Authors: Twaroski, CJ; Segroves, LI


Cite As:
Twaroski, CJ & Segroves, LI 2011, 'Existing mine pit and natural lakes in northern Minnesota as predictors of total mercury concentration of a mine pit at closure', in AB Fourie, M Tibbett & A Beersing (eds), Proceedings of the Sixth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 565-571,

Download citation as:   ris   bibtex   endnote   text   Zotero

Open pit mining of taconite ore has been ongoing in northern Minnesota since the early 1900s and mine pit lakes are a common feature on the Mesabi Iron Range. The approximate western half of the Iron Range is within the Mississippi River watershed and the approximate eastern half is within the Lake Superior Basin watershed. In the Lake Superior Basin the outflow water from pit lakes is required to meet a standard of 1.3 nanograms per litre (ng/L) for total mercury concentration. The average concentration of mercury in precipitation in northern Minnesota is approximately 12 to 13 ng/L (1996–2009 time period). Available surface water chemistry data indicate that a number of existing mine pit lakes on the eastern end of Minnesota’s Iron Range and several remote lakes in Voyageurs National Park (located about 50 km to the north of the Iron Range) have annual average total mercury concentration in the water column or outflow water that is less than 1.3 ng/L. Characteristics of pit lakes and natural lakes set in bedrock, when compared to other lake-specific research findings in the Upper Midwest, suggest that atmospheric mercury deposited to these water bodies is likely removed from the water column by volatilisation back to the atmosphere and by sedimentation and burial in the bottom sediments. As part of the environmental review and permitting process in Minnesota, mining companies with projects in the Lake Superior Basin watershed are asked to demonstrate that the potential total mercury concentration in the outflow from the closed mine pit will comply with the 1.3 ng/L standard for total mercury. Using data from existing mine pit lakes and natural lakes in northern Minnesota as predictors of future conditions it is likely that a mine pit at closure will comply with the total mercury water quality standard.

Axler, R., Larsen, C., Tikkanen, C. and McDonald, M. (1992) Intensive aquaculture in abandoned Minnesota iron ore pits: Environmental and regulatory perspectives. viewed 28 April 2011: .
Brigham, M.E. (1992) Accumulation of mercury in Minnesota, Alaska, and Wisconsin lakes. Thesis for MS Degree in Civil Engineering, University of Minnesota. Minneapolis - St. Paul, MN.
Brigham, M.E., Olson, M.L. and Dewild, J.F. (1999) Mercury, methylmercury, and other water-quality data from flood-control impoundments and natural waters of the Red River of the North basin, Minnesota, 1997–99. USGS Open File Report 99-273A (p 34).
Chen, C.W., Herr, J.W. and Goldstein, R.A. (2008) Model calculations of total maximum daily loads of mercury for drainage lakes. J. American Water Resources Assoc., Vol. 45, pp. 1295–1307.
Engstrom, D.R. and Swain, E.B. (1997) Recent declines in atmospheric mercury deposition in the Upper Midwest. Environmental Science and Technology, 1997, Vol. 31, pp. 960–967.
Goldstein, R.M., Brigham, M.E., Steuwe, L. and Menheer, M.A. (2003) Mercury data from small lakes in Voyageurs National Park, northern Minnesota, 2000–02. U.S. Geological Survey, Open File Report 03-480.
Grigal, D.F. (2002) Inputs and outputs of mercury from terrestrial watersheds: A review. Environ. Rev., 2002, Vol. 10, pp. 1–39.
Kratz, T.K., Webster, K.E., Bowser, C.J., Magnuson, J.J. and Benson, B.J. (1997) The influence of landscape position on lakes in northern Wisconsin. Freshwater Biology, 1997, Vol. 37, pp. 209–217.
Lorey, P. and Driscoll, C.T. (1999) Historic trends of mercury deposition in Adirondack lakes. Environ. Sci. Technol., Vol. 33 (5), pp. 718–722.
MDNR (2009) Minnesota Department of Natural Resources. Sulphate and Mercury Chemistry of the St. Louis River in Northeastern Minnesota. A Report to the Minerals Coordinating Committee. Division of Lands and Minerals, 500 Lafayette Road, St. Paul, MN 55155. Draft Report, June 2009.
MPCA (2008) Minnesota Pollution Control Agency. MERCLKS water ecoregion data. Unpublished data from the Minnesota Pollution Control Agency Environmental Outcomes Division (St. Paul, MN); data as of 22 January 2008.
Porcella, D.B. (1994) Mercury in the environment: Biogeochemistry in Mercury Pollution, Integration and Synthesis, C.J. Watras and J.W. Huckabee (eds), Lewis Publishers, Boca Raton, FL., pp. 3–19.
USDA (1997–2000) U.S. Department of Agriculture. National Weather and Climate Center. Natural Resources Conservation Service. Climate information retrieval for Minnesota, by county. Viewed 26 April 2011,
Watras, C.J. and Morrison, K.A. (2008) The response of two remote, temperate lakes to changes in atmospheric mercury deposition, sulphate, and the water cycle. Can. J. Fish. Aquat. Sci., Vol. 65, pp. 100–116.
Watras, C.J., Morrison, K.A., Hudson, R.J.M., Frost, T.M. and Kratz, T.K. (2000) Decreasing mercury in northern Wisconsin: Temporal patterns in bulk precipitation and a precipitation-dominated Lake. Environmental Science and Technology, Vol 34, pp. 4051–4057.
Webster, K.E., Kratz, T.K., Bowser, C.J., Magnuson, J.J. and Rose, W.J. (1996) The influence of landscape position on lake chemical responses to drought in northern Wisconsin. Limnol. Oceanogr., Vol. 41(5), pp. 977–984.
Wiener, J.G., Knights, B.C., Sandheinrich, M.B., Jeremiason, J.D., Brigham, M.E., Engstrom, D.R., Woodruff, L.G., Cannon, W.F. and Balogh, S.J. (2006) mercury in soils, lakes, and fish in Voyageurs National Park (Minnesota): Importance of atmospheric deposition and ecosystem factors. Environ. Sci. Technol. 2006, Vol. 40,
pp. 6261–6268.

© Copyright 2021, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
Please direct any queries or error reports to