The Impact of Urbanization on River Salinity in North-Central Massachusetts

Robert Carpenter

Abstract:
Salinization of freshwater is one of many adverse impacts that urbanization has on local bodies of freshwater and can harm aquatic biota, impair drinking water quality, and have detrimental effects on local ecosystems. Treated wastewater, runoff of road de-icers, weathered building materials (such as concrete), construction and land clearing all create anthropogenic inputs of salts into freshwater bodies. The purpose of this study is to evaluate the effects of urbanization on local river salinity (i) seasonally and (ii) longitudinally (upstream-to-downstream). Eight HOBO conductivity loggers were placed along the North Nashua River in North Central Massachusetts to monitor specific conductance (SC), which is an indicator of salinity. Data collection began on October 1, 2020 with data points collected continuously every 30 minutes. Cross-sectional soil samples were collected every season from six of the sites and analyzed for SC and chloride to identify trends in soil salinity adjacent to the river. Annual soil salinity was higher at downstream urban sites than at upstream rural sites. Both mean and median soil salinity were highest in the winter and lowest in the summer. In-stream data was analyzed using ArcGIS Pro to map the spatial distribution of high salinity water in the Nashua River basin on an annual and seasonal basis.