EPA Research Partner Support Story: Modeling bioaccumulation of PCBs and mercury in fish
Partner: Minnesota Pollution Control Agency (MPCA)
Challenge: Addressing Beneficial Use Impairments through tracking and remediation of bioaccumulating contaminants
Resource: Modeling bioaccumulation of PCBs and mercury in fish
Project Period: 2017 – Present
The St. Louis River is listed as a Great Lakes Area of Concern (AOC) under the Great Lakes Water Quality Agreement of 1987. This AOC has several Beneficial Use Impairments including loss of fish and wildlife habitat, excess loadings of sediment and nutrients, degradation of aquatic invertebrate communities (benthos), and restrictions on fish and wildlife consumption. MPCA conveyed a need to identify improvements and advance progress toward removing use impairments and eventual AOC delisting.
“EPA ORD's Great Lakes Toxicology and Ecology Division has been instrumental in providing data, analytical expertise and guidance to support MPCA’s efforts to remove Beneficial Use Impairments (BUI's) in the St. Louis River Area of Concern (AOC) in Duluth, MN and Superior, WI. This AOC is the largest and most complex of the 43 legacy pollution sites surrounding the Great Lakes in the U.S. and Canada. EPA's work on aquatic macrophyte models, bioaccumulative compounds in fish tissue, benthic invertebrate communities and spatial data sets has accelerated the implementation of our plan to complete all project work in the AOC by 2020 so that BUI's can be removed by the target date of 2025.” – MPCA John Linc Stine (former Commissioner)
One of the critical impairments identified for this AOC is restriction of fish and wildlife consumption. Both Minnesota and Wisconsin have posted fish consumption advisories for the St. Louis River because fish have elevated mercury and polychlorinated biphenyl (PCBs) concentrations. Bioaccumulation of dioxins and furans in the Thomson and Scanlon reservoirs are also a concern for fish, wildlife and human health. MPCA identified the need to develop approaches to establish remediation targets for these and other bioaccumulating contaminants, and monitoring designs to track progress after sediment remediation has occurred.
EPA ORD researchers worked with state agency staff to develop a geospatial, habitat-based model of fish bioaccumulation of PCBs to help determine the extent of PCB contamination in the AOC. The model is being used to screen for contamination “hot spots,” determine remediation targets for contamination, and develop monitoring plans for future assessments. ORD researchers also led a multi-federal/state agency team to apply cutting-edge chemical tracers to identify the source and pathways of mercury contamination in the AOC. The tracers are being applied to determine the role of legacy mercury contamination in the AOC, and aid in establishing a mercury-specific remedial target. Finally, once the remediation of dioxins and furans in the Thomson and Scanlon reservoir occurs, state agencies will implement a tracking approach developed by EPA ORD researchers to determine success of the activities.