Time domain induced polarization inversion of multi time-channel data for contaminated area

Abstract:

Induced polarization (IP) method, which is one of the geophysics methods based on electrical phenomena, has been used increasingly in environmental investigations. This is attributed to the fact that IP measurements are very sensitive to contaminants and biochemical reaction. Time domain IP (TDIP) method measures apparent chargeability explaining overvoltage caused by chargeability anomalies and normalized by measured apparent electrical resistivity. Theoretically the overvoltage should be measured at the moment when the survey current is turned off, which is impossible due to the equipment limitations. Instead, an IP equipment measures decaying voltages over time which can be called as ‘multi time-channel data’ and integrates every measured voltage to obtain the apparent chargeability. Conventional IP inversion strategies deal with the apparent chargeability data, which do not fit to the real process of how chargeability data are achieved.

In this study, we developed a new strategy to invert TDIP multi time-channel data to recover chargeability anomalies, with consideration on the real measurement mechanism of TDIP data. To simulate decaying IP curve as well as to perform forward modeling for multi time-channel data, TD Cole-Cole model is adopted. Firstly, we applied the developed inversion algorithm to a simple synthetic chargeability model to prove its applicability. In order to make a realistic synthetic model of environmental sites, we make a hydrogeological model which includes fluid contaminants and set Cole-Cole model parameters. This subject is supported by Korea Ministry of Environment as the SEM projects (No. 2018002440005) and KETEP granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20194010201920).