ROAD SALT CONTAMINATION OF THE SAUGUS WATERSHED, COASTAL MASSACHUSETTS AND THE INFLUENCE OF LAND USE PRACTICE WITHIN A SINGLE WATERSHED

To ensure safe driving conditions throughout the winter, an average of 20 tons of road salt is applied to each highway mile in Massachusetts per year. Road salt, sodium chloride (NaCl), readily dissolves and enters surface water, groundwater, and soils. The majority remains a dissolved solid in surface water and groundwater, but some precipitates on the surface and in soils, only to be redissolved during later storm events. Road salt is removed from the watershed as a dissolved solid in groundwater baseflow and storm event flow at or near the surface. In New England watersheds, approximately half of the road salt applied each year is accounted for in stream discharge. Road salt contamination has been correlated with loss of plant and macroinvertebrate life, loss of biodiversity, nutrient depletion of soils, release of toxins, infrastructure damage, aquifer stratification and stagnation, and a decrease in water quality. This study focuses on the Saugus Watershed, a coastal Massachusetts watershed with especially diverse land use practices, and attempts to determine what, if any, influence land use practice has on road salt contamination within a single watershed. This is being done by calculating the concentration and dissolved load of major ions in groundwater baseflow and storm event flow, including sodium and chloride, at 28 sample sites throughout the watershed over a year-long period and comparing the results at each sample site. Preliminary results show that during the summer, sodium and chloride stream discharge concentrations range from 3 - 150 mg/L and 4 - 350 mg/L respectively throughout the watershed. The lowest concentrations correspond to undeveloped upstream locations and the highest concentrations correspond to areas of near major highways.