Broadband Electrical Impedance Tomography for Subsurface Characterization Using Improved Corrections of Electromagnetic Coupling and Spectral Regularization

Kemna, Andreas; Huisman, Johan Alexander; Zimmermann, Egon; Martin, Roland; Zhao, Yulong; Treichel, Andrea; Flores-Orozco, Adrián; Fechner, Thomas

doi:10.1007/978-3-319-04205-3_1

Cited by 17 publications

(17 citation statements)

References 22 publications

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“…Research has also been conducted on electrical properties at the cellular scale, including electrical surface properties of cell membranes, also called plasma membranes (e.g., Kinraide, 1994;Wang et al, 2011). An electrical double layer (EDL) forms at an electrically charged surface in contact with an electrolyte (e.g., Lyklema, 2005).…”

Section: Introductionmentioning

confidence: 99%

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

Weigand

Kemna

2017

Biogeosciences

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Abstract. A better understanding of root–soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)- electrical conduction- and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water–filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.

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Section: Introductionmentioning

confidence: 99%

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

Weigand

Kemna

2017

Biogeosciences

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“…Field‐based acquisition of CC parameters is increasing with the advent of new instrumentation and measurement techniques (Kemna et al, ; Slater et al, 2018). Considering the impracticality of applying the geometric permeability models in the field, the geophysical models might provide a solution to field‐scale estimation of permeability.…”

Section: Discussionmentioning

confidence: 99%

On Permeability Prediction From Complex Conductivity Measurements Using Polarization Magnitude and Relaxation Time

Robinson

Slater

Weller

et al. 2018

Water Resources Research

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Geophysical length scales determined from complex conductivity (CC) measurements can be used to estimate permeability k when the electrical formation factor F is known. Two geophysical length scales have been proposed: (1) the specific polarizability cp normalized by the imaginary conductivity σ″ and (2) the time constant τ multiplied by a diffusion coefficient D+. The parameters cp and D+ account for the control of fluid chemistry and/or varying minerology on the geophysical length scale. We evaluated the predictive capability of two CC permeability models: (1) an empirical formulation based on σ″ or normalized chargeability mn and (2) a mechanistic formulation based on τ. The performance of the CC models was evaluated against measured k; and further compared against that of well‐established k estimation equations that use geometric length scales. Both CC models predict permeability within one order of magnitude for a database of 58 sandstone samples, with the exception of samples characterized by high pore volume normalized surface area Spor. Variations in cp and D+ likely contribute to the poor model performance for the high Spor samples, which contain significant dolomite. Two observations favor the implementation of the σ″‐based model over the τ‐based model for field‐scale k estimation: (1) a limited range of variation in cp relative to D+ and (2) σ″ field measurements are less time consuming to acquire relative to τ. The need for a reliable field‐estimate of F limits application of either model, in particular the σ″ model due to a high power law exponent associated with F.

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“…Spatio‐spectral regularisation was also implemented recently by Kemna et al . (). We assigned equal weight to reducing the differences between the models (images) at different frequencies and reducing the individual model roughness.…”

Section: Field Methodsmentioning

confidence: 97%

Field Test of Detection and Characterisation of Subsurface Ice using Broadband Spectral-Induced Polarisation

Grimm

Stillman

2015

Permafrost and Periglac. Process.

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Low-frequency (LF, <<1 kHz) electrical resistivity is useful in discriminating frozen from unfrozen ground in periglacial environments, but it cannot distinguish whether frozen materials are dry or ice-rich, nor can it provide reliable estimates of ice content. However, polarisabilities due to unfrozen, interfacial water and protonic defects in ice both have strong dielectric relaxations (frequency dependence), resulting in a large decrease in resistivity at high frequencies (HF, > > 1 kHz). From laboratory measurements of samples collected at the US Army Permafrost Tunnel (Fox, Alaska), we find temperature-dependent relationships between ice volume fraction and the resistivity frequency effect (RFE, defined as the LF-normalised difference in LF and HF resistivities). We report the first field detection of H 2 O polarisability in permafrost, using a broadband spectral-induced polarisation system at the permafrost tunnel. By comparing laboratory and field spectra, we found a best-fitting ice temperature of -3 ± 0.5°C. Laboratory RFE at the selected temperature was then used to map the RFE in the tunnel wall to 45 À 95 per cent ice by volume. Both of these results agreed quantitatively with the bulk properties of the tunnel, and the ice content image correlated qualitatively with major permafrost features. The RFE approach may be expedient using simpler instrumentation, but the close agreement of laboratory and field spectra indicates that the ice and interfacial water signatures can be individually quantified by broadband fitting of both amplitude and phase. This will provide more accurate constitutive relations, but more importantly will yield better remote temperature measurement of the subsurface using known dependencies of the dielectric relaxation frequencies.* Includes reciprocals. AB, MN = Transmitter and receiver dipole positions; R = transfer resistance, respectively; σ = standard error.(Continued) 36 R.

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Broadband Electrical Impedance Tomography for Subsurface Characterization Using Improved Corrections of Electromagnetic Coupling and Spectral Regularization

Cited by 17 publications

References 22 publications

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

On Permeability Prediction From Complex Conductivity Measurements Using Polarization Magnitude and Relaxation Time

Field Test of Detection and Characterisation of Subsurface Ice using Broadband Spectral-Induced Polarisation

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