Mercury Deposition

Mercury is emitted primarily by coal-fired utilities and may be carried thousands of miles before entering lakes and streams as mercury deposition. Mercury can bioaccumulate and greatly biomagnify through the food chain in fish, humans and other animals, initiated via the conversion of non-organic forms of mercury to methylmercury by sulfur reducing bacteria in aquatic sediments. Methylmercury is a potent neurotoxin, and has been shown to have detrimental health effects in human populations as well as behavioral and reproductive impacts to wildlife. Most States, including Minnesota, have consumption advisories for their lakes and streams, warning of mercury-contaminated fish. High concentrations of mercury are measured in sediments and fish tissue, even in remote areas of the Arctic. Recently, elevated methylmercury loads have been monitored in upland bird species. The link between sulfur reducing bacteria and biotic mercury concentrations has led researchers to indicate that reductions in sulfur dioxide emissions and a resulting reduction in sulfate deposition will likely abate mercury concentrations in wildlife. Therefore hard won reductions in sulfur dioxide emissions will result in more than improved visibility and abated acid deposition.

The State of Minnesota has a plan to reduce mercury deposition.

The Superior National Forest has done a lot to monitor and understand mercury.  Many of these efforts are continuing.

  • We have contributed financially to the statewide effort to monitor mercury in gamefish.  The data is compiled by the Minnesota Department of Health and made available online.
  • We have monitored mercury in precipitation.  Data is available online.
  • We have measured mercury in loons
  • We have an ongoing study to determine if our prescribed burning program is causing any changes to the chemistry of lakes or fish


Key mercury references