ST. PAUL — Environmental advocates trying to stop a proposed copper-nickel mine in northeastern Minnesota launched an ad campaign on Monday aimed not at the company behind the project but at Gov. Mark Dayton, hoping to persuade the Democrat to require stronger environmental protections.

The latest environmental review of PolyMet Mining Corp’s open-pit mine, released by the Department of Natural Resources last week, did little to assuage concerns of a coalition of environmental groups called Mining Truth, despite finding that the mine likely wouldn’t significantly impact water quality. In a statewide ad expected to begin airing this week, the group shows video of a massive spill of mining waste in Canada and calls on Dayton to reject the mine’s waste storage system they say could result in a similar accident in Minnesota.