On the relation between viscosity and hydraulic conductivity for volatile organic liquid mixtures in soils

Changes in the volatile organic liquid mixture (VOLM) hydraulic conductivity in different soils are compared with corresponding changes in VOLM viscosity through an extended analysis of results from three previous experimental studies. The conductivity with regard to four different kerosene mixtures, corresponding to different degrees of volatilisation of the original kerosene, was determined in one set of soils; an increasing degree of volatilisation implies less lighter kerosene compounds, changing both kerosene viscosity and its chemical composition. In another set of soils, kerosene conductivity measurements were conducted at two temperatures, which provided two different viscosities but did not affect the kerosene chemical composition. Both volatilisation- and temperature-induced changes in kerosene viscosity and conductivity were studied in two of the soils. In all the soils that were used in the temperature experiments, the changes in kerosene conductivity could be successfully predicted by scaling the original kerosene conductivity value based on the observed viscosity ratio. For the chemically different kerosene mixtures, the changes in conductivity agreed with the corresponding viscosity changes only in inert sands. For a montmorillonitic loam, a montmorillonitic clay and a peat soil, considerable deviations were found between the conductivity ratio and the viscosity ratio; for the peat, which was also used in temperature experiments, no such deviations were observed at different temperatures. The deviations between the conductivity ratio and the viscosity ratio were also found to increase with increasing differences in kerosene chemical composition. These results indicate that chemical composition may be of major importance for VOLM hydraulic conductivity in interacting soils, apart from the effect that the composition has on viscosity. The viscosity ratios were shown to deviate more than 300% from observed conductivity ratios for the chemically most different kerosene mixtures.