Electrical conductivity in soils: Underlying phenomena

Electrical conductivity can be accurately and readily measured in the laboratory and in the field, with minimal electrode effects even in high specific surface soils and/or high ionic concentration pore fluids. Electrical conductivity combines the contributions of particle conduction, surface conduction and pore fluid conduction, and the effects of particle shape and fabric. The interplay between participating soil parameters is often obscured in typical empirical equations, such as Archie's law. New experimental results show that surface conduction is an important contributor to global soil conduction in high specific surface soils that are saturated with low-ionic concentration pore fluids; the relevance of surface conduction increases with decreasing porosity. On the other hand, pore fluid conduction prevails as the conductivity of the electrolyte and the porosity of the soil increase. Furthermore, low frequency conductivity anisotropy increases with increasing ionic concentration. Simple yet robust microscale analytical models properly capture the observed interplay between the most relevant soil parameters.