COMMUNITY VOICES | PolyMet supporters spread misinformation concerning efficacy of iron amendment for Minnesota waters


Fear-mongering is the latest buzzword being used by the sulfide mining industry and its supporters, used to divert attention away from the toxic metal poisoning of our children; primarily the result of a taconite industry that does not meet standards. If the grossly underestimated calculations for water flowage, water seepage, and mercury levels discovered in PolyMet’s SDEIS are any indication; the sulfide mining industry is planning to do the same. While PolyMet supporters are busy spreading misinformation.

It would have been advisable for PolyMet shareholder Harlan Christensen to do more reading before he wrote his MinnPost piece, “Iron Range sulfide mining can be done without harming wild rice or raising mercury levels.” Wildly exaggerating, he claimed that there is “widely accepted scientific evidence that iron reduces mercury methylation.”

The research he referred to, from a single early University of California, Berkeley, study in 2003, has been ongoing and was revised in 2010: “Impact of iron amendment on net methyl mercury export from tidal wetland microcosms” (including referenced supporting material).’10EST-27-HgFeWetland.pdf The Berkeley research is still unfinished and flawed. It has not been tested in the field. Christensen has misrepresented the research, and used it inappropriately. It must be studied in its totality and in detail, recognizing that there is a distinct difference between saltwater and freshwater environments.


The rest of the story

The Berkeley research is not comparable or relevant to northeastern Minnesota. Its focus was on ocean tidal salt marshes and pools, about as far from the physical, chemical, and biological interactions of Minnesota’s freshwater aquatic ecosystems as it is possible to get.

Christensen stated: “Iron makes the difference, and we are talking about the Iron Range, right?” Wrong. The California researchers used ferrous chloride to treat their marine microcosms, a soluble, reduced form of iron.  This treatment contrasts drastically with “Iron Range iron” which is not soluble as oxidized mineral forms; iron oxides such as magnetite and hematite.

Concerning mercury and sulfur minerals in vegetated microcosms the researchers stated: “The formation of these minerals [FeS and FeS2] could also be important to Hg bioavailability since they can be important scavengers of Hg (II), and mercury can coprecipitate with authigenic pyrite in marine sediments. In both cases, it is possible that mercury could be rendered less bioavailable. If this occurred following an iron amendment, it could provide a long-term means of reducing MeHg production, provided that the minerals are prevented from reoxidizing and releasing the associated mercury. However, it appears that iron-sulfur minerals did not affect the microcosms in this way, since the inorganic mercury concentrations were similar for all groups. It is possible that the high concentrations of porewater DOC [dissolved organic carbon] inhibited sorption to the minerals by forming complexes with Hg.” (Italics added) 

Apparently unrecognized by researchers at Berkeley, their iron treatment acted directly on the mercury to change its form to elemental mercury, which then left the microcosm as a gaseous vapor. In the real world, this elemental mercury would cycle back through dry or wet deposition. See S6 or S8 in the study’s supporting material, which shows the total mercury being much less in the iron(II) additions than in the controls.

Yet the lowest iron added to the system [devegetated microcosm] is higher in methyl mercury than the methyl mercury in the controls, making the conditions ‘worse’ and stimulating the formation of methyl mercury. As was stated, This phenomenon warrants further attention if an iron amendment is used at the field scale because it would be problematic if elevated MeHg production occurs in areas that receive lower-than planned iron doses.” (Italics added)

As the Berkeley research cautioned in 2010: “Research at the field scale is needed to determine the efficacy of an iron amendment under field conditions, and if an amendment is effective for longer than 12 weeks or if repetitive dosing would be needed. Additionally, unintended consequences of adding iron to the ecosystem, including toxicity to wetland vegetation, must be taken into account to ensure that changes that alter habitat quality do not occur.”


A dangerous and foolish game

In Minnesota, to say that waters with high iron content can handle more sulfates or that iron can control methyl mercury is a dangerous and foolish game to play; particularly when the stakes are the health and intellect of our children. The Berkeley study does nothing to change the odds. The Berkeley study does nothing to change the present high levels of toxic mercury exposure in our children. Responsible mining officials must act to reduce toxic metal and mineral exposures in every way possible. That includes discarding the “not economically feasible” excuse, and putting an end to the accepted stratagem of passing the costs – the health consequences – to their workers and to our children.


I would suggest everyone read, “Some Ecosystems will Respond to Reductions in Mercury Emissions,” noting: “Forest canopies were found to be very active interfaces that accumulate atmospheric mercury. Year-round studies showed that with the onset of the annual autumn leaf fall, a substantial influx of mercury (heretofore greatly underestimated as a terrestrial mercury source) is introduced to the land surface, soils, and the watershed in general. Mercury researchers across the globe are now reevaluating whether deposition monitoring in the form of precipitation in open settings is a reliable estimate of mercury loadings to watersheds.” 2010.pdf This important issue was not thoroughly evaluated by PolyMet or by Minnesota’s cooperating agencies in the NorthMet SDEIS.