Minnesota Pollution Control Agency to set sulfate standards Thursday

Kristoffer Tigue

State grain may be in danger from high concentrations of a mineral salt that is produced by metal mining and other industrial discharge.

According to the Star Tribune, sulfate has long been associated with inhibiting the growth and production of wild rice and other plants, particularly up north in Minnesota's Iron Range. The Minnesota Pollution Control Agency will decide on Thursday whether or not to change the current standard of sulfate allowed in waters where wild rice grows, currently 10 parts per million.

"When you get sulfate concentrations in lakes that start to exceed 10 milligrams per liter the wild rice abundance becomes sparse," said University of Minnesota Duluth biology professor John Pastor. "That was determined back in the 1940's by a botanist who worked for the DNR at the time."

From that research the MPCA set standards for how much sulfate was allowed to be discharged into waters inhabited by wild rice, Pastor said, but those standards were rarely enforced. Now the recent debate over constructing new mines in northern Minnesota re-sparked interest in those standards, he said.

According to Minnpost, in 2011 Legislature mandated the state conduct research, including a three-year survey of more than two dozen lakes, to find out just how harmful sulfate is on the production of wild rice.

Pastor was part of that research and said it's not the sulfate itself that harms wild rice but rather sulfide, which is created when sulfate is exposed to certain bacteria that's present in calmer bodies of water like lakes.

Pastor said "sulfate by itself has no effect on the wild rice" but that when it's converted into sulfide, two things happen — the sulfide inhibits important developmental stages of the wild rice seeds and iron sulfide is created, which attaches itself to the roots of the plant and further complicates its reproduction.

"It's a complicated issue," he said because the current standard refers to sulfate, not sulfide. He said he believes the current sulfate standards should be able to keep sulfide levels low enough for wild rice sustainability but he hopes the MPCA doesn't decide to allow higher concentrations in waters where it grows.

"I think wild rice should be protected," Pastor said. "It's the state grain. It's the only aquatic grain in North America."