Spectral induced polarization monitoring of induced calcite precipitation in subsurface sediments

Abstract

Summary Co-precipitation of contaminants within the crystalline structure of calcite is a promising natural attenuation or remedial technology being considered at contaminated sites. We explore the sensitivity of the spectral induced polarization (SIP) method to induced calcite precipitation in natural sediments as a path forward to non-invasively monitor these sites. We performed time-lapse column experiments using phased (I-IV) injections over 40 days on natural sediments from the Hanford Site (Washington State, USA). In the phased injections, abiotic calcite precipitation was induced and confirmed to have occurred. Previous work on glass beads and homogeneous sand was limited to high frequency detection of calcite, however in this work we observed the development of two polarization mechanisms, one at high frequency (>100 Hz) and one at low frequency (< 100 Hz). Based on the characteristic frequencies from the SIP high and low frequency regimes, characteristic length scales (L) were computed where the adsorption mode of Na+ versus Ca2+ was compared by using diffusion coefficients corresponding to Na+ versus an arithmetically averaged value for Na+ and Ca2+. Using the diffusion coefficient of Na+, the high frequency L was found to correlate well with the size of the calcite crystals. The low frequency L correlated well with the individual natural sediment grain sizes within the columns. During late experimental times (day 36 and 40), the characteristic low frequency in two of the experimental columns shifted to lower frequencies (<0.001 Hz) which may signify SIP sensitivity of the formed calcite with the sediment grains. In field applications, the development of a low frequency polarization length scale to monitor calcite precipitation is promising for field monitoring applications, however further laboratory work needs to be performed to examine the SIP sensitivity of calcite formation in the presence of natural sediments.

Electrical Responses of Modified Mineral Surfaces as Observed With Spectral Induced Polarization and Atomic Force Microscopy

“…While these and other studies typically presume that calcite precipitation is distributed throughout a porous medium, other behaviors may also occur. For example, Izumoto et al (2022) recently showed that high frequency (100-10,000 Hz) SIP responses similar in magnitude to those observed by Placencia-Gomez et al (2023) could be generated by the formation of a solid wall of calcite precipitated along a reaction front between solutions of CaCl 2 and Na 2 CO 3 in microfluidics experiments. Despite these and many other studies, there remains a lack of experimental evidence providing direct links between the electrical properties of mineralfluid interfaces, such as the surface of calcite precipitates, and the overall electrical response of a composite porous medium captured by SIP measurements.…”

“…Leroy et al (2017) were later able to fit these responses using a grain polarization model. Recent experiments by Placencia-Gomez et al (2023) observed SIP responses occurring at both low frequencies (0.001-0.1 Hz) and high frequencies (100-10,000 Hz) during calcite precipitation experiments using columns of soil from the Hanford site (WA, USA). These authors observed the high frequency response to be almost three times larger than the low frequency response.…”

Dynamics of Electric Polarization and Relaxation of Ions at Humid Calcite Surfaces

“…Calcite is a common mineral that has important roles in subsurface geochemistry, hydrology, and carbon sequestration as well as in atmospheric chemistry. Past studies − have shown that calcite precipitation is linked to the appearance of a capacitive SIP signal that is strongly dependent on precipitate grain size. Accurate interpretation of such results will require a better understanding of the ion mobility on the calcite surface.…”