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| Titel |
Predicting the mineral composition of dust aerosols – Part 1: Representing key processes |
| VerfasserIn |
J. P. Perlwitz, C. Pérez García-Pando, R. L. Miller |
| 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 ; 15, no. 20 ; Nr. 15, no. 20 (2015-10-21), S.11593-11627 |
| Datensatznummer |
250120107
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| Publikation (Nr.) |
 copernicus.org/acp-15-11593-2015.pdf |
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| Zusammenfassung |
| Soil dust aerosols created by wind erosion are typically assigned
globally uniform physical and chemical properties within Earth
system models, despite known regional variations in the mineral
content of the parent soil. Mineral composition of the aerosol
particles is important to their interaction with climate, including
shortwave absorption and radiative forcing, nucleation of cloud
droplets and ice crystals, heterogeneous formation of sulfates and
nitrates, and atmospheric processing of iron into bioavailable forms
that increase the productivity of marine phytoplankton. Here,
aerosol mineral composition is derived by extending a method that
provides the composition of a wet-sieved soil. The extension
accounts for measurements showing significant differences between
the mineral fractions of the wet-sieved soil and the emitted aerosol
concentration. For example, some phyllosilicate aerosols are more
prevalent at silt sizes, even though they are nearly absent at these
diameters in a soil whose aggregates are dispersed by wet sieving.
We calculate the emitted mass of each mineral with respect to size
by accounting for the disintegration of soil aggregates during wet
sieving. These aggregates are emitted during mobilization and
fragmentation of the original undispersed soil that is subject to
wind erosion. The emitted aggregates are carried far downwind from
their parent soil. The soil mineral fractions used to calculate the
aggregates also include larger particles that are suspended only in
the vicinity of the source. We calculate the emitted size
distribution of these particles using a normalized distribution
derived from aerosol measurements. In addition, a method is
proposed for mixing minerals with small impurities composed of iron
oxides. These mixtures are important for transporting iron far from
the dust source, because pure iron oxides are more dense and
vulnerable to gravitational removal than most minerals comprising
dust aerosols. A limited comparison to measurements from North
Africa shows that the model extensions result in better agreement,
consistent with a more extensive comparison to global observations
as well as measurements of elemental composition downwind of the
Sahara, as described in companion articles. |
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