Evaluation of Wild Rice Waters Sulfate Standard

Group of Scientists Will Evaluate the State's Analysis of a Series of Research ProjectsDesigned to Determine Minnesota's Current Sulfate Standard for Wild Rice Waters is Right

Minnesota's approach to protecting wild rice from sulfate pollution faces a key test this week. A group of scientists recruited from around the country will evaluate the state's analysis of a series of research projectsdesigned to determine whether Minnesota's current sulfate standard for wild rice waters is right. Sulfate occurs naturally, but it's also added to water by industry, including wastewater treatment plants and mining operations. TheMinnesota Pollution Control Agencyis bending over backward to makethe processas transparent as possible. But members of its own advisory group are already picking apart the analysis.

The studies included hydroponic experiments in the lab, "mesocosm" experiments in stock tanks, and field surveys of more than 120 sites. The researchers are operating under the theory that sulfate itself does not harm rice, but that bacteria in lake sediments convert it to sulfide, which is known to harm plants rooted in saturated soils.

MPCA's preliminary analysis says the hydroponic experiments showed wild rice can tolerate very high levels of sulfate, but is likely to be harmed at sulfide levels far lower than the current standard. The agency's analysis says the mesocosm experiments showed seed weight, seed viability, and seedlings emerging from the sediment each spring declined with increasing sulfate. Also, there was a positive correlation between sulfate in the surface water and sulfide in the porewater (water in the sediments). And it says the field survey confirms the findings of DNR scientist John Moyle back in the 1940s that wild rice tends to grow in low-sulfate water. Moyle's research was the basis for the standard, established in 1973, of 10 milligrams per liter of sulfate "in water used for production of wild rice during periods when the rice may be susceptible to damage by high sulfate levels."

Industry critics, such as theMinnesota Chamber of Commerce, point to the hydroponic experiments and say a sulfate standard is not needed at all, but if there is one, it should be 1,600 parts per million. That would be more than six times the federal guideline for drinking water. The industry scientists also say the study does not demonstrate a correlation between sulfate in the surface water and sulfide in the porewater.

Source: Minnpost

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