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Road salt keeps America’s roads safe, but threatens the environment

A New York City Transit worker shovels snow and slush from the platforms of the public transit. Photo by MTA New York City Transit / Marc A. Hermann

More than 22 million tons of road salt — 139 pounds per person — is used nationwide each year to keep roads safe from snow and ice. But environmental concerns emerge after the snow melts and the salt compounds remain, Smithsonian magazine reports.

The cost-effective ice-buster threatens valuable environmental resources, including plants, aquatic life and groundwater. The magazine explains in its “Surprising Science” blog:

> Road salt pollution is generally a bigger issue for the surrounding environment and the organisms that live in it. It’s estimated that chloride concentrations above 800 ppm are harmful to most freshwater aquatic organisms–because these high levels interfere with how animals regulate the uptake of salt into their bodies — and for short periods after a snow melt, wetlands nearby highways can surpass these levels. A range of studies has found that chloride from road salt can negatively impact the survival rates of crustaceans, amphibians such as salamanders and frogs, fish, plants and other organisms. There’s even some evidence that it could hasten invasions of non-native plant species–in one marsh by the Massachusetts Turnpike, a study found that it aided the spread of salt-tolerant invasives.

On a broader scale, elevated salt concentrations can reduce water circulation in lakes and ponds — because salt affects water’s density — preventing oxygen from reaching bottom layers of water. It can also interfere with a body of water’s natural chemistry, reducing the overall nutrient load. On a smaller scale, highly concentrated road salt can dehydrate and kill trees and plants growing next to roadways, creating desert conditions because the plants have so much more difficulty absorbing water. In some cases, dried salt crystals can attract deer and moose to busy roads, increasing their chance of becoming roadkill.

Transportation officials in the U.S. have been experimenting with different, environmentally friendly alternatives to rock salt, the Associated Press reported Wednesday, covering the roads with cheese brine, sugar beet juice, molasses or potato juice.

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