Experimental validation of a model relating water content to the electrical conductivity of peat

Abstract

The influence of water content on the electrical conductivity response of peat was investigated on peat samples extracted from different peatlands in the Netherlands and saturated at different pore fluid conductivities (0.001 to 1S/m). Tests were performed using a compression cell that allows for electrical measurements across the sample with a four-electrode configuration. Results at low-frequency showed a positive correlation between water content and peat conductivity when the pore fluid conductivity is higher than the peat conductivity, whereas at lower pore fluid conductivities (below about 10mS/m) the correlation was found to be negative. Peat conductivity was modeled as the sum of electrolytic and surface conductivity, and model parameters were studied as a function of water content, in order to implement water content in the model. The contribution of surface conductivity to the total peat conductivity response is particularly significant at low pore fluid conductivities, whereas at high pore fluid conductivities the contribution is negligible as the surface conductivity becomes independent of salinity. The derived model was used to predict water content from low-frequency electrical measurements of peat samples. Results suggest the possibility of determining water content of peatlands from electrical measurements; the accuracy of the prediction increases at higher pore fluid conductivities.