SIMULATION OF DYNAMICS AND MECHANISM OF ROAD SALT BRINES MIGRATION IN THE SUBSURFACE

Deicer brines (sodium chloride) running off the road surfaces during/after the winter snowstorms are significantly denser than the surrounding snow or ice. For temperatures ranging downward from 30 ^oF to 25 ^oF and 20 ^oF these solutions have densities increasing from 1.015 g/cm³ to 1.047 g/cm³ and 1.075 g/cm³ respectively. The brines will therefore accumulate at the bottom of the snow pile and even melt through the frozen ground to reach the subsurface and the underlying aquifer. Our interest is to investigate how these concentrated solutions interact with groundwater and the mechanism of modifying their initial high concentrations to the levels observed in natural waters in the northeastern US. In the same temperature range as above (30 ^oF to 20 ^oF) the brine concentrations increase from 2.1 wt% to near 10 wt% of NaCl whereas by contrast the NaCl concentration in natural waters is typically less than 0.2 wt%, more commonly 0.02 wt% to 0.08 wt%.

We designed a series of benchtop experiments using plastic transparent boxes (12x12x21 cm) filed with a saturated single fraction fine sand and introduced blue dyed brine solutions (0.5 wt%, 1 wt%, and 5 wt%) alongside the transparent wall. Experimental progress was recorded by time lapse photography.