MINNEAPOLIS — The Minnesota Pollution Control Agency said Wednesday that more data analysis must be done to determine whether it will recommend changes to the state's water quality standards to protect wild rice from sulfates.
A preliminary analysis of a two-year study on the issue makes no recommendations for changes to the standard for sulfate discharges at this time but says site-specific standards might be needed for some waters. The analysis also suggests the current standard is within a range suitable for protecting wild rice.
"We're learning it's more complicated than it is simple," said MPCA Commissioner John Linc Stine. "So we have more work to do on that before we can settle on a recommendation or ... recommendations that we know would be more comprehensive and protective."
He said the analysis released Wednesday only begins to look at the complexity of the subject and is not a final answer on water quality standards.
Minnesota limits sulfate discharges from mines and other sources into waters that produce wild rice to 10 milligrams per liter, based on research from the 1940s suggesting that higher levels can stunt development of the plants.
Supporters of iron and copper-nickel mining have argued the standard is obsolete, and the Minnesota Chamber of Commerce has said its own analysis concludes a standard is unnecessary. But the state's American Indian bands fear any weakening could imperil a food source they consider sacred and central to their cultural identity.
The theory behind the study, conducted by scientists at the University of Minnesota and the University of Minnesota-Duluth, is that higher concentrations of sulfates can harm wild rice plants when they're converted into sulfides in the sediments where the plants grow.
The MPCA's analysis found that the amount of sulfide in the sediment is affected by the amount of sulfate in the water as well as the amount of iron in the sediment.
A higher amount of iron in the sediment mitigates sulfide concentrations, so in those areas, a higher level of sulfate in the water might not result in too much sulfide, the analysis found. On the flip side, areas with very low iron levels might require lower sulfate standards.
Because of that, the analysis said, site-specific standards might be needed for some waters.
The MPCA will continue to examine whether the type of water body — lakes, streams or rice paddies — affect wild rice's susceptibility to sulfide.
Stine said the MPCA is working on developing recommendations based on sound science and good policy. He said the agency continues to analyze the data and refine its findings as needed. A scientific review will take place this year and there will be an opportunity for all stakeholders and members of the public to comment before final recommendations are made.
Stine said recommendations could be put forth late this year or early next year, at the earliest.