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| Titel |
A method for sizing submicrometer particles in air collected on Formvar films and imaged by scanning electron microscope |
| VerfasserIn |
E. Hamacher-Barth, K. Jansson, C. Leck |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 12 ; Nr. 6, no. 12 (2013-12-10), S.3459-3475 |
| Datensatznummer |
250085131
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| Publikation (Nr.) |
 copernicus.org/amt-6-3459-2013.pdf |
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| Zusammenfassung |
A method was developed to systematically investigate individual aerosol
particles collected onto a polyvinyl formal (Formvar)-coated copper grid with
scanning electron microscopy. At very mild conditions with a low accelerating
voltage of 2 kV and Gentle Beam mode aerosol particles down to 20 nm in
diameter can be observed. Subsequent processing of the images with digital
image analysis provides size resolved and morphological information
(elongation, circularity) on the aerosol particle population. Polystyrene
nanospheres in the expected size range of the ambient aerosol particles
(20–900 nm in diameter) were used to confirm the accuracy of sizing and
determination of morphological parameters. The relative standard deviation of
the diameters of the spheres was better than ±10% for sizes larger
than 40 nm and ±18% for 21 nm particles compared to the
manufacturer's certificate.
Atmospheric particles were collected during an icebreaker expedition to the
high Arctic (north of 80°) in the summer of 2008. Two samples
collected during two different meteorological regimes were analyzed. Their
size distributions were compared with simultaneously collected size
distributions from a Twin Differential Mobility Particle Sizer, which
confirmed that a representative fraction of the aerosol particles was imaged
under the electron microscope. The size distributions obtained by scanning
electron microscopy showed good agreement with the Twin Differential Mobility
Sizer in the Aitken mode, whereas in the accumulation mode the size
determination was
critically dependent on the contrast of the aerosol with the Formvar-coated
copper grid. The morphological properties (elongation, circularity) changed
with the number of days the air masses spent over the pack-ice area north of
80° before the aerosol particles were collected at the position of the
icebreaker and are thus an appropriate measure to characterize transformation
processes of ambient aerosol particles. |
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