Speaker
Description
Freeze-thaw cycles are ubiquitous in cold climates and can affect groundwater recharge and solute transport through the porous subsurface. These cycles create freezing and melting fronts that propagate centimeters to meters into the vadose zone. Within the vadose zone, these fronts cause spatial and temporal variations in pressure and temperature that impact flow and transport. These coupled hydrologic, mechanical, and thermodynamic changes drive a range of complex processes including cryosuction, solute quenching, and pore space expansion. In partially saturated porous soils experiencing freezing temperatures, ice content increases, which in turn causes the capillary pressure in the partially frozen media to increase. This dynamic capillary pressure change causes fluid to migrate upwards, a phenomenon known as cryosuction. While freeze-thaw cycles and their associated processes are frequent in high latitude regions, a key knowledge gap exists in how cryosuction processes affect groundwater recharge and the mobility and distribution of contaminants within the vadose zone.
To quantify the influence of freeze-thaw cycles, we created a quasi-3-dimensional tank (Hele-Shaw cell) filled with glass beads to act as the porous media. The tank was first partially saturated with unfrozen water and subsequently frozen using a circulating system to generate a top-down freezing front. To track the movement of fluid flow, we added a dye tracer to the unfrozen bottom layer of the tank. Time lapse photography recorded the movement of the dye tracer throughout experimental trials and was used to to optically visualize the cryosuction-driven transport within the bead pack during freezing front progression. Image processing was used to quantify liquid water content and tracer movement to interpret the role of cryosuction-driven transport. The results of this study provide valuable insights into cryosuction processes in unsaturated porous media, as well as water quality and recharge of near-surface aquifers in areas that experience seasonal freezing.
| Country | United States |
|---|---|
| Water & Porous Media Focused Abstracts | This abstract is related to Water |
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