Heavy metals used in industrial and manufacturing processes can present health and management challenges when they accumulate in aquatic ecosystems. While the fate and transport of certain legacy metals (e.g., mercury) are well-studied, there are critical knowledge gaps in the spatial distribution and temporal patterns of metals in the Laurentian Great Lakes in relation to changes in industrial uses within the watershed and airshed. As part of the EPA Great Lakes Sediment Surveillance Program, we analyzed metals in surface sediments and sediment cores collected throughout Lake Superior to identify tributary sources of metals, better understand their fate and burial, and evaluate how concentrations have changed through time. Preliminary findings indicate that metals distributions in surface sediments (< 5 y) reflect the underlying geology and industrial activities (e.g., mining, forestry) in the watershed: (1) lead and copper were highest between Isle Royale and the Keweenaw Peninsula; (2) mercury concentrations were highest near the Kaministiquia River and in western Lake Superior; and (3) arsenic concentrations were highest near Silver Bay and in western Lake Superior. Interestingly, surface sediments northeast of Munising, MI, had much higher concentrations of arsenic, copper, mercury, and lead compared to nearby sampling locations. Sediment cores revealed that (1) lead concentrations peaked in the 1950s-1960s, (2) copper concentrations peaked in the 1930s near Isle Royale, and (3) arsenic concentrations peaked in the early 1970s near Duluth-Superior entries.

Primary Presenter: Christopher Filstrup, University of Minnesota Duluth (filstrup@d.umn.edu)

Authors:

Christopher Filstrup, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN USA  (filstrup@d.umn.edu)

Euan Reavie, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN USA  (ereavie@d.umn.edu)

Sarah Janssen, Upper Midwest Water Science Center, U.S. Geological Survey, Madison, WI USA  (sjanssen@usgs.gov)

Michael Tate, Upper Midwest Water Science Center, U.S. Geological Survey, Madison, WI USA  (mttate@usgs.gov)

Chan Lan Chun, Civil Engineering Department & Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN USA  (chun0157@d.umn.edu)

Zach Wagner, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN USA  (wagn0671@d.umn.edu)