Individual Particle Analysis Research Articles

The influence of collecting substrates on the single-particle characterization of real atmospheric aerosols

This work investigated the influence of three different collecting substrate materials, Ag and Al foils and grids for transmission electron microscopy (TEM grid), on the morphological and chemical compositional analysis of individual particles collected at an underground shopping area in Seoul, Korea. The feasibility of using each substrate in a quantitative single-particle analysis was evaluated by comparing particle morphologies, X-ray spectra, and elemental quantification results obtained for the three substrates. The morphologies and the quality of X-ray spectra for crystalline mineral particles were very similar among the three substrates. However, water-soluble, CNO-rich aerosols showed different morphologies among the three substrates, mainly due to the differences in the hygroscopic properties of the substrates. The quality of the X-ray spectra of the CNO-rich particles was optimal when collected on the TEM grid. To reliably assess the characteristic X-rays of the CNO-rich particles collected on the Ag and Al foils, appropriate data analysis had to be applied. Especially, the X-ray spectra of the CNO-rich particles collected on Al foil required a new background subtraction procedure. The overall relative abundances of the chemical species, obtained from the three collecting substrates, were in good agreement with each other and single-particle characterization of the real aerosol sample was feasible on the different substrates. However, the TEM grid substrate was the most appropriate for single-particle analysis of the water-soluble CNO-rich particles as: (i) it retains the original morphology and size of the particles, (ii) it allows high contrast in the backscattered electron image (BSEI) mode, and (iii) it provides a high peak-to-background ratio (P/B) with small and correctable interferences in the X-ray spectra.

Composition distributions in FePt(Au) nanoparticles

Ternary alloy FePt(Au) nanoparticles were prepared by the co-reduction of platinum(II) acetylacetonate and gold(III) acetate and the thermal decomposition of iron pentacarbonyl in hot phenyl ether in the presence of oleic acid and oleylamine ligands. This gave spherical particles with an average diameter of 4.4 nm with a range of diameters from approximately 1.6–9 nm. The as-synthesized particles had a solid solution, face-centered-cubic structure. Though the average composition of the particles was Fe44Pt45Au11, individual particle analysis by Scanning Transmission Electron Microscopy–X-ray Energy Dispersive Spectroscopy showed a broad distribution in composition. In general, smaller-sized particles tended to have a lower amount of Au as compared to larger-sized particles. As the Au content increased, the ratio of Fe/Pt widened.

Turbidity Model for Ashokan Reservoir, New York: Case Study

Terrigenous inorganic particles delivered during runoff events cause problems of high turbidity in many lakes and reservoirs. A turbidity model, composed of a two-dimensional hydrothermal/transport submodel and a turbidity submodel, is developed and tested for Ashokan Reservoir, New York, that experiences elevated turbidity levels following runoff events. A robotic monitoring network, rapid profiling instrumentation, and individual particle analyses are used to support the modeling, by specifying turbidity loads and in-reservoir patterns and features of the particles that guided representation of settling. The turbidity-causing particles are clay minerals, 1–10 μm in diameter. The hydrothermal/transport submodel that serves as the physical framework for the overall model, was separately validated for a 13-year period. The turbidity submodel considered three particle-size/settling velocity classes of turbidity, consistent with the independent individual particle characterizations. Robust performance is dem...

Quantitative elemental analysis of individual particles with the use of micro‐beam X‐ray fluorescence method and Monte Carlo simulation

AbstractThe aim of the work was to develop a Monte Carlo (MC) method and combine it with micro‐beam X‐ray fluorescence (XRF) technique for determination of chemical composition of individual particles. A collection of glass micro‐spheres, made of NIST (National Institute of Standards and Technoly) K3089 material of known chemical composition, with diameters in the range of 25–45 µm was investigated. The micro‐spheres were measured in a scanning micro‐beam XRF spectrometer utilising X‐ray tube as a source of primary radiation. Results obtained for low Z elements showed high dependence on particle size. It was found that the root mean square of concentration uncertainty, for the all elements present in the particle, increases with growing sample size. More accurate results were obtained for high Z elements such as Fe–Pb, as compared to others. The elemental percentage uncertainty did not exceed 14% for any particular sample and 6% for the whole group of the measured micro‐spheres as an average. Results obtained by the Monte Carlo method were compared with other analytical approaches. Copyright © 2009 John Wiley & Sons, Ltd.

On-Line Chemical Analysis of Individual Alkali-Containing Aerosol Particles by Surface Ionization Combined with Time-of-Flight Mass Spectrometry

An aerosol mass spectrometer for measurements of the alkali metal content in individual submicron aerosol particles is presented. The instrument combines surface ionization of individual particles on a hot platinum surface with orthogonal acceleration time-of-flight mass spectrometry. The instrument simultaneously provides the content of different alkali metal elements in single particles with high sensitivity. The instrument is characterized in laboratory experiments, and determination of the alkali metal content is demonstrated for particle diameters of 50–500 nm. The technique is demonstrated in ambient air measurements at an urban background site, and sea spray particles and particles originating from biomass burning are identified based on their content of sodium and potassium. Possible further improvements and applications of the technique are discussed.

Characterizations of minerogenic particles in support of modeling light scattering in Lake Superior through a two‐component approach

The role of suspended minerogenic particles in light scattering in eastern Lake Superior and Keweenaw Bay (11 sites) during July of 2006 was evaluated with an individual particle analysis technique (scanning electron microscopy interfaced with automated image and X‐ray analyses, SAX), along with bulk measurements of particulate scattering and backscattering coefficients (bp and bbp) and chlorophyll a concentration ([Chl]). SAX measurements provided information on light‐scattering attributes of minerogenic particles, including chemical composition and particle size distribution (PSD). The data were used in Mie theory calculations for estimations of minerogenic scattering and backscattering coefficients (bm and bb,m). The bay had higher concentrations of minerogenic particles and higher values of bm, bb,m, bbp, and the backscattering ratio (bbp : bp) than the pelagic sites. Minerogenic scattering was primarily attributable to clay mineral particles in the size range of 1‐10 mm. The PSDs deviated from the (Junge) pattern of monotonic increase of particle numbers with decreasing particle size. The estimates of bm and bb,m combined with those of organic particulate components, as represented by empirical Case 1 bio‐optical models, showed reasonably good closure with bp and bbp, supporting the credibility of the SAX‐Mie approach. Variations in the bbp : bp ratio are strongly related to spatial differences in the relative contributions of phytoplankton vs. minerogenic particles to scattering, with higher values observed where the minerogenic component is more important. SAX can advance the understanding of optical variability by establishing the contributions of well‐defined minerogenic constituents that strongly influence optical properties.

Ion beam microanalysis of individual aerosol particles originating from Saharan dust episodes observed in Debrecen, Hungary

Approximately 50 episodes of Saharan dust intrusion have been observed by PIXE in the atmosphere of Debrecen, Hungary since 1991 [I. Borbély-Kiss, Á.Z. Kiss, E Koltay, Gy. Szabó, L. Bozó, J. Aerosol Sci. 35 (2004) 1205]. In order to separate dust particles of Saharan origin from local sources, and to follow the formation, ageing and evolution of particles originating from long range transport processes, individual dust particle analysis was carried out on the Debrecen ion microprobe. The samples were collected on polycarbonate filters at a rural site 50 km from Debrecen during the Saharan sand plume in November 1996. Quantitative elemental concentrations for elements Z ⩾ 6 were determined using PIXE–PIXE and STIM analytical methods. Saharan dust particles were selected on the base of characteristic elemental ratios like Ti/Ca, Ti/Fe and Al/Ca. Major and trace element content and possible chemical composition of the selected particles were determined. Single particle analysis of Saharan dust particles will lead to a better understanding of their formation process during transport.

Spectral measurements of large particles by flow cytometry

Flow cytometers designed to analyze large particles are enabling new applications in biology and chemistry. Similarly, flow spectroscopy approaches are extending the capabilities of the flow cytometry platform. Here, we report on the adaptation of a commercial large particle analyzer to measure fluorescence and Raman spectra of individual particles at high speeds. We modified a Union Biometrica COPAS Plus instrument to allow red excitation and optical fiber-based light collection and spectral analysis using a spectrograph and CCD array detector. These modifications did not compromise the ability of the instrument to resolve different sized particles based on their extinction and time of flight signals. The modified instrument has the sensitivity and spectral resolution to measure the fluorescence and Raman signals from individual particles with signal integration times of 10 usec. The high speed spectral analysis of individual particles in flow will enable new applications in biological and chemical analyses.

A Method for Source Apportionment of Lead in Fine Particulate Matter Based on Individual Particle Analysis Using a Synchrotron X-ray Fluorescence Microprobe

A source apportionment method based on individual particle analysis carried out using a synchrotron X-ray fluorescence microprobe was developed for source apportionment of lead in fine particulate matter. Mass contributions of every emission source were obtained by intensity ratios of the characteristic X-ray spectrum of lead in individual airborne particles. The validity of the method was evaluated. The uncertainty of the source apportionment was estimated, which was within 10% in this work. The method was applied to the apportionment of lead in fine airborne particles of Shanghai, indicating that the method has a finer performance for source apportionment.

An analysis of individual Asian-dust particles collected at Higashiosaka, Japan in 2007 and 2008

An analysis of individual Asian-dust particles collected at Higashiosaka, Japan in 2007 and 2008

Aerosol Particles from Dried Salt-Lakes and Saline Soils Carried on Dust Storms over Beijing

Characteristics of individual particles from a super dust storm (DS) on 20 March 2002, and those of non dust storm aerosols for Beijing (NDS) and Duolun (DL) (a desert area) are deter mined using a variety of methods. In China, typically the source of aerosols in dust storms is thought to be deserts with aluminosilicates being the main constituent particles; how ever, this does not reflect a complete analysis with our evidence indicating potential alternate dust sources along the storm's transport path. Individual particle analysis of aero sols collected from a super dust storm on 20 March 2002 in Beijing shows that among all the 14 elements measured, only S and C1 have remark able positive correlation. 82.5% of all particles measured contained both S and C1, and the relative mass percent age of S and C1 in these particles is much higher than the aver age of all particles. 62.0% of all particles contained S, C1, and Na, in which the concentration of Na is 1.4 times higher than average. PMF (Positive Matrix Factorization) analysis indicates that NaC1 and Na2SO4 are major components of these particles with S and C1 showing significant positive correlation. More over, SO4(superscript 2-) and Cl(superscript -) also show significant positive correlation in bulk aerosol analysis. XPS (X-ray Photoelectron Spectroscopy) analysis of the surface of aerosols demonstrates that concentrations of Na and S on particles from the dust storm are higher than those from non-dust storm particles in Beijing and also for particles from. It is very likely that particles enriched with S, C1, and Na is from the surface soils of dried salt-lakes and saline soils enriched with chloride and sulfate. This evidence demonstrates that besides deserts, surface soils from dry salt-lakes and saline soils of arid and semi-arid areas are also sources of particulates in dust storms over Beijing.

Element and mineral characterization of dust emission from the saline land at Songnen Plain, Northeastern China

Recent observations of Asian dust storms show an eastern expansion of the source area to degraded lands, where dust emissions have been little studied. The dust concentrations over the saline land of the western Songnen Plain (SSL), Northeastern China, are circumstantially higher than those from the northwestern Chinese deserts. These concentrations are sensitive to the surface soil conditions and wind velocity on the ground. The dust samples collected during dust storm events on the SSL contain abundant Na, Mg, Al, K, Ca, Fe and Ti, as well as toxic elements such as Cu, V, Zn and Ba. Individual particle analysis reveals that fine saline particles (< 10 microm in diameter) on the saline land, consisting largely of carbonate, halite and sulfate together with lithogenic minerals such as SiO2 and aluminosilicate, are eventually uplifted during the interval from spring to autumn. The predominantly fine saline particles uplifted from the SSL are likely transported eastward by the winter monsoon circulation and westerlies. Recent degradation of saline lands in Northeastern China would not only increase the frequency of dust storm events in the downwind area, but also might change the chemical composition of the Asian dust emissions.

The Case Study on Elemental Analyses of Asian Dust Particles by Using an Analytical Scanning Electron Microscope

The individual particle analyses of suspended particulate matter (SPM:particles less than 10μm in size) collected on tape filters during April 17-18, 2006, in Kawasaki, Japan, were carried out. The chemical elements present in aerosol particles were investigated by using a scanning electron microscope with an energy-dispersive X-ray spectrometer. The fraction of chemical elements detected in the particles collected on April 18, 2006, except for S, was in good agreement with that in Asian dust particles from the Loess Plateau, China. S was not detected in Asian dust particles but was detected in the particles collected on April 18, 2006. Therefore, it was concluded that the particles collected on April 18, 2006, in Kawasaki were Asian dust particles transported from the Asian continent, and the absorption of SO2 or the coagulation of sulfate occurred during the transportation of Asian dust particles.

Elemental and individual particle analysis of atmospheric aerosols from high Himalayas

Atmospheric aerosols were collected during the scientific expedition to Mt. Qomolangma (Everest) in May-June, 2005. The elemental concentrations of the aerosols were determined by inductively coupled plasma mass spectrometry. This yielded data for the concentration of 14 elements: Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb. The mean elemental concentrations were generally comparable with those from central Asia and the Arctic, while much higher than those from Antarctic. Size, morphology, and chemical composition of 900 individual aerosol particles were determined by scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on morphology and elemental composition, the particles were clustered into eight groups: soot (8%), tar ball (3%), alumosilicates/silica (55%), calcium sulfate (16%), Ca/Mg carbonate (2%), Fe/Ti-rich particles (3%), Pb-rich particles (1%), and biological particles (12%). The sampling site, located at 6,520 m in the Himalayas, is particularly remote and located at high altitude. Nonetheless, high aerosol enrichment factors for copper, chromium, lead, nickel, vanadium, and zinc all suggest the influence of long-range transported pollution, while enrichment in calcium and the presence of alumino-silicates in individual particle analyses indicates a distinct mineral dust influence. The backward air mass trajectories showed that the northwestern part of India may contribute to the atmospheric aerosol in the central high Himalayas.

Chemical composition and morphology of individual aerosol particles from a CARIBIC flight at 10 km altitude between 50°N and 30°S

Analysis of individual particles by analytical electron microscopy as well as quantitative analysis using particle‐induced X‐ray emission (PIXE) and particle elastic scattering analysis (PESA) were carried out on samples collected from a flight at 10 km altitude between 50°N and 30°S as part of the Civil Aircraft for Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) project (http://www.caribic-atmospheric.com). Particle morphology showed large variability with sampling latitude. Complicated branched structures dominated the large particles of the extratropical northern and southern hemisphere and the northern tropics. Particles in the tropics of the southern hemisphere were small in size and large in number concentration, whereas particles in or close to the intertropical convergence zone were few and small in size. Particles in the lowermost stratosphere were found to have similar structures but more branched than the ones found in the upper troposphere of the extratropics. Quantitative analysis revealed that the sulfur concentration varied by a factor of 50 in the nine samples analyzed in this study. The carbon‐to‐sulfur mass concentration ratio was lowest in the lowermost stratosphere (0.5) and highest in the tropics of the southern hemisphere (3.5). The elemental distribution of carbon and sulfur in individual particles was mapped by energy‐filtered transmission electron microscopy (EFTEM). Almost all particles analyzed contained a mixture of carbonaceous and sulfurous matter. Particles with satellites were found by EFTEM to contain both carbon and sulfur in the central particle, whereas in the satellite particles only carbonaceous material was detected.

Increase of the aerosol hygroscopicity by cloud processing in a mesoscale convective system: a case study from the AMMA campaign

Abstract. Aerosol properties were measured during an airborne campaign experiment that took place in July 2006 in West Africa within the framework of the African Monsoon Multidisciplinary Analyses (AMMA). The goal of the present study was to determine the main microphysical processes that affect the aerosols during the passage of a mesoscale convective system (MCS) over the region of Niamey in Niger. A significant change in the aerosol profiles measured before and after the passage of the MCS was found in a layer located between 1300 and 3000 m, where the aerosol concentration drastically decreased after the passage of the MCS. Concurrently, a significant increase in the cloud condensation nuclei (CCN) fraction was also observed during the post-MCS period in the same layer. Moreover, the results of the elemental composition analyses of individual particles collected in this layer after the MCS passage have shown higher contributions of sulfate, nitrate and chloride to the total aerosol mass. A mesoscale atmospheric model with on-line dust parameterization and Lagrangian backtrajectories was used to interpret the impact of the MCS on the aerosol properties. The results of the simulation show that the MCS 1) generates dust particles at the surface in the gust front of the system and washout of particles during the system precipitation, 2) modifies the aerosol mixing state (intensive aerosol property) through cloud processing, and 3) enhances CCN activity of particles through coating by soluble material.

Comparison of ICP-MS and SIMS techniques for determining uranium isotope ratios in individual particles

The determination of uranium isotope ratios in individual particles is of great importance for nuclear safeguards. In the present study, an analytical technique by inductively coupled plasma mass spectrometry (ICP-MS) with a desolvation sample introduction system was applied to isotope ratio analysis of individual uranium particles. In ICP-MS analysis of individual uranium particles with diameters ranging from 0.6 to 4.2 μm in a standard reference material (NBL CRM U050), the use of the desolvation system for sample introduction improved the precision of 234U/ 238U and 236U/ 238U isotope ratios. The performance of ICP-MS with desolvation was compared with that of a conventionally used method, i.e., secondary ion mass spectrometry (SIMS). The analysis of test swipe samples taken at nuclear facilities implied that the performance of ICP-MS with desolvation was superior to that of SIMS in a viewpoint of accuracy, because the problems of agglomeration of uranium particles and molecular ion interferences by other elements could be avoided. These results indicated that ICP-MS with desolvation has an enough ability to become an effective tool for nuclear safeguards.

Iron isotopic fractionation in industrial emissions and urban aerosols

A study on tropospheric aerosols involving Fe particles with an industrial origin is tackled here. Aerosols were collected at the largest exhausts of a major European steel metallurgy plant and around its near urban environment. A combination of bulk and individual particle analysis performed by SEM–EDX provides the chemical composition of Fe-bearing aerosols emitted within the factory process (hematite, magnetite and agglomerates of these oxides with sylvite (KCl), calcite (CaCO 3) and graphite carbon). Fe isotopic compositions of those emissions fall within the range (0.08‰ < δ 56Fe < +0.80‰) of enriched ores processed by the manufacturer (−0.16‰ < δ 56Fe < +1.19‰). No significant evolution of Fe fractionation during steelworks processes is observed. At the industrial source, Fe is mainly present as oxide particles, to some extent in 3–4 μm aggregates. In the close urban area, 5 km away from the steel plant, individual particle analysis of collected aerosols presents, in addition to the industrial particle type, aluminosilicates and related natural particles (gypsum, quartz, calcite and reacted sea salt). The Fe isotopic composition ( δ 56Fe = 0.14 ± 0.11‰) measured in the close urban environment of the steel metallurgy plant appears coherent with an external mixing of industrial and continental Fe-containing tropospheric aerosols, as evidenced by individual particle chemical analysis. Our isotopic data provide a first estimation of an anthropogenic source term as part of the study of photochemically promoted dissolution processes and related Fe fractionations in tropospheric aerosols.

Patterns and modeling of the long-term optics record of Onondaga Lake, New York

A retrospective analysis of long-term data sets of Secchi disc depth (SD, 40 years), the diffuse light attenuation coefficient for downwelling irradiance for photosynthetically available radiation (k d (PAR), 23 years), and chlorophyll-a ([Chl], 28 years), is presented for culturally eutrophic and industrially polluted Onondaga Lake, New York. The effects of changes in multiple drivers on SD and k d (PAR) are resolved in the record, including: (1) salinity decreases from closure of an industry, (2) changes in the grazing by exotic and native Daphnia, (3) long-term variations in populations of planktivorous fish, (4) runoff events, and (5) progressive decreases in phosphorus (P) loading. Four time intervals, or regimes, are identified for the record that had unifying features with respect to drivers and SD observations. The most dramatic changes in clarity conditions were the abrupt transition to annual occurrences of a clear-water phase (CWP) for 16 years following a coupled decrease in salinity and return of native Daphnia, and the subsequent loss of the CWP (for 5 years) from the loss of these cladocerans. The CWP was characterized by coincident dramatic increases in SD (annual maxima ≥ 4.55 m) and decreases in [Chl] and high densities of Daphnia. The benefits of P management were most clearly manifested by a 3-fold decrease in average [Chl] and a 2-fold increase in SD between two of the regimes, separated by 25 years, which both lacked CWPs. A probabilistic mechanistic model for SD and k d (PAR), that represents the effects of multiple constituents on the regulating processes of absorption and scattering, is developed, tested for the long-term record. The model is applied to partition the scattering coefficient (b) according to contributions of phytoplankton and tripton (b NAP ). Good model performance is demonstrated through: (1) closure of estimates of b with independent measurements, (2) consistencies of b NAP predictions with independent estimates based on an individual particle analysis technique, and the timing of runoff events, and (3) closure of predictions of k d (PAR) with observations. Broadly applicable nomographs are formed with the model that represent the dependence of SD and k d (PAR) on phytoplankton ([Chl]) and inorganic tripton (b NAP ) levels, that can be used to predict responses of these optical metrics to changes in the levels of these attenuating constituents. Inorganic tripton in the size range 1 to 10 μm, has played a critical role in influencing important features of the lake's optical regime by: (1) contributing importantly to b throughout the record (30 to 40 %, on average), (2) regulating optical signatures from runoff and CWP events, and (3) limiting increases in SD that can be achieved from decreases in phytoplankton biomass.

Automated optical microscopy of coated particle fuel

Fundamental technological advances have occurred during the 20 year hiatus in US research on coated particle nuclear fuel. As part of the recent US Department of Energy’s Advanced Gas Reactor Fuel Development and Qualification program, Oak Ridge National Laboratory has utilized advancements in computer automation, digital imaging, and image analysis to modernize US optical microscopy techniques for coated particle nuclear fuel. Automated optical microscopy has enabled detailed and objective analysis of individual particles (hundreds of measurements per particle) and of large sample sizes that far exceed the capabilities of conventional manual microscopy methods (analysis of 1500–5000 particles is common). Demonstrative examples of the capabilities of this automated optical microscopy are given for: (a) shadow imaging of kernels, coated fuel particles, and graphite matrix overcoated particles and (b) cross-sectional analysis of coated fuel particles to determine layer thicknesses.