ASSESSING THE UPSTREAM TO DOWNSTREAM TRENDS IN FRESHWATER SALINIZATION OF AN URBANIZED CENTRAL MASSACHUSETTS WATERSHED

Freshwater salinization due to anthropogenic activities including urbanization, runoff, and road de-icer applications has received global attention in recent times due to the associated degradation of water quality and stressed aquatic ecosystems resulting from excess fluxes of salt into the freshwater environment. This study seeks to evaluate the impacts of urbanization and road de-icer applications on the North Nashua River watershed in north-central Massachusetts. Eight sites in the watershed have been monitored for specific conductance (SC) continuously since October 2020. The eight sites are located along the main stem of the river from upstream (82% forested) to downstream (35% urban + agricultural). Seasonal soil samples, monthly water samples, and winter roadside snowbank samples were collected and analyzed for SC and chloride. Results indicate that stream bank soil samples do not have significantly different salinity values by season. River salinity increases significantly from upstream (~200 µS cm^-1 on average) to downstream (~500 µS cm^-1 on average) as the watershed becomes more urbanized. River SCs are highest, but most stable in summer, whereas winter SCs tend to be lower on average but experience more spikes in SC due to road de-icer events. Year-to-year trends in SC in relation to river discharge as well as chloride results will also be presented.