Induced Polarization: A Preliminary Study of Its Chemical Basis

Abstract

An investigation of the effect that the in‐situ solution chemistry would have on the induced‐polarization phenomena was carried out by means of laboratory studies of the electrode impedances of metallic and sulfide minerals. Reaction rate theory shows that this effect is largely due to the impedance associated with the diffusion of the ions involved in the charge transfer reaction to and from the reaction sites. This impedance is inversely proportional to the concentration of the reacting ions and inversely proportional to the square root of the frequency. Impedance measurements were made with different concentrations of a variety of ions in order to identify the active ion species. The ion concentrations were controlled by doping and by excursions in Eh and pH. These measurements showed that cupric and sulfide ions are active in the charge transfer reaction and control the electrode impedances whenever their concentrations exceed [Formula: see text]. None of the other common anions and cations tested appeared active. A background impedance level was found which was relatively insensitive to the solution chemistries tested. These impedances varied somewhat with the type of mineral tested, but generally ran between 2000 and [Formula: see text] at 1 radian/sec. The identity of these background reactions is still an open question.

Using complex resistivity imaging to infer biogeochemical processes associated with bioremediation of an uranium-contaminated aquifer

“…We suggest that this decrease could be related to the depletion of electroactive ions (primarily dissolved Fe(II)), the absence of which manifests itself as a lower overall phase response, as suggested by Williams et al [2009]. The importance of electroactive ions in controlling the polarization magnitude at the metallic interface has been extensively discussed in previous studies [Angoran and Madden, 1977;Wong, 1979;Merriam, 2007].…”

“…Further studies have demonstrated a proportional correlation between the size and volumetric enrichment of the metallic minerals and a characteristic frequency response (described by a characteristic relaxation time) [ Pelton et al , 1978; Olhoeft , 1985]. Recent laboratory studies have demonstrated a linear correlation between the imaginary component of the complex conductivity and the total metallic surface area of precipitated metallic minerals [ Slater et al , 2005, 2007], with other studies attributing changes in the frequency‐dependent responses to variations in the concentration of electroactive ions in the pore fluid [ Angoran and Madden 1977; Wong , 1979; Williams et al , 2005] or spatiotemporal changes in location of the mineralization [ Ntarlagiannis et al , 2005a]. Given the multitude of condition‐dependent factors controlling the complex resistivity response, further studies are warranted.…”

Geophysical Monitoring of Coupled Microbial and Geochemical Processes During Stimulated Subsurface Bioremediation

“…S11; R ct 1 ), facilitating greater rates of electron transfer and a phase response reflective of a diffusion-controlled process (13,14,21). Under such conditions, the composition of the mineral(s) facilitating electron transfer is of minimal importance and in agreement with recently reported results (14) and previous studies investigating the electrochemical nature of the IP response (13).…”

“…Among these methods, the induced polarization (IP) technique has shown excellent sensitivity to enhanced microbial activity (5,7,(9)(10)(11)(12). Such studies, combined with theoretical investigations exploring the electrochemical mechanisms underlying the IP response (13,14), suggest it is well suited to monitoring stimulated subsurface bioremediation under field conditions. Analogous to laboratory electrochemical approaches, the IP method involves injection of variable frequency currents into the ground and the measurement of resulting voltage potentials via electrodes located above and below the ground surface.…”

On the pore water chemistry effect on spectral induced polarization measurements in the presence of pyrite

“…Even with such simplifications, the Wong model still contains eight parameters with some of them dependent on others. For instance, (1) the diffusion coefficient (D) is considered the same for both the redox-active and redox-passive ions in the electrical double layer (EDL), whilst the passive/active ion concentration ratio is considered very large and the redox-active ions are engaged in diffusive mass transport only; (2) the equilibrium current density (i o ) associated with the transfer of charge (e -) at the metal-electrolyte interface is complicated to define accurately due to the various possible redox reactions, i.e., i o will depend on every specific redox reaction between ions and type of metallic mineral (Angoran and Madden, 1977;Klein and Shuey, 1978). Consequently, i o is directly related to the magnitude of the electrochemical reaction modelling parameters (α, β), and thus to the specific surface conductance of metallic particles, accounting for the interfacial charge storage or capacitive properties; (3) the parameter defining the distance from the metallic mineral surface to the outer Helmholtz plane (l), i.e., the thickness of the Stern layer, directly affects the α parameter and thus the specific surface conductance.…”