Author: Carolyn Christmann

In cities like New Haven, winter brings more than just flurries and flakes. Salt laden sidewalks and streets are a sure sign that snow is on the forecast. Safety conscious New Englanders are quick to scatter this affordable and effective de-icer. Salt has become a (literal) widespread solution to preventing slips, falls and accidents, but what impact does its abundant use have on our waterways?

Aided by a Quinnipiac River Fund grant, Gaboury Benoit, professor of Environmental Chemistry at Yale School of the Environment, launched a research project — “Road Salt in Urban Runoff of the Quinnipiac River” — to measure the impact of winter salting on the environment, using the Quinnipiac River as a central testing site.

Using a sweep and weigh approach, Benoit measured the amount of salt on sidewalks and paved areas. The results revealed that most test sites contained more than 100 times the recommended levels. “People think, ‘if one pound is good, then ten pounds is better,’” Benoit explained. “Although science proves that a little salt can go a long way, people often pile it on thinking, “if I see it, then I know its working.”

Benoit’s study also measured the salt flux in catch basins, wells, tributaries and the Quinnipiac River itself. Salt flux is determined by an equation of a water’s saltiness and its flow.  The results showed extremely elevated levels across the board. The brine in catch basins measured a salt flux of 8000, which is 400 times the recommended levels and more than double the saltiness of the ocean itself. And the salt flux in deep wells averaged 100 — 1000 times the recommended level for groundwater.

“The whole system is contaminated.” Benoit described. “Even if we stopped salting immediately, it would be years for it to clear the system.”

With data covering the entire year, Benoit noticed a disturbing trend. In the summertime, after substantial rainfalls, salt levels measured nearly as high as the winter readings. This poses serious problems for aquatic organisms during their active and reproductive period, Benoit explained. He attributed these summer spikes to the stormwater surges that flush out the salt-saturated brine that settled in the bottom of catch basins in the winter season.

While the problem is pervasive, the solutions can be simple, Benoit described. By installing low-tech baffle panels in catch basins (a vertical panel that forces water out of the discharge rather than accumulating in the bottom), the majority of brine would be washed out of basins in wintertime when aquatic life is more dormant. 

Even more low-tech and effective is the solution Benoit widely recommends, “use less salt!”

This summer, several faculty members and students are engaged in important research projects supported by the Quinnipiac River Fund, examining how microplastics and metals are affecting wildlife in local aquatic habitats.