Lake Michigan Mass Balance Study - PCBs

Figure 5. Trends of Total PCBs in Various Lake Michigan Media. (PCBs in Lake Michigan sediments show a gradual increase from 1930 through about 1950 and then a sharp increase to about 1960. Concentrations remain high through 1970 with a decline and recovery in the mid to late 1960s. Sediment concentrations decline steadily through 1994 with an increase in 1995.

PCBs in Lake Michigan water show a steep decline from about 1975 through the early 1980s, the remaining low through 1995.

PCBs in Lake Michigan gas phase air show an apparent decline from the mid-1970s through about 2000.

PCBs in Lake Michigan lake trout shows a steep decline from the early 1970s to the late 1980s and then a gradual decline through the early part of the 2000s.

All media follow the same declining trend.

Figure 6. Average PCB loads (kg/year) to Lake Michigan from major monitored and unmonitored tributaries, 1994-1995.

• Fox River 216 kilograms per year
• Sheboygan River 12 kilograms per year
• Milwaukee River 11 kilograms per year
• Grand Calumet River 40 kilograms per year
• St. Joseph River 10 kilograms per year
• Kalamazoo River 39 kilograms per year
• Grand River 10 kilograms per year
• Muskegon River 2 kilograms per year
• Pere Marquette River 2 kilograms per year
• Manistique River 1 kilograms per year
• Menominee River 4 kilograms per year

Average PCB for monitored tributaries 347 kilograms per year
Average PCB for unmonitored tributaries 31 kilograms per year