Influence of physical and chemical properties on the low-frequency complex conductivity of peat
M. Ponziani, E.C. Slob, H. Vanhala and D.J.M. Ngan-Tillard
Issue: Vol 10, No 6, December 2012 pp. 491 - 501
Special Topic: Induced Polarization for Near-surface Investigations
Info: Article, PDF ( 6.99Mb )
Organic layers are heterogeneous in space and their composition changes over time. This poses challenges to ecohydrologists, subsurface hydrologists and ground engineers in characterizing subsurface peat structures and predicting their behaviour over time. Peat deposits can be characterized by performing electrical surveys, provided that the complex conductivity of peat is understood and connected to its physical and chemical properties. Low-frequency (0.1–1000 Hz) induced polarization measurements were carried out to investigate the correlation between the chemical and physical properties of several peat samples and their electrical properties. A Cole-Cole model was fit to the peat spectra to obtain the model parameters and study their relationship with the sample properties. All the samples were characterized by analysing their degree of humification, water content, organic content, cation exchange capacity, pH and conductivity of the pore-fluid. Two significant correlations between physical, chemical and electrical properties are found. The peat bulk conductivity is directly correlated with the pore fluid conductivity, whereas the degree of humification of peat shows an inverse correlation with the phase angle. This study presents results that have implications for peatland characterization with frequency dependent or single frequency analysis of induced polarization measurements.