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| Titel |
Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment |
| VerfasserIn |
M. Radhi, M. A. Box, G. P. Box, R. M. Mitchell, D. D. Cohen, E. Stelcer, M. D. Keywood |
| 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 ; 10, no. 13 ; Nr. 10, no. 13 (2010-07-02), S.5925-5942 |
| Datensatznummer |
250008592
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| Publikation (Nr.) |
 copernicus.org/acp-10-5925-2010.pdf |
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| Zusammenfassung |
Mineral dust is one of the major components of the
world's aerosol mix, having a number of impacts within the Earth system.
However, the climate forcing impact of mineral dust is currently poorly
constrained, with even its sign uncertain. As Australian deserts are more
reddish than those in the Northern Hemisphere, it is important to better
understand the physical, chemical and optical properties of this important
aerosol. We have investigated the properties of Australian desert dust at a
site in SW Queensland, which is strongly influenced by both dust and biomass
burning aerosol.
Three years of ground-based monitoring of spectral optical thickness has
provided a statistical picture of gross aerosol properties. The aerosol
optical depth data showed a clear though moderate seasonal cycle with an
annual mean of 0.06 ± 0.03. The Angstrom coefficient showed a stronger
cycle, indicating the influence of the winter-spring burning season in
Australia's north. AERONET size distributions showed a generally bimodal
character, with the coarse mode assumed to be mineral dust, and the fine
mode a mixture of fine dust, biomass burning and marine biogenic material.
In November 2006 we undertook a field campaign which collected 4 sets of
size-resolved aerosol samples for laboratory analysis – ion beam analysis
and ion chromatography. Ion beam analysis was used to determine the
elemental composition of all filter samples, although elemental ratios were
considered the most reliable output. Scatter plots showed that Fe, Al and Ti
were well correlated with Si, and Co reasonably well correlated with Si,
with the Fe/Al ratio somewhat higher than values reported from Northern
Hemisphere sites (as expected). Scatter plots for Ca, Mn and K against Si
showed clear evidence of a second population, which in some cases could be
identified with a particular sample day or size fraction. These data may be
used to attempt to build a signature of soil in this region of the
Australian interior.
Ion chromatography was used to quantify water soluble ions for 2 of our
sample sets, complementing the picture provided by ion beam analysis. The
strong similarities between the MSA and SO42− size distributions
argue strongly for a marine origin of much of the SO42−. The
similarity of the Na+, Cl− and Mg2+ size distributions also
argue for a marine contribution. Further, we believe that both
NO3− and NH4+ are the result of surface reactions with
appropriate gases. |
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