Elemental Composition Of Individual Particles Research Articles

Characterisation of Sugar Cane Combustion Particles in the Araraquara Region, Southeast Brazil

Biomass burning is an important primary and secondary source of aerosol particles. The presence of carbonaceous particles in the respirable size range makes the study of this fraction important in view of possible health and climatic effects. The annual burning of sugar cane plantations causes emission of huge amounts of pyrogenic particles. Aerosol samples were collected in Araraquara city, Sao Paulo state, Brazil, during the harvest season for fine and coarse particles and bulk; they were analysed by electron-probe microanalysis, including facilities for low-Z element determination (low-Z EPMA) and by energy-dispersive X-ray fluorescence (EDXRF), in order to investigate the elemental composition of individual particles and bulk samples, respectively. Numerical analysis of the EPMA results by hierarchical clustering shows high contributions of carbonaceous particles that can be distinguished mainly in two different types: biogenic and carbon-rich. Additionally, two significant contributions of aluminosilicate particles were identified: as rather pure aluminosilicates or mixed with carbonaceous species. The EDXRF results are compatible with those of aerosol particles in Amazon, which is nowadays one of the main sources of biogenic particles in the world.

Measurement of Condensed-Phase Reaction Kinetics in the Aerosol Phase Using Single Particle Mass Spectrometry

We applied a recently developed single particle mass spectrometer to analyze the elemental composition of individual aerosol particles and applied the technique to study the kinetics of thermal decomposition of metal nitrate aerosols (aluminum, calcium, silver, and strontium). Such decomposition processes on the industrial scale is known as spray pyrolysis and is a common method for making metal and metal oxide particles. Metal nitrate aerosols were passed through a tube furnace to induce thermal decomposition and transformation into oxides, and were delivered with high efficiency into the vacuum system of the single particle mass spectrometer using an aerodynamics lens arrangement. The particles were ablated and torn down to atomic ions with a tightly focused, high-power pulsed laser in the extraction field of the time-of-flight mass spectrometer. The mass spectra thus obtained are shown to carry a quantitative signature of the elemental composition of individual particles, and allow for on-line measurem...

Elemental compositions of individual aerosol particles collected over the Southern Ocean: A case study

Marine aerosols have been sampled from the boundary layer over the Southern Ocean. By means of X-ray spectrometry, elemental compositions of individual particles have been studied. The data reveal the occurrence of two chemical processes over the Southern Ocean: (1) modification of sea salts by acidic materials, where Cl − is replaced by SO 4 2− and/or NO 3 − and (2) fractional recrystallization within evaporating seawater drops followed by shattering. The effects of these phenomena appear to be simultaneously enhanced when there is mass transfer from the free troposphere.

Reduction of sampling and analytical errors for electron microscopic analysis of atmospheric aerosols

Electron microscopy-energy dispersive spectroscopy (EM/EDS) can be used to determine the elemental composition of individual particles. However, the accuracy with which atmospheric particle compositions can be quantitatively determined is not well understood. In this work we explore sources of sampling and analytical bias and methods of reducing bias. Sulfuric acid [H 2SO 4] and ammonium sulfate [(NH 4) 2SO 4] particles were collected on beryllium, silicon, and carbon substrates with similar deposition densities. While [(NH 4) 2SO 4] particles were observed on all substrates, [H 2SO 4] and ammonia-treated [H 2SO 4] particles could not be found on beryllium substrates. Interactions between the substrate and sulfuric acid particles are implicated. When measured with EM/EDS, [H 2SO 4] particles exposed to ammonia overnight were found having lower beam damage rates (0.000 ± 0.002 fraction s −1) than those without any treatment (0.023 ± 0.006 fraction s −1) For laboratory-generated [C 10H 6(SO 3Na) 2] particles, the composition determined using the experimental k-factors evaluated from independent particle standards of similar composition and size shows an error less than 20% for all constituents, while greater than 78% errors were found when k-factors were calculated from the theory. This study suggests (1) that sulfate beam damage can be reduced by exposure of atmospheric particle samples to ammonia before analysis, (2) that beryllium is not a suitable substrate for atmospheric particle analysis, and (3) calibration ( k-factor determination) using particle standards of similar size and composition to particles present in the atmosphere shows promise as a way of improving the accuracy of quantitative EM analysis.

Gravimetric analysis, ionic composition, and associated water mass of the marine aerosol

Measurements of the total aerosol mass and ionic composition were obtained for submicrometer ( D p ⩽ 1.0 μm) aerosol particles from the remote Pacific boundary layer by gravimetric and ion chromatography analysis. Discrepancies were found to exist between the absolute mass determined by the separate techniques suggesting aerosol components in addition to sea salt and sulfate particles exist at significant mass concentrations. The gravimetric mass was equal to or significantly larger than the sum of the ionic masses, suggesting additional aerosol components contribute between 0 and 75% of the submicrometer aerosol mass. Measurements of the elemental composition of individual particles by electron microscopy confirmed the presence of mineral and carbonaceous particles which contributed 0–86% of the total number concentration for the particle-size range of interest. The relative number of submicrometer sulfate particles with respect to the total was low during periods with the largest discrepancy between the gravimetric and ionic mass. The amount of water associated with the submicrometer aerosol at 47% relative humidity made up 29% of the total aerosol mass collected on the filters (and 9% of the total mass at 35%). Laboratory studies determined the relative amount of water associated with sea salt, sulfate, and sodium chloride particles on a filter substrate, with sea-salt particles containing 27% water and ammonium sulfate particles containing only 4% water at 40% r.h.

Elemental analysis of non-living particles in picoplankton fractions from oligotrophic lake water

Electron microscopic (TEM) study of bacterial-sized planktonic fractions recovered from the water column samples of a small oligotrophic lake, consistently showed the presence of non-living organic and inorganic particles as prominent parts of the micro habitat. An all important objective of this work was to determine the composition and possible origins of the minute particles. They were of several morphological types, described by transmission electron microscopic (TEM) appearance as: spherical, oblong, cuboidal, plates and fibrillar. The TEM used in the scanning transmission mode (STEM) in conjunction with the Princeton Gamma Tech (PGT) System 4 energy dispersive X-ray spectrometer (EDX) allowed the determination of the elemental composition of individual particles. The particles referred to as spherical were electron dense and were less than 1 μm in diameter. They were mainly composed of either Fe or Ti but not both. Cuboidal iron particles 37–75 nm in diameter were found in about equal abundance, but they were arranged in chains of individuals. Oblong particles were from 0.18 to 0.2 nm in width to 0.2 to 0.45 μm in length. Most were composed mainly of Ca, S and O but other elemental compositions were observed also. Plates with jagged edges composed of Al and Si were somewhat electron transparent. Both were less than 1 μm in largest dimension. Fibrillar particles were most abundant and were composed of Fe, Si, Cl, K, Na, O and C. They ranged from 90 Å to 37 nm in thickness and 1 μm to several μm in length. Particles of planktonic origin were observed with regularity including fragments of diatom cell walls and scales. These particles were composed of Si and O. Hexagonally shaped virus-like particles of several sizes were observed also. The relationship between elements in micro particles and their possible origins are discussed.

Aerosol particles in the Kuwait oil fire plumes: Their morphology, size distribution, chemical composition, transport, and potential effect on climate

Airborne aerosol samples were collected with an impactor in the Kuwait oil fire plumes in late May 1991. A transmission electron microscope was used to examine the morphology and size distribution of the particles, and an X ray energy spectrometer was used to determine the elemental composition of individual particles. A chemical spot test was used to identify particles containing sulfate. The results show that the dominant particles were (1) agglomerates of spherical soot particles coated with sulfate, (2) cubic crystals containing NaCl and S04=, (3) irregular‐shaped dust containing Si, Al, Fe, Ca, K, and/or S, and (4) very small ammonium sulfate spherules. The concentrations of small sulfate particles increased at higher levels or greater distances from the fire, suggesting the transformation of SO2 gas to sulfate particles by photooxidation followed by homogeneous nucleation. The number of soot, salt, and dust particles that were coated with sulfate increased farther from the fire, and the thickness of the coating increased with altitude. This suggested that gas‐to‐particle conversion had occurred by means of catalytic oxidation combined with heterogeneous nucleation during the plume dispersion. Because the sulfate coating can modify the hydrophobic surfaces of soot and dust particles to make them hydrophilic, most of the particles in the plume apparently were active cloud condensation nuclei that could initiate clouds, fog, and smog, which in turn could affect regional surface temperature, air quality, and visibility. Long‐range air trajectories suggested that some aerosols from the fires could have transported to eastern Asia. It seems possible (but is presently unproven) that a severe flood in China in June was influenced by aerosols from the plumes.

Interstellar grains within interstellar grains

view Abstract Citations (142) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar Grains within Interstellar Grains Bernatowicz, Thomas J. ; Amari, Sachiko ; Zinner, Ernst K. ; Lewis, Roy S. Abstract Five interstellar graphite spherules extracted from the Murchison carbonaceous meteorite are studied. The isotopic and elemental compositions of individual particles are investigated with the help of an ion microprobe, and this analysis is augmented with structural studies of ultrathin sections of the grain interiors by transmission electron microscopy. As a result, the following procedure for the formation of the interstellar graphite spherule bearing TiC crystals is inferred: (1) high-temperature nucleation and rapid growth of the graphitic carbon spherule in the atmosphere of a carbon-rich star, (2) nucleation and growth of TiC crystals during continued growth of the graphitic spherule and the accretion of TiC onto the spherule, (3) quenching of the graphite growth process by depletion of C or by isolation of the spherule before other grain types could condense. Publication: The Astrophysical Journal Pub Date: June 1991 DOI: 10.1086/186054 Bibcode: 1991ApJ...373L..73B Keywords: Carbon Isotopes; Carbonaceous Meteorites; Graphite; Interstellar Matter; Spherules; Abundance; Cosmic Dust; Electron Microscopy; Stellar Atmospheres; Titanium Carbides; Astrophysics; ABUNDANCES; INTERSTELLAR: MATTER; METEORS AND METEORITES; NUCLEOSYNTHESIS full text sources ADS |

Eds Of Radioactive Particles By Self-Induced Fluorescence

The elemental composition of individual particles is commonly measured by using energydispersive spectroscopic microanalysis (EDS) of samples excited with electron beam irradiation. Similarly, several investigators have characterized particles by using external monochromatic X-irradiation rather than electrons. However, there is little available information describing measurements of particulate characteristic X rays produced not from external sources of radiation, but rather from internal radiation contained within the particle itself. Here, we describe the low-energy (< 20 KeV) characteristic X-ray spectra produced by internal radiation self-excitation of two general types of particulate samples; individual radioactive particles produced during the Chernobyl nuclear reactor accident and radioactive fused aluminosilicate particles (FAP). In addition, we compare these spectra with those generated by conventional EDS.Approximately thirty radioactive particle samples from the Chernobyl accident were on a sample of wood that was near the reactor when the accident occurred. Individual particles still on the wood were microdissected from the bulk matrix after bulk autoradiography.

Analytical electron microscope studies of size-segregated particles collected during AGASP-II, flights 201?203

Cascade impactor samples were collected over the Alaskan Arctic during the first three research flights of AGASP-II. These samples were analyzed using analytical electron microscopy to determine the morphology, mineralogy and elemental composition of individual particles. For analytical considerations, a typical impactor sample was run for approximately 20 min, thus giving excellent time resolution of discrete events. Samples collected during flights 201 and 202 consisted of stratospheric aerosol and lower-altitude haze samples. Stratospheric samples were characterized by moderate loadings of H2SO4 droplets with relatively few particles of other types. Samples collected in tropospheric haze layers generally exhibited light-to-moderate particle loadings. H2SO4 was again the most prevalent species, with crustal and anthropogenic particles also observed. One sample taken over south-central Alaska near the end of flight 203 showed high concentrations of solid crustal particles, with relatively little associated H2SO4. Giant particles larger than 5 μm were occasionally observed in this aerosol. The composition of this material closely matches that of bulk ash from the Mt. Augustine volcano, which erupted 9–13 days before collection of this sample. This brings forth the possibility that pockets of ash-rich aerosol existed over parts of south and central Alska during the AGASP-II field mission. There is no evidence that these volcanic aerosols were present in the AGASP study area north of the Brooks Range.

Electron microscopy of nanometer particles in fresh water

Nanometer particles, 1-100 nm, in freshwater play an important role to decrease the toxicity of heavy metals toward aquatic organisms by adsorption. They are also known to contribute to sedimentation of heavy metals in estuarine regions. So far, however, little information has been available on the morphology and elemental composition of individual particles. Scanning electron microscopy of particles smaller than 100 nm collected on a membrane filter does not give sufficient information, because of poor resolution in morphology and difficulty in X-ray microanalysis. An analytical electron microscope (AEM), a high-resolution transmission electron microscope (TEM) equipped with an X-ray microanalyzer, can be a powerful tool, although specimen preparation is more difficult. This note describes the usefulness of specimen preparation by centrifugation in the characterization of particles smaller than 100 nm in pond and river waters using the AEM. Quantitative collection has been confirmed with monodispersed gold particles, several nanometers in diameter.

A study of marine aerosols over the Pacific Ocean

Aerosol samples were collected on a Pacific cruise from 47°N to 55°S. Particle morphology, concentrations, and size distributions were analyzed with an electron microscope; elemental compositions of individual particles were determined with an X-ray energy spectrometer; and chemical compositions of bulk samples were measured with an ion chromatograph. Temporal and spatial variations of aerosol physico-chemical characteristics were studied in relation to ocean currents and atmospheric parameters. The results show that number and mass concentrations of primary particles depend mainly on surface wind speeds. However the ratios between the major ions, e.g., Na+, Cl-, and Mg++, are similar to the ratios in seawater regardless of location or meteorological conditions. The concentrations of secondary aerosols, e.g., non-seasalt sulfate, nitrate, and ammonium particles, show maxima at upwelling regions, such as along the California coast, at the Equator, and near the Chatham Rise where ascending motion brings nutrient-riched deep water into the surface layer. The number concentrations of small sulfate particles and large nitrate-coated particles showed diurnal variations with maxima in the early afternoon and minima at night, indicating that the particles are the products of photo-chemical reactions. Their precursor gases, e.g., CH3SCH3, NO, and NH3 are known to be released from seawater in upwelling regions where biological activities thrive.

Rocket Effluent: Its Ice Nucleation Activity and Related Properties

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

Nucleation properties of fly ash in a coal-fired power-plant plume

Airborne aerosol samples were collected on Nuclepore filters in the plume of a coal-fired power plant. Transmission and scanning electron microscopes were used to determine the concentration and size distribution of aerosols and an X-ray energy spectrometer was used to determine the elemental composition of individual particles. It was found that on a mass basis, only about 2% of the fly ash aerosol is water soluble. However, due to surface coating of insoluble fly ash particles with water soluble materials, the number of cloud condensation nuclei in a plume can be enhanced multifold over the background concentration. The passivation of the ice nucleation capability of fly ash can be alleviated by the evaporation of surface-deposited compounds.