Study doesn’t sugarcoat the effects of road salt
After the snow from last week’s “bomb cyclone” melts, cities and towns across the northeast will find their roads and sidewalks still a ghostly white.
That fine white powder is salt, America’s favorite de-icing chemical. More than 15 million tons of the stuff is applied annually, only to wash away with snowmelt or spring rains. But just because it’s gone from your block doesn’t mean it’s gone for good. It may end up in your faucet.
Road salt is an influential part of a decades-long chemistry experiment local governments have unwittingly conducted on soil, waterways and infrastructure. Studying river data nationwide, a study published Monday explains that 37 percent of all U.S. river systems have greater salinity, and 90 percent have seen a decrease in acidity, compared with a century ago. The two trends are related, scientists conclude, as urbanization and widespread use of chemicals such as road salt damage America’s water and soil quality while corroding infrastructure.
Why is less acid bad? Here’s how nature usually works. Raindrops absorb atmospheric carbon dioxide, turning them slightly acidic. It’s the same reaction that makes drinking a lot of seltzer potentially bad for your teeth. When that rain hits the ground, specifically rock and soil, the acid frees up ions from mineral salts and washes things like magnesium and calcium into rivers and out to sea, a process that scientists call “weathering.”
Put simply, a lot more salt is being pushed into our water, and that’s bad. Easier weathering and the resulting increase in the alkalinity of waters across the North American continent is a process that now has a name: “freshwater salinization syndrome,” according to a paper in Proceedings of the National Academy of Sciences.