T254 The Hydrogeological Effects of Urbanization (Posters)

Wednesday, 3 November 2010
8:00 AM - 6:00 PM
Hall D

ROAD SALTING AFFECTS on LOCAL WATER BODIES IN THE SOUTHERN NASHUA RIVER WATERSHED, MA

Paper number: T254-5
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

In the winter months, road salt (NaCl) application is the main method for keeping roads free of ice. Studies have shown correlations between the use of road salt and water contamination, density stratification within water bodies, nutrient depletion in soils through ion exchange, as well as damage to road infrastructure. Historical data taken at USGS gauging stations for several watersheds within Massachusetts indicate a strong positive correlation between specific conductance and dissolved chloride concentration, with an R² value of 0.9666. Gauging station sites show an increase in specific conductance and dissolved chloride concentrations since the late 1960s, which may indicate that portions of salt used annually, are remaining in the watershed. Increases may be attributed to factors such as, increased road density for new communities, as well as dissolved chloride remaining in groundwater, steadily building year after year.

In this study, several rivers and lakes in the southern portion of the Nashua River watershed, within Worcester County, MA, were sampled for specific conductance. Using a linear model, dissolved chloride concentrations for sampled rivers are calculated. Water sampling is carried out to determine if the winter use of NaCl is causing an increase in the year round chloride concentrations. Sample locations within forested areas, away from high road density, yield low specific conductance, and are used as indicators of background concentrations. Background specific conductance values for lakes are around 30 microsiemens, while background specific conductance values for streams are around 70 microsiemens. Deviations from these background concentrations are likely due to applications of road salt. Measurements, taken during the summer, show specific conductance values ranging from 39.2 – 683 microsiemens for streams, with approximated chloride concentrations of 4– 151 mg/L. Preliminary lake specific conductance values are measured at 29.2 – 2075 microsiemens. Sample sites that yield the highest concentrations are found to be located around major highways.