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Supercooled interfacial water in fine-grained soils probed by dielectric spectroscopy

  • Water substantially affects nearly all physical, chemical and biological processes on the Earth. Recent Mars observations as well as laboratory investigations suggest that water is a key factor of current physical and chemical processes on the Martian surface, e.g. rheological phenomena. Therefore it is of particular interest to get information about the liquid-like state of water on Martian analogue soils for temperatures below 0 °C. To this end, a parallel plate capacitor has been developed to obtain isothermal dielectric spectra of fine-grained soils in the frequency range from 10 Hz to 1.1 MHz at Martian-like temperatures down to −70 °C. Two Martian analogue soils have been investigated: a Ca-bentonite (specific surface of 237 m2 g−1, up to 9.4% w / w gravimetric water content) and JSC Mars 1, a volcanic ash (specific surface of 146 m2 g−1, up to 7.4% w / w). Three soil-specific relaxation processes are observed in the investigated frequency–temperature range: two weak high-frequency processes (bound or hydrated water as well as ice) and a strong low-frequency process due to counter-ion relaxation and the Maxwell–Wagner effect. To characterize the dielectric relaxation behaviour, a generalized fractional dielectric relaxation model was applied assuming three active relaxation processes with relaxation time of the ith process modelled with an Eyring equation. The real part of effective complex soil permittivity at 350 kHz was used to determine ice and liquid-like water content by means of the Birchak or CRIM equation. There are evidence that bentonite down to −70 °C has a liquid-like water content of 1.17 monolayers and JSC Mars 1 a liquid-like water content of 1.96 monolayers.

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Document Type:Article
Author: Andreas Lorek, Norbert Wagner
DOI (Cite-Link):https://doi.org/10.25643/bauhaus-universitaet.3149Cite-Link
URN (Cite-Link):https://nbn-resolving.org/urn:nbn:de:gbv:wim2-20170425-31490Cite-Link
Parent Title (English):Cryosphere
Date of Publication (online):2017/04/25
Year of first Publication:2013
Release Date:2017/04/25
Publishing Institution:Bauhaus-Universität Weimar
Institutes:An-Institute / Materialforschungs- und -prüfanstalt an der Bauhaus-Universität
First Page:1839
Last Page:1855
Tag:initerfacial water, liquid-like water, Mars, dielectric spectroscopy, ice, permittivity, JSC Mars 1, Bentonite, Birchak, CRIM, plate capacitor, monolayer, Hamaker constant, soil
GND Keyword:Wasser; Eis; Impedanzspektroskopie; Boden
Dewey Decimal Classification:500 Naturwissenschaften und Mathematik / 530 Physik
BKL-Classification:33 Physik / 33.07 Spektroskopie
Licence (German):License Logo Copyright All Rights Reserved - only metadata