With winter seemingly here to stay, one of the most common sounds we hear is the familiar “beep beep beep” of salt trucks on our streets and highways.
But what is all that salt doing to our environment?
Scientists have long recognized that road salts can contribute to chemical changes in rivers and streams. But research by Chatham University assistant professor of water resources Ryan Utz, Ph.D. and his colleagues has determined that long-term salinization is occurring throughout most of North America and may be linked to chemical changes beyond salts, including chemicals that lead water to become more alkaline.
The conceptual framework that attempts to explain the trends is the Freshwater Salinization Syndrome, and it postulates that many variables are leading to chemical changes in our nation’s rivers. A combination of road salt pollution, acid precipitation, expanding urban and agricultural land cover, and potentially climate change appear to be causing surface waters (lakes and rivers) to become saltier and more alkaline. Such changes may cause problems for facilities that deliver municipal water for us to drink.
His research found that although individual trends can vary in strength, changes in salinization and alkalinization have affected 37% and 90%, respectively, of the drainage area of the contiguous U.S. over the past century. Across 232 USGS monitoring sites, 66% of stream and river sites showed a statistical increase in pH, which often began decades prior to acid rain regulations.
The Freshwater Salinization Syndrome is most prominent in the densely populated Eastern U.S. and Midwestern U.S., where salinity and alkalinity have increased most rapidly. The syndrome is caused by salt pollution (e.g., road deicers, irrigation runoff, sewage, potash), accelerated weathering and soil cation exchange, mining and resource extraction, and the presence of easily weathered minerals used in agriculture (lime) and urbanization (concrete).
Freshwater Salinization Syndrome can lead to a broad range of harmful impacts, including infrastructure corrosion, contaminant mobilization and even variations in coastal ocean acidification caused by increasingly alkaline river inputs. Unless regulated and managed, the Freshwater Salinization Syndrome can have significant impacts on ecosystem services such as safe drinking water, contaminant retention, and biodiversity.
What is the solution?
Dr. Utz hopes this effort will cause researchers to dive in deeper and determine the biggest contributors to the problem. Part of the challenge is that rivers can be thought of as ‘watershed tea’- what happens on land always has a signature in the waters that surface nearby.
“At the very least, the average person could forego or limit road/sidewalk salt use, fertilizer on their lawns, washing cars, and any other activities that result in chemicals ending up in the ground,” he says.