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| Titel |
TEM analysis of the internal structures and mineralogy of Asian dust particles and the implications for optical modeling |
| VerfasserIn |
G. Y. Jeong, T. Nousiainen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 14 ; Nr. 14, no. 14 (2014-07-16), S.7233-7254 |
| Datensatznummer |
250118890
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| Publikation (Nr.) |
 copernicus.org/acp-14-7233-2014.pdf |
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| Zusammenfassung |
| Mineral dust interacts with incoming/outgoing
electromagnetic radiation in the atmosphere. This interaction depends on the
microphysical properties of the dust particles, including size, mineral
composition, external morphology, and internal structure. Ideally all of these
properties should be accounted for in the remote sensing of dust, the modeling of
single-scattering properties, and radiative effect assessment. There have
been many reports on the microphysical characterizations of mineral dust,
but no investigations of the internal structures of individual dust
particles. We explored the interiors of Asian dust particles using the
combined application of focused ion beam thin-slice preparation and
high-resolution transmission electron microscopy. The results showed that
individual dust particles consisted of numerous mineral grains, which were
organized into several types of internal structure: single and
polycrystalline cores of quartz, feldspars, calcite, and amphibole often
with oriented clay coatings; individual clay agglomerates of nano-thin clay
platelets showing preferred to random orientations common with coarser
mineral inclusions; and platy coarse phyllosilicates (muscovite, biotite,
and chlorite). Micron to submicron pores were scattered throughout the
interior of particles. Clays in the coatings and agglomerates were dominated
by nano-thin platelets of the clay minerals of illite–smectite series
including illite, smectite, and their mixed layers with subordinate
kaolinite and clay-sized chlorite. Submicron iron oxide grains, dominantly
goethite, were distributed throughout the clay agglomerates and coatings.
Unlike the common assumptions and simplifications, we found that the
analyzed dust particles were irregularly shaped with birefringent,
polycrystalline, and polymineralic heterogeneous compositions. Accounting
for this structural and mineralogical makeup may improve the remote sensing
retrieval of dust and the evaluation of radiation effects, but will also
require sophisticated single-scattering modeling. In particular, the
observed internal structures of dust particles such as clay coatings,
preferred orientation, embedded grains in clays, and pores, have the
potential to considerably impact on the light scattering by dust particles.
The distribution and size of structural components with contrasting
dielectric properties, such as iron oxides, should also be explicitly
accounted for. |
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