A new approach to fitting induced-polarization spectra

Abstract

Best fitting of induced-polarization (IP) spectra by different models of Cole-Cole type evidences discrepancies in the resulting model parameters. The time constant determined from the same data could vary in magnitude over several decades. This effect, which makes an evaluation of the results of different models nearly impossible, is demonstrated by induced polarization measurements in the frequency range between [Formula: see text] and [Formula: see text] on thirteen mixtures of quartz sand and slag grains. The samples differ in size and the amount of the slag grains. Parameters describing the IP spectra are derived by fitting models of the Cole-Cole type to the measured data. The fitting quality of the generalized Cole-Cole model, the standard Cole-Cole model, and the Cole-Davidson model is investigated. The parameters derived from these models are compared and correlated with mass percentage and grain size of the slag particles. An alternative fittingapproach is introduced, using the decomposition of observed IP spectra into a variety of Debye spectra. Four integrating parameters are derived and correlated with parameters of the slag-sand mixtures and Cole-Cole parameters, respectively. The alternative approach generally enables a better fitting of measured spectra compared with Cole-Cole type models. It proves to be more flexible and stable, even for complicated phase spectra that cannot be fitted by single Cole-Cole type models. The integrating parameters are well correlated with characterizing parameters of the slag-sand mixtures. The total chargeability well indicates the mass percentage of slag grains, and the mean relaxation time is related to the grain size. The relaxation time distribution can be displayed by cumulative normalized chargeability versus relaxation time, similar to granulation curves. Anologous to the latter, a nonuniformity parameter characterizes the width of the relaxation time distribution.

Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

“…Florsch et al (2010) used for example IP to quantify the volume and mass of slag heaps at an archeological site (see also Weller et al 2000, andUllrich et al 2007). Nordsiek and Weller (2008) and Florsch et al (2010) found a linear relationship between the chargeability and the slag concentration that they used to quantify the amount of slag. In the monitoring of contaminant plumes, the precipitation of metallic particles associated with microbial-induced mineralization processes can have a substantial influence on the IP response.…”

On the pore water chemistry effect on spectral induced polarization measurements in the presence of pyrite

“…In the DD modelling, m t represents the summation of specific chargeabilities (m n = 1 ,N ) associated with incremental conductivity changes over narrow frequency intervals (f n =1,N ), where every specific value is related to a relaxation time (τ n=1,N ) within the measured frequency range. The mean relaxation time (τ m ) is defined as the average value of the specific relaxation times weighted by m t as follows (Nordsiek and Weller, 2008) …”

Influence of non-aqueous phase liquid configuration on induced polarization parameters: Conceptual models applied to a time-domain field case study

“…grain sizes, grain shape, grain surface chemistry and pore throat size distribution (e.g. Slater and Lesmes, 2002a;Scott and Barker, 2003;Binley et al, 2005;Nordsiek and Weller, 2008;Titov et al, 2010). Consequently, the IP method may have a greater potential of being able to detect NAPLs in the pore space compared to resistivity alone.…”