Measurements of near-surface temperature fluctuations during a period of night frost were used in conjunction with a surrogate measure of soil water ion concentration to attempt to trace inflections in these time series to soil water advection effects. Major inflections in the ion concentration time series were traceable to water and water vapor processes as a freeze-thaw front propagated vertically through a soil profile at shallow depths. Relative ion concentration was related to the electrical potential measured between a probe at different depths of interest and a ground spike. The field probe electric circuit was modeled as an electrolytic cell without transference. Field time series data illustrated that effects of water migration toward near-surface evaporation/freezing fronts, solute expulsionfrom a freezing region, internal evaporation, and clean melt water release could be detected by variations in the electric potential orits surrogate, the relative ion concentration index. The spatial/temporal pattern of temperature and relative ion concentration helps to explain interactions or coupling between induced hydraulic, osmotic, and electrical gradients during the propagation of a thermal disturbance through a soil. This paper appears in transportation research record no. 1288, Geotechnical engineering 1990.
Samenvatting