Publication Details |
| Category | Text Publication |
| Reference Category | Journals |
| DOI | 10.1029/2025JB031945 |
Licence  |
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| Title (Primary) | Broadband dielectric analysis of clays: Impact of cation, exchange capacity, water content, and porosity |
| Author | Schmidt, F.; Wagner, N.; Mulder, I.; Emmerich, K.; Bore, T.; Bumberger, J.
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| Source Titel | Journal of Geophysical Research-Solid Earth |
| Year | 2026 |
| Department | MET |
| Volume | 131 |
| Issue | 3 |
| Page From | e2025JB031945 |
| Language | englisch |
| Topic | T5 Future Landscapes |
| Data and Software links | https://doi.org/10.5281/zenodo.15473270 |
| Abstract |
Clay-rich soils and sediments are key components of
near-surface systems, influencing water retention, ion exchange, and
structural stability. Their complex dielectric response under moist
conditions arises from surface–ion electrostatics and diffuse double
layers that govern transport and retention processes. This study
explores the broadband dielectric spectra (1 MHz–5 GHz) of four
water-saturated clays (kaolinite, illite, and two sodium-activated
bentonites) in a coaxial transmission-line setup. The spectra were
parameterized with two phenomenological relaxation models–the
Generalized Dielectric Relaxation Model (GDR) and the Combined
Permittivity-Conductivity Model (CPCM)–and two mixture models: the
Augmented Broadband Complex Dielectric Mixture Model (ABC-M) and the
Complex Refractive Index Model (CRIM). These approaches were evaluated
for their ability to link dielectric relaxation behavior to key
petrophysical parameters such as Cation Exchange Capacity (CEC),
Volumetric Water Content (VWC), and porosity. The results demonstrate
distinct spectral signatures correlating with clay mineralogy,
particularly at low frequencies. Relaxation strength and apparent DC
conductivity show systematic relationships with CEC, emphasizing the
influence of clay-specific surface properties. While expandable clays
like bentonites displayed enhanced relaxation due to ion-exchange
dynamics, deviations in a soda-activated bentonite highlighted the
impact of chemical treatments on dielectric behavior. Overall, the study
highlights both the potential and the limitations of broadband
dielectric spectroscopy for soil and clay characterization. This study
provides a systematic framework for linking clay mineral physics to
applied electromagnetic methods. The results have significant
implications for non-invasive, frequency-domain methods for
characterizing soils and sediments, hydrological modeling, geotechnical
evaluation, and environmental monitoring. |
| Schmidt, F., Wagner, N., Mulder, I., Emmerich, K., Bore, T., Bumberger, J. (2026): Broadband dielectric analysis of clays: Impact of cation, exchange capacity, water content, and porosity J. Geophys. Res.-Solid Earth 131 (3), e2025JB031945 10.1029/2025JB031945 |
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