ION DYNAMICS OF A FREEZING SOIL MONITORED IN-SITU BY TIME-DOMAIN REFLECTOMETRY

In situ measurements of the electrical conductivity of the soil solution are cumbersome, especially under frozen conditions, and often involve destruction of the soil volume sampled. The objective of this work was to use time domain reflectometry (TDR) to study the dynamics of ions in the soil solution caused by freezing and thawing. The data set consisted of field,measured TDR and temperature records in four soil profiles in a loamy soil. Bulk electrical conductivity and electrical conductivity were evaluated from the TDR traces. Freezing caused a temporary twofold to fourfold increase in electrical conductivity. Strong evidence of a downward transport of ions during freezing was found; The transport was attributed to thermally induced regelation. Infiltration resulted in an increased electrical conductivity. TDR was shown to be a promising technique for monitoring the electrical conductivity of the soil solution, in both frozen and unfrozen soils.