Mercury Fire Effects Study

The Issue
Mercury is a leading environmental contaminant that has been identified in both populated regions and remote wilderness areas. Mercury is of particular concern because it biomagnifies up the food chain in aquatic ecosystems. Although the cycling of mercury through forested and aquatic systems has been studied, little is known about the cycling of mercury in response to wildland or prescribed fires. This issue is important because prescribed burns are a useful tool in fuels

Our Approach
This study is determining if additional transport and deposition of mercury is caused by fire. The hypothesis is that prescribed fires will affect mercury cycling by increasing the mobilization and transportation in burned watersheds. It is unknown whether the change in the mercury cycle caused by fire would lead to an increase in fish mercury concentrations.

Mercury contamination in Minnesota and other Great Lake States is of special concern. Fish consumption advisories are already in effect due to the elevated mercury levels in these regions. Within Minnesota, the highest mercury levels are found in the interior lakes of the northeast including the Superior National Forest and in the Boundary Waters Canoe Area Wilderness (BWCAW). Due to the major blowdown event of July 1999, a prescribed burning program was developed by the Superior National Forest for the BWCAW. Our research is utilizing the prescribed burning program to compare undeveloped lakes in both burned (treatment lakes) and unburned (control lakes) watersheds. Mercury cycling is evaluated by measuring total-mercury, methyl-mercury (bioaccumulative form of mercury) and other important ions in precipitation, throughfall, soil, lake water and in 1+ year fish (perch) both pre-burn and post-burn to assess sources of mercury and determine if changes in sources alters the concentration of mercury in fish.

We hope to be able to determine if prescribed fire enhances the watershed transport and bioaccumulation of mercury in fish. This is especially relevant in sensitive regions such as the boreal region where high levels of mercury in fish is already a concern.



  • Northern Research Station
  • University of Minnesota, Department of Soil, Water, and Climate
  • United States Geological Survey



Peer Reviewed Publications

Woodruff, L.G. and W.F. Cannon. 2010. Forest fire effects on mercury in soils in forests in Northern Minnesota. Environmental Science and Technology, 44: 5371-5376.

Witt, E.L., R.K. Kolka, E.A. Nater, and T.R. Wickman. 2009. Influence of the forest canopy on total and methyl mercury deposition in the boreal forest. Water, Air, and Soil Pollution, 199: 3-11.

Witt, E.L., R.K. Kolka, E.A. Nater, and T.R. Wickman. 2009. Forest fire effects on mercury deposition in the boreal forest. Environmental Science and Technology, 43(6): 1776-1782.

Gabriel M.C., R. Kolka, T. Wickman, E. Nater, and L. Woodruff. 2009. Evaluating the spatial variation of total mercury concentrations in young-of-year fish for watershed-lake systems within the southern Boreal Shield. Science of the Total Environment, 407(13): 4117-4126. 

Gabriel M.C., R. Kolka, T. Wickman, E. Nater, and L. Woodruff. 2012.  Latent Effect of Soil Organic Matter Oxidation on Mercury Cycling within a Southern Boreal Ecosystem. Journal of Environmental Quality-Technical Reports, 41:495-505.   

Complete list of Publications/Presentations/Reports