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1

Sources and Properties of Organic Material in Aqueous Atmospheric Aerosol Particles  

NASA Astrophysics Data System (ADS)

We have observed the formation of high-molecular-weight and light-absorbing secondary organic aerosol material in mildly acidic aqueous mixtures of 1,2-dicarbonyls and inorganic salts meant to mimic the composition of aqueous aerosols. The organics studied include the VOC oxidation products glyoxal, methylglyoxal, oxalic acid, and mixtures thereof. The solutions studied were saturated in the salt of interest, and the concentration of organics in the mixture was maintained at 1-10% of the solute mass, consistent with ambient aerosol composition. The product mixtures were characterized using UV-Vis spectrophotometry, MALDI-MS, and pendant drop tensiometry. The results suggest a mechanism involving the participation of the ammonium ion. Kinetics studies show that substantial product formation occurs within hours. If these products form in atmospheric aerosol particles, they could change the radiative properties of the seed aerosol over its lifetime in the atmosphere.

McNeill, V.

2009-05-01

2

The atmosphere as particle detector  

NASA Astrophysics Data System (ADS)

The possibility of using an inflatable, gas-filled balloon as a TeV gamma-ray detector on the moon is considered. By taking an atmosphere of Xenon gas there, or by extracting it on the moon, a layman's detector design is presented. In spite of its shortcomings, the exercise illustrates several of the novel features offered by particle physics on the moon.

Stanev, T.

1990-03-01

3

Phase Transitions of Aqueous Atmospheric Particles  

NASA Astrophysics Data System (ADS)

The physical state of atmospheric particles affect their optical properties, their chemical reactivity, and their atmospheric lifetime. Accordingly, the prediction of particle phase is critical for accurate atmospheric modeling. Atmospheric aqueous particles, due to their small size (submicron), can deeply supercool with respect to freezing (e.g., 40 K) and deeply supersaturate (e.g., S = 35) with respect to relative humidity before crystallization begins via homogeneous nucleation. Atmospheric mineral dusts, incorporated as inclusions within aqueous particles, provide active surfaces to induce crystallization heterogeneously and thus drastically reduce the extent of supercooling (e.g., 20 K) or supersaturation (e.g., S = 5). This talk will present laboratory and theoretical work on several systems, including sulfates, nitrates, and mineral dusts. The results are crucial to providing a quantitative microphysical model that couples the interactions of these particle classes in the atmosphere.

Martin, S. T.

2001-12-01

4

Phase Transitions of Aqueous Atmospheric Particles  

NASA Astrophysics Data System (ADS)

The physical state of atmospheric particles affect their optical properties, their chemical reactivity, and their atmospheric lifetime. Accordingly, the prediction of particle phase is critical for accurate atmospheric modeling. Atmospheric aqueous particles, due to their small size (submicron), can deeply supercool with respect to freezing (e.g., 40 K) and deeply supersaturate (e.g., S = 35) with respect to relative humidity before crystallization begins via homogeneous nucleation. This talk will present laboratory work on several systems, including sulfates, nitrates, and mineral dusts. The results are crucial to providing a quantitative microphysical model that couples the interactions of these particle classes in the atmosphere. Modeling work on the implications of phase transitions for radiative forcing will also be presented.

Martin, S. T.; Hung, H.

2002-12-01

5

Degradation of materials in the atmosphere  

SciTech Connect

This paper provides a perspective on the potential for materials degradation as a consequence of atmospheric exposure. Ferrous metals, masonry, zinc, copper, and perhaps some paints appear most likely to be degraded. The regimes of greatest concern vary with different materials, but they include dew, fog, airborne particles, and indoor air. The results, however, rest on a rather sparse data base and take no account of synergistic deterioration effects of corrodents; thus, the presentation should be considered a starting point for discussion and experimentation.

Graedel, T.E.; R. McGill

1986-11-01

6

Particle Formation (Nucleation) in the Martian Atmosphere  

NASA Astrophysics Data System (ADS)

We have studied ice particle formation via heterogeneous nucleation in the present atmospheric conditions of Mars for both one-component (water OR carbon dioxide) and two-component (water AND carbon dioxide) cases.

Määttänen, A.; Vehkamäki, H.; Lauri, A.; Napari, I.; Merikallio, S.; Kauhanen, J.; Savijärvi, H.; Kulmala, M.

2006-10-01

7

The Effects of Atmospheric Particles on Climate  

NSDL National Science Digital Library

This video segment produced by ThinkTV explains that particles suspended in the atmosphere, or aerosols, can have a surprising effect on regional warming and cooling, adding to the complexity of global climate change.

Thinktv

2010-11-30

8

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

9

Meteoritic material in stratospheric particles  

NASA Astrophysics Data System (ADS)

About half of the sulfuric acid particles in the lower stratosphere contain a few percent by mass of elements derived from ablation of meteoroids. Detailed particle data suggest that some elements such as magnesium and iron are dissolved in the sulfuric acid particles whereas other elements such as aluminum and silicon are present as solid inclusions. The uniformity of composition from particle to particle confirms that diffusion in the mesosphere rapidly mixes material ablated from different meteoroid grains. Stratospheric aerosols rule out some of the highest and lowest estimates of the meteoric mass flux.

Murphy, D. M.; Froyd, K.; Cziczo, D. J.

2013-12-01

10

Alternative pathway for atmospheric particles growth  

PubMed Central

Credible climate change predictions require reliable fundamental scientific knowledge of the underlying processes. Despite extensive observational data accumulated to date, atmospheric aerosols still pose key uncertainties in the understanding of Earth’s radiative balance due to direct interaction with radiation and because they modify clouds’ properties. Specifically, major gaps exist in the understanding of the physicochemical pathways that lead to aerosol growth in the atmosphere and to changes in their properties while in the atmosphere. Traditionally, the driving forces for particle growth are attributed to condensation of low vapor pressure species following atmospheric oxidation of volatile compounds by gaseous oxidants. The current study presents experimental evidence of an unaccounted-for new photoinduced pathway for particle growth. We show that heterogeneous reactions activated by light can lead to fast uptake of noncondensable Volatile Organic Compounds (VOCs) at the surface of particles when only traces of a photosensitizer are present in the seed aerosol. Under such conditions, size and mass increase; changes in the chemical composition of the aerosol are also observed upon exposure to volatile organic compounds such as terpenes and near-UV irradiation. Experimentally determined growth rate values match field observations, suggesting that this photochemical process can provide a new, unaccounted-for pathway for atmospheric particle growth and should be considered by models.

Monge, Maria Eugenia; Rosen?rn, Thomas; Favez, Olivier; Muller, Markus; Adler, Gabriela; Abo Riziq, Ali; Rudich, Yinon; Herrmann, Hartmut; George, Christian; D'Anna, Barbara

2012-01-01

11

Particle Size Distributions in Atmospheric Clouds  

NASA Technical Reports Server (NTRS)

In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

Paoli, Roberto; Shariff, Karim

2003-01-01

12

Phase of atmospheric secondary organic material affects its reactivity.  

PubMed

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

2012-10-23

13

Characterization of Atmospheric Organic Nitrates in Particles  

NASA Astrophysics Data System (ADS)

Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ń-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

2008-12-01

14

Methodology for the Isolation and Characterization of Individual Plutonium-Bearing Particles in Atmospheric Effluents from a Nuclear Processing Plant.  

National Technical Information Service (NTIS)

A method for isolating and characterizing individual particles containing fissionable materials is described. Polycarbonate membrane filters are used to collect the particles from atmospheric effluents from a nuclear processing plant. Collected particles ...

S. M. Sanders

1977-01-01

15

Teaching Materials: Stellar Atmospheres/Radiative Transfer  

NASA Astrophysics Data System (ADS)

We will present a selection of modern teaching materials for courses in Stellar Atmospheres and Radiative Transfer that have been collected from a wide variety of sources. We will provide brief synopses of each book, or set of of notes, and endeavor to compare and contrast the different presentations of the material. One of the newer additions to the literature is ``Radiative Transfer in Stellar Atmospheres,'' lecture notes from R.J. Rutten based on courses taught at Utrecht University. In addition, I. Hubeny and D. Mihalas presently are writing a new edition of Mihalas' famous ``Stellar Atmospheres.'' Other books we are aware of range from the planning stages to near completion. We will emphasize the diversity of styles and presentation techniques, but will try to make clear the central themes around which any successful Stellar Atmospheres/Radiative Transfer course must be built.

Hawley, S. L.; Ayres, T. R.

1996-05-01

16

Chemistry and composition of atmospheric aerosol particles.  

PubMed

For more than two decades a cadre of physical chemists has focused on understanding the formation processes, chemical composition, and chemical kinetics of atmospheric aerosol particles and droplets with diameters ranging from a few nanometers to ?10,000 nm. They have adapted or invented a range of fundamental experimental and theoretical tools to investigate the thermochemistry, mass transport, and chemical kinetics of processes occurring at nanoscale gas-liquid and gas-solid interfaces for a wide range of nonideal, real-world substances. State-of-the-art laboratory methods devised to study molecular spectroscopy, chemical kinetics, and molecular dynamics also have been incorporated into field measurement instruments that are deployed routinely on research aircraft, ships, and mobile laboratories as well as at field sites from megacities to the most remote jungle, desert, and polar locations. These instruments can now provide real-time, size-resolved aerosol particle physical property and chemical composition data anywhere in Earth's troposphere and lower stratosphere. PMID:22404591

Kolb, Charles E; Worsnop, Douglas R

2012-01-01

17

Material shields against neutral atomic particle beams  

Microsoft Academic Search

A material shield designed to protect a spacecraft against an atomic particle beam will, of necessity, be quite massive; consequently, even modest fractional-weight savings would be significant. With this goal in mind, the particle stopping power and range in various materials were investigated. The lightest shield materials are compounds composed of hydrogen and other light elements.

S. W. Kash

1985-01-01

18

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.

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

19

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

20

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

21

Dust and Sputtered Particle Streams in Cometary Atmosphere  

NASA Technical Reports Server (NTRS)

Dynamics of dust particles in a comet atmosphere was investigated using Monte-Carlo simulation method taking into account radiation and gravitational forces applied to the particles. The model distribution function found out in VEGA experiments was chosen for calculations. Dust particles with masses more then 10(exp -10) g were considered. The delay effect for the big mass particles is shown. In this paper the boundary distribution function for sputtered particles drifting off the surface was determined using Nochilla's model. General dependences for the normal component of the relative mass velocity of sputtered particles are given as the function of particle energy normalized by Tomas-Fermi energy.

Svirschevsky, Stanislav B.

1996-01-01

22

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

23

Energetic particle precipitation in the atmosphere of Mars  

NASA Astrophysics Data System (ADS)

The main sources of ionization in the atmosphere of Mars are the precipitating particles: photons (EUV-XUV), electrons, protons and cosmic rays (galactic or solar). Characterizing the reaction of the Martian atmosphere to these inputs helps understanding the observed variations of the upper atmosphere density and, more generally, the evolution of the atmosphere. We have modeled the ion and excited state species production in the atmosphere of Mars due to these particles using the Aeroplanets model, recently upgraded to take into account the low energy proton precipitation. Using the precipitation spectra from different Martian probes, we modeled the response for several conditions of proton and electron precipitation. We also modeled the ionization due to the cosmic rays at the ground.

Gronoff, G.; Simon Wedlund, C.; Mertens, C. J.; Norman, R. B.

2012-12-01

24

Evaluation of energetic particle effects on BUV data and atmospheric ozone  

NASA Technical Reports Server (NTRS)

To aid investigations of energetic particle effects on the backscattered ultraviolet (BUV) instrumentation aboard Nimbus 4, solar proton events characterized as polar cap absorption events occurring in the period April 1970 to April 1976 were summarized. Energetic particle effects on total ozone above the 4 mb pressure level measured by Nimbus 4 were analyzed. Proceedings of a workshop meeting of operation aurorozone are included as background material for possible effects of bremsstrahlung on atmospheric ozone.

Herman, J. R.

1977-01-01

25

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

26

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

27

Nanoporous Materials in Atmosphere Revitalization, Chapter 1.  

National Technical Information Service (NTIS)

Atmospheric Revitalization (AR) is the term the National Aeronautics and Space Administration (NASA) uses to encompass the engineered systems that maintain a safe, breathable gaseous atmosphere inside a habitable space cabin. An AR subsystem is a key part...

B. Luna C. Junaedi J. Hernandez-Maldonado J. L. Perry L. Mulloth R. G. Raptis S. Roychoudhury Y. Ishikawa

2012-01-01

28

Atmospheric New Particle Formation Enhanced by Organic Acids  

Microsoft Academic Search

Atmospheric aerosols often contain a substantial fraction of organic matter, but the role of organic compounds in new nanometer-sized particle formation is highly uncertain. Laboratory experiments show that nucleation of sulfuric acid is considerably enhanced in the presence of aromatic acids. Theoretical calculations identify the formation of an unusually stable aromatic acid-sulfuric acid complex, which likely leads to a reduced

Renyi Zhang; Inseon Suh; Jun Zhao; Dan Zhang; Edward C. Fortner; Xuexi Tie; Luisa T. Molina; Mario J. Molina

2004-01-01

29

Optical properties, morphology and elemental composition of atmospheric particles at T1 supersite on MILAGRO campaign  

NASA Astrophysics Data System (ADS)

Atmospheric particles were sampled at T1 supersite during MILAGRO campaign, in March 2006. T1 was located at the north of Mexico City (MC). Aerosol sampling was done by placing copper grids for Transmission Electron Microscope (TEM) on the last five of an 8-stage MOUDI cascade impactor. Samples were obtained at different periods to observe possible variations on morphology. Absorption and scattering coefficients, as well as particle concentrations (0.01-3 ?m aerodynamic diameter) were measured simultaneously using a PSAP absorption photometer, a portable integrating nephelometer, and a CPC particle counter. Particle images were acquired at different magnifications using a CM 200 Phillips TEM-EDAX system, and then calculated the border-based fractal dimension. Also, Energy Dispersive X-Ray Spectroscopy (EDS) was used to determine the elemental composition of particles. The morphology of atmospheric particles for two aerodynamic diameters (0.18 and 1.8 ?m) was compared using border-based fractal dimension to relate it to the other particle properties, because T1-generated particles have optical, morphological and chemical properties different from those transported by the MC plume. Particles sampled under MC pollution influence showed not much variability, suggesting that more spherical particles (border-based fractal dimension close to 1.0) are more common in larger sizes (d50 = 1.8 ?m), which may be attributed to aerosol aging and secondary aerosol formation. Between 06:00 and 09:00 a.m., smaller particles (d50 = 0.18 ?m) had more irregular shapes resulting in higher border-based fractal dimensions (1.2-1.3) for samples with more local influence. EDS analysis in d50 = 0.18 ?m particles showed high contents of carbonaceous material, Si, Fe, K, and Co. Perhaps, this indicates an impact from industrial and vehicle emissions on atmospheric particles at T1.

Carabali, G.; Mamani-Paco, R.; Castro, T.; Peralta, O.; Herrera, E.; Trujillo, B.

2012-03-01

30

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

31

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

32

Single particle atmospheric aerosol analysis using digital holographic microscopy  

NASA Astrophysics Data System (ADS)

The aim of this research is to calculate the refractive index of transparent atmospheric aerosols, which have biological origin, using a digital holographic microscopy technique (DHM). The samples are collected on filters, using miniature impactors for particles with dimensions smaller than 10?m (on even one axis), from a height of over 20 meters, in Magurele, a rural location near the urban and industrial agglomeration of the capital city, Bucharest. Due to their organic or inorganic origin, each atmospheric aerosol particle has different size, shape and optical properties which have a determinant role in LIDAR measurements. We record on a CCD camera hundreds of holograms which contain the diffraction pattern from every aerosol particle superposed with the reference wave. Digitally, we scan the entire volume of one particle with nanometric resolution (using an algorithm based on the Fresnel approximation). The calibration was done using an object with known dimensions fabricated by e-beam lithography and some complementary measurements were done in confocal microscopy. Our analysis separates four main classes of atmospheric aerosols particles (wires, columns, spherical fragments, and irregular). The predominant class in the investigated period is the first one, which has biological origin and the refractive index was calculated starting from the phase shift introduced by them in the optical path and models for their cylindrical shape. The influence of spatial filtering in the reconstructed object images was investigated.

Mihailescu, Mona; Cojocaru, Ruxandra Elena; Kusko, C.; Toanca, Flori; Dinescu, A.; Schiopu, P.

2011-05-01

33

Black carbon particles in the urban atmosphere in Beijing  

NASA Astrophysics Data System (ADS)

A study of the concentration of black carbon particles and its variation in the urban atmosphere has been carried out since 1996 in the Beijing area. The measurements were done in the late autumn and early winter each year, the period before and after domestic heating activities begin. The results show the presence of black carbon particles at the high level that vary over a large range in the urban atmosphere in Beijing. The mean value of daily average concentration for the whole observation period of 1996 2004 is 20.0 ?g m-3. An evident decrease of black carbon particle concentration in the Beijing area is observed after 2000, and the daily average concentration of black carbon particles is estimated to be 16.0 ?g m-3 with a variation range of 2.10 50.50 ?g m-3 for the period of 2000 2004. The observation method and main variation behavior characteristics of black carbon particles in the urban atmosphere in the Beijing area are given and discussed.

Wang, Gengchen; Bai, Jianhui; Kong, Qinxin; Emilenko, Alexander

2005-09-01

34

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

35

Observation of nitrate coatings on atmospheric mineral dust particles  

NASA Astrophysics Data System (ADS)

Nitrate compounds have received much attention because of their ability to alter the hygroscopic properties and cloud condensation nuclei (CCN) activity of mineral dust particles in the atmosphere. However, very little is known about specific characteristics of ambient nitrate-coated mineral particles on an individual particle scale. In this study, sample collection was conducted during brown haze and dust episodes between 24 May and 21 June 2007 in Beijing, northern China. Sizes, morphologies, and compositions of 332 mineral dust particles together with their coatings were analyzed using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) microanalyses. Structures of some mineral particles were verified using selected-area electron diffraction (SAED). TEM observation indicates that approximately 90% of the collected mineral particles are covered by visible coatings in haze samples whereas only 5% are coated in the dust sample. 92% of the analyzed mineral particles are covered with Ca-, Mg-, and Na-rich coatings, and 8% are associated with K- and S-rich coatings. The majority of coatings contain Ca, Mg, O, and N with minor amounts of S and Cl, suggesting that they are possibly nitrates mixed with small amounts of sulfates and chlorides. These nitrate coatings are strongly correlated with the presence of alkaline mineral components (e.g., calcite and dolomite). CaSO4 particles with diameters from 10 to 500 nm were also detected in the coatings including Ca(NO3)2 and Mg(NO3)2. Our results indicate that mineral particles in brown haze episodes were involved in atmospheric heterogeneous reactions with two or more acidic gases (e.g., SO2, NO2, HCl, and HNO3). Mineral particles that acquire hygroscopic nitrate coatings tend to be more spherical and larger, enhancing their light scattering and CCN activity, both of which have cooling effects on the climate.

Li, W. J.; Shao, L. Y.

2009-03-01

36

Material void opening computation using particle method  

SciTech Connect

When performing the calculation of material flow in two dimensional Eulerian coordinates, one always encounters the difficulties of modeling the void opening due to material failure such as fracture, spallation, or phase change. The present studies use one type of particle to represent the material and another type for the void space. According to the flow conditions, the void space may grow with crack propagation or may be recombined with the void space closed up when the volume decreases. The penetration of a copper rod into, and eventually through a steel plate, is calculated using the present code.

Lee, W.H.; Painter, J.W.

1988-01-01

37

Organic Compounds Evaporating from Building Materials into Indoor Atmosphere.  

National Technical Information Service (NTIS)

Volatile organic compounds evaporating from building materials produce odor to indoor atmosphere and may cause health hazards. The latest publications on organic compounds emitted by building and interior finish materials have been reviewed. These publica...

S. Jaemsae A. Kivistoe M. Ojala K. Saarela M. Waeaenaenen

1986-01-01

38

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

SciTech Connect

Atmospheric ice formation induced by particles with complex chemical and physical properties through heterogeneous nucleation is not well understood. Heterogeneous ice nucleation and water uptake by ambient particles collected from urban environments in Los Angeles and Mexico City are presented. Using a vapour controlled cooling system equipped with an optical microscopy, the range of onset conditions for ice nucleation and water uptake by the collected particles was determined as a function of temperature (200{273 K) and relative humidity with respect to ice (RHice) up to water saturation. Three distinctly different types of authentic atmospheric particles were investigated including soot particles associated with organics/inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn containing inorganic particles apportioned to anthropogenic 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 ne structure spectroscopy (STXM/NEXAFS). Above 230 K, signicant differences in water uptake and immersion freezing effciencies of the different particle types were observed. Below 230 K, the particles exhibited high deposition ice nucleation effciencies and formed ice at RHice values well below homogeneous ice nucleation limits. The data show that the chemical composition of these eld{collected particles plays an important role in determining water uptake and immersion freezing. Heterogeneous ice nucleation rate coeffcients, cumulative ice nuclei (IN) spectrum, and IN activated fraction for deposition ice nucleation are derived. The presented ice nucleation data demonstrate that anthropogenic and marine particles comprising of various chemical and physical properties exhibit distinctly different ice nucleation effciencies and can serve as effcient IN at atmospheric conditions typical for cirrus and mixed phase clouds. This indicates a potential link between human activities and cloud formation, and thus climate.

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

2012-09-25

39

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

Microsoft Academic Search

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 mum 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

Marsha A. Presley; Philip R. Christensen

2010-01-01

40

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

Microsoft Academic Search

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

Marsha A. Presley; Philip R. Christensen

2010-01-01

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

Atmospheric new particle formation enhanced by organic acids.  

PubMed

Atmospheric aerosols often contain a substantial fraction of organic matter, but the role of organic compounds in new nanometer-sized particle formation is highly uncertain. Laboratory experiments show that nucleation of sulfuric acid is considerably enhanced in the presence of aromatic acids. Theoretical calculations identify the formation of an unusually stable aromatic acid-sulfuric acid complex, which likely leads to a reduced nucleation barrier. The results imply that the interaction between organic and sulfuric acids promotes efficient formation of organic and sulfate aerosols in the polluted atmosphere because of emissions from burning of fossil fuels, which strongly affect human health and global climate. PMID:15178797

Zhang, Renyi; Suh, Inseon; Zhao, Jun; Zhang, Dan; Fortner, Edward C; Tie, Xuexi; Molina, Luisa T; Molina, Mario J

2004-06-01

44

Atmospheric observations of new particle growth and shrinkage  

NASA Astrophysics Data System (ADS)

In subtropical central Taiwan, a total of fourteen new particle formation (NPF) events were identified at four sites that represent urban, coastal, mountain and downwind area, respectively. Among them, there were five particle shrinkage events showing the grown particles shrank back to the smallest measureable size of ~10 nm, thereby creating a unique "arch-like" shape in the size distribution contour plot. The particle shrinkage rates ranged from 5.1 to 7.6 nm h-1. The corresponding particle volume losses suggest that a notable fraction of the condensable species that contributed to growth was semi-volatile. The particle shrinkage was related to strong atmospheric dilution, high ambient temperature and low relative humidity, thus favoring the evaporation of semi-volatile species from the particulate phase to the gas phase. Our observations show that the new particle growth could be a reversible process, in which the evaporating semi-volatile species are important for the growth of new particles to sizes of environmental health concerns.

Young, Li-Hao; Lee, Shan-Hu; Kanawade, Vijay P.; Hsiao, Ta-Chih; Lee, Yungling L.; Hwang, Bing-Fang; Liou, Yi-Jyun; Hsu, Hui-Tsung; Tsai, Perng-Jy

2013-05-01

45

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

46

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

47

Cohesive granular materials composed of nonconvex particles  

NASA Astrophysics Data System (ADS)

The macroscopic cohesion of granular materials made up of sticky particles depends on the particle shapes. We address this issue by performing contact dynamics simulations of 2D packings of nonconvex aggregates. We find that the macroscopic cohesion is strongly dependent on the strain and stress inhomogeneities developing inside the material. The largest cohesion is obtained for nearly homogeneous deformation at the beginning of unconfined axial compression and it evolves linearly with nonconvexity. Interestingly, the aggregates in a sheared packing tend to form more contacts with fewer neighboring aggregates as the degree of nonconvexity increases. We also find that shearing leads either to an isotropic distribution of tensile contacts or to the same privileged direction as that of compressive contacts.

Saint-Cyr, Baptiste; Radjai, Farhang; Delenne, Jean-Yves; Sornay, Philippe

2013-05-01

48

Water Absorption by Atmospheric Organic Particles: Evidence, Causes and Simulations  

NASA Astrophysics Data System (ADS)

The optical and chemical properties of atmospheric fine particles and their ability to act as cloud condensation nuclei depend strongly upon their affinity for water. Laboratory experiments have shown that water-soluble sulfates and nitrates, which are major inorganic components of atmospheric fine particles, absorb water in an amount proportional to water vapor pressure. Analogous information about the interactions between water and organics is lacking. Moreover, the molecular composition of atmospheric particulate organics remains poorly characterized; information on the molecular composition of the water-soluble fraction is particularly sparse. Here we first analyze concurrent observations of particle chemical composition and water content from a continental nonurban (Grand Canyon) and an urban (Los Angeles) location to determine whether the water content of atmospheric particles is influenced by the presence of organics. We find that the aggregate hygroscopic properties of inorganic particles are altered substantially when organics are also present. For the nonurban location, organics enhance water absorption by inorganics. For the urban location, on the other hand, the net effect of organics is to diminish water absorption of the inorganics. Second, we identify specific compounds that are likely to contribute to the water-soluble fraction by juxtaposing published observations regarding the extraction characteristics and the molecular composition of atmospheric particulate organics with compound-specific solubility and condensibility for a wide variety of organics. We find that water-soluble organics, which constitute a substantial fraction of the total organic mass, include C2 to C7 multifunctional compounds (e.g. diacids, polyols, amino acids). Third, towards developing a simulation capability, we (1) synthesize published laboratory data to evaluate the water absorption behavior of multifunctional oxygenated organic compounds; and (2) test the reliability of the UNIFAC method for estimating water activities of aqueous organic solutions. Laboratory data show that multifunctional oxygenated compounds can absorb water over the entire range of relative humidities. For a wide variety of compounds (e.g., glycols, dicarboxylic acids, keto acids) and a wide range of solute concentrations (0 to over 90% by wt), we find that in most cases, water activities can be estimated within approximately 15% error.

Saxena, Pradeep

49

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

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

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...

52

Investigations of organic and microbiological atmospheric ice nucleating particles (Invited)  

NASA Astrophysics Data System (ADS)

Measurements in a number of laboratory and field campaigns have offered the opportunity to compare and contrast ice nucleation by soil-and plant-based inorganic, organic, and microbiological particles versus ice nucleating particles (INP) actually sampled in the atmosphere. This presentation reviews these recent studies. Plants support sometimes prodigious populations of INA bacteria as well as fungi and other potential biological ice nucleating particles, such as fragments of plant tissues themselves. The means of release of plant-sourced INP to the atmosphere is not fully documented, but our recent studies have found clear cases of release of ice nuclei from disturbances such as rain, both in forests and over grasslands, and harvesting. Composition of such ice nuclei in air has been inferred at these times based on simultaneous measurements of ice nuclei and biological aerosols. At quiescent times, measurements of the labile fraction of ice nucleating particles in air over agricultural regions suggest that organic and possibly microbiological organisms dominate ice nuclei populations, but INA bacteria are only selective and modest contributors at the warmest activation temperatures. Our results therefore suggest the presence of a spectrum of biological and organic ice nucleating particles over land regions. The ice nucleating activity of mineral soils is well documented and the presence of these particles in air is certain on the basis of many measurement campaigns which identified mineral particles to represent up to half or more of ice nuclei sampled in parts of the free troposphere. Our recent measurements have also documented a clear organic ice nucleating particle source within arable, sagebrush, grassland and forest soils, a source that may dominate over the mineral ice nuclei in such soils. Investigations of their compositions will be described. These ice nuclei are strongly resistant to heat, and may represent a separate population and source compared to the labile ice nuclei found in air over agricultural regions. While these soil-based ice nuclei must at times be lofted into the free troposphere and may represent some proportion of carbonaceous ice nuclei detected via electron microscopy in previous ambient sampling, we have not presently directly confirmed the presence of these ice nuclei in ambient air. Depending on available time, results regarding organic contributions of ice nucleating particles from biomass burning and oceanic sources will also be discussed.

DeMott, P. J.; Hill, T. C.; Tobo, Y.; Prenni, A. J.; McMeeking, G. R.; Levin, E. J.; McCluskey, C.; Huffman, J. A.; Mason, R.; Bertram, A. K.; Kreidenweis, S. M.

2013-12-01

53

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

54

Particle size distributions in functionally graded materials fabricated by the centrifugal solid-particle method  

Microsoft Academic Search

The aim of this study is to examine the possibility of the gradual particle size distributions in the functionally graded material (FGM) fabricated by centrifugal solid-particle method. FGM tubes were fabricated from plaster\\/corundum model materials containing five different particle sizes. The particle size distributions were directly determined by the extraction of the particles from the plaster matrix. The results reveal

Yoshimi Watanabe; Akihiro Kawamoto; Koichi Matsuda

2002-01-01

55

Impacts of solar particle events on middle atmospheric chlorine compounds  

NASA Astrophysics Data System (ADS)

Solar particle events (SPEs) are well known sources of chemical perturbations in the middle atmosphere. A well-understood effect is the release of reactive NOx and HOx, and the subsequent destruction of ozone. Satellite measurements (HALOE, MIPAS, AURA-MLS) have shown that there is also chlorine activation in the stratosphere and mesosphere, and an increase of chlorine nitrate in the lower and middle stratosphere during SPEs. This cannot be explained by the NOx and HOx increase alone. Atmospheric models with standard parametrizations of NOx and HOx production due to SPEs fail to reproduce the magnitude of the observed chlorine disturbances. Numerical simulations using the University of Bremen ion chemistry (UBIC) model show a much better agreement with measurements if full negative ion chemistry is considered additionally to the NOx and HOx production. The UBIC results in combination with atmospheric models indicate that reactions of negative cluster ions can have a significant impact on the middle atmosphere's chlorine chemistry during SPEs. There is a transformation of HCl into active chlorine via anion cluster chemistry. Additionally, the release of O(1D) through N(2D) + O2 - NO + O(1D) has a considerable impact on chlorine species. Results of UBIC simulations for different SPEs (July 2000, October 2003, January 2005) are presented. They are compared with the observed changes of chlorine compounds - HCl, HOCl, ClO and ClONO2 - from the satellite instruments HALOE, MIPAS and AURA-MLS.

Winkler, Holger; Sinnhuber, Miriam; Wissing, Jan-Maik; Kallenrode, May-Britt; Stiller, Gabrielle; von Clarmann, Thomas; Funke, Bernd

2010-05-01

56

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

57

Chemistry of background atmospheric particles collected at Mauna Loa Observatory, Hawaii  

SciTech Connect

Mauna Loa Observatory, Hawaii, was selected as a remote northern hemisphere site from which to collect atmospheric particles for chemical analyses of background aerosols in the free troposphere of the northern hemisphere. An automatic digital sampling controller was designed and installed at this site to aid in the isolation of uncontaminated particles of the free troposphere, based on wind direction and speed, time-of-day and particle characteristics at the observatory. The three primary components measured on these background particles between 1979 and 1982 were sulfates, continentally derived crustal material and marine particles with average geometric mean concentrations of 240 ng/m/sup 3/, and 15 ng/m/sup 3/, respectively, during the months of July to mid-February. Other months showed a ten-fold increase in continental crustal material, geometric avg = 730 ng/m/sup 3/, (which has been traced to Asian deserts) and doubling of sulfate mass to 480 ng/m/sup 3/ while the marine mass showed no significant changes. The average geometric mean concentration of local basalt was determined to be 15 ng/m/sup 3/ in down-slope winds and, thus, does not represent a major interference to most studies at MLO as a majority of the crustal dust in the atmosphere, even in relatively clean periods, is transported over thousands of kilometers to the islands from continents surrounding the Pacific Ocean.

Parrington, J.R.

1984-01-01

58

Ignition of a Combustible Atmosphere by Incandescent Carbon Wear Particles  

NASA Technical Reports Server (NTRS)

A study was made to determine whether carbon wear particles from carbon elements in sliding contact with a metal surface were sufficiently hot to cause ignition of a combustible atmosphere. In some machinery, electric potential differences and currents may appear at the carbon-metal interface. For this reason the effect of these voltages and currents on the ability of carbon wear particles to cause ignition was evaluated. The test specimens used in the investigation were carbon vanes taken from a fuel pump and flat 21-inch-diameter 2 metal disks (440-C stainless steel) representing the pump housing. During each experiment a vane was loaded against a disk with a 0.5-pound force, and the disk was rotated to give a surface speed of 3140 feet per minute. The chamber of the apparatus that housed the vane and the disk was filled with a combustible mixture of air and propane. Various voltages and amperages were applied across the vane-disk interface. Experiments were conducted at temperatures of 75, 350, 400, and 450 F. Fires were produced by incandescent carbon wear particles obtained at conditions of electric potential as low as 106 volts and 0.3 ampere at 400 F. Ignitions were obtained only with carbon wear particles produced with an electric potential across the carbon-vane-disk interface. No ignitions were obtained with carbon wear particles produced in the absence of this potential; also, the potential difference produced no ignitions in the absence of carbon wear particles. A film supplement showing ignition by incandescent wear particles is available.

Buckley, Donald H.; Swikert, Max A.; Johnson, Robert L.

1960-01-01

59

Energy deposition rates by charged particles. [in upper atmosphere  

NASA Technical Reports Server (NTRS)

A summary of measurements of the precipitation of electrons and positive ions (in the keV-MeV range) detected aboard eight rockets launched within the Energy Budget Campaign from Northern Scandinavia is given, together with corresponding satellite data. In some cases strong temporal variations of the downgoing integral fluxes were observed. The fluxes provide the background for the calculated ion production rates and altitude profiles of the energy deposition into the atmosphere at different levels of geomagnetic disturbance and cosmic noise absorption. The derived ion production rates by eneretic particles are compared to other night-time ionisation sources.

Torkar, K. M.; Urban, A.; Bjordal, J.; Lundblad, J. A.; Soraas, F.; Smith, L. G.; Dumbs, A.; Grandal, B.; Ulwick, J. C.; Vancour, R. P.

1985-01-01

60

Determination of atmospheric particle size distribution from forward scattering data.  

NASA Technical Reports Server (NTRS)

Description of an analytic method of reconstructing the particle size distribution of atmospheric aerosols when no a priori information is available regarding the refractive index of the particles, the analytic form of the distribution, the size range, and the size extremal values. The method applies in principle to angle-dependent scattering data at a fixed wave number, or to wave-number-dependent scattering data at a fixed angle, or to a combination of the two. Some results of an angular scan study of the aureole are presented to illustrate the effectiveness of the method. In conclusion, an analysis is made of the efficiency and accuracy of the method, the uniqueness of the inverse solutions, and the stability of the method relative to experimental noise.

Fymat, A. L.

1973-01-01

61

Terrestrial atmospheric effects induced by counterstreaming dense interstellar cloud material  

NASA Astrophysics Data System (ADS)

The Solar System during its life has encountered more than 10 times with dense interstellar clouds with particle concentrations about 10(8)-10(9) m(-3) and more suppressing the heliopause to dimensions smaller than 1 AU and bringing the Earth in immediate contact with the interstellar matter. For cloud's concentration greater than of 10(8) m(-3), the flow material at the Earth, completely shielded from solar wind protons would be only subject to solar photoionization processes. Previously published results were limited to consideration of processes outside of the accretion radius and have not been taken into account the photoionization. We have developed a 2D-2-fluid gasdynamical numerical code to describe the behavior of the incoming neutral matter near the Earth, taken into account both the photoionization and the gravity of the Sun. Increased neutral hydrogen fluxes ranging from 10(13) to 10(16) m(-2)s(-1) would cause an alteration of the terrestrial atmosphere. During immersion in the cloud the total incident flux of neutral hydrogen onto the terrestrial atmosphere in the steady state would be balanced by the upward escape flux of hydrogen and the downward flux of water, which is the product of hydrogen-oxygen chemistry via even-odd reaction schemes. In that case hydrogen acts as a catalyst for the destruction of oxygen atoms and causes the ozone concentration to diminish pronouncedly above 50 km from a factor of 1.5 at the stratopause to about a factor of 1000 and more at the mesopause. Thus, depending on the encounter parameters the large mixing ratio of hydrogen decreases the ozon concentration in the mesosphere and triggers an ice age of relatively long duration.

Yeghikyan, A.; Fahr, H.

62

Laboratory Studies of Hydrocarbon Nucleation on Tholin Particles and Thin Organic Films: Application to Titan's Atmosphere  

NASA Technical Reports Server (NTRS)

Titan, Saturn's largest satellite, has a thick nitrogen/methane atmosphere. In Titan's lower atmosphere, methane is saturated or supersaturated with respect to nucleation and may form clouds. To better characterize the properties of Titan's methane clouds we have measured the saturation ratio required to obtain butane nucleation, S (sub crit), on Titan tholin material and organic films. We find a critical saturation ratio for butane on tholin particles of S (sub crit) = 1.40, suggesting high supersaturations are required for nucleation. If methane is similar to butane, we expect high supersaturations of methane as well. This could favor the formation of a small number of large particles, consistent with recent measurements of methane rain on Titan.

Curtis, Daniel B.; Glandorf, David L.; Toon, Owen B.; Tolbert, Margaret A.; McKay, Christopher P.; Khare, Bishun N.

2001-01-01

63

Small particle cirrus observed by the Atmospheric Infrared Sounder  

NASA Astrophysics Data System (ADS)

The high-resolution spectra of the Atmospheric Infrared Sounder (AIRS) have provided an opportunity to globally observe small particle-dominated cirrus clouds. The shape of the radiance spectra in the atmospheric windows is uniquely influenced by small ice crystals with an effective radius (reff) of a few 10s of microns and smaller. In some rare instances, minima in the AIRS brightness temperature (BT) spectra between 800 to 850 cm-1 are seen, consistent with the existence of ice particles with an reff smaller than 3 microns. Much more frequent occurences of small ice particle clouds with reff larger than 3 microns are observed through the large 998 to 811 cm-1 BT differences without minima. The small particle events are occasionally found in orographic cirrus clouds, in and around cumulonimbus towers, and in cirrus bands far removed from convection and orography. Several cases spanning the variety of small particle-dominated cirrus events will be presented. AIRS, located on the EOS-Aqua platform, is a high-resolution grating spectrometer that scans at angles 49.5 degrees on either side of nadir view, at both visible and infrared wavelengths. The surface footprint is 13.5 km at the nadir view, and coverage in the infrared is in three bandpasses (649-1136, 1265-1629, and 2169-2674 cm-1). Comparisons of observed spectra are made with simulated spectra generated by a plane-parallel scattering radiative transfer model using ice particle shapes and sizes calculated by the T-matrix method. These comparisons yield information on small particle cirrus cloud reff and optical depth. Aumann, H.H., and R.J. Pagano, Atmospheric Infrared Sounder on the Earth Observing System. Opt. Eng. 33, 776-784, 1994. Mishchenko, M.I., and L.D. Travis, Capabilities and limitations of a current Fortran implementation of the T-matrix method for randomly oriented, rotationally symmetric scatterers. J. Quant. Spectrosc. Radiat. Transfer, 60, 309-324, 1998. Moncet, J.L., and S.A. Clough, Accelerated monochromatic radiative transfer for scattering atmospheres: Application of a new model to spectral radiance observations. J. Geophys. Res., 102, 21,853-21,866, 1997. Rathke, C., and J. Fischer, Retrieval of cloud microphysical properties from thermal infrared observations by a fast iterative radiance fitting method, J. Atmos. Ocean. Tech., 17, 1509-1524, 2000. Smith, W.L., S. Ackerman, H. Revercomb, H. Huang, D.H. DeSlover, W. Feltz, L. Gumley, and A. Collard, Infrared spectral absorption of nearly invisible cirrus clouds. Geophys. Res. Lett., 25, 1137-1140, 1998. Strabala, K.I., S.A. Ackerman, and W.P. Menzel, Cloud properties inferred from 8-12 micron data. J. Appl. Meteor., 33, 212-229, 1994.

Kahn, B. H.; Eldering, A.; Fishbein, E. F.

2003-04-01

64

Gas-to-particle conversion in the atmosphere: I. Evidence from empirical atmospheric aerosols  

NASA Astrophysics Data System (ADS)

Condensable vapours such as sulphuric acid form aerosol in the atmosphere by the competing mechanisms of condensation on existing aerosol and the nucleation of new aerosol. Observational and theoretical evidence for the relative magnitudes of the competing processes is reviewed, and a number of general conclusions are made. Condensation is sensitive to the sticking probability of sulphuric acid molecules on aerosol particles, but there is now good evidence that it should be close to unity. In this case, equilibration timescales between acid vapour and the aerosol in most of the atmosphere are of the order of minutes or less, so that the acid concentration on such timescales given simply by the production rate times the equilibration time. When the acid concentration exceeds a threshold, nucleation will occur. The atmospheric aerosol therefore follows a history of initial formation in a nucleation burst followed by growth and coagulation with final removal by precipitation. This leads to the inverse correlation between aerosol number concentration and mass concentration found by Clarke (1992. Journal of Atmospheric Chemistry 14, 479-488) in the free troposphere. Binary homogeneous nucleation of sulphuric acid/water droplets, for which various simplified rates are compared, may dominate in such regions, but other mechanisms are possible elsewhere. A detailed analysis is performed of the number concentrations, removal rates, and masses of the components of the different types of global aerosols proposed empirically by Jaenicke (1993. Tropospheric Aerosols, Aerosol-Cloud-Climate Interaction. Academic Press, New York). There is a striking correlation between number concentrations in the nucleation and accumulation modes; and the giant aerosol mode, which if it is present dominates the mass, has little effect on the gas-to-particle conversion process. The mass of the atmospheric aerosol is therefore uncorrelated with the magnitude of molecular aerosol removal by condensation.

Clement, Charles F.; Ford, Ian J.

65

Solar particle effects on minor components of the Polar atmosphere  

NASA Astrophysics Data System (ADS)

Solar activity can influence the Earth's environment, and in particular the ozone layer, by direct modulation of the e.m. radiation or through variability of the incoming cosmic ray flux (solar and galactic particles). In particular, solar energetic particles (SEPs) provide additional external energy to the terrestrial environment; they are able to interact with the minor constituents of the atmospheric layer and produce ionizations, dissociations, dissociative ionizations and excitations. This paper highlights the SEP effects on the chemistry of the upper atmosphere by analysing some SEP events recorded during 2005 in the descending phase of the current solar cycle. It is shown that these events can lead to short- (hours) and medium- (days) term ozone variations through catalytic cycles (e.g. HOx and NOx increases). We focus attention on the relationship between ozone and OH data (retrieved from MLS EOS AURA) for four SEP events: 17 and 20 January, 15 May and 8 September. We confirm that SEP effects are different on the night and day hemispheres at high latitudes.

Damiani, A.; Storini, M.; Laurenza, M.; Rafanelli, C.

2008-02-01

66

Gas-particle partitioning of pesticides in atmospheric samples  

NASA Astrophysics Data System (ADS)

A filter-XAD-2 resin plug high-volume air sampler was used to collect the particle (P) and vapour (V) phases of 11 pesticides. The atmospheric concentrations were measured simultaneously at three sites characterised as remote (Aubure in the Vosges mountains), rural (Colmar, in the upper Rhine Valley), and urban (Strasbourg, in the upper Rhine Valley). The measured concentrations, which agree with those of literature, were used to study the influence of the physico-chemical parameters on the V/P partitioning. The behaviour observed on two organochlorine pesticides ( ?-HCH and HCB), carbaryl, and trifluraline corresponds to the one presented in literature for organochlorine and PAH. Therefore, the V/P partitioning is mainly controlled by temperature, total suspended particle (TSP), and vapour pressure. Nevertheless, the slope of the regression line of log( A.TSP/ F ) against log P° l (where A and F are, respectively, the gas and particulate concentrations and P° l is the subcooled liquid-vapour pressure) is less compared with that presented in literature (0.36 against approximately 0.85). This difference could possibly result from the low TSP concentrations measured in our study. For some pesticides (trifluraline, ?-HCH, mecoprop, carbofuran and atrazine) the description of the V/P partitioning is improved by using relative humidity in addition to the three previous environmental parameters (temperature, TSP and vapour pressure). There seems to exist a competition mechanism between water molecules in gas phase and pesticides to adsorb on the receiving sites of the particles. By this mechanism increase in the atmospheric relative humidity induces a simultaneous increase of pesticides in the gas phase.

Sanusi, Astrid; Millet, Maurice; Mirabel, Philippe; Wortham, Henri

67

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

68

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

69

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

70

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

71

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.

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

2013-01-01

72

Material shields against neutral atomic particle beams. Technical report  

Microsoft Academic Search

A material shield designed to protect a spacecraft against an atomic particle beam will, of necessity, be quite massive; consequently, even modest fractional-weight savings would be significant. With this goal in mind, the particle stopping power and range in various materials were investigated. The lightest shield materials are compounds composed of hydrogen and other light elements.

Kash

1985-01-01

73

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

74

Particle emission from artificial cometary materials  

NASA Technical Reports Server (NTRS)

During KOSI (comet simulation) experiments, mineral-ice mixtures are observed in simulated space conditions. Emission of ice-/dust particles from the sample surface is observed by means of different devices. The particle trajectories are recorded with a video system. In the following analysis we extracted the parameters: particle count rate, spatial distribution of starting points on the sample surface, and elevation angle and particle velocity at distances up to 5 cm from the sample surface. Different kinds of detectors are mounted on a frame in front of the sample to register the emitted particles and to collect their dust residues. By means of these instruments the particle count rates, the particle sizes and the composition of the particles can be correlated. The results are related to the gas flux density and the temperature on the sample surface during the insolation period. The particle emission is interpreted in terms of phenomena on the sample surface, e.g., formation of a dust mantle.

Koelzer, Gabriele; Kochan, Hermann; Thiel, Klaus

1992-01-01

75

Fragmentation energetics of clusters relevant to atmospheric new particle formation.  

PubMed

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 (NPF), but 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 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 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. PMID:23373990

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

2013-02-27

76

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

77

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

78

Particle production in the remote marine atmosphere: Cloud outflow and subsidence during ACE 1  

Microsoft Academic Search

During November and December 1995 the First Aerosol Characterization Experiment (ACE 1) was undertaken as part of the International Global Atmospheric Chemistry (IGAC) Program. A key objective of the aircraft component of this experiment included the identification of source regions for new particles in the remote marine atmosphere. No evidence was found for particle production in the marine boundary layer

A. D. Clarke; J. L. Varner; F. Eisele; R. L. Mauldin; D. Tanner; M. Litchy

1998-01-01

79

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

80

Quantifying the kinetic limitations of atmospheric gas-to-particle conversion  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles, from anthropogenic and biogenic sources, remain a major uncertainty in the Earth system: they impact the climate by directly scattering and absorbing solar radiation, as well as regulating the properties of clouds. On regional scales, aerosols are among the main pollutants deteriorating air quality, their impacts on both poorly quantified. Reducing these uncertainties requires accurate knowledge on the composition, concentrations and size distributions of these particles as they reside in the atmosphere. Unfortunately, there are currently huge uncertainties in many fundamental parameters that are required to predict their environmental impacts. This is largely down to the fact that a significant fraction of atmospheric aerosol particles are comprised of organic material (20-90% of particle mass), containing potentially thousands of compounds with largely uncertain properties It is becoming increasingly evident that aerosols exist as metastable amorphous states, rather than simple liquid/solid mixtures. Empirical evidence suggests that particles can form glass like substances. As the glass transition temperature is approached, an increase in viscosity leads to a reduced rate of molecular diffusion and an arrested non-equilibrium structure. Partitioning between the gas and condensed phase is kinetically limited in such amorphous states. Traditional organic aerosol models do not account for this, they assume that 1) the aerosol phase is a well-mixed non-viscous liquid; 2) the aerosol phase instantaneously equilibrates with the gas phase constituents. This adds significant uncertainty to predictions of gas/particle mass transfer as mixing timescales are ultimately governed by the diffusion coefficients of the aerosol constituents in the aerosol, which, on the other hand, are connected to the viscosity of the particulate matter. For typical aerosol sizes, the characteristic time for mixing could increase from a few milliseconds to hours or even days. In this study, we present direct laboratory determination of viscosity/diffusing of atmospherically relevant species along with an evaluation of composition dependent predictive techniques. Output from highly detailed chemical mechanisms are used to probe potential sensitivities of these kinetic limitations and sensitivities to our predictive capability.

Booth, A.; Murphy, B.; Riipinen, I.; Percival, C.; Topping, D. O.

2013-12-01

81

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

82

The soiling of materials in the ambient atmosphere  

NASA Astrophysics Data System (ADS)

Models describing the rate of soiling of exposed surfaces due to the deposition and accumulation of particulate matter from the atmosphere are reviewed. Samples of white painted wood were exposed for 110 days in the ambient atmosphere. Separate samples were sheltered and unsheltered from rainfall. Reflectance was measured daily. Results are compared with recently published studies in the U.S.A. (samples in the ambient atmosphere) and the U.K. (samples in a road tunnel). Experimental soiling rates were compared with predicted values. Existing models were satisfactory for predicting soiling in a tunnel but underestimated soiling in an ambient situation; a revised formulation is proposed for this situation. Rainfall generally produced a cleaning effect but redistribution of washed-off material could produce enhanced soiling.

Hamilton, R. S.; Mansfield, T. A.

83

The Impact of Energetic Particle Precipitation on the Earths Atmosphere  

NASA Astrophysics Data System (ADS)

Energetic particle precipitation (EPP) represents an important Sun-Earth coupling mechanism with important implications on polar stratospheric ozone chemistry. Solar protons generated during solar storms cause sporadically in situ production of stratospheric NO x and HO x radicals involved in catalytic ozone destruction. Further, NO produced continuously in the mesosphere and lower thermosphere by medium energy electron precipitation (EEP) descends to the stratosphere during the polar winter, where it represents an additional, though variable source of NO x . The capability of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) to measure all important NO y species, as well as ClO and HOCl with global coverage including the polar night regions make it an ideal instrument for studying EPP effects on stratospheric chemistry. We present a quantitative assessment of EPP-induced composition changes as observed by MIPAS during 2002-2004, including the unusually strong solar proton event in October/November 2003. The impact of EPP on the stratospheric ozone budget has been studied with chemical models. The stratospheric ozone loss in the polar regions reached 18DU and lasted over months to years.

Funke, B.; López-Puertas, M.; Garcķa-Comas, M.; Bermejo-Pantaleón, D.; Stiller, G. P.; von Clarmann, T.

84

Etching materials with an atmospheric-pressure plasma jet  

Microsoft Academic Search

A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and 0963-0252\\/7\\/3\\/005\\/img10C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of 0963-0252\\/7\\/3\\/005\\/img11, a stable, arc-free discharge

J. Y. Jeong; S. E. Babayan; V. J. Tu; I. Henins; R. F. Hicks; G. S. Selwyn

1998-01-01

85

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

86

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

87

[Variation of atmospheric particle number concentrations in Qingdao and its impact on visibility].  

PubMed

Atmospheric particle number concentrations were measured from September 2010 to August 2011 with potable light house laser particle counter to study the variation of atmospheric particle concentrations and its impact on visibility in Qingdao. Backward trajectory was calculated by Hysplit model. Statistical analysis was done to discuss the influence of meteorological factors on the atmospheric particle number concentrations and visibility. It was shown that the atmospheric particle number concentrations were the highest in winter and spring, followed by autumn, and the lowest in summer. Air mass from Xinjiang and Gansu regions resulted in higher particle concentrations, while the atmospheric particles from the northeast and the ocean had lower concentrations. The variation of atmospheric particle number concentrations presented a good negative correlation with the variation of wind speed, relative humidity and mixed-layer height. When the air mass came from west or northwest, the surface wind direction was south or southeast and the mixed-layer height was low, the number concentration of fine particles was likely to be higher, which tended to cause low visibility phenomenon. PMID:24720179

Ke, Xin-Shu; Sheng, Li-Fang; Kong, Jun; Hao, Ze-Tong; Qu, Wen-Jun

2014-01-01

88

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

89

Motion and ablation of meteor particles in the upper layers of the atmosphere  

Microsoft Academic Search

A theoretical study of the motion of a meteor particle of arbitrary shape in the rarefied layers of the earth's atmosphere is presented. The mechanism of particle heating due to interaction with the outer gas flow is examined, with allowance for internal thermal conductivity; and changes of particle shape along its trajectory due to ablation are considered. Numerical calculations are

E. Z. Apshtein; N. N. Piliugin

1980-01-01

90

On the stationary charge distribution on aerosol particles in a bipolar ionic atmosphere  

Microsoft Academic Search

Summary By the «limiting sphere» method the combination coefficients for gaseous ions and aerosol particles were calculated, allowing for the jump in ion concentration at the surface of the particles. Hence the stationary charge distribution on aerosol particles in a symmetrical bipolar ionic atmosphere was determined. The use of the Boltzmann equation for this purpose proposed by some authors is

N. A. Fuchs

1963-01-01

91

Effect of particle size in composite materials on radiative properties  

NASA Technical Reports Server (NTRS)

A numerical model for the radiative properties of a composite material composed of ceramic oxide fibers and particles was developed and used to determine the effect of the size parameters of the two components. Results include the computed phase functions for the zirconia and silica composite materials, showing the location and strength of the strong forward-scattering peak. The phase function and the optical properties of the composite are strongly influenced by the particle size parameter through the fiber or particle diameter and the wavelength, the material, and the mixture fraction.

Lee, Siu-Chun; White, Susan; Grzesik, Jan

1993-01-01

92

Preferential settling of elongated mineral dust particles in the atmosphere  

Microsoft Academic Search

Positions of particles' centers of gravity and folding centers were analyzed for individual dust particles in snow on a high mountain in Japan. Bias of dust particles' centers of gravity was observed: L1 (the longest distance from the center of gravity to the boundary of particles) is 5% (of L1, on average) longer than L2 (1\\/2 of the longest axis

Jingmin Li; Kazuo Osada

2007-01-01

93

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

94

Nanostructured materials production by hypersonic plasma particle deposition  

Microsoft Academic Search

We report on a new process for producing nanostructured materials, hypersonic plasma particle deposition (HPPD), wherein a thermal plasma seeded with vapor-phase precursors is supersonically expanded through a nozzle to nucleate ultrafine particles, which are then deposited by hypersonic impaction onto a temperature-controlled substrate. Results from preliminary experiments aimed at synthesizing nanostructured silicon are presented.

N. P. Rao; H. J. Lee; M. Kelkar; D. J. Hansen; J. V. R. Heberlein; P. H. McMurry; S. L. Girshick

1997-01-01

95

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

96

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

97

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

98

Atmospheric ice nucleation by fertile soil dusts particles: Relative importance of mineral and biological components  

NASA Astrophysics Data System (ADS)

Dusts emitted from agricultural soils may represent a significant source of atmospheric particulates at mid-latitudes. Such dusts, which can be aerosolised by anthropogenic agricultural activities, have previously been estimated to be present in the atmosphere at sufficient number densities that they could potentially compete with other known ice nuclei (IN). In contrast to soils from arid regions, such as the Sahara, fertile soils contain a larger fraction of biological material, which can lead to an enhancement in the ice nucleating ability of their associated dusts. However, considerable uncertainties remain regarding the relative efficacy of soil dust particles from fertile soils as IN. Using an experimental methodology designed to increase sensitivity to a wide range of ice nucleation efficiencies, we have characterized the immersion mode ice nucleating activities of sub 11 ?m particles extracted from surface soils collected in four locations around England. By using a variety of droplet sizes, from pico-to micro-litre, we have been able to characterize the ice active site densities in soils (estimated using a time-independent framework) at temperatures ranging from -5°C down to the homogeneous limit of freezing at ~ -36°C. At temperatures below -15°C, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the inorganic fraction of soil dusts becomes increasingly important in the initiation of the ice phase at large supercoolings. Conversely, above -15°C we find that the ice nucleating activity of the soils dusts was larger than expected from the mineral composition of the soils. The sites responsible for this high temperature ice nucleating activity were sensitive to heat treatment and digestion with hydrogen peroxide, suggesting that they are biological in origin. We conclude that although only being a relatively minor contributor to the global atmospheric dust burden, the enhanced IN activities of dusts generated from agricultural activities may impact upon cloud glaciation, particularly at temperatures above -15°C.

O'Sullivan, Daniel; Murray, B. J.; Malkin, T. L.; Webb, M. E.; Whale, T. F.; Atkinson, J. D.; Baustian, K. J.

2013-05-01

99

RADIOACTIVE PARTICLES IN THE ATMOSPHERE, JANUARY 1951MARCH 1951  

Microsoft Academic Search

ABS>Filter papers received from various western locations after the 1951 ; tests in Nevada indicated the presence of active particles at all locations ; monitored. The results of monitoring at each station are included in tabular ; form showing the active particle collection from day to day. Maximum particle ; count (3.62\\/mĀ³) was recorded at Salt Lake City Feb. 4-5,

Singlevich

1951-01-01

100

Model simulations of the impact of energetic particle precipitation onto the upper and middle atmosphere  

Microsoft Academic Search

Solar eruptions and geomagnetic storms can produce fluxes of high-energy protons and elec-trons, so-called Solar Energetic Particle Events, which can enter the Earth's atmosphere espe-cially in polar regions. These particle fluxes primarily cause ionisation and excitation in the upper atmosphere, and thereby the production of HOx and NOx species, which are catalysts for the reduction of ozone. To simulate such

Nadine Wieters; Miriam Sinnhuber; Holger Winkler; Uwe Berger; Jan Maik Wissing; Gabriele Stiller; Bernd Funke; Justus Notholt

2010-01-01

101

Observational quantification of the separation of simple and complex atmospheric ice particles  

NASA Astrophysics Data System (ADS)

impact of ice clouds on weather and climate is a function of ice particle shape through light scattering properties and cloud lifetime through ice particle sedimentation rates. Many weather forecast and climate models use two categories to represent ice cloud particles: cloud ice and snow, though the distinction between particle categories is generally without observational justification. Improved characterization of cloud ice and snow as well as the transition between them will make models more realistic. An analysis of particle imagery data from high-resolution aircraft particle imaging probes indicates that atmospheric ice particles can easily be separated by particle complexity. In this work, a technique is described which enables the clear separation of vapor grown particles from aggregates of particles. When applied to two example data sets, the technique shows that the separation between these categories occurs at 150 and 250 microns, for two example data sets.

Schmitt, Carl G.; Heymsfield, Andrew J.

2014-02-01

102

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

NASA Astrophysics Data System (ADS)

In cold high altitude cirrus clouds and anvils of high convective clouds in the tropics and mid-latitudes, ice partciles that are exposed 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. In this talk we will describe experiements that simulate the atmospheric freeze-drying cycle of aerosols. We find that aerosols with high organic content can form highly porous particles (HPA) with a larger diameter and a lower density than the initial homogenous aerosol following ice subliation. 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 follwoing ice sublimation. We find that the highly porous aerosol scatter solar light less efficiently than non-porous aerosol particles. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges.

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

2014-05-01

103

Chemical speciation of individual atmospheric particles using low- Z electron probe X-ray microanalysis  

Microsoft Academic Search

Chemical speciation of individual microparticles is of much interest in environmental atmospheric chemistry; e.g. the determination of the elemental concentrations in individual atmospheric aerosol particles is important to study the chemical behavior of atmospheric pollution. Recently, an EPMA technique using an X-ray detector equipped with an ultra-thin window, allowing EPMA to determine concentrations of low-Z elements, such as C, N,

Chul-Un Ro; Keun-Young Oh; HyeKyeong Kim; Youngsin Chun; Jįnos Osįn; Johan de Hoog; Ren e e Van Grieken

2001-01-01

104

Superparamagnetic Fe3O4 particles formed by oxidation of pyrite heated in an anoxic atmosphere  

USGS Publications Warehouse

As a follow-up to previous gas analysis experiments in which pyrite was heated to 681 K in an anoxic (oxygen starved) atmosphere, the first oxidation product, FeSO4, was studied as a bulk material. No decomposition of FeSO4 to Fe3O4 was observed in the temperature range studied. The lack of decomposition of bulk FeSO4 to Fe3O4 suggests that FeS2 oxidizes directly to Fe3O4, or that FeSO4, FeS2 and O2 react together to form Fe3O4. Magnetic susceptibility and magnetization measurements, along with magnetic hysteresis curves, show that small particles of Fe3O4 form on the pyrite surface, rather than a continuous layer of bulk Fe3O4. A working model describing the oxidation steps is presented. ?? 1990.

Thorpe, A. N.; Senftle, F. E.; Talley, R.; Hetherington, S.; Dulong, F.

1990-01-01

105

Hydrodynamic modelling of cometary particles captured in aerogel and the Earth's atmosphere  

NASA Astrophysics Data System (ADS)

The capture of cometary fragments in aerogel by the Stardust mission is analogous to the process of meteoroid deceleration in the Earth’s atmosphere. We present a simplified model for the formation of the tracks formed in aerogel by hypervelocity impacts of cometary material. Using a hydrodynamic approach to model this class of problem overcomes some of the errors associated with previous semi-analytical models for track formation (Coulson 2009). The hydrodynamic models developed allow the particle velocity, temperature and pressure to be calculated as a function of track length within aerogel. A qualative description of how this model can be extended to the formation of bulbous cavities using the Chapman-Jouquet theory is provided.

Coulson, S. G.

2009-11-01

106

Behavior of alumina particles in atmospheric pressure plasma jets  

SciTech Connect

The distribution of Al{sub 2}O{sub 3} particle size, velocity and temperature was mapped over the flow field of a 31.5 kW plasma torch. The effects of varying the powder loading were studied. The powder feed rate was varied between .45 and 2.05 kg/hr independent of the carrier gas flow rate. The particle flow field was non-symmetric due to the method of particle injection. The data indicate that powder feed rate does not significantly affect either the temperature or velocity of the particles, for typical plasma spray conditions, and that the assumption of a dilute particle flow field is valid. 1 ref., 7 figs.

Fincke, J.R.; Swank, W.D.

1990-01-01

107

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

108

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

109

UNDERSTANDING AND REDUCING THE UNCERTAINTY ASSOCIATED WITH THE EFFECT OF ATMOSPHERIC PARTICLES ON CLOUDS AND CLIMATE  

EPA Science Inventory

I predict that human-generated particles have modified clouds and cooled climate, somewhat masking the effect of greenhouse gases and that these particles have also modified the amount of sunlight reaching the ground, changing the thermodynamic cycles in the atmosphere. Wi...

110

Carbohydrate-Like Composition of Submicron Atmospheric Particles and their Production from Ocean Bubble Bursting  

Microsoft Academic Search

Oceans cover over two-thirds of the Earth's surface, and the particles emitted to the atmosphere by waves breaking on sea surfaces provide an important contribution to the planetary albedo. During the ICEALOT cruise on the R\\/V Knorr in March and April of 2008, organic mass accounted for 15% to 47% of the submicron particle mass in the air masses sampled

L. M. Russell; L. N. Hawkins; A. A. Frossard; P. Quinn; T. S. Bates

2009-01-01

111

Trajectory Models for Heavy Particles in Atmospheric Turbulence: Comparison with Observations  

Microsoft Academic Search

The simplest ''random flight'' models for the paths of heavy particles in turbulence have been tested against previous observations of the deposition of glass beads from an elevated source in the atmospheric surface layer. For the bead sizes examined (diameter 50-100 mm), for which the ratio of particle inertial timescale to turbulence timescale t p\\/GL K 1, it was found

John D. Wilson

2000-01-01

112

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...

113

Ion Densities and Particle Charges for Alpha Ionization in an Aerosol Atmosphere: Columnar Recombination Corrections  

Microsoft Academic Search

Ionization by alpha sources in an environment containing small aerosol particles is of interest in aerosol neutralizes, particle chargers and atmospheric electricity. It is known that the conventional ion-balance equation is inadequate in describing the bulk ion densities for alpha sources in view of the columnar recombination process. An earlier self-consistent formulation to include this effect is extended to the

Y. S. Mayya; W. Holländer

1995-01-01

114

Real-time measurement of correlated size and composition profiles of individual atmospheric aerosol particles  

Microsoft Academic Search

In this paper, the unique real-time measurement capabilities of aerosol time-of-flight mass spectrometry (ATOFMS) for characterizing atmospheric aerosol particles are demonstrated. ATOFMS is used to obtain the aerodynamic size and chemical composition of individual aerosol particles sampled directly into the instrument from outdoors. Such measurements are made in-situ by combining a unique dual-laser aerodynamic particle sizing system to size and

Christopher A. Noble; Kimberly A. Prather

1996-01-01

115

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

116

Fabrication of advanced particles and particle-based materials assisted by droplet-based microfluidics.  

PubMed

Recent advances in the fabrication of complex particles and particle-based materials assisted by droplet-based microfluidics are reviewed. Monodisperse particles with expected internal structures, morphologies, and sizes in the range of nanometers to hundreds of micrometers have received a good deal of attention in recent years. Due to the capability of generating monodisperse emulsions and of executing precise control and operations on the suspended droplets inside the microchannels, droplet-based microfluidic devices have become powerful tools for fabricating complex particles with desired properties. Emulsions and multiple-emulsions generated in the microfluidic devices can be composed of a variety of materials including aqueous solutions, gels, polymers and solutions containing functional nanoparticles. They are ideal microreactors or fine templates for synthesizing advanced particles, such as polymer particles, microcapsules, nanocrystals, and photonic crystal clusters or beads by further chemical or physical operations. These particles are promising materials that may be applicable for many fields, such as photonic materials, drug delivery systems, and bio-analysis. From simple to complex, from spherical to nonspherical, from polymerization and reaction crystallization to self-assembly, this review aims to help readers be aware of the many aspects of this field. PMID:21618428

Wang, Jing-Tao; Wang, Juan; Han, Jun-Jie

2011-07-01

117

Receptor modeling for inhalable atmospheric particles in Sao Paulo, Brazil  

NASA Astrophysics Data System (ADS)

Aerosol samples were collected with stacked filter units (SFUs) at the Sao Paulo University Campus during the winter of 1989. The fine and coarse filters of the SFU samples were analyzed by particle-induced X-ray emission (PIXE) and the data were subjected to an absolute principal component analysis (APCA) in order to identify the major aerosol sources and to apportion the particulate mass to these sources. Five sources were identified for the fine particles: industrial emissions, which accounted for 13% of the fine mass; emissions from residual oil and diesel, explaining 41%; resuspended soil dust, with 28%; and emissions of Cu and of Mg, with together 18% (these elements could not be attributed to any specific source). For the coarse particles, four sources were identified: soil dust, accounting for 59% of the coarse mass; industrial emissions, with 19%; oil burning, with 8%; and sea-salt aerosol, with 14% of the coarse mass.

Andrade, F.; Orsini, C.; Maenhaut, W.

1993-04-01

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

Behavior of alumina particles in atmospheric pressure plasma jets.  

National Technical Information Service (NTIS)

The distribution of Al(sub 2)O(sub 3) particle size, velocity and temperature was mapped over the flow field of a 31.5 kW plasma torch. The effects of varying the powder loading were studied. The powder feed rate was varied between .45 and 2.05 kg/hr inde...

J. R. Fincke W. D. Swank

1990-01-01

120

DETERMINATION OF THE STRONG ACIDITY OF ATMOSPHERIC FINE PARTICLES (  

EPA Science Inventory

This report is a standardized methodology description for the determination of strong acidity of fine particles (less than 2.5 microns) in ambient air using annular denuder technology. his methodology description includes two parts: art A - Standard Method and Part B - Enhanced M...

121

Genesis Concentrator Target Particle Contamination Mapping and Material Identification  

NASA Technical Reports Server (NTRS)

The majority of surface particles were found to be < 5 microns in diameter with increasing numbers close to the optical resolution limit of 0.3 microns. Acceleration grid EDS results show that the majority of materials appear to be from the SRC shell and SLA materials which include carbon-carbon fibers and Si-rich microspheres in a possible silicone binder. Other major debris material from the SRC included white paint, kapton, collector array fragments, and Al. Image analysis also revealed that SRC materials were also found mixed with the Utah mud and salt deposits. The EDS analysis of the acceleration grid showed that particles < 1 m where generally carbon based particles. Chemical cleaning techniques with Xylene and HF in an ultrasonic bath are currently being investigated for removal of small particles by the Genesis science team as well as ultra-pure water megasonic cleaning by the JSC team [4]. Removal of organic contamination from target materials is also being investigated by the science team with the use of UV-ozone cleaning devices at JSC and Open University [5]. In preparation for solar wind oxygen analyses at UCLA and Open University [1, 2], surface particle contamination on three Genesis concentrator targets was closely examined to evaluate cleaning strategies. Two silicon carbide (Genesis sample # 60001 and 60003) and one chemical vapor deposited (CVD) 13C concentrator target (60002) were imaged and mosaic mapped with optical microscopes. The resulting full target mosaic images and particle feature maps were subsequently compared with non-flight, but flight-like, concentrator targets and sample return capsule (SRC) materials. Contamination found on the flown concentrator acceleration grid was further examined using a scanning electron microscope (SEM). Energy dispersive X-ray spectroscopy (EDS) for particle identification was subsequently compared with the optical images from the flown targets. Figure 1 show that all three targets imaged in this report are fully intact and do not show any signs of material fractures. However, previous ellipsometry results and overview imaging of both flown SiC targets show a solar wind irradiation gradient from the center focal point to the outer edge [3]. In addition, due to the hard landing, each target has experienced varying degrees of impacts, scratches, and particle debris from the spacecraft and Utah impact site.

Calaway, Michael J.; Rodriquez, M. C.; Allton, J. H.

2007-01-01

122

Etching materials with an atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and 0963-0252/7/3/005/img10C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of 0963-0252/7/3/005/img11, a stable, arc-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: 0963-0252/7/3/005/img12 for Kapton (0963-0252/7/3/005/img13 and He only), 0963-0252/7/3/005/img14 for silicon dioxide, 0963-0252/7/3/005/img15 for tantalum and 0963-0252/7/3/005/img16 for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.

Jeong, J. Y.; Babayan, S. E.; Tu, V. J.; Park, J.; Henins, I.; Hicks, R. F.; Selwyn, G. S.

1998-08-01

123

Secondary organic aerosol formation from toluene in an atmospheric hydrocarbon mixture: Water and particle seed effects  

NASA Astrophysics Data System (ADS)

Atmospherically relevant secondary organic aerosol (SOA) concentrations from toluene, in an urban hydrocarbon environment, with oxides of nitrogen in natural sunlight, were studied in a large outdoor chamber with different initial humidity and types of initial seed aerosols. Ammonium sulfate particles (38 ?g m -3) in the presence of an atmospheric hydrocarbon mixture and NOx in sunlight under a dry atmosphere (%RH = 6 to 10%) show reduced SOA formation when compared to similar gas phase conditions with lower ammonium sulfate (7 ?g m -3) and higher relative humidities (%RH 40 to 90%). No post particle nucleation (particles in the 6 to 10 nm range) was observed in either seeded system. When initial background particles levels were below 0.5 ?g m -3 particle nucleation was observed. A new condensed aromatic kinetic chemical mechanism was developed to simulate experimental data. A particle water phase was highly related to SOA formation. Reasonable fits to the gas and total SOA concentrations emphasize the important impact of different initial particle seed levels and particle phase water when simulating SOA formation from aromatic compounds like toluene.

Kamens, Richard M.; Zhang, Haofei; Chen, Eric H.; Zhou, Yang; Parikh, Harshal M.; Wilson, Rebecca L.; Galloway, Katherine E.; Rosen, Elias P.

2011-04-01

124

Penetrant and magnetic-particle inspection for material integrity  

Microsoft Academic Search

The Nondestructive Evaluation Section at Lawrence Livermore provides penetrant and magnetic-particle inspection services. These two techniques are used on materials and fabricated parts to test for surface or near-surface cracks and defects that may limit serviceability. The use of these methods assures a trouble-free service life, improves safety, and is cost-effective. The inspection of material at appropriate stages of fabrication

R. H. Bossi; J. R. Ambrosino

1983-01-01

125

Detection of special nuclear materials with the associate particle technique  

NASA Astrophysics Data System (ADS)

In the frame of the French trans-governmental R&D program against chemical, biological, radiological, nuclear and explosives (CBRN-E) threats, CEA is studying the detection of Special Nuclear Materials (SNM) by neutron interrogation with fast neutrons produced by an associated particle sealed tube neutron generator. The deuterium-tritium fusion reaction produces an alpha particle and a 14 MeV neutron almost back to back, allowing tagging neutron emission both in time and direction with an alpha particle position-sensitive sensor embedded in the generator. Fission prompt neutrons and gamma rays induced by tagged neutrons which are tagged by an alpha particle are detected in coincidence with plastic scintillators. This paper presents numerical simulations performed with the MCNP-PoliMi Monte Carlo computer code and with post processing software developed with the ROOT data analysis package. False coincidences due to neutron and photon scattering between adjacent detectors (cross talk) are filtered out to increase the selectivity between nuclear and benign materials. Accidental coincidences, which are not correlated to an alpha particle, are also taken into account in the numerical model, as well as counting statistics, and the time-energy resolution of the data acquisition system. Such realistic calculations show that relevant quantities of SNM (few kg) can be distinguished from cargo and shielding materials in 10 min acquisitions. First laboratory tests of the system under development in CEA laboratories are also presented.

Carasco, Cédric; Deyglun, Clément; Pérot, Bertrand; Eléon, Cyrille; Normand, Stéphane; Sannié, Guillaume; Boudergui, Karim; Corre, Gwenolé; Konzdrasovs, Vladimir; Pras, Philippe

2013-04-01

126

Detection of special nuclear materials with the associate particle technique  

SciTech Connect

In the frame of the French trans-governmental R and D program against chemical, biological, radiological, nuclear and explosives (CBRN-E) threats, CEA is studying the detection of Special Nuclear Materials (SNM) by neutron interrogation with fast neutrons produced by an associated particle sealed tube neutron generator. The deuterium-tritium fusion reaction produces an alpha particle and a 14 MeV neutron almost back to back, allowing tagging neutron emission both in time and direction with an alpha particle position-sensitive sensor embedded in the generator. Fission prompt neutrons and gamma rays induced by tagged neutrons which are tagged by an alpha particle are detected in coincidence with plastic scintillators. This paper presents numerical simulations performed with the MCNP-PoliMi Monte Carlo computer code and with post processing software developed with the ROOT data analysis package. False coincidences due to neutron and photon scattering between adjacent detectors (cross talk) are filtered out to increase the selectivity between nuclear and benign materials. Accidental coincidences, which are not correlated to an alpha particle, are also taken into account in the numerical model, as well as counting statistics, and the time-energy resolution of the data acquisition system. Such realistic calculations show that relevant quantities of SNM (few kg) can be distinguished from cargo and shielding materials in 10 min acquisitions. First laboratory tests of the system under development in CEA laboratories are also presented.

Carasco, Cedric; Deyglun, Clement; Perot, Bertrand; Eleon, Cyrille [CEA, DEN, Cadarache, Nuclear Measurement Laboratory, F-13108 St Paul-lez-Durance (France); Normand, Stephane; Sannie, Guillaume; Boudergui, Karim; Corre, Gwenole; Konzdrasovs, Vladimir [CEA, DRT, LIST, Saclay, F-91191 Gif-sur-Yvette (France); Pras, Philippe [CEA, DAM, DIF, F-91297 Arpajon (France)

2013-04-19

127

Comparison of analytical methods for HULIS measurements in atmospheric particles  

NASA Astrophysics Data System (ADS)

Humic-Like Substances (HULIS) are a major contributor to the organic carbon in atmospheric aerosol. It would be necessary to standardise an analytical method that could be easily and routinely used for HULIS measurements. We present one of the first comparisons of two of the main methods in use to extract HULIS, using i) a weak anion exchanger (DEAE) and ii) the combination of two separation steps, one according to polarity (on C18) and the second according to acidity (with a strong anion exchanger SAX). The quantification is performed with a DOC analyzer, complemented by an investigation of the chemical structure of the extracted fractions by UV-Visible spectroscopy. The analytical performances of each method are determined and compared for humic substances standards. These methods are further applied to determine the water extractable HULIS (HULISWS) and the 0.1M NaOH alkaline extractable HULIS (HULIST) in atmospheric aerosol collected in an Alpine Valley during winter time. This comparison shows that the simpler DEAE isolation procedure leads to higher recoveries and better reproducibility and should therefore be recommended.

Baduel, C.; Voisin, D.; Jaffrezo, J. L.

2009-03-01

128

Method and apparatus for making articles from particle based materials  

DOEpatents

A method and apparatus 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.

Moorhead, Arthur J. (Knoxville, TN); Menchhofer, Paul A. (Oak Ridge, TN)

1995-01-01

129

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

130

Preparation and characterization of energetic materials coated superfine aluminum particles  

NASA Astrophysics Data System (ADS)

This work is devoted to protect the activity of aluminum in solid rocket propellants by means of solvent/non-solvent method in which nitrocellulose (NC) and Double-11 (shortened form of double-base gun propellant, model 11) have been used as coating materials. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the morphology of coated Al particles. Other characterization data of coated and uncoated Al particles, such as infrared absorption spectrum, laser particle size analysis and the active aluminum content were also studied. The thermal behavior of pure and coated aluminum samples have also been studied by simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC). The results indicated that: superfine aluminum particles could be effectively coated with nitrocellulose and Double-11 through a solvent/non-solvent method. The energetic composite particles have core-shell structures and the thickness of the coating film is about 20-50 nm. The active aluminum content of different coated samples was measured by means of oxidation-reduction titration method. The results showed that after being stored in room temperature and under 50% humidity condition for about 4months the active aluminum content of coated Al particles decreased from 99.8 to 95.8% (NC coating) and 99.2% (Double-11 coating) respectively. Double-11 coating layer had a much better protective effect. The TG-DTA and DSC results showed that the energy amount and energy release rate of NC coated and Double-11 coated Al particles were larger than those of the raw Al particles. Double-11 coated Al particles have more significant catalytic effect on the thermal decomposition characters of AP than that of NC coated Al particles. These features accorded with the energy release characteristics of solid propellant.

Liu, Songsong; Ye, Mingquan; Han, Aijun; Chen, Xin

2014-01-01

131

Characterization of atmospheric particles in Seoul, Korea using SEM-EDX.  

PubMed

Atmospheric particles in Seoul, Korea were investigated by scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). Particles were identified and characterized by their morphology and elemental compositions. The morphology of particles was closely coupled with elemental compositions, which provided information on sources and transport processes of aerosols. There were various types of combustion-derived particles identified such as fly ashes, soot, organic matters, tar balls, chars, and sulfur-containing particles. These anthropogenic particles mainly have spherical shape with nano- to micro-meter size. Char was, however, distinguished by irregular shape with varying size up to several micrometers. The sulfur-containing aggregates show a wide range of size, shape, and elemental composition. In addition, bioaerosol and mineral dust were the most abundant particles from natural sources. PMID:22966700

Kang, Eunha; Park, Inji; Lee, Young Jae; Lee, Meehye

2012-07-01

132

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

133

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

134

Non-silica aerogels as hypervelocity particle capture materials  

NASA Astrophysics Data System (ADS)

The Stardust sample return mission to the comet Wild 2 used silica aerogel as the principal cometary and interstellar particle capture and return medium. However, since both cometary dust and interstellar grains are composed largely of silica, using a silica collector complicates the science that can be accomplished with these particles. The use of non-silica aerogel in future extra-terrestrial particle capture and return missions would expand the scientific value of these missions. Alumina, titania, germania, zirconia, tin oxide, and resorcinol/formaldehyde aerogels were produced and impact tested with 20, 50, and 100?m glass microspheres to determine the suitability of different non-silica aerogels as hypervelocity particle capture mediums. It was found that non-silica aerogels do perform as efficient hypervelocity capture mediums, with alumina, zirconia, and resorcinol/formaldehyde aerogels proving to be the best of the materials tested.

Jones, Steven M.

2010-01-01

135

Development of the Global Atmospheric Transport and Backtracking System Using Lagrangian Particle Dispersion Model  

NASA Astrophysics Data System (ADS)

We developed global atmospheric transport and backtracking system using FLEXPART Lagrangian particle dispersion model for the purpose of predicting radioactive materials movement in case of neighboring country's nuclear accident. In addition, the system can be used to estimate the source location when unusual peak was detected in radiation monitoring stations in Korea. As an input to this system, we can choose two meteorological data, namely the Korea Meteorological Administration(KMA)'s global meteorological data and the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) data. KMA produces global meteorological data using Unified Model system which was introduced from the UK Met Office. Meteorological data's spatial resolution is about 25 km and its temporal resolution is 3 hour. GFS data had 26 model levels and a resolution of 0.5×0.5° globally. Using this system, we can evaluate the characteristics of transport and dispersion of radioactive materials released from the source region. Also, we can estimate the possible source regions using observed data and Source-Receptor Sensitivity Matrix (SRSM). SRSM can be calculated using FLEXPART model in backward mode. We adopted Graphic User Interface (GUI) system, so users can run and check the model results easily.

Lee, Kwan-Hee; Lee, Jin-Hong; Park, Soon-Ung; Cho, Jeong-Hoon; Yun, Ju-Yong; Park, Hong-Mo; Lee, Byoung-Soo

2014-05-01

136

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

137

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

NASA Astrophysics Data System (ADS)

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 dust, tire wear, brake lining dust, meat cooking operations, industrial oil-fired boilers, roofing tar pots, natural gas combustion in residential homes, cigarette smoke, fireplaces burning oak and pine wood, and plant leaf abrasion products. These primary fine particle source emissions were supplied to a computer-based model that simulates atmospheric transport, dispersion, and dry deposition based on the time series of hourly wind observations and mixing depths. Monthly average fine particle organic compound concentrations that would prevail if the primary organic aerosol were transported without chemical reaction were computed for more than 100 organic compounds within an 80 km × 80 km modeling area centered over Los Angeles. The monthly average compound concentrations predicted by the transport model were compared to atmospheric measurements made at monitoring sites within the study area during 1982. The predicted seasonal variation and absolute values of the concentrations of the more stable compounds are found to be in reasonable agreement with the ambient observations. While model predictions for the higher molecular weight polycyclic aromatic hydrocarbons (PAH) are in agreement with ambient observations, lower molecular weight PAH show much higher predicted than measured atmospheric concentrations in the particle phase, indicating atmospheric decay by chemical reactions or evaporation from the particle phase. The atmospheric concentrations of dicarboxylic acids and aromatic polycarboxylic acids greatly exceed the contributions that are due to direct emissions from primary sources, confirming that these compounds are principally formed by atmospheric chemical reactions.

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

1996-08-01

138

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

139

Source apportionment of fine and coarse atmospheric particles in Auckland, New Zealand.  

PubMed

Atmospheric fine particles (with a diameter less than 2.5 microm) and coarse particles (with a diameter between 2.5 and 10 microm) were collected simultaneously at an urban background site in Auckland, New Zealand, in the summer and winter of 2003. Major water-soluble ions, black carbon (BC), and some elements in the samples were analysed, and the data compiled into two sets. Selected trace gases (NH3, HONO, HNO3, and SO2) were also collected at the same time. Application of positive matrix factorisation to the particle data resolved five sources for the fine particles and five for the coarse particles. Weighted multiple linear regression was used to investigate the mass contributions of the sources. It was found that although natural sources had significant contributions to the coarse particles, anthropogenic sources dominated the contributions to the fine particles, particularly in winter. Significant seasonal changes of the sources were observed. Overall, sea salt and wind-blown soil had significantly stronger contributions in the summer; in contrast, the winter contribution of vehicle emissions, road dust, and industry and incineration sources was significantly higher. These seasonal changes may be explained by variations in meteorological conditions and atmospheric chemistry. The nonparametric correlations between the atmospheric concentrations of the trace gases and the mass contributions of the resolved sources demonstrate that these sources are realistic, providing a useful supplementary approach for the assessment of receptor modelling. PMID:15752501

Wang, Haobo; Shooter, David

2005-03-20

140

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

141

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

142

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

143

Field-responsive smart composite particle suspension: materials and rheology  

NASA Astrophysics Data System (ADS)

Both electrorheological (ER) and magnetorheological (MR) fluids are known to be smart materials which can be rapidly and reversibly transformed from a fluid-like to a solid-like state within milliseconds by showing dramatic and tunable changes in their rheological properties under external electrical or magnetic field strength, respectively. Here, among various smart composite particles studied, recently developed core-shell structured polystyrene/graphene oxide composite based ER material as well as the dual-step functionally coated carbonyl iron composite based MR material are briefly reviewed along with their rheological characteristics under external fields.

Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin

2012-09-01

144

An Overview of Particle Beam Materials Processing Techniques*  

NASA Astrophysics Data System (ADS)

Materials processing techniques can lead to the development of new products, create new applications by modifying existing materials, and add significant value to existing product lines. Additionally, there is ever-increasing consumer and regulatory pressure to develop "greener" products utilizing "dry chemistry" which have reduced environmental impact, and where the production process yields only product and no waste. Such processing can result from the use of photons or elementary particles. Accelerated particle beams offer many diverse opportunities, to process materials if economic targets can be met. This mini-symposium, a joint endeavor of the APS Division of the Physics of Beams (DPB) and the Forum on Industrial and Applied Physics (FIAP), seeks to review these opportunities and the current state-of-the-art, by assembling leading practitioners of particle beam materials processing for review presentations. Beam processing areas covered in the symposium will include: electron beam processing of biomass, curing of composite materials, sterilization and other applications; ion beams and plasma accelerators for surface processing; proposed next-generation lithography tools that utilize either compact synchrotrons or small ion and electron accelerators; high-volume UV surface processing of polymers and metals using free-electron lasers or excimer lamps, and beam generation of tritium. * This work supported by U.S. DOE Contract No. DE-AC05-84ER40150.

Dylla, H. F.

1996-05-01

145

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

146

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

147

On the Climatic Impact of CO2 Ice Particles in Atmospheres of Terrestrial Exoplanets  

NASA Astrophysics Data System (ADS)

Clouds play a significant role for the energy budget in planetary atmospheres. They can scatter incident stellar radiation back to space, effectively cooling the surface of terrestrial planets. On the other hand, they may contribute to the atmospheric greenhouse effect by trapping outgoing thermal radiation. For exoplanets near the outer boundary of the habitable zone, condensation of CO2 can occur due to the low atmospheric temperatures. These CO2 ice clouds may play an important role for the surface temperature and, therefore, for the question of habitability of those planets. However, the optical properties of CO2 ice crystals differ significantly from those of water droplets or water ice particles. Except for a small number of strong absorption bands, they are almost transparent with respect to absorption. Instead, they are highly effective scatterers at long and short wavelengths. Therefore, the climatic effect of a CO2 ice cloud will depend on how much incident stellar radiation is scattered to space in comparison to the amount of thermal radiation scattered back towards the planetary surface. This contribution aims at the potential greenhouse effect of CO2 ice particles. Their scattering and absorption properties are calculated for assumed particle size distributions with different effective radii and particle densities. An accurate radiative transfer model is used to determine the atmospheric radiation field affected by such CO2 particles. These results are compared to less detailed radiative transfer schemes employed in previous studies.

Kitzmann, D.; Patzer, A. B. C.; Rauer, H.

2014-04-01

148

Are coarse particles unexpected common reservoirs for some atmospheric anthropogenic trace elements? A case study  

NASA Astrophysics Data System (ADS)

Without specific experimental equipment, it is very difficult to sample long-term atmospheric deposits on a pure state. That is why the composition of air-transferred solid material accumulated for 40 years in the 2 m-high walls, pierced with numerous holes of an outdoor public shelter, Grenoble city, France, was studied. An appropriate fractionation procedure allowed to obtain several fractions which were i) a sand fraction (8.3%) (fraction A), ii) a large mass of organic matter corresponding mostly to large fragments (>250 ?m) of plant origin (66.7%) (fraction B) or to pollen fraction C (0.4%), iii) a slowly depositing organo-clay fraction (20%) (fractions D1 and D2) and iv) a solution mixed with non-settable particles (4.3%) (fraction E). The composition of each fraction was determined for 20 elements. The sand fraction showed very high concentrations specifically in Cu, Pb and Fe corresponding respectively to 81.5, 48.2 and 35.2% of the samples content in these elements. In contrast, Cd and Zn were mainly accumulated in the fraction B (67.5 and 62.2%, respectively). The scanning electron microscopy coupled to energy dispersive X-ray analysis (SEM-EDX) study of the fraction A showed the presence of large particles bearing Pb and Fe, particles rich in Cu and typical fly ashes originating mostly from iron industry. Most of these particles had a crystalline shape suggesting that they were formed after emission at a high temperature. The Pb-Fe-Cu deposit seen in fraction A likely originates from the neighbouring road surface contaminated by car traffic for several decades. The 206Pb/207Pb ratio (1.146 ± 0.004) showed that in the coarse sandy fraction A, Pb was represented at 65% by non-gasoline lead and 35% by "gasoline" lead emitted before 1999. The fraction A particles can only be transported on a limited distance by high magnitude events. They constitute a large reservoir for Cu and Pb and may play a major role in the long-term contamination of urban soils.

Catinon, Mickaėl; Ayrault, Sophie; Boudouma, Omar; Bordier, Louise; Agnello, Gregory; Reynaud, Stéphane; Tissut, Michel

2013-08-01

149

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.

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

150

Treatment of airborne asbestos and asbestos-like microfiber particles using atmospheric microwave air plasma  

Microsoft Academic Search

Atmospheric microwave air plasma was used to treat asbestos-like microfiber particles that had two types of ceramic fiber and one type of stainless fiber. The treated particles were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experiment results showed that one type of ceramic fiber (Alumina:Silica=1:1) and the stainless fiber were spheroidized, but the other type of

A. Averroes; H. Sekiguchi; K. Sakamoto

2011-01-01

151

Solar Particle Events in the QinetiQ Atmospheric Radiation Model  

Microsoft Academic Search

Models have been embodied within the QinetiQ atmospheric radiation model (QARM) to compute enhancements during major solar particle events and the influence of any concurrent geomagnetic storms that lower the cut-off rigidity. Predictions are compared with available in-flight measurements and extended to give worst case estimates for a number of aircraft routes. It is found that during solar particle events

Clive Dyer; Fan Lei; Alex Hands; Peter Truscott

2007-01-01

152

Particle-Induced X-Ray Emission Analysis of Atmospheric Aerosols  

Microsoft Academic Search

We are developing a research program in ion-beam analysis (IBA) of atmospheric aerosols at the Union College Ion-Beam Analysis Laboratory to study the transport, transformation, and effects of airborne pollution in Upstate New York. The simultaneous applications of the IBA techniques of particle-induced X-ray emission (PIXE), Rutherford back-scattering spectrometry (RBS), particle-induced gamma-ray emission (PIGE), and proton elastic scattering analysis (PESA)

Colin Gleason; Charles Harrington; Katie Schuff; Maria Battaglia; Robert Moore; Colin Turley; Michael Vineyard; Scott Labrake

2010-01-01

153

Search for Fractional-Charge Particles in Meteoritic Material  

SciTech Connect

We have used an automated Millikan oil drop method to search for free fractional-charge particles in a sample containing in total 3.9 mg of pulverized Allende meteorite suspended in 259 mg of mineral oil. The average diameter of the drops was 26.5 {mu}m with the charge on about 42 500 000 drops being measured. This search was motivated by the speculation that isolatable, fractional-charge particles produced in the early Universe and present in our Solar System are more likely to be accumulated in asteroids than on Earth's surface. No evidence for fractional-charge particles was found. With 95% confidence, the concentration of particles with fractional-charge more than 0.25 e (e being the magnitude of the electron charge) from the nearest integer charge is less than 1.3x10{sup -21} particles per nucleon in the meteoritic material and less than 1.9x10{sup -23} particles per nucleon in the mineral oil.

Kim, Peter C.; Lee, Eric R.; Lee, Irwin T.; Perl, Martin L.; Halyo, Valerie; Loomba, Dinesh [Stanford Linear Accelerator Center, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Department of Physics, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2007-10-19

154

The role of biogenic, biomass burning and urban pollution aerosol particles in controlling key atmospheric processes in Amazonia  

NASA Astrophysics Data System (ADS)

As part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment, a research program run in the last 10 years had help to understand critical atmospheric processes in Amazonia. The vegetation in Amazonia is a direct source of aerosol particles to the atmosphere as well as a source of biogenic trace gases that generates particles trough gas-to-particle conversion. Biomass burning is also a large source of particles and trace gases to the atmosphere. Over the last 10 years, the LBA experiment has unveiled several key processes that control Amazonian composition and influence regional climate. A significant fraction (60-80%) of airborne particles can act as Cloud Condensation Nuclei (CCN), influencing cloud formation and development. The radiation balance is strongly influenced by biomass burning particles, and surface radiative forcing up to -250 w/m2 is measured. A network of 8 sites with AERONET sunphotometers measures aerosol optical depth (AOD) and derive aerosol size distribution and optical properties. Aerosols are composed of more than 70% of organic material, with significant absorption characteristics. The aerosol radiative forcing during the biomass burning season can reach very high values, and the increase in diffuse radiation increases the carbon uptake by the forest for AOD values smaller than 1.2 at 500nm. For large AOD, the solar flux is strongly reduced making the carbon uptake approach zero for AOD larger than 3.0. The composition of aerosols is mostly organic, with contribution of K, Ca, Si, and other trace elements. The aerosol has high capability to serve as Cloud Condensation Nuclei (CCN), contributing with high water vapor amounts to the significant cloud cover over the region. In the last 20 years, an urbanization process took over for most of the Amazonian region, increasing urban pollution that interacts with forest emissions to produce a quite unique pattern of aerosols and pollutants around large urban areas such as Manaus. Emissions from biomass burning travel over long distances and have significant impacts on radiation and precipitation over the South American continent. Precipitation is influenced by land use change as well as by the aerosol loading in the atmosphere, but no changes have been observed when rain rate is integrated over the Basin.

Artaxo, P.; Ferreira De Brito, J.; Barbosa, H. M.; Rizzo, L. V.; Sena, E. T.; Cirino, G.; Arana, A.; Yanez-Serrano, A. M.

2013-05-01

155

Materials for Active Engagement in Nuclear and Particle Physics Courses  

NASA Astrophysics Data System (ADS)

Physics education researchers have developed a rich variety of research-based instructional strategies that now permeate many introductory courses. Carrying these active-engagement techniques to upper-division courses requires effort and is bolstered by experience. Instructors interested in these methods thus face a large investment of time to start from scratch. This NSF-TUES grant, aims to develop, test and disseminate active-engagement materials for nuclear and particle physics topics. We will present examples of these materials, including: a) Conceptual discussion questions for use with Peer Instruction; b) warm-up questions for use with Just in Time Teaching, c) ``Back of the Envelope'' estimation questions and small-group case studies that will incorporate use of nuclear and particle databases, as well as d) conceptual exam questions.

Loats, Jeff; Schwarz, Cindy; Krane, Ken

2013-04-01

156

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

157

Boundary-layer charged-particle density profiles in an atmospheric pressure plasma flow  

Microsoft Academic Search

The charged-particle density profiles inside the boundary layer formed on a flat plate or a circular cylinder located in an atmospheric-pressure plasma flow were measured with electrostatic probes. Theoretical profiles were obtained through numerical solution of momentum, species, and energy conservation equations taking account of variable transport properties. Comparison of these results leads to the following conclusions: For the flat

M. Suzuki; A. Kanzawa

1979-01-01

158

Formation of the Spectrum of Sizes of Aerosol Particles in the Surface Layer of the Atmosphere.  

National Technical Information Service (NTIS)

A study of the spectrum of sizes of aerosol particles in the surface layer of the atmosphere which was carried out recently in the Soviet Union. It was found that in areas where the air is clear and there is high relative humidity, there is a multimodal d...

L. S. Ivlev

1974-01-01

159

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

160

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

161

Novel applications of atmospheric pressure plasma on textile materials  

NASA Astrophysics Data System (ADS)

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 is found to be more significant than the plasma, but differences in density, strength, and surface roughness are apparent for the pulp vs. paper plasma treatments. The plasma is also used to remove sizes of PVA and starch from poly/cotton and cotton fabric respectively. In both cases plasma successfully removes a significant amount of size, but complete size removal is not achieved. Subsequent washes (PVA) or scouring (cotton) to remove the size are less successful than a control, suggesting the plasma is crosslinking the size that is not etched away. However, at short durations in cold water using an oxygen plasma, slightly more PVA is removed than with a control. For the starch sized samples, plasma and scouring are never as successful at removing starch as a conventional enzyme, but plasma improves dyeability without need for scouring. Plasma is also used to graft chemicals to the surface of polypropylene and cotton fabric. HTCC, an antimicrobial is grafted to polypropylene with successful grafting indicated by x-ray photoemission spectroscopy (XPS), dye tests, and Fourier transform infrared spectroscopy (FTIR). Antimicrobial activity of the grafted samples is also characterized. 3ATAC, a vinyl monomer is also grafted to polypropylene and to cotton. Additives including Mohr's salt, potassium persulfate, and diacrylate are assessed to increase yield. Successful grafting of 3ATAC is confirmed by XPS and dye testing. A combination of all three additives is identified as optimum for maximizing graft yield.

Cornelius, Carrie Elizabeth

162

Seasonality of the chemistry in atmospheric new particle formation in southern Africa  

NASA Astrophysics Data System (ADS)

Atmospheric new particle formation has been observed in various different environments ranging from remote background regions to polluted megacities. In many environments it has also been shown to increase the concentration of particles in sizes that can act as cloud condensation nuclei and therefore affect the climate. New particle formation is essentially a two-step process, where the first step is nucleation in the nanometer size range, which is followed by a growth phase to climatically relevant sizes. While recent advances in experimental methods have enabled direct observations of atmospheric nucleation, aerosol particle chemistry during the growth phase following nucleation has been characterised in relatively few studies and never covered a full seasonal cycle. In this study we utilized one year of continuous online chemical composition measurements of submicron aerosol particles with an Aerosol Chemical Speciation Monitor (ACSM) together with concurrent size distribution measurements from 12 to 840 nm with a Differential Mobility Particle Sizer (DMPS). The measurements were carried out at Welgegund measurement station in South Africa, which is approximately 100 km west of Johannesburg from September 2010 to August 2011. During this period the frequency of new particle formation events was 78 % with 90 % data coverage. The high frequency of new particle formation events enabled us to study the chemistry of aerosol particle growth in 89 new particle formation events during the one year period. Organic aerosol and sulphate were the dominant constituents in the growth of newly formed particles at Welgegund. On average, organic aerosol constituted 49 % of the growth and sulphate 36 %. However, the ratio of organic aerosol and sulphate varied widely depending on whether the air masses originated in the clean sector or in the anthropogenic sector. Ammonium correlated with sulphate (correlation coefficient 0.83) and constituted on average 11 % of the growth, while nitrate was a minor constituent with a 4 % average fraction. We observed a clear seasonal pattern in the organic aerosol source rate with the highest values occurring during the local spring and summer.

Vakkari, Ville; Tiitta, Petri; Beukes, Johan P.; van Zyl, Pieter G.; Josipovic, Miroslav; Venter, Andrew D.; Jaars, Kerneels; Worsnop, Douglas R.; Kulmala, Markku; Laakso, Lauri

2014-05-01

163

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

164

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

165

Fine particle receptor modeling in the atmosphere of Mexico City.  

PubMed

Source apportionment analyses were carried out by means of receptor modeling techniques to determine the contribution of major fine particulate matter (PM2.5) sources found at six sites in Mexico City. Thirty-six source profiles were determined within Mexico City to establish the fingerprints of particulate matter sources. Additionally, the profiles under the same source category were averaged using cluster analysis and the fingerprints of 10 sources were included. Before application of the chemical mass balance (CMB), several tests were carried out to determine the best combination of source profiles and species used for the fitting. CMB results showed significant spatial variations in source contributions among the six sites that are influenced by local soil types and land use. On average, 24-hr PM2.5 concentrations were dominated by mobile source emissions (45%), followed by secondary inorganic aerosols (16%) and geological material (17%). Industrial emissions representing oil combustion and incineration contributed less than 5%, and their contribution was higher at the industrial areas of Tlalnepantla (11%) and Xalostoc (8%). Other sources such as cooking, biomass burning, and oil fuel combustion were identified at lower levels. A second receptor model (principal component analysis, [PCA]) was subsequently applied to three of the monitoring sites for comparison purposes. Although differences were obtained between source contributions, results evidence the advantages of the combined use of different receptor modeling techniques for source apportionment, given the complementary nature of their results. Further research is needed in this direction to reach a better agreement between the estimated source contributions to the particulate matter mass. PMID:20066907

Vega, Elizabeth; Lowenthal, Douglas; Ruiz, Hugo; Reyes, Elizabeth; Watson, John G; Chow, Judith C; Viana, Mar; Querol, Xavier; Alastuey, Andrés

2009-12-01

166

Energetic particle precipitation into the middle atmosphere: measurements and model predictions  

NASA Astrophysics Data System (ADS)

Precipitation of energetic particles - protons and electrons from large solar coronal mass ejections, the aurora, or the radiation belts - significantly affects the chemical composition of the atmosphere from the lower stratosphere to the lower thermosphere. The primary reactions are excitation, dissociation, and ionization of the main components of the atmosphere (N2 and O2), followed by fast ion-chemistry reactions forming NOx (N, NO, NO2) and HOx (H, OH, HO2, 2 H2O2). Both NOx and HOx contribute to catalytic destruction of ozone in the middle atmosphere, NOx in the stratosphere (below ~45 km), HOx in the mesosphere (above ~45 km). The impact of energetic particle precipitation onto the composition of the middle atmosphere, especially on the NOx budget and stratospheric ozone, has been investigated in a number of studies in the past, but there are still many open questions, both regarding the processes that lead to chemical changes during the particle events, and the long-term impact of those events on stratospheric composition and dynamics. We use models of different complexity from a one-dimensional ion-chemistry model to a global three-dimensional chemistry and transport model combined with observations of atmospheric trace gases from different satellite platforms to investigate the impact of energetic particle precipitation onto the chemical composition of the middle atmosphere. Focus of our investigations are, on the one hand, ion-chemistry processes during particle events, and on the other hand, the contribution of energetic electron precipitation to the middle atmosphere NOx and ozone budget. We find that some of the observed trace-gas changes during large solar particle events can only be explained by complex ion-chemistry. Models driven by ionization rates derived from observed electron and proton fluxes predict a large direct impact of energetic electrons onto the upper stratosphere and mesosphere, both during large solar proton events, and during geomagnetic storms; in contrast to the model predictions, observational evidence for a direct impact of energetic electrons to altitudes below 80 km is sparse and ambiguous. However, observations also show that the downwelling of NOx from the auroral region above 80 km during polar winter can affect the NOx budget of the polar stratosphere more than even very large solar events.

Sinnhuber, M.; Wieters, N.; Winkler, H.

2012-04-01

167

Brighter material on Deimos - A particle size effect in a carbonaceous material?  

NASA Technical Reports Server (NTRS)

The values obtained for brightness ratios between contiguous bright and dark areas on Deimos from Viking Orbiter images, together with the lack of a significant wavelength dependence of these ratios in the 0.4-0.6-micron range, are presently noted to be consistent with particle size fraction measurements of the Murchison CM meteorite. These data, and a near-coincidence of Deimos absolute reflectances with those of laboratory samples, render the present data consistent with both brighter and darker materials on Deimos being akin to carbonaceous chondrites; the material with smaller average particle size is associated with the brighter patches.

French, L. M.; Veverka, J.; Thomas, P.

1988-01-01

168

Field and laboratory studies of atmospheric reactive mercury: Gas-particle partitioning and sources  

NASA Astrophysics Data System (ADS)

Certain aspects of atmospheric reactive mercury (RM) source-receptor relationships are not well understood. The objective of this dissertation was to improve the understanding of these relationships in the following areas: (i) gas-particle partitioning, and; (ii) the local impacts of RM source emissions. A novel aerosol reactor was developed to study gas-particle partitioning of RM using synthetic atmospheric aerosol containing picogram concentrations of RM. The RM in the aerosol was collected in an offline mode with filters and sorbent, and analyzed with Thermal Desorption Analysis (TDA). The offline-TDA collection and analysis method was compared with a commercial real time ambient mercury analyzer and two wet analysis methods using ambient measurements. The offline-TDA method performed well in comparison to the established techniques. The dependencies of gas-particle partitioning coefficients upon temperature and particle composition were determined and parameterized from field studies and laboratory experiments. The volatility of RM increased with ambient temperature in urban aerosol and laboratory aerosol of ammonium sulfate and adipic acid. The dependence of RM gas-particle partitioning on particle composition were determined using synthetic atmospheric aerosol generated in the laboratory. RM partitioned predominantly to the particle phase in particles of sodium nitrate, sodium chloride and potassium chloride, but was much more volatile in particles made of ammonium sulfate, levoglucosan and adipic acid. The impacts of RM sources on local receptors were studied in southern Wisconsin and Mexico City. RM measurements were made over a year in Milwaukee, WI (urban) and Devil's Lake State Park, WI (rural). An urban excess of all three mercury species was detected in Milwaukee, WI. The urban excess was attributed to a higher density of mercury emissions in the Milwaukee, WI-Chicago, IL area. The impact of local sources of RM on both sites was found to dominate the atmospheric concentrations. PHg and RGM measurements were made in Mexico City over 2.5 weeks. Diurnal concentration variations with nocturnal maxima pointed to nightly transport of air into the city from the industrial area to the north. RM partitioned predominantly to the particle phase in most of the plumes.

Rutter, Andrew Philip

169

Atmospheric particle formation from the ozonolysis of alkenes in the presence of SO 2  

NASA Astrophysics Data System (ADS)

Laboratory studies on the formation of new particles have been performed in a flow tube in the system O 3/alkene/SO 2 using ?-pinene, trans-butene, and tetramethylethylene (TME) as model alkenes. Reactant concentrations were kept close to atmospheric conditions. In the absence of SO 2, no particle formation was observed. The number of newly formed particles measured in the presence of SO 2 was found to be H 2SO 4-controlled, whereas a distinct contribution of different organic products from the ozonolysis was not discovered. Scavenger experiments for OH radicals revealed that the main fraction of H 2SO 4 produced arose from OH+SO 2. An additional pathway for H 2SO 4, probably Criegee Intermediate+SO 2, accounted for 26% ( ?-pinene), 23% ( trans-butene), and 42% (TME) of the total amount of H 2SO 4 formed. For conditions where particle formation occurred in the flow tube, H 2SO 4 concentrations of a few 10 7 molecule cm -3 were calculated, similar to observations in the atmosphere. Under the experimental conditions used, an analysis of the particle volume indicated that the organic ozonolysis products did not influence the particle growth significantly.

Berndt, Torsten; Böge, Olaf; Stratmann, Frank

170

Harnessing Particle Modulation in an Electrodynamic Balance to Measure Optical Properties of Atmospheric Aerosols  

NASA Astrophysics Data System (ADS)

Aerosols play a key but complex role in the global energy budget. Observations of aerosols with high organic and carbonaceous content over large areas in the Indian Ocean signify the role of aerosols in our coupled climate system (1) and underscore the need to quantify their optical properties. To help achieve this, we have constructed an electrodynamic balance where isolated aerosols are levitated and investigated without any contamination by wall effects. The mass of the particle is measured by the DC electric field necessary to balance the gravitational force. Light scattering and Mie theory allow a precise determination of particle size and refractive index. We are also developing a novel technology that exploits particle modulation and lock in detection to measure optical absorption by a single aerosol particle. Both photo-acoustic and Raman spectroscopy are being used for this. We plan to present results on salt, carbonaceous, and mixed particles to demonstrate the feasibility of our approach. Models to calculate absorption by complex atmospheric particles will also be examined. (1) Ramanathan V, Crutzen PJ, Kiehl JT, Rosenfeld D, Atmosphere : Aerosols, climate, and the hydrological cycle, Science, 294, 2119-2124, 2001

Schmidt, C. C.; Dubey, M. K.; Stephens, J. R.

2002-05-01

171

Properties and effects of dust particles suspended in the Martian atmosphere  

NASA Technical Reports Server (NTRS)

Direct measurements of the optical depth above the two Viking landers are presented for a period covering the summer, fall, and winter seasons in the Northern Hemisphere, a time period during which two global dust storms occurred. The data are used to define the properties of suspended dust particles in the Martian atmosphere and to assess their role in a number of meteorological and geological processes. Major conclusions are that (1) both the radiative effects of dust particles and the thermodynamical effects of large-scale atmospheric motions have a significant impact on the vertical temperature structure; (2) Pertinent feedback effects play an important part in the generation of some local dust storms, in the expansion of local dust storms to global proportions, and in the subsequent decay of global dust storms; (3) An important mechanism for the removal of dust particles from the atmosphere is the CO2 condensation-sedimentation process; and (4) that the polar laminae are constructed from atmospheric dust and water ice is hypothesized.

Pollack, J. B.; Colburn, D. S.; Flasar, F. M.; Kahn, R.; Carlston, C. E.; Pidek, D.

1979-01-01

172

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.

Cooney, Daniel J; Hickey, Anthony J

2008-01-01

173

Removal of Ultra-Fine Aerosol Particles From the Atmospheric Boundary Layer During Precipitation  

NASA Astrophysics Data System (ADS)

New aerosol particles are formed in atmospheric environment as a result of the secondary particle production, or homogeneous nucleation of gaseous species. Direct emissions of small particles into atmosphere are related to road traffic, power plants and additional mechanisms involving ion-assisted nucleation. These processes contribute to ultra-fine particle (UFP) presence in atmosphere (defined as particles with diameter less than 100 nm), which can have health effects and can impact cloud properties. UFP formed in the boundary layer (BL) need to grow up to a diameter dp ~ 100 nm to become activated as cloud droplets (CD). The time required to reach dp=100 nm is about 2-3 days for a typical growth rate of 5 nm hr-1, while significant variability was reported from experimental data. If precipitation occurs, most UFP are too small to become CD and some particles are removed by scavenging processes. A model to estimate the UFP wet removal from the BL by rainfall and coagulation is presented. The scavenging coefficient that describes the decay of aerosol mass in various size bins is a function of aerosol size (dp), rainfall rate (R), and BL background aerosol. The model is applied to determine the UFP characteristic removal time during precipitation, due to below-cloud scavenging by falling raindrops, coagulation with background aerosol, mixing in-cloud followed by coagulation with cloud hydrometeors. Results show that during rain events, the 0.5-folding time is t05 ~ 1 hr for R ~ 1 mm hr-1 for newly created particles (dp < 10 nm) and t05 ~ 1 day for larger UFP (dp ~ 10-100 nm). The likelihood of UFP removal at locations with specific precipitation regimes is also illustrated.

Andronache, C.

2004-05-01

174

Estimating bacteria emissions from inversion of atmospheric transport: sensitivity to modelled particle characteristics  

NASA Astrophysics Data System (ADS)

Model-simulated transport of atmospheric trace components can be combined with observed concentrations to obtain estimates of ground-based sources using various inversion techniques. These approaches have been applied in the past primarily to obtain source estimates for long-lived trace gases such as CO2. We consider the application of similar techniques to source estimation for atmospheric aerosols, using as a case study the estimation of bacteria emissions from different ecosystem regions in the global atmospheric chemistry and climate model ECHAM5/MESSy-Atmospheric Chemistry (EMAC). Source estimation via Markov Chain Monte Carlo is applied to a suite of sensitivity simulations, and the global mean emissions are estimated for the example problem of bacteria-containing aerosol particles. We present an analysis of the uncertainties in the global mean emissions, and a partitioning of the uncertainties that are attributable to particle size, activity as cloud condensation nuclei (CCN), the ice nucleation scavenging ratios for mixed-phase and cold clouds, and measurement error. For this example, uncertainty due to CCN activity or to a 1 ?m error in particle size is typically between 10% and 40% of the uncertainty due to observation uncertainty, as measured by the 5-95th percentile range of the Monte Carlo ensemble. Uncertainty attributable to the ice nucleation scavenging ratio in mixed-phase clouds is as high as 10-20% of that attributable to observation uncertainty. Taken together, the four model parameters examined contribute about half as much to the uncertainty in the estimated emissions as do the observations. This was a surprisingly large contribution from model uncertainty in light of the substantial observation uncertainty, which ranges from 81-870% of the mean for each of ten ecosystems for this case study. The effects of these and other model parameters in contributing to the uncertainties in the transport of atmospheric aerosol particles should be treated explicitly and systematically in both forward and inverse modelling studies.

Burrows, S. M.; Rayner, P. J.; Butler, T.; Lawrence, M. G.

2013-06-01

175

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

176

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

177

Mass-particle size distributions of atmospheric dust and the dry deposition of dust to the remote ocean  

NASA Astrophysics Data System (ADS)

Size-separated mineral aerosol samples were collected and analyzed to investigate the relationships between the mass-particle size distributions (MSDs) of dust particles and the dust loadings in the atmosphere. The data also were used to assess the changes in the MSDs of dust in relation to transport processes and especially the associated effects on dry deposition. Atmospheric dust concentrations, as indicated by aluminum or scandium, in samples collected from three sites in the remote North Atlantic were higher than those in samples collected during a cruise in the North Pacific on board the R/V Moana Wave. However, the mass median diameters (MMDs) for the North Pacific samples were both larger on average (˜3 ?m versus ˜2 ?m aerodynamic equivalent diameter) and more variable than those from the North Atlantic; this difference was attributed to wet conditions and particle aggregation over the North Pacific. In addition, for the ensemble of all samples the geometric standard deviations of the mass-particle size distributions, which are analogous to the sorting values used to characterize sedimentary materials, tended to vary inversely and nonlinearly with the mass median diameters. Model-derived dry deposition velocities for the samples were at most weakly related to either the dust concentrations or the MMDs. However, the dry deposition velocities for two subsets of samples were correlated with the geometric standard deviations of the distributions; this is further evidence that the mass flux of dust via dry deposition can be controlled by a relatively small fraction of aerodynamically large particles.

Arimoto, R.; Ray, B. J.; Lewis, N. F.; Tomza, U.; Duce, R. A.

1997-07-01

178

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

NASA Astrophysics Data System (ADS)

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still unclear. This study, investigated the influence of feedstock particle size in RPS of aluminum nitride (AlN) coatings, through plasma nitriding of aluminum (Al) feedstock powders. It was possible to fabricate AlN-based coatings through plasma nitriding of all kinds of Al powders in atmospheric plasma spray (APS) process. The nitriding ratio was improved with decreasing the particle size of feedstock powder, due to improving the nitriding reaction during flight. However, decreasing the particle size of feedstock powder suppressed the coatings thickness. Due to the loss of the powder during the injection, the excessive vaporization of fine Al particles and the completing nitriding reaction of some fine Al particles during flight. The feedstock particle size directly affects on the nitriding, melting, flowability, and the vaporization behaviors of Al powders during spraying. It concluded that using smaller particle size powders is useful for improving the nitriding ratio and not suitable for fabrication thick AlN coatings in reactive plasma spray process. To fabricate thick AlN coatings through RPS, enhancing the nitriding reaction of Al powders with large particle size during spraying is required.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2011-03-01

179

Wavelength-dependent optical extinction of carbonaceous particles in atmospheric aerosols and interstellar dust.  

PubMed

Optical extinction spectra for particles of structurally disordered carbonaceous material (carbon black, soot) are discussed in terms of the effects of size and shape and the difference between coagulated and coalesced particles. For this purpose, the orientation-averaged specific extinction for several compact and open aggregates of spherical particles is calculated and compared with the specific extincton by homogeneous particles, i.e., volume-equivalent sphere and elongated spheroids. The extinction spectra are calculated for wavelengths from 0.2 to 1000 microm by use of the optical constants for the carbonaceous materials of Jäger et al. [Astron. Astrophys. 332, 291 (1998)] and Schnaiter et al. [Astrophys. J. 498, 486 (1998)]. Comparisons with the model case of particles composed of graphite and with measurements of diesel soot aerosols are made. PMID:12463258

Quinten, Michael; Kreibig, Uwe; Henning, Thomas; Mutschke, Harald

2002-11-20

180

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

181

Reports of workshops on Probe Measurements of Particles and Radiation in the Atmosphere of Titan  

NASA Technical Reports Server (NTRS)

The planned 1995 joint ESA-NASA Cassini mission to the Saturnian system will include an atmospheric probe to be dropped into the atmosphere of Titan for in situ measurements during descent. Because of the unique properties of the Titan atmosphere it is necessary to consider the peculiar requirements for such measurements and applicable techniques. The proceedings of two workshops dealing with the measurement of particles and radiation in the atmosphere of Titan are presented in two parts. The first part dealt with the measurement of particulate matter in the atmosphere of Titan. The second part dealt with the measurement of radiation in the atmosphere of Titan. The proceedings were first published and distributed informally, and are presented with only minor editorial changes. In the report of the particulate matter workshop, discussions of the mission background, the importance of the measurements, and descriptions of the desired information are followed by a description of appropriate measurement techniques and conclusions and recommendations. The proceeding for the workshop on radiation measurement and imaging contains a discussion of the importance of radiation measurements and imaging, and presents a summary of participants' experience with such measurements made from entry probes. This is followed by a description of appropriate measurement techniques and conclusions and recommendations.

Ragent, Boris (comp. and ed.); Swenson, Byron L. (comp. and ed.)

1990-01-01

182

Coated or Embedded? Organic Matter as a Host for Individual Ambient Atmospheric Aerosol Particles (Invited)  

NASA Astrophysics Data System (ADS)

Organic matter is a prominent form of atmospheric aerosol particle. It commonly occurs with soot, sulfate, metals, or mineral dust in individual, internally mixed particles and is important when estimating radiative and health effects of aerosols. The details of these mini-assemblages are well observed when using transmission electron microscopy (TEM). When organic matter hosts soot particles, it enhances the light absorption of the soot and thus its warming effects. We determined the shapes of organic matter embedding soot using electron tomography (ET) with a transmission electron microscope, calculated the radiative forcing of such particles, and compared them to those of various coating and mixing models. Organic matter in particles collected from the vicinity of Mexico City (as part of the MILAGRO - Megacity Initiative: Local and Global Research Observations - campaign conducted in March 2006) also hosts metal-bearing nanoparticles that can include Fe, Zn, Mn, Pb, Hg, Sn, Cr, Ni, Ti, V, or Ag as major constituents. Nanoparticles of Hg are especially abundant. The nanoparticles are interesting because of their small sizes and high surface-to-volume ratios, both of which make them highly reactive in the human body and can cause negative health effects. In these and samples from other areas, we commonly find organic matter coating or otherwise associated with (hosting) inorganic aerosol particles of all types. Although the atmospheric community commonly speaks of coatings onto aerosol particles, in the case of organic matter, a more apt term might be embedding rather than coating. Finally, such hosting by organic matter can influence the climate and health effects of aerosol particles.

Buseck, P. R.; Adachi, K.

2009-12-01

183

Characterization of organic coatings on hygroscopic salt particles and their atmospheric impacts  

NASA Astrophysics Data System (ADS)

The photooxidation of ?-pinene in the presence of NO 2, with and without added NaNO 3 seed particles, has been studied in a large-diameter flow tube. Particles formed by homogeneous nucleation and by condensation on the pre-existing seeds were sampled at various stages of the reaction, dried using four diffusion dryers, size selected at different mobility diameters ( dm) using a differential mobility analyzer (DMA), and characterized with a single particle mass spectrometer (SPLAT II). It was found that homogeneously nucleated particles are spherical, have a density ( ?) of 1.25 ± 0.02 g cm -3 (±2 ?) and contain a significant amount of organic nitrates. The mass spectra of the low volatility products condensed on the NaNO 3 seed particles were found to be virtually the same as in the case of homogeneous nucleation. The data show that the presence of even a submonolayer of organics on the NaNO 3 particles causes water retention that leads to a decrease in particle density and that the amount of water retained increases with organic coating thickness. Thicker coatings appear to inhibit water evaporation from the particle seeds altogether. This suggests that in the atmosphere, where low volatility organics are plentiful, some hygroscopic salts will retain water and have different densities and refractive indices than expected in the absence of the organic coating. This water retention combined with the organic shell on the particles can potentially impact light scattering by these particles and activity as cloud condensation nuclei (CCN), as well as heterogeneous chemistry and photochemistry on the particles.

Zelenyuk, Alla; Ezell, Michael J.; Perraud, Véronique; Johnson, Stanley N.; Bruns, Emily A.; Yu, Yong; Imre, Dan; Alexander, M. Liz; Finlayson-Pitts, Barbara J.

184

Nano- and Microscale Particles in Vortex Motions in Earth's Atmosphere and Ionosphere  

SciTech Connect

Vortex motions in the atmosphere are shown to be closely connected with dynamics of the dust nano- and microscale particles. The mechanism by which nano- and microscale particles are transported from the troposphere into the lower stratosphere by synoptic-scale vortices, simulated by the soliton solutions to the Charney-Obukhov equations (Rossby vortices), is described. Redistribution of dust particles in the ionosphere as a result of vortical motions is discussed. It is shown that excitation of acoustic-gravitational vortices at altitudes of 110-130 km as a result of development of acoustic-gravitational wave instability, associated with nonzero balance of heat fluxes, owing to solar radiation, water vapors condensation, infrared emission of the atmosphere, and thermal conductivity, leads to a substantial transportation of dust particles and their mixing at altitudes of 110-120 km. One of the ways of transportation of dust particles in the ionosphere is shown to be vertical flows (streamers), which are generated by dust vortices as a result of development of parametric instability.

Popel, S. I.; Izvekova, Yu. N. [Institute for Dynamics of Geospheres, Leninsky prospect 38, building 1, 119334 Moscow (Russian Federation); Shukla, P. K. [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2010-12-14

185

Lanthanum and lanthanides in atmospheric fine particles and their apportionment to refinery and petrochemical operations in Houston, TX  

NASA Astrophysics Data System (ADS)

A study was conducted in Houston, TX focusing on rare earth elements (REEs) in atmospheric fine particles and their sources. PM 2.5 samples were collected from an ambient air quality monitoring site (HRM3) located in the proximity of a large number of oil refineries and petrochemical industries to estimate the potential contributions of emissions from fluidized-bed catalytic cracking operations to ambient fine particulate matter. The elemental composition of ambient PM 2.5, several commercially available zeolite catalysts, and local soil was measured after microwave assisted acid digestion using inductively coupled plasma—mass spectrometry. Source identification and apportionment was performed by principal component factor analysis (PCFA) in combination with multiple linear regression. REE relative abundance sequence, ratios of La to light REEs (Ce, Pr, Nd, and Sm), and enrichment factor analysis indicated that refining and petrochemical cat cracking operations were predominantly responsible for REE enrichment in ambient fine particles. PCFA yielded five physically meaningful PM 2.5 sources: cat cracking operations, a source predominantly comprised of crustal material, industrial high temperature operations, oil combustion, and sea spray. These five sources accounted for 82% of the total mass of atmospheric fine particles (less carbon and sulfate). Factor analysis confirmed that emissions from cat cracking operations primarily contributed to REE enrichment in PM 2.5 even though they comprised only 2.0% of the apportioned mass. Results from this study demonstrate the need to characterize catalysts employed in the vicinity of the sampling stations to accurately determine local sources of atmospheric REEs.

Kulkarni, Pranav; Chellam, Shankararaman; Fraser, Matthew P.

186

EXPERIMENTAL STUDIES ON PARTICLE IMPACTION AND BOUNCE: EFFECTS OF SUBSTRATE DESIGN AND MATERIAL. (R825270)  

EPA Science Inventory

This paper presents an experimental investigation of the effects of impaction substrate designs and material in reducing particle bounce and reentrainment. Particle collection without coating by using combinations of different impaction substrate designs and surface materials was...

187

Determination of the particle size distribution and chemical composition of semi-volatile organic compounds in atmospheric fine particles with a diffusion denuder sampling system  

NASA Astrophysics Data System (ADS)

Correct assessment of the factors associated with visibility impairment is dependent on accurate determination of the chemical composition as a function of size of particles present in the atmosphere. Collection of particles on a filter results in underestimation of particulate organic compounds due to losses from the semi-volatile organic fraction during sample collection, i.e. a "negative sampling artifact". These semi-volatile organic compounds lost from particles collected on a filter can be correctly measured using a diffusion denuder sampling system. This paper describes a multi-system, multi-channel, high-volume diffusion denuder sampler for the accurate determination of the particle size distribution and chemical composition of semi-volatile organic compounds in atmospheric fine particles. Data obtained in Provo, UT and Los Angeles, CA on the chemical composition and particle size distribution of semi-volatile organic compounds in atmospheric fine particles indicate that the majority of the semi-volatile organic compounds lost from particles during sampling were present in particles in the 0.4-0.8 ?m size range in the atmospheres sampled. Organic compounds lost from the particles during sampling include paraffinic compounds, aromatic compounds and organic acids and esters.

Tang, H.; Lewis, E. A.; Eatough, D. J.; Burton, R. M.; Farber, R. J.

188

Automated inspection of tubular material based on magnetic particle inspection  

NASA Astrophysics Data System (ADS)

Automatic industrial surface inspection methodology based on Magnetic Particle Inspection is developed from image acquisition to defect classification. First the acquisition system is optimized, then tubular material images are acquired, reconstructed then stored. The characteristics of the crack-like defects with respect to its geometric model and curvature are used as a priori knowledge for mathematical morphology and linear filtering. After the segmentation and binarization of the image, vast amount of defect candidates exist. Finally classification is performed with decision tree learning algorithm due to its robustness and speed. The parameters for mathematical morphology, linear filtering and classification are analyzed and optimized with Design Of Experiments based on Taguchi approach. The most significant parameters obtained may be analyzed and tuned further. Experiments are performed on tubular materials and evaluated by its accuracy and robustness by comparing ground truth and processed images. The result is promising with 97 % True Positive and only 0.01 % False Positive rate on the testing set.

Mahendra, Adhiguna; Stolz, Christophe; Meriaudeau, Fabrice; Petit, Sebastien; Noel, Alexandre; Degoutin, Fabien

2012-02-01

189

Numerical modelling of spontaneous crack generation in brittle materials using the particle simulation method  

Microsoft Academic Search

Purpose – The main purpose of this paper is to present and use the particle simulation method to explicitly simulate the spontaneous crack initiation phenomenon in brittle materials, and to compare the particle simulation results with experimental ones on the laboratory scale. Design\\/methodology\\/approach – Using the particle simulation method, the brittle material is simulated as an assembly of particles so

Chongbin Zhao; T. Nishiyama; A. Murakami

2006-01-01

190

Nature of the Martian surface as inferred from the particle-size distribution of lunar-surface material.  

NASA Technical Reports Server (NTRS)

Analysis of lunar particle size distribution data indicates that the surface material is composed of two populations. One population is caused by comminution from the impact of the larger-sized meteorites, while the other population is caused by the melting of fine material by the impact of smaller-sized meteorites. The results are referred to Mars, and it is shown that the Martian atmosphere would vaporize the smaller incoming meteorites and retard the incoming meteorites of intermediate and large size, causing comminution and stirring of the particulate layer. The combination of comminution and stirring would result in fine material being sorted out by the prevailing circulation of the Martian atmosphere and the material being transported to regions where it could be deposited. As a result, the Martian surface in regions of prevailing upward circulation is probably covered by either a rubble layer or by desert pavement; regions of prevailing downward circulation are probably covered by sand dunes.

Mason, C. C.

1971-01-01

191

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

Microsoft Academic Search

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

Christian Weller; Hartmut Herrmann

2010-01-01

192

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

Microsoft Academic Search

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

C. Weller; A. Tilgner; H. Herrmann

2010-01-01

193

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

194

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

195

Study of nitro-polycyclic aromatic hydrocarbons in fine and coarse atmospheric particles  

Microsoft Academic Search

The purpose of the present study was to evaluate six nitro-polycyclic aromatic hydrocarbons (NPAHs) in fine (<2.5?m) and coarse (2.5–10?m) atmospheric particles in an urban and industrial area located in the Metropolitan Area of Porto Alegre (MAPA), RS, Brazil. The method used was of NPAHs isolation and derivatization, and subsequent gas chromatography by electron capture detection (CG\\/ECD). Results revealed a

Elba Calesso Teixeira; Karine Oliveira Garcia; Larissa Meincke; Karen Alam Leal

2011-01-01

196

Climatic effects of cloud particles in the atmospheres of Earth-like extrasolar planets  

NASA Astrophysics Data System (ADS)

ABSTRACT Clouds can have an important effect on the climate (and thereby also on the habitability) of terrestrial planets. While clouds in the upper atmosphere increase atmospheric cooling by scattering of the incoming stellar radiation, clouds in the lower atmosphere are leading to an enhanced greenhouse effect, resulting in higher surface temperatures. Due to the shortage of observational detail regarding the atmospheres of terrestrial extrasolar planets, particular studies of clouds are limited to basic questions about the predominant processes at work, which have to be adressed. In this contribution we focus on the climatic effects of water droplet distributions in the lower tropospheres of Earth-like extrasolar planets. As a first approximation, parametrized distribution functions are used in our study for the description of the cloud particles. The distribution function used here is the log-normal distribution, which is known to be a good approximation to observed size spectra of cumulus clouds in the Earths atmosphere (cf. [3]). This size distribution function is given by the expression f(a) = N p 2? a ln ?g exp ? -(ln a - ln an)2 2(ln ?g)2 ? (1) and depends on the three parameters: particle number concentration N, geometric standard deviation ?g and the median radius an. The particle radius is denoted by a, respectively. Our simplified cloud description scheme is coupled with a one-dimensional radiative-convective climate-model (see e.g. [4] and [2] for a general overview of the model) in order to study the basic effects on the climate. Optical properties of the cloud particles are, thereby, calculated by Mie-theory (cf. e.g. [1]), assuming spherical particles composed of pure liquid water and have been included in the models radiative transfer scheme. Results for e.g. different types of central stars are presented and compared with the respective cloud-free situations. References [1] C.F. Bohren and D.R. Huffman, Absorption and scattering of light by small particles, 1983, Wiley [2] Grenfell et al. (2007) Planetary and Space Science, Vol. 55, Issue 5, 661-671 [3] A. A. Kokhanovsky, Cloud Optics, 2006, Springer [4] Segura et al. (2003) Astrobiology, Vol. 3, No. 4, 689- 708

Kitzmann, D.; Patzer, A. B. C.; von Paris, P.; Grenfell, L.; Rauer, H.

2008-09-01

197

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

198

Ion precipitation in planetary upper atmospheres: test particle simulations and implications for escape  

NASA Astrophysics Data System (ADS)

A 3-D Monte Carlo energetic particle transport model has been developed and successfully applied to ion precipitation into planetary upper atmospheres in our solar system (viz., Earth, Mars, Jupiter, and Saturn), and can be readily be extended using a full Lorentz motion formu-lation in the absence of strong dipole planetary magnetic fields. This model can be used with a variety of other models to assess the influence of hot ion precipitation on the thermosphere and exosphere of planetary atmospheres and the subsequent sputtering and escape. For instance in the case of Mars, a pick-up ion transport model already exists to allow for particle acceleration exerted by the convection electric field used in conjunction with existing model results from the Mars Thermosphere General Circulation Model (MTGCM) and the BATS-R-US global MHD model. The loss of exospheric neutrals through ionization, in which they become pick-up ions in the solar wind, can be calculated to examine the relative contribution of the various ionization processes. Solar wind protons as well as pick-up ions from a planetary exosphere routinely enter and alter their upper atmosphere. A study of the pick-up ion escape, sputtering, ion-ization, excitation, and energy deposition will be reviewed and discussed, resulting in a robust examination of the influence of energetic ion transport on planetary upper atmospheres.

Parkinson, Christopher; Liemohn; Fang, Xiaohua

199

Atmospheric release advisory capability: Real-time modeling of airborne hazardous materials  

Microsoft Academic Search

The Atmospheric Release Advisory Capability (ARAC) at Lawrence Livermore National Lab. is a centralized federal project for assessing atmospheric releases of hazardous materials in real time. Since ARAC began making assessments in 1974, the project has responded to over 60 domestic and international incidents. ARAC can model radiological accidents in the US within 30 to 90 min., using its operationally

Thomas J. Sullivan; James S. Ellis; Connee S. Foster; Kevin T. Foster; Ronald L. Baskett; John S. Nasstrom; Walter W. Schalk III

1993-01-01

200

Atmospheric Release Advisory Capability: Real-Time Modeling of Airborne Hazardous Materials  

Microsoft Academic Search

The Atmospheric Release Advisory Capability (ARAC) at Lawrence Livermore National Laboratory is a centralized federal project for assessing atmospheric releases of hazardous materials in real time. Since ARAC began making assessments in 1974, the project has responded to over 60 domestic and international incidents. ARAC can model radiological accidents in the United States within 30 to 90 min, using its

Thomas J. Sullivan; James S. Ellis; Connee S. Foster; Kevin T. Foster; Ronald L. Baskett; John S. Nasstrom; Walter W. Schalk III

1993-01-01

201

Trends on atmospheric new particle formation - 16 years of observations in boreal forest  

NASA Astrophysics Data System (ADS)

Research on new particle formation (NPF) in the atmosphere has been very active during the last two decades. This phenomenon has been observed in various environments around the world [1]. One of the longest and most comprehensive data sets of atmospheric aerosol properties is available from the University of Helsinki SMEAR II station in Hyytiälä, southern Finland [2]. Ambient aerosol size distributions have been measured at Hyytiälä since January 1996 with a DMPS system covering particle size range 3 - 1000 nm (3 - 500 nm until end of 2004; see Aalto et al., 2001 [3]). Aerosol measurements are complemented by measurements of basic meteorological variables, trace gas concentrations (SO2, O3, CO, CO2, NO, NOx), and quantities related to the soil and forest surrounding the station. Until end of 2011 we have observed 1337 days with regional NPF events, i.e. formation of new 3 nm particles followed by particle growth to sizes of 30-50 nm typically within 10-20 hours. The number of nucleation events detected at Hyytiälä varies from year to year in the range 60 - 120 per year. The reasons behind this quite substantial variation are not yet found. We have, however, established that the variation of the galactic cosmic ray intensity due to the 11 year solar cycle is not connected to the particle formation intensity at Hyytiälä [4]. Mean values and observed trends in the quantities relative to NPF are listed in Table 1. There is no significant trend in the formation rates of 3 nm particles. In contrast, the growth rates are increasing by 3% per year relative to their 16 year mean value. Concentrations of sulphuric acid, which is the most important precursor vapor in atmospheric NPF, can be approximated with a simple proxy model [5]. This proxy takes into account the source from SO2 and the condensation sink by pre-existing particles. Both the SO2 concentration and CS are decreasing in Hyytiälä, but the relative change in SO2 is larger. This leads to a decreasing trend of 4% per year also in the H2SO4 proxy concentration, and suggests that the observed increase in the particle growth rates could be caused by increased concentrations of organic compounds and their oxidation products. As the emissions of these biogenic organic compounds are highly temperature dependent, increasing global temperatures can lead to a larger fraction of newly formed particles reaching cloud condensation nuclei sizes and this way NPF becoming more significant to climate.

Nieminen, T.; Dal Maso, M.; Petäjä, T.; Aalto, P. P.; Kerminen, V.-M.; Hari, P.; Kulmala, M.

2012-04-01

202

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

203

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

204

Atmospheric corrosion of batten and enclosure materials for flat-plate solar collectors  

SciTech Connect

As part of the Solar Reliability and Materials Program at Argonne National Laboratory, the atmospheric-corrosion-monitoring project is to assess the materials used for battens and enclosures for flat-plate solar collectors. Sensors at nine test sites have provided atmospheric data. Other data have been obtained by analyzing corrosion samples that were exposed for varying periods of time. This interim report summarizes the results of the first test period.

Not Available

1980-09-01

205

The inclusion of atmospheric particles into the bark suber of ash trees.  

PubMed

A slow deposition of atmospheric components occurs on tree barks. One part of them can be incorporated into bark tissues. This work demonstrates that mineral particles are present inside the suber tissue in four-year-old ash tree stems. Most of these particles are smaller than 2 microm. Scanning electronic microscope studies - using energy dispersive X-ray spectroscopy (SEM-EDX) - on stem cuttings show that they are located either inside the dead suber cells or between these cells. Numerous particles are composed of clay, quartz, feldspar or mica. Others, clearly of anthropogenic origin, are metallic fragments composed of Fe, Ni, Cr, Pb, etc. Spherical fly ashes were found, composed of Si, Al or Fe, and demonstrating an anthropogenic formation. Such particles were isolated and purified from suber ashes obtained at 550 degrees C, after aqueous and acidic treatments, and their composition was established through SEM-EDX. These results reinforce the idea that the suber of tree barks alone can be considered as archives for atmospheric deposition. PMID:19846195

Catinon, Mickaėl; Ayrault, Sophie; Boudouma, Omar; Asta, Juliette; Tissut, Michel; Ravanel, Patrick

2009-11-01

206

Atmospheric Solids Analysis Probe Mass Spectrometry: A New Approach for Airborne Particle Analysis  

SciTech Connect

Secondary organic aerosols (SOA) formed in the atmosphere from the condensation of semivolatile oxidation products are a significant component of airborne particles which have deleterious effects on health, visibility, and climate. In this study, atmospheric solids analysis probe mass spectrometry (ASAP-MS) is applied for the first time to the identification of organics in particles from laboratory systems as well as from ambient air. SOA were generated in the laboratory from the ozonolysis of r-pinene and isoprene, as well as from NO3 oxidation of r-pinene, and ambient air was sampled at forested and suburban sites. Particles were collected by impaction on ZnSe disks, analyzed by Fourier transform-infrared spectroscopy (FT-IR) and then transferred to an ASAP-MS probe for further analysis. ASAP-MS data for the laboratory-generated samples show peaks from wellknown products of these reactions, and higher molecular weight oligomers are present in both laboratory and ambient samples. Oligomeric products are shown to be present in the NO3 reaction products for the first time. A major advantage of this technique is that minimal sample preparation is required, and complementary information from nondestructive techniques such as FT-IR can be obtained on the same samples. In addition, a dedicated instrument is not required for particle analysis. This work establishes that ASAP-MS will be useful for identification of organic components of SOA in a variety of field and laboratory studies.

Bruns, Emily A.; Perraud, Veronique M.; Greaves, John; Finlayson-Pitts, Barbara J.

2010-07-15

207

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

208

Chemical imaging analysis of environmental particles using the focused ion beam/scanning electron microscopy technique: microanalysis insights into atmospheric chemistry of fly ash.  

PubMed

Airborne fly ash from coal combustion may represent a source of bioavailable iron (Fe) in the open ocean. However, few studies have focused on Fe speciation and distribution in coal fly ash. In this study, chemical imaging of fly ash has been performed using a dual-beam focused ion beam/scanning electron microscope (FIB/SEM) system for a better understanding of how simulated atmospheric processing can modify the morphology, chemical composition and element distribution within individual particles. A novel approach has been applied for cross-sectioning fly ash particles with the FIB in order to explore element distribution within the interior of individual particles. Our results indicate that simulated atmospheric processing can cause disintegration of aluminosilicate glass, a dominant material in fly ash particles. Fe present in the inner core of fly ash spheres within the aluminosilicate phase is more easily mobilized compared with Fe oxides present as surface aggregates on the exterior of fly ash spheres. Fe dissolution depends strongly on Fe speciation in fly ash particles. The approach for preparation of a cross-sectioned specimen described here opens up new opportunities for particle microanalysis, particularly with respect to inorganic refractive materials like fly ash and mineral dust. PMID:23207643

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

2013-01-21

209

Continuous scanning of the mobility and size distribution of charged clusters and nanometer particles in atmospheric air and the Balanced Scanning Mobility Analyzer BSMA  

Microsoft Academic Search

Measuring of charged nanometer particles in atmospheric air is a routine task in research on atmospheric electricity, where these particles are called the atmospheric ions. An aspiration condenser is the most popular instrument for measuring atmospheric ions. Continuous scanning of a mobility distribution is possible when the aspiration condenser is connected as an arm of a balanced bridge. Transfer function

H. Tammet

2006-01-01

210

Scale-Dependence of Particle Size Distributions in the Atmosphere: New Theories, Observations and Implications  

NASA Astrophysics Data System (ADS)

Aerosols, clouds and precipitation can be generally considered as stochastic, multi-body, polydisperse systems affected by various nonlinear/random forces and mutual interactions. Current dominant theories/models for particle size distributions have been formulated for individual particles. Such kinetic models, which demand that the dynamical equations be formulated and solved on a numerical grid size as small as ~ 1 mm and to exactly know the initial and boundary conditions, are unrealistic. On the other hand, in many real-world applications such as climate models and remote sensing, what really matters is the "thermodynamic" size distributions, i.e., size distributions averaged over scales much larger than the Kolmogorov microscale, instead of those on local microscopic scales. In this study, we argue that to address many issues related to atmospheric particle systems, mesoscopic and macroscopic theories are needed in addition to kinetic models. Presented are new advances in a systems theory that may be used to study and represent size distributions of atmospheric particles. The systems theory integrates ideas from statistical mechanics, information theory, and fractal geometry to overcome the insuperable difficulties facing kinetic models. Besides its consistence with observations, a major result of this theory is prediction of the scale-dependence of size distributions, i.e., individual size distributions depend on the scale over which they are sampled/simulated. To understand the details of scale-dependence and its relationship with fluctuations, we apply multiscale analysis approaches (e.g., auto-correlation analysis, spectral analysis, and fractal analysis) to measurements of aerosol and cloud size distributions collected under a variety of conditions. Based on the results, we address such questions as whether the scale-dependence is scaling or if there is a saturation scale beyond which size distribution will not change. Implications of the scale-dependence for related subjects such as including cloud properties in climate models are discussed. We further explore new frontiers, including a macroscopic theory analogous to thermodynamics for molecular systems, the fluctuation-dissipation theorem for the atmospheric particle systems, and the shift from the existing paradigm of scale-independent framework to a scale-dependent one by considering these particle systems as elements within the hierarchy of the atmosphere.

Liu, Y.; Daum, P. H.

2001-05-01

211

In situ measurements of gas/particle-phase transitions for atmospheric semivolatile organic compounds  

PubMed Central

An understanding of the gas/particle-phase partitioning of semivolatile compounds is critical in determining atmospheric aerosol formation processes and growth rates, which in turn affect global climate and human health. The Study of Organic Aerosol at Riverside 2005 campaign was performed to gain a better understanding of the factors responsible for aerosol formation and growth in Riverside, CA, a region with high concentrations of secondary organic aerosol formed through the phase transfer of low-volatility reaction products from the oxidation of precursor gases. We explore the ability of the thermal desorption aerosol gas chromatograph (TAG) to measure gas-to-particle-phase transitioning for several organic compound classes (polar and nonpolar) found in the ambient Riverside atmosphere by using in situ observations of several hundred semivolatile organic compounds. Here we compare TAG measurements to modeled partitioning of select semivolatile organic compounds. Although TAG was not designed to quantify the vapor phase of semivolatile organics, TAG measurements do distinguish when specific compounds are dominantly in the vapor phase, are dominantly in the particle phase, or have both phases present. Because the TAG data are both speciated and time-resolved, this distinction is sufficient to see the transition from vapor to particle phase as a function of carbon number and compound class. Laboratory studies typically measure the phase partitioning of semivolatile organic compounds by using pure compounds or simple mixtures, whereas hourly TAG phase partitioning measurements can be made in the complex mixture of thousands of polar/nonpolar and organic/inorganic compounds found in the atmosphere.

Williams, Brent J.; Goldstein, Allen H.; Kreisberg, Nathan M.; Hering, Susanne V.

2010-01-01

212

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

213

Investigation of atmospheric particle-bound reactive oxidative species (ROS): Their sources, characterization, and measurement  

NASA Astrophysics Data System (ADS)

The relationships between the observed ROS concentrations in the New York City PMTACS study and various other atmospheric indicator species such as O3, HOx radicals, organic carbon (OC), elemental carbon (EC) and secondary organic carbon (SOC), as well as the statistical significance of any observable correlations were explored. A statistically significant moderate positive correlation between the O3 and the ROS concentrations, that indicated the local intensity of photochemistry was a moderate factor affecting the formation of particulate ROS in the daytime atmosphere, was observed. The results of the comparison between ROS and HO x concentrations indicated the existence of, at best, a weak positive correlation. The lack of a more positive correlation of the particle-bound ROS, both with ozone as well as other gas phase oxidants, showed the decoupling of the particulate matter ROS from the gas phase oxidants. The comparison of ROS concentrations with OC, EC, and SOC concentrations revealed a statistically significant relationship (P-value < 0.05) only in the case of ROS and SOC. EC and OC, in general exhibited weak, negative correlations with the observed ROS concentrations. The consistency of the positive relationships between ROS and SOC for all the periods suggested that the measured ROS was photochemically driven. The absence of any statistical relevance of primary EC and OC concentrations on the ROS concentrations suggested that primary emissions, especially from motor vehicles, were not a major source of the measured particle-bound ROS. An important objective of this work was to develop a system that could provide a stable throughput of particle-bound ROS, and characterize it in terms of particle size distribution, concentrations, and formed products, such that the results obtained could be viewed in the perspective of atmospheric processes and measurements. A ROS-bearing particle generator was developed, that could deliver known exposures of ROS. It was seen that the system was generally stable with an average ROS generation capability of 5.6 nanomoles of equivalent H2O2/m3 of (aerosol+ozone) flow sampled. Additionally, the alpha-pinene-O3 oxidation chemical system, used in the ROS generator, was studied to elucidate the structures of reaction products using liquid chromatography-multiple stage mass spectrometry (LC/MSn). The classes of compounds identified based on their multiple stage-MS fragmentation patterns, mechanistic considerations of alpha-pinene-O 3 oxidation, and general fragmentation rules, of the products from this reaction system were highly oxygenated species, predominantly containing hydroperoxide and peroxide functional groups. The oxidant species observed were clearly stable for the 1-3 hrs that elapsed during aerosol collection and analysis, and probably for much longer, thus rendering it possible for these species to bind onto particles forming fine particulate organic peroxides that concentrate on the particles and could deliver concentrated doses of ROS in vivo to tissue. The lack of a suitable method to measure ROS on a routine basis has resulted in no work being undertaken to assess the effects of particle-bound ROS on health effects. In order to fill this need, an automated monitor for the sampling of ambient aerosol and the measurement of concentrations of ROS on the sampled aerosol was developed. Potential methods to quantify ROS were compared in order to arrive at a suitable method to automate. The Dichlorofluorescein (DCFH) fluorescence method was found to be the most non-specific, and hence the best suited method for the automated monitor. An integrated sampling-analysis system was designed and constructed based on collection of atmospheric particles in an aqueous slurry, and subsequent detection of the ROS concentration of the slurry using the DCFH fluorescence method. The results of the lab-scale investigation of the ROS sampling-analysis system suggested that the prototype continuous system was capable of detecting particle-bound ROS, and accounting for short-term variabilitie

Venkatachari, Prasanna

214

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.

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

2010-01-01

215

A model for the atmospheric transport of sea-salt particles in coastal areas  

NASA Astrophysics Data System (ADS)

A model for the aerosol transport in the lower atmosphere is of great interest for studies on air and water quality. One of the difficulties of such a model is to provide the accurate source terms. In particular, for maritime environment, the production of particles generated at the air-sea interface by breaking waves largely varies in time and space (Piazzola et al., 2009). More particularly, near the coastal zone, the sea-spray aerosol fluxes depend on the development of the wave field. The present paper proposes some improvement of the model MACMod, published by Tedeschi and Piazzola (2011), which is dedicated to the transport of aerosol particles in the marine atmospheric boundary layer (MABL). Taking benefit of the experimental campaign MIRAMER conducted in the French Mediterranean in 2008, a new sea-spray source function has been introduced in the latter version of the model MACMod. This consists in a revisited version of the whitecap dependant formulation established by Monahan et al. (1986). The simulations were then validated using aerosol size distributions recorded on board the ship "Atalante" for different wind speeds. Error calculations show a good performance of the model since it predicts the aerosol concentration to within a maximum factor of 3 for particle radii between 0.5 to 5 ?m.

Demoisson, A.; Tedeschi, G.; Piazzola, J.

2013-10-01

216

Monte-Carlo modelling of hot particles in Venus upper atmosphere  

NASA Astrophysics Data System (ADS)

Suprathermal oxygen atoms produced by means of photochemical reactions in planetary thermospheres can play an important role for the escape of atmospheric species by direct (i.e. thermal) or indirect (e.g. pick up) processes. In either case the non-thermal energy distribution functions at the exobase must be known in order to estimate the hot oxygen exosphere density profiles. For this purpose hot particles generated via dissociative recombination of O2+ are traced along their stochastic way through the thermosphere of Venus by using a 3D Monte-Carlo model and the kinetics and transport characteristics of these particles are determined. The simulation considers the collision of the suprathermal particles with the background gas, energy transfer, and the tracing of secondary and cascaded hot atoms, which are generated in collisions of the hot particles with ambient constituents. A non-linear electron dissociative recombination coefficient as well as energy and mass dependent collision cross sections and their corresponding scattering angles (forward scattering) are also taken into account. The exosphere density is obtained from the corresponding energy density and angular distribution at the exobase altitude by using a test particle model which traces the ballistic trajectories of hot O atoms in the exosphere.

Gröller, Hannes; Lammer, Helmut; Lichtenegger, Herbert; Shematovich, Valery; Kulikov, Yuri; Pfleger, Martin

2010-05-01

217

Dispersion of aerosol particles in the free atmosphere using ensemble forecasts  

NASA Astrophysics Data System (ADS)

The dispersion of aerosol particle pollutants is studied using 50 members of an ensemble forecast in the example of a hypothetical free atmospheric emission above Fukushima over a period of 2.5 days. Considerable differences are found among the dispersion predictions of the different ensemble members, as well as between the ensemble mean and the deterministic result at the end of the observation period. The variance is found to decrease with the particle size. The geographical area where a threshold concentration is exceeded in at least one ensemble member expands to a 5-10 times larger region than the area from the deterministic forecast, both for air column "concentration" and in the "deposition" field. We demonstrate that the root-mean-square distance of any particle from its own clones in the ensemble members can reach values on the order of one thousand kilometers. Even the centers of mass of the particle cloud of the ensemble members deviate considerably from that obtained by the deterministic forecast. All these indicate that an investigation of the dispersion of aerosol particles in the spirit of ensemble forecast contains useful hints for the improvement of risk assessment.

Haszpra, T.; Lagzi, I.; Tél, T.

2013-10-01

218

Relation between aerosol sources and meteorological parameters for inhalable atmospheric particles in Sao Paulo City, Brazil  

NASA Astrophysics Data System (ADS)

Stacked filter units were used to collect atmospheric particles in separate coarse and fine fractions at the Sao Paulo University Campus during the winter of 1989. The samples were analysed by particle-induced X-ray emission (PIXE) and the data were subjected to an absolute principal component analysis (APCA). Five sources were identified for the fine particles: industrial emissions, which accounted for 13% of the fine mass; emissions from residual oil and diesel, explaining 41%; resuspended soil dust, with 28%; and emissions of Cu and of Mg, together with 18%. For the coarse particles, four sources were identified: soil dust, accounting for 59% of the coarse mass; industrial emissions, with 19%; oil burning, with 8%; and sea salt aerosol, with 14% of the coarse mass. A data set with various meteorological parameters was also subjected to APCA, and a correlation analysis was performed between the meteorological "absolute principal component scores" (APCS) and the APCS from the fine and coarse particle data sets. The soil dust sources for the fine and coarse aerosol were highly correlated with each other and were anticorrelated with the sea breeze component. The industrial components in the fine and coarse size fractions were also highly positively correlated. Furthermore, the industrial component was related with the northeasterly wind direction and, to a lesser extent, with the sea breeze component.

Andrade, Fatima; Orsini, Celso; Maenhaut, Willy

219

Plasma processes of nuclear waste materials under atmospheric-pressure  

Microsoft Academic Search

The plasma processing requires lots of energy and should be used as a value-added process. Application of plasma process to the nuclear engineering field can be one of the best choice if process safety is assured. We have suggested several kind of application to the waste treatment processes of the nuclear materials, investigated and developed them. In this paper we

M. Suzuki; S. Mori

2003-01-01

220

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

221

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 mum 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

222

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

223

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

224

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

NASA Astrophysics Data System (ADS)

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 the satellite and TLE atmospheric radiation in many wavelength bands will be performed in two missions, Tatiana-2 and RELEC. In the TUS mission UV transient event detection will be accompanied by measurements of the weak UV emission from the “seed” electrons of extensive air showers of extremely high-primary energies.

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

2010-06-01

225

Properties of Mn-doped ZnO particles annealed in different atmospheres  

NASA Astrophysics Data System (ADS)

Mn-doped ZnO particles (x = 0.01 and 0.03) have been successfully prepared and sintered at 600 °C in air and argon atmosphere, respectively. The effects of annealing atmosphere on the structural, morphological and magnetic properties of obtained samples were studied. XRD studies reveal a wurzite-type structure for the samples with x = 0.01, while the formation of the secondary phases were evidenced for x = 0.03 samples. The samples annealed in Ar have much better crystallization. All EPR spectra present a hyperfine structure specific to isolated Mn ions and for the sample x = 0.03 annealed in air, a new resonance line arises, which could be attributed to a ferromagnetic phase.

Toloman, D.; Popa, A.; Raita, O.; Stan, M.; Silipas, T. D.; Giurgiu, L. M.

2013-11-01

226

Mass and elemental distributions of atmospheric particles nearby blast furnace and electric arc furnace operated industrial areas in Australia.  

PubMed

The improved understanding of mass and elemental distributions of industrial air particles is important due to their heterogeneous atmospheric behaviour and impact on human health and the environment. In this study, particles of different size ranges were collected from three sites in Australia located in the vicinity of iron and steelmaking industries and one urban background site with very little industrial influence. In order to determine the importance of the type of industrial activity on the urban atmospheric quality, the industrial sites selected in this study were in the close proximity to two blast furnace operated and one electric arc furnace based steelmaking sites. The chemical compositions of the collected air particles were analysed using the proton induced X-ray emission (PIXE) technique. This study revealed significantly higher metal concentrations in the atmospheric particles collected in the industrial sites, comparing to the background urban site, demonstrating local influence of the industrial activities to the air quality. The modality types of the particles were found to be variable between the mass and elements, and among elements in the urban and industrial areas indicating that the elemental modal distribution is as important as particle mass for particle pollution modelling. The highest elemental number distribution at all studied sites occurred with particle size of 0.1?m. Iron was found as the main dominant metal at the industrial atmosphere in each particle size range. The industrial Fe fraction in the submicron and ultrafine size particles was estimated at up to 95% which may be released from high temperature industrial activities with the iron and steelmaking industries being one of the major contributors. Hence, these industrial elemental loadings can highly influence the atmospheric pollution at local urban and regional levels and are required to consider in the atmospheric modelling settings. PMID:24793329

Mohiuddin, Kazi; Strezov, Vladimir; Nelson, Peter F; Stelcer, Eduard; Evans, Tim

2014-07-15

227

The simulations of sulfuric acid concentration and new particle formation in an urban atmosphere in China  

NASA Astrophysics Data System (ADS)

Simulations of sulfuric acid concentration and new particle formation are performed by using the zero-dimensional version of the model MALTE (Model to predict new Aerosol formation in the Lower TropospherE) and measurements from the Campaign of Air Quality Research in Beijing and Surrounding areas (CAREBeijing) in 2008. Chemical reactions from the Master Chemical Mechanism version 3.2 (MCM v3.2) are used in the model. High correlation (slope = 0.72, R = 0.74) between the modelled and observed sulfuric acid concentrations is found during daytime (06:00-18:00). The aerosol dynamics are simulated by the University of Helsinki Multicomponent Aerosol (UHMA) model including several nucleation mechanisms. The results indicate that the model is able to predict the on- and offset of new particle formation in an urban atmosphere in China. In addition, the number concentrations of newly formed particles in kinetic-type nucleation including homogenous homomolecular (J=K[H2SO4]2) and homogenous heteromolecular nucleation involving organic vapours (J=Khet[H2SO4][Org]) are in satisfactory agreement with the observations. However, the specific organic compounds that possibly participate in the nucleation process should be investigated in further studies. For the particle growth, only a small fraction of the oxidized total organics condense onto the particles in polluted environments. Meanwhile, the OH and O3 oxidation mechanism contribute 5.5% and 94.5% to the volume concentration of small particles, indicating the particle growth is more controlled by the precursor gases and their oxidation by O3.

Wang, Z. B.; Hu, M.; Mogensen, D.; Yue, D. L.; Zheng, J.; Zhang, R. Y.; Liu, Y.; Yuan, B.; Li, X.; Shao, M.; Zhou, L.; Wu, Z. J.; Wiedensohler, A.; Boy, M.

2013-11-01

228

Investigations of the variability of dust particle sizes in the martian atmosphere using the NASA Ames General Circulation Model  

NASA Astrophysics Data System (ADS)

We present a Mars General Circulation Model (GCM) numerical investigation of the physical processes (i.e., wind stress and dust devil dust lifting and atmospheric transport) responsible for temporal and spatial variability of suspended dust particle sizes. Measurements of spatial and temporal variations in airborne dust particles sizes in the martian atmosphere have been derived from Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) spectral and emission phase function data [Wolff, M.J., Clancy, R.T., 2003. J. Geophys. Res. (Planets) 108 (E9), doi:10.1029/2003JE002057. 1-1; Clancy, R.T., Wolff, M.J., Christensen, P.R., 2003. J. Geophys. Res. (Planets) 108 (E9), doi:10.1029/2003JE002058. 2-1]. The range of dust particle sizes simulated by the NASA Ames GCM is qualitatively consistent with TES-derived observations of effective dust particle size variability. Model results suggest that the wind stress dust lifting scheme (which produces regionally confined dust lifting) is the process responsible for the majority of the dust particle size variability in the martian atmosphere. Additionally, model results suggest that atmospheric transport processes play an important role in the evolution of atmospheric dust particles sizes during substantial dust storms on Mars. Finally, we show that including the radiative effects of a spatially variable particle size distribution significantly influences thermal and dynamical fields during the dissipation phase of the simulated global dust storm.

Kahre, Melinda A.; Hollingsworth, Jeffery L.; Haberle, Robert M.; Murphy, James R.

2008-06-01

229

Correlation of Upper-Atmospheric Be-7 With Solar Energetic Particle Events  

NASA Technical Reports Server (NTRS)

Surprisingly large concentrations of radioactive Be-7 have been found in the upper atmosphere at levels of one to three orders of magnitude greater than observed in the stratosphere. This phenomenon was originally observed on the LDEF satellite which was recovered in January 1990 following a period of extremely high solar activity in the fall of 1989. We report on follow-up measurements on the Russian COSMOS and RESURS F1 spacecraft during the period of 1996 to 1999 which was a period of minimal to moderate solar activity. The Be-7 concentrations observed on these flights were down substantially from the LDEF observations but were still one to two orders of magnitude higher than stratospheric levels. A significant correlation is observed between the Be-7 activity and the combined fluence of solar energetic protons (SEP) and galactic cosmic-ray (GCR) protons. The Be-7 activity is not correlated with overall solar activity as represented by the solar x-ray flux. We discuss possible mechanisms for the solar proton correlation. However, it is likely that the Be-7 is ionized and it is unknown how this will affect the calculations. There were several large solar flares in the fall of 1989 that produced extraordinarily intense solar particle events at the Earth and record geophysical disturbances. These may have acted to increase production of Be-7 from spallation in the stratosphere and also to enhance transport to higher altitudes from the effects of heating and expansion of the upper atmosphere. Be-7 in the upper atmosphere may also have been produced directly at the Sun. Be-7 and Li-7 are produced in solar flares when accelerated alpha-particles fuse with He-4 in the solar atmosphere. Under optimistic assumptions for Sun to Earth transport and subsequent insertion into low Earth orbit, a Be-7 density of about 10(exp -7) atom/cubic cm at 310 km is estimated.

Phillips, G. W.; Share, G. H.; August, R. A.; Tylka, A. J.; Adams, J. H., Jr.; Panasyuk, M. I.; Nymmik, R. A.; Kuzhevskjj, B. M.; Kulikauskas, V. S.; Rose, M. Franklin (Technical Monitor); Rose, M. Franklin (Technical Monitor)

2001-01-01

230

Impacts of the January 2005 solar particle events on middle atmospheric chlorine species  

NASA Astrophysics Data System (ADS)

It is well established that solar particle events (SPEs) are sources of significant chemical dis-turbances in the Earth's polar atmosphere. The observed SPE effects on nitrogen, hydrogen and oxygen compounds have been investigated in some detail in recent years, and they can be reproduced by atmospheric models using basic parametrizations for NOx and HOx produc-tion as a funtion of the particle impact ionisation. However, there are considerable differences between model predictions and measurements concerning several other trace gases including chlorine species. Two major SPEs occurred on January 17, and January 20, 2005. The latter had an exceptionally hard energy spectrum which caused maximum particle impact ionization at stratospheric altitudes. The Microwave Limb Sounder (MLS) instrument on-board the Aura satellite has measured a short-term decrease of HCl in the northern polar region corresponding to January 2005 SPEs. The peak HCl depletion is ˜300 ppt at 35-40 km. This is comparable to the depletion of messopheric HCl observed by the HALOE instrument during the July 2000 SPE. We will present simulation results of the University of Bremen Ion Chemistry (UBIC) model for the SPEs in January 2005 focusing on chlorine species. The simulations indicate that the observed short-term decrease of middle atmospheric HCl is due to a conversion into active chlorine species such as Cl, ClO and HOCl. The magnitude of the observed HCl loss can only be reproduced if reactions of negative chlorine species and the production of O(1 D) from the reaction N(2 D) + O2 are taken into account. The model results will be compared to MLS/Aura data of HCl, HOCl and ClO. Additionally, the impacts of the observed chlorine activation, e.g. on ozone, will be assessed.

Winkler, Holger; Sinnhuber, Miriam; Notholt, Justus; Maik Wissing, Jan; Kallenrode, May-Britt; Santee, Michelle

231

An improved pulse-height analyzer for energetic particle measurements in the upper atmosphere  

NASA Technical Reports Server (NTRS)

An energetic particle spectrometer for measurements in the upper atmosphere by rocket is described. The system has two methods of processing data. One is a staircase generator using threshold detectors; the other is a peak detector. The system incorporates a logarithmic converter for better resolution at low amplitudes and better use of telemetry channels. The circuits are described and calibration procedures are given. Modifications are recommended for high flux environments. Appendices cover sampling error in the peak detector and modifications made to the receiver of the propagation experiment.

Dean, L.; Smith, L. G.

1982-01-01

232

Gas\\/particle partitioning of currently used pesticides in the atmosphere of Strasbourg (France)  

Microsoft Academic Search

Atmospheric particle (P) and gas (G) phase samples have been collected in Strasbourg (Northeast of France) using a high-volume\\u000a sampler equipped with a filter-XAD-2 resin plug between April 17 and May 29, 2007. Seventy-one currently used pesticides were\\u000a monitored in these samples, and 38 of them were detected at concentrations ranging from 0.07 ng\\/m3 for fenarimol to 40.30 ng\\/m3 for deltamethrin in

Claude Schummer; Elodie Mothiron; Brice M. R. Appenzeller; Robert Wennig; Maurice Millet

2010-01-01

233

Surface composition of atmospheric aerosol: individual particle characterization by TOF-SIMS  

NASA Astrophysics Data System (ADS)

Size segregated atmospheric aerosol samples collected from the summer 2000 Montana forest fires, from Hawaiian sea salt, and from an Asian Dust event reaching Salt Lake City, Utah, in April 2001 have been studied. Multivariate statistical analysis has been used to extract information from the SIMS images. Images of the particles have been separated from the image background, which significantly improved our ability to acquire the composition of individual aerosol particles. Montana forest fire aerosol was predominantly submicrometer, well within the respirable range (PM2.5), and had a characteristic surface composition identified as the amides of stearic acid and palmitic acid. Sea salt showed a layered structure of organic compounds on the surface of aqueous NaCl. The Asian Dust event could be clearly distinguished from normal Salt Lake City particulate pollution.

Peterson, R. E.; Tyler, B. J.

2003-01-01

234

COMPASS - COMparative Particle formation in the Atmosphere using portable Simulation chamber Study techniques  

NASA Astrophysics Data System (ADS)

In this study we report the set-up of a novel twin chamber technique that uses the comparative method and establishes an appropriate connection of atmospheric and laboratory methods to broaden the tools for investigations. It is designed to study the impact of certain parameters and gases on ambient processes, such as particle formation online, and can be applied in a large variety of conditions. The characterisation of both chambers proved that both chambers operate identically, with a residence time xT (COMPASS1) = 26.5 ± 0.3 min and xT (COMPASS2) = 26.6 ± 0.4 min, at a typical flow rate of 15 L min-1 and a gas leak rate of (1.6 ± 0.8) × 10-5 s-1. Particle loss rates were found to be larger (due to the particles' stickiness to the chamber walls), with an extrapolated maximum of 1.8 × 10-3 s-1 at 1 nm, i.e. a hundredfold of the gas leak rate. This latter value is associated with sticky non-volatile gaseous compounds, too. Comparison measurement showed no significant differences. Therefore operation under atmospheric conditions is trustworthy. To indicate the applicability and the benefit of the system, a set of experiments was conducted under different conditions, i.e. urban and remote, enhanced ozone and terpenes as well as reduced sunlight. In order to do so, an ozone lamp was applied to enhance ozone in one of two chambers; the measurement chamber was protected from radiation by a first-aid cover and volatile organic compounds (VOCs) were added using a small additional flow and a temperature-controlled oven. During the elevated ozone period, ambient particle number and volume increased substantially at urban and remote conditions, but by a different intensity. Protection of solar radiation displayed a clear negative effect on particle number, while terpene addition did cause a distinct daily pattern. E.g. adding ? pinene particle number concentration rose by 13% maximum at noontime, while no significant effect was observable during darkness. Therefore, the system is a useful tool for investigating local precursors and the details of ambient particle formation at surface locations as well as potential future feedback processes.

Bonn, B.; Sun, S.; Haunold, W.; Sitals, R.; van Beesel, E.; dos Santos, L.; Nillius, B.; Jacobi, S.

2013-12-01

235

Middle atmospheric ion chemistry during energetic particle events, and impacts on the neutral chemistry  

NASA Astrophysics Data System (ADS)

It is well established that solar proton events (SPEs) are sources of distinct chemical disturbances in the Earth's polar atmosphere. While the observed SPE caused production of NOx, and the subsequent destruction of ozone can be reproduces quite well by atmospheric models using basic parametrizations for NOx and HOx release as a function of the particle impact ionisation rate, there are significant differences between measurements and model predictions concerning several other chemical compounds. For instance, during the October 2003 SPE, measurements of a number of species were obtained from the MIPAS instrument on-board the ENVISAT satellite. These measurements show significant enhancements of HNO3 and N2O5 as well as an increase of several chlorine species, i.e., ClO, HOCl and ClONO2. Atmospheric models cannot reproduce these chemical effects if only production of NOx and HOx is considered. The impact of positive and negative ion chemistry on the neutral composition of the middle atmosphere is investigated combining model results from the University of Bremen Ion Chemistry model UBIC with different neutral stratosphere-mesosphere models, particularly the new Bremen three-dimensional Chemistry and Transport model of the middle atmosphere. Focus of the investigation will be the impact of negative ion chemistry on the activation of chlorine radicals, and on the partitioning of NOy species. Model results will be compared to measurement data of different satellite instruments (HALOE, MIPAS, MLS) for several large SPEs (e.g., the July 2000, Oct/Nov 2003, and January 2005 events) to show that the observed chlorine activation and the increase of HNO3 can be reproduced much better if full negative ion chemistry is considered additionally to the NOx and HOx production.

Sinnhuber, M.; Winkler, H.; Wieters, N.; Kazeminejad, S.; Wissing, J. M.; Kallenrode, M.-B.; Stiller, G. P.; von Clarmann, T.

2009-04-01

236

Detection of Melting Temperatures and Sources of Errors Using Two-Color Pyrometry During In-flight Measurements of Atmospheric Plasma-Sprayed Particles  

NASA Astrophysics Data System (ADS)

Growing demands on the quality of plasma-sprayed coatings require reliable methods to monitor and optimize the spraying processes. As the coating microstructures are dependent on the characteristics of the powder feedstock, particle in-flight diagnostics is of great importance. In particular, the melting status of the particles is critical in this regard. Thus, the accurate determination of the particle temperature is necessary. In-flight particle temperature measurements during atmospheric plasma spraying (APS) of tungsten, molybdenum, and yttria-stabilized zirconia by two-color pyrometry were analyzed statistically. The diagnostic tool applied is the DPV-2000 (Tecnar). The particle temperature distributions allow for assessment of the melting status of the particles as well as the identification of the melting temperature and particle fractions in the molten and solidification state. Furthermore, the relevant systematic and material-dependent sources for measurement errors using two-color pyrometry were investigated. Their influence was carefully estimated and corrected. As long as there are reliable data available on the emissivity of the powder material, good agreement between the corrected measured melting temperatures and the reference data can be expected.

Mauer, Georg; Vaßen, Robert; Stöver, Detlev

2008-04-01

237

Carbohydrate-Like Composition of Submicron Atmospheric Particles and their Production from Ocean Bubble Bursting  

NASA Astrophysics Data System (ADS)

Oceans cover over two-thirds of the Earth’s surface, and the particles emitted to the atmosphere by waves breaking on sea surfaces provide an important contribution to the planetary albedo. During the ICEALOT cruise on the R/V Knorr in March and April of 2008, organic mass accounted for 15% to 47% of the submicron particle mass in the air masses sampled over the North Atlantic and Arctic Oceans. A majority of this organic component (0.1 to 0.4 ?g m-3) consisted of organic hydroxyl (including polyol and other alcohol) groups characteristic of saccharides, similar to biogenic carbohydrates found in seawater. The large fraction of organic hydroxyl groups measured during ICEALOT in submicron atmospheric aerosol exceeded those measured in most previous campaigns but were similar to particles in marine air masses in the open ocean (Southeast Pacific Ocean) and coastal sites at northern Alaska (Barrow) and northeastern North America (Appledore Island and Chebogue Point). The ocean-derived organic hydroxyl mass concentration during ICEALOT correlated strongly to submicron Na concentration and wind speed. The observed submicron particle ratios of marine organic mass to Na were enriched by factors of ~100 to ~1000 over reported sea surface organic to Na ratios, suggesting that the surface-controlled process of film bursting is influenced by the dissolved organic components present in the sea surface micro-layer. Both marine organic components and Na increased with increasing number mean diameter of the accumulation mode, suggesting a possible link between organic components in the ocean surface and aerosol-cloud interactions.

Russell, L. M.; Hawkins, L. N.; Frossard, A. A.; Quinn, P.; Bates, T. S.

2009-12-01

238

Treatment of airborne asbestos and asbestos-like microfiber particles using atmospheric microwave air plasma.  

PubMed

Atmospheric microwave air plasma was used to treat asbestos-like microfiber particles that had two types of ceramic fiber and one type of stainless fiber. The treated particles were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experiment results showed that one type of ceramic fiber (Alumina:Silica=1:1) and the stainless fiber were spheroidized, but the other type of ceramic fiber (Alumina:Silica=7:3) was not. The conversion of the fibers was investigated by calculating the equivalent diameter, the aspect ratio, and the fiber content ratio. The fiber content ratio in various conditions showed values near zero. The relationship between the normalized fiber vanishing rate and the energy needed to melt the particles completely per unit surface area of projected particles, which is defined as ?, was examined and seen to indicate that the normalized fiber vanishing rate decreased rapidly with the increase in ?. Finally, some preliminary experiments for pure asbestos were conducted, and the analysis via XRD and phase-contrast microscopy (PCM) showed the availability of the plasma treatment. PMID:21962864

Averroes, A; Sekiguchi, H; Sakamoto, K

2011-11-15

239

Spectro-microscopic Characterization of Physical Properties and Phase Separations in Individual Atmospheric Particles  

NASA Astrophysics Data System (ADS)

The phase state and liquid-liquid phase separations of ambient and laboratory generated aerosol particles were investigated using (1) scanning transmission x-ray microscopy/near-edge x-ray absorption fine structure spectroscopy (STXM/NEXAFS) coupled to a relative humidity (RH) controlled in-situ chamber and (2) environmental scanning electron microscopy (ESEM). The phase states of the particles were determined from measurements of their size and optical density. A comparison is made between the observed phase states of ambient samples and of laboratory generated aerosols to determine how well laboratory samples represent the phase of ambient samples. In addition, liquid-liquid phase separations in laboratory generated particles were investigated. Preliminary results showing that liquid-liquid phase separations occur at RH's between the deliquescence and efflorescence points and that the organic phase surrounds the inorganic phase will be presented. The STXM/NEXAFS technique provides insight into the degree of mixing at the deliquescence point and the degree of phase separation for particles of atmospherically relevant sizes.

OBrien, R. E.; Wang, B.; Neu, A.; Kelly, S. T.; Lundt, N.; Epstein, S. A.; MacMillan, A.; You, Y.; Laskin, A.; Nizkorodov, S.; Bertram, A. K.; Moffet, R.; Gilles, M.

2013-12-01

240

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.

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

241

Automated Instrumentation for the Measurement of Atmospheric Trace Gases and Particles  

NASA Astrophysics Data System (ADS)

Diffusion based separation and collection of gases, followed by filter collection of particles, is the method of choice in the present practice of atmospheric analysis. This approach is especially useful where a species is concurrently present in both phases, e.g., measurement of gaseous nitric acid in presence of particulate nitrate. Presently available techniques require batch processing, are labor intensive and difficult to automate, and exhibit poor time resolution. Continuously operating automated diffusion based gas analyzers were made for the first time by modifying a glass surface to a very highly wettable form with porous silica coating. A novel parallel plate geometry was used. It is simple to construct and offers excellent gas collection efficiency and negligible particle loss, far superior to other existing designs. Coupled to an ion chromatograph (IC), the detection limit of SO_2 for such a system was established to be less than 500 parts per quadrillion (ppq) with a time resolution of eight minutes. Corresponding values for nitrous acid and nitric acid are 110 ppq and 230 ppq, respectively. Downstream particle collection is automated by another novel approach involving vapor super saturation, vapor condensation, impaction and the thermophoretic effect. Steam is injected into the aerosol stream followed by thermoelectric cooling. The steam condenses on particles to form fine droplets. These droplets agglomerate and impact on the walls of the cooled maze-like flow path and the liquid is then collected in a simple inertial air/liquid separator. The liquid is sent to the IC for analysis. The whole system operates continuously and provides essentially quantitative particle collection (99 + % for NaNO_3, (NH_4)_2SO _4, NH_4NO _3 and H_2SO _4 particles of micrometer and submicrometer size). The system also offers excellent sensitivity (detection limits of particulate sulfate, nitrite and nitrate are 2.2 ng/m^3, 0.6 ng/m^3 , and 5.1 ng/m^3, respectively).

Poruthoor, Simon K.

242

An improved criterion for new particle formation in diverse atmospheric environments  

NASA Astrophysics Data System (ADS)

A dimensionless theory for new particle formation (NPF) was developed, using an aerosol population balance model incorporating recent developments in nucleation rates and measured particle growth rates. Based on this theoretical analysis, it was shown that a dimensionless parameter L?, characterizing the ratio of the particle scavenging loss rate to the particle growth rate, exclusively determined whether or not NPF would occur on a particular day. This parameter determines the probability that a nucleated particle will grow to a detectable size before being lost by coagulation with the pre-existing aerosol. Cluster-cluster coagulation was shown to contribute negligibly to this survival probability under conditions pertinent to the atmosphere. Data acquired during intensive measurement campaigns in Tecamac (MILAGRO), Atlanta (ANARChE), Boulder, and Hyytiälä (QUEST II, QUEST IV, and EUCAARI) were used to test the validity of L? as an NPF criterion. Measurements included aerosol size distributions down to 3 nm and gas-phase sulfuric acid concentrations. The model was applied to seventy-seven NPF events and nineteen non-events (characterized by growth of pre-existing aerosol without NPF) measured in diverse environments with broad ranges in sulfuric acid concentrations, ultrafine number concentrations, aerosol surface areas, and particle growth rates (nearly two orders of magnitude). Across this diverse data set, a nominal value of L?=0.7 was found to determine the boundary for the occurrence of NPF, with NPF occurring when L?<0.7 and being suppressed when L?>0.7. Moreover, nearly 45% of measured L? values associated with NPF fell in the relatively narrow range of 0.1

Kuang, C.; Riipinen, I.; Sihto, S.-L.; Kulmala, M.; McCormick, A. V.; McMurry, P. H.

2010-09-01

243

An improved criterion for new particle formation in diverse atmospheric environments  

NASA Astrophysics Data System (ADS)

A dimensionless theory for new particle formation (NPF) was developed, using an aerosol population balance model incorporating recent developments in nucleation rates and measured particle growth rates. Based on this theoretical analysis, it was shown that a dimensionless parameter L?, characterizing the ratio of the particle scavenging loss rate to the particle growth rate, exclusively determined whether or not NPF would occur on a particular day. This parameter determines the probability that a nucleated particle will grow to a detectable size before being lost by coagulation with the pre-existing aerosol. Cluster-cluster coagulation was shown to contribute negligibly to this survival probability under conditions pertinent to the atmosphere. Data acquired during intensive measurement campaigns in Tecamac (MILAGRO), Atlanta (ANARChE), Boulder, and Hyytiälä (QUEST II, QUEST IV, and EUCAARI) were used to test the validity of L? as an NPF criterion. Measurements included aerosol size distributions down to 3 nm and gas-phase sulfuric acid concentrations. The model was applied to seventy-seven NPF events and nineteen non-events (characterized by growth of pre-existing aerosol without NPF) measured in diverse environments with broad ranges in sulfuric acid concentrations, ultrafine number concentrations, aerosol surface areas, and particle growth rates (nearly two orders of magnitude). Across this diverse data set, a nominal value of L?=0.7 was found to determine the boundary for the occurrence of NPF, with NPF occurring when L?<0.7 and being suppressed when L?> 0.7. Moreover, nearly 45% of measured L? values associated with NPF fell in the relatively narrow range of 0.1

Kuang, C.; Riipinen, I.; Sihto, S.-L.; Kulmala, M.; McCormick, A. V.; McMurry, P. H.

2010-01-01

244

Non-silica aerogels as hypervelocity particle capture materials  

Microsoft Academic Search

The Stardust sample return mission to the comet Wild 2 used silica aerogel as the principal cometary and interstellar particle capture and return medium. However, since both cometary dust and interstellar grains are composed largely of silica, using a silica collector complicates the science that can be accomplished with these particles. The use of non-silica aerogel in future extra-terrestrial particle

Steven M. Jones

2010-01-01

245

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

246

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

Microsoft Academic Search

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

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

2004-01-01

247

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

(a) You must clean and coat each pipeline or portion of pipeline that is exposed to the atmosphere, except pipelines under paragraph (c) of this section. (b) Coating material must be suitable for the prevention of atmospheric...

2010-10-01

248

Thermal conductivity measurements of particulate materials: 3. Natural samples and mixtures of particle sizes  

Microsoft Academic Search

A line-heat source apparatus was used to measure thermal conductivities of natural fluvial and eolian particulate sediments under low pressures of a carbon dioxide atmosphere. These measurements were compared to a previous compilation of the dependence of thermal conductivity on particle size to determine a thermal conductivity-derived particle size for each sample. Actual particle-size distributions were determined via physical separation

Marsha A. Presley; Robert A. Craddock

2006-01-01

249

Evaluation of the atmospheric transport of marine-derived particles using long-chain unsaturated ketones  

SciTech Connect

Biomarker source information provided by long-chain alkenone (LCA) distribution patterns was used to assess the transport pathways of marine aerosols. The C{sub 37}-C{sub 39}LCA were found in significant amounts in aerosols collected in New Zealand. Their occurrence in the atmosphere stems from their introduction by bubble-bursting processes during wave breaking. The surface water temperatures calculated from the U{sub 37}{sup k} ratios suggested a local origin and short atmospheric residence times of the LCA. They were not detected in aerosol samples collected on American Samoa due to the absence of the source organisms in surface waters. The distribution of LCA was also investigated in size-fractionated aerosols over a range of < 0.5 to > 7.2 {mu}m equivalent diameter. Their distribution over the size spectrum demonstrated that they were only associated with large particles (d{sub eq} > 3.0 {mu}m), suggesting a direct injection of algal cells and/or their fragments into the atmosphere.

Sicre, M.A.; Gagosian, R.B.; Peltzer, E.T. (Woods Hole Oceanographic Institution, MA (United States))

1990-02-20

250

Comparison of isolation and quantification methods to measure humic-like substances (HULIS) in atmospheric particles  

NASA Astrophysics Data System (ADS)

Humic-like Substances (HULIS) comprise a significant fraction of the water-soluble organic aerosol mass and influence the cloud microphysical properties and climate effects of aerosols in the atmosphere. In this work, the most frequently used HULIS isolation and quantification methods including ENVI-18, HLB, XAD-8 and DEAE were comparatively characterized with two model standards, ten interfering compounds, and five ambient aerosol samples. Quantification of HULIS is performed with a TOC analyzer, complemented by an investigation of the chemical structure of the extracted fractions by UV-Vis spectroscopy. The results show that the four isolation methods were all characterized by high reliability, high reproducibility, and low limit of detection (LOD), indicating that each method can be used to efficiently recover Suwannee River Fulvic Acid (SRFA) and be applied to the quantification of the lower amount of HULIS in atmospheric particles. The analytical results of the UV-Vis spectra of HULIS fractions isolated also indicate that they are all favorable for extraction of compounds of high UV absorbance, high MW, and high aromaticity and that the DEAE protocol is the most significant one. Compared with the DEAE method that favors extraction of highly UV-absorbing and more aromatic compounds, SRFA isolated by the ENVI-18, HLB, and XAD-8 protocols were more representative of the global matrix. Each method has its own advantages and disadvantages and is suitable for a particular application. No single method is ideal for both isolation and quantification of HULIS in atmospheric samples.

Fan, Xingjun; Song, Jianzhong; Peng, Ping'an

2012-12-01

251

The effect of atmospheric aerosol particles and clouds on Net Ecosystem Exchange in Amazonia  

NASA Astrophysics Data System (ADS)

Carbon cycling in Amazonia 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 sun photometers. Carbon fluxes were measured using eddy-correlation techniques at LBA (The Large Scale Biosphere-Atmosphere Experiment in Amazonia) flux towers. Two sites were studied: the Biological Reserve of Jaru (located in Rondonia) and the Cuieiras Biological Reserve (located in a preserved region in central Amazonia). In the Jaru Biological Reserve, a 29% increase in carbon uptake (NEE) was observed when the AOD ranged from 0.10 to 1.5. In the Cuieiras Biological Reserve, this effect was smaller, accounting for an approximately 20% increase in NEE. High aerosol loading (AOD above 3 at 550 nm) or cloud cover leads to reductions in solar flux and strong decreases in photosynthesis up to the point where NEE approaches 0. The observed increase in NEE is attributed to an enhancement (~50%) in the diffuse fraction of photosynthetic active radiation (PAR). 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 Amazonia, the observed changes in NEE for these two sites may occur over large areas in Amazonia, significantly altering the carbon balance in the largest rainforest of the world.

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

2013-11-01

252

Characterization of Spatial Impact of Particles Emitted from a Cement Material Production Facility on Outdoor Particle Deposition in the Surrounding Community  

PubMed Central

The objective of this study was to estimate the contribution of a facility that processes steel production slag into raw material for cement production to local outdoor particle deposition in Camden, NJ. A dry deposition sampler that can house four 37-mm quartz fiber filters was developed and used for the collection of atmospheric particle deposits. Two rounds of particle collection (3–4 weeks each) were conducted in 8–11 locations 200–800 m downwind of the facility. Background samples were concurrently collected in a remote area located ~2 km upwind from the facility. In addition, duplicate surface wipe samples were collected side-by-side from each of the 13 locations within the same sampling area during the first deposition sampling period. One composite source material sample was also collected from a pile stored in the facility. Both the bulk of the source material and the <38 ?m fraction subsample were analyzed to obtain the elemental source profile. The particle deposition flux in the study area was higher (24–83 mg/m2 day) than at the background sites (13–17 mg/m2·day). The concentration of Ca, a major element in the cement source production material, was found to exponentially decrease with increasing downwind distance from the facility (P < 0.05). The ratio of Ca/Al, an indicator of Ca enrichment due to anthropogenic sources in a given sample, showed a similar trend. These observations suggest a significant contribution of the facility to the local particle deposition. The contribution of the facility to outdoor deposited particle mass was further estimated by three independent models using the measurements obtained from this study. The estimated contributions to particle deposition in the study area were 1.8–7.4% from the regression analysis of the Ca concentration in particle deposition samples against the distance from the facility, 0–11% from the U.S. Environmental Protection Agency (EPA) Chemical Mass Balance (CMB) source-receptor model, and 7.6–13% from the EPA Industrial Source Complex Short Term (ISCST3) dispersion model using the particle-size-adjusted permit-based emissions estimates.

Yu, Chang Ho; Fan, Zhihua (Tina); McCandlish, Elizabeth; Stern, Alan H.; Lioy, Paul J.

2014-01-01

253

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

254

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

NASA Astrophysics Data System (ADS)

We have investigated the behaviour of light scattering by particulates of various sizes (0.1 ?m to 100 ?m) at a small scattering angle (below 20°). It has been previously shown that, for a small angle, the scattered intensities are weakly dependent upon the particulates' composition (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 present both the classical Mie theory and its adaptation to the case of rough particulates with a fairly simple roughness parameterisation. An experimental device was built, corresponding to the angular set-up of interest (low scattering angle and therefore low angular aperture). Measurements are presented that confirm the theoretical results with good agreement. It was found that differences between the classical Mie solution and actual measurements - especially for large particulates - can be attributed to the particulate roughness. It was 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 observed for atmospheric 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. Thus it allows 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.

2014-04-01

255

[Pollution characteristics of organic acids in atmospheric particles during haze periods in autumn in Guangzhou].  

PubMed

Total suspended particles (TSP), collected during a typical haze period in Guangzhou, were analyzed for the fatty acids (C12-C30) and low molecular weight dicarboxylic acids (C3-C9) using gas chromatography/mass spectrometry (GC/MS). The results showed that the concentration of total fatty and carboxylic acids was pretty high during the haze episode. The ratios of fatty acids and carboxylic acids in haze to those in normal days were 1.9 and 2.5, respectively. During the episode of the increasing pollution, the fatty acids and carboxylic acids at night (653 ng x m(-3)) was higher than that (487 ng x m(-3)) in days. After that, the level of fatty acids and carboxylic acids in days (412 ng x m(-3)) was higher than that (336 ng x m(-3)) at night. In general, the time-series of fatty acids and carboxylic acids was similar to that of the air particle and carbonaceous species, however, the trend of the ratio of fatty acids and carboxylic acids to organic carbon was opposite to that of air particle and carbonaceous species. This ratio decreased with the increase of the concentration of air particle and after the night of 27th, the ratio increased with the decrease in the concentration of air particle. The results showed that haze pollution had a significant inhibitory effect on the enrichment of fatty and carboxylic acids. Based on the ratio of malonate to succinate (C3/C4), it could be found that primary sources contribute more to the atmospheric fatty and carboxylic acids during the autumn haze pollution periods in Guangzhou. PMID:23914557

Tan, Ji-hua; Zhao, Jing-ping; Duan, Jing-chun; Ma, Yong-liang; He, Ke-bin; Yang, Fu-mo

2013-05-01

256

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

257

Phase-field study of the second phase particle effect on texture evolution of polycrystalline material  

NASA Astrophysics Data System (ADS)

The second phase particle effect on texture evolution of polycrystalline material is studied through phase-field method. A unique field variable is introduced into the phase-field model to represent the second phase particles. Elastic interaction between particles and grains is also considered. Results indicate that in the presence of second phase particles the average particle diameter turns smaller than in the absence of these particles and retards texture formation by pinning effect. The second phase particles change the strain energy profile, which tremendously influences the pinning effect.

Lu, Yan-Li; Zhang, Liu-Chao; Zhou, Ying-Ying; Chen, Zheng

2014-06-01

258

Space Systems - Safety and Compatibility of Materials - Method to Determine the Ignition Susceptibility of Materials or Components to Particle Impact  

NASA Technical Reports Server (NTRS)

The scope of this International Technical Specification is to provide a method to determine the ignition susceptibility of materials and components to particle impact. The method can be used to determine the conditions at which ignition and consumption of a specimen material occurs when impacted by single or multiple particles entrained in a flow of gaseous oxygen (GOX). Alternatively, the method can be used to determine if a specific material or component is subject to ignition and sustained combustion in a given flow environment when impacted by single or multiple particles entrained in a flow of GOX.

Hirsch, David B.

2011-01-01

259

A numerical investigation of the destruction of peroxy radical by Cu ion catalysed reactions on atmospheric particles  

NASA Astrophysics Data System (ADS)

To determine if Cu mediated reactions on atmospheric particles are important to HO2 chemistry in the ambient atmosphere, Cu molalities were calculated from measured Cu aerosol particle concentrations, mass and number size distribution data from a site in central Sweden. A comparison of characteristic times indicates that at low relative humidities the reaction is limited by the mass transport of gas phase HO2 radical to the particle surface and not by the chemical kinetics of the aqueous reaction. Comparison of half-lives for particle reactions and the gas phase destruction of HO2 radical to form H2O2 indicate that heterogeneous reactions on aerosol particles may have important consequences on the chemistry of HO2 radical and H2O2 in the troposphere.

Ross, Howard B.; Noone, Kevin J.

1991-02-01

260

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

261

Characterization of individual atmospheric aerosol particles with SIMS and laser-SNMS  

NASA Astrophysics Data System (ADS)

The surface chemistry of atmospheric aerosol particles is important in determining how these particles will effect human health, visibility, climate and precipitation chemistry. In previous work, it has been shown that ToF-SIMS can provide significant valuable information on both organic and inorganic constituents of the aerosol. It has been found, however, that ToF-SIMS with a Ga + primary ion beam offers very low sensitivity to poly-aromatic hydrocarbons (PAHs) and heavy metals, two important classes of pollutants. In this work the utility of laser-SNMS for detection of these pollutants has been explored. Two laser systems, a 193 nm excimer laser and a 157 nm excimer laser have been utilized. Each approach has advantages. ToF-SIMS has the highest sensitivity to alkali metals and aliphatic hydrocarbons. The 193 nm laser provides very high sensitivity to lead and other metals. The 157 nm laser greatly enhances sensitivity to PAHs which has enabled detection of PAHs on the surface of individual particles.

Peterson, R. E.; Nair, A.; Dambach, S.; Arlinghaus, H. F.; Tyler, B. J.

2006-07-01

262

The simulations of sulfuric acid concentration and new particle formation in an urban atmosphere in China  

NASA Astrophysics Data System (ADS)

Simulations of sulfuric acid concentration and new particle formation are performed by using the zero-dimensional version of the model MALTE (Model to predict new Aerosol formation in the Lower TropospherE) and measurements from the Campaign of Air Quality Research in Beijing and Surrounding areas (CAREBeijing) in 2008. Chemical reactions from the Master Chemical Mechanism Version 3.2 (MCM v3.2) are used in the model. High correlation (slope = 0.72, R = 0.74) between the modelled and observed sulfuric acid concentrations is found during daytime (06:00-18:00). The aerosol dynamics are simulated by the University of Helsinki Multicomponent Aerosol (UHMA) model including several nucleation mechanisms. The results indicate that the model is able to predict the on- and offset of new particle formation in an urban atmosphere in China. In addition, the number concentrations of newly formed particles in kinetic-type nucleation including homogenous homomolecular (J=K[H2SO4]2) and homogenous heteromolecular nucleation involving organic vapours (J=Khet[H2SO4][Org]) are in satisfactory agreement with the observations. However, the specific organic compounds possibly participate in the nucleation process should be investigated in further studies.

Wang, Z. B.; Hu, M.; Mogensen, D.; Yue, D. L.; Zheng, J.; Zhang, R. Y.; Liu, Y.; Yuan, B.; Li, X.; Shao, M.; Zhou, L.; Wu, Z. J.; Wiedensohler, A.; Boy, M.

2013-06-01

263

Plasma shielding during picosecond laser sampling of solid materials by ablation in He versus Ar atmosphere  

Microsoft Academic Search

The influence of plasma shielding on the coupling of laser energy to a target surface during picosecond pulsed laser–material interactions is demonstrated using a He and Ar gas atmosphere. An inductively coupled plasma-atomic emission spectrometer (ICP-AES) is used to monitor the quantity of copper material removed during picosecond and nanosecond pulsed-laser sampling. The intensity of Cu i emission from the

X. L. Mao; W. T. Chan; M. A. Shannon; R. E. Russo

1993-01-01

264

Decomposition of persistent materials using atmospheric pressure plasmas operated in processing water  

Microsoft Academic Search

Summary form only given. Water treatment by atmospheric oxygen plasma was examined for decomposing persistent materials such as dioxin. In the previous experiments the acetic acid (CH3COOH) as an alternative to the dioxin was successfully decomposed by the combination of fast oxygen flow and a DC driven micro hollow cathode discharge (MHCD). Meanwhile no decomposition was observed with ozone injection.

K. Yasuoka; A. Yamatake; S. Ishii

2006-01-01

265

ATMOSPHERIC DRY PARTICLE DEPOSITION OF POPS AND TRACE METALS IN AN URBAN- AND INDUSTRIALLY-IMPACTED MID-ATLANTIC ESTUARY (AEOLOS B MID-ATLANTIC)  

EPA Science Inventory

Emissions of hazardous air pollutants into the coastal urban-industrial atmosphere increase atmospheric depositional fluxes to proximate water bodies. Dry deposition of large particles containing persistent organic pollutants (POPs) and trace metals were a major contribu...

266

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

267

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

268

A model for the atmospheric fate of sea salt particles incoastal areas  

NASA Astrophysics Data System (ADS)

Aerosol particles affect climate by scattering and absorbing radiation (Charlson et al., 1992), and may affect the heat budget. Among them, the particles generated at the air-sea interface by wave breaking represent a major component of the natural aerosol (Andreae, 1995). Sea-spray aerosols are mechanically produced by the interaction between wind and wave: when the wind speed increases beyond a critical value, waves break to dissipate the excess of energy. This is accompanied by the occurrence of whitecaps (Monahan and O'Muircheartaigh, 1980) and the primary marine aerosol production is directly related to the whitecap fraction. Air entrained into the water breaks up into bubbles, which may be transported to depths of several meters. When the bubbles rise and reach the surface, they burst and produce two kinds of droplets : film drops and jet drops (Blanchard, 1963; Blanchard, 1983; Resch and Afeti, 1991; Resch and Afeti, 1992). Sea-salts dominate atmospheric deposition in maritime regions (Gustafsson and Franzen, 1996; Farrell et al., 1995). However, the fate of marine aerosol particles in the marine atmosphere is still largely unknown. A model for the aerosol transport in coastal areas is then of great interest for a large number of applications among them, climate change and studies on air and water quality. Tedeschi and Piazzola (2011) presented the development of the Marine Aerosol Concentration Model (MACMod), which is a 2D unsteady model dedicated to the atmospheric transport of marine aerosols in the Marine Atmospheric Boundary Layer. However, such a transport model needs to implement an accurate source term for the sea-salt particles. Uncertainties on the sea-salt source function are still large (see Lewis and Schwartz, 2004). In particular, in coastal areas, the sea-spray production through breaking waves depends on both the fetch and the wind speed conditions. In this study, we propose to improve the MACMod model predictions by introducing an accurate sea-salt source function. To this end, the MACMOD model was implemented in the Mediterranean coast using aerosol data measured during an experimental campaign conducted in the French coastal Mediterranean area in 2008 on board the French oceanographic vessel "Atalante." Using the aerosol size distributions measured in different geographical locations south off the French coastal zone, a new source term has been introduced in MACMOD. The Monahan et al. (1986) formulation, depending both on the aerosol radius and the whitecap fraction, has been revisited. First, a separated approach is used for both the film and jet drops, accounting for the different radius modes. Then, a new sea-state dependent model is used for the whitecap fraction. The simulations were then validated with the help of aerosol size distributions recorded on board the ship "Atalante" for different meteorological conditions.

Demoisson, Ambre; Tedeschi, Gilles; Piazzola, Jacques

2013-04-01

269

Simulation of Ion Motion at Atmospheric Pressure: Particle Tracing Versus Electrokinetic Flow  

NASA Astrophysics Data System (ADS)

Results obtained with two computational approaches for the simulation of ion motion at elevated pressure are compared with experimentally derived ion current data. The computational approaches used are charged particle tracings with the software package SIMION ver. 8 and finite element based calculations using the software package Comsol Multiphysics ver. 4.0/4.0a. The experimental setup consisted of a tubular corona discharge ion source coupled to a cylindrical measurement chamber held at atmospheric pressure. Generated ions are flown into the chamber at essentially subsonic laminar isothermal conditions. In the simulations, strictly stationary conditions were assumed. The results show very good agreement between the SIMION/SDS model and experimental data. For the Comsol model, only qualitative agreement is observed.

Wissdorf, Walter; Pohler, Larissa; Klee, Sonja; Müller, David; Benter, Thorsten

2012-02-01

270

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

271

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

272

Modelling brittle impact failure of disc particles using material point method  

Microsoft Academic Search

Understanding the impact failure of particles made of brittle materials such as glasses, ceramics and rocks is an important issue for many engineering applications. During the impact, a solid particle is turned into a discrete assembly of many fragments through the development of multiple cracks. The finite element method is fundamentally ill-equipped to model this transition. Recently a so-called material

Fan Li; Jingzhe Pan; Csaba Sinka

2011-01-01

273

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

274

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

275

Atmosphere-ionosphere conductivity enhancements during a hard solar energetic particle event  

NASA Astrophysics Data System (ADS)

On 20 January 2005, a solar energetic particle (SEP) event caused the largest recorded solar proton ground level event since 1956. Serendipitously, a balloon-borne experiment intended to measure effects of relativistic electron precipitation was aloft over Antarctica (˜32 km near 70°S, 345°E geographic) throughout the duration of the SEP event, including the fast (˜6 min) onset. The balloon instrumentation included dc electric field and scalar electrical conductivity sensors. The observed conductivity increased by nearly a factor of 20 above ambient with the SEP event onset and returned to within a factor of two above normal levels within 17 h. Results from a newly developed, globally applicable atmosphere-ionosphere conductivity model based on the Sodankylä Ion and Neutral Chemistry (SIC) model suggest that proton-induced ionization was directly responsible for the observed conductivity increase at the balloon. Model input for this event included estimates of ionization from energetic particle precipitation and rigidity cutoffs. Altitudes between 20 and 150 km were considered during model runs. The results show a maximum conductivity increase near 60 km of more than 600-fold directly after SEP event onset. Relatively small conductivity enhancements (two- to fivefold) are suggested to have occurred above 70 km as a result of SEP ionization, while almost no enhancement is thought to have occurred above 95 km. These results quantify the real effect that an SEP-event can have on atmosphere-ionosphere electrical conductivity on a large, nearly global scale and provide a detailed comparison to one of the few direct stratospheric conductivity observations made during an SEP event.

Kokorowski, M.; Seppälä, A.; Sample, J. G.; Holzworth, R. H.; McCarthy, M. P.; Bering, E. A.; Turunen, E.

2012-05-01

276

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

277

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

278

Effect of colloidal particles on the formation of ordered mesoporous materials  

SciTech Connect

This research investigates the effect of colloidal particles on the preparation of ordered mesoporous materials (M41S). It demonstrates that colloidal silica and colloidal titania particles promote the formation of these materials. Under similar conditions no ordered structure is observed without the colloidal particles. A heterogeneous nucleation mechanism is proposed based on these observations and is supported by direct evidence from transmission electron microscopy (TEM). 15 refs., 5 figs.

Liu, J.; Kim, A.Y.; Virden, J.W.; Bunker, B.C. [Pacific Northwest Lab., Richland, WA (United States)

1995-03-01

279

Particle-induced damage and subsequent healing of materials: Erosion, corrosion and self-healing coatings  

Microsoft Academic Search

This review summarizes research on particle-induced damage and the subsequent repair of metallic materials. Metallic materials are damaged by solid particle impact via two damage processes: repeated plastic deformation and cutting. At a certain low-impact velocity, the particle does not skid, resulting in only plastic deformation with no damage by cutting. The critical impact velocity has been theoretically derived. Self-healing

Akihiro Yabuki

2011-01-01

280

An Overview of Particle Beam Materials Processing Techniques  

Microsoft Academic Search

Materials processing techniques can lead to the development of new products, create new applications by modifying existing materials, and add significant value to existing product lines. Additionally, there is ever-increasing consumer and regulatory pressure to develop \\

H. F. Dylla

1996-01-01

281

An Overview of Energetic Particle Precipitation Effects on the Earth's Atmosphere and (Potentially) Climate  

NASA Technical Reports Server (NTRS)

Energetic precipitating particles (EPPs) can cause significant constituent changes in the polar mesosphere and stratosphere (middle atmosphere) during certain periods. Both protons and electrons can influence the polar middle atmosphere through ionization and dissociation processes. EPPs can enhance HOx (H, OH, HO2) through the formation of positive ions followed by complex ion chemistry and NOx (N, NO, NO2) through the dissociation of molecular nitrogen. The solar EPP-created HOx increases can lead to ozone destruction in the mesosphere and upper stratosphere via several catalytic loss cycles. Such middle atmospheric HOx-caused ozone loss is rather short-lived due to the relatively short lifetime (hours) of the HOx constituents. The HOx-caused ozone depletion of greater than 30% has been observed during several large solar proton events (SPEs) in the past 50 years. HOx enhancements due to SPEs were confirmed by observations in solar cycle 23. A number of modeling studies have been undertaken over this time period that show predictions of enhanced HOx accompanied by decreased ozone due to energetic particles. The solar EPP-created NOx family has a longer lifetime than the HOx family and can also lead to catalytic ozone destruction. EPP-caused enhancements of the NOx family can affect ozone promptly, if produced in the stratosphere, or subsequently, if produced in the lower thermosphere or mesosphere and transported to the stratosphere. NOx enhancements due to auroral electrons, medium and high energy electrons, relativistic electron precipitation (REP) events, and SPEs have been measured and/or modeled for decades. Model predictions and measurements show that certain years have significant winter-time meteorological events, which result in the transport of EPP-caused NOx enhancements in the upper mesosphere and lower thermosphere to lower altitudes. The NOx-caused ozone depletion has also been observed during several solar proton events (SPEs) in the past 50 years. Model predictions indicate that the longer-lived SPE-caused polar stratospheric and mesospheric ozone decrease can be >10% for up to five months past the largest events and is statistically significant; however, total ozone measurements do not indicate any long-term SPE impact.

Jackman, Charles H.

2012-01-01

282

Particle Sizes and Composition of Mars Atmospheric Dust Based Upon Viking and Mariner 9 Observations.  

National Technical Information Service (NTIS)

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 comp...

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

1993-01-01

283

Properties of coarse particles in the atmosphere of the United Kingdom  

NASA Astrophysics Data System (ADS)

The recent rapid expansion of PM 2.5 monitoring alongside PM 10 has allowed estimation of concentrations of coarse particles (PM 2.5-10) by difference. This has been carried out for sites using comparable measurement techniques for both metrics, and the properties of the hourly average concentration data have been evaluated. In the UK atmosphere, coarse particles generally represent well under half of PM 10 mass. The ratio of PM coarse to PM 10 averages 0.29 ± 0.14 ( n = 43) for FDMS measurements and 0.38 ± 0.30 ( n = 12) for TEOM measurements and does not show a very consistent pattern according to site type. The values are mostly higher for TEOM measurements than for FDMS which is explicable in terms of semi-volatile losses predominantly from fine particles in the TEOM. Sites where PM coarse/PM 10 exceeds 0.5 generally have a marine or industrial influence. Correlations between hourly PM 2.5 and PM 10 are generally very high (mean R = 0.80 for FDMS data and mean R = 0.85 for TEOM data) whilst those between PM coarse and PM 2.5 are very much lower (mean R = 0.09 for FDMS measurements and mean R = 0.41 for TEOM measurement sites). When inter-site correlations are examined between sites of similar characteristics within 30 km of one another, the inter-site correlation of PM 2.5 ( R = 0.56-0.87) is very much higher than that of PM coarse ( R = 0.25-0.60). Coefficients of Divergence indicate lower spatial homogeneity for PM coarse than for PM 2.5. When hourly data are used to construct pollution roses, it is typical for PM 2.5 and PM 10 to show a similar pattern dominated either by long-range transport or local traffic sources while PM coarse can show quite a different pattern indicative of a different range of contributory sources. Plots of particle concentration versus wind speed show a monotonic decline of concentration with increasing wind speed for PM 2.5, but an initial decline and an increase at higher wind speeds for PM coarse. There are relatively few datasets allowing an examination of temporal trend but those available for 4.5-10 years generally show no significant trend with time for fine or coarse particles, or for PM 10. Weekday/weekend and diurnal concentration patterns for coarse and fine particles show a strong anthropogenic influence on PM coarse and a larger weekday/weekend difference for PM coarse than PM 2.5. It is concluded that coarse and fine particles show very different behaviour as a result of their different sources and properties. The lower spatial homogeneity of coarse particles may be a contributory factor in why they appear to be less toxic than fine particles in epidemiological studies.

Liu, Yan-Ju; Harrison, Roy M.

2011-06-01

284

Influence of Ionization Degrees on the Evolutions of Charged Particles in Atmospheric Plasma at Low Altitude  

NASA Astrophysics Data System (ADS)

A zero-dimensional model which includes 56 species of reactants and 427 reactions is used to study the behavior of charged particles in atmospheric plasmas with different ionization degrees at low altitude (near 0 km). The constant coefficient nonlinear equations are solved by using the Quasi-steady-state approximation method. The electron lifetimes are obtained for afterglow plasma with different initial values, and the temporal evolutions of the main charged species are presented, which are dominant in reaction processes. The results show that the electron number density decays quickly. The lifetimes of electrons are shortened by about two orders with increasing ionization degree. Electrons then attach to neutral particles and produce negative ions. When the initial electron densities are in the range of 1010 ~ 1014 cm-3, the negative ions have sufficiently high densities and long lifetimes for air purification, disinfection and sterilization. Electrons, O2-, O4-, CO4- and CO3- are the dominant negative species when the initial electron density ne0 <= 1013 cm-3, and only electrons and CO3- are left when ne0 >= 1015 cm-3 · N+2, N+4 and O+2 are dominant in the positive charges for any ionization degree. Other positive species, such as O+4, N+3, NO+, NO+2, Ar+2 and H3O+·H2O, are dominant only for a certain ionization degree and in a certain period.

Pang, Xuexia; Deng, Zechao; Jia, Pengying; Liang, Weihua; Li, Xia

2012-08-01

285

Solubility of methanol in low-temperature aqueous sulfuric acid and implications for atmospheric particle composition  

NASA Technical Reports Server (NTRS)

Using traditional Knudsen cell techniques, we find well-behaved Henry's law uptake of methanol in aqueous 45 - 70 wt% H2SO4 solutions at temperatures between 197 and 231 K. Solubility of methanol increases with decreasing temperature and increasing acidity, with an effective Henry's law coefficient ranging from 10(exp 5) - 10(exp 8) M/atm. Equilibrium uptake of methanol into sulfuric acid aerosol particles in the upper troposphere and lower stratosphere will not appreciably alter gas-phase concentrations of methanol. The observed room temperature reaction between methanol and sulfuric acid is too slow to provide a sink for gaseous methanol at the temperatures of the upper troposphere and lower stratosphere. It is also too slow to produce sufficient quantities of soluble reaction products to explain the large amount of unidentified organic material seen in particles of the upper troposphere.

Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

286

Microgel particles for the delivery of bioactive materials  

DOEpatents

Novel microgels, microparticles and related polymeric materials capable of delivering bioactive materials to cells for use as vaccines or therapeutic agents. The materials are made using a crosslinker molecule that contains a linkage cleavable under mild acidic conditions. The crosslinker molecule is exemplified by a bisacryloyl acetal crosslinker. The new materials have the common characteristic of being able to degrade by acid hydrolysis under conditions commonly found within the endosomal or lysosomal compartments of cells thereby releasing their payload within the cell. The materials can also be used for the delivery of therapeutics to the acidic regions of tumors and sites of inflammation.

Frechet, Jean M. J. (Oakland, CA); Murthy Niren (Atlanta, GA)

2010-03-23

287

Source identification of lead pollution in the atmosphere of Shanghai City by analyzing single aerosol particles (SAP)  

Microsoft Academic Search

A new method combining the pattern recognition (PR) technique with micro-PIXE spectrum was used for direct assessment of lead pollution in the atmosphere of Shanghai City. Single aerosol particles (SAP) of PMāā (<10 Ī¼m) were analyzed using the nuclear microprobe. Every particle is characterized with its micro-PICE spectrum, which can be considered its fingerprint. The PR technique was applied to

J. Wang; P. Guo; X. Li; J. Zhu; T. Reinert; J. Heitmann; D. Spemann; J. Vogt; R.-H. Flagmeyer; T. Butz

2000-01-01

288

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

289

Behavior of CCN to CN fraction during aging and mixing processes of atmospheric particles  

NASA Astrophysics Data System (ADS)

During Spring 2003, field experiments were conducted at the summit of Puy de Dóme (1465 m a.s.l.), in Central France, mainly in the free troposphere and during cloudy conditions. During this experiment, cloud condensation nuclei (CCN) concentrations were measured with a thermal gradient CCN counter at applied supersaturations that ranged between 0.2 and 2%. Aerosol size distributions were obtained with a TSI scanning mobility particle sizer (SMPS) consisting of a DMA and a CPC, and aerosol number (CN) concentrations were derived by integrating the SMPS size spectra between 0.015 and 0.3 µm. The isentropic back trajectories were computed for the altitude of the observation site using the Hybrid Single Particle Lagrangian Integrated Trajectory (HY-SPLIT) code from NOAA. For each air mass type, the aerosol bulk chemical composition used was that previously determined from cascade impactor samples by Sellegri et al. (2003). The methodological approach of this study was, firstly, to determine the relationships between CN and CCN concentrations for various air mass types arriving on the observation site. According to their origin, air masses arriving on the observation site are classified into 4 types: continental, clean marine, modified marine and polar. The CN concentrations appear to clearly depend on the type of air mass with the highest concentrations for the continental event and the lowest ones for the marine events. Moreover, a typical range can be attributed for the CCN/CN ratio to each air mass type. Then, the objective was to observe the hygroscopic behavior of aerosol particles upon heating of the sample in a thermo-desorber. Since the heated sample can be considered as representative of the original state of the aerosol, it appears that the evolution of CN to CCN is much more affected when the air mass is modified by aging and mixing processes with the contact of various atmospheric species all along the transport pathway. This result shows indirectly but clearly the presence of an active chemical layer containing more hygroscopic properties on the aerosol particle surface that can favour the particle growth. However, the role played by organic species is not clear and more work is needed to know if organic compounds may act to increase the CCN concentration.

Rojas, S.; Gomes, L.; Villani, P.

2006-09-01

290

ESCAPING PARTICLE FLUXES IN THE ATMOSPHERES OF CLOSE-IN EXOPLANETS. I. MODEL OF HYDROGEN  

SciTech Connect

A multi-fluid model for an atomic hydrogen-proton mixture in the upper atmosphere of an extrasolar planet is presented when the continuity and momentum equations of each component have already been solved with an energy equation. The particle-number density, temperature distribution, and structure of velocity can be found by using the model. I chose two special objects, HD 209458b and HD 189733b, for discussion and concluded that their predicted mass-loss rates are consistent with those observed. The most important physical process in coupling each component is the charge exchange, which couples atomic hydrogen tightly with protons. Most of the hydrogen escapes from hot Jupiters as protons, especially in the young star-planet system. I found that the single-fluid model can describe the escape of particles when the mass-loss rate is higher than a few times 10{sup 9} g s{sup -1}, while below 10{sup 9} g s{sup -1} the multi-fluid model is more suitable because of the decoupling of particles. Assuming an energy limit, I found that the predicted mass-loss rates of HD 189733b are a factor of 10 larger than those calculated by my models because of a high degree of ionization. For ionized wind, which is mainly composed of protons, assuming an energy limit is no longer effective. I fitted the mass-loss rates of the ionized wind as a function of F{sub UV} by calculating the variation of the mass-loss rates with UV fluxes.

Guo, J. H., E-mail: guojh@ynao.ac.cn [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

2011-06-01

291

Effect on surface roughness of zerodur material in atmospheric pressure plasma jet processing  

NASA Astrophysics Data System (ADS)

Zerodur material is considered as the ideal material in the high performance optic systems because of its excellent thermal stability characteristics. This paper deals with the impacting factors on the zerodur material surface roughness during atmospheric pressure plasma jet(APPJ) processing. At first, based on multiphase and multi-component in zerodur material, the effect on the zerodur surface chemical components and surface roughness is studied when the element contained Si is etched during the chemical machining process. The change of surface microcosmic topography is observed, it is proved that the technology of atmospheric pressure plasma jet can modify the surface roughness of zerodur material. Moreover, in consideration of the re-deposition phenomenon in the machining process, the composition of the re-deposition are studied and the genesis of the re-deposition were analysed. Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray spectrometry (EDX) were utilized to obtain the elemental composition of the sample powder residuum on zerodur surface. The relationship between substrate roughness and the process parameters is established based on the experimental results. Experimental results indicate that it is beneficial to add certain amount O2 to modify the surface roughness of zerodur material. This finding provides an important basis for the improvement of surface roughness in APPJ of zerodur material.

Jin, H. L.; Wang, B.; Zhang, F. H.

2010-05-01

292

Characterisation of trace metals in atmospheric particles in the vicinity of iron and steelmaking industries in Australia  

NASA Astrophysics Data System (ADS)

The aims of this work are to provide a detailed physicochemical assessment of atmospheric particles collected in the vicinity of three iron and steelmaking plants and to indicate the importance of chemical characterisation of the particles, in addition to the assessment of the particle size and concentrations. In this study, atmospheric sampling sites were selected downstream of three iron and steel processing operations in Australia and one background site in an urban area with little industrial activity. The collected particles were analysed for a range of particle size mass concentrations and detailed chemical analysis of the trace metals Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn in the corresponding particle size ranges was carried out. The PM2.5 fractions in the PM10 particles at all sampling sites ranged from 35 to 62% indicating fine particles made a significant contribution to this size fraction at these sampling sites. Similarly, PM1 to the total PM10 at all sites varied from 20 to 46% and contributed significantly to the PM10 mass loading. When compared to the background sampling site, all detected metals in the particles collected near the iron and steelmaking operations had 3.4-14 times higher concentrations of PM10, PM2.5 and PM1. Iron (Fe) was found to be the dominant metal in the particles collected in vicinity of the iron and steel processing industries contributing up to 12% of the total particle mass loading. This study suggests that the metal composition of PM10, PM2.5 and PM1 varies significantly between sites and the associated metal exposure value is considerably higher in the vicinity of iron and steel processing industries than in the urban area for the same particle concentration level.

Mohiuddin, K.; Strezov, V.; Nelson, P. F.; Stelcer, E.

2014-02-01

293

Particle size effect on the complex permeability for permalloy composite materials  

SciTech Connect

Complex permeability {mu}* = {mu}{prime}-i{mu}{double{underscore}prime} of permalloy (Fe{sub 0.55}Ni{sub 0.45}) composite materials has been studied in the frequency range from 10kHz to 2GHz for two different particle sizes of permalloys (particle diameter d < 45{micro}m and d < 6{micro}m). Low frequency permeabilities of small particle composites have larger values than those of large particle ones and natural resonance frequency of small particle composites is lower than that of large particle ones. The ac electrical resistivity in low frequency range shows a drastic increase at about 40 vol% permalloy content with decreasing permalloy content indicating the disconnection of embedded permalloy particles. These properties can be realized considering the eddy current in composite materials.

Kasagi, Teruhiro; Tsutaoka, Takanori; Hatakeyama, Kenichi

1999-09-01

294

Particle range and energy deposition in materials containing voids  

Microsoft Academic Search

The manner in which voids affect both the range and the energy deposition of energetic charged particles in irradiated metals has been investigated. Calculations of energy deposition for 5 MeV Cu ions and 1 MeV protons incident on Fe indicate uncertainties in these quantities that increase with penetration distance. Mass density corrections adequately account for the presence of voids, except

G. R. Odette; D. M. Schwartz; A. J. Ardell

1974-01-01

295

MATERIALS ANALYSIS IN ARCHAEOMETRICAL STUDIES AT BUCHAREST PARTICLE ACCELERATORS  

Microsoft Academic Search

The analysis of archaeological objects requires simultaneously, non-destructive, fast, versatile, sensitive and multielemental methods. Our purpose was to help Romanian archaeologists to identify objects provenance (workshops, technologies, mines) and to explain commercial, military and political aspects. Ancient Greek silver and Dacian gold coins were studied. For silver coins, two methods were used : in air 3 MeV protons PIXE (Particle

B. Constantinescu; V. Cojocaru; R. Bugoi; A. Sasianu

296

Insitu measurements of laser-induced-fluorescence spectra of single atmospheric organic carbon aerosol particles for their partial classification. (Invited)  

NASA Astrophysics Data System (ADS)

Aerosols are ubiquitous in the earth’s atmosphere. Within the last two decades, the importance of organic carbon aerosols (OCAs) has been widely recognized. OCAs have both natural and anthropogenic sources and have effects ranging from atmospheric radiative forcing to human health. Improved methods for measuring and classifying OCAs are needed for better understanding their sources, transformation, and fate. In this talk we focus on the use of a relatively new technique for characterization of single OCA particles in atmospheric aerosol: ultraviolet laser-induced-fluorescence (UV-LIF). UV-LIF spectra of atmospheric aerosols measured at multiple sites with different regional climate (Adelphi, MD, New Haven, CT, and Las Cruces, NM) are reported. A hierarchical clustering method was used to cluster (approximately 90%) of the single-particle UV-LIF spectra into 8-10 groups (clusters). Some of these clusters have spectra that are similar to spectra of some important classes of atmospheric aerosol, such as humic/fulvic acids and humic-like substances, bacteria, cellulose, marine aerosol, and polycyclic aromatic hydrocarbons. The most highly populated clusters, and some of the less populated ones, appear at all sites. On average, spectra characteristic of humic/fulvic acids and humic-like-substances (HULIS) comprise 28-43% of fluorescent particles at all three sites; whereas cellulose-like spectra contribute only 1-3%.

Pinnick, R. G.; Pan, Y.; Hill, S.; Rosen, J. M.; Chang, R. K.

2009-12-01

297

Energetic Particles Impacting the Upper Atmosphere in Connection with Transient Luminous Event Phenomena: 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

M. I. Panasyuk; V. V. Bogomolov; G. K. Garipov; O. R. Grigoryan; Yu. I. Denisov; B. A. Khrenov; P. A. Klimov; L. L. Lazutin; S. I. Svertilov; N. N. Vedenkin; I. V. Yashin; S. I. Klimov; V. S. Makhmutov; Yu. 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

2009-01-01

298

Computed contributions to odd nitrogen concentrations in the Earth’s polar middle atmosphere by energetic charged particles  

Microsoft Academic Search

A two-dimensional photochemical transport model which has inputs that characterize the odd nitrogen production associated with galactic cosmic rays, solar particle events (SPEs), and lower thermospheric contributions (auroral electrons and solar EUV and soft X-rays) is used to compute odd nitrogen concentrations in the polar middle atmosphere from 1 January 1970 to 31 December 1994. We are able to separate

Francis M. Vitt; Thomas P. Armstrong; Thomas E. Cravens; Gisela A. M. Dreschhoff; Charles H. Jackman; Claude M. Laird

2000-01-01

299

Absorption of Beta Particles in Different Materials: An Undergraduate Experiment  

ERIC Educational Resources Information Center

The absorption of beta rays from a radioactive source in different materials was investigated by the use of a simple setup based on a Geiger counter and a set of absorber sheets. The number of electrons traversing the material was measured as a function of its thickness. Detailed GEANT simulations were carried out to reproduce the obtained…

La Rocca, Paola; Riggi, Francesco

2009-01-01

300

A review of solid particle erosion of engineering materials  

Microsoft Academic Search

A detailed modeling effort was initiated to develop an analytical capability to predict corrosion\\/erosion behavior of structural materials in advanced fossil technologies. As part of this program, a literature search was conducted to collect the available erosion data on materials of interest in fossil energy technology and to evaluate the capability of the existing erosion models to correlate the data.

S. Majumdar; K. Natesan; A. Sarajedini

1987-01-01

301

A review of solid particle erosion of engineering materials  

Microsoft Academic Search

A detailed modelling effort is currently under way to develop an analytical capability to predict corrosion\\/erosion behavior of structural materials in advanced fossil technologies. As part of this program, a literature search was conducted to collect the available erosion data on materials of interest in fossil technology and to evaluate the capability of the existing erosion models to correlate the

S. Majumdar; A. Sarajedini

1987-01-01

302

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

303

Solid spherical glass particle impingement studies of plastic materials  

NASA Technical Reports Server (NTRS)

Erosion experiments on polymethyl methacrylate (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE) were conducted with spherical glass beads impacting at normal incidence. Optical and scanning electron microscopic studies and surface profile measurements were made on specimens at predetermined test intervals. During the initial stage of damage to PMMA and polycarbonate, material expands or builds up above the original surface. However, this buildup disappears as testing progresses. Little or no buildup was observed on PTFE. PTFE is observed to be the most resistant material to erosion and PMMA the least. At low impact pressures, material removal mechanisms are believed to be similar to those for metallic materials. However, at higher pressures, surface melting is indicated at the center of impact. Deformation and fatigue appear to play major roles in the material removal process with possible melting or softening.

Rao, P. V.; Young, S. G.; Buckley, D. H.

1983-01-01

304

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

305

Relationships between horizontal transport flux and vertical deposition flux during dry deposition of atmospheric dust particles  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments were conducted to investigate the relationships between vertically settling dust and the horizontal dust flow from which the particles originate. The study primarily focused on the grain size characteristics and on the horizontal and vertical sediment fluxes. Simultaneous samplings of vertical deposition flux and horizontal transport flux were carried out at an almost identical altimetric level (a very narrow layer immediately above a water surface generating no resuspension). This made it possible to relate deposition flux to the horizontal transport flux and to study how deposition alters the sedimentological characteristics of horizontally moving dust. The use of water as a deposition surface implied that the dust was subjected to some degree of dispersion after the settling. This restricted the analysis to grains >10 ?m, but the trends for grains <10 ?m were easy to reconstruct. The experiments show that deposited dust is generally coarser than the parent dust from which it originates but only for friction velocities below 0.34 m s-1. For higher wind speeds the median grain diameter of settling dust does not differ from that of the parent dust. Similar observations were made for the horizontal and vertical dust fluxes. At a constant horizontal transport flux (Fh) vertical deposition flux (Fs) drops with wind speed; however, from the same critical friction velocity of 0.34 m s-1 the ratio Fs/Fh remains constant. It was also found that the relationships between Fh and Fs depend on the grain size of the particles but only for sufficiently fine particles. Particles >50 ?m no longer affect these relationships. Vertical mixing created by the turbulent nature of the flow strongly affects deposition of atmospheric dust. Mixing significantly hampers deposition of the grains, especially the small ones. The wind tunnel experiments allowed the magnitude of the effect mixing exerts on deposition to be calculated. For coarse grains the effect is small, but for fine grains mixing may hamper deposition by several dozen per cent. Theoretical dust deposition models should thus consider vertical mixing or otherwise include it in the numerical value of the velocity of deposition vd.

Goossens, Dirk

2008-06-01

306

Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition  

NASA Astrophysics Data System (ADS)

Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous component of Hg(II)), particle-bound mercury (PBM, the particulate component of Hg(II)), fine particulate matter (PM2.5), and temperature (T) at five sites in North America to derive an empirical gas-particle partitioning relationship log10(K-1) = (10±1)-(2500±300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in ?g m-3, and T in K. This relationship is within the range of previous work but is based on far more extensive data from multiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) between the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with little aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more efficient scavenging of particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North American surface sites suggests that subsidence from the free troposphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduction of Hg(II) emitted from coal combustion and by assuming that anthropogenic particulate Hg(p) behaves as semi-volatile Hg(II) rather than as a refractory particulate component. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout algorithm. The observed wintertime minimum in wet deposition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).

Amos, H. M.; Jacob, D. J.; Holmes, C. D.; Fisher, J. A.; Wang, Q.; Yantosca, R. M.; Corbitt, E. S.; Galarneau, E.; Rutter, A. P.; Gustin, M. S.; Steffen, A.; Schauer, J. J.; Graydon, J. A.; St. Louis, V. L.; Talbot, R. W.; Edgerton, E. S.; Zhang, Y.; Sunderland, E. M.

2012-01-01

307

Functionalised carboxylic acids in atmospheric particles: An annual cycle revealing seasonal trends and possible sources  

NASA Astrophysics Data System (ADS)

Carboxylic acids represent a major fraction of the water soluble organic carbon (WSOC) in atmospheric particles. Among the particle phase carboxylic acids, straight-chain monocarboxylic acids (MCA) and dicarboxylic acids (DCA) with 2-10 carbon atoms have extensively been studied in the past. However, only a few studies exist dealing with functionalised carboxylic acids, i.e. having additional hydroxyl-, oxo- or nitro-groups. Regarding atmospheric chemistry, these functionalised carboxylic acids are of particular interest as they are supposed to be formed during atmospheric oxidation processes, e.g. through radical reactions. Therefore they can provide insights into the tropospheric multiphase chemistry. During this work 28 carboxylic acids (4 functionalised aliphatic MCAs, 5 aromatic MCAs, 3 nitroaromatic MCAs, 6 aliphatic DCAs, 6 functionalised aliphatic DCAs, 4 aromatic DCAs) were quantitatively determined in 256 filter samples taken at the rural research station Melpitz (Saxony, Germany) with a PM10 Digitel DHA-80 filter sampler. All samples were taken in 2010 covering a whole annual cycle. The resulting dataset was examined for a possible seasonal dependency of the acid concentrations. Furthermore the influence of the air mass origin on the acid concentrations was studied based on a simple two-sector classification (western or eastern sector) using a back trajectory analysis. Regarding the annual average, adipic acid was found to be the most abundant compound with a mean concentration of 7.8 ng m-3 followed by 4-oxopimelic acid with 6.1 ng m-3. The sum of all acid concentrations showed two maxima during the seasonal cycle; one in summer and one in winter, whereas the highest overall acid concentrations were found in summer. In general the target acids could be divided into two different groups, where one group has its maximum concentration in summer and the other group during winter. The first group contains all investigated aliphatic mono- and dicarboxylic acids. The high concentrations in summer could lead to the conclusion that these acids are mostly formed during photochemical processes in the atmosphere. However, the concentrations in autumn were often exceeded by the ones in winter. Therefore probably other sources beside photochemical processes have to be considered. The second group consists of aromatic compounds. Because of the high concentrations in winter it can be concluded that photochemical formation plays a minor role and primary emission sources e.g., wood combustion are likely. Further evidence in determining sources of the carboxylic acids could be obtained from the air mass origin. In general, air masses transported from East have a more anthropogenic influence than the air mass inflow from West. For all aromatic carboxylic acids higher concentrations were determined during eastern inflow, indicating anthropogenic sources. This presumption is supported by high correlations with the elemental carbon (EC). Regarding the aliphatic carboxylic there is one group with higher concentrations when the air mass is transported from West and one with higher concentrations when air mass is transported from East. In summary the findings of this study reveal a clear difference in the seasonal trends of the single target acids indicating a variety of different sources.

Teich, Monique; van Pinxteren, Dominik; Herrmann, Hartmut

2013-04-01

308

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

309

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

310

Aerosol trace metals, particle morphology and total gaseous mercury in the atmosphere of Oxford, UK  

NASA Astrophysics Data System (ADS)

An investigation of atmospheric trace metals was conducted in Oxford, UK, a small city ˜60 miles northwest of London, in 2007 and 2008. Concentrations of Sr, Mo, Cd, Pb, V, Cr, Mn, Fe, Co, Ni, Cu and Zn in aerosol were measured in bulk and size segregated samples. In addition, total gaseous mercury (TGM) concentrations were monitored semi-continuously by cold vapour-atomic fluorescence spectroscopy. Metal concentrations in Oxford were intermediate between previously reported levels of UK rural and urban areas for most metals studied and levels of Cd, Ni and Pb were within European guidelines. Metal concentrations appeared to be influenced by higher traffic volume on a timescale of hours. The influence of traffic on the aerosols was also suggested by the observation of carbonaceous particles via scanning electron microscopy (SEM). Air mass back trajectories suggest air masses arriving in Oxford from London and mainland Europe contained the highest metal concentrations. Aerosol samples collected over Bonfire Weekend, a period of intense firework use and lighting of bonfires in the UK, showed metal concentrations 6-46 times higher than at other times. Strontium, a tracer of firework release, was present at higher concentrations and showed a change in its size distribution from the coarse to fine mode over Bonfire Weekend. The presence of an abundance of spherical Sr particles was also confirmed in SEM images. The average TGM concentration in Oxford was 3.17 ng m -3 (st. dev. 1.59) with values recorded between 1.32 and 23.2 ng m -3. This is a higher average value than reported from nearby rural locations, although during periods when air was arriving from the west, similar concentrations to these rural areas were seen in Oxford. Comparison to meteorological data suggests that TGM in Oxford's air is highest when wind is arriving from the east/southeast. This may be due to emissions from London/mainland Europe with a possible contribution from emissions from a local crematorium situated 4 miles east of the sampling site. A diurnal pattern was also observed in the TGM data with a minimum concentration during the day when mercury may have been diluted by thermal mixing of the atmospheric boundary layer. Additionally, this diurnal pattern may reflect variations in a local source of TGM.

Witt, M. L. I.; Meheran, N.; Mather, T. A.; de Hoog, J. C. M.; Pyle, D. M.

2010-04-01

311

Biogenic particles in the surface microlayer and overlaying atmosphere in the central Arctic Ocean during summer  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy photographs of airborne particles are compared with those of particles found in the surface microlayer of the open water between ice floes in the central Arctic Ocean in summer. The similarity in morphology, physical properties, X-ray spectra and a chemical reaction of the numerous aggregates and their building blocks predominantly smaller than 70 nm diameter, and of bacteria and other micro-organisms found in both, strongly suggests that the airborne particles were ejected from the water by bursting bubbles. The shape of the size distribution of aggregates in the air is very similar to that in the water, each with a well-defined Aitken mode but shifted towards smaller sizes. Diffuse electron-transparent material joining and surrounding the heat resistant and non-hygroscopic particulates in both the air and water is shown to have properties consistent with the exopolymer secretions (EPS) of microalgae and bacteria in the water. EPS are highly surface-active, highly hydrated molecules that can spontaneously assemble into gels. They are broken down by ultraviolet light or acidification. These properties provide an explanation for the different resistance to dehydration of bacteria from air and water samples when subjected to a vacuum, and the apparent absence of sea salt on airborne bacteria and aggregates. The difference in size distribution between the air and water samples is also explained. The role of EPS and particulate matter from the open lead surface microlayer in the production of the airborne Aitken mode particles and cloud condensation nuclei is examined and concluded to be very important.

Leck, Caroline; Bigg, E. Keith

2005-09-01

312

Phonon-mediated particle detection with superconducting detector materials  

NASA Astrophysics Data System (ADS)

It is shown that a calorimeter composed of a cylindrical-shape absorber of superconducting V metal, with 25 x 10 mm dimensions and weighing 15 g, is sensitive to thermal phonons that have been generated by the stopping and the absorption of a 5 MeV alpha-particle. A further improvement in energy resolution is expected via lowering of calorimeter operating temperature from 120 mK to 10-50 mK.

Azgui, F.; von Feilitzsch, F.; Forster, G.

1992-10-01

313

Dynamics of Granular Materials and Particle-Laden Flows  

SciTech Connect

Rapid granular flows and particle-laden flows were studied in laboratory experiments, molecular dynamics simulations, and simulations of continuum equations. The research demonstrated that the inclusion of friction is crucial in realistic modeling of granular flows; hence extensive previous analyses and simulations by many researchers for frictionless particles must be reconsidered in the light of our work. We also made the first detailed comparison between experiment and the predictions of continuum theory for granular media (hydrodynamic equations). We found that shock waves easily form in granular flows since the speed of sound waves (pressure fluctuations) in a granular gas is small, typically 10 cm, while flow velocities are easily an order of magnitude larger. Our measurements on vertically oscillating granular layers led to the development of a novel technique for continuously separating particles of different sizes. Our study of craters formed by the impact of a projectile in a granular medium showed, surprisingly, that the time taken for a projectile to come to a rest in the granular layer is independent of the projectile’s impact energy. Another study supported by this grant examined a vertically oscillating layer of a mixture of cornstarch and water. The discovery of stable holes in the mixture was reported widely in the popular press, e.g., Science News [15 May 2004], “Imaging poking a liquid to create holes that persist like the holes in Swiss cheese. Incredible as that might sound, a group of scientists has done it.” Further experiments on glass spheres in an aqueous solution yielded the same holey fluid phenomenon, supporting our conjecture that such holes may occur in dense concentrations of particles in solution in industrial applications.

Swinney, Harry L.

2007-07-11

314

The Ultrafine Mineralogy of a Molten Interplanetary Dust Particle as an Example of the Quench Regime of Atmospheric Entry Heating  

NASA Technical Reports Server (NTRS)

Melting and degassing of interplanetary dust particle L2005B22 at approx. 1200 C was due to flash heating during atmospheric entry. Preservation of the porous particle texture supports rapid quenching from the peak heating temperature whereby olivine and pyroxene nanocrystals (3 nm-26 nm) show partial devitrification of the quenched melt at T approx. = 450 C - 740 C. The implied ultrahigh cooling rates are calculated at approx. 105 C/h-106 C/h, which is consistent with quench rates inferred from the temperature-time profiles based on atmospheric entry heating models. A vesicular rim on a nonstoichiometric relic forsterite grain in this particle represents either evaporative magnesium loss during flash heating or thermally annealed ion implantation texture.

Rietmeijer, Frans J. M.

1996-01-01

315

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.

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

2011-01-01

316

Adsorption and reactions of atmospheric constituents and pollutants on ice particles: an FTIR study  

NASA Astrophysics Data System (ADS)

Processes on icy particles attract much attention due to their importance for atmospheric science, ecology and astrophysics. In this work, adsorption and ecologically important reactions of some molecules on pure and mixed water icy films by means of FTIR spectroscopy have been investigated. The cell for spectral studies of adsorbed molecules at variable temperatures (55-370 K), described elsewhere1, enables one to run the spectra in the presence of gaseous adsorbate, and even to perform adsorption from the solution in some cryogenic solvents. For the studies of ice films, it was equipped with a device for water vapour sputtering from the heated capillaries and deposition onto the inner BaF2 or ZnSe windows of the cell, cooled by liquid nitrogen. Lower temperatures were obtained by pumping off evaporating nitrogen from the coolant volume. The estimated specific surface area of freshly deposited at 77 K water ice film was about 160 m2/g and decreases on raising the temperature together with the diminishing intensity of the bands of dangling OH (OD) groups at 3696 (2727) cm-1 until the latter disappear at 130 - 160 K when the changes of bulk absorption provide evidence for a phase transition from amorphous to polycrystalline ice. CO adsorption at 77 K results in two bands at 2153 and 2137 cm-1 assigned to molecules forming weak H-bond with the dangling hydroxyl groups and bound to unsaturated surface oxygen atoms, respectively2. The band of dangling hydroxyl groups moves to lower wavenumbers on adsorption of different molecules (hydrogen, nitrogen, methane, ozone, NO, ethane or chlorinated ethenes, etc.). The shift value depends on the nature of adsorbate. Besides this shift, spectra of adsorbed nitrogen and methane registered at 55 K reveal the adsorption intensity decrease at ~ 2650 cm-1 at the high-frequency slope of bulk adsorption, and increase at about 25 cm-1 below. We interpret this perturbation as a strengthening of H-bonds between surface water molecules, which act as adsorption sites either as a proton-donor or as a donor of the lone pair of electrons. Such adsorption-induced relaxation explains the dependence of physico-chemical properties of icy particles on the presence of atmospheric gases. Spectra HCN/D2O and ND3/D2O mixed icy films with low (1:10) dopant/water ratios do not manifest any changes in the acidic or basic properties of dangling hydroxyl groups or surface oxygen atoms, but reveal a difference in the proportion between the concentrations of these sites as compared with that for pure water ice. For high dopant concentrations (1:1), the dangling hydroxyls were not observed; the dominant adsorption sites for CO are likely to be the unsaturated oxygen atoms, while serious structural changes occur in the bulk of ices. Ecologically important reactions of atmospheric pollutants such as ozonolysis of ethene, chlorinated ethenes, hydrogen cyanide, and methyl bromide adsorbed on water ice film as well as the influence of UV radiation on this process have been studied in 77 - 200 K temperature range by FTIR spectroscopy. Ozone co-adsorption with ethene or C2H3Cl readily leads to ozonolysis reaction, which also starts for C2H2Cl2 isomers but only at temperatures elevated up to 120 - 150 K. Co-adsorption of O3 with HCN or CH3Br molecules in the dark does not lead to any noticeable spectral changes. Irradiation of HCN or CH3Br deposited on ice films in the presence of ozone leads to appearance of new bands revealing the formation of ozonolysis products. The same "synergetic effect" of simultaneous action of ozone and UV radiation at 77 K, was found for C2H2Cl2 isomers and C2Cl4, which are resistant against O3 even at higher temperatures. The obtained spectral dependence of photo-ozonolysis of C2Cl4 and HCN at 77 K shows that photoexcitation or photodissociation of ozone, evidently, accounts for the observed processes. The surface of ice particles, thus, plays the role of a condenser of atmospheric pollutants and acts as a micro- photoreactor in the atmospheric chemistry. Acknowledgments. The work was

Rudakova, A. V.; Marinov, I. L.; Poretskiy, M. S.; Tsyganenko, A. A.

2009-04-01

317

Organophosphate and halogenated flame retardants in atmospheric particles from a European arctic site.  

PubMed

Levels of 13 organophosphate esters (OPEs) and 45 brominated and chlorinated flame retardants (BFRs) were measured in particle phase atmospheric samples collected at Longyearbyen on Svalbard in the European Arctic from September 2012 to May 2013. Total OPE (?OPEs) concentrations ranged from 33 to 1450 pg/m(3), with the mean ?OPE concentration of 430 ± 57 pg/m(3). The nonchlorinated tri-n-butyl phosphate (TnBP) and 2-ethylhexyl-diphenyl phosphate (EHDPP) were the most abundant OPE congeners measured, and the sum of all nonchlorinated OPE concentrations comprised ?75% of the ?OPE concentrations. The most abundant chlorinated OPE was tris(1-chloro-2-propyl) phosphate (TCPP). Total BFR concentrations (?BFRs) were in the range of 3-77 pg/m(3), with a mean concentration of 15 ± 3 pg/m(3). 2-Ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB) and bis(2-ethylhexyl)tetrabromophthalate (TBPH) were among the relatively abundant BFRs measured in these samples and comprised ?46% and 17% of ?BFR concentrations, respectively. Total PBDE (?PBDE) concentrations constituted ?37% of ?BFR concentrations on average and ranged from 1 to 31 pg/m(3). The most abundant PBDE congener was BDE-209, which contributed 24% to ?PBDE concentrations. Dechlorane Plus (DP) was detected in all of the samples, and ?DP concentrations (syn- + anti-DP concentrations) ranged from 0.05 to 5 pg/m(3). Overall, ?OPE concentrations were 1-2 orders of magnitude higher than the ?BFR concentrations. PMID:24848787

Salamova, Amina; Hermanson, Mark H; Hites, Ronald A

2014-06-01

318

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

319

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

PubMed Central

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.

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

2011-01-01

320

Atmospheric ultrafine particles promote vascular calcification via the NF-?B signaling pathway.  

PubMed

Exposure to atmospheric fine particulate matter (PM(2.5)) is a modifiable risk factor of cardiovascular disease. Ultrafine particles (UFP, diameter <0.1 ?m), a subfraction of PM(2.5), promote vascular oxidative stress and inflammatory responses. Epidemiologic studies suggest that PM exposure promotes vascular calcification. Here, we assessed whether UFP exposure promotes vascular calcification via NF-?B signaling. UFP exposure at 50 ?g/ml increased alkaline phosphatase (ALP) activity by 4.4 ± 0.2-fold on day 3 (n = 3, P < 0.001) and matrix calcification by 3.5 ± 1.7-fold on day 10 (n = 4, P < 0.05) in calcifying vascular cells (CVC), a subpopulation of vascular smooth muscle cells with osteoblastic potential. Treatment of CVC with conditioned media derived from UFP-treated macrophages (UFP-CM) also led to an increase in ALP activities and matrix calcification. Furthermore, both UFP and UFP-CM significantly increased NF-?B activity, and cotreatment with an NF-?B inhibitor, JSH23, attenuated both UFP- and UFP-CM-induced ALP activity and calcification. When low-density lipoprotein receptor-null mice were exposed to UFP at 359.5 ?g/m(3) for 10 wk, NF-?B activation and vascular calcification were detected in the regions of aortic roots compared with control filtered air-exposed mice. These findings suggest that UFP promotes vascular calcification via activating NF-?B signaling. PMID:23242187

Li, Rongsong; Mittelstein, David; Kam, Winnie; Pakbin, Payam; Du, Yunfeng; Tintut, Yin; Navab, Mohamad; Sioutas, Constantinos; Hsiai, Tzung

2013-02-15

321

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

322

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

Microsoft Academic Search

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

Bernard P. Binks; Ryo Murakami

2006-01-01

323

Sieveless particle size distribution analysis of particulate materials through computer vision  

Microsoft Academic Search

This paper explores the inconsistency of “length-based separation” by mechanical sieving of particulate materials with standard sieves, which is the standard method of particle size distribution (PSD) analysis. We observed inconsistencies of length-based separation of particles using standard sieves with manual measurements, which showed deviations of 17–22 times. In addition, we have demonstrated the “falling through” effect of particles cannot

C. Igathinathane; L. O. Pordesimo; Eugene P Columbus; William D Batchelor; Shahabaddine Sokhansanj

2009-01-01

324

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

325

TCT characterization of different semiconductor materials for particle detection  

NASA Astrophysics Data System (ADS)

The development of digital semiconductor based X-ray detectors necessitates a detailed understanding of the applied sensor material. Under this premise a broad-band transient current technique (TCT) setup has been developed and used to characterize different semiconductors. The measurements are based on the generation of electrical charges within the sensor material and the subsequent time-resolved analysis of the charge carrier movement. From the recorded current pulses the charge collection efficiency, the charge carrier mobility and the electric field profile have been extracted. The examined materials are silicon p in n diodes, ohmic and Schottky contacted CdTe detectors, CdZnTe (CZT) crystals with Schottky contacts as well as two single-crystal CVD-diamonds.

Fink, J.; Lodomez, P.; Krüger, H.; Pernegger, H.; Weilhammer, P.; Wermes, N.

2006-09-01

326

Report on the Possible Benefits of Using High-Temperature Superconductor Materials in Particle Accelerator Design.  

National Technical Information Service (NTIS)

This report discusses different design concepts for particle beam accelerators. It demonstrates that with the use of high temperature superconducting materials, a more compact, lighter, and more robust accelerator design can be realized for the space base...

B. Balko L. Cohen R. Collins

1988-01-01

327

Role of ceramic particles for developing wear resistant materials  

NASA Astrophysics Data System (ADS)

The present work emphasises on the study of two different ceramic particulates embedded in the soft alloy. The material is developed by spray atomization. The two ceramic particulates used for the study are SiC and ZrSiO4. The effect of particulate on hardness has been analyzed. Moreover, wear characteristics of the both developed material has been compared with the monolithic as cast alloy. The results of the ZrSiO4 reinforced composite shows lesser wear rate at 50°C and 150°C at low as well as high loads as compared to SiC reinforced Al-alloy.

Kaur, Kamalpreet; Pandey, O. P.

2013-06-01

328

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

329

Wave propagation in functionally graded materials by modified smoothed particle hydrodynamics (MSPH) method  

Microsoft Academic Search

We use the modified smoothed particle hydrodynamics (MSPH) method to study the propagation of elastic waves in functionally graded materials. An artificial viscosity is added to the hydrostatic pressure to control oscillations in the shock wave. Computed results agree well with the analytical solution of the problem. It is shown that, for the same placement of particles\\/nodes the MSPH method

G. M. Zhang; R. C. Batra

2007-01-01

330

Dynamic stress concentrations in particle- and fiber-reinforced composite materials  

NASA Astrophysics Data System (ADS)

The scattering of elastic waves from spherical elastic particles and cylindrical elastic fibers embedded in solid binders is studied. General analytic expressions are obtained for the corresponding dynamic stress concentrations in particle- and fiber-reinforced composite materials. Special cases of the results are found to be equivalent to independently derived formulas for elastic wave scattering from rigid, fluid, and void spheres and cylinders.

Hinders, M.; Fang, T.; Bronson, S.; Bogan, S.; Nagem, R.; Sandri, G.

331

Photons and particles emitted from cold atmospheric-pressure plasma inactivate bacteria and biomolecules independently and synergistically.  

PubMed

Cold atmospheric-pressure plasmas are currently in use in medicine as surgical tools and are being evaluated for new applications, including wound treatment and cosmetic care. The disinfecting properties of plasmas are of particular interest, given the threat of antibiotic resistance to modern medicine. Plasma effluents comprise (V)UV photons and various reactive particles, such as accelerated ions and radicals, that modify biomolecules; however, a full understanding of the molecular mechanisms that underlie plasma-based disinfection has been lacking. Here, we investigate the antibacterial mechanisms of plasma, including the separate, additive and synergistic effects of plasma-generated (V)UV photons and particles at the cellular and molecular levels. Using scanning electron microscopy, we show that plasma-emitted particles cause physical damage to the cell envelope, whereas UV radiation does not. The lethal effects of the plasma effluent exceed the zone of physical damage. We demonstrate that both plasma-generated particles and (V)UV photons modify DNA nucleobases. The particles also induce breaks in the DNA backbone. The plasma effluent, and particularly the plasma-generated particles, also rapidly inactivate proteins in the cellular milieu. Thus, in addition to physical damage to the cellular envelope, modifications to DNA and proteins contribute to the bactericidal properties of cold atmospheric-pressure plasma. PMID:24068175

Lackmann, Jan-Wilm; Schneider, Simon; Edengeiser, Eugen; Jarzina, Fabian; Brinckmann, Steffen; Steinborn, Elena; Havenith, Martina; Benedikt, Jan; Bandow, Julia E

2013-12-01

332

Method of Synthesis of Electrode Materials with Controlled Particle Size for Lithium Batteries  

Microsoft Academic Search

\\u000a The particle size of the active cathode materials for lithium ion batteries plays an important role for the electrochemical\\u000a behaviour of the cell [1-5]. Two main technological principles are in the basis of proposed method of synthesis of active electrode materials with controlled\\u000a particle size: a convective drying in liquid agent followed by firing in gas media. Varying the parameters

S. Uzunova; B. Banov; A. Momchilov

333

Atmospheric Release Advisory Capability: Real-Time Modeling of Airborne Hazardous Materials.  

NASA Astrophysics Data System (ADS)

The Atmospheric Release Advisory Capability (ARAC) at Lawrence Livermore National Laboratory is a centralized federal project for assessing atmospheric releases of hazardous materials in real time. Since ARAC began making assessments in 1974, the project has responded to over 60 domestic and international incidents. ARAC can model radiological accidents in the United States within 30 to 90 min, using its operationally robust, three-dimensional atmospheric transport and dispersion models, extensive geophysical and dose-factor databases, meteorological data acquisition systems, and experienced staff. Although it was originally conceived and developed as an emergency response and assessment service for providing dose-assessment calculations after nuclear accidents, it has proven to be an extremely adaptable system, capable of being modified to respond also to non radiological hazardous releases. In 1991, ARAC responded to three major events: the oil fires in Kuwait, the eruption of Mt. Pinatubo in the Philippines, and an herbicide spill into the upper Saerarnento River in California. Modeling the atmospheric effects of these events added significantly to the range of problems that ARAC can address and demonstrated that the system can be adapted to assess and respond to concurrent, multiple, unrelated events at different locations.

Sullivan, Thomas J.; Ellis, James S.; Foster, Connee S.; Foster, Kevin T.; Baskett, Ronald L.; Nasstrom, John S.; Schalk, Walter W., III

1993-12-01

334

Using the Internet to Disseminate Educational Material on Atmospheric Composition Change in ACCENT  

NASA Astrophysics Data System (ADS)

ACCENT (2004-08) is a Network of Excellence in Atmospheric Composition Change in Framework Programme VI of the European Union (www.accent-network.org). The task "Training and Education" aims at preparing the next generation of atmospheric scientists (up to 3 years after completion of a Ph.D.) for the future of scientific endeavour in the field. Educational events, courses, and training workshops will be offered both on subjects in the field of atmospheric composition change and on essential skills (e.g., communication, networking, interdisciplinarity), and will be paralleled by leadership sessions and Science Cafes to increase the expertise to a common level across Europe (including Accession countries). Integration of female scientists, and (young) scientists from newly associated and emerging countries will be realized through specific schemes (e.g., mentoring, fellowships). Training and Education in ACCENT also aims at triggering the use of New Information and Communication Technologies (NICT). Examples will be presented on the varied use of NICT to disseminate educational material on atmospheric composition change, both at the undergraduate and at the postgraduate level, and to teachers.

Schuepbach, E.

2005-12-01

335

Inorganic salts interact with organic di-acids in sub-micron particles to form material with low hygroscopicity and volatility  

NASA Astrophysics Data System (ADS)

Volatility and hygroscopicity are two key properties of organic aerosol components, and both are strongly related to chemical identity. Here we show that inorganic-organic component interactions typically not considered in atmospheric models may strongly affect aerosol volatility and hygroscopicity. In particular, bi-dentate binding of di-carboxylic acids (DCA) to soluble inorganic ions can lead to very strongly bound metal-organic complexes with largely undetermined hygroscopicity and volatility. These reactions profoundly impact particle hygroscopicity, transforming hygroscopic components into irreversibly non-hygroscopic material. While the hygroscopicities of pure salts, DCA, and DCA salts are known, the hygroscopicity of internal mixtures of hygroscopic salts and DCA, as they are typically found in the atmosphere, has not been fully characterized. We have studied the volatility of pure, dry organic salt particles and the hygroscopicity of internal mixtures of oxalic acid (OxA, the dominant DCA in the atmosphere) and a number of salts, both mono- and di-valent. The formation of very low volatility organic salts was confirmed, with minimal evaporation of oxalate salt particles below 75 °C. Dramatic increases in the CCN activation diameter for particles with divalent salts (e.g. CaCl2) and relatively small particle mass fractions of OxA indicate that standard volume additivity rules for hygroscopicity do not apply. Thus small organic compounds with high O:C are capable of forming low volatility and very low hygroscopicity particles. Given current knowledge of the formation mechanisms of OxA and M-Ox salts, surface enrichment of insoluble M-Ox salts is expected. The resulting formation of an insoluble coating of metal-oxalate salts can explain low particle hygroscopicities. The formation of particles with a hard coating could offer an alternative explanation for observations of glass-like particles with very low viscosity.

Drozd, G.; Woo, J.; Häkkinen, S. A. K.; Nenes, A.; McNeill, V. F.

2013-11-01

336

The temporal record and sources of atmospherically deposited fly-ash particles in Lake Akagi-konuma, a Japanese mountain lake  

Microsoft Academic Search

Fly-ash particles comprising spheroidal carbonaceous particles (SCP) and inorganic ash spheres (IAS), produced from industrial\\u000a fossil-fuel combustion, are found in lake sediments throughout the world where they provide an historical record of atmospheric\\u000a pollutant deposition. These particles have been widely used to assess the temporal and spatial distribution of industrial\\u000a atmospheric pollution in both freshwater and terrestrial environments in Europe

Osamu Nagafuchi; Neil L. Rose; Akira Hoshika; Kenichi Satake

2009-01-01

337

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

338

Acoustic properties and durability of liner materials at non-standard atmospheric conditions  

NASA Technical Reports Server (NTRS)

This report documents the results of an experimental study on how acoustic properties of certain absorbing liner materials are affected by nonstandard atmospheric conditions. This study was motivated by the need to assess risks associated with incorporating acoustic testing capability in wind tunnels with semicryogenic high Reynolds number aerodynamic and/or low pressure capabilities. The study consisted of three phases: 1) measurement of acoustic properties of selected liner materials at subatmospheric pressure conditions, 2) periodic cold soak and high pressure exposure of liner materials for 250 cycles, and 3) determination of the effect of periodic cold soak on the acoustic properties of the liner materials at subatmospheric conditions and the effect on mechanical resiliency. The selected liner materials were Pyrell foam, Fiberglass, and Kevlar. A vacuum facility was used to create the subatmospheric environment in which an impedance tube was placed to measure acoustic properties of the test materials. An automated cryogenic cooling system was used to simulate periodic cold soak and high pressure exposure. It was found that lower ambient pressure reduced the absorption effectiveness of the liner materials to varying degrees. Also no significant change in the acoustic properties occurred after the periodic cold soak. Furthermore, mechanical resiliency tests indicated no noticeable change.

Ahuja, K. K.; Gaeta, R. J., Jr.; Hsu, J. S.

1994-01-01

339

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

340

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

NASA Astrophysics Data System (ADS)

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.

2006-09-01

341

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

342

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

343

Measurements of ultrafine particle concentration and size distribution in the urban atmosphere  

Microsoft Academic Search

Particle size distributions were measured at three adjacent sites in Birmingham: a busy roadside (A38); 30 m away from the road and a nearby urban background site. Two scanning mobility particle sizers (SMPS), an electrical low pressure impactor (ELPI), a condensation particle counter and a thermophoretic precipitator were employed to measure and collect particles. Excellent agreement on the number weighted

Ji Ping Shi; A. A. Khan; Roy M. Harrison

1999-01-01

344

Insights on Sources, Growth, and Phase Partitioning of Atmospheric Particles from Hourly Measurements of Organic Marker Compounds  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols have adverse affects on human health and have direct and indirect affects on the global radiation balance. In order to implement particle concentration control strategies, we must first understand particle origins. Atmospheric aerosols have both primary sources such as combustion processes and secondary sources such as photochemically driven gas to particle phase partitioning. By monitoring changes in the molecular composition of the organic fraction of atmospheric aerosols, these various sources can be differentiated. Thermal desorption Aerosol Gas chromatography (TAG) is a new in-situ instrument capable of identifying and quantifying organic aerosol chemical composition with one hour time resolution. TAG is fully automated, offering around the clock measurements to determine diurnal, weekly, and seasonal patterns in organic aerosol composition, hence, determining aerosol sources and transformation processes. We report results from ambient measurements made in Southern California during the summer and fall of 2005 as part of the Study of Organic Aerosol at Riverside (SOAR). We use hourly measurements of over 300 individual organic compounds to define both primary and secondary particle sources. The particle sources defined include primary anthropogenic sources such as vehicle emissions, meat cooking, biomass burning, pesticide use, herbicide use, along with primary biogenic sources such as plant emissions and plant waxes. We also explore secondary particle sources (i.e. SOA) formed as a result of the oxidation of biogenic and anthropogenic precursor gases. Comparisons are made between TAG-defined sources and aerosol sources defined using Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) and Aerosol Mass Spectrometer (AMS) data. In addition to source apportionment results, we present seasonal changes in ambient phase partitioning of organic compounds as a function of carbon number for multiple compound classes.

Williams, B.; Goldstein, A.; Kreisberg, N.; Hering, S.; Docherty, K.; Jimenez, J.; Shields, L.; Qin, X.; Prather, K.; Ziemann, P.

2007-12-01

345

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

NASA Astrophysics Data System (ADS)

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.

Rodrķguez-Fernįndez, Luis

2010-09-01

346

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

347

In vitro macrophage response to nanometer-size particles from materials used in hip implants  

NASA Astrophysics Data System (ADS)

Wear particle-induced inflammation leading to periprosthetic osteolysis remains a major cause of hip implant failure. As polyethylene particles from conventional metal-on-polyethylene implants have been associated with these failures, an interest in lower wear metal-on-metal (MM) bearings has emerged. However, the biological effects of nanometer-size chromium oxide particles, predominant type of wear particles produced by MM implants, remain mostly unknown. Therefore, this study aimed to determine the cytotoxicity of nanometer-size Cr2O3 particles on macrophages in vitro, by analyzing their effects on cell mortality and cytokine release and comparing them with those of similarly-sized alumina (Al2O3) particles (known to be relatively bioinert). Results showed that at high concentrations, nanometer-size Cr2O3 particles can be cytotoxic to macrophages, inducing significant decreases in total cell numbers and increases in necrosis. Results also showed that, at high concentrations, the cytotoxicity of Cr 2O3 particles was overall higher than that of Al2O 3 particles, even though Cr2O3 and Al2O 3 are both stable forms of ceramic materials. However, it appeared to be lower than that of previously reported conventional polyethylene and CoCrMo particles. Therefore, chromium oxide particles may not be the main culprit in initiating the inflammatory reaction in MM periprosthetic tissues.

VanOs, Robilyn

348

Air Quality Impacts of Atmospheric Particles & Trace Gases: Field Studies in Diverse Environments  

NASA Astrophysics Data System (ADS)

Air pollution impacts occur at all scales, meaning that policies and air quality management practices must be implemented and coordinated at the local, regional, national, and global scales. This dissertation is part of a continuing effort to improve our understanding of various air quality related issues in different environments. The dissertation consists of four studies. In the first study, wintertime chemical composition of water-soluble particulate matter with aerodynamic diameter less than 2.5 microm (PM2.5) was monitored in the Treasure Valley region near Boise, Idaho. This study was aimed at understanding the major drivers of wintertime PM2.5 within the locality of Boise and its suburbs. From this study, organics and particulate nitrate were the dominant contributors to the PM2.5 mass during wintertime. In the second study, particle size distribution, light scattering coefficient, speciated water soluble PM2.5, and cloud condensation nuclei (CCN) concentration were monitored in a mixed deciduous forest in Northern Michigan during the Community Atmosphere-Biosphere Interactions Experiment (CABINEX-2009). The overall goal of this study was to understand on how emissions of biogenic volatile organic compounds (BVOC) affect the gas-phase and particle-phase chemistry in the near-canopy environment, and the implications on local and regional air quality. From this study aerosol derived from the oxidation of BVOCs exhibited reduced hygroscopicity and CCN activation potential compared to aerosols derived from anthropogenic activities. The third study employed the eddy covariance (EC) technique to understand source-sink interactions of carbon dioxide (CO2), methane (CH 4), carbon monoxide (CO) and nitrous oxide (N2O) in Xi'an, China. In this study urban vegetation were found to play a major role in regulating CO2 emissions within the city while vehicular activities were a major driver for CO and CH4 fluxes. In the fourth study, visibility degradation effects of nitrogen oxide (NO) and nitrogen dioxide (NO2) emissions from a natural gas compressing facility in southern Idaho were evaluated and quantified. In addition, several retrofit technologies were evaluated based to their ability to reduce NOx (NO + NO2) emissions. From this study selective catalytic reduction (SCR) was found to be the most appropriate technology to reduce NOx emissions from the facility.

Mwaniki, George R.

349

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

350

Atmospheric input of POPs into Lake Maggiore (Northern Italy): PBDE concentrations and profile in air, precipitation, settling material and sediments  

Microsoft Academic Search

Large lakes are sinks for many chemical pollutants but the role of the atmosphere in delivering PBDEs (polybrominated diphenyl ethers) is not well known. In this study we estimated inputs of PBDEs from the atmosphere to Lake Maggiore and the delivery via settling material to accumulated bottom sediments. Sampling consisted of one simultaneous week of air and bulk deposition during

G. Mariani; E. Canuti; J. Castro-Jiménez; E. H. Christoph; S. J. Eisenreich; G. Hanke; H. Skejo; G. Umlauf

2008-01-01

351

Particle size and time of the day influences on the morphology distributions of atmospheric fine particles at the Baltimore supersite  

NASA Astrophysics Data System (ADS)

The morphology of size-classified ambient particulate matter less than 2.5 ?m in aerodynamic diameter (PM 2.5) was studied in samples collected at the USEPA supersite located in Baltimore, MD. Size classification was accomplished through the use of a low pressure impactor to produce samples with cut-off diameters of 0.10, 0.15, 0.55, and 2.0 ?m. Sampling was conducted in two campaigns during the fall of 2002, with separate sampling occurring during early morning, mid-day, late afternoon, and evening periods. Particles with cut-off diameters of 2 ?m were generally round in shape, with a border fractal dimension close to 1 based on the analysis of transmission electron microscope (TEM) images of collected samples. Particles with a cut-off diameter of 0.15 ?m had on average higher fractal dimensions than the other size classes considered, regardless of time of day associated with the sample. As expected, the time of the day influenced the shape of particle populations sampled. Particles collected during early morning were found to have higher fractal dimension than those collected at other sampling times. At night, particles presented mostly round shapes. This difference was particularly pronounced in particles with cut-off diameters of 0.15 ?m.

Mamani-Paco, Ruben M.; Helble, Joseph J.

352

Surface-enhanced Raman spectroscopy of Vitamin B 12 on silver particles in colloid and in atmosphere  

NASA Astrophysics Data System (ADS)

The surface-enhanced Raman scattering (SERS) spectra of Vitamin B 12 molecules on silver surface in colloid and in atmosphere were obtained with very low laser power. The SERS on silver surface in atmosphere shows more intense enhancement with sharper and narrower Raman peaks compared with the SERS in colloid. The adsorption geometries of Vitamin B 12 molecules were analyzed based on the SERS data. Vitamin B 12 molecule is supposed to adsorb on the silver particle in colloid with the corrin ring plane nearly vertical to the surface, while Vitamin B 12 molecule is supposed to adsorb on silver surface with the corrin ring plane tilted to the surface. This could be due to the water effect of the molecular conformation and the characteristic of silver particles.

Zhang, Zhenlong; Wang, Bo; Yin, Yanfeng; Mo, Yujun

2009-06-01

353

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

354

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 ...

355

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

...2013-10-01 2013-10-01 false Which pipelines must I protect against atmospheric corrosion...Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION...DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF...

2013-10-01

356

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

357

Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer  

Microsoft Academic Search

Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B&W seven-cylinder four-stroke marine diesel engine under various load

A. Petzold; J. Hasselbach; P. Lauer; R. Baumann; K. Franke; C. Gurk; H. Schlager; E. Weingartner

2007-01-01

358

Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer  

Microsoft Academic Search

Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B&W seven-cylinder four-stroke marine diesel engine under various load

A. Petzold; J. Hasselbach; P. Lauer; R. Baumann; K. Franke; C. Gurk; H. Schlager; E. Weingartner

2008-01-01

359

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

360

Atmospheric pressure plasma pretreatment of sugarcane bagasse: the influence of biomass particle size in the ozonation process.  

PubMed

Atmospheric pressure O? plasma was used to produce ozone in order to treat sugarcane bagasse as a function of particle sizes. The fixed bagasse moisture content was 50%. The delignification efficiency had small improvement due to ozonation process as a function of particle size, varying from 75 up to 80%. Few amounts of hemicellulose were removed, but the ozonation has not been affected significantly with particle size variance as well (from 30 up to 35%). The cellulose presented some losses below 1.0 mm size (8-15%) which was an unexpected result. The conversion of cellulose content into free sugar has shown a significant increase as the particle size has diminished as well. The best condition of the bagasse particle size was for 0.08 mm. For this case, a great quantity of cellulose (78.8%) was converted into glucose. Optical absorption spectroscopy was applied to determine ozone concentrations in real time where the samples with typical bagasse particle sizes equal or below to 0.5 mm had shown a better absorption of ozone in comparison with greater particle size samples. PMID:24242163

Souza-Corrźa, J A; Oliveira, C; Nascimento, V M; Wolf, L D; Gómez, E O; Rocha, G J M; Amorim, J

2014-02-01

361

The deformation and cooling of ceramic particles sprayed with a thermal radio-frequency plasma under atmospheric conditions  

NASA Astrophysics Data System (ADS)

Common thermal-spray techniques use the strong acceleration of powder particles to produce dense ceramic coatings with high bond strength. The residence time of the powder particles within the plasma jet is correspondingly low, and only relatively small particles can be molten. In this work, on the contrary, an inductively coupled radio-frequency (RF) inductively coupled plasma (ICP) torch was used to spray large oxide-ceramic powder particles under atmospheric conditions. The slow plasma flow of a RF plasma leads to large residence times of the powder particles, so that the powder size of the feedstock can be 100 µm and more. It was observed that these particles will not be strongly accelerated in the plasma and that their velocity at the moment of impact is in the range of 10 to 20 m/s. Ceramic coatings were ICP sprayed with a low porosity and a high bond strength, similar to direct current (DC) or high-velocity-oxygen-fuel (HVOF) sprayed coatings. The morphology of ICP-sprayed particles on smooth steel surfaces, as a function of the surface temperature, is described and compared with DC plasma-sprayed splats. Furthermore, the degree of deformation was measured and determined by different models, and the pronounced contact zones formed between the pancake and the substrate were investigated. The ICP-sprayed ceramic coatings show some special properties, such as the absence of metastable crystalline phases, which are common in other spray technologies.

Dzur, B.; Wilhelmi, H.; Nutsch, G.

2001-12-01

362

LWS Studies of Gamma Rays Produced in the Earth's Atmosphere by Cosmic Rays and Solar Energetic Particle Events  

NASA Astrophysics Data System (ADS)

We summarize a three-year study of atmospheric gamma-ray line measurements conducted under the Living With a Star program. The observations were made by instruments on three satellites: SMM, Yohkoh, and RHESSI. They detected the 511-keV positron annihilation line produced in electromagnetic showers and de- excitation lines from 14N at 728, 1635, 2313, 3890, and 5106 keV, and from 16O at 6129 keV, as well as spallation lines near 4440 keV from 12C and 11B produced by neutron and proton interactions on Earth's atmosphere. The SMM studies focused on the variation of the cosmic-ray produced lines as a function of magnetic rigidity and solar cycle modulation. We found that the power-law spectral index of the secondary neutrons was relatively constant for the range of times and rigidity intervals sampled. The Yohkoh and RHESSI studies focused on atmospheric gamma rays produced by solar energetic particles interacting in the Earth's atmosphere following flares on 2000 July 14 and 2002 April 21, respectively. The SEP spectra estimated using gamma-ray line ratios were of comparable hardness with the spectrum measured by SMM for the 1989 October 20 intense event, consistent with measurements in space. Improved cross sections for the production of the nuclear lines offer better estimates of the spectra of SEPs impacting the atmosphere. Since the early observations, RHESSI has observed several more SEP events producing detectable fluxes of atmospheric gamma rays. These include large particle events in 2003 October/November and 2005 January.

Murphy, R. J.; Share, G. H.; Kozlovsky, B. Z.

2006-12-01

363

Growth of new particle in less and highly polluted atmosphere: Implication for an important role of NH4NO3 in growing new particles to CCN size  

NASA Astrophysics Data System (ADS)

When new particles formed in the atmosphere grow over 50-80 nm, they will activate as cloud condensation nuclei (CCN) and lead to an increase of cloud albedo. Knowledge gaps still existed, e.g., 1) new particles under which conditions can grow to CCN size? 2) which chemicals determine the growth of new particles to CCN size? In this study, new particle formation (NPF) events were investigated at two urban sites, in Qingdao during 23 April and 31 May, 2010, and in Toronto during 1 May and 31 May, 2009, using two identical Fast Mobility Particle Sizer (FMPS). Based on the satellite column densities of air pollutants and the particulate chemical concentration in PM2.5, the site in Qingdao suffered severe air pollution while the site in Toronto is less polluted. NPF events were observed in 16 days out of 39 sampling days in Qingdao and 13 days out of 31 sampling days in Toronto. The occurrence frequency of NPF events between Qingdao (41%) and Toronto (42%) was comparable to each other. In Qingdao, the geometric mean diameter of grown nucleated particles (Dpg,i) in 15 days grew to larger than 40 nm except in one day when the growth of new particles terminated at ~20 nm. In addition, the Dpg,i in 8 days out of the 15 days grew over 50 nm and it reached ~100 nm in two days. Two-phase growth of new particles was generally observed in these NPF events of Qingdao. The first-phase growth occurred in daytime and the CMAQ modeling results showed that formation of secondary organics was likely an important cause for the growth. The second-phase growth was observed at night and was associated with the increased concentrations of NH4+ and NO3-, implying that NH4NO3 condensation played an important role in the growth. In Toronto, NPF events in 4 days followed with the growth of new particles <~20 nm while new particles grew up to ~40 nm in the remaining NPF events. A slight growth of new particles at night was observed only in 3-day NPF events when the increased concentrations of NH4+, NO3- or the increased relative humidity were observed. However, the calculated Dpg,i was less than 45 nm for all NPF events in Toronto, implying a negligible contribution of new particles to the population of CCN.

Zhu, Y.; Gao, H.; Duan, Z. Q.; Evans, G. J.; Yao, X.

2013-12-01

364

The Effect of Cloud Particle Size on Climate Using an Atmosphere-Ocean Coupled General Circulation Model  

NASA Astrophysics Data System (ADS)

Recently, there have been some studies suggesting that the variation of solar activity affects the production of cloud condensation nuclei (CCN). If the production of CCN changes, it may be expected that the size of cloud particles would change because more (less) CCN may result in more (less) and smaller (larger) cloud particles. In this study, the cloud particle sizes in the atmospheric radiation computation in an atmosphere-ocean coupled general circulation model, called CFES (Coupled model For the Earth Simulator), are changed in order to investigate the effect of cloud particle size on global climate. The resolution of CFES is T119L48 (horizontally 1-degree and 48 vertical levels) for the atmospheric part, and horizontally 0.5-degree and 54 vertical levels for the ocean. The atmospheric radiation code is MSTRN-X, a Japanese community model. The cloud particle sizes are, for default, 20 micron meters for liquid stratus, 30 for liquid cumulus, 10 for solid stratus and 15 for solid cumulus. The Control run is conducted for 120 years. The last 20 years are analyzed. Additionally, two sensitivity numerical experiments are conducted. In the Half run, the cloud particle sizes are halved. The sizes are doubled in the Double run. It should be mentioned that the effect of cloud particle size on precipitation efficiency is not included in the simulations. Both runs are run from January 1 of the 101st year of Control for 20 years. The global mean surface air temperature in Control is about 287.5 K. After 20-year simulations, the global mean surface temperature is 3.7 K colder for Half than Control and 3.7 K warmer for Double. High clouds warm the Earth, and low clouds cool the Earth because their . The low cloud amount in Double (Half) decreases (increases). It is consistent with the temperature changes. Some implications for paleoclimate, current climate and future climate will be also discussed.; Time series of global mean surface air temperature. Abscissa is year, and ordinate is temperature in K. Black curve is for Control, blue for Half, and red for Double.

Ohfuchi, W.; Chikaraishi, Y.; Suzuki, R.; Kusano, K.; Taguchi, B.; Kataoka, R.; Miyahara, H.; Maruyama, S.; Hamano, Y.

2012-12-01

365

Heterogeneous chemical kinetics and particle nucleation in interstellar and atmospheric environments  

NASA Astrophysics Data System (ADS)

Dust is believed to play a significant role in the evolution of interstellar clouds and hence in processes such as star formation. The physics involved is similar to that responsible for terrestrial aerosols. Certain chemical reactions in interstellar conditions may only occur on the surface of a host particle and are not viable purely in the gas phase. The traditionally used rate equations approach to describe these reactions fail to account for the statistical fluctuations in the reactant populations, which would be significant in situations where the mean population may be well below unity. This can easily occur in interstellar conditions and quite often in reactions catalysed by terrestrial aerosols. This thesis considers a master equation approach that provides a stochastic description of heterogeneous chemical kinetics and demonstrates that classical kinetics may have been overestimating the reaction rates by one order of magnitude under interstellar conditions. The same idea can be extended to study mantle growth on dust surfaces. Traditionally, this is described using a classical description of nucleation kinetics, generally suitable for large systems. Again, this can be unreliable for heterogeneous nucleation taking place on small particles under low vapour concentration where the mean population of adsorbed nucleating species could be of order unity or less. The the-sis explores a stochastic description of heterogeneous nucleation kinetics and solves the arising equations numerically to demonstrate that the stochastic nucleation rate could be significantly different from that derived using the traditional approach. The chemical composition of interstellar dust has for long puzzled experts. The key to determining this lies in an accurate description of the physical processes underlying the formation of these particles. Magnesium oxide is considered to be one of the major candidates as the primary nucleating material, but recently doubts have been cast over this. However, the models employed in reaching that conclusion seem to be rather inaccurate. The thesis attempts to calculate free energies of molecular clusters using newly designed potential models for MgO. It is found that MgO is probably not the primary nucleating dust species in stellar winds.

Bhatt, Jayesh

366

PLASMA WINDOW FOR VACUUM - ATMOSPHERE INTERFACE AND FOCUSING LENS OF SOURCES FOR NON-VACUUM MATERIAL MODIFICATION.  

SciTech Connect

Material modifications by ion implantation, dry etching, and micro-fabrication are widely used technologies, all of which are performed in vacuum, since ion beams at energies used in these applications are completely attenuated by foils or by long differentially pumped sections, which ate currently used to interface between vacuum and atmosphere. A novel plasma window, which utilizes a short arc for vacuum-atmosphere interface has been developed. This window provides for sufficient vacuum atmosphere separation, as well as for ion beam propagation through it, thus facilitating non-vacuum ion material modification.

HERSHCOVITCH,A.

1997-09-07

367

Identification of sources of atmospheric PM at the Pittsburgh Supersite—Part II: Quantitative comparisons of single particle, particle number, and particle mass measurements  

NASA Astrophysics Data System (ADS)

A single particle mass spectrometer, RSMS-3, and a MOUDI were deployed during the Pittsburgh Air Quality Study (PAQS), July 2001-September 2002, to obtain size resolved measurements of elemental composition for particulate matter (PM) within the Pittsburgh area. Elemental mass distributions from analysis of the MOUDI stages were directly compared to those constructed using the single particle data, in conjunction with coincident SMPS measurements, for specific days within the PAQS. Results from one episode on 27 October 2001 showed that approximately 80% of the metal containing particles detected on this day belonged to the Na/Si/K/Ca/Fe/Ga/Pb particle class. The density and shape factor of these particles were estimated to be 3.9±0.8 g/cc and 1.5±0.2, respectively, and the relative sensitivity factors for individual metals showed little variation with respect to particle diameter over the size range of 70-800 nm. Compared to the 27 October 2001 episode, there was a larger degree of variability in the metal containing particles detected during another episode on 14 March 2002. The Ca and Pb mass distributions from this day represent an ensemble of externally mixed particles. Estimates of particle density were provided for the dominant particle types, including EC/OC/Ca, Al/Si/Ca/Fe, EC/OC/Pb and Na/K/Zn/Pb, and estimates of particle shape factor were provided for the EC/OC/Ca and Na/K/Zn/Pb classes. Comparison with the 27 October 2001 Ca and Pb mass distributions revealed that the RSMS data reconstructed the MOUDI mass much better from the Ca/Pb containing particles detected on 14 March 2002 than those observed on 27 October 2001, suggesting that the single particle instrument sensitivity to both Ca and Pb depends on the particle matrix.

Bein, Keith J.; Zhao, Yongjing; Pekney, Natalie J.; Davidson, Cliff I.; Johnston, Murray V.; Wexler, Anthony S.

368

Organic particulate material levels in the atmosphere: Conditions favoring sensitivity to varying relative humidity and temperature  

PubMed Central

This study examines the sensitivity in predicted levels of atmospheric organic particulate matter (Mo, ?g m-3) as those levels may potentially be affected by changes in relative humidity and temperature. In a given system, for each partitioning compound, fg and fp represent the gaseous and particulate fractions (fg + fp = 1). Sensitivity in the Mo levels becomes dampened as the compounds contributing significantly to Mo are increasingly found in the particle phase (fp ? 1). Thus, although local maxima in sensitivity can be encountered as Mo levels increase, because as Mo increases each fp ? 1, then increasing Mo levels generally tend to reduce sensitivity in Mo levels to changes in relative humidity and temperature. Experiments designed to elucidate the potential magnitudes of the effects of relative humidity and temperature on Mo levels must be carried out at Mo levels that are relevant for the ambient atmosphere: The fp values for the important partitioning compounds must not be elevated above ambient-relevant values. Systems in which Mo levels are low (e.g., 1–2 ?g m-3) and/or composed of unaged secondary organic aerosol are the ones most likely to show sensitivity to changing relative humidity and temperature. Results from two published chamber studies are examined in the above regard: [Warren B, et al. (2009) Atmos Environ 43:1789–1795] and [Prisle NL, et al. (2010) Geophys Res Lett 37:L01802].

Pankow, James F.

2010-01-01

369

Brominated flame retardants in the urban atmosphere of Northeast China: Concentrations, temperature dependence and gas-particle partitioning.  

PubMed

57 pairs of air samples (gas and particle phases) were collected using a high volume air sampler in a typical city of Northeast China. Brominated flame retardants (BFRs) including 13 polybrominated diphenyl ethers (PBDEs, including BDEs 17, 28, 47, 49, 66, 85, 99, 100, 138, 153, 154, 183, and 209) and 9 alternative BFRs (p-TBX, PBBZ, PBT, PBEB, DPTE, HBBZ, ?-HBCD, BTBPE, and DBDPE) were analyzed. The annual average total concentrations of the 13 PBDEs and the 9 alternative BFRs were 69pg/m(3) and 180pg/m(3), respectively. BDE 209 and ?-HBCD were the dominant congeners, according to the one-year study. The partial pressure of BFRs in the gas phase was significantly correlated with the ambient temperature, except for BDE 85, ?-HBCD and DBDPE, indicating the important influence of ambient temperature on the behavior of BFRs in the atmosphere. It was found that the gas-particle partitioning coefficients (logKp) for most low molecular weight BFRs were highly temperature dependent as well. Gas-particle partitioning coefficients (logKp) also correlated with the sub-cooled liquid vapor pressure (logPL(o)). Our results indicated that absorption into organic matter is the main control mechanism for the gas-particle partitioning of atmospheric PBDEs. PMID:24661943

Qi, Hong; Li, Wen-Long; Liu, Li-Yan; Song, Wei-Wei; Ma, Wan-Li; Li, Yi-Fan

2014-09-01

370

Biotic carbon feedbacks in a materially closed soil-vegetation-atmosphere system  

NASA Astrophysics Data System (ADS)

The magnitude and direction of the coupled feedbacks between the biotic and abiotic components of the terrestrial carbon cycle is a major source of uncertainty in coupled climate-carbon-cycle models. Materially closed, energetically open biological systems continuously and simultaneously allow the two-way feedback loop between the biotic and abiotic components to take place, but so far have not been used to their full potential in ecological research, owing to the challenge of achieving sustainable model systems. We show that using materially closed soil-vegetation-atmosphere systems with pro rata carbon amounts for the main terrestrial carbon pools enables the establishment of conditions that balance plant carbon assimilation, and autotrophic and heterotrophic respiration fluxes over periods suitable to investigate short-term biotic carbon feedbacks. Using this approach, we tested an alternative way of assessing the impact of increased CO2 and temperature on biotic carbon feedbacks. The results show that without nutrient and water limitations, the short-term biotic responses could potentially buffer a temperature increase of 2.3°C without significant positive feedbacks to atmospheric CO2. We argue that such closed-system research represents an important test-bed platform for model validation and parameterization of plant and soil biotic responses to environmental changes.

Milcu, Alexandru; Lukac, Martin; Subke, Jens-Arne; Manning, Pete; Heinemeyer, Andreas; Wildman, Dennis; Anderson, Robert; Ineson, Phil

2012-04-01

371

Anthropogenic Influence on Secondary Aerosol Formation and Total Water-Soluble Carbon on Atmospheric Particles  

NASA Astrophysics Data System (ADS)

On a global scale, the atmosphere is an important source of nutrients, as well as pollutants, because of its interfaces with soil and water. Important compounds in the gaseous phase are in both organic and inorganic forms, such as organic acids, nitrogen, sulfur and chloride. In spite of the species in gas form, a huge number of process, anthropogenic and natural, are able to form aerosols, which may be transported over long distances. Sulfates e nitrates are responsible for rain acidity; they may also increase the solubility of organic compounds and metals making them more bioavailable, and also can act as cloud condensation nuclei (CCN). Aerosol samples (PM2.5) were collected in a rural and industrial area in Rio de Janeiro, Brazil, in order to quantify chemical species and evaluate anthropogenic influences in secondary aerosol formation and organic compounds. Samples were collected during 24 h every six days using a high-volume sampler from August 2010 to July 2011. The aerosol mass was determined by Gravimetry. The water-soluble ionic composition (WSIC) was obtained by Ion Chromatography in order to determine the major anions (NO3-, SO4= and Cl-); total water-soluble carbon (TWSC) was determined by a TOC analyzer. The average aerosol (PM2.5) concentrations ranged from 1 to 43 ug/m3 in the industrial site and from 4 to 35 ug/m3 in the rural area. Regarding anions, the highest concentrations were measured for SO42- (10.6 ?g/m3-12.6 ?g/m3); where the lowest value was found in the rural site and the highest in the industrial. The concentrations for NO3- and Cl- ranged from 4.2 ?g/m3 to 9.3 ?g/m3 and 3.1 ?g/m3 to 6.4 ?g /m3, respectively. Sulfate was the major species and, like nitrate, it is related to photooxidation in the atmosphere. Interestingly sulfate concentrations were higher during the dry period and could be related to photochemistry activity. The correlations between nitrate and non-sea-salt sulfate were weak, suggesting different sources for these species. The secondary aerosol represented an important fraction of total compounds in PM2.5 ranged from 16 to 18% for (NH4)2SO4 and 6 to 8% for NH4NO3. The values for TWSC ranged from 0.28 to 6.35 ?g/m3 in the industrial area and 0.12 to 7.49 ?g/m3 for rural area. The similarity between the areas regarding secondary aerosols formation and water-soluble carbon compounds is probably due to the particle size.

Gioda, Adriana; Mateus, Vinicius; Monteiro, Isabela; Taira, Fabio; Esteves, Veronica; Saint'Pierre, Tatiana

2013-04-01

372