Abstract
AbstractSynchrotron-based micro-X-ray fluorescence (μXRF) equipment has been used to analyze impurities in polar ice. A customized sample holder has been developed and the μXRF equipment has been adapted with a thermal control system to keep samples unaltered during analyses. Artificial ice samples prepared from ultra-pure water were analyzed to investigate possible contamination and/or experimental artefacts. Analyses of polar ice from Antarctica (Dome C and Vostok) confirm this μXRF technique is non-destructive and sensitive. Experiments can be reproduced to confirm or refine results by focusing on interesting spots such as crystal grain boundaries or specific inclusions. Integration times and resolution can be adjusted to optimize sensitivity. Investigation of unstable particles is possible due to the short analysis time. In addition to identification of elements in impurities, μXRF is able to determine their speciations. The accuracy and reliability of the results confirm the potential of this technique for research in glaciology.
Highlights
Studying impurities in ice is essential for current research in glaciology
Control of the experimental procedure and background estimation To estimate the contamination introduced by the sample preparation and to test the influence of the Ultralene[1] film, two XRF spectra (Fig. 2) were taken under the same experimental conditions as for the polar ice samples: one using a sample cell filled with air and the other using an artificial sample (S1), which was analyzed by ion chromatography
To take account of the variations in the incoming intensity (Io) during experiments, all the figures presented in this paper show the relative intensity, i.e. the ratio (I/Io) of the emitted signal (I) to the incoming intensity
Summary
Analysis of melted samples by ion chromatography gives the average ionic concentrations of soluble (mineral and organic) species, even at very low concentrations. Such information is used for studying past atmospheric composition, for example. Due to the possible interaction between chemical impurities and physical properties it is of primary interest to know the microstructural localization of impurities. Depending on their localization, either dispersed in the ice matrix or concentrated at grain boundaries, the structure of the sample may evolve from its original in situ state. Reactions between soluble sulphuric acid and carbonate particulates may alter the record of atmospheric CO2 present in air bubbles trapped in the ice (Legrand and Mayewski, 1997)
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