Conductivity of Compacted Clay Soils To Water and Organic Liquids

Abstract

Four clay soils, selected to represent a range of mineralogies, were permeated with water and seven selected organic liquids in fixed wall permeameters. The conductivity of each soil/water followed by the chosen organic liquid was measured. The tested organic liquids included an acid and a base, and both polar and non-polar solvents. All four compacted soils had conductivities to water of less than 1 x 10-7 cm s-1. Acetic acid initially decreased the conductivity; however, after sufficient acid had permeated the soils, the conductivity generally increased to approximately the values measured with water. Soils treated with aniline exhibited conductivities of one to two orders of magnitude greater than values measured with water. Organic solvents, i.e. methanol, acetone, ethylene glycol, heptane and xylene, had conductivities of two to three orders of magnitude greater than their respective conductivities to water. While the miscible organics may undergo dilution by water in a field situation, the water immiscible solvents heptane and xylene would not be diluted by leachate and may reach a clay liner at or very near full strength. Conductivities of the soils to the organic solvents were much greater than could be explained by the densities and viscosities of the liquids. Visual observation of the soils permeated with organic solvents indicated the presence of cracks and voids in the centre of the soil mass which were not observed after the soils were permeated with water.