Extraction of environmental information from large aerosol data sets through combined application of cluster and factor analyses

Suspended particulate matter (SPM) has a complicated system of emission and transport, and a receptor model is required for apportioning the sources of SPM. We have developed a method for individual particle analysis as a method of source apportionment using electron probe microanalysis (EPMA). In this method, elemental analysis of individual SPM particles is carried out using EPMA and the emission source of each is defined according to its x-ray spectrum. When many particles are analysed, cluster analysis is used to classify particles based on the similarity of elemental composition. If this procedure were automated it could process data more rapidly, with little work required of an analyst. In this study, we examined different kinds of cluster analyses using the data obtained from real SPM samples to increase the reliability of cluster analysis as the method of data analysis for SPM source apportionment.

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“…In other words, a large background indicates the possible presence of light elements. 20 The background index, B j , of particle j was defined as…”

Section: Individual Particle Analysismentioning

confidence: 99%

Individual particle analysis for source apportionment of suspended particulate matter using electron probe microanalysis

Kim

Tomiyasu

Owari

et al. 2001

Surface & Interface Analysis

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“…7 Classification of the various particle types is also extensively used for source apportionment. [9][10][11][12] Furthermore, heterogeneous chemistry of individual atmospheric particles can be evidenced. [13][14][15][16][17][18][19][20] In these last cases, quantitative work may result in a better identification of sources.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, it is known that aerosol radiative forcing is strongly affected by the mixing state of airborne particles. Improved knowledge of the complex nature of ambient particles allows better estimates to be made of their optical properties. , Classification of the various particle types is also extensively used for source apportionment. − Furthermore, heterogeneous chemistry of individual atmospheric particles can be evidenced. − In these last cases, quantitative work may result in a better identification of sources. Precise relative amounts of elements are also required to differentiate particles in various stages of conversion.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Determination of Low-ZElements in Single Atmospheric Particles on Boron Substrates by Automated Scanning Electron Microscopy−Energy-Dispersive X-ray Spectrometry

et al. 2005

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

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“…For chemical characterization of atmospheric particles, electron probe x-ray microanalysis (EPMA) is a widely applied technique that can provide excellent possibilities for automated analysis. For source profiling of aerosol samples, semiquantitative approaches using the net peak intensities combined with chemometric methods such as cluster and factor analyses are generally used (De Bock et al 1998, Treiger et al 1995. However, quantitative results are required in some applications where the origin of the particles has to be identified without question.…”

Section: Introductionmentioning

confidence: 99%

Characterization of atmospheric particles by electron probe X‐ray microanalysis

et al. 2002

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Summary: Microchemical glass standards were used to validate a quantitation method based on peak-to-background (P/B) ratios from electron probe x-ray microanalysis spectra. This standardless method was applied to the determination of concentrations of individual particles from Mα or Lα lines, as well as from Kα lines. The algorithm was tested on particulate glass samples for diameters ranging from 1 to 20 µm. The determined concentrations did not depend on particle size. The certified values for elements were well matched, except for Na, which may migrate under electron bombardment. Finally, classification of qualitative results obtained for aerosol particles was completed by the P/B quantitative method.

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Extraction of environmental information from large aerosol data sets through combined application of cluster and factor analyses

Cited by 7 publications

References 13 publications

Individual particle analysis for source apportionment of suspended particulate matter using electron probe microanalysis

Individual particle analysis for source apportionment of suspended particulate matter using electron probe microanalysis

Quantitative Determination of Low-ZElements in Single Atmospheric Particles on Boron Substrates by Automated Scanning Electron Microscopy−Energy-Dispersive X-ray Spectrometry

Characterization of atmospheric particles by electron probe X‐ray microanalysis

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