DEVELOPMENT OF A PCB MASS BALANCE AND BIOACCUMULATION MODEL IN SUPPORT OF THE LAKE ONTARIO LAKEWIDE MANAGEMENT PLAN (LaMP)

The Four Party Secretariat (U.S. Environmental Protection Agency, New York State Department of Environmental Conservation, Environment Canada and the Ontario Ministry of Environment) is working to develop a load reduction strategy and schedule for priority contaminants in Lake Ontario, as a part of the mandated Lake Ontario Lakewide Management Plan (LaMP) pursuant to Annex 2 of the Great Lakes Water Quality Agreement (International Joint Commission, 1987). The LaMP is focusing on the removal of lakewide beneficial use impairments being caused by a list of priority contaminants, which include PCBs. Also, Lake Ontario is listed by New York State on the 2002 Section 303(d) list of waters that are impaired by fish consumption advisories, thus triggering the need for a TMDL for PCBs. In order to support the LaMP with regard to control of these priority contaminants and potentially the PCB TMDL, we have developed a toxic chemical mass balance and bioaccumulation model called LOTOX2.This paper describes the development of LOTOX2, which is a finite-segment hydrophobic organic chemical mass balance and food chain bioaccumulation model, with water circulation driven by a hydrodynamic (Princeton Ocean Model). The model has been calibrated for total PCBs (tPCB) using long-term data and a reconstructed loading history to conduct a long-term hindcast of 137Cs and tPCB in water, bottom sediments, and adult lake trout. Construction of the historical contaminant loading time series for the watershed was a challenging task. This paper describes the details on the development of loading series and the use of LOTOX2 for management applications to evaluate the effects of potential PCB load reduction strategies on tPCB concentrations in Lake Ontario.Results of management forecast runs show that the lake is not yet at steady-state with current loads. It will take approximately 30 years for PCB concentrations in lake trout to decrease 95% of the way to their steady-state value of ˜0.4 ppm if year 2000 loads remain constant. This represents the upper bound on long-term lake response. The lower bound is determined if all external loads are instantaneously eliminated in the year 2000. In that case, the lake trout will reach a steady-state PCB concentration of approximately 0.05 ppm (the uniform Great Lakes protocol value for unrestricted consumption).