As D.C.’s snow and ice finally melt, rising sodium levels from road salt are fueling a growing water‑quality threat.
The ice and snow that fell on the D.C. area during last month’s storm is finally starting to melt. The ice dunes that have been on the sides of streets for weeks are slowly shrinking. But as the melting continues, there’s a danger that’s seeping into our waterways.
“Salt is the biggest enemy of fresh water that there ever was,” said Sujay Kaushal, a professor of geology at the University of Maryland. “It’s a very pressing issue. I’d say salinization issues are the oldest, most boring but yet most important problem there is for water quality.”
Kaushal has been sampling water from the Potomac and Anacostia Rivers for years, as well as water from Piney Branch, Rock Creek and a host of other tributaries. What he’s found is that sodium levels in the water have been rising.
This issue is the presence of sodium chloride, the main ingredient in most traditional road salt treatments.
“Over that last 50 years, for example, in the Potomac River, we’ve seen that some of the salt concentrations basically have increased about five-fold,” Kaushal said.
He said the rise is due largely to the increased amount of road salt used after large snow events.
Kaushal said while we’ve been seeing less snow in the winter overall, when it does snow, we tend to have extreme snow events, which leads to heavy road treatments. He said the salinization trend is extremely harmful to animals that live in the rivers and streams as well as the vegetation that grows around them.
“Over the last decade, there’s been a lot of urbanization in the Potomac Watershed and so there’s more impervious surfaces, roadways and parking lots that you have treat with salt, leading to the big (salt) pulses that we see in winter,” Kaushal said.
So, more roads means more surface area that has to be treated with road salt. All that ends up in the river — or in the soil, where it can stay for a long period of time and be washed out by heavy rain.
Local governments are trying out alternative de-icers and more precise salting methods to reduce runoff. Still, Kaushal said we won’t see the results of those efforts for some time.
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