Contaminant Trends in Suspended Sediments in the Detroit River-Lake St. Clair-St. Clair River Corridor, 2000 to 2004

Suspended sediments from the Detroit River-Lake St. Clair-St. Clair River corridor over the period of 2000 to 2004 were analyzed to examine the spatial distributions of contaminants including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and mercury. Contaminant spatial distributions were similar over the five-year study period, but concentrations varied considerably among sampling locations. Concentrations of PCBs ranged from 22 to 1,200 ng/g (dry weight) in 2004, and from 10 to 2,700 ng/g (dry weight) in 2000; concentrations of PAHs ranged from 640 to 52,000 ng/g (dry weight) in 2004, and from 240 to 82,000 ng/g (dry weight) in 2000; and concentrations of mercury ranged from 0.063 to 0.478 mg/kg (dry weight) in 2004, and from 0.060 to 0.514 mg/kg (dry weight) in 2002. The highest PCB and PAH concentrations were associated with suspended sediments in the lower and middle reaches of the Detroit River in the area of the Trenton Channel, and the outflow of the Rouge River. The spatial distributions of mercury were more consistent throughout the entire corridor, indicating the presence of sources in both the lower reaches of the Detroit River and the upper reaches of the St. Clair River. Both the Trenton Channel area of the Detroit River and the upper reaches of the St. Clair River are characterized by heavy historical industrial activity, including steel manufacturing and chlor-alkali production.