EAST LANSING, Mich. — The Michigan Department of Transportation is participating in a pilot program testing out a liquid de-iceras a way to reduce salt on the roadways. It's no secret, road salt isn't good for the environment. A study published in Dec. 2021 took a look at a salt that's pouring into Lake Michigan.
"The primary purpose of this study was to look at not chloride, but rather to look at how much nitrogen and phosphorus was in those stream samples," said Research Assistant Professor at Michigan State University, Anthony Kendall.
Kendall was able to collaborate on the study with scientists Robert Mooney and Hilary Dugan at the University of Wisconsin-Madison.
"We are very concerned right now about the amounts of nitrogen and phosphorus that make it into the Great Lakes," said Kendall. "Because those two, what we call nutrients, which are critical for life, are leading to things like harmful algae blooms, and changes in ecosystems that are disrupting fisheries and resulting in foul algae biomass that wash up on the shore."
He says these are concerns all across the Great Lakes. But after collecting water samples from streams around the shore of Lake Michigan, they found an additional concern: chloride, a byproduct of dissolving salt.
Using the data collected in 2018 from over 200 locations, they discovered that road salt and other salt sources created by humans are increasing the lake's saltiness.
"The darkest color blue is between zero and 10. And then as the blues get lighter, that means higher and higher values. Here in yellow, we get values of chloride between 10 and 1000 milligrams per liter," said Kendall. "Anything above 1000 milligrams per liter is a very high chloride value and one where we would expect that is causing immediate consequences for those ecosystems."
In fact, they found that chloride concentrations have multiplied over the last two centuries. In the 1800s, levels sat at 1 to 2 milligrams per liter of water. And in 2020, it was 15.
"If we're talking about Lake Michigan, and whether chloride is a threat, the answer is not right now. And that's because even though chloride has been steadily rising for the last century, it's still not at all what you'd consider salty. The chloride concentrations in Lake Michigan qualified as very low chloride waters," he added. "Where you have a lot of road salt, and in septic tanks around smaller streams, smaller wetlands, and that's when we can start to see chloride levels get up to, up to values that start to threaten ecosystems that are adapted to freshwater."
Kendall says the interesting part of all of this is the water in the streams was all coming from the ground, or nearly all of it.
"So, this groundwater that supplies Michigan and Wisconsin's lakes and streams with water during the summertime is what contains the chloride. So groundwater has now carried the chloride contamination from our activities that happen at the surface."
He says groundwater has very long travel times and can take 10 to 100 years for it to move from the point where it starts on the land surface, through the groundwater system, and end up in a stream lake or wetland somewhere in the basin.
"So we could have a very long legacy of our decisions today. And that's one of the reasons why it's important to pay attention now. Because the sooner we change it, the sooner differences can start to happen," said Kendall.
Kendall says you can help by not salting your driveway if you can and using water softeners selectively.
"But the big use is the chloride and the salt that we use on our roads and there MDOT and is actually working pretty hard to encourage county level departments of transportation to use more salt friendly methods or salt reducing methods environmentally friendly methods," said Kendall. "Everything isn't an immediate threat. But it can often be something that we need to keep an eye out for, and that we need to be aware of, and we need to monitor and work like this helps both scientists as well as the general public."