Science: Effects of Sulfate Pollution
What does the science say about sulfate and wild rice?
In 2011, the Minnesota Legislature funded new scientific research with the goal of weakening or repealing the wild rice sulfate standard. However, the new research – in the field, in test tubes, and growing wild rice in tanks and buckets – all confirmed that the 10 mg/L wild rice sulfate standard was needed and reasonable.
What recent scientific research supports the wild rice sulfate standard?
- Dr. Pastor found in a series of controlled experiments in outdoor mesocosms (large tanks) that adding sulfate to the water resulted in increased sulfide in the sediments and a decline in wild rice. Dr. Pastor explained:
- Dr. La-Fond Hudson tested the hypothesis that high levels of iron would protect wild rice. This hypothesis was proposed by the mining industry and the MPCA as justification for weakening the wild rice standard. But Dr. Hudson found – in a series of experiments that involved growing wild rice in buckets — that high levels of iron did not protect wild rice from harm caused by sulfate. Instead, iron sulfide accumulated on wild rice roots, interfering with nutrient uptake. As a result, wild rice seeds were fewer, lighter, and thus, less likely to generate new plants.
- Dr. Pastor explained the implications of this research in an expert opinion provided to the Administrative Law Judge in support of preserving Minnesota’s wild rice sulfate standard:
The MPCA assumes that any precipitation of sulfide by iron helps to protect wild rice. Our experimental mesocosm research has substantially undermined this assumption.
We learned that iron sulfide precipitates rapidly on wild rice roots in midsummer at the time when the plants are beginning to flower and take up additional nutrients for the ripening seeds. The iron sulfide precipitates gave the roots a black appearance, compared to amber or rust colored roots on healthy plants exposed to sulfate concentrations near the current fixed standard of 10 mg/L. Seed nitrogen, seed count and seed weight were all markedly reduced in plants with back root surfaces exposed to high sulfate surface water concentrations (300 mg/L) because these black iron sulfide precipitates inhibit the uptake of nutrients necessary for the filling and ripening of seeds necessary for propagation of wild rice.
[B]ased on my training and experience, it is my opinion that the weight of the scientific evidence supports retaining Minnesota’s existing sulfate standard of 10 mg/L to protect wild rice.
- University of Minnesota (U of M) mathematics professor emeritus, Joel Roberts, PhD, also analyzed the MPCA’s proposed equation that would replace Minnesota’s 10 mg/L wild rice sulfate standard. He pointed out that the mathematical formula “is inadequate for explaining the data from the Wild Rice Field Study” and “inadequate for protecting Minnesota’s Wild Rice.”
- Administrative Law Judge LauraSue Schlatter disapproved the MPCA’s proposed rule to repeal Minnesota’s wild rice sulfate standard. She concluded that the equation proposed by the MPCA to allow more sulfate in waters with a high concentration of iron was not protective of wild rice:
Dr. Pastor’s continuing mesocosm research has indicated that, while increased iron may counter the toxicity of sulfide to wild rice seedlings in the springtime, iron sulfide plaques form and precipitate on the plants’ roots during the flowering and seed production phases of the wild rice life cycle. These plaques result in fewer and smaller seeds, with reduced nitrogen content, leading to extinction of the wild rice plant within 4 or 5 years at about 300 mg/L of sulfate, and greatly reducing wild rice plant population viability at lower concentrations of sulfate.
Read Dr. John Pastor’s 2016 Annual Report on The Biogeochemical Habitat of Wild Rice: identifying the black coatings on wild rice roots in tanks with more than 50 mg/L of sulfate as iron sulfide plaques.
Read the December 2015 technical opinion of mathematics professor emeritus, Joel Roberts, Ph.D., explaining flaws in the MPCA’s wild rice “equation” proposal as an unreliable method to predict sulfide in sediments.
Read the November 2015 technical opinion of international expert on structural equations, Bill Shipley, Ph.D., challenging use of MPCA’s formula to predict levels of sulfate that would protect wild rice.
Read the December 2015 technical opinion of UMD biology professor emeritus, David Schimpf, Ph.D.: explaining that from an ecological perspective, MPCA’s proposal “redefines ‘protect wild rice’ into a much weaker sense than that of the existing standard.”
The Duluth News Tribune discussed on July 19, 2016:
“We already know that the existing sulfate limit is effective and reasonable. But [M]PCA, ignoring evidence that the equation they are developing is ﬂawed, continues down this path and away from protecting wild rice,” Maccabee said. “They are developing this very complex and ﬂawed process based on pressure from the mining industry and Iron Range lawmakers when their primary concern should be protecting wild rice.”
What scientific research supported the wild rice sulfate standard in 1973?
The wild rice sulfate standard was adopted by the MPCA and approved the by the EPA in 1973 on the basis of scientific field research conducted by John Moyle on hundreds of water bodies from the 1940’s through the 1970’s. Dr. Moyle wrote in 1944:
Dr. Moyle confirmed in a 1975 memo to MPCA, after decades of additional research:
What contributions did citizen scientists make early in the review process?
Len Anderson, a biology teacher and experienced hunter, fisher, and ricer, canoed the Partridge River with retired mine engineer and outdoorsman, Bob Tammen, to sample water quality and document conditions of wild rice beds. Upstream, they found plentiful, healthy natural wild rice beds. But downstream, the beds were damaged from decades of mine wastewater discharges. Anderson and Tammen concluded that current field data required preservation of the wild rice sulfate standard.
Len Anderson found impaired wild rice in the Partridge River downstream of historical sulfate pollution from mining.
How does sulfate affect mercury contamination of fish and harm Minnesota lakes?
- Sulfate more than doubles the release of inorganic mercury from sediments as compared to a low-sulfate control. With sulfate levels of either 100 mg/L or 300 mg/L, methylmercury increased 5.9 times as compared to the low-sulfate control. Methylmercury is the form of mercury that accumulated in the food chain and contaminates fish.
- In addition, higher sulfate released nutrient chemicals – nitrogen and phosphorus – from sediments to water. Excessive nitrogen and phosphorus contribute to algae blooms in once-clear Minnesota lakes.
The plain English summary of Dr. Myrbo’s article states:
This study demonstrates that adding sulfate to a wetland can not only produce toxic levels of sulﬁde but also increase the surface water concentrations of nitrogen, phosphorus, mercury, and methylmercury.
Information on the risks of methylmercury to human health, particularly harm to the developing brains of fetuses, infants, and children is summarized in Expert Opinion of Duluth child psychiatrist Dr. Margaret Saracino.