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| Titel |
Direct observations of the atmospheric processing of Asian mineral dust |
| VerfasserIn |
R. C. Sullivan, S. A. Guazzotti, D. A. Sodeman, K. A. Prather |
| 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 ; 7, no. 5 ; Nr. 7, no. 5 (2007-02-22), S.1213-1236 |
| Datensatznummer |
250004741
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| Publikation (Nr.) |
 copernicus.org/acp-7-1213-2007.pdf |
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| Zusammenfassung |
| The accumulation of secondary acids and ammonium on individual mineral dust
particles during ACE-Asia has been measured with an online single-particle
mass spectrometer, the ATOFMS. Changes in the amounts of sulphate, nitrate,
and chloride mixed with dust particles correlate with air masses from
different source regions. The uptake of secondary acids depended on the
individual dust particle mineralogy; high amounts of nitrate accumulated on calcium-rich
dust while high amounts of sulphate accumulated on aluminosilicate-rich dust. Oxidation of
S(IV) to S(VI) by iron in the aluminosilicate dust is a possible explanation
for this enrichment of sulphate, which has important consequences for the
fertilization of remote oceans by soluble iron. This study shows the
segregation of sulphate from nitrate and chloride in individual aged dust particles
for the first time. A transport and aging timeline provides an
explanation for the observed segregation. Our data suggests that sulphate
became mixed with the dust first. This implies that the transport pathway
is more important than the reaction kinetics in determining which species
accumulate on mineral dust. Early in the study, dust particles in
volcanically influenced air masses were mixed predominately with sulphate.
Dust mixed with chloride then dominated over sulphate and nitrate when a
major dust front reached the R. V. Ronald Brown. We hypothesize that the
rapid increase in chloride on dust was due to mixing with HCl(g) released
from acidified sea salt particles induced by heterogeneous reaction with
volcanic SO2(g), prior to the arrival of the dust front. The amount of
ammonium mixed with dust correlated strongly with the total amount of
secondary acid reaction products in the dust. Submicron dust and ammonium
sulphate were internally mixed, contrary to frequent reports that they exist
as external mixtures. The size distribution of the mixing state of dust with
these secondary species validates previous mechanisms of the atmospheric
processing of dust and generally agrees with simulated aerosol chemistry
from the STEM-2K3 model. This series of novel results has important
implications for improving the treatment of dust in global chemistry models
and highlights a number of key processes that merit further investigation
through laboratory and field studies. |
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