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| Titel |
Mineral composition of TALDICE aeolian ice core dust by means of synchrotron radiation XAS and XRF techniques |
| VerfasserIn |
A. Marcelli, G. Cibin, M. Sala, D. Hampai, V. Maggi, F. Marino, B. Delmonte |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027408
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| Zusammenfassung |
| In this work we present the first accurate non-destructive comparison of the mineral
composition of atmospheric dusts contained in a deep ice core from Antarctica using
synchrotron radiation. Different mineral assemblages reaching glaciated areas could be
correlated to sources areas starting from the knowledge of the dust composition. In this
investigation we demonstrate the possibility to characterize with SR the mineral composition
of the dust in order to perform its geochemical characterization and to understand the pattern
of the transport and the trajectories of the aerosol.
This study has been focused on the elemental characterization and the identification of the
iron oxidation state of aeolian Antarctic dust by means of synchrotron radiation X-Ray
Fluorescence and X-Ray Absorption Spectroscopy. A set of twelve ice samples from the
TALDICE (TD, 72Ë 46’S, 159Ë 04’E, 2316 m a.s.l., mean accumulation rate 80
kg*m-2*yr-1) ice core, corresponding to the warm climatic period, Holocene, and to the
cold climatic period, Marine Isotopic Stage 3 (MIS 3) have been measured.
To obtain both the elemental composition and the iron oxidation state of the mineral dust
we performed experiments on specially prepared samples at the Stanford Synchrotron
Radiation Lightsource (SSRL) laboratory in the framework of the Proposal N.3082B.
Actually, melted ice samples were filtered and then mineral particles were deposited onto
Nuclepore polycarbonate membranes in a 1000 class clean room under a 100 class laminar
flow bench for both XRF and XAS experiments. A dedicated HV experimental
chamber, that allows performing different type of experimental technique on very low
absorber concentration samples was developed and tested in Italy. The original
experimental setup, including an in-vacuum sample micromanipulator and a special
alignment and docking sample system was installed at the beamline 10-2 at SSRL. For
the x-ray detection a 7 mm2 high sensitive Silicon Drift Detector was available
inside the HV chamber. XRF experiments allowed the detection of Na, Mg, Al,
Si, S, Cl, K, Ca, Ti, Cr and Fe elements. Differences in Ca and K concentration
between Holocene and MIS3 ice dust were clearly detected and measured with high
accuracy.
From the XANES analysis of mineral particles we recognised the presence of iron in an
octahedral coordination state and a shift of the Fe absorption edge towards low energies, a
behaviour characteristic of the reduction of the Fe2+concentration from MIS 3 to Holocene
ice samples. Combined XRF and XANES results clearly identify differences in the mineral
composition between Glacial and Interglacial periods, we associated to different
contributions from the Potential dust Source Areas (PSAs) of the Southern Hemisphere.
Although limited, data demonstrate that with this fully non-destructive technique, new
information about the dust mineralogy at very low concentration and transport mechanism of
aerosols can be performed using an intense synchrotron radiation X-ray source. |
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