APPLICATION OF A MASS BALANCE AND BIOACCUMULATION MODEL FOR A PCB TMDL IN LAKE ONTARIO

The Lake Ontario ecosystem has experienced significant changes over the last century from the effects of toxic pollution and habitat loss. In 1972, Canada and the United States took actions to ban and control contaminants entering the Great Lakes, and in 1987 renewed the Great Lakes Water Quality Agreement with the goal to restore the overall health of the Great Lakes ecosystem. Today, as a result of these actions, levels of toxic contaminants in the Lake Ontario ecosystem have decreased significantly. However, fish consumption advisories remain in many areas of the Great Lakes basin based on levels of PCBs, mirex, dioxins, and mercury. Lake Ontario is listed by New York State on the 2002 Section 303(d) list of impaired waters. In Lake Ontario, the pollutants listed as causing the fish consumption advisories are PCBs, mirex, and dioxins. Because of this listing, Lake Ontario has been scheduled for a TMDL to be completed by 2011.This paper describes the development of a mass balance and food chain bioaccumulation model, LOTOX2, and its application applied for the purpose of supporting the Lake Ontario LaMP (Lakewide Management Plan) and the TMDL process (DePinto et al. 1997, 1999b). LOTOX2 has been calibrated for tPCB in the lake 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 (DePinto et al. 1998; DePinto et al. 1999a). This paper investigates the utility of using this model to support a TMDL process for PCBs in Lake Ontario. Challenges associated with conducting a TMDL for a bioaccumulative chemical in a large lake whose watershed spans two countries are discussed.