002. Reductions of ammonia emissions are predicted to decrease the frequency of nucleation events during both summer and winter, with a more dramatic effect during the summer. The response to changes in emissions of sulfur dioxide during the summer is counterintuitive. Reductions of sulfur dioxide and the resulting sulfate by up to 40% actually increase the frequency of the summer nucleation events. Modeling predicts the opposite effect in winter, with reductions of sulfur dioxide leading to fewer nucleation events.

Gaydos, Timothy M.; Stanier, Charles O.; Pandis, Spyros N.

2005-04-01

290

Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles.  

PubMed

Measurements of submicron particles by Fourier transform infrared spectroscopy in 14 campaigns in North America, Asia, South America, and Europe were used to identify characteristic organic functional group compositions of fuel combustion, terrestrial vegetation, and ocean bubble bursting sources, each of which often accounts for more than a third of organic mass (OM), and some of which is secondary organic aerosol (SOA) from gas-phase precursors. The majority of the OM consists of alkane, carboxylic acid, hydroxyl, and carbonyl groups. The organic functional groups formed from combustion and vegetation emissions are similar to the secondary products identified in chamber studies. The near absence of carbonyl groups in the observed SOA associated with combustion is consistent with alkane rather than aromatic precursors, and the absence of organonitrate groups can be explained by their hydrolysis in humid ambient conditions. The remote forest observations have ratios of carboxylic acid, organic hydroxyl, and nonacid carbonyl groups similar to those observed for isoprene and monoterpene chamber studies, but in biogenic aerosols transported downwind of urban areas the formation of esters replaces the acid and hydroxyl groups and leaves only nonacid carbonyl groups. The carbonyl groups in SOA associated with vegetation emissions provides striking evidence for the mechanism of esterification as the pathway for possible oligomerization reactions in the atmosphere. Forest fires include biogenic emissions that produce SOA with organic components similar to isoprene and monoterpene chamber studies, also resulting in nonacid carbonyl groups in SOA. PMID:21317360

Russell, Lynn M; Bahadur, Ranjit; Ziemann, Paul J

2011-03-01

291

Acidic reaction products of mono- and sesquiterpenes in atmospheric fine particles in a boreal forest  

NASA Astrophysics Data System (ADS)

Biogenic acids were measured from PM2.5 aerosols at SMEAR II station (Station For Measuring Forest Ecosystem-Atmosphere Relations) in Finland from June 2010 until October 2011. The measured organic acids were pinic, pinonic, caric, limonic and caryophyllinic acids from oxidation of ?-pinene, ?-pinene, limonene, ?3-carene and ?-caryophyllene. Due to lack of authentic standards caric, limonic and caryophyllinic acids were synthesized at the Laboratory of Organic Chemistry, University of Helsinki. The highest terpenoic acid concentrations were measured during summer concomitant with the precursor mono- and sesquiterpenes. Of the acids ?-caryophyllinic acid had highest concentrations in summer, but during other times of the year pinonic acid was the most abundant. The ?-caryophyllinic acid contribution was higher than expected on the basis of emission calculations of precursor compounds and yields in oxidation experiments in smog chambers implicating that ?-caryophyllene emissions or ?-caryophyllinic acid yields are underestimated. Concentration ratios between terpenoic acids and their precursor were clearly lower in summer than in winter indicating stronger partitioning to the aerosol phase during cold winter season. The ?-caryophyllinic and caric acids were correlated with the accumulation mode particle number concentrations.

Vestenius, M.; Hellén, H.; Levula, J.; Kuronen, P.; Helminen, K. J.; Nieminen, T.; Kulmala, M.; Hakola, H.

2014-01-01

292

Source apportionment of fine atmospheric particles in Marseille: a one year study  

NASA Astrophysics Data System (ADS)

Marseille is the second most populated city in France with more than one million inhabitants. With traffic of about 88 million tons (Mt) in 2011, Marseille is also the most important port of the Mediterranean Sea, and also in the vicinity of the large petrochemical and industrial area of Fos-Berre, located 40 km northwest of the metropolitan area. For these reasons, Marseille area represents a challenging case study for source apportionment exercises, combining an active photochemistry and multiple emission sources, including fugitive emissions from industrial sources and shipping. In order to develop strategies for controlling and reducing air pollution, there is a need of source apportionment studies in order to better understand the influence of the different sources of aerosol particles. Within the framework of the EU-MED APICE project (Common Mediterranean strategy and local practical Actions for the mitigation of Port, Industries and Cities Emissions ; www.apice-project.eu), sources of atmospheric particles in Marseille were evaluated for a one-year period by a long monitoring campaign conducted at two sampling sites. PM2.5 were collected continuously on a 24h-basis in an urban background site from July 2011 to July 2012 and on a 48h-basis for the Eastern dock from November 2011 to July 2012 using high volume samplers (DA80) operating at a flow rate of 30m3 h-1. In this work, two different source apportionment models were used to explain the chemical observations, and to investigate the sources of organic aerosol in Marseille. Two sources apportionment models were used and combined to quantify the contribution of the main aerosol particles sources: CMB (Chemical Mass Balance) and PMF (Positive Matrix Factorization). Both models were used with organic molecular markers and metals/trace elements. Both approaches are able to identify major sources, the combination of these two commonly used receptor models offer interesting perspective, especially when the factors derived from PMF analysis are injected as source profiles in CMB calculation.

Marchand, Nicolas; Salameh, Dalia; Detournay, Anais; Wortham, Henri; Jaffrezo, Jean-Luc; Piot, Christine; Armengaud, Alexandre; Piga, Damien; Parra, Michael; Deveze, Magali

2013-04-01

293

Particle number size distribution in the eastern Mediterranean: Formation and growth rates of ultrafine airborne atmospheric particles  

NASA Astrophysics Data System (ADS)

Particle number concentration was measured between June 2009 and June 2010 at Akrotiri research station in a rural/suburban region of western Crete (Greece). Overall, the available data covered 157 days during the aforementioned period of measurements. The objectives were to study the number size distribution characteristics of ambient aerosols and furthermore to identify new particle formation events and to evaluate particle formation rates and growth rates of the newborn particles. Aerosol particles with mobility diameters between 10 and 1100 nm were measured using a Scanning Mobility Particle Sizer (SMPS) system. Measurements were performed at ambient relative humidities. The median total particle number concentration was 525 #/cm3 whereas the number concentration ranged between 130 #/cm3 and 9597 #/cm3. The average percentage of particles with diameters between 10 nm and 100 nm (N10-100) to total particles was 53% during summer and spring, but reached 80% during winter. Maximum average contribution of nano-particles (10 nm < Dp < 50 nm) to total particles was recorded also in winter and was attributed partly to the effect of local heating. Furthermore, back trajectories (HYSPLIT model) showed that different air mass origins are linked to different levels of particle number concentrations, with higher values associated with air masses passing from polluted areas before reaching the Akrotiri station. Modal analysis of the measured size distribution data revealed a strong nucleation mode during winter (15-25 nm), which can be correlated with emissions from local sources (domestic heating). The nucleation mode was observed also during the spring campaigns and was partly linked to new particle formation events. On the contrary, an accumulation mode (80-120 nm) prevailed in the measurements during summer campaigns, when the station area was influenced by polluted air masses arriving mainly from Eastern Europe. In total, 13 new particle formation events were recorded during the 157 days of measurements. Nucleation events were associated with low values of N100 particle number concentration and reduced coagulation sinks. Mean growth and formation rates were calculated and showed values equal to 6 nm hr-1 and 13 cm-3 s-1, respectively.

Kopanakis, I.; Chatoutsidou, S. E.; Torseth, K.; Glytsos, T.; Lazaridis, M.

2013-10-01

294

Atmospheric Aerosols Aging Involving Organic Compounds and Impacts on Particle Properties  

E-print Network

where toluene is oxidized by OH radicals. The variations in soot particle properties are simultaneously monitored, including particle size, mass, organic mass faction, hygroscopicity, and optical properties. The changes in particle properties are found...

Qiu, Chong

2013-02-01

295

Formation of nanostructured materials via coalescence of amphiphilic hollow particles.  

PubMed

A new, simplified route to amphiphilic core-shell nanotubes, microfibers, and microrods has been developed that does not involve the traditional utilization of well-defined block copolymers. Thus, amphiphilic graft copolymers (PEI-g-PMMA) are prepared by an aqueous free radical polymerization that self-assemble in situ to form uniform core-shell nanoparticles. The hydrophobic homopolymer (PMMA) that is also formed is incorporated in the cores. Slight cross-linking of the shells followed by extraction of the homopolymer results in hollow nanoparticles that coalesce to form nanotubes. When the shells are not cross-linked, the hollow particles coalesce to form microrods and microfibers. The sizes and shapes of the micromaterials can be controlled by varying the experimental conditions. PMID:16478143

Sunintaboon, Panya; Ho, Kin Man; Li, Pei; Cheng, Stephen Z D; Harris, Frank W

2006-02-22

296

Wood dust particle and mass concentrations and filtration efficiency in sanding of wood materials.  

PubMed

The importance of fine particles has become apparent as the knowledge of their effects on health has increased. Fine particle concentrations have been published for outside air, plasma arc cutting, welding, and grinding, but little data exists for the woodworking industry. Sanding was evaluated as the producer of the woodworking industry's finest particles, and was selected as the target study. The number of dust particles in different particle size classes and the mass concentrations were measured in the following environments: workplace air during sanding in plywood production and in the inlet and return air; in the dust emission chamber; and in filter testing. The numbers of fine particles were low, less than 10(4) particles/cm(3) (10(7) particles/L). They were much lower than typical number concentrations near 10(6) particles/cm(3) measured in plasma arc cutting, grinding, and welding. Ultrafine particles in the size class less than 100 nm were found during sanding of MDF (medium density fiberboard) sheets. When the cleaned air is returned to the working areas, the dust content in extraction systems must be monitored continuously. One way to monitor the dust content in the return air is to use an after-filter and measure pressure drop across the filter to indicate leaks in the air-cleaning system. The best after-filtration materials provided a clear increase in pressure drop across the filter in the loading of the filter. The best after-filtration materials proved to be quite effective also for fine particles. The best mass removal efficiencies for fine particles around 0.3 mum were over 80% for some filter materials loaded with sanding wood dust. PMID:19065389

Welling, Irma; Lehtimäki, Matti; Rautio, Sari; Lähde, Tero; Enbom, Seppo; Hynynen, Pasi; Hämeri, Kaarle

2009-02-01

297

Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the lowermost stratosphere  

NASA Astrophysics Data System (ADS)

With a lidar system that was installed in Lindenberg/Germany, we observed in June 2003 an extended aerosol layer at 13km altitude in the lowermost stratosphere. This layer created an inelastic backscatter signal that we detected with a water vapour Raman channel, but that was not produced by Raman scattering. Also, we find evidence for inelastic scattering from a smoke plume from a forest fire that we observed in the troposphere. We interpret the unexpected properties of these aerosols as fluorescence induced by the laser beam at organic components of the aerosol particles. Fluorescence from ambient aerosol had not yet been considered detectable by lidar systems. However, organic compounds such as polycyclic aromatic hydrocarbons sticking to the aerosol particles, or bioaerosol such as bacteria, spores or pollen fluoresce when excited with UV-radiation in a way that is detectable by our lidar system. Therefore, we conclude that fluorescence from organic material released by biomass burning creates, inelastic backscatter signals that we measured with our instrument and thus demonstrate a new and powerful way to characterize aerosols by a remote sensing technique. The stratospheric aerosol layer that we have observed in Lindenberg for three consecutive days is likely to be a remnant from Siberian forest fire plumes lifted across the tropopause and transported around the globe.

Immler, F.; Engelbart, D.; Schrems, O.

2005-02-01

298

Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the stratosphere  

NASA Astrophysics Data System (ADS)

With a lidar system that was installed in Lindenberg/Germany, we observed in June 2003, an extended aerosol layer at 13 km altitude in the lowermost stratosphere. This layer created an inelastic backscatter signal which we interpret as laser induced fluorescence from aerosol particles. Also, we find evidence for inelastic scattering in a smoke plume from a forest fire that we observed in the troposphere. Fluorescence from ambient aerosol had not yet been considered detectable by lidar. However, organic compounds such as polycyclic aromatic hydrocarbons sticking to the aerosol particles, or bioaerosol such as bacteria, spores or pollen fluoresce when excited with UV-radiation in a way that is detectable by our lidar system. Therefore, we conclude that fluorescence from organic material released by biomass burning creates the inelastic backscatter signal that we measured with our instrument and thus demonstrate a new and powerful way to characterize aerosols by a remote sensing technique. The stratospheric aerosol layer that we have observed in Lindenberg for three consecutive days is likely to be a remnant from Siberian forest fire plumes lifted across the tropopause and transported around the globe.

Immler, F.; Engelbart, D.; Schrems, O.

2004-09-01

299

Micromechanics-based elastic model for functionally graded materials with particle interactions  

SciTech Connect

A micromechanics-based elastic model is developed for two-phase functionally graded materials with locally pair-wise interactions between particles. While the effective material properties change gradually along the gradation direction, there exist two microstructurally distinct zones: particle-matrix zone and transition zone. In the particle-matrix zone, pair-wise interactions between particles are employed using a modified Green's function method. By integrating the interactions from all other particles over the representative volume element, the homogenized elastic fields are obtained. The effective stiffness distribution over the gradation direction is further derived. In the transition zone, a transition function is constructed to make the homogenized elastic fields continuous and differentiable in the gradation direction. The model prediction is compared with other models and experimental data to demonstrate the capability of the proposed method.

Yin, H.M.; Sun, L.Z.; Paulino, G.H

2004-07-12

300

Particle Accelerator Applications: Ion and Electron Irradiation in Materials Science, Biology and Medicine  

SciTech Connect

Although the developments of particle accelerators are devoted to basic study of matter constituents, since the beginning these machines have been applied with different purposes in many areas also. Today particle accelerators are essential instruments for science and technology. This work presents an overview of the main application for direct particle irradiation with accelerator in material science, biology and medicine. They are used for material synthesis by ion implantation and charged particle irradiation; to make coatings and micromachining; to characterize broad kind of samples by ion beam analysis techniques; as mass spectrometers for atomic isotopes determination. In biomedicine the accelerators are applied for the study of effects by charged particles on cells. In medicine the radiotherapy by electron irradiation is widely used, while hadrontherapy is still under development. Also, they are necessary for short life radioisotopes production required in radiodiagnostic.

Rodriguez-Fernandez, Luis [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364, Mexico D.F., 01000 (Mexico)

2010-09-10

301

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials  

NASA Technical Reports Server (NTRS)

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrate and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analogs include hydration features due to structural OH, bound H2O and adsorbed H2O. The spectal character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration features near 1.9 micrometers, 2.2 micrometers, 2.7 micrometers, 3 micrometers, and 6 micrometers are reported here in spetra measured under Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-micrometer band depth is 8-17%; this band is much stonger under moist conditions. Under Marslike atmospheric conditions the 1.9-micrometer feature is broad and barely discernible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparable spectra of the ferric sulfate-bearing montmorillonite the 1.9-micrometer feature is also broad, but stronger (6% band depth). In the low atmospheric pressure and temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3- micrometer band is weaker in spectra of each of the analogs when measured under Marslike conditions, the 3-micromter band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil. The structural OH features observed in these materials at 2.2-2.3 micrometers and 2.27 micrometers remain largely unaffected by the environmental conditions. A shift in the Christiansen feature towards shorter wavelengths has also been observed with decreasing atmospheric pressure and temperature in the midinfrared spectra of these samples.

Bishop, Janice L.; Pieters, Carle M.

1995-01-01

302

Phase inversion of particle-stabilized materials from foams to dry water  

NASA Astrophysics Data System (ADS)

Small particles attached to liquid surfaces arise in many products and processes, including crude-oil emulsions and food foams and in flotation, and there is a revival of interest in studying their behaviour. Colloidal particles of suitable wettability adsorb strongly to liquid-liquid and liquid-vapour interfaces, and can be sole stabilizers of emulsions and foams, respectively. New materials, including colloidosomes, anisotropic particles and porous solids, have been prepared by assembling particles at such interfaces. Phase inversion of particle-stabilized emulsions from oil in water to water in oil can be achieved either by variation of the particle hydrophobicity (transitional) or by variation of the oil/water ratio (catastrophic). Here we describe the phase inversion of particle-stabilized air-water systems, from air-in-water foams to water-in-air powders and vice versa. This inversion can be driven either by a progressive change in silica-particle hydrophobicity at constant air/water ratio or by changing the air/water ratio at fixed particle wettability, and has not been observed in the corresponding systems stabilized by surfactants. The simplicity of the work is that this novel inversion is achieved in a single system. The resultant materials in which either air or water become encapsulated have potential applications in the food, pharmaceutical and cosmetics industries.

Binks, Bernard P.; Murakami, Ryo

2006-11-01

303

Interactions of mineral dust with pollution and clouds: An individual-particle TEM study of atmospheric aerosol from Saudi Arabia  

NASA Astrophysics Data System (ADS)

Aerosol particles from desert dust interact with clouds and influence climate on regional and global scales. The Riyadh (Saudi Arabia) aerosol campaign was initiated to study the effects of dust particles on cloud droplet nucleation and cloud properties. Here we report the results of individual-particle studies of samples that were collected from an aircraft in April 2007. We used analytical transmission electron microscopy, including energy-dispersive X-ray spectrometry, electron diffraction, and imaging techniques for the morphological, chemical, and structural characterization of the particles. Dust storms and regional background conditions were encountered during four days of sampling. Under dusty conditions, the coarse (supermicrometer) fraction resembles freshly crushed rock. The particles are almost exclusively mineral dust grains and include common rock-forming minerals, among which clay minerals, particularly smectites, are most abundant. Unaltered calcite grains also occur, indicating no significant atmospheric processing. The particles have no visible coatings but some contain traces of sulfur. The fine (submicrometer) fraction is dominated by particles of anthropogenic origin, primarily ammonium sulfate (with variable organic coating and some with soot inclusions) and combustion-derived particles (mostly soot). In addition, submicrometer, iron-bearing clay particles also occur, many of which are internally mixed with ammonium sulfate, soot, or both. We studied the relationships between the properties of the aerosol and the droplet microphysics of cumulus clouds that formed above the aerosol layer. Under dusty conditions, when a large concentration of coarse-fraction mineral particles was in the aerosol, cloud drop concentrations were lower and droplet diameters larger than under regional background conditions, when the aerosol was dominated by submicrometer sulfate particles.

Pósfai, Mihįly; Axisa, Duncan; Tompa, Éva; Freney, Evelyn; Bruintjes, Roelof; Buseck, Peter R.

2013-03-01

304

Acoustical properties of materials made of vegetable particles with several scales of porosity  

Microsoft Academic Search

This article is devoted to the acoustical properties of hemp concrete, a “green” building material. In the study, hemp concretes made of different binders and different kinds of particles were characterised, and then modeled using equivalent-fluid models. Further, it is shown that the sound absorption of these materials can be controlled and significantly enhanced by means of suitable constituents and

P. Glé; E. Gourdon; L. Arnaud

2011-01-01

305

Analysis results of micron-sized particles captured by space material exposure experiment  

NASA Astrophysics Data System (ADS)

Space material exposure experiments were performed on the International Space Station (ISS) using the Micro-Particles Capturer and the Space Environment Exposure Device (MPAC&SEED) developed by the Japan Aerospace Exploration Agency (JAXA). MPAC is a passive experiment designed to evaluate the dust (micrometeoroid and space debris) environment and to capture particle residues for subsequent chemical analysis. We found many unexpected micron-sized particles that did not make impact with hypervelocity. The diameter of these particles is in the order of micrometers. It is difficult to analyze these particles because they are too small to handle from aerogels. Also, their colorless and transparent nature prevents us from handling them after extraction. In final paper, I present the analysis results of this micron-sized particles

Kimoto, Yugo

306

Large area nuclear particle detectors using ET materials, phase 2  

NASA Technical Reports Server (NTRS)

This report presents work done under a Phase 2 SBIR contract for demonstrating large area detector planes utilizing Quantex electron trapping materials as a film medium for storing high-energy nuclide impingement information. The detector planes utilize energy dissipated by passage of the high-energy nuclides to produce localized populations of electrons stored in traps. Readout of the localized trapped electron populations is effected by scanning the ET plane with near-infrared, which frees the trapped electrons and results in optical emission at visible wavelengths. The effort involved both optimizing fabrication technology for the detector planes and developing a readout system capable of high spatial resolution for displaying the recorded nuclide passage tracks.

Wrigley, Charles Y.; Storti, George M.; Walter, Lee; Mathews, Scott

1990-01-01

307

Acidic reaction products of monoterpenes and sesquiterpenes in atmospheric fine particles in a boreal forest  

NASA Astrophysics Data System (ADS)

Biogenic acids were measured in aerosols at the SMEAR II (Station for Measuring Forest Ecosystem-Atmosphere Relations II) station in Finland from June 2010 until October 2011. The analysed organic acids were pinic, pinonic, caric, limonic and caryophyllinic acids from oxidation of ?-pinene, ?-pinene, limonene, ?3-carene and ?-caryophyllene, respectively. Due to a lack of authentic standards, the caric, limonic and caryophyllinic acids were synthesised for this study. The mean, median, maximum and minimum concentrations (ng m-3) were as follows: limonic acid (1.26, 0.80, 16.5, below detection limit (< LOD)), pinic acid (5.53, 3.25, 31.4, 0.15), pinonic acid (9.87, 5.07, 80.1, < LOD), caric acid (5.52, 3.58, 49.8, < LOD), and caryophyllinic acid (7.87, 6.07, 86.1, < LOD). The highest terpenoic acid concentrations were measured during the summer. Of the acids, ?-caryophyllinic acid showed the highest concentrations in summer, but during other times of the year pinonic acid was the most abundant. The ?-caryophyllinic acid contribution was higher than expected, based on the emission calculations of the precursor compounds and yields from oxidation experiments in smog chambers, implying that the ?-caryophyllene emissions or ?-caryophyllinic acid yields were underestimated. The concentration ratios between terpenoic acids and their precursors were clearly lower in summer than in winter, indicating stronger partitioning to the aerosol phase during the cold winter season. The ?-caryophyllinic and caric acids were weakly correlated with the accumulation-mode particle number concentrations.

Vestenius, M.; Hellén, H.; Levula, J.; Kuronen, P.; Helminen, K. J.; Nieminen, T.; Kulmala, M.; Hakola, H.

2014-08-01

308

The Exploration Atmospheres Working Group's Report on Space Radiation Shielding Materials  

NASA Technical Reports Server (NTRS)

This part of Exploration Atmospheres Working Group analyses focuses on the potential use of nonmetallic composites as the interior walls and structural elements exposed to the atmosphere of the spacecraft or habitat. The primary drive to consider nonmetallic, polymer-based composites as an alternative to aluminum structure is due to their superior radiation shielding properties. But as is shown in this analysis, these composites can also be made to combine superior mechanical properties with superior shielding properties. In addition, these composites can be made safe; i.e., with regard to flammability and toxicity, as well as "smart"; i.e., embedded with sensors for the continuous monitoring of material health and conditions. The analysis main conclusions are that (1) smart polymer-based composites are an enabling technology for safe and reliable exploration missions, and (2) an adaptive, synergetic systems approach is required to meet the missions requirements from structure, properties, and processes to crew health and protection for exploration missions.

Barghouty, A. F.; Thibeault, S. A.

2006-01-01

309

Crystallization of atmospheric sulfate-nitrate-ammonium particles Scot T. Martin, Julie C. Schlenker, Adam Malinowski, and Hui-Ming Hung  

E-print Network

Crystallization of atmospheric sulfate-nitrate-ammonium particles Scot T. Martin, Julie C the crystallization RH (CRH) at 293 K of particles throughout the entire sulfate-nitrate-ammonium composition space the same particle for compositions enriched in nitrate or somewhat acidic, although the CRH is under 30

310

Automated technologies needed to prevent radioactive materials from reentering the atmosphere  

NASA Technical Reports Server (NTRS)

Project SIREN (Search, Intercept, Retrieve, Expulsion Nuclear) has been created to identify and evaluate the technologies and operational strategies needed to rendezvous with and capture aerospace radioactive materials (e.g., a distressed or spent space reactor core) before such materials can reenter the terrestrial atmosphere and then to safely move these captured materials to an acceptable space destination for proper disposal. A major component of the current Project SIREN effort is the development of an interactive technology model (including a computerized data base) that explores in building block fashion the interaction of the technologies and procedures needed to successfully accomplish a SIREN mission. This SIREN model will include appropriate national and international technology elements-both contemporary and projected into the next century. To permit maximum flexibility and use, the SIREN technology data base is being programmed for use on 386-class PC's.

Buden, David; Angelo, Joseph A., Jr.

1991-01-01

311

Thermodynamic analysis of chemical stability of ceramic materials in hydrogen-containing atmospheres at high temperatures  

NASA Technical Reports Server (NTRS)

The chemical stability of several ceramic materials in hydrogen-containing environments was analyzed with thermodynamic considerations in mind. Equilibrium calculations were made as a function of temperature, moisture content, and total system pressure. The following ceramic materials were considered in this study: SiC, Si3N4, SiO2, Al2O3, mullite, ZrO2, Y2O3, CaO, MgO, BeO, TiB2, TiC, HfC, and ZrC. On the basis of purely thermodynamic arguments, upper temperature limits are suggested for each material for long-term use in H2-containing atmospheres.

Misra, Ajay K.

1990-01-01

312

Effect of atmospheric interference and sensor noise in retrieval of optically active materials in the ocean by hyperspectral remote sensing  

Microsoft Academic Search

We present a method to construct the best linear estimate of optically active material concentration from ocean radiance spectra measured through an arbitrary atmosphere layer by a hyperspectral sensor. The algorithm accounts for sensor noise. Optical models of seawater and maritime atmosphere were used to obtain the joint distribution of spectra and concentrations required for the algorithm. The accuracy of

Iosif M. Levin; Elizaveta Levina

2007-01-01

313

Models and methods for automated material identification in hyperspectral imagery acquired under unknown illumination and atmospheric conditions  

Microsoft Academic Search

The spectral radiance measured by an airborne imaging spectrometer for a material on the Earth's surface depends strongly on the illumination incident of the material and the atmospheric conditions. This dependence has limited the success of material-identification algorithms that rely on hyperspectral image data without associated ground-truth information. In this paper, the authors use a comprehensive physical model to show

Glenn Healey; David Slater

1999-01-01

314

Materials performance in the atmospheric fluidized-bed cogeneration air heater experiment  

SciTech Connect

The Atmospheric Fluidized-Bed Cogeneration Air Heater Experiment (ACAHE) sponsored by the US Department of Energy (DOE) was initiated to assess the performance of various heat-exchanger materials to be used in fluidized-bed combustion air heater systems. Westinghouse Electric Corporation, through subcontracts with Babcock Wilcox, Foster Wheeler, and ABB Combustion Engineering Systems, prepared specifications and hardware for the ACAHE tests. Argonne National Laboratory contracted with Rockwell International to conduct tests in the DOE atmospheric fluidized-bed combustion facility. This report presents an overview of the project, a description of the facility and the test hardware, the test operating conditions, a summary of the operation, and the results of analyzing specimens from several uncooled and cooled probes exposed in the facility. Extensive microstructural analyses of the base alloys, claddings, coatings, and weldments were performed on specimens exposed in several probes for different lengths of time. Alloy penetration data were determined for several of the materials as a function of specimen orientation and the exposure location in the combustor. Finally, the data were compared with earlier laboratory test data, and the long-term performance of candidate materials for air-heater applications was assessed.

Natesan, K.; Podolski, W.; Wang, D.Y.; Teats, F.G. (Argonne National Lab., IL (United States)); Gerritsen, W.; Stewart, A.; Robinson, K. (Rockwell International Corp., Canoga Park, CA (United States))

1991-02-01

315

Materials performance in the atmospheric fluidized-bed cogeneration air heater experiment  

SciTech Connect

The Atmospheric Fluidized-Bed Cogeneration Air Heater Experiment (ACAHE) sponsored by the US Department of Energy (DOE) was initiated to assess the performance of various heat-exchanger materials to be used in fluidized-bed combustion air heater systems. Westinghouse Electric Corporation, through subcontracts with Babcock & Wilcox, Foster Wheeler, and ABB Combustion Engineering Systems, prepared specifications and hardware for the ACAHE tests. Argonne National Laboratory contracted with Rockwell International to conduct tests in the DOE atmospheric fluidized-bed combustion facility. This report presents an overview of the project, a description of the facility and the test hardware, the test operating conditions, a summary of the operation, and the results of analyzing specimens from several uncooled and cooled probes exposed in the facility. Extensive microstructural analyses of the base alloys, claddings, coatings, and weldments were performed on specimens exposed in several probes for different lengths of time. Alloy penetration data were determined for several of the materials as a function of specimen orientation and the exposure location in the combustor. Finally, the data were compared with earlier laboratory test data, and the long-term performance of candidate materials for air-heater applications was assessed.

Natesan, K.; Podolski, W.; Wang, D.Y.; Teats, F.G. [Argonne National Lab., IL (United States); Gerritsen, W.; Stewart, A.; Robinson, K. [Rockwell International Corp., Canoga Park, CA (United States)

1991-02-01

316

Comprehending the activation of aerosol particles into cloud droplets: measuring strong surfactants in atmospheric aerosols and their kinetic effects  

NASA Astrophysics Data System (ADS)

This presentation will summarize several new developments in the field of aerosols and cloud droplet formation in the last few years. First, new chemical analysis methods were developed in our group and have evidenced the presence of very strong surfactants in a wide range of atmospheric aerosols, expected to strongly enhance the activation into cloud droplets. These analyses also reveal some variations of the surface tension of some aerosols with the season or with the presence or absence of clouds, providing new insight on the parameters controlling aerosol particle activation in the atmosphere. A summary of these results, covering a wide range of aerosols from remote and urban regions, will be presented. Comparing with field CCN measurements, it appeared that only the measurement techniques allowing for sufficient particle activation time (? 10 s) were able to confirm the presence of such strong surfactants. This suggested the occurrence time-dependent surface tension effects (or "kinetic" effects) in the activated particles, not well captured by these on-line techniques. Such effects were investigated in our laboratory with a range of model surfactants (Sodium dodecyl sulfate, rhamnolipids…) and the results will be presented. They show that, in some cases, strong surfactants need several ten of seconds to reach their full effect on the surface of micron-size particles. Therefore most current CCN measurement instruments are unable to capture the effect of strong surfactants in atmospheric aerosols. More importantly, these kinetics effects are representative of a wider range of molecular effects controlling the distribution of surfactants in the aqueous droplets and therefore their effect on particle activation. Although well documented in the "Colloid and Surfactant" literature, these effects are currently ignored in aerosols/CCN models resulting in erroneous calculations of the role of surfactants. Future measurements and techniques to investigate and fully understand these effects will be proposed.

Noziere, B.; Baduel, C.

2012-12-01

317

ACIDIC DEPOSITION AND THE CORROSION AND DETERIORATION OF MATERIALS IN THE ATMOSPHERE: A BIBLIOGRAPHY, 1880-1982  

EPA Science Inventory

The bibliography contains more than 1300 article citations and abstracts on the effects of acidic deposition, air pollutants, and biological and meteorological factors on the corrosion and deterioration of materials in the atmosphere. The listing includes citations for the years ...

318

Heterogeneous chemistry of atmospheric mineral dust particles and their resulting cloud-nucleation properties  

E-print Network

with ? app ~0.5. Notably, the particle generation methodfrom dry- and wet-generation. The best-fit ? app values fromapp = 1 .25 (Table Calcium carbonate and calcium sulfate were studied using two different particle generation

Sullivan, Ryan Christopher

2008-01-01

319

Molecular-structure variation of organic materials irradiated with atmospheric pressure plasma  

NASA Astrophysics Data System (ADS)

The effect of atmospheric pressure He plasma on the molecular structure of polyethylene terephthalate (PET) has been investigated. The plasma composition was analyzed using optical emission spectroscopy. In addition to strong He emission lines, lines due to O and N radicals were also detected. The change in the molecular structure of the PET film surface was investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. It was found that plasma irradiation led to oxidation and degradation of the surface due to chemical and physical effects of the active species. The results demonstrate the feasibility of observing the interaction of plasma with organic material on a local scale.

Takenaka, K.; Miyazaki, A.; Setsuhara, Y.

2014-06-01

320

The Stopping Power of Asteroidal Materials as High-Energy Charged Particle Shielding  

NASA Astrophysics Data System (ADS)

Extended human missions in deep space face a challenging radiation environment from high-energy galactic cosmic rays and solar energetic particles generated by solar flares and related coronal mass ejections. Shielding to attenuate these high-energy particles will require significant mass and volume, and would be extremely expensive launch from the surface of the earth. One possible solution could be the use of asteroidal resources as shielding for these high-energy particles. The effectiveness of shielding material for moderately relativistic charged particles is a function of the mean rate of energy loss, primarily to ionization and atomic excitation and is termed stopping power. In general, low atomic number elements are more effective per unit volume. We have calculated the stopping power for the average compositions of all major meteorite groups and will compare these data with typical spacecraft materials.

Pohl, Leos; Johnson, Daniel; Britt, Daniel

2014-11-01

321

Production and characterization of plutonium dioxide particles as a quality control material for safeguards purposes.  

PubMed

Plutonium (Pu) dioxide particles were produced from certified reference material (CRM) 136 solution (CRM 136-plutonium isotopic standard, New Brunswick Laboratory, Argonne, IL, U.S.A., 1987) using an atomizer system on December 3, 2009 after chemical separation of americium (Am) on October 27, 2009. The highest density of the size distribution of the particles obtained from 312 particles on a selected impactor stage was in the range of 0.7-0.8 ?m. The flattening degree of 312 particles was also estimated. The isotopic composition of Pu and uranium (U) and the amount of Am were estimated by thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICPMS), and ?-spectrometry. Within uncertainties the isotopic composition of the produced particles is in agreement with the expected values, which were derived from the decay correction of the Pu isotopes in the CRM 136. The elemental ratio of Am to Pu in the produced particles was determined on the 317th and 674th day after Am separation, and the residual amount of Am in the solution was estimated. The analytical results of single particles by micro-Raman-scanning electron microscopy (SEM)-energy-dispersive X-ray spectrometry (EDX) indicate that the produced particles are Pu dioxide. Our initial attempts to measure the density of two single particles gave results with a spread value accompanied by a large uncertainty. PMID:22372509

Shinonaga, Taeko; Donohue, David; Aigner, Helmut; Bürger, Stefan; Klose, Dilani; Kärkelä, Teemu; Zilliacus, Riitta; Auvinen, Ari; Marie, Olivier; Pointurier, Fabien

2012-03-20

322

Impact of different energies of precipitating particles on NOx generation in the middle and upper atmosphere during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Energetic particle precipitation couples the solar wind to the Earth's atmosphere and indirectly to Earth's climate. Ionisation and dissociation increases, due to particle precipitation, create odd nitrogen (NOx) and odd hydrogen (HOX) in the upper atmosphere, which can affect ozone chemistry. The long-lived NOx can be transported downwards into the stratosphere, particularly during the polar winter. Thus, the impact of NOx is determined by both the initial ionisation production, which is a function of the particle flux and energy spectrum, as well as transport rates. In this paper, we use the Sodankylä Ion and Neurtal Chemistry (SIC) model to simulate the production of NOx from examples of the most representative particle flux and energy spectra available today of solar proton events (SPE), auroral energy electrons, and relativistic electron precipitation (REP). Large SPEs are found to produce higher initial NOx concentrations than long-lived REP events, which themselves produce higher initial NOx levels than auroral electron precipitation. Only REP microburst events were found to be insignificant in terms of generating NOx. We show that the Global Ozone Monitoring by Occultation of Stars (GOMOS) observations from the Arctic winter 2003-2004 are consistent with NOx generation by a combination of SPE, auroral altitude precipitation, and long-lived REP events.

Turunen, Esa; Verronen, Pekka T.; Seppälä, Annika; Rodger, Craig J.; Clilverd, Mark A.; Tamminen, Johanna; Enell, Carl-Fredrik; Ulich, Thomas

2009-07-01

323

Particle size analysis of prepared solutions and fingerprint deposits of high explosive materials  

SciTech Connect

The Idaho National Engineering and Environmental Laboratory (INEEL) managed and operated by Lockheed Martin Idaho Technologies Company (LMITCO) was tasked via the Federal Aviation Administration (FAA) and US Department of Energy (DOE) to conduct various studies involving the detection and measurement of explosive materials and their associated residues. This report details the results of an investigation to determine the particle size characteristics of the explosive materials used in the design, development, and testing of trace explosives detection systems. These materials, in the form of water suspensions of plastic explosives, are used to provide a quantitative means of monitoring the performance characteristics of the detection systems. The purpose of this investigation is to provide data that allows a comparison between the particles deposited using the suspension standards and the particles deposited from fingerprints. This information may support the development of quality control aids, measurement methods, or performance criteria specifications for the use of trace explosives detection systems. For this report, particle size analyses were completed on explosives standard suspensions/solutions for composition C-4, Semtex-H, and Detasheet and fingerprints for C-4, Detasheet, and pentolite. Because of the difficulty in collecting microscopic images of the particles in the suspensions from test protocol surfaces, this paper discusses the characteristics of the particles as they are found on metal, glass, and paper. The results of the particle characterization analyses indicate that the water suspensions contain particulate composed of binder materials and dissolved portions of the explosive compounds. Upon drying of the water suspensions, significant particle nucleation and growth is observed. The nucleated particulate is comparable to the particulate deposited by fingerprints.

Carmack, W.J.; Hembree, P.B.

1998-03-01

324

The effect of particle size reduction of fibrous materials on TCLP results  

Microsoft Academic Search

The TCLP (toxicity characteristic leaching procedure) test is used to determine the mobility of toxic contaminants present in waste materials and to define hazardous wastes under RCRA. The test requires particle size reduction for solids > 9.5 mm. Filamentous wastes do not need particle size reduction if they have a surface area greater than 3.1 cm2\\/g. However, guidance in this

Bridget N. Bero; Margrit C. von Braun

1995-01-01

325

Reactivity of NaCl with Secondary Organic Acids: An Important Mechanism of the Chloride Depletion in Sea Salt Particles Mixed with Organic Materials  

NASA Astrophysics Data System (ADS)

Sea salt particles, one of the major sources of atmospheric aerosols, undergo complex multi-phase reactions and have profound consequences on their physical and chemical properties, thus on climate. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of sea salt chlorides with inorganic acids, such as nitric and sulfuric acids. Some studies have also showed that the chloride deficit cannot be fully compensated for this mechanism. We present an important pathway contributing to this chloride depletion: reactions of weak organic acids with sea salt particles. NaCl particles internally mixed with secondary organic materials generated from the reactions of limonene and alpha-pinene with ozone served as surrogates for sea salt particles mixed with organic materials. Chemical imaging analysis of these particles was conducted using complementary techniques including computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX), scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and micro-fourier transform infrared spectroscopy (micro-FTIR). Substantial chloride depletion and formation of organic salts were observed along with distinctive changes in particle morphology after hydration/dehydration processes. The results indicate that secondary organic acids can effectively react with NaCl particles resulting in displacement of chloride and release of gaseous HCl. This is consistent with a recent field study showing chloride depletion in sea salt particles mixed with organic materials which cannot be fully compensated by inorganic acid displacement. Although the formation of the organic salts is not thermodynamically favored in bulk aqueous solution, these reactions are driven by the high volatility and evaporation of gaseous HCl in particles, especially during hydration/dehydration processes. The proposed reactions may result in the formation of organic salts and production of HCl from sea salt particles that become mixed with organic acids during atmospheric aging that occurs with transport. The process of hydration/dehydration and these reactions may modify the physical and chemical properties of aged sea salt particles.

Wang, B.; Laskin, A.; Kelly, S.; Gilles, M. K.; Shilling, J. E.; Zelenyuk, A.; Wilson, J. M.; Tivanski, A.

2012-12-01

326

Atmospheric Environment 40 (2006) 68636878 Acid-catalyzed reactions of hexanal on sulfuric acid particles  

E-print Network

Atmospheric Environment 40 (2006) 6863Ā­6878 Acid-catalyzed reactions of hexanal on sulfuric acid are incorporated into atmospheric aerosols are not well understood. Acid-catalyzed reactions of compounds into acidic aerosols. In the present study, we use the aerodyne aerosol mass spectrometer (AMS) to probe

Elrod, Matthew J.

327

The thermal performance of fuel matrix material in a CO2 atmosphere  

NASA Astrophysics Data System (ADS)

The thermal oxidation performance of a semi-graphitic fuel matrix-material has been compared to two grades of nuclear graphite between 600 °C and 1200 °C in flowing CO2. Fuel matrix material is used to produce compacts or pebbles containing TRISO coated particle fuel for High Temperature Reactors (HTRs). The A3-27 fuel matrix-material grade was compared to NBG-18 and Gilsocarbon nuclear graphite grades. At 1200 °C temperatures A3-27 appears to be more reactive than NBG-18, but less so than Gilsocarbon. At 600 °C the oxidation rate of A3-27 is comparable to that of NBG-18, but both are significantly higher than that of Gilsocarbon. It is concluded that the comparable thermal oxidation behaviour of graphite and fuel-matrix material suggests that operating temperatures in a CO2 cooled reactor fuelled with TRISO coated particle fuel would not need to be reduced below those considered acceptable for the use of nuclear graphite.

Turner, J. D.; Schmidt, M. J. S.; Abram, T. J.

2013-11-01

328

Composite material reinforced with atomized quasicrystalline particles and method of making same  

DOEpatents

A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

Biner, Suleyman B. (Ames, IA); Sordelet, Daniel J. (Ames, IA); Lograsso, Barbara K. (Ames, IA); Anderson, Iver E. (Ames, IA)

1998-12-22

329

Composite material reinforced with atomized quasicrystalline particles and method of making same  

DOEpatents

A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quasicrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked composite exhibits substantially improved yield strength, tensile strength, Young`s modulus (stiffness). 3 figs.

Biner, S.B.; Sordelet, D.J.; Lograsso, B.K.; Anderson, I.E.

1998-12-22

330

particles  

NASA Astrophysics Data System (ADS)

We explore a facile and nontoxic hydrothermal route for synthesis of a Cu2ZnSnS4 nanocrystalline material by using l-cysteine as the sulfur source and ethylenediaminetetraacetic acid (EDTA) as the complexing agent. The effects of the amount of EDTA, the mole ratio of the three metal ions, and the hydrothermal temperature and time on the phase composition of the obtained product have been systematically investigated. The addition of EDTA and an excessive dose of ZnCl2 in the hydrothermal reaction system favor the generation of kesterite Cu2ZnSnS4. Pure kesterite Cu2ZnSnS4 has been synthesized at 180°C for 12 h from the reaction system containing 2 mmol of EDTA at 2:2:1 of Cu/Zn/Sn. It is confirmed by Raman spectroscopy that those binary and ternary phases are absent in the kesterite Cu2ZnSnS4 product. The kesterite Cu2ZnSnS4 material synthesized by the hydrothermal process consists of flower-like particles with 250 to 400 nm in size. It is revealed that the flower-like particles are assembled from single-crystal Cu2ZnSnS4 nanoflakes with ca. 20 nm in size. The band gap of the Cu2ZnSnS4 nanocrystalline material is estimated to be 1.55 eV. The films fabricated from the hierarchical Cu2ZnSnS4 particles exhibit fast photocurrent responses under intermittent visible-light irradiation, implying that they show potentials for use in solar cells and photocatalysis.

Xia, Yu; Chen, Zhihong; Zhang, Zhengguo; Fang, Xiaoming; Liang, Guozheng

2014-05-01

331

Single-particle chemical characterization and source apportionment of iron-containing atmospheric aerosols in Asian outflow  

NASA Astrophysics Data System (ADS)

Using a single-particle mass spectrometer, the size and chemical composition of individual Fe-containing atmospheric aerosols (Fe aerosols) with diameter from 100 to 1800 nm were characterized during Asian outflow season (spring of 2008) in Okinawa Island, Japan and their sources were determined. Fe aerosols were classified into five unique particle types which were mixed with specific compound(s) and related to their sources (crustal, fly ash/K-biomass burning, elemental carbon, metals, and vanadium). Particle number-based contribution of the crustal particle type, which has been thought to be the main source of aerosol Fe, was quite small (2 ˜ 10%) in all size ranges, while anthropogenic Fe aerosols were the dominant contributor in this study. Fly ash/K-biomass burning type was the most abundant particle types, which contributed ˜50%. Metals and elemental carbon types contributed ˜20% and ˜10%, respectively. Contribution of vanadium type was variable (5 ˜ 50%), which is attributed to ship emission. The frequent appearance of lithium ion peak in the fly ash/K-biomass burning type strongly suggests that large fraction of the type is coal combustion origin, reflecting high coal usage in China. These results show that anthropogenic sources contributes significant portion of Fe aerosols in Asian outflow. Excluding the vanadium type, relative contribution of the remaining four particle types was constant over the course of study, which remained even when the total concentration of Fe aerosols changed and fraction of the Fe aerosols among atmospheric aerosols decreased significantly by the switch of air mass type into marine type. We concluded that the observed constant relative abundance reflected the relative source strength of Fe aerosols in Asian outflow, particularly emphasizing the importance of coal combustion source in East Asia.

Furutani, Hiroshi; Jung, Jinyoung; Miura, Kazuhiko; Takami, Akinori; Kato, Shungo; Kajii, Yoshizumi; Uematsu, Mitsuo

2011-09-01

332

Adaptive binary material classification of an unknown object using polarimetric images degraded by atmospheric turbulence  

NASA Astrophysics Data System (ADS)

An improved binary material-classification algorithm using passive polarimetric imagery degraded by atmospheric turbulence is presented. The technique implements a modified version of an existing polarimetric blind-deconvolution algorithm in order to remove atmospheric distortion and correctly classify the unknown object. The classification decision, dielectric or metal in this case, is based on degree of linear polarization (DoLP) estimates provided by the blind-deconvolution algorithm augmented by two DoLP priors - one statistically modeling the polarization behavior of metals and the other statistically modeling the polarization behavior of dielectrics. The DoLP estimate which maximizes the log-likelihood function determines the image pixel's classification. The method presented here significantly improves upon a similar published polarimetric classification method by adaptively updating the DoLP priors as more information becomes available about the scene. This new adaptive method significantly extends the range of validity of the existing polarimetric classification technique to near-normal collection geometries where most polarimetric material classifiers perform poorly. In this paper, brief reviews of the polarimetric blind-deconvolution algorithm and the functional forms of the DoLP priors are provided. Also provided is the methodology for making the algorithm adaptive including three techniques for updating the DoLP priors using in-progress DoLP estimates. Lastly, the proposed technique is experimentally validated by comparing classification results of two dielectric and metallic samples obtained using the new method to those obtained using the existing technique.

Kim, Mu J.; Hyde, Milo W.

2012-10-01

333

Particle Size of CO2 Condensates in Mars Atmosphere Revealed by Climate Sounder and Laser Ranging Observations  

NASA Astrophysics Data System (ADS)

Current-generation Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter (MRO) offers extensive coverage of the latitudinal and seasonal distribution of CO_2 condensation in Mars’s atmosphere. The atmospheric temperature profiles measured by MCS reveal that the thickness of CO_2 condensation layer reaches a maximum of 10-15 km (north) or ˜20 km (south) during the middle of winter. There is a shrinking of the CO_2 condensation layer from L_S ˜270(°) to ˜300(°) in 2007, probably related to a planet-encircling dust storm. We integrate the condensation area and the condensation occurrence rate synthesized from the MCS observations to estimate cumulative masses of CO2 condensates deposited onto the northern and southern seasonal polar caps. The mass loading of CO_2 condensate particles, when condensation occurs, can be independently inferred from the detections of reflective clouds by the Mars Orbiter Laser Altimetry (MOLA) onboard the Mars Global Surveyor (MGS). Therefore, we approximate the precipitation flux by the particle settling flux, which is estimated using the impulse responses of MOLA filter channels. With our approach, the total atmospheric condensation mass can be estimated from these observational data sets, with average particle size as the only free parameter. By comparison with the seasonal polar cap masses inferred from the time-varying gravity of Mars, our estimates indicate that the average condensate particle radius is 8 - 22 mum in the northern hemisphere and 4 - 13 mum in the southern hemisphere. This multi-instrument data analysis provides new constraints on modeling the microphysics of CO_2 clouds on Mars.

Hu, Renyu

334

Atmospheric concentrations and gas/particle partitioning of neutral poly- and perfluoroalkyl substances in northern German coast  

NASA Astrophysics Data System (ADS)

Total 58 high volume air samples were collected in Büsum, Germany, from August 2011 to October 2012 to investigate air concentrations of 12 per- and polyfluoroalkyl substances (PFASs) and their gas/particle partitioning. The total concentration (vapor plus particle phases) of the 12 PFASs (?PFASs) ranged from 8.6 to 155 pg/m3 (mean: 41 pg/m3) while fluorotelomer alcohols 8:2 (8:2 FTOH) dominated all samples accounting for 61.9% of ?PFASs and the next most species were 10:2 FTOH (12.7%). Air mass back trajectory analysis showed that atmospheric PFASs in most samples were from long range atmospheric transport processes and had higher ratios of 8:2 to 6:2 FTOH compared to the data obtained from urban/industrial sources. Small portion of particle PFASs in the atmosphere was observed and the average percent to ?PFASs was 2.0%. The particle-associated fractions of different PFASs decreased from perfluorooctane sulfonamidoethanols (FOSEs) (15.5%) to fluorotelomer acrylates (FTAs) (7.6%) to perfluorooctane sulfonamides (FOSAs) (3.1%) and FTOHs (1.8%), indicating the functional group obviously influenced their gas/particle partitioning. For neutral compounds with acid dissociation constant (pKa) > 7.0 (i.e., FTOHs, FOSEs and FOSAs), a significant log-linear relationship was observed between their gas/particle partition coefficients (KSP) and vapor pressures (pŗL), suggesting the gas/particle partitioning of neutral PFASs agreed with the classical logKSP-logpŗL relation. Due to the pKa values of 6:2 and 8:2 FTA below the typical environmental pH conditions, they mainly exist as ionic form in aerosols, and the corrected logKSP (neutral form) were considerably lower than those of FTOHs, FOSEs and FOSAs with similar vapor pressures. Considering the strong partitioning potential to aqueous phases for ionic PFASs at higher pH values, a need exists to develop a model taking account of the ad/absorption mechanism to the condensed phase of aerosols for ionizable PFASs (e.g., FTAs).

Wang, Zhen; Xie, Zhiyong; Möller, Axel; Mi, Wenying; Wolschke, Hendrik; Ebinghaus, Ralf

2014-10-01

335

Composition and properties of atmospheric particles in the eastern Atlantic and impacts on gas phase uptake rates  

NASA Astrophysics Data System (ADS)

Marine aerosol composition continues to represent a large source of uncertainty in the study of climate and atmospheric chemistry. In addition to their physical size and chemical composition, hygroscopicity plays a significant role, increasing the particles' surface areas and scattering potential. Simultaneous aerosol measurements were performed on board the RRS Discovery and at the Cape Verde atmospheric observatory during the Aerosol Composition and Modelling in the Marine Environment (ACMME) and Reactive Halogens in the Marine Boundary Layer (RHAMBLE) experiments. These included online measurements of number and dry size and bulk collection for offline analysis of aqueous ions. In addition, the measurements on board the Discovery included online measurements of composition using an Aerodyne Aerosol Mass Spectrometer, optical absorption using a Multi Angle Absorption Photometer, ambient humidity size distribution measurements using a humidified differential mobility particle sizer (DMPS) and optical particle counter (OPC) and hygroscopicity measurements with a hygroscopicity tandem differential mobility analyser (HTDMA). Good agreement between platforms in terms of the sea salt (ss) and non sea salt (nss) modes was found during the period when the Discovery was in close proximity to Cape Verde and showed a composition consistent with remote marine air. As the Discovery approached the African coast, the aerosol showed signs of continental influence such as an increase in particle number, optical absorption, enhancement of the nss mode and dust particles. The Cape Verde site was free of this influence during this period. Chloride and bromide showed concentrations with significant deviations from seawater relative to sodium, indicating that atmospheric halogen processing (and/or acid displacement for chloride) had taken place. The time dependent ambient size distribution was synthesised using humidified DMPS and OPC data, corrected to ambient humidity using HTDMA data. Heterogeneous uptake rates of hypoiodous acid (HOI) were also predicted and the nss accumulation mode was found to be the most significant part of the size distribution, which could act as an inert sink for this species. The predicted uptake rates were enhanced by around a factor of 2 during the African influence period due to the addition of both coarse and fine particles. The hygroscopicity of the nss fraction was modelled using the Aerosol Diameter Dependent Equilibrium Model (ADDEM) using the measured composition and results compared with the HTDMA data. This was the first time such a reconciliation study with this model has been performed with marine data and good agreement was reached within the resolution of the instruments. The effect of hygroscopic growth on HOI uptake was also modelled and ambient uptake rates were found to be approximately doubled compared to equivalent dry particles.

Allan, J. D.; Topping, D. O.; Good, N.; Irwin, M.; Flynn, M.; Williams, P. I.; Coe, H.; Baker, A. R.; Martino, M.; Niedermeier, N.; Wiedensohler, A.; Lehmann, S.; Müller, K.; Herrmann, H.; McFiggans, G.

2009-12-01

336

Composition and properties of atmospheric particles in the eastern Atlantic and impacts on gas phase uptake rates  

NASA Astrophysics Data System (ADS)

Marine aerosol composition continues to represent a large source of uncertainty in the study of climate and atmospheric chemistry. In addition to their physical size and chemical composition, hygroscopicity plays a significant role, increasing the particles' surface areas and scattering potential. Simultaneous aerosol measurements were performed on board the RRS Discovery and at the Cape Verde atmospheric observatory during the Aerosol Composition and Modelling in the Marine Environment (ACMME) and Reactive Halogens in the Marine Boundary Layer (RHAMBLE) experiments. These included online measurements of number and dry size and bulk collection for offline analysis of aqueous ions. In addition, the measurements on board the Discovery included online measurements of composition using an Aerodyne Aerosol Mass Spectrometer, optical absorption using a Multi Angle Absorption Photometer, ambient humidity size distribution measurements using a humidified differential mobility particle sizer (DMPS) and optical particle counter (OPC) and hygroscopicity measurements with a hygroscopicity tandem differential mobility analyser (HTDMA). Good agreement between platforms in terms of the sea salt (ss) and non sea salt (nss) modes was found during the period when the Discovery was in close proximity to Cape Verde and showed a composition consistent with remote marine air. As the Discovery approached the African coast, the aerosol showed signs of continental influence such as an increase in particle number, optical absorption, enhancement of the nss mode and dust particles. The Cape Verde site was free of this influence during this period. Chloride and bromide showed concentrations with significant deviations from seawater relative to sodium, indicating that atmospheric halogen processing (and/or acid displacement for chloride) had taken place. The time dependent ambient size distribution was synthesised using humidified DMPS and OPC data, corrected to ambient humidity using HTDMA data. Heterogeneous uptake rates of HOI were also predicted and the nss accumulation mode was found to be the most significant part of the size distribution, which could act as an inert sink for this species. The predicted uptake rates were enhanced by around a factor of 2 during the African influence period due to the addition of both coarse and fine particles. The hygroscopicity of the nss fraction was modelled using the Aerosol Diameter Dependent Equilibrium Model (ADDEM) using the measured composition and results compared with the HTDMA data. This was the first time such a reconciliation study with this model has been performed with marine data and good agreement was reached within the resolution of the instruments. The effect of hygroscopic growth on HOI uptake was also modelled and ambient uptake rates were found to be approximately doubled compared to equivalent dry particles.

Allan, J. D.; Topping, D. O.; Good, N.; Irwin, M.; Flynn, M.; Williams, P. I.; Coe, H.; Baker, A. R.; Martino, M.; Niedermeier, N.; Wiedensohler, A.; Lehmann, S.; Müller, K.; Herrmann, H.; McFiggans, G.

2009-09-01

337

Development of the Moving Least Squares Smooth Particle Hydrodynamics Approach For Inert/Energetic Material Interaction  

NASA Astrophysics Data System (ADS)

PRIMEX-Warhead Systems (PWS) has developed a smooth particle code based upon a methodology developed by G. Dilts (1999) referred to as MLSPH (Moving Least Squares Smooth Paticles Hydrodynamics). The object is to solve general high rate problems associated with the interaction of energetic and inert materials. Some conservative numerical schemes in cylindrical geometry were developed as well 1D, 2D, and 3D cartesian coding. We use a simple neighbor search technique that limits the computation of searching neighbor particles to one order lower compared to the total CPU time of calculation. PWSuses randomly distributed phantom particles to eliminate certain terms in the numerical growth factor, thus improving the stability of the MLSPH method. In fact, the stability factor can be close to unity. The boundary treatment is also naturally implemented by using this approach. The particle size effect has been minimized through rezoning. PWS developed a new numerical technique of second order accuracy that exactly conserves mass and volume. The rezoning technique provides smoother boundary surface and improves stability by naturally moving apart the particles that are close together. This rezoning method can be used to construct a conservative scheme for volume expansion of particles (mass conservation) that keeps the volume sum of particles equal to the volume enclosed by boundaries, this feature is not satisfied in other SPH schemes. We have also started working on the implementation of a general 3D rezoning technique for SPH. The PWS-MLSPH code is able to deal with material interactions between solid, fluid and gas. Several reaction models are contained in the code to solve problems that involves explosives. In particular the burn process of inert materials contained in an explosive matrix is handled with a 'neighbor ignition' method. That allows an explosive particle to be ignited only by another burning explosive particle that is close enough. We will present a calculation involving the interaction of inert tungsten particles in a TNT matrix. The program will eventually be modified to allow for energy release of metallic particles into the reaction zone (as a function of particle size and coating). The figure below depicts a calculation of 100 micron tungsten in a 60/40 volume ratio.

Yao, Jin; Gunger, Michael

2001-06-01

338

Black carbon enrichment in atmospheric ice particle residuals observed in lower trophospheric mixed phase clouds  

SciTech Connect

The enrichment of black carbon (BC) in residuals of small ice particles was investigated during intensive experiments in winter 2004 and 2005 at the high alpine research station Jungfraujoch (3580 m asl, Switzerland). Two inlets were used to sample the bulk aerosol (residuals of cloud droplets and ice crystals as well as non-activated aerosol particles) and the residual particles of small ice crystals (diameter 5 - 20 m). An enrichment of the BC mass fraction in the ice particle residuals was observed by investigating the measured BC mass concentration as a fraction of the bulk (submicrometer) aerosol mass concentration sampled by the two inlets. On average, the BC mass fraction was 5% for the bulk aerosol and 14% for the ice particle residuals. The observed enrichment of BC in ice particle residuals suggests that BC may act as ice nuclei, with important implications for the indirect aerosol effect via glaciation of clouds.

Cozic, J.; Mertes, S.; Verheggen, B.; Cziczo, Dan; Gallavardin, S. J.; Walter, S.; Baltensperger, Urs; Weingartner, E.

2008-08-15

339

Trace elements in chondritic stratospheric particles - Zinc depletion as a possible indicator of atmospheric entry heating  

NASA Technical Reports Server (NTRS)

Major-element abundances in 11 C, C?, and TCA cosmic dust particles have been measured using SEM and TEM energy dispersive X-ray (EDX) systems. The Fe/Ni ratio, when coupled with major element abundances, appears to be a useful discriminator of cosmic particles. Three particles classified as C?, but having Fe/Ni peak height ratios similar to those measured on the powdered Allende meteorite sample in their HSC EDX spectra, exhibit chondritic minor-/trace-element abundance patterns, suggesting they are extraterrestrial. The one particle classified as C-type, but without detectable Ni in its JSC EDX spectrum, exhibits an apparently nonchondritic minor-/trace-element abundance pattern. A class of particles that are chondritic except for large depletions in the volatile elements Zn and S has been identified. It is likely that these particles condensed with a C1 abundance pattern and that Zn and S were removed by some subsequent process.

Flynn, G. J.; Sutton, S. R.

1992-01-01

340

Fluorescence spectra of atmospheric aerosol at Adelphi, Maryland, USA: measurement and classification of single particles containing organic carbon  

NASA Astrophysics Data System (ADS)

We measured laser-induced fluorescence spectra from individual supermicron-sized atmospheric particles drawn into our laboratory at Adelphi, MD, an urban site in the Washington, DC metroplex. A virtural impactor concentrator is used along with an aerodynamic-focusing-nozzle which forms, within an optical chamber, a focused aerosol jet where single aerosol particles can be interrogated on-the-fly with a pulsed 266-nm-wavelength laser. Sample rates are a few liter per minute, and are size dependent. Crossed-diode laser beams indicate when a particle is traversing the sample region and are used to trigger the UV laser to fire and the gated intensified CCD to record the fluorescence spectrum. Our breadboard fluorescence particle spectrometer measures particles in the 3-10 ?m diameter size range. Typical trigger rates are a few per second. The usable spectral range is from about 295 to 605 nm. The majority of the particles have very weak fluorescence (on average 8 percent of particles have fluorescence signals above noise). The spectra were grouped using a heirarchical cluster analysis, with parameters chosen so that spectra typically cluster into 4-12 main categories. From the set of all cluster spectra we chose 8 template spectra for reanalyzing all the data. On average, 92 percent (81-94 percent) of the spectra were similar to these templates (using the same thresholds used for the cluster analysis). The major emission bands of the most commonly occurring spectra have peaks: near 460 nm (28 percent of fluorescent particles on average), a very broad hump, and may be humic acids or humic like substances; near 317 nm (on average 24 percent of fluorescent particles); near 321 and 460 nm (a double hump, 12 percent of fluorescent particles); and near 341 nm (8 percent of fluorescent particles). Some of the fluorescence in spectra peaking in the 317-341 nm range is probably from dicyclic aromatics and heterocyclics, including the amino acid tryptophan in biological particles such as bacteria and spores.

Pinnick, Ronald G.; Hill, Steven C.; Pan, Yong-Le; Chang, Richard K.

341

New applications of particle accelerators in medicine, materials science, and industry  

SciTech Connect

Recently, the application of particle accelerators to medicine, materials science, and other industrial uses has increased dramatically. A random sampling of some of these new programs is discussed, primarily to give the scope of these new applications. The three areas, medicine, materials science or solid-state physics, and industrial applications, are chosen for their diversity and are representative of new accelerator applications for the future.

Knapp, E.A.

1981-01-01

342

Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications  

Microsoft Academic Search

In diatremes and other volcanic vents, steep bodies of volcaniclastic material having differing properties (particle size\\u000a distribution, proportion of lithic fragments, etc.) from those of the surrounding vent-filling volcaniclastic material are\\u000a often found. It has been proposed that cylindrical or cone-shaped bodies result from the passage of “debris jets” generated\\u000a after phreatomagmatic explosions or other discrete subterranean bursts. To learn

Pierre-Simon Ross; James D. L. White; Bernd Zimanowski; Ralf Büttner

2008-01-01

343

Heterogeneous atmospheric chemistry of lead oxide particles with nitrogen dioxide increases lead solubility: environmental and health implications.  

PubMed

Heterogeneous chemistry of nitrogen dioxide with lead-containing particles is investigated to better understand lead metal mobilization in the environment. In particular, PbO particles, a model lead-containing compound due to its widespread presence as a component of lead paint and as naturally occurring minerals, massicot, and litharge, are exposed to nitrogen dioxide at different relative humidity. X-ray photoelectron spectroscopy (XPS) shows that upon exposure to nitrogen dioxide the surface of PbO particles reacts to form adsorbed nitrates and lead nitrate thin films with the extent of nitrate formation relative humidity dependent. NO(2)-exposed PbO particles are found to have an increase in the amount of lead that dissolves in aqueous suspensions at circumneutral pH compared to particles not exposed. These results point to the potential importance and impact that heterogeneous chemistry with trace atmospheric gases can have on increasing solubility and therefore the mobilization of heavy metals, such as lead, in the environment. This study also shows that surface intermediates that form, such as adsorbed lead nitrates, can yield higher concentrations of lead in water systems. These water systems can include drinking water, groundwater, estuaries, and lakes. PMID:23057678

Baltrusaitis, Jonas; Chen, Haihan; Rubasinghege, Gayan; Grassian, Vicki H

2012-12-01

344

Heterogeneous Atmospheric Chemistry of Lead Oxide Particles with Nitrogen Dioxide Increases Lead Solubility: Environmental and Health Implications  

PubMed Central

Heterogeneous chemistry of nitrogen dioxide with lead-containing particles is investigated to better understand lead metal mobilization in the environment. In particular, PbO particles, a model lead-containing compound due to its wide spread presence as a component of lead paint and as naturally occurring minerals, massicot and litharge, are exposed to nitrogen dioxide at different relative humidity. X-ray photoelectron spectroscopy (XPS) shows that upon exposure to nitrogen dioxide the surface of PbO particles react to form adsorbed nitrates and lead nitrate thin films with the extent of formation of nitrate relative humidity dependent. Surface adsorbed nitrate increases the amount of dissolved lead. These reacted particles are found to have an increase in the amount of lead that dissolves in aqueous suspensions at circumneutral pH compared to unreacted particles. These results point to the potential importance and impact that heterogeneous chemistry with trace atmospheric gases can have on increasing solubility and therefore the mobilization of heavy metals, such as lead, in the environment. This study also show that surface intermediates, such as adsorbed nitrates, that form can yield higher concentrations of lead in water systems. In the environment, these water systems can include drinking water, ground water, estuaries and lakes. PMID:23057678

Baltrusaitis, Jonas; Chen, Haihan; Rubasinghege, Gayan

2012-01-01

345

Atmospheric behavior of trace elements on particles emitted from a coal-fired power plant  

NASA Astrophysics Data System (ADS)

Filter and cascade impactor samples of suspended particles were collected in-stack and at distances up to 64 km downwind in the plume of a large western coal-fired power plant equipped with both electrostatic precipitators (ESP) and venturi wet particulate scrubbers (VWS) to investigate modifications of the particulate signatures of minor and trace elements during transport. Samples were analyzed for 40 elements by instrumental neutron activation analysis. Precipitator malfunction during the experiment caused greater than normal emission of large particles, and concentrations of As, Zn, Sb, Mo, Ga, W, U, V and Ba in near-plume particles collected on filters were enriched relative to their concentrations in stack particles by factors of 1.4 to 2.5, presumably because of sedimentation of very large particles. Selenium was enriched by up to 6-fold (plume:stack). However, enrichment of elements in the plume relative to more typical in-stack particles were insignificant for all elements except Se, which was enriched 2.3-fold. Concentrations of Se on particles in the stack and plume suggest that most of the Se vapor in stack gases became associated with aerosol particles soon after emission. Thus although significant post-emission modifications of elemental signatures of particles may occur for poorly controlled plants, little change is expected for well-controlled plants equipped with ESPs except for Se. Source signatures measured for Se must account for vapor deposition. Impactor data showed a preferential decrease in the concentrations of the above elements in submicrometer particles; suggesting that either intermodal coagulation or size selective sampling losses were important. The impactor data further suggest that enrichment-particle-size profiles for VWS emissions were not conservative during transport.

Ondov, J. M.; Choquette, C. E.; Zoller, W. H.; Gordon, G. E.; Biermann, A. H.; Heft, R. E.

346

Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds  

Microsoft Academic Search

Although organic compounds typically constitute a substantial fraction of the fine particulate matter (PM) in the atmosphere, their molecular composition remains poorly characterized. This is largely because atmospheric particles contain a myriad of diverse organic compounds, not all of which extract in a single solvent or elute through a gas chromatograph; therefore, a substantial portion typically remains unanalyzed. Most often

Pradeep Saxena; Lynn M. Hildemann

1996-01-01

347

Relationship of Atmospheric Pollution Characterized by Gas (NO 2 ) and Particles (PM10) to Microbial Communities Living in Bryophytes at Three Differently Polluted Sites (Rural, Urban, and Industrial)  

Microsoft Academic Search

Atmospheric pollution has become a major problem for modern societies owing to its fatal effects on both human health and\\u000a ecosystems. We studied the relationships of nitrogen dioxide atmospheric pollution and metal trace elements contained in atmospheric\\u000a particles which were accumulated in bryophytes to microbial communities of bryophytes at three differently polluted sites\\u000a in France (rural, urban, and industrial) over

Caroline Meyer; Daniel Gilbert; André Gaudry; Marielle Franchi; Hung Nguyen-Viet; Juliette Fabure; Nadine Bernard

2010-01-01

348

Physicochemical properties and ability to generate free radicals of ambient coarse, fine, and ultrafine particles in the atmosphere of Xuanwei, China, an area of high lung cancer incidence  

NASA Astrophysics Data System (ADS)

The link between the high incidence of lung cancer and harmful pollutants emitted by local coal combustion in Xuanwei, Yunnan province, China, has been a focus of study since the 1980s. However, the mechanisms responsible for the high lung cancer rate remain unclear, necessitating further study. Since a close relationship between ambient air particle pollution and respiratory diseases exists, we sampled size-resolved ambient particles from the atmosphere of Xuanwei. In our indoor experiment, cutting-edge methods, including scanning electron microscopy coupled with energy dispersive X-ray detection (SEM/EDX), particle-induced X-ray emission (PIXE), electronic paramagnetic resonance (EPR) and the cell-free DCFH-DA assay, were employed to investigate the physicochemical properties, the potential to generate free radicals and the oxidative potential of ambient coarse (diameter, 1.8-10 ?m), fine (diameter, 0.1-1.8 ?m), and ultrafine (diameter, <0.1 ?m) particles. We found the total mass concentrations of the size-resolved particles collected in spring were higher than that in early winter. Mass percentage of fine particles accounted for 68% and 61% of the total particulate mass in spring and in early winter samples, respectively, indicating that fine particles were the major component of the Xuanwei ambient particulate matters. On the other hand, the results of SEM/EDX analysis showed that the coarse particles were dominated by minerals, the fine particles by soot aggregates and fly ashes, and the ultrafine particles by soot particles and unidentified particles. Our PIXE results revealed that crustal elements (Ca, Ti Si, Fe) were mainly distributed in coarse particles, while trace metals (Cr, Mn, Ni, Cu, Zn, Pb) dominated in the fine particle fraction, and S, a typical element emitted by coal combustion, mainly resided in fine particles collected from the winter atmosphere. EPR results indicated that the magnitude of free radical intensity caused by size-resolved particles followed these patterns: fine particles > coarse particles > ultrafine particles for spring samples and ultrafine particles > fine particles > coarse particles for winter samples. Cell-free DCFH assay results conclusively showed that all of the measured particle suspensions displayed a higher oxidative potential than the negative control. The correlation coefficient (R2) between free radical intensity and fluorescent intensity generated by the size-resolved particles was 0.535 and 0.507 for the spring and winter seasons, respectively, implying that ambient air particles in the Xuanwei atmosphere have the ability to generate free radicals, and fine and ultrafine particles could be hazardous to local residents.

Lu, Senlin; Yi, Fei; Hao, Xiaojie; Yu, Shang; Ren, Jingjing; Wu, Minghong; Jialiang, Feng; Yonemochi, Shinich; Wang, Qingyue

2014-11-01

349

Measurement of size, concentration and structure of atmospheric particulates by the airborne continuous particle replicator  

Microsoft Academic Search

An assessment is made of the design characteristics of a continuous formvar cloud particle replicator for use on a pressurized aircraft such as the C130. Correction of measured replica particle concentrations is required depending on the siting of the instrument on the aircraft and the geometry of the collecting probe, to give free air concentration. A correction may also be

J. Hallett

1976-01-01

350

USE OF METAL- AND FLUORESCEIN-TAGGED MATERIALS TO STUDY SETTLED PARTICLES EXPOSURE PATHWAYS  

EPA Science Inventory

Through the use of ten size ranges of tagged materials (Antley et. al., 2000a), inductively coupled plasma- mass spectrometry (ICP-MS) and flourometry are being used to study the movement of settled particles in the indoor environment, exposure pathways, and the collection effi...

351

Isotope abundances of solar coronal material derived from solar energetic particle measurements  

Microsoft Academic Search

Coronal isotopic abundances for the elements He, C, N, O, Ne, and Mg are derived from previously published measurements of the isotopic composition of solar energetic particles by first measuring, and then correcting for, the charge-to-mass-dependent fractionation due to solar flare acceleration and propagation processes. The resulting coronal composition generally agrees with that of other samples of solar system material,

R. A. Mewaldt; E. C. Stone

1989-01-01

352

Modeling of microwave absorbing structure using winning particle optimization applied on electrically conductive nanostructured composite material  

Microsoft Academic Search

This work presents the design and optimization of a Radar Absorbing Material system in the X-band frequency using evolutionary algorithm. Winning Particle Optimization is a new evolutionary algorithm. Due to its elementary evolving mechanism, it recall in mind primordial life form in trying to search the best place to proliferate. It is shown that such method, is quite simple but

Davide Micheli; Carmelo Apollo; Roberto Pastore; Mario Marchetti

2010-01-01

353

Effects of cement particle size distribution on performance properties of Portland cement-based materials  

SciTech Connect

The original size, spatial distribution, and composition of Portland cement particles have a large influence on hydration kinetics, microstructure development, and ultimate properties of cement-based materials. In this paper, the effects of cement particle size distribution on a variety of performance properties are explored via computer simulation and a few experimental studies. Properties examined include setting time, heat release, capillary porosity percolation, diffusivity, chemical shrinkage, autogenous shrinkage, internal relative humidity evolution, and interfacial transition zone microstructure. The effects of flocculation and dispersion of the cement particles in the starting microstructures on resultant properties are also briefly evaluated. The computer simulations are conducted using two cement particle size distributions that bound those commonly in use today and three different water-to-cement ratios: 0.5, 0.3, and 0.246. For lower water-to-cement ratio systems, the use of coarser cements may offer equivalent or superior performance, as well as reducing production costs for the manufacturer.

Bentz, D.P.; Garboczi, E.J.; Haecker, C.J.; Jensen, O.M.

1999-10-01

354

Test of hadron interaction models in the most important energy range of secondary particles in spectra of atmospheric muons  

NASA Astrophysics Data System (ADS)

A simple method has been proposed for testing hadron interaction models, which are used to simulate extensive air showers, in observed spectra of atmospheric muons. It has been shown that muon flux intensities in the energy range of 102-104 GeV that are calculated within the SIBYLL 2.1, QGSJETII-04, and QGSJET01 models exceed the data of the classical experiments L3 + Cosmic, MACRO, and LVD on the spectra of atmospheric muons by a factor of 1.5-2. It has been concluded that these tested models overestimate the generation of secondary particles with the highest energies in elementary events of interaction between hadrons in agreement with the LHCf and TOTEM accelerator experiments.

Dedenko, L. G.; Roganova, T. M.; Fedorova, G. F.

2014-10-01

355

A Massively Parallel Particle Code for Rarefied Ionized and Neutral Gas Flows in Earth and Planetary Atmospheres, Ionospheres and Magnetospheres  

NASA Technical Reports Server (NTRS)

In order to understand the global structure, dynamics, and physical and chemical processes occurring in the upper atmospheres, exospheres, and ionospheres of the Earth, the other planets, comets and planetary satellites and their interactions with their outer particles and fields environs, it is often necessary to address the fundamentally non-equilibrium aspects of the physical environment. These are regions where complex chemistry, energetics, and electromagnetic field influences are important. Traditional approaches are based largely on hydrodynamic or magnetohydrodynamic MHD) formulations and are very important and highly useful. However, these methods often have limitations in rarefied physical regimes where the molecular collision rates and ion gyrofrequencies are small and where interactions with ionospheres and upper neutral atmospheres are important.

Combi, Michael R.

2004-01-01

356

Quasistatic rheology and microstructural description of sheared granular materials composed of platy particles  

NASA Astrophysics Data System (ADS)

This is the first paper of a series devoted to the micro-mechanical modeling of clayey soils, by means of discrete element simulations. We specifically focus here on the effect of the platy shape of particles by reducing the interactions between particles to mechanical contact forces (i.e., neither electrostatic repulsion nor van der Waals forces are taken into account). The particles are three-dimensional square plates, approximated as spheropolyhedra. Several samples composed of particles of different levels of platyness (related to the ratio of length to thickness) were numerically prepared and sheared up to large deformations. We analyzed the shear strength, packing fraction, orientation of the particles, connectivity, fabric of the interactions network, and interaction forces as functions of the platyness. We find that both the mechanical behavior and microstructure are strongly dependent on the degree of platyness. The principal underlying phenomenon is the alignment of particle faces along a particular direction. This ordering phenomenon, which emerges even for shapes that deviate only slightly from that of a sphere, enhances the ability of the packing to develop an anisotropic structure leading to large shear strength, especially as a consequence of the fabric and mobilization of friction forces. Moreover, the connectivity of the packings and their packing fraction also evolve with the platyness. In particular, the packing fraction evolves in a nonmonotonic fashion, as observed in other granular materials composed of elongated or angular particles.

Boton, Mauricio; Azéma, Emilien; Estrada, Nicolas; Radjaļ, Farhang; Lizcano, Arcesio

2013-03-01

357

Automated technologies needed to prevent radioactive materials from reentering the atmosphere  

NASA Technical Reports Server (NTRS)

Project SIREN (Search, Intercept, Retrieve, Expulsion Nuclear) was created to identify and evaluate the technologies and operational strategies needed to rendezvous with and capture aerospace radioactive materials (e.g., a distressed or spent space reactor core) before such materials can reenter the terrestrial atmosphere and then to safely move these captured materials to an acceptable space destination for proper disposal. A major component of the current project SIREN effort is the development of an interactive technology model (including a computerized data base) that explores, in building-block fashion, the interaction of the technologies and procedures needed to successfully accomplish a SIREN mission. The SIREN model will include appropriate national and international technology elements--both contemporary and projected into the next century. To obtain maximum flexibility and use, the SIREN technology data base is being programmed for use on 286-class PC's. The major technical elements for a successful SIREN mission include: ground and space-based tracking, launch vehicles of needed payload capacity, telerobotic systems, sensors, capture technologies, and space transport and disposal. However, Project SIREN also will impose specialized requirements including the use of dextrous aerospace systems capable of properly functioning in intense radiation and thermal environments.

Buden, David; Angelo, Joseph A., Jr.

1991-01-01

358

Exploration of Heterogeneous Chemistry in Model Atmospheric Particles Using Extended X-ray Absorption Fine Structure Analysis  

SciTech Connect

As models of the composition and heterogeneous chemical reactions of the troposphere undergo refinement, novel application of state-of-the-art analytical techniques will be necessary to propound realistic characterizations of mineral dust chemistry. In this study, strontium carbonate particles treated with gaseous nitric acid and nitrogen dioxide were examined with X-ray absorption fine structure analysis (EXAFS). The X-ray spectra of carbonate and nitrate standards were fitted to ab initio calculations, which were used to determine the structure and consistency of strontium nitrate formed on strontium carbonate. By examining differences in mean square radial displacement and lattice spacing values obtained for bulk Sr(NO3)2 as compared to Sr(NO3)2 formed on SrCO3, EXAFS proves effective as a tool for investigating the local structure and composition of heterogeneous aerosol particles. The implications of findings on reacted strontium carbonate for atmospheric models of calcium carbonate aerosol are discussed.

Bramante,J.; Hinrichs, R.; Brown, E.; Calvin, S.

2007-01-01

359

Measurement of atmospheric boundary layer based on super-large-scale particle image velocimetry using natural snowfall  

NASA Astrophysics Data System (ADS)

We present an implementation of super-large-scale particle image velocimetry (SLPIV) to characterize spatially the turbulent atmospheric boundary layer using natural snowfall as flow tracers. The SLPIV technique achieves a measurement area of ~22 m × 52 m, up to 56 m above the ground, with a spatial resolution of ~0.34 m. The traceability of snow particles is estimated based on their settling velocity obtained from the wall-normal component of SLPIV velocity measurements. The results are validated using coincident measurements from sonic anemometers on a meteorological tower situated in close proximity to the SLPIV sampling area. A contrast of the mean velocity and the streamwise Reynolds stress component obtained from the two techniques shows less than 3 and 12 % difference, respectively. Additionally, the turbulent energy spectra measured by SLPIV show a similar inertial subrange and trends when compared to those measured by the sonic anemometers.

Toloui, M.; Riley, S.; Hong, J.; Howard, K.; Chamorro, L. P.; Guala, M.; Tucker, J.

2014-05-01

360

Heterogeneous Reactions of NO3 Radicals With Polycyclic Aromatic Hydrocarbons and Alkane Monolayers as Proxies for Particles in the Atmosphere  

NASA Astrophysics Data System (ADS)

The nitrate radical NO3 is an important nighttime oxidant in the troposphere, especially in polluted urban areas. While homogeneous gas-phase reactions of NO3 with organic substances of atmospheric importance have been studied in detail, little research has focused on heterogeneous reactions of NO3 with atmospheric organic particles. As reaction rates, products, and mechanisms can be very different in heterogeneous reactions compared to the corresponding homogeneous reactions, there is a need for investigations on these heterogeneous processes. Reactions on atmospheric particulate matter can also have a major effect on important properties of aerosol particles (e.g. hydrophilicity, toxicity, and optical properties). Polycyclic aromatic hydrocarbons (PAHs) are atmospheric pollutants that result from incomplete combustion processes. Due to their abundance and toxicity, they are of high scientific interest. To gain insight into heterogeneous reactions of this class of compounds, solid films of four different PAHs were exposed to gas phase NO3 radicals using a flow tube reactor coupled to a chemical ionization mass spectrometer. The reactive uptake coefficient ? of these reactions was determined. Results show a very fast reaction of NO3 with PAHs (pyrene and fluoranthene: ? ? 0.2, benz[a]anthracene: ? = 0.06 ± 0.01) while reactions of N2O5, O3, NO2, and HNO3 with PAH surfaces are significantly slower (e.g. for pyrene + O3 ? ? 1.4 × 10-6). Although atmospheric concentrations of NO3 are lower compared to the other gas phase oxidants studied, NO3 heterogeneous reactions are still more important for the oxidation of PAHs in atmospheric particulate matter due to the higher reactivity of NO3. Self assembled monolayers (SAMs) are frequently used as model substrates for organic aerosol surfaces. To study heterogeneous reactions of alkane surfaces, a SAM of octadecanethiol on a gold substrate was exposed to NO3 radicals. Surface products were studied using X-ray photoelectron spectroscopy (XPS). No volatilization or destruction of the SAM was detected using XPS. Formation of hydroxyl-, carbonyl-, and carboxylic functional groups was observed.

Gross, S.; Knopf, D. A.; Mak, J.; Bertram, A. K.

2006-12-01

361

Prediction of material strength and fracture of glass using the SPHINX smooth particle hydrodynamics code  

SciTech Connect

The design of many military devices involves numerical predictions of the material strength and fracture of brittle materials. The materials of interest include ceramics, that are used in armor packages; glass that is used in truck and jeep windshields and in helicopters; and rock and concrete that are used in underground bunkers. As part of a program to develop advanced hydrocode design tools, the authors have implemented a brittle fracture model for glass into the SPHINX smooth particle hydrodynamics code. The authors have evaluated this model and the code by predicting data from one-dimensional flyer plate impacts into glass, and data from tungsten rods impacting glass. Since fractured glass properties, which are needed in the model, are not available, the authors did sensitivity studies of these properties, as well as sensitivity studies to determine the number of particles needed in the calculations. The numerical results are in good agreement with the data.

Mandell, D.A.; Wingate, C.A.

1994-08-01

362

Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction  

NASA Astrophysics Data System (ADS)

This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20 L stainless-steel chamber and exposed to ozone. The materials included expanded polystyrene, a natural rubber adhesive, cedar board, Japanese Cyprus board and silver fir board, as well as d-limonene, which is a known constituent of certain woods and cleaning products. The combination of ozone and either d-limonene, cedar board or cypress board produced sub-micron particles, with most of the increase occurring in the size range of 0.01- 0.5?m diameter. This was not observed for the other materials. In the case of cedar board, the consequence of ozone exposure over an extended time interval was monitored. As the exposure time elapsed, the concentration of sub-micron particles moderately decreased. In the second set of experiments, unwaxed or waxed plastic tiles were placed in the 20 L chamber and exposed to ozone. Sub-micron particles and organic compounds were measured during the course of the experiments. In the case of the waxed tile, the number of 0.01- 1.0?m size particles grew about 50×108particlesm-3; particle growth was significantly less for the un-waxed tile. For both the waxed and un-waxed tiles, the emission rates of heptane, nonane, nonanal, and decanal increased after ozone was added to the supply air. (However, it is not clear if some or all of this production was due to ozone reacting with the sorbent used for sampling or with compounds captured by the sorbent.) This study provides further evidence that ozone-initiated reactions with building materials can be a significant source of both sub-micron particles and secondary organic compounds in indoor environments.

Aoki, Taisuke; Tanabe, Shin-ichi

363

Responses of the Jovian Atmosphere to Cometary Particles and Photon Impacts  

NASA Technical Reports Server (NTRS)

Spectra of soft x-ray and EUV emissions of oxygen ions, precipitating into the Jovian atmosphere, are calculated, taking into account the dynamical character of the energy and charge distributions of the ions as they propagate. Monte-Carlo simulations are performed using experimental and theoretical cross sections of ion collisions with the atmospheric gases. The numbers of x-ray and EUV photons produced per precipitating oxygen ion are calculated as functions of the initial ion energy and charge. The energy and charge distribution functions are used to evaluate the intensities of characteristic x-ray and EUV spectral emission lines of oxygen ions in the Jovian aurora.

Dalgarno, A.

1998-01-01

364

Generation of Internally Mixed Insoluble and Soluble Aerosol Particles to Investigate the Impact of Atmospheric Aging and Heterogeneous Processing on the CCN Activity of Mineral Dust Aerosol  

Microsoft Academic Search

Heterogeneous reactions of trace gases with mineral dust aerosol not only impact the chemical balance of the atmosphere but also the physicochemical properties of the dust particle and the ability of the particle to act as a cloud condensation nuclei (CCN). Recent field studies have shown that carbonate minerals are preferentially associated with nitrates whereas aluminum silicates (i.e., clay minerals)

Elizabeth R. Gibson; Kelly M. Gierlus; Paula K. Hudson; Vicki H. Grassian

2007-01-01

365

Characterization of Atmospheric Pressure Plasma Torch and the Surface Interaction for Material Removal  

NASA Astrophysics Data System (ADS)

An atmospheric pressure plasma torch has been developed and characterized for removal of organic based coatings. The focus of the Strategic Environmental Research & Development Program (SERDP) project WP-1762, that funded the bulk of this dissertation work, is removal of paint from US Navy vessels. The goal is to develop a novel technology for coating removal that is capable of reducing the amount of environmental waste produced during the commonly used grit blasting process. The atmospheric pressure air plasma torch was identified as having the capacity to remove the paint systems while using only compressed air and electricity as a media-less removal system with drastically reduced waste generation. Any improvements to the existing technology need to be based on scientific knowledge and thus the plasma removal mechanisms or material warranted investigation. The removal of material does not show a strong relation to the plasma parameters of power, frequency, and gas flow, nor is there a strong relation to the presences of inorganic fillers impeding or altering the removal rates. The underlying removal mechanisms also do not show a strong correlation to the rotational temperature of the plasma but do show a strong correlation to the optical emission intensity. Primarily, the emission from atomic oxygen and molecular nitrogen were identified significant contributors and were investigated further. The plasma feed gas was then varied from the nitrogen and oxygen ratio present in ambient air to pure nitrogen to identify the effect of oxygen on the removal mechanism. From these experiments it was concluded that the oxygen present in air does contribute to the overall removal mechanism; however, it is not the sole contributing factor with the other major factor being nitrogen.

McWilliams, Anthony Joseph

366

A Carbon Source Apportionment Shift in Mexico City Atmospheric Particles During 2003-2004 as Determined with Stable Carbon Isotopes  

NASA Astrophysics Data System (ADS)

The stable carbon isotope composition of atmospheric particles (PM2.5) was measured at La Merced (MER), a commercial site in the eastern sector, and at Xalostoc (XAL) an industrial site in the NE sector of Mexico City, during three sampling periods in autumn 2003, and spring and autumn 2004. At each site and sampling campaign particle samples were collected daily with minivol samplers during two week periods. Ancillary data included organic and elemental carbon, trace elements and ionic species. This data base was complement with air quality data from the RAMA (Automatic Atmospheric Monitoring Network). In general, particle concentrations, ionic species and some air quality species showed higher concentrations in autumn and lowest values in spring. Moreover, the concentrations of these chemical species were highest at XAL compared to MER. The stable carbon isotope composition of PM2.5 during autumn 2003 and spring 2004 had and average value of -26.04 (± 1.54) ‰ vs. PDB. Differences in the isotopic composition between the two sites were non significant. The average ?13C during these seasons were 1 ‰ lighter relative to data collected previously at these sites during 2000 and 2001, and is consistent with a predominant source of hydrocarbon combustion. In autumn 2004, however, average ?13C at XAL and MER increased to -22.8 (± 0.9) and -20.6 (± 3.1) ‰, respectively. Organic carbon concentrations during this period increased concomitantly at these sites. The shift in the isotopic composition in ambient particles suggests a predominance of soil-derived carbon during this period. The possible causes and implications of this are discussed.

Lopez-Veneroni, D. G.; Vega, E.

2013-05-01

367

LEVOGLUCOSAN, A TRACER FOR CELLULOSE IN BIOMASS BURNING AND ATMOSPHERIC PARTICLES. (R823990)  

EPA Science Inventory

Abstract The major organic components of smoke particles from biomass burning are monosaccharide derivatives from the breakdown of cellulose, accompanied by generally lesser amounts of straight-chain, aliphatic and oxygenated compounds and terpenoids from vegetation wa...

368

mu-Scale Variations Of Elemental Composition In Individual Atmospheric Particles By Means Of Synchrotron Radiation Based mu-XRF Analysis  

SciTech Connect

Atmospheric pollution poses a huge challenge especially for densely populated urban areas. Although a tremendous knowledge already exists on atmospheric particulate pollution, only very limited knowledge is available on mineral and chemical composition of single atmospheric particles because most studies on air pollution focus on total mass concentrations or bulk elemental analysis. However, it is of particular importance to investigate the properties of single particles since according to their individually composition they differ in their specific impact on climate change, negative environment and health effects, as well as accelerating the weathering of stone buildings in urban areas. Particles with sulfate and nitrate coatings together with sufficient moisture increase metal solubility and possibly catalyze further surface reactions on stone facades of buildings. From the viewpoint of health effects of aerosols it is important to consider agglomerations processes of fine anthropogenic and highly toxic particles with coarse geogenic and less toxic particles. With respect to fundamental research in mineralogy, processes forming composed coarse particles consisting of geogenic and anthropogenic substances are valuable to study since a new type of particle is produced. In this context, the important and still in detail unknown role of geogenic particles as catchers for anthropogenic aerosols can be investigated more closely. Coarse particles can provide a possible sink for fine particles. Moreover, the intermixture of particles from geogenic and anthropogenic sources and the spatial and temporal variations of contributions from different sources, which plays a decisive role in the study area of Beijing, can be clarified with this approach. For this study, particles were collected with the passive sampling device Sigma-2 and analyzed for particles from 3 to 96 {mu}m. The analyzed particles showed a very inhomogeneous distribution in their elemental composition. For this study, synchrotron radiation based mu-X-ray fluorescence analysis (mu-SXRF) proved to be an excellent tool to investigate mu-scalic distributions of main and trace element concentrations within individual airborne particles.

Schleicher, N.; Kramar, U. [Institute of Mineralogy and Geochemistry, Universitaet Karlsruhe (Thailand), Adenauerring 20, 76131 Karlsruhe (Germany); Norra, S. [Institute of Geography and Geoecology, Universitaet Karlsruhe (Thailand), Kaiserstr. 12, 76128 Karlsruhe (Germany); Dietze, V.; Kaminski, U. [Research Center Human Biometeorology, Air Quality Department, Deutscher Wetterdienst, Stefan-Meier-Str. 4, 79104 Freiburg i. Br. (Germany); Cen, K.; Yu, Y. [Department of Geology and Mineral Resources, Chinese University of Geosciences, Xueyuan Road 29, Beijing 100083 (China)

2010-04-06

369

Atmosphere Expansion and Mass Loss of Close-orbit Giant Exoplanets Heated by Stellar XUV. I. Modeling of Hydrodynamic Escape of Upper Atmospheric Material  

NASA Astrophysics Data System (ADS)

In the present series of papers we propose a consistent description of the mass loss process. To study in a comprehensive way the effects of the intrinsic magnetic field of a close-orbit giant exoplanet (a so-called hot Jupiter) on atmospheric material escape and the formation of a planetary inner magnetosphere, we start with a hydrodynamic model of an upper atmosphere expansion in this paper. While considering a simple hydrogen atmosphere model, we focus on the self-consistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to an investigation of the role of the specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free and restricted flow) are formed. A comparative study is performed of different processes, such as X-ray and ultraviolet (XUV) heating, material ionization and recombination, H_3^ + cooling, adiabatic and Ly? cooling, and Ly? reabsorption. We confirm the basic consistency of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we determine that, under the typical conditions of an orbital distance of 0.05 AU around a Sun-type star, a hot Jupiter plasma envelope may reach maximum temperatures up to ~9000 K with a hydrodynamic escape speed of ~9 km s–1, resulting in mass loss rates of ~(4-7) · 1010 g s–1. In the range of the considered stellar-planetary parameters and XUV fluxes, that is close to the mass loss in the energy-limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the follow-up paper (Paper II).

Shaikhislamov, I. F.; Khodachenko, M. L.; Sasunov, Yu. L.; Lammer, H.; Kislyakova, K. G.; Erkaev, N. V.

2014-11-01

370

28th International Cosmic Ray Conference 1627 Composition of cosmic ray particles in the atmosphere as  

E-print Network

has been emphasized in connection to the atmospheric neutrino obser- vations performed by underground they are compared. One of the main sources of inaccuracies is the model used in the simulations to reproduce. The apparatus consisted of a superconducting magnet spectrometer, a timeĀ­ofĀ­flight device, a gas ring imaging

Morselli, Aldo

371

PARTICLE-ASSOCIATED POLYCYCLIC AROMATIC HYDROCARBONS IN THE ATMOSPHERE OF HONG KONG  

E-print Network

high volume air samplers were identified using GC-MS (gas chromatography-mass spectrometry(k)fluoranthene was more significant in autumn and winter. Keywords: atmospheric aerosols, gas chromatography-mass predominantly from pyrolysis, incomplete com- bustion and carbonization processes. Even in Antarctica, PAHs

Zheng, Mei

372

Particle-in-cell and global simulations of ? to ? transition in atmospheric pressure Penning-dominated capacitive discharges  

NASA Astrophysics Data System (ADS)

Atmospheric pressure radio-frequency (rf) capacitive micro-discharges are of interest due to emerging applications, especially in the bio-medical field. A previous global model did not consider high-power phenomena such as sheath multiplication, thus limiting its applicability to the lower power range. To overcome this, we use one-dimensional particle-in-cell (PIC) simulations of atmospheric He/0.1% N2 capacitive discharges over a wide range of currents and frequencies to guide the development of a more general global model which is also valid at higher powers. The new model includes sheath multiplication and two classes of electrons: the higher temperature ‘hot’ electrons associated with the sheaths, and the cooler ‘warm’ electrons associated with the bulk. The electric field and the electron power balance are solved analytically to determine the time-varying hot and warm temperatures and the effective rate coefficients. The particle balance equations are integrated numerically to determine the species densities. The model and PIC results are compared, showing reasonable agreement over the range of currents and frequencies studied. They indicate a transition from an ? mode at low power characterized by relatively high electron temperature Te with a near uniform profile to a ? mode at high power with a Te profile strongly depressed in the bulk plasma. The transition is accompanied by an increase in density and a decrease in sheath widths. The current and frequency scalings of the model are confirmed by the PIC simulations.

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Chabert, P.; Lazzaroni, C.

2014-06-01

373

Seasonal variation of source contributions to atmospheric fine and coarse particles at suburban area in Istanbul, Turkey  

SciTech Connect

Daily samples of fine (PM2.5) and coarse (PM2.5-10) particles were collected from July 2002 to July 2003 to provide a better understanding of the elemental concentration and source contribution to both PM fractions. Sampling location represents suburban part of Istanbul metropolitan city. Samples were collected on Teflon filters using a 'Dichotomous Sampler.' Concentrations of Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V, and Zn were measured by GFAAS, FAAS, and FAES techniques. Elemental variations of heating and nonheating seasons were discussed. Fossil fuel-related atmospheric metals dramatically increased during the heating season, while natural originated atmospheric metals increased during the nonheating season. Seasonal variations of source contributions were evaluated using factor analysis, which was separately applied to the collected fine and coarse particles data sets during heating and nonheating seasons (four data sets: PM2.5 heating, PM2.5 nonheating, PM2.5-10 heating, and PM2.5-10 nonheating). Significant seasonal differences in source contributions were observed. Four factor groups were extracted for PM2.5 dataset during the nonheating season, while five factor groups were extracted for all the other cases. Mineral dust transportation, traffic, and industry-related activities were classified as different factor groups in all the cases.

Karaca, F.; Alagha, O.; Erturk, F.; Yilmaz, Y.Z.; Ozkara, T. [Fatih University, Istanbul (Turkey). Dept. for Environmental Engineering

2008-06-15

374

Seasonality and interspecies differences in particle/gas partitioning of PAHs observed by the Integrated Atmospheric Deposition Network (IADN)  

NASA Astrophysics Data System (ADS)

This study presents partitioning data from eight locations in the Laurentian Great Lakes region collected by the Integrated Atmospheric Deposition Network (IADN) over periods ranging from 1 to 6 years. Particle/gas partitioning varies sufficiently between sites in the Great Lakes region to preclude the use of a uniform temperature dependence for its description. Site-specific parameters for describing partitioning as a function of inverse