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

Abstract

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.

Laboratory study of spectral induced polarization responses of magnetite — Fe2+ redox reactions in porous media

“…We note that Ca 2+ , Ni 2+ , and Fe 2+ will also have adsorbed to the surface of silica grains within our samples however, the phase responses associated with silica grains are typically very much smaller than those seen in our study (e.g. Leroy et al, 2008;Zhang et al, 2012), which we thus attribute to the semiconductive magnetite particles. An interpretation of our data based on the responses of magnetite particles is illustrated by the conceptual model shown in Figure 5.…”

“…SIP phase responses have been attributed to several different types of polarization phenomena including those associated with microbial cells and biofilms (Davis et al, 2006), non conductive minerals such as silica Zhang et al, 2012), and (semi)conductive particles such as sulfides Page 6 of 31 Geophysics Manuscript, Accepted Pending: For Review Not Production (Ntarlagiannis et al, , 2010a(Ntarlagiannis et al, , 2010b, magnetite and Fe(0) particles . Microbes and biofilms produce relatively small phase responses of typically <2 mrad (Ntarlagiannis and Ferguson, 2009).…”

“…Detection of such responses in field surveys is likely to be very difficult. Non conductive minerals also typically produce small SIP phase responses arising from ion migration within the electrical double layer (EDL) at the mineral water interface (typically <<10 mrad at frequencies <1000 Hz; Vaudelet et al, 2011;Zhang et al, 2012). In contrast, semiconductive minerals dispersed in a matrix of non conducting minerals, including natural authigenic minerals such as magnetite, secondary precipitates and metallic particles may give larger phase responses, typically of the order of several tens to hundreds of mrad Personna et al, 2008;Ntarlagiannis et al, 2010a).…”

Investigations of a Cretaceous limestone with spectral induced polarization and scanning electron microscopy

“…The surface charge on calcium carbonate minerals is weaker compared to the surface charge of, for example silica minerals (Zhang et al 2012) which can explain weak polarization effects caused by the electrochemical mechanism (e.g. Schwarz 1962;Revil & Florsch 2010).…”

Modeling the evolution of complex conductivity during calcite precipitation on glass beads

“…Geochemical borehole data give accurate measurements of the water chemical composition associated with calcite precipitation but they are time consuming, not continuous in time, invasive and spatially limited to the location of the boreholes. The complex conductivity method can be used to non-intrusively monitor calcite precipitation in porous media because of its sensitivity to the evolution of the mineralogy, pore structure and connectivity (Wu et al 2010(Wu et al , 2011Zhang et al 2012). This geoelectrical method investigates both conduction (i.e.…”