Sediment quality at select sites in the St. Marys River Area of Concern

The St. Marys River is the sole surface outlet from Lake Superior, flowing over 100 km to Lake Huron, and forming part of the international border between Canada (Ontario) and the United States (MI). The river system has been severely impacted by modifications to the hydrology as well as local industrial and municipal discharges, and was designated in 1985 as an Area of Concern (AOC). Since that time, sediments on the Canadian side of the river have been systematically re-sampled, but the US side of the river has received less attention. This paper discusses two recent projects, one completed in 2003 and one completed in 2005, that sought to revisit a variety of sediment localities within the St. Marys River to update sediment contaminant data, and to expand sampling into additional areas of interest on the US side of the border: Munuscong Lake at the southern end of the AOC, and the Little Rapids adjacent to Sugar Island. The primary focus was on surficial sediment contamination, particularly metals shown to be elevated during previous sampling (chromium, nickel, copper). Results show that while Cr, Ni and Cu contamination remains slightly elevated in surficial sediments at some sites in the St. Marys River, the overall trend shows metal concentrations declining to levels consistent with background levels in sediments found in Lake Superior, Whitefish Bay and the St. Marys River.