EXPERIMENTAL OBSERVATION OF DISSOLVED DEICER TRANSPORT IN THE SUBSURFACE

Winter deicing chemicals are transported from the sites of applications as dissolved solids either by direct overland flow or by percolation into the underlying aquifers. Previous studies show that percolation pathways can account for up to 70 to 90% of the total deicers applied on impervious surfaces subsequently discharged as baseflow throughout the entire year. Densities of percolating brines in equilibrium with snow/ice depend on environmental temperatures and can vary from 1.0053 to 1.0340 g/cm3 (temperature range from 26 to 31 deg.F). Denser than fresh water the brines will move downward toward the aquifer interior. Mechanism of brine percolation and the interaction with fresh groundwater is important to understanding how the brines are ultimately distributed within the aquifer: accumulation at the bottom or active mixing resulting in more dilute but more voluminous contamination. Our experiments suggest a style of rapid mixing due to Rayleigh-Taylor liquid instability suggesting more voluminous contamination of fresh water systems.