Induced Polarization Signals Research Articles

Induced polarization applied to biogeophysics: recent advances and future prospects

ABSTRACTThis paper provides an update on the fast‐evolving field of the induced polarization method applied to biogeophysics. It emphasizes recent advances in the understanding of the induced polarization signals stemming from biological materials and their activity, points out new developments and applications, and identifies existing knowledge gaps. The focus of this review is on the application of induced polarization to study living organisms: soil microorganisms and plants (both roots and stems). We first discuss observed links between the induced polarization signal and microbial cell structure, activity and biofilm formation. We provide an up‐to‐date conceptual model of the electrical behaviour of the microbial cells and biofilms under the influence of an external electrical field. We also review the latest biogeophysical studies, including work on hydrocarbon biodegradation, contaminant sequestration, soil strengthening and peatland characterization. We then elaborate on the induced polarization signature of the plant‐root zone, relying on a conceptual model for the generation of biogeophysical signals from a plant‐root cell. First laboratory experiments show that single roots and root system are highly polarizable. They also present encouraging results for imaging root systems embedded in a medium, and gaining information on the mass density distribution, the structure or the physiological characteristics of root systems. In addition, we highlight the application of induced polarization to characterize wood and tree structures through tomography of the stem. Finally, we discuss up‐ and down‐scaling between laboratory and field studies, as well as joint interpretation of induced polarization and other environmental data. We emphasize the need for intermediate‐scale studies and the benefits of using induced polarization as a time‐lapse monitoring method. We conclude with the promising integration of induced polarization in interdisciplinary mechanistic models to better understand and quantify subsurface biogeochemical processes.

Bacterial Stern layer diffusion: experimental determination with spectral induced polarization and sensitivity to nitrite toxicity

ABSTRACTSpectral induced polarization signatures have been used as proxies for microbial abundance in subsurface environments, by taking advantage of the charged properties of microbial cell membranes. The method's applicability, however, remains qualitative, and signal interpretation ambiguous. The adoption of spectral induced polarization as a robust geo‐microbiological tool for monitoring microbial dynamics in porous media requires the development of quantitative relationships between biogeochemical targets and spectral induced polarization parameters, such as biomass density and imaginary conductivity (σ″). Furthermore, deriving cell density information from electrical signals in porous media necessitates a detailed understanding of the nature of the cell membrane surface charge dynamics. We present results from a fully saturated sand‐filled column reactor experiment where Shewanella oneidensis growth during nitrate reduction to ammonium was monitored using spectral induced polarization. While our results further confirm the direct dependence of σ″ on changing cell density, Cole–Cole derived relaxation times also record the changing surface charging properties of the cells, ascribed to toxic stress due to nitrite accumulation. Concurrent estimates of cell size yield the first measurement‐derived estimation of the apparent surface ion diffusion coefficient for cells (Ds = 5.4 ±1.3 µm2 s−1), strengthening the link between spectral induced polarization and electrochemical cell polarization. Our analysis provides a theoretical framework on which to build σ″–cell density relations using bench‐scale experiments, leading to eventual robust non‐destructive monitoring of in situ microbial growth dynamics.

Mineralogical and textural controls on spectral induced polarization signatures of the Canadian Malartic gold deposit: Applications to mineral exploration

Applications of the spectral induced polarization (SIP) method to mineral exploration are limited by our knowledge of the relationships among rock texture, mineral composition, and electrical properties. Laboratory SIP responses were measured on rock samples from the Canadian Malartic gold deposit. Field SIP responses were also measured at the outcrop scale, along a profile that intersects a well-studied mineralized zone. The mineralogy and the texture of sedimentary rocks from this deposit were quantitatively determined with mineral liberation analysis. A systematic decrease (Pearson [Formula: see text]) in total chargeability with increasing fraction of the sulfide mineral interfaces associated with feldspar minerals (namely, K-feldspar and albite) was observed. On the other hand, total chargeability increased with the fraction of sulfide mineral interfaces associated with carbonates and micas (Pearson [Formula: see text]). At Canadian Malartic, proximal alteration in the mineralized zones is marked by rocks that lack a foliation plane and that were subjected to pervasive K-feldspar, albite, and pyrite alteration. In contrast, distal alteration in sedimentary rocks is marked by biotite, albite, carbonate, and pyrite that are oriented along the regional [Formula: see text] foliation. In the least-altered (LA) sedimentary rocks, quartz and biotite are associated with pyrrhotite and ilmenite as the main sulfide and oxide mineral phases, respectively. SIP measurements conducted at district and outcrop scales and along a drill core indicated that proximally altered sedimentary rocks were characterized by low total chargeability values ([Formula: see text] to [Formula: see text] in the laboratory and [Formula: see text] in the field). In contrast, the LA sedimentary rocks were characterized by total chargeability values up to [Formula: see text] in the laboratory and [Formula: see text] in the field. We conclude that mineralized zones associated with this type of ore deposit are characterized by low chargeability anomalies.

Electrical and seismic response of saline permafrost soil during freeze - Thaw transition

We conducted laboratory studies on the geophysical signals from Arctic saline permafrost soils to help understand the physical and mechanical processes during freeze-thaw cycles. Our results revealed low electrical resistivity (<20Ωm) and elastic moduli (7.7GPa for Young's modulus and 2.9GPa for shear modulus) at temperatures down to ~−10°C, indicating the presence of a significant amount of unfrozen saline water under the current field conditions. The spectral induced polarization signal showed a systematic shift during the freezing process, affected by concurrent changes of temperature, salinity, and ice formation. An anomalous induced polarization response was first observed during the transient period of supercooling and the onset of ice nucleation. Seismic measurements showed a characteristic maximal attenuation at the temperatures immediately below the freezing point, followed by a decrease with decreasing temperature. The calculated elastic moduli showed a non-hysteric response during the freeze – thaw cycle, which was different from the concurrently measured electrical resistivity response where a differential resistivity signal is observed depending on whether the soil is experiencing freezing or thawing. The differential electrical resistivity signal presents challenges for unfrozen water content estimation based on Archie's law. Using an improved formulation of Archie's law with a variable cementation exponent, the unfrozen water content estimation showed a large variation depending on the choice of the resistivity data during either a freezing or thawing cycle. Combining the electrical and seismic results, we suggest that, rather than a large hysteresis in the actual unfrozen water content, the shift of the resistivity response may reflect the changes of the distribution pattern of the unfrozen water (or ice) in the soil matrix during repeated freeze and thaw processes. Collectively, our results provide an improved petrophysical understanding of the physical and mechanical properties of saline permafrost during freeze – thaw transitions, and suggest that large uncertainty may exist when estimating the unfrozen water content using electrical resistivity data.

Delineating hazardous material without touching — AEM mapping of Norwegian alum shale

Alum shale is a particular type of metamorphic clay that occurs in Cambro-Ordovician metasediment units throughout southern Scandinavia. Owing to its geochemical composition, it is considered a large environmental challenge in Norway (Endre and Sormo, 2015) and poses a significant site hazard for infrastructure projects (Endre, 2014). Swedish alum shale has such a high Uranium content, that is was mined as a Uranium ore during the mid-1900s (Dyni, 2006). Norwegian alum shale typically contains more than 15 g/kg sulphides and 60-200 mg/kg Uranium. It is consequently a source for radon gas posing a risk to human health. The sulphides oxidize to produce sulphuric acid with pH down to 2-1 once the shale is exposed to air and water, posing a hazard to concrete and metal constructions and the environment. Finally, the most critical geotechnical risk connected to alum shale is its intense swelling owing to oxidation that has damaged properties in the vicinity of building sites that exposed alum shale units and consequently initiated swelling. Prior knowledge of the existence and extent of this hazardous shale is consequently a major risk management factor for underground building activities in areas prone to alum shale. The state of practice for identifying alum shale and other acid producing black shales classified by the Norwegian Environment Agency (Endre and Sormo, 2015), is primarily based on geochemistry and an understanding of the local geology. Geochemical identification is based on the balance between acidification- and neutralisation potential (Pabst et al., 2016) the geological risk for projects in alum shale prone areas is consequently high. In the worst case, a project may have to be abandoned, for example if the excavated shale volume exceeds the capacity of special waste landfills in the area. Geophysical delineation can decrease the geological risk and increases the efficiency of detailed volume assessments. Since 2014, we have been studying how sulphide and uranium content of various black shale types relate to electrical properties. Sulphide-rich alum shale has very low resistivity (~0.1 Ωm) (Lysdahl et al., 2015) and a strong induced polarization signature (Lysdahl et al., 2016). In the following we show the relationship between geochemically classified shale types and resistivity measurements directly on drill cores as well as surface electrical resistivity tomography (ERT) data. Two case histories show black shale units even at depths exceeding 80 metres based on airborne electromagnetic (AEM) surveying. Here we only focus on resistivity, for further studies on the polarization behaviour of alum shale please see Bazin et al. (2015) and (2017).

1D Cole-Cole inversion of TEM transients influenced by induced polarization

Effects of induced polarization (IP) can have an impact on time-domain electromagnetic measurements (TEM) and may lead to sign reversals in the recorded transients. To study these IP effects on TEM data, a new 1D inversion algorithm was developed for both, the central-loop and the separate-loop TEM configurations using the Cole-Cole relaxation model. 1D forward calculations for a homogeneous half-space were conducted with the aim of analyzing the impacts of the Cole-Cole parameters on TEM transients with respect to possible sign reversals. The forward modelings showed that the variation of different parameters have comparable effects on the TEM transients. This leads to an increasing number of equivalent models as a result of inversion calculations. Subsequently, 1D inversions of synthetic data were performed to study the potentials and limitations of the algorithm regarding the resolution of the Cole-Cole parameters. In order to achieve optimal inversion results, it was essential to error-weight the data points in the direct vicinity of sign reversals. The obtained findings were eventually adopted on the inversion of real field data which contained considerable IP signatures such as sign reversals. One field data set was recorded at the Nakyn kimberlite field in Western Yakutiya, Russia, in the central-loop configuration. Another field data set originates from a waste site in Cologne, Germany, and was measured utilizing the separate-loop configuration.

Induced polarization signature of coal seam fires

Induced polarization signature of coal seam fires

Performing the power spectrum-area method to separate anomaly from background for induced polarization data: (a case study; Hamyj copper deposit, Iran)

Anomaly separation plays a critical role in mineral exploration. The power spectrum-area considers the spatial data which give rise to detecting the anomalies more significantly. Induced polarization data has been surveyed using dipole-dipole array in the Hamyj copper index. Electrode spacing was designed at about 20 m. The Hamyj index was explored based on the result of remote sensing and economic geology. Hamyj deposit is located about 80 km west of Birjand city, South Khorasan province, Iran. In this paper, the induced polarization from the concentration-place domain was transferred to the time-frequency domain by using two dimensional Fourier transforms in order to use the power spectrum-area method. Then, the power spectrums of induced polarization signals were calculated and differentiated by means of fractal geometry. The threshold of separation for the design of digital filter was used to filter the data. Threshold IP and filtered data was calculated by concentration-area method. Finally, IP data and filtered data were compared with each other and 72 percentages of the anomalous data corresponded significantly with each other. The results showed that the power spectrum-area method can eliminate noise; hence, anomalies can be highlighted more sharply. As far as this study is concerned, this method can be used to suggest the best places for drilling.

Reconstruction of CMB temperature anisotropies with primordial CMB induced polarization in galaxy clusters

Abstract Scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces polarization signals determined by the quadrupole anisotropy in the photon distribution at the location of clusters. This ‘remote quadrupole’ derived from the measurements of the induced polarization in galaxy clusters provides an opportunity to reconstruct local CMB temperature anisotropies. In this Letter, we develop an algorithm of the reconstruction through the estimation of the underlying primordial gravitational potential, which is the origin of the CMB temperature and polarization fluctuations and CMB induced polarization in galaxy clusters. We found a nice reconstruction for the quadrupole and octopole components of the CMB temperature anisotropies with the assistance of the CMB induced polarization signals. The reconstruction can be an important consistency test on the puzzles of CMB anomalies, especially for the low-quadrupole and axis-of-evil problems reported in Wilkinson Microwave Anisotropy Probe and Planck data.

Polarization effects of unconsolidated sulphide-sand-mixtures

Due to the increasing demand for some metals the investigation of abandoned mine waste dumps for the potential reuse of ore mining residues becomes more important. This study examines the suitability of the spectral induced polarization (SIP) method to distinguish different ores in the mine dumps and evaluate the deposited amounts. We investigated SIP characteristics of four sulphides: pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS) and sphalerite (ZnS). Laboratory measurements on fully saturated synthetic ore-sand-mixtures (FeS2, PbS, ZnS) with three different grain radii (between 31μm and 500μm), three different ore concentrations (0.5vol.-%, 2vol.-%, 6vol.-%) and with different electrical conductivities of the pore fluid (between 25mS/m and 400mS/m, sodium chloride) for pyrite- and chalcopyrite-sand mixtures have been carried out. A new four-point sample holder for precise and reproducible measurements of the unconsolidated mineral-sand mixtures has been developed. The measurements were done at constant temperature of 20∘C within a frequency range from 1mHz to 45kHz using a high-accuracy impedance spectrometer. Several trends for the induced polarization signature have been observed. First, the polarization signal increases with higher ore mineral content. Second, both phase amplitude and peak frequency increase with decreasing grain radius. Third, the frequency of the phase maximum is shifted to higher values for increasing fluid conductivity. Fourth, all ores showed similar phase characteristics, solely sphalerite indicated lower phase magnitude. By fitting the IP spectra on basis of a Cole–Cole model, the parameters chargeability (m) and time constant (τ) have been derived. The following relations were confirmed: 1) chargeability rises with increasing ore mineral concentration. 2) The time constant increases with increasing grain radius. Ore-specific quantities are determined by these relations. The results show that conclusions about the ore mineral content, grain radius and fluid conductivity can be derived from laboratory SIP measurements. The method seems to be suitable to identify sulphide minerals in sandy mixtures but a differentiation between the different types of ore minerals remains a challenging task. Nevertheless, more investigations are required to improve the reliability of these findings towards a field scale application.

Discrimination of parahydrogen induced polarization signals with J-spectra acquisition in poorly hyperpolarized samples

The application of parahydrogen for the generation of hyperpolarization has increased continuously during the last years. When the chemical reaction that deposits the parahydrogen atoms into the target molecule is carried out following the PASADENA protocol an anti-phase signal is obtained, with a separation of the resonance lines of only a few Hz. Signal cancelation can be produced by line broadening due to magnetic field inhomogeneities or by the superposition with thermal signals. In this work we show that the acquisition of a J-spectrum has a double effect of enhancing spectral resolution and separating PHIP from thermal contributions even in systems where only a very small amount of hyperpolarization can be achieved.

On the spectral induced polarization signature of soil organic matter

Although often composing a non-negligible fraction of soil cation exchange capacity (CEC), the impact of soil organic matter (OM) on the electrical properties of soil has not been thoroughly investigated. In this research the impact of soil OM on the spectral induced polarization (SIP) signature of soil was investigated. Electrical and chemical measurements for two experiments using the same soil, one with calcium as the dominant cation and the other with sodium, with different concentration of OM were performed. Our results show that despite the high CEC of OM, a decrease in polarization and an increase in relaxation time with increasing concentration of OM is observed. For the soil with calcium as the dominant cation, the decreases in polarization and the increase in relaxation time were stronger. We explain these non-trivial results by accounting for the interactions between the OM and the soil minerals. We suggest that the formation of organo-mineral complexes reduce ionic mobility, explaining both the decrease in polarization and the increase in relaxation time. These results demonstrate the important role of OM on SIP response of soil, and call for a further research in order to establish a new polarization model that will include the impact of OM on soil polarization.

The effect of free-phase NAPL on the spectral induced polarization signature of variably saturated soil

[1] In this study, the influence of a free phase nonaqueous phase liquid (NAPL), decane, on the soil's SIP signature was experimentally investigated. The complex electrical conductivity was determined using the SIP measurement system and compared between two main treatment types: clean and decane contaminated. Complementary chemical and temporal measurements were conducted. The results show a clear decrease in the imaginary part of the complex conductivity for the decane contaminated soil. Moreover, a shift of the relaxation frequency was observed for the contaminated soil. Our chemical analysis suggests that there was no change in the chemical composition of the Stern layer, and clearly, the grain size distribution did not change as well. Therefore, these results are attributed to membrane polarization. The decane addition to the unsaturated porous media changes the pore-scale liquid phase distribution, thus affecting membrane polarization. Further, the electrical signature is a time-related process associated with liquid phase arrangement time. The findings of this study can enable a better understanding of the SIP response for soils contaminated with free-phase organic compounds.

The analysis on IP signals in TEM response based on SVD

During transient electromagnetic method (TEM) exploration of a copper mine, we detected the late-channel TEM signal reversal phenomenon (a voltage change from positive to negative) caused by the influence of the induced polarization (IP) effect, which affects the depth and precision of the TEM detection. The conventional inversion method is inefficient because it is difficult to process the data. In this paper, the Cole-Cole model is adopted to analyze the effect of Dc resistivity, chargeability, time constant, and frequency exponent on the TEM response in an homogeneous half space model. Singular Value Decomposition (SVD) is used to invert the measured TEM data, and the Dc resistivity, chargeability, time constant and frequency exponent were extracted from the measured TEM data in the mine area. The extracted parameters are used for interpreting the detection result as a supplement. This reveals why the TEM data acquired in the area has a low resolution. It was found that the DC resistivity and time constant do not significantly change the results, however, the chargeability and frequency exponent have a significant effect. Because of these influences, the SVD method is more accurate than the conventional method in the apparent resistivity profile. The area of the copper mine is confined accurately based on the SVD inverted data. The conclusion has been verified by drill and is identical to the practical geological situation.

Spectral induced polarization signature of soil contaminated by organic pollutant: Experiment and modeling

The spectral induced polarization (SIP) signature of soil contaminated with organic pollutant was studied. Using a flow column experiment, the effect of crystal violet (CV, a polar organic pollutant) on the temporal change of the SIP response over a broad frequency range (1 mHz to 45 KHz) was determined. Complimentary measurements were used to determine the effect of CV on the chemical composition of both the pore water and the solid surface. In addition, analysis of the experimental results was carried out by using both chemical complexation and induced polarization models. Our results shows that adsorption of CV to the mineral surface resulted in release of inorganic ions to the soil solution, increasing the solution electrical conductivity and therefore also the real part of the complex conductivity. Despite the increase in the real part of the complex conductivity, the imaginary part of the complex conductivity decreased with increasing concentration of adsorbed CV. Using the Revil induced polarization model, we were able to show that the contribution of the adsorbed CV to the polarization of the soil is negligible, and that the main process affecting the polarization is the decrease in the density of the inorganic surface species. The results of this study can be used to better interpret SIP signature of soils contaminated by organic compounds.

COSMIC MICROWAVE BACKGROUND INDUCED POLARIZATION FROM SINGLE SCATTERING BY CLUSTERS OF GALAXIES AND FILAMENTS

We present light-cone-integrated simulations of the cosmic microwave background (CMB) polarization signal induced by a single scattering in the direction of clusters of galaxies and filaments. We characterize the statistical properties of the induced polarization signals from the presence of the CMB quadrupole component (pqiCMB) and as the result of the transverse motion of ionized gas clouds with respect to the CMB rest frame (p?2 t SZ). From adiabatic N-body/hydrodynamic simulations, we generated 28 random sky patches integrated along the light cone, each with about 0.86?deg2 and angular resolution of 6''. Our simulation method involves a box-stacking scheme that allows to reconstruct the CMB quadrupole component and the gas physical properties along the line of sight. We find that the linear polarization degree in the logarithmic scale of both effects follows approximately a Gaussian distribution and the mean total signal is about 10?8 and 10?10 for the pqiCMB and p?2 t SZ effects, respectively. The polarization angle is consistent with a flat distribution in both cases. From the mean distributions of the polarization degree with redshift, the highest peak is found at z 1 for the induced CMB quadrupole and at z 0.5 for the kinematic component. Our results suggest that most of the contribution for the total polarization signal arises from z 4 for the pqiCMB and z 3 for p?2 t SZ. The spectral dependency of both integrated signals is strong, increasing with the frequency, especially in the case of the p?2 t SZ signal, which increases by a factor of 100 from 30?GHz to 675?GHz. The maxima values found at the highest frequency are about 3 ?K and 13 ?K for the pqiCMB and p?2 t SZ, respectively. The angular power spectra of these effects peak at large multipoles ? > 104, being of the order of 10?5 ?K2 for pqiCMB polarization and 10?7 ?K2 for the p?2 t SZ effect. Therefore, these effects will not be a relevant source of contamination for measurements of the primary polarization modes, and at larger multipoles of roughly ? > 40, 000, pqiCMB may be the dominant component over the primary and lensing signals.

A new model for the spectral induced polarization signature of bacterial growth in porous media

The complex conductivity of porous materials and colloidal suspensions comprises two components: an in‐phase conductivity associated with electromigration of the charge carriers and a quadrature conductivity associated with the reversible storage of the charges at some polarization length scales. We developed a quantitative model to investigate the frequency domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (α polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and α polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to their cation exchange capacity. The mobility of the counterions in this Stern layer is found to be very small (4.7 × 10−10 m2 s−1 V−1 at 25°C). This implies a very low relaxation frequency for the αpolarization of the bacteria cells (typically around 0.1–5 Hz), in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred nonintrusively from time‐lapse frequency domain induced polarization data.

Spectral Induced Polarization Signatures of Hydroxide Adsorption and Mineral Precipitation in Porous Media

The spectral induced polarization (SIP) technique is a promising approach for delineating subsurface physical and chemical property changes in a minimally invasive manner. To facilitate the understanding of position and chemical properties of reaction fronts that involve mineral precipitation in porous media, we investigated spatiotemporal variations in complex conductivity during evolution of urea hydrolysis and calcite precipitation reaction fronts within a silica gel column. The real and imaginary parts of complex conductivity were shown to be sensitive to changes in both solution chemistry and calcium carbonate precipitation. Distinct changes in imaginary conductivity coincided with increased hydroxide ion concentration during urea hydrolysis. In a separate experiment focused on the effect of hydroxide concentration on interfacial polarization of silica gel and well-sorted sand, we found a significant dependence of the polarization response on pH changes of the solution. We propose a conceptual model describing hydroxide ion adsorption behavior in silica gel and its control on interfacial polarizability. Our results demonstrate the utility of SIP for noninvasive monitoring of reaction fronts, and indicate its potential for quantifying geochemical processes that control the polarization responses of porous media at larger spatial scales in the natural environment.

The effect of NAPL on the electrical properties of unsaturated porous media

SUMMARY The spectral induced polarization signature of porous media contaminated with non-aqueous phase liquid (NAPL) was studied. Using an accurate measurement system, the complex electrical conductivity of unsaturated porous media contaminated with either diesel fuel or motor oil at a constant water saturation was determined. Counter intuitively, the results show that replacing air with NAPL increases the real part of the complex conductivity of unsaturated porous media. We interpret the results in terms of electrochemical polarization, and suggest that polar compounds contained in the NAPL adsorb to the mineral surface leading to release of inorganic ions to the pore water, which affects both the fluid and surface conductivity. In addition, we observed a decrease in the polarization followed by further addition of NAPL, which we relate to a lower mobility of the adsorbed polar compound. This study allows a better understanding of the electrical signature of NAPL contaminated porous media, especially in variably saturated conditions.

Induced polarization signatures of cations exhibiting differential sorption behaviors in saturated sands

Two sets of experiments were designed to understand the change in induced polarization associated with the sorption of copper and sodium, exhibiting distinct sorption behavior on a silica sand. A sand column experiment was first performed to see the change in the complex conductivity during the advective transport of a copper sulfate solution. A second set of experiments was done with the sand at equilibrium with various solutions of NaCl and CuSO4. In the first experiment, the copper sulfate solution replaced a sodium chloride solution, keeping the electrical conductivity of the solution nearly constant. During the passage of the copper sulfate solution, the apparent phase angle decreased from 3 ± 0.2 to 0.5 ± 0.2 mrad, while the magnitude of the conductivity of the sand remained nearly constant. A quantitative model is proposed to explain the change in the complex conductivity as a function of the chemistry assuming a polarization mechanism associated with the Stern layer (the inner part of the electrical double layer coating the water‐mineral interface). The Stern layer polarization is combined with a complexation model describing the competitive sorption of copper and sodium at the pore water interface. The change of the phase lag is directly associated with the ion exchange between sodium and copper at the surface of the silica grains. The explanation of the observed phase differences between Na and Cu relies on their different complexation behaviors, with Na being loosely absorbed, while Cu forms relatively strong complexation with both inner (monodentate) and outer sphere (bidentate) complexes. The replacement of Cu2+ by Na+ is less favorable; therefore, the kinetics of such a replacement is much slower than for the opposite replacement (Na+ by Cu2+). We were able to reproduce the changes in the phase lags at thermodynamic equilibrium near the relaxation frequency and in the frequency domain. These measurements and modeling results open the door to the quantitative interpretation of spectral induced polarization data in the field in terms of quantification of the sorption processes.