Deicing salt accumulation and loss in highway snowbanks

Environmental impacts of road deicing salt are well known, although salt pathways following application have rarely been quantified. Deicing salt (NaCl) fate was determined from retention and loss in snow cover adjacent to a 14-km section of highway in southern Ontario during the 1994-1995 winter, Total salt application was similar to 530 Mg (29-74 ks m(-1) length), Retention in snow cover in the highway right-of-way (ROW) decayed as a power function of distance from the highway, although melting of proximal snowbanks with high salt loads disrupted this pattern. Peak concentrations in snowbanks reached 6506 (Na+) and 9916 (Cl-) mg L-1. Wind transport of salt from the ROW was minor and restricted to relatively exposed sites, Almost all applied NaCl reached the soil surface via (i) direct runoff and infiltration of saline water from the road into the shoulder and ROW, and (ii) transfer of salt to snow cover adjacent to the highway and release during snowmelt. Total salt nux along the two pathways during a 49-d period was similar. Salt transfer via road runoff occurred during or shortly after application, unlike the intermittent fluxes from snow to soil surfaces in the ROW during this period. The latter were relatively uniform along the highway (3-5 kg m(-1) length of highway), accounting for 39 to 65% of applied NaCl. However, magnitude and timing of water and salt fluxes from snow to soil varied within the ROW and should be considered when modeling salt transport to groundwater.