Spectral Induced Polarization Method Research Articles

Monitoring of copper adsorption on biochar using spectral induced polarization method

Copper contaminant generated from mining and industrial smelting poses potential risks to human health. Biochar, as a low-energy and cost-effective biomaterial, holds value in Cu remediation. Spectral Induced Polarization (SIP) technique is employed in this study to monitor the Cu remediation processes of by biochar in column experiments. Cation exchange at low Cu2+ concentrations and surface complexation at high Cu2+ concentrations are identified as the major mechanisms for copper retention on biochar. The normalized chargeability (mn) from SIP signals linearly decreased (R2 = 0.776) with copper retention under 60 mg/L Cu influent; while mn linearly increases (R2 = 0.907, 0.852) under high 300 and 700 mg/L Cu influents. The characteristic polarizing unit sizes (primarily the pores adsorbing Cu2+) calculated from Schwartz equation match well with experimental results by mercury intrusion porosimetry (MIP). It is revealed that Cu2+ was driven to small pores (∼3 μm) given high concentration gradient (influent Cu2+ concentration of 700 mg/L). Comparing to activated carbon, biochar is identified as an ideal adsorbent for Cu remediation, given its high adsorption capacity, cost-effectiveness, carbon-sink ability, and high sensitivity to SIP responses – the latter facilitates its performance assessment.

Geophysical signatures of soil AFFF contamination from spectral induced polarization and low field nuclear magnetic resonance methods

Few field methods are available for characterizing source zones impacted with aqueous film forming foam (AFFF). Non-invasive geophysical characterization of AFFF source zone contamination in situ could assist with the delineation and characterization of these sites, allowing for more informed sampling regimes aimed at quantifying subsurface poly- and perfluoroalkyl substances (PFAS) contamination. We present initial results from the investigation of the sensitivity of two existing surface and borehole-deployable geophysical technologies, spectral induced polarization (SIP), and low field nuclear magnetic resonance (NMR), to soils impacted with AFFF. To investigate the sensitivity of these methods to AFFF-impacted soil, bench-scale column experiments were conducted on samples consisting of natural and synthetic soils and groundwater. While our findings do not show strong evidence of NMR sensitivity to soil PFAS contamination, we do find evidence that SIP has sufficient sensitivity to detect sorption of AFFF constituents (including PFAS) to soils. This finding is based on evidence that AFFF constituents associated with the pore surface produce a measurable polarization response in both freshly impacted synthetic soils and in soils historically impacted with AFFF. Our findings encourage further exploration of the SIP method as a technology for characterizing contaminant concentrations across AFFF source zones.

Detection of Iron Disulfide Materials in Geological Porous Media Using Spectral Induced Polarization Method

Summary Iron sulfide (FeS) scale is a known problem that can significantly impact oil and gas (O&G) production. However, current monitoring methods cannot detect the problem at early stages, not until it is too late for any meaningful remedial action. Spectral induced polarization (SIP) is an established geophysical method increasingly used in near-surface environmental applications. The unique characteristics of the SIP method, mainly the sensitivity to both bulk and interfacial properties of the medium, allow for the potential use as a characterization and monitoring tool. SIP is particularly sensitive to metallic targets, such as FeS, with direct implications for the detection, characterization, and quantification of FeS scale. In a column setup, various concentrations of pyrite (FeS2), a common form of FeS scale, within calcite were tested to examine the SIP sensitivity and establish qualitative and quantitative relationships between SIP signals and FeS2 properties. The concentration of FeS2 in the samples directly impacts the SIP signals; the higher the concentration, the higher the magnitude of SIP parameters. Specifically, the SIP method detected the FeS2 presence as low as 0.25% in the bulk volume of the tested sample. This study supports the potential use of SIP as a detection method of FeS2 presence. Furthermore, it paves the way for upcoming studies utilizing SIP as a reliable and robust FeS scale characterization and monitoring method.

Research on linear inversion of SIP using the Debye decomposition method

Spectral-induced polarization data can provide information regarding the polarization properties of underground media. The characteristic relaxation time of polarized media is related in part to the composition of rocks and minerals and porosity. Therefore, the spectral-induced polarization method is widely used to obtain underground lithology/structure, hydrogeology, and geochemical data. Because the Debye decomposition method can flexibly fit the spectrum shape, it is being increasingly used to analyze the relaxation time distribution of spectral-induced polarization (SIP) signals. In this study, the Debye decomposition method was used to directly invert the relaxation time distribution curve from SIP data to extract the characteristic relaxation time of the target. First, we discuss the Debye decomposition method in terms of its physical principle and show the relationship between the multi-Cole–Cole model and Debye decomposition through a numerical simulation. We then used the linear inversion method to invert the synthetic and measured data based on the Debye decomposition parameterization and verify the effectiveness of the inversion. Compared with the numerical simulations of several models, we proved that the parameters of the Cole–Cole model are strongly correlated. Additionally, the inversion results show that the linear inversion method is suitable for inverting the Debye decomposition and that expanding the range of the relaxation time in the Debye decomposition can effectively alleviate the influence of the truncation error on inversion.

Analysis of Transient Characteristics of Induced Polarization in Innovative Mineral Exploration Solutions (from Case Studies of Gold Deposits)

Abstract—The paper discusses current state of the spectral approach to analysis of induced polarization (IP), its possibilities and limitations, along with directions for the method development. Reviewed are the main methods and approaches for estimation of spectral IP parameters and their specific features. Our practical experiments have shown the advantages of analysis of transient IP characteristics over standard approaches to the IP data analysis and processing. Results of the standard and spectral approaches application to analysis of IP data when solving mineral exploration problems at the Maletoyvayam gold deposit (Kamchatka Peninsula) and the Yasnoe gold occurrence (Taimyr Peninsula) are compared. Here, we demonstrate that low efficiency of works is erroneously regarded as one of the main factors hindering a broad adoption of the spectral IP method in mineral exploration activities. Rather, it is a lack of automated techniques for analysis of transient IP characteristics. We propose a new approach to spectral analysis of IP data, based on the algorithms for image recognition of a reference object, and describe pioneering efforts of its practical application.

The influence of roots on soil's electrical signature

Detecting and monitoring roots and their activity in soil is of great importance as it controls water and nutrient transport, soil carbon dynamics, and soil microorganisms. However, roots are hidden in the soil, they are heterogeneous, and dynamics; therefore, in-situ measurements of their properties and the involved processes are highly challenging. The spectral induced polarization (SIP) is a geophysical method that allows noninvasive mapping of subsurface properties and processes. Recently, the quadrature conductivity (measured with the SIP method) was positively correlated with root biomass and root surface area in hydroponics. Unlike the nonpolarized hydroponic solution (at frequencies <1000 Hz, relevant to the SIP method), the soil is a polarizable medium, and various soil-root interactions (e.g., water and nutrient uptake, root exudation, etc.) are expected to influence the soil SIP signature. Therefore, this research aimed to assess the impact of roots on the SIP signature of soil. We conducted a series of experiments in which we measured and monitored the SIP signature of soil in which wheat plants are growing. Supplementary measurements included soil water content, pore water salinity, and root biomass. Our results show that, unlike in hydroponic, there is an inverse relationship between root biomass and quadrature conductivity. Most of the decrease in the quadrature conductivity was associated with the water content decrease. We suggest that the unexplained decline in the quadrature conductivity is associated with various soil-root interactions, such as selective uptake of nutrients and root exudation, but further research is needed.

SOME PROBLEMS OF ELECTRICAL GEOPHYSICAL PROSPECTING METHODS USED FOR EXPLORATION OF ORE DEPOSITS

Electrical geophysical prospecting methods are widely used at different stages of geological exploration. In the last two decades, new computer technologies and satellite navigation systems were successfully introduced in the geophysical industry. As a result, exploration technologies have improved, and new geophysical methods have been developed, such as electrical resistivity tomography (ERT) and spectral induced polarization (SIP) methods. An important role in ore geophysics is played by magnetotelluric (MT) methods. In this article, we focus on the issues of methodology and interpretation of electrical prospecting data for solving ore exploration problems. Special attention is paid to the induced polarization (IP) method that is most widely used in mineral exploration and mining industry as one of the most important and most dynamically developing techniques of ore geophysics. In addition, the issues of correct choices of survey scales and the use of automatic 2D and 3D inversion programs are considered.

Layered soil exploration based on the time domain spectral induced polarization method

Soil stratification is the basic problem of soil development and utilization in the farmland, which can be used as a reference for later development and planting. Traditional soil stratification method is inefficient and needs to introduce new methods and techniques. In this paper, time domain spectral induced polarization method was introduced to carry out electric sounding exploration for the certain soil, and the observed data were processed and interpreted by using half-life time and deviation degree. The results show that the application of time domain spectral induced polarization method in soil stratification is feasible, and the half-life time and deviation degree are effective as interpretation parameters. The measured results and conclusions of this work can provide a basis for related research and the reference for relevant work.

Validation of complex electrical properties of concrete affected by accelerated alkali-silica reaction

Alkali-silica reaction (ASR) is one of the most damaging problems with chemical alteration causing mechanical and physical changes in the concrete properties. Therefore in order to control concrete durability, a fast, non-destructive method aiming at detecting ASR is needed before an advanced stage (external visible signs) especially in field investigation. This paper focuses on the validation of the complex electrical measurements using spectral induced polarization (SIP) to monitor ASR development in concrete. Significant relationships were studied between the electro-chemical and physico-mechanical properties of concrete affected by ASR over time (22 weeks in accelerated conditions). Non-destructive methods (SIP, ultrasonic pulse velocity, expansion, and mass variation) and destructive testing (compressive strength, modulus of elasticity, petrographic examination) were used to monitor concrete mixtures (reactive and reference) submitted to accelerated laboratory test conditions. A significant evolution of SIP responses (phase lag, total chargeability, mean relaxation time) was found in the concrete specimens affected by ASR over the low frequency range. This observation was confirmed by other measurements specially expansion, UPV, modulus of elasticity, and petrographic analysis. Finally, this paper suggests SIP method as an effective non-destructive technique to monitor ASR development.

Time-lapse monitoring of an electrokinetic soil remediation process through frequency-domain electrical measurements

The electrokinetic (EK) method is an emerging technique for soil remediation, even though a monitoring system of the contaminant removal through geophysical methods has not been developed yet. In this paper, frequency-domain time-lapse measurements are used on heavy-metal contaminated sediments for monitoring an EK remediation process in a small-scale measuring cell. Our goal is to monitor the development of the electrokinetic process within the sediment and to evaluate the total time needed for the treatment. In fact, frequency-domain electrical monitoring provides complex resistivity spectra at different time steps that can be correlated to changes in the physical properties of the sediments. We perform laboratory spectral induced polarization (SIP) measurements on different samples before, during and after the EK treatment, using different electrolyte solutions (acids and tap water), commonly employed in EK remediation. Direct-current measurements (resistivity and chargeability) were also acquired on one sample for testing the reliability of the system by a comparison with a widespread commercial instrumentation for field measurements.Results indicate that resistivity is a diagnostic parameter as long as it is linked to changes in water saturation, pH and ionic concentration and not to the percentage of metal extraction. The resistivity exhibited well-defined signatures as a function of time that changes depending on the conditioning agent and the grain size distribution. These peculiarities were used to understand the physical processes occurring within the cell and consequently to assess the effectiveness of the electrokinetic treatment.Conversely, the polarization effect was negligible using acids as conditioning agents at the electrolyte chambers. Therefore, the SIP method is not effective under these conditions, being the polarization effect significant only when tap water was used at both ends of the measuring cell. In this case, we were able to correlate changes in water saturation with the time-shift observed on relaxation time distributions (RTDs) after inversion of SIP data and to observe, using normalized chargeability, that polarization is stronger at high pH values.On these basis, resistivity is suitable to monitor the development of the remediation, to optimise the energy levels required for treatment and to assess the end time of the EK process (time when metal mobilization ends). In fact, the end time of treatment can be associated with the time at which resistivity becomes stable. This time is highly dependent on the particular working conditions and sediment grain size as demonstrated by our experiments.

Application of spectral induced polarization for characterizing surfactant-enhanced DNAPL remediation in laboratory column experiments

The widespread presence of entrapped dense non-aqueous phase liquid (DNAPL) in the subsurface poses a continuing challenge to groundwater remediation. Cost-effective and high-resolution subsurface characterization is a critical issue for further DNAPL recovery due to the complexity of DNAPL source zone architecture (SZA). Geophysical techniques provide a noninvasive, spatially continuous and cost-effective way for monitoring the DNAPL remediation process. In particular, the spectral induced polarization (SIP) method has shown great potential in environmental problems. In this study, we performed real-time SIP measurements on DNAPL contaminated soil in columns to quantitatively assess the ability of SIP method for monitoring surfactant-enhanced DNAPL remediation process. Chemical data was simultaneously collected during the remediation process to verify the results obtained by SIP method. Taking account into the variations of subsurface environment, we conducted a series of column flushing experiments under different flow rate, surfactant concentrations and fluid salinities. The results highlight that SIP method is able to effectively monitor the DNAPL remediation process, as well as to evaluate the remediation efficiency under different conditions. The variations in the flow rate, the concentration of surfactant and the salinity of pore water not only affect remediation effectiveness, but also have an impact on the SIP signatures. This study shows that SIP performs better for monitoring DNAPL remediation at a relatively low flow rate of ~ 0.4 m/d, low surfactant concentration of 5000 mg/L and high salinity of 1.0 S/m, with an error of saturation estimation (RMSES) <0.1.

Relationship between wheat root properties and its electrical signature using the spectral induced polarization method

AbstractMeasuring root properties, the “hidden half” of the plant, is challenging due to their heterogeneous and dynamic nature. A promising method for noninvasive mapping of roots and their activity, spectral induced polarization (SIP), has been introduced. However, measurements of root properties together with their SIP responses are missing, limiting the interpretation of a root's SIP signature. In this study, we coupled SIP measurements of roots in hydroponic solution with measurements of root biomass, surface area, and diameter. Furthermore, we monitored the SIP response of roots poisoned by cyanide, which results in depolarization of the root's cell membrane potential. We found a linear correlation between root biomass and surface area, and the low‐frequency electrical polarization. In addition, we demonstrate the relationship between root cell membrane potential and root polarization. Based on the results, we suggest that in comparison with the stem‐based approach used by other researchers, the polarization in the contact‐free method used in this study is related to the external surface area of the root and external architectural structures such as root diameter and root hair. Overall, a direct link between root properties and their electrical signature was established.

Measuring electrical properties of mortar and concrete samples using the spectral induced polarization method: laboratory set-up

Abstract Electrical impedance spectroscopy (EIS), also known as Spectral Induced Polarization (SIP) has proven to be a successful non-destructive technique able to characterize the chemical and physical properties of a complex structure (concrete, rocks, and soil) under various environmental conditions. Because this technique aims to measure small amplitude signals, it can easily be influenced by parasitic effects which are not representative of the intrinsic properties of the investigated material. The purpose of this paper is to validate the resolution of our experimental methodology as a preliminary step to ensure an accurate measurement of the bulk complex resistivity response of concrete samples within a wide frequency range (1.43 mHz–20 kHz). A cement mortar sample is first used as a homogeneous (isotropic) material to improve the sample holder design for reducing the errors and controlling the external parameters (such as coupling effect, geometric factor, contact impedance, electrode polarization) during the laboratory measurements. Also, the performance and installation of the measuring components such as the electrodes (current and potential) and the sample holder design are assessed. The specimen dimensions and designs are selected based on a sample standard size that will be used to determine the physico-mechanical properties of concrete (compressive strength, modulus of elasticity, ultrasonic pulse velocity, length variation). The examinations are performed in parallel with the SIP measurement on the same sample. The accuracy of our measurement setup is then validated using aluminum-bronze plates bonded to the sample using a conductive gel to transmit electric current with a density less than 10 - 3  A m−2. The results showed that by controlling the sponge moisture in the Ag/AgCl non-polarizable voltage electrodes, our SIP measurement system is able to measure the phase lag with an error smaller than 1 mrad over a frequency range from 1.43 mHz to 20 kHz.

Geophysical Monitoring of Hydrocarbon Biodegradation in Highly Conductive Environments

AbstractNatural attenuation is very often the remediation method of necessity, rather than choice, for beach environments impacted by offshore exploration/drilling accidents. Robust methods that can be efficiently utilized in difficult to access and ecologically sensitive areas are needed for the long‐term monitoring of such degradation processes. A prime candidate for such a monitoring tool is the spectral induced polarization (SIP) method, a geophysical technique successfully used for characterization and monitoring of hydrocarbon degradation in freshwater environments. In this laboratory experiment the SIP method successfully monitored the natural degradation of beach sediments impacted by the Deepwater Horizon oil spill. Using the SIP, we were able to differentiate between biotic (e.g., microbial driven) and abiotic (e.g., dilution) degradation processes and infer degradation rates. To our knowledge this is the first effort to use the SIP method as a monitoring aid in high salinity environments.

New spectral-induced polarization measurement with low cost and high efficiency

Spectral induced polarization (SIP) measurement requires synchronous current acquisition and real-timetransmission devices or precise phase-measuring apparatus. To carry out SIP investigations in the absence of these auxiliary devices, a new SIP measurement has been developed in this research. The new method uses high-accuracy phase-calculation technology based on all-phase spectrum analysis (APSA) to obtain the initial phase of the emission current and uses time information recorded in the file header of the voltage data file and the ‘Frequency-Time Table’ of the emission current to calculate the current phase information at any given moment. The phase-calculation method for the voltage data was the same as that used for the current initial phase. Subsequently, the phase of the complex resistivity was obtained by subtracting the current phase from the voltage phase, and the amplitude was obtained by normalization. Simulation tests showed that the algorithm was superior for absolute phase measurement compared with other spectrum analysis methods and confirmed that the accuracy of the new method was equal to that of the measurement that collects voltage and current synchronously. Indoor and field tests showed that the new APSA-based SIP method can successfully measure the complex resistivity without a synchronous current- or phase-measuring device. Moreover, this method reduces the requirement for synchronization of the transmitter and receiver.

Experimental Study of Spectral Induced Polarization Response Based on Laboratory Measurement

The spectral induced polarization (SIP) method can provide apparent complex resistivity based on measurements of multi frequency. SIP method also can provide more detail information about physical properties of rocks and minerals because SIP can give spectral parameters or Cole-Cole parameters such as, changeability (m), time constant (τ) and frequency dependence (c). An Experimental study in laboratory has been conducted to knowing the SIP response of some test sample. The measurement system is built with digital oscilloscope Pico ADC-100 as device for sampling the input and output voltage. Amplifier is used to doubled up the signal and input differential. The range frequency of measurement is 10−2 Hz - 103 Hz. Porouspot Cu − CuSO4 is used to minimize the polarization at potential electrode. A Matlab listings is used to calculate the response of impedance and phase. The result from calibration that used the parallel circuit RC indicate that the measurement system was good. SIP response of porous model indicate that the response form an asymptotic resistivity, and the peak of phase is in the range frequency where the dispersion happen. The result also indicate that resistivity of small grain size model is larger than the big grain size model. Result from sample of mineralized rocks did not indicate a perfect SIP response, it is influenced by the contact between mineral and water was minimum.

Sensitivity of galvanic and inductive Induced Polarization methods to the Cole-Cole parameters

The Induced Polarization (IP) method is recognized as a valuable geophysical tool for resource exploration and environmental studies. In many of these studies, the Cole-Cole relaxation expression has been used to describe how subsurface resistivity depends on the frequency of the fields. In this study, we estimate the resolution of the Cole-Cole parameters of simple models measured by three geophysical methods. We compare the Spectral IP (SIP), the time-domain or Transient IP (TIP), and the in-loop Transient Electromagnetic (TEM) methods. In the first two, a current is injected directly into the ground (galvanic), while in the last one, the current is created by electromagnetic induction. The sensitivities and parameter uncertainties are estimated with a Singular Value Decomposition of the sensitivity matrix for a series of homogeneous and two-layered models. In general, the SIP method gives the best parameter resolutions, followed by those of the TIP and TEM methods. Of the four Cole-Cole parameters, generally the time constant is the least well resolved. The parameters are better resolved when the time constant is less than 10 s. When the polarizable medium is buried under a non-polarizable layer, the uncertainties of the TEM method show an important increase.

Complex conductivity of oil-contaminated clayey soils

Spectral induced polarization (SIP) is considered as a promising tool in environmental investigations. However, few works have done regarding the electrical signature of oil contamination of clayey soils upon induced polarization. Laboratory column experiments plus one sandbox experiment are conducted in this study to investigate the performances of the SIP method in oil-contaminated soils. First, a total of 12 soils are investigated to reveal the influences of water and soil properties on the saturation dependence of the complex conductivity below 100 Hz. Results show that the magnitude of the complex conductivity consistently decreases with decreasing water saturation for all soils samples. The saturation n and quadrature conductivity p exponents tend to increase slightly with increasing water salinity when using a linear conductivity model. The saturation exponent increases marginally with the cation exchange capacity (CEC) and the specific surface area (Ssp) while the quadrature conductivity exponent exhibits a relatively stronger dependence on both CEC and Ssp. For the low CEC soil samples (normally ≤10 meq/100 g), the quadrature conductivity exponent p correlates well with the saturation exponent n using the relationship p = n−1. SIP method is further applied in a sandbox experiment to estimate the saturation distribution and total volume of the oil. Results demonstrate that the SIP method has a great potential for mapping the organic contaminant plume and quantifying the oil volume.

Simulation of membrane polarization of porous media with impedance networks

ABSTRACTThe spectral induced polarization method is supposed to have some potential to provide useful information on hydraulic properties of the subsurface. One difficulty for the practical implementation is the simulation of underlying physical processes at the pore scale and their upscaling to hydraulically relevant scales. We extend an existing semi‐analytical membrane polarization model to two‐ and three‐dimensional impedance networks, which are numerically solved to obtain a spectral induced polarization response that can be compared to measured data.The original model consists of two cylinders with different sizes. The model has been shown to be able to reproduce some basic features of spectral induced polarization spectra measured in the laboratory, but it is unable to meet the complexity of macroscopic porous media structures, which can be found within unconsolidated sediments or rocks. To approach realistic pore space geometry, we connect different combinations of cylinders to networks. We treat the smaller of the two cylinders as a pore throat. The pore throat distribution in the network is chosen by matching measured pore throat radii distributions obtained from the mercury injection method. The large cylinder is treated as the (large) pore body, and its radii are associated to the pore throats using existing relationships.We compare the behaviour of the networks with real porous media by using sandstone samples for which both the electrical and petrophysical properties have been measured. We adjust the geometrical parameters of the network, i.e., pore lengths, pore radii, and their relative occurrences, such that they match the measured parameters (specific internal surface area, pore throat distribution, and porosity) of the sandstone samples. The measured spectral induced polarization parameters, like the maximum phase shift and the characteristic relaxation time, are qualitatively consistent with our simulation results.

Spectral induced polarization of Na-montmorillonite dispersions

Montmorillonite (Mt) clays have a high specific surface area and surface charge, which confer them remarkable adsorption properties. Nevertheless, their electrochemical and aggregation behavior are not completely elucidated because of the complexity of their microstructural and interfacial properties. In this work, the conductive and dispersive properties of Na-Mt suspensions of weight fractions 0.5–5.2% were investigated for the first time using the spectral induced polarization method. A four-electrode system was used to reduce errors introduced by electrode polarization and contact resistances. Complex conductivity spectra in the low-frequency range of 0.1Hz to 45kHz were successfully described using a triple layer model of the basal surface of Mt and a complex conductivity model that considers conduction of the diffuse layer and polarization of the Stern layer. Aggregate size distributions were inferred from inverted relaxation time distributions. We found that the negative and permanent surface charge of the basal plane of Na-Mt controls its quadrature (imaginary) conductivity, which is not very sensitive to pH and salinity (NaCl) in the 100Hz to 45kHz frequency range. For lower frequencies, the sudden increase of the quadrature conductivity at the highest salinities was explained by considering coagulation of Na-Mt particles.