![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Fox River / Green Bay Mass Balance Study
- assessment of the technical and economic feasibility of the mass balance approach for use in the management of pollutant loadings and ecosystem impacts,
- calibration of mass balance models for understanding the sources, transport routes, fate, and effects of pollutants in the Green Bay system,
- identification of the major sources of contaminants entering the Green Bay system and provide a ranking of relative significance, and
- demonstration of methods and priorities for further studies of toxic contaminants in large aquatic systems such as the Great Lakes.
- assessment of the technical and economic feasibility of the mass balance approach for use in the management of pollutant loadings and ecosystem impacts,
- calibration of mass balance models for understanding the sources, transport routes, fate, and effects of pollutants in the Green Bay system,
- identification of the major sources of contaminants entering the Green Bay system and provide a ranking of relative significance, and
- demonstration of methods and priorities for further studies of toxic contaminants in large aquatic systems such as the Great Lakes.
Preliminary results of the system mass balance indicated that the primary source of PCBs to Green Bay was the Fox River. Specifically, PCBs from sediments in the upper and lower Fox River were the primary contributors of the contaminant; other tributaries, the atmosphere, and point sources were relatively minor source components. Largest losses from Green Bay were due to volatilization to the atmosphere and a relatively large outflow of PCBs through the Green Bay/Lake Michigan boundary into northern Lake Michigan. Model forecasts were propagated through the suite of models through to the food chain model and indicated a large difference between the no further action and an optimal remedation of Fox River sediments. The no further action forecast indicated that PCB concentrations in the Fox River walleye fishery would not decline to desirable concentrations in the foreseeable future. A forecast of the maximum anticipated sediment remediation in the upper and lower Fox River system indicated that PCB concentrations in walleye would reach desirable levels in approximately 10 years after sediment removal. Based upon the results of this mass balance modeling study, several agencies are presently focusing their attention on remedial options for sediments.
PCBs have been a known, long-term stressor to resident biota populations and have closed a considerable number of the commercial and recreational fisheries for many years due to human health considerations from consumption. As an exemplary species, the walleye fishery and supporting food chain were used as a target endpoint in the modeling framework. The framework included a suite of models including hydraulic transport, eutrophication, solids, sorbent dynamics, sediment resuspension, sorbent-toxics, and food chain bioaccumulation. Models were used for 3 geographic areas: upper Fox River, lower Fox River, and Green Bay proper. Within the modeling framework, the goal was to determine the optimal combination of actions (no further action, regulatory, and/or remedial) for the reduction of PCB concentrations in walleye to desirable levels and the time for response.
The Fox River/Green Bay Mass Balance Study was conducted to demonstrate the feasibility of the mass balance modeling framework for managing toxic substances in the St. Lawrence Great Lakes using a large embayment as an example. The study was a cooperative partnership among numerous federal, state, and local agencies, the academic community, the public, and private sector, and was in support of the lower Fox River/Green Bay Remedial Action Plan. The mass balance approach is based upon the principle of conservation of mass, energy, and momentum as applied to the evaluation of sources, transport, fate, and effects of anthropogenic substances. The contaminants of interest were PCBs, dieldrin, lead, and cadmium. Specific objectives included:
PCBs have been a known, long-term stressor to resident biota populations and have closed a considerable number of the commercial and recreational fisheries for many years due to human health considerations from consumption. As an exemplary species, the walleye fishery and supporting food chain were used as a target endpoint in the modeling framework. The framework included a suite of models including hydraulic transport, eutrophication, solids, sorbent dynamics, sediment resuspension, sorbent-toxics, and food chain bioaccumulation. Models were used for 3 geographic areas: upper Fox River, lower Fox River, and Green Bay proper. Within the modeling framework, the goal was to determine the optimal combination of actions (no further action, regulatory, and/or remedial) for the reduction of PCB concentrations in walleye to desirable levels and the time for response.