It’s estimated that more than 22 million tons of salt are scattered on the roads of the U.S. annually...about 137 pounds of salt for every American.
But all that salt has to go somewhere.
After it dissolves--and is split into sodium and chloride ions--it gets carried away via runoff and deposited into both surface water (streams, lakes and rivers) and the groundwater under our feet.
Because it’s transported more easily than sodium, chloride is the greater concern, and in total, an estimated 40 percent of the country’s urban streams have chloride levels that exceed safe guidelines for aquatic life, largely because of road salt.
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.
Recently, in some areas, transportation departments have begun pursuing strategies to reduce salt use.
Salting before a storm, instead of after, can prevent snow and ice from binding to the asphalt, making the post-storm cleanup a little bit easier and allowing road crews to use less salt overall. Mixing the salt with slight amounts of water allows it to spread more, and blending in sand or gravel lets it to stick more easily and improve traction for cars.
Elsewhere, municipalities are trying out alternate de-icing compounds.
Over the past few years, beet juice, sugarcane molasses, and cheese brine, among other substances, have been mixed in with salt to reduce the overall chloride load on the environment. These don’t eliminate the need for conventional salt, but they could play a role in cutting down just how much we dump on the roads.
Read the full article (by Joseph Stromberg for Smithsonian) here.
