Elemental Composition Of Individual Particles Research Articles

Characterization of particle exposure during tunnel excavation by tunnel boring machines.

Tunnel boring machines (TBMs) are used to excavate tunnels in a manner where the rock is constantly penetrated with rotating cutter heads. Fine particles of the rock minerals are thereby generated. Workers on and in the vicinity of the TBM are exposed to particulate matter (PM) consisting of bedrock minerals including α-quartz. Exposure to respirable α-quartz remains a concern because of the respiratory diseases associated with this exposure. The particle size distribution of PM and α-quartz is of special importance because of its influence on adverse health effects, monitoring and control strategies as well as accurate quantification of α-quartz concentrations. The major aim of our study was therefore to investigate the particle size distribution of airborne PM and α-quartz generated during tunnel excavation using TBMs in an area dominated by gneiss, a metamorphic type of rock. Sioutas cascade impactors were used to collect personal samples on 3 separate days. The impactor fractionates the dust in 5 size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations were quantified using X-ray diffraction (XRD) analysis and the NIOSH 7500 method on the 5 size fractions. Other minerals were determined using Rietveld refinement XRD analysis. The size and elemental composition of individual particles were investigated by scanning electron microscopy. The majority of PM mass was collected on the first 3 stages (aerodynamic diameter = 10 to 0.5 µm) of the Sioutas cascade impactor. No observable differences were found for the size distribution of the collected PM and α-quartz for the 3 sampling days nor the various work tasks. However, the α-quartz proportion varied for the 3 sampling days demonstrating a dependence on geology. The collected α-quartz consisted of more particles with sizes below 1 µm than the calibration material, which most likely affected the accuracy of the measured respirable α-quartz concentrations. This potential systematic error is important to keep in mind when analyzing α-quartz from occupational samples. Knowledge of the particle size distribution is also important for control measures, which should target particle sizes that efficiently capture the respirable α-quartz concentration.

Morphological and chemical characterisation of indoor quasi-ultrafine particles

Particles in the nanoscale range have intrinsic physicochemical characteristics that define their interaction with the human body and ultimately their toxicity. Whilst research has focused on engineered nanomaterials or ambient ultrafine particles, little is known about the morphology, size and elemental composition of particles in the nanoscale range collected in indoor environments, where humans spend the longest time. This study aims to characterise the physicochemical properties of quasi-ultrafine particles (qUFP), with an aerodynamic diameter <250 nm, collected with a Sioutas impactor from 5 indoor environments (3 homes and 2 offices). Morphology, size and elemental composition of individual particles were imaged using a Transmission Electron Microscope coupled with X-ray energy dispersive spectroscopy. Most of the single particles and their aggregates were of irregular shapes, and some fibrous rods, elongated rods, spheres and hexagons were also observed. ImageJ software was used to analyse the surface area, roundness and circularity of the particles, as well as individual particle diameter for the spherical particles. For the non-spherical shaped particle, the particles were manually measured to characterise the maximum Feret diameter. Particle main dimensions (i.e. diameter for spheroids and maximum Feret diameter for irregular particles) ranged from 35 ± 59 nm to 103 ± 160 nm. Shapes for non-spherical particles were assigned by visual description. Si, Fe and S were found in nanoparticles from all indoor locations. Other abundant constituents were K, Cr, Na, Ca, Cl found in 60–80% of locations. Minor constituents of indoor nanoparticles were Cu, Sn, Ti, Mo, Al, P, Be, F, Zn, Rb, Pb, Mn and Co. Sources were related to indoor emissions, e.g. printers, stainless-steel tools, electronics, cooking, house chores, particle re-suspension, aerosol and cleaning products as well as to penetration of outdoor nanoparticles from vehicular emissions, soil and secondary aerosols. Detailed investigation of the physicochemical properties of these particles can help understand their associated hazard and their fate in the human body.

Direct Measurement of Microplastics by Carbon Detection via Single Particle ICP-TOFMS in Complex Aqueous Suspensions.

Multiple analytical techniques to measure microplastics (MPs) in complex environmental matrices are currently under development, and which is most suited often depends on the aim(s) of the research question and the experimental design. Here, we further broaden the suite of possible techniques which can directly detect MPs in suspension while differentiating the carbon contained in MPs from other natural particles and dissolved organic carbon (DOC). Single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) is well suited to measuring particles at trace concentrations, and the use of ICP time-of-flight-MS (ICP-TOFMS) allows one to simultaneously monitor the entire elemental spectrum to assess the full elemental composition of individual particles through developing elemental fingerprints. Because carbon is not detected in a standard operation mode with icp TOF, a dedicated optimization was necessary. Subsequently, to assess the feasibility of monitoring 12C particle pulses for the detection of MPs in more complex natural waters, two proof-of-principle studies were performed to measure MPs in waters with environmentally relevant DOC backgrounds (≤20 mg/L) and in the presence of other carbon containing particles, here, algae. Elevated DOC concentrations did not impact the enumeration of particles in suspension, and individual MPs, single algae, and aggregates of MPs and algae were clearly distinguished. The simultaneous identification of different analytes of interest allows for multiplexed sp-ICP-TOFMS experiments utilizing elemental fingerprinting of particles and is a step forward in quantifying MPs in aqueous environmental samples.

Using nondestructive techniques in mineral carbonation for understanding reaction fundamentals

Mineral carbonation of alkaline earth metals is the conversion of carbon dioxide, in gaseous form or dissolved in water, to form solid inorganic carbonates. Alkaline earth metals can be derived from natural minerals, waste residues, or brines. Calcium and magnesium are the two most abundant of these metals, which when carbonated form a variety of calcium and magnesium carbonates of different mineral compositions and crystal structures. Determining inorganic carbon (IC) content of carbonation solid products with high precision is an essential requisite to quantify the amount of carbon dioxide sequestered by a given process at a given reaction time. It also enables understanding fundamental phenomena about the reactions, including the reaction rate, conversion limitations, and the mineral composition of carbonation products and by-products. The most conventional methods to determine IC content utilize destructive techniques based on acid decomposition (e.g. calcimeter) and thermal decomposition (e.g. thermogravimetric analyzer). The main disadvantage of these methods includes chemical usage, long measurement time, overestimation of IC, and limited ability to differentiate the various mineral forms of carbonates. In this regard, nondestructive techniques (NDT) constitute a valuable alternative to the conventional method for IC determination and carbonates characterization; these include spectroscopic methods (NIR, MIR), X-ray spectroscopy (XRD, XRF, XCT); and microscopic methods (SEM-EDS, TEM, RLM, EPMA). While infrared spectroscopy can be used to quantitatively identify carbonate spectral bands, X-ray diffraction quantitatively identifies the presence of specific crystalline carbonate phases. Elemental chemical information is provided by X-ray fluorescence, and microstructure analysis is done using electron probe microanalysis and micro-tomography. SEM provides visualization of crystal and particle size and morphology, while energy dispersive spectroscopy is used to inspect elemental composition of individual particles or intra-particle layers and grains. This paper presents a critical comparative analysis of the use of these NDT in determining IC content and carbonate composition. Improved understanding of the advantages, limitations, and applicability of each method can enable the development of standard protocols for characterization of carbonation products, which is especially required for carbon sequestration accounting in view of climate change mitigation.

Microscopic morphology and elemental composition of atmospheric particles from seven micro-environments in Xi’an

This paper characterizes the morphological and elemental compositions of individual particles in seven micro-environments of Xi’an. Atmospheric particulate matter samples were collected at one suburban site (Duling Park (DL)), three urban sites (roadside site (RS), clear days (CD), dusty days (DD)) and three indoor sites (hot pot (HP), barbecue (BBQ), hospital (HO)) during March–April in 2017. A total of 469 particles were analysed by a scanning electron microscopy with an energy dispersive X-ray spectroscopy. Seven types of particles were observed, including sulphate particles, iron oxide particles, dust mineral particles, soot, organic aerosols, silicon–aluminium (Si–Al)-rich fly ash and biological particles. Soot accounted for 22% in BBQ, indicating an effect of BBQ coal burning. Sulphate particles were found in high abundance (14–15%) in HP and HO samples, consistent with the occurrence of secondary chemical reactions. Organic aerosols accounted for 13% in HO, 20% in HP and BBQ samples due to cooking of food and human factors. Comparison of samples in indoor and outdoor environments showed that the external transmission of dust mineral particles and Fe oxide particles played a key role in indoor levels. The microscopic analysis also demonstrated that the particles in Xi’an were highly distributed with fine particles (less than 3 µm) and that the morphology of fine particles tended to be spherical.

A model based two-stage classifier for airborne particles analyzed with Computer Controlled Scanning Electron Microscopy

Computer controlled scanning electron microscopy (CCSEM) is a widely-used method for single airborne particle analysis. It produces extensive chemical and morphological data sets, whose processing and interpretation can be very time consuming. We propose an automated two-stage particle classification procedure based on elemental compositions of individual particles. A rule-based classifier is applied in the first stage to form the main classes consisting of particles containing the same elements. Only elements with concentrations above a threshold of 5 wt% are considered. In the second stage, data of each main class are isometrically log-ratio transformed and then clustered into subclasses, using a robust, model-based method. Single particles which are too far away from any more densely populated region are excluded during training, preventing these particles from distorting the definition of the sufficiently populated subclasses. The classifier was trained with over 55,000 single particles from 83 samples of manifold environments, resulting in 227 main classes and 465 subclasses in total. All these classes are checked manually by inspecting the ternary plot matrix of each main class. Regardless of the size of training data, some particles might belong to still undefined classes. Therefore, a classifier was chosen which can declare particles as unknown when they are too far away from all classes defined during training.

Aerosol composition and microstructure in the smoky atmosphere of Moscow during the August 2010 extreme wildfires

This is a comprehensive study of the physicochemical characterization of multicomponent aerosols in the smoky atmosphere of Moscow during the extreme wildfires of August 2010 and against the background atmosphere of August 2011. Thermal–optical analysis, liquid and ion chromatography, IR spectroscopy, and electron microscopy were used to determine the organic content (OC) and elemental content (EC) of carbon, organic/inorganic and ionic compounds, and biomass burning markers (anhydrosaccharides and the potassium ion) and study the morphology and elemental composition of individual particles. It has been shown that the fires are characterized by an increased OC/EC ratio and high concentrations of ammonium, potassium, and sulfate ions in correlation with an increased content of levoglucosan as a marker of biomass burning. The organic compounds containing carbonyl groups point to the process of photochemical aging and the formation of secondary organic aerosols in the urban atmosphere when aerosols are emitted from forest fires. A cluster analysis of individual particles has indicated that when the smokiest atmosphere is characterized by prevailing soot/tar ball particles, which are smoke-emission micromarkers.

Synthesis, structural and magnetic characterization of soft magnetic nanocrystalline ternary FeNiCo particles

The present study focuses on the synthesis, microstructural and magnetic properties of ternary FeNiCo nanoparticles. Nanocrystalline ternary FeNiCo particles were synthesized via hydrogen reduction assisted ultrasonic spray pyrolysis method in single step. The effect of precursor concentration on the morphology and the size of particles was investigated. The syntheses were performed at 800°C. Structure, morphology and magnetic properties of the as-prepared products were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) studies. Scherer calculation revealed that crystallite size of the ternary particles ranged between 36 and 60nm. SEM and TEM investigations showed that the particle size was strongly influenced by the precursor concentration and Fe, Ni, Co elemental composition of individual particles was homogeneous. Finally, the soft magnetic properties of the particles were observed to be a function of their size.

Classification and chemical compositions of individual particles at an eastern marginal site of Tibetan Plateau

Aerosol particles at Shangri-La, an eastern marginal site of Tibetan Plateau, were collected in July and August 2011. Morphologies and elemental compositions of individual particles were investigated through transmission electron microscopy coupled with energy dispersive X-ray spectroscopy. More than 14 elements were detected in the aerosol particles, and S were detected in more than 70% of the 292 analyzed particles. Six morphological types of individual particles were identified: soot, fly ash, complex secondary particles, crustal minerals, organic particles, and metal particles. The aerosol particles mainly comprised mineral particles (36.02%) and complex secondary particles (30.73%), followed by organic particles (17.38%), soot (8.06%), fly ash (6.08%), and metal particles (1.01%). The diameters of fly ash, soot, and metal particles were less than 2 μm. Approximately 81% of the particles were internally or externally mixed with two or more aerosol components from different sources. Soot, fly ash, organic, and fine mineral particles were commonly internally mixed with S-rich particles. Mineral particles tended to commonly associate with visible coatings, probably formed through chemical reactions on the surface of the particles. Back-trajectories revealed that air mass arriving at Shangri-La were transported from Northeast Burma, a region of the Indian subcontinent.

THE STUDY OF DUST FORMATION DURING ARC MELTING OF ZINC-COATED STEEL

The formation of dust was studied when plasma arc heating of galvanized steel in argon atmosphere at amperage from 170 – 190 A, argon consumption – 0.06 m 3 /h, pressure in the furnace – 0.1 MPa. It was found that zinc is almost completely evaporated during the first 30 seconds of melting. The structure of collected zinc containing dust is not homogenous; there are particles of different shapes (spherical, needle, spherical and filmy), sizes and composition. The elemental composition of individual particles of formed dust was analyzed at iCAP 6300 spectrometer (Thermo Electron, USA), on the basis of which their oxide composition was evaluated using TERRA program. It was shown that the dust is composed of particles, consisting of ZnO, Fe 3 O 4 , pure iron and carbon. Based on the results of the work it was concluded that during plasma-smelting of galvanized steel zinc containing dust can be traped separately from the remaining dust in the initial period of melting.

Healthy environment — indoor air quality of Brazilian elementary schools nearby petrochemical industry

The mitigation of pollution released to the environment originating from the industrial sector has been the aim of all policy-makers and its importance is evident if the adverse health effects on the world population are considered. Although this concern is controversial, petroleum refinery has been linked to some adverse health effects for people living nearby. Apart from home, school is the most important indoor environment for children and there is increasing concern about the school environment and its impact on health, also in developing countries where the prevalence of pollution is higher. As most of the children spend more than 40% of their time in schools, it is critical to evaluate the pollution level in such environment. In the metropolitan region of Curitiba, South Brazil, five schools nearby industries and highways with high density traffic, were selected to characterize the aerosol and gaseous compounds indoor and outdoor of the classrooms, during 2009–2011. Size segregated aerosol samples were collected for analyses of bulk and single particle elemental profiles. They were analyzed by electron probe X-ray micro-analysis (EPXMA), and by energy-dispersive X-ray fluorescence (EDXRF), to investigate the elemental composition of individual particles and bulk samples. The concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX); NO2; SO2; acetic acid; and formic acid were assessed indoor and outdoor using passive diffusion tubes. BTEX were analyzed by GC–MS and other collected gasses by ion chromatography. Individual exposition of BTEX was assessed by personal passive diffusion tubes. Results are interpreted separately and as a whole with the specific aim of identifying compounds that could affect the health of the scholars. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the children's respiratory systems were calculated, revealing the deposition of particles at extrathoracic, tracheobronchial and pulmonary levels.

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The mitigation of pollution released to the environment originating from the industrial sector has been the aim of all policy-makers and its importance is evident if the adverse health effects on the world population are considered. Although this concern is controversial, petroleum refinery has been linked to some adverse health effects for people living nearby. Apart from home, school is the most important indoor environment for children and there is increasing concern about the school environment and its impact on health, also in developing countries where the prevalence of pollution is higher. As most of the children spend more than 40% of their time in schools, it is critical to evaluate the pollution level in such environment. In the metropolitan region of Curitiba, South Brazil, five schools nearby industries and highways with high density traffic, were selected to characterize the aerosol and gaseous compounds indoor and outdoor of the classrooms, during 2009–2011. Size segregated aerosol samples were collected for analyses of bulk and single particle elemental profiles. They were analyzed by electron probe X-ray micro-analysis (EPXMA), and by energy-dispersive X-ray fluorescence (EDXRF), to investigate the elemental composition of individual particles and bulk samples. The concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX); NO2; SO2; acetic acid; and formic acid were assessed indoor and outdoor using passive diffusion tubes. BTEX were analyzed by GC–MS and other collected gasses by ion chromatography. Individual exposition of BTEX was assessed by personal passive diffusion tubes. Results are interpreted separately and as a whole with the specific aim of identifying compounds that could affect the health of the scholars. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the children's respiratory systems were calculated, revealing the deposition of particles at extrathoracic, tracheobronchial and pulmonary levels.

Chemical and morphological characterization of PM2.5 collected during MILAGRO campaign using scanning electron microscopy

PM2.5 were collected in March 2006 during the MILAGRO campaign (Megacities Initiative: Local and Global Research Observations) carried out in the northern region of the Mexico City Metropolitan Area (MCMA), in order to realize an individual characterization of particulate matter through scanning electron microscopy coupled with an energy–dispersive X–Ray analyzer (SEM–EDX), acquiring information from around 6 000 particles about their morphology, size and superficial chemical composition. Measurements of the aerosol were obtained at a site located in the northern part of Mexico City (T0) and also at a site located 30km northeast (T1) in four time intervals 6:00 – 9:00; 11:00 – 14:00; 16:00 – 19:00 and 21:00 – 0:00hrs. Employing backscattered electron detector (BSD) anthropogenic phases were analyzed with the EDX and elemental composition of individual particles showed mainly elemental composition of Fe–O (24% relative abundance) with spherical morphology congruent to emissions from metal–mechanic industrial process and soil re–suspension. Twenty percent of the aerosol was “Pb–rich” particles identified as agglomerations of nanometric spheres of individual size distributions among 1.0 – 600nm and they are related to high temperature industrial emissions. The “Ba– rich” particles (16%) presented chemical associations of Ba–S–O and irregular morphologies and they were related to emissions from the mineral phase of barite that constitutes the asbestos of the automobile pieces. “C–rich” group was the fourth most abundant (12%) one with predominant morphology corresponds to nanometric spheres (between 600 and 800nm) of compact and continuous surface, this kind of particles are mainly related to vehicle exhaust emissions and their temporal distribution presented a clear decrease during weekends when vehicle traffic is reduced on the MCMA. Elements like Ca, Zn, Cu, Sr, Sn, Al, Sb, Na and W were also detected in less relative abundance (28% of the total), and their individual morphology and possible source emissions are described.

Nanoparticle chemical composition and diurnal dependence at the CalNex Los Angeles ground site

The Nano Aerosol Mass Spectrometer (NAMS) was deployed to the California Nexus Los Angeles ground site in Pasadena, California during May–June 2010 to study nanoparticles in the 20–25 nm size range. NAMS gives a quantitative measure of the elemental composition of individual particles, and molecular apportionment of the elemental data allows the O/C mole ratio of carbonaceous matter in each particle to be determined. Abrupt increases in nanoparticle number concentration were observed in the afternoon on sunny days, and coincided with a shift in the wind direction from the southeast to the southwest. Nanoparticles analyzed during these time periods were found to contain enhanced levels of sulfur and silicon relative to particles analyzed earlier in the day, and the O/C ratios of carbonaceous matter changed from a distribution dominated by primary motor vehicle emissions (O/C ratio &lt; 0.25) to one dominated by “fresh” secondary organic aerosol (O/C ratio between 0.25 and 0.65). The wind direction and chemical composition dependencies suggest that the afternoon increase in number concentration originated from motor vehicle emissions in the downtown Los Angeles area that were photochemically processed during transport to the measurement site. It is likely that photochemical processing led to both a change in the composition of preexisting particles and to the formation of new particles.

Microscopic morphology and size distribution of particles in PM2.5 of Guangzhou City

Samples of airborne PM2.5 particles in Guangzhou urban area were collected during the autumn of 2006 and the spring of 2007. The morphologies and elemental compositions of individual particles were determined by Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectrometer (SEM-EDX). The obtained images were further analyzed for size distribution by an image analysis system. Based on the morphology, particles in PM2.5 were classified into four groups: soot aggregates, minerals, fly ash and others. The amount of soot aggregates and minerals were higher than that of fly ashes. The distributions of particles by number and size in two seasons were bimodal with 90% less than 1.0 μm in diameter. The primary peak from the autumn samples was in the size range of 0.4 ~ 0.5 μm, and 0.3 ~ 0.4 μm for the spring samples. More soot aggregates (36.1%) and minerals (61.5%) were found than fly ash (2.4%) in autumn, but soot aggregates (89.9%) was the dominant particle type in spring. The size distribution of particles according to the volume was generally opposite to that according to the number. Particles less than 1.0 μm were as high as 89.5% in number but contributed only 18.9% in volume, indicating that fine particles contributed relatively little in volume although existing in large numbers.

Assessment of aerosol particles within the Rubens' House Museum in Antwerp, Belgium

AbstractThe majority of researchers, conservators and curators recognise that atmospheric pollution is one of the major threats to works of art. In principle, all atmospheric particles, when deposited onto art objects can be considered harmful because of their potential in causing deterioration. Moreover, under certain conditions, particulate matter can induce and intensify surface damage, particularly because of its potential to serve as centre for moisture condensation and adsorbent of gaseous pollutants. To investigate the potential harm that these particles can cause, comprehensive characterisation of the particulate matter is necessary. Particulate matter was collected at the Rubens' House Museum in Antwerp, Belgium, where a unique exhibit of the paintings and living quarters of Peter Paul Rubens (1577–1640) are seen. Size segregated aerosol samples were collected for analyses of bulk and single particle elemental and molecular compositions. They were analysed by electron probe micro‐analysis, utilising facilities for low‐Z element determination, and by energy‐dispersive x‐ray fluorescence, to investigate the elemental composition of individual particles and bulk samples, and by micro Raman spectrometry, to elucidate the molecular composition. Results are interpreted separately and as a whole with the specific aim of identifying compounds that could contribute to the chemical reactions taking place on the surfaces of artefacts and which could potentially cause degradation of the objects. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Chemistry of Particle Inception and Growth during α-Pinene Ozonolysis

A flow-tube reactor was used to study the formation of particles from alpha-pinene ozonation. Particle phase products formed within the first 3-22 s of reaction were analyzed online using a scanning mobility particle sizer and two particle mass spectrometers. The first, a photoionization aerosol mass spectrometer (PIAMS), was used to determine the molecular composition of nascent particles between 30 and 50 nm in diameter. The second, a nano-aerosol mass spectrometer (NAMS), was used to determine the elemental composition of individual particles from 50 nm to below 10 nm in diameter. Molecular composition measurements with PIAMS confirm that both the stabilized Criegee intermediate and hydroperoxide channels of alpha-pinene ozonolysis are operative. However, these channels alone cannot explain the high oxygen content of the particles measured with NAMS. The carbon-to-oxygen mole ratios of suspected nucleating agents are in the range of 2.25-4.0, while the measured ratios are from 1.9 for 9 nm particles to 2.5 and 2.7 for 30 and 50 nm particles, respectively. The large oxygen content may arise by cocondensation of small oxygenated molecules such as water or multistep reactions with ozone, water, or other species that produce highly oxygenated macromolecules. In either case, the increasing ratio with increasing particle size suggests that the aerosol becomes less polar with time.

Size-Resolved Kinetic Measurements of Aluminum Nanoparticle Oxidation with Single Particle Mass Spectrometry

Aluminum nanoparticles are being considered as a possible fuel in advanced energetic materials application. Of considerable interest therefore is a knowledge of just how reactive these materials are, and what the effect of size on reactivity is. In this paper we describe results of size resolved oxidation rate using a recently developed quantitative single particle mass spectrometer (SPMS). Aluminum nanoparticles used were either generated by DC Arc discharge or laser ablation, or by use of commercial aluminum nanopowders. These particles were oxidized in an aerosol flow reactor in air for specified various temperatures (25-1100 degrees C), and subsequently sampled by the SPMS. The mass spectra obtained were used to quantitatively determine the elemental composition of individual particles and their size. We found that the reactivity of aluminum nanoparticles is enhanced with decreasing primary particle size. Aluminum nanoparticles produced from the DC Arc, which produced the smallest primary particle size (approximately 19 nm), were found to be the most reactive (approximately 68% aluminum nanoparticles completely oxidized to aluminum oxide at 900 degrees C). In contrast, nanopowders with primary particle size greater than approximately 50 nm were not fully oxidized even at 1100 degrees C (approximately 4%). The absolute rates observed were found to be consistent with an oxide diffusion controlled rate-limiting step. We also determined the size-dependent diffusion-limited rate constants and Arrehenius parameters (activation energy and pre-exponential factor). We found that as the particle size decreases, the rate constant increases and the activation energy decreases. This work provides a quantification of the known pyrophoric nature of fine metal particles.

A case study of the single and size-resolved particles in roadway tunnel in Seoul, Korea

Abstract Particle sampling was conducted at the center of Buk-Ak tunnel, which is one of heavily polluted tunnels in Seoul, in October 2000. The sampling equipments consist of a 2-stage filter pack sampler and an Andersen impactor sampler. Micro-particle induced X-ray emission (PIXE) was applied to determine the elemental composition of individual particles (>1.2 μm). The thermal/optical reflectance (TOR ® ) method was also employed in analyzing of EC and OC. Mass concentrations of fine and coarse particles are 177 and 40 μg m −3 , respectively. The most important contributor to particle mass concentration in the present study is carbonaceous components. Most of the individual particles are found to be internally mixed with soil-derived and trace elemental components.

Measurement of fine particulate matter using electron microscopy techniques

Ambient fine particulate matter, defined as material with an aerodynamic diameter less than or equal to 2.5 μm (PM 2.5), comprises a broad range of primary and secondary particles that are dispersed through the atmosphere from a variety of sources. Attention has recently shifted to investigating ambient PM 2.5 because fine particles are thought to have a greater influence on health effects. Of particular interest are sources of fossil fuel combustion because they have been hypothesized as potentially contributing to the observed link between atmospheric particulate matter and health effects. Current studies are focused on the use of multiple analytical techniques to assist in the characterization of particulate matter to gain a better understanding of the relationship between anthropogenic emission sources and ambient PM 2.5. Electron microscopy techniques are being employed to provide information on the size, morphology, and elemental composition of individual particles. Individual particle data offers the potential to more specifically identify and quantify sources of particulate matter contributing to ambient air quality. However, electron microscopy has not been widely utilized in air quality studies because of the difficulties associated with collecting a sample that is well suited for individual particle analysis. Recent improvements in sampling technology, specifically the speciation sampler, permit collection of samples that are more amenable for electron microscopy analysis. This paper discusses the application of electron microscopy in environmental studies for individual particle analysis using scanning electron microscopy (SEM), computer-controlled scanning electron microscopy (CCSEM), and transmission electron microscopy (TEM) techniques. The paper also addresses managing the difficulties associated with the characterization of fine particulate matter using electron microscopy due to substrate interference and describes the benefits of sample collection with speciation samplers.