Effect of solute concentration on the spectral induced polarization response of calcite precipitation

Abstract

SUMMARY Induced calcite precipitation is used in geotechnics to modify the mechanical and hydrological properties of the underground. Laboratory experiments have shown that spectral induced polarization (SIP) measurements can detect calcite precipitation. However, the results of previous studies investigating the SIP response of calcite precipitation were not fully consistent. This study aims to investigate how the SIP response of calcite depends on solute concentration to explain the differences in SIP response observed in previous studies. A four-phase experiment with SIP measurements on a column filled with sand was performed. In phase I, calcite precipitation was generated for a period of 12 days by co-injecting Na2CO3 and CaCl2 solutions through two different ports. This resulted in a well-defined calcite precipitation front, which was associated with an increase in the imaginary part of the conductivity ($\sigma ^{\prime\prime}$). In phase II, diluted solutions were injected into the column. This resulted in a clear decrease in $\sigma ^{\prime\prime}$. In phase III, the injection of the two solutions was stopped while calcite precipitation continued and solute concentrations in the mixing zone decreased. Again, this decreased $\sigma ^{\prime\prime}$. Finally, the injection rate of the Na2CO3 solution was reduced relative to that of the CaCl2 solution in phase IV. This resulted in a shift of the mixing zone away from the calcite precipitation front established in phase I and an associated decrease of $\sigma ^{\prime\prime}$. These results imply that the SIP response of calcite is highly sensitive to the solute concentration near the precipitates, which may explain previously reported conflicting results.

Pore-Scale Mechanisms for Spectral Induced Polarization of Calcite Precipitation Inferred from Geo-Electrical Millifluidics

“…In the additional experiment where the sample holder was flushed twice with the MgCO3 solution, the injection of MgCO3 solution decreased the imaginary part of conductivity as expected from previous studies 28 and increased the peak frequencies (Figure S13 and S14).…”

“…A first millifluidic calcite precipitation experiment was performed with a total duration of 80 hours using the same solute concentrations as in previous column studies 15,28 . The sample holder was first filled with a 26.2 mM CaCl2 solution.…”

Geophysically based analysis of breakthrough curves and ion exchange processes in soil

“…The effect of soil hydraulic characteristics on its SIP signature has been studied before (e.g., Kruschwitz et al, 2010;Breede et al, 2012;Nordsiek et al, 2016). For example, Kruschwitz et al (2010) examined the low-frequency electrical spectra of a range of natural and artificial porous media with the aim to link the electrical signature to the physical properties of the examined media. They confirmed a significant positive correlation between the electrical polarization and the surface area to pore volume ratio.…”

Advancing measurements and representations of subsurface heterogeneity and dynamic processes: towards 4D hydrogeology

“…This idea remains to be tested in the laboratory and field. Geophysical techniques that have the potential to map and monitor reactive processes, such as Spectral Induced Polarization (SIP), which consists in measuring the phase shift of an alternating electrical signal occurring because of polarization phenomena in the electrical double layer, by mineral precipitation (Leroy et al, 2017), or by the activity of microorganisms (Kessouri et al, 2019) are highly sensitive to pore scale processes and concentration distributions (Izumoto et al, 2020), which make their interpretation challenging but potentially very rewarding. The coupling of geophysical techniques with pore scale imaging techniques, including micro and millifluidics, represents a new avenue of research to understand and quantify the geophysical signature of unresolved pore scale processes (Jougnot et al, 2018;Fernandez Visentini et al, 2021).…”

“…CC BY 4.0 License. the pore space or fracture apertures (Davy et al, 2018), colmatation and erosion processes in streambeds (Partington et al, 2017) or reactive transport inducing changes in the pore space (Izumoto et al, 2020).…”