WASHINGTON — As the weeks of snow and ice melt away into frigid memories, the salt and chemicals used to clear area roadways and sidewalks aren’t going anywhere.
And that’s the problem.
“Even though it’s melting, the road salt stays in the environment for a very long time,” says Dr. Sujay Kaushal, assistant professor in the department of geology, at University of Maryland, College Park.
When the snow melts, a considerable amount gets built up in the groundwater, says Kaushal.
“So even when there’s no salt applied, it’s still going to be saltier during the summer months,” says Kaushal. “Maybe not as high as we see in the winter, but that residual salinity still remains and lingers on for seasons, even years, and decades after we apply salt.”
As it melts, some of the water goes directly into streams, and some seeps into the ground.
Eventually, a portion of that water migrates into the sediment or the dirt, and reaches the water table, where the salt is stored.
“We’ve seen salinization of major drinking water supplies in Baltimore and Washington, D.C., where the salinity has been increasing over time, over decades,” says Kaushal.
In addition, other chemicals used to clear sidewalks and driveways also build up in the groundwater.
“We need to make the connection that what we apply to the roadways doesn’t just go away, doesn’t just wash off,” says Kaushal. “It actually persists and stays in the environment, and is having effects on the environment.”
Increased salt can also affect the biodiversity in streams, Kaushal says.
Some organisms are more acclimated to fresh water environments, says Kaushal. “So when you have fresh water converted into salt water, that can affect the types of species and organisms that are present.”
Another problem — salt can trigger the mobilization of certain contaminants from the sediment.
“The salt actually replaces some of these toxic metals and contaminants that are stuck onto soils at the bottom of streams and causes them to release into the water,” he says.
With over a decade of rising salt concentrations, Kaushal says planners can control the problem by careful consideration of where roadways are built, and being prudent in the amount of road salt that is actually needed to keep roads clear.
