THE OBSERVED IMPACT OF ROAD DE-ICERS ON WATER QUALITY IN NORTH-CENTRAL MASSACHUSETTS

Freshwater salinization in the northeastern United States has increased in the last several decades due to multiple factors such as agricultural and urban runoff, and increased frequency of road deicer applications. Road salts tend to runoff into rivers, ponds and lakes; high concentrations of salt in freshwater systems may negatively impact the ecology of the affected area. The purpose of this study is to assess seasonal trends in river water salinity from an upstream to downstream gradient. Six HOBO conductivity loggers were placed along the North Nashua River in Massachusetts to continuously monitor river salinity. Seasonal roadside and stream bank soil samples were collected at each site in addition to roadside snow samples. Specific conductance (SC) and chloride concentrations (mg/L) were measured for all water, soil, and snow samples. A maximum SC of 2,390 µS/cm was recorded in the winter at an urban downstream site. Median river SCs were highest in the fall (224 µS/cm to 526 µS/cm for all sites) and lowest in the spring (129 µS/cm to 427 µS/cm at all sites). Soil salinity was higher at downstream urban sites with a mean SC of 1,009 µS/cm across all seasons, while rural upstream sites had an average SC of 311 µS/cm across all seasons. Winter soil samples had higher SCs than spring samples. Several roadside snow samples had SCs >10,000 µS/cm with chloride concentrations between 1,500 mg/L and 4,500 mg/L. Sharp increases in river salinity during the winter may be attributed to runoff containing high salt concentrations from road salt applications, and these salt flux events correspond with high river discharge during precipitation events and/or snowmelt. Additional water and soil samples are continually being collected and analyzed in order to identify road salt impacts on freshwater systems on a seasonal and annual basis. Though river salinity appears to be highest in the fall and winter with additional snow samples showing high amounts of salt alongside roads, it is still unclear how much of the data collected is influenced by road salt applications because of the short temporal span. A more complete picture of seasonal and/or annual trends in river salinity will be important to help understand the impacts on local freshwater systems for ecological and public health.