Can Winter De-Icers Go Completely Green?
Additives to road salt designed to make it more environmentally friendly might still have tradeoffs
Every year, as winter closes in, transportation authorities prepare to deploy their vast stockpiles of salt and sand to keep the roads and highways safe and ice-free for drivers.
In the United States, roughly 18 million metric tons of road salt are spread on the roads each year, with another 5 million used in Canada. In Minnesota, nine tons of salt are applied per lane mile each winter—meaning a single mile of a four-lane highway gets 36 tons of salt dumped on it each year.
But all that salt does not just disappear along with the ice in the spring; it sticks around, and can have major effects on the surrounding ecosystems and even drinking water.
As the salt dissolves and runs into local streams it makes them saltier and disrupts the creatures that live there.
“Any increase in saltiness in a freshwater ecosystem will change the types of microorganisms and plants that can live there,” said Fraser Shilling, co-director of the Road Ecology Center at the University of California, Davis. “They either die or migrate away from the area.”
One 2010 study in the Canadian city of Pickering, on the north shore of Lake Ontario, found that around half of the 7,600 tons of salt spread on the roads there each year seeps into the groundwater and local streams, or washes into nearby Frenchman’s Bay. The bay becomes more than twice as salty as the rest of the lake, nearly wiping out its fish populations. The effect is permanent and non-reversible.
“These salts are persistent, they get diluted but they will sit there for geological time,” said Shilling.