Solute partitioning in freezing soils

Abstract

One-dimensional constant end plate temperature (step freezing) tests were conducted on a saturated clayey silt at various pore-water salinities to establish the relationship between solute rejection and freezing conditions. The rate of cooling, a parameter that is a function of both frost penetration rate and temperature gradient in the frozen soil near the frost front, is the main factor controlling solute partitioning between the solid (ice) and liquid phases. It was also established that there is a threshold rate of cooling of 3 °C/day above which no solutes are rejected from the ice matrix. For rates of cooling smaller than 0.1 °C/day, which incidentally corresponds to most of the field freezing conditions, more than 90% of the solutes are rejected from the pore ice. Key words: freezing, clayey silt, saline, solute, exclusion, rate of cooling.