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Road salt melts the ice – and then it pollutes the lakes, a new study says

Researchers say if current trends don't change, a lot of lakes could be too polluted for fish 50 years from now.

Salt is just fine for the ocean but it's not so good for Minnesota's lakes. And scientists say that's where most of the salt we put on our roads ends up.

Researchers with the Cary Institute of Ecosystem Studies said this week if the current trend toward saltier lakes in the northern U.S. continues, a lot of those waters will be too polluted to keep fish alive 50 years from now.

Their study looked at more than 370 lakes in the northern U.S. and Canada. The basic finding: if there's a road or a parking lot nearby, the lake is probably polluted with chloride, which comes from road salt.

Rivers get polluted, too, but lakes suffer the most. As one of the study's co-authors puts it, "Unlike flowing streams and rivers, water resides in lakes for long periods of time."

Chloride pollution in Minnesota

When there's too much salt in a lake, the chloride changes the composition of the plankton, which is the most basic fish food. That can change the number or type of fish that live in the lake. If the chloride pollution gets extreme, the oxygen level in the water can get so low that all aquatic life gets smothered, the researchers say.

According to the Minnesota Pollution Control Agency, 47 bodies of water in the state have too much chloride to meet water quality standards. 39 of them are in the Twin Cities area.

Hilary Dugan, a University of Wisconsin scientist who was the lead researcher for the Cary Institute's study, told the Star Tribune the dozens of small lakes in the Twin Cities area are prone to pollution from road salt.“The smaller the lake, the more easily you load it with salt,” she says.

The MPCA says in a typical winter about 350,000 tons of salt are scattered on Twin Cities roads. They offer ten tips to help reduce road salt pollution. One of them: shovel. The more snow and ice you remove yourself, the less salt you'll need to put down.

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