IMPACTS OF ROAD SALT APPLICATIONS AND URBANIZATION ON WATER QUALITY AND AQUATIC MACROINVERTEBRATES OF THE NORTH NASHUA RIVER, MASSACHUSETTS

Freshwater salinization is a global issue receiving attention in recent times due to the potential impacts of increased salt concentrations on water quality and freshwater aquatic ecosystems. The North Nashua River in Central Massachusetts is impacted by salinization due to urbanization and applications of road de-icing agents containing NaCl or CaCl₂, which alters chemical and biological composition of the river. As an example, a city in the North Nashua River watershed, Fitchburg Massachusetts, stores approximately 5,352 m³/y of NaCl, 229,000 m³/y of sand, and 11,000 L/y of CaCl₂. These products are applied to roads during winter storms and subsequently runoff into streams during melting. This study analyzes a continuous freshwater salinity network of eight sites within the North Nashua River, ranging from forested headwaters upstream to highly urbanized areas with major highway bridge crossings of the river downstream. Freshwater salinity data to date shows a general increase in mean specific conductance (SC; μS/cm) from upstream to downstream as urban density and road density increase. Downstream SC means were 480 μS/cm and the lowest SC mean was 183 μS/cm at the forested headwater site. Downstream sites also show “spikes” in SC, with levels approaching 4,000 μS/cm occasionally in some sites; these spikes occur during all seasons and not just in winter. Two years of continuous SC data will be presented, however, collection and analysis of data is ongoing. Benthic macroinvertebrates were also sampled at each study site and will be used to evaluate if the trends in SC affect species richness and abundance in the freshwater ecosystem as well as the pollution tolerance or sensitivity of the aquatic communities.