When studying the migration behaviour of trace elements or radionuclides in argillaceous rocks, one assumes that the thermodynamics underlying the speciation of radionuclides in the confined pore water is the same as one for bulk water. This might be not the case at all. Therefore it is necessary to learn more about thermodynamics in confined solutions.
Perhaps you want to have a look at the work of one of my colleagues from chemistry at the University of Nebraska-Lincoln about a new state of confined water
(http://newsroom.unl.edu/releases/2012/12/12/'Nebraska+Ice'+leads+to+3+more+discoveries)
Here a quote from the popular article which references the scientific articles:
" Nebraska Ice is the nickname for a startling discovery that water contracts rather than expands when it is frozen at extremes of subnanoscale confinement".
As to water itself, both dynamics and thermodynamics in confined geometries are significantly different from their bulk analogues and strongly dependent on dimensionality.
Two good (though not exhaustive - this field keeps evolving, and rapidly) references you could examine are 1) the 2003 monograph by Buch and Devlin ('Water in Confined Geometries') and 2) the 2008 computational review by Brovchenko and Oleinikova ('Interfacial and Confined Water').
As to experimental techniques involved, take a serious look at works performed in high- and low-resolution NMR, as well as as to neutron and dielectric spectroscopy.
Thanks Alexandra for this input. So far we did neutron spectroscopy on different clay samples at different degrees of compaction and humidity. This does not really bring us further. Although one sees that the confined water is different from bulk water (e.g. from the freezing behaviour as measured in fix window scans), I don't know how to translate this in terms of thermodynamics. For instance, how do I have to calculate the speciation of cations in confined water. Are the thermodynamic constants for the species the same as in bulk water or are they different. I guess they are different, but how different?
Perhaps the use of reverse micelles is a good approach to learn more about this.
You're probably right:
http://wp.natsci.colostate.edu/crans/files/2013/08/Lemons2013NJCVO2Catecholate.pdf
Confined water is rather an unexplored territory, which still needs massive characterization. I'd go for NMR spectroscopy and a parallel surfing through the (vast) spectroscopic literature about zeolites and polar glasses (e.g., Vycor).
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