DescriptionSpectral induced polarization (SIP) is an electrical geophysical technique that non-invasively characterizes subsurface environmental processes by measuring the complex electrical conductivity. Complex conductivity, which includes a real component representing the ability of electrical conduction and an imaginary component representing the ability of electrical charge storage (i.e., polarization), provides distinct insights into the interfacial properties in porous materials. This dissertation focuses on the improvement of data acquisition, data interpretation, and hydrological applications of the SIP technique.
First, a novel correction method was developed to remove the laboratory SIP measurement errors at kHz frequencies. These errors were accurately predicted by an electrical circuit model considering the parasitic capacitive coupling effects of the measurement system. The corrected SIP spectra of various earth material samples show excellent agreement with the theory. This study sheds light on the research on kHz range electrical properties which are important for understanding the physicochemical properties of small particles yet overlooked due to unrecognized errors in previous studies.
Secondly, negative induced polarization (IP) effects were investigated to improve the data interpretation of SIP. Fundamental theory was developed to quantitatively explain the negative IP effects, which are associated with sensitivity of resistivity measurements and subsurface heterogeneity. Comprehensive studies including numerical modeling, electrical circuit modeling, and sandbox experiments were performed to demonstrate the occurrence and control factors of negative IP effects. This work highlights the importance of including negative IP data, that were normally discarded as measurement errors, in the inversion or interpretation.
Finally, a novel field SIP methodology was developed to characterize the physical properties of streambed sediments in river corridors. Synthetic modeling using a 1D analytical model illustrates the influence of water layer depth and conductivity on the field SIP measurements made at the streambed-stream water interface. Field SIP measurements along a landfill-impacted river reveal discrete streambed zones with enhanced bulk surface area generally corresponding to anoxic groundwater discharge zones with high concentrations of fine-grained iron oxide precipitates. This work highlights the advantage of the SIP method and its potential for studying the river dynamics and conditions.