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Lake Michigan Mass Balance Study - Mercury
LMMB Study
Overview- The Issue: Are sediments, air, land, and water sources or pathways of contamination that affect the integrity of the ecosystem?
- What is the Lake Michigan Mass Balance Study?
- Sample Design and Sample Collection
- PCBs
- Atrazine
- Mercury
- Nutrients-Eutrophication
Lake Michigan Mercury
The objective of the mercury investigation was to provide a mass balance for total mercury. Methylmercury was not directly measured for the LMMB Study. The loadings of mercury from the major monitored and unmonitored tributaries are provided in Figure 13 . The greatest load of total mercury is contributed by the Fox River.
Total mercury was detected in all of the fish samples collected for this study. Mercury concentrations in adult lake trout ranged as high as 396 ng/g and averaged 139 ng/g. In coho salmon, mercury concentrations ranged as high as 127 ng/g and averaged 79.9, 20.6, and 69.0 ng/g in hatchery, yearling, and adult salmon, respectively. Mercury concentrations in lake trout were significantly higher than in adult or yearling coho salmon. Adult coho salmon also were significantly higher in mercury concentrations than yearling coho, which contained the lowest mean concentration of mercury.
LMMB Major Findings: Mercury
- Fox River 101 kilograms per year
- Sheboygan River 1 kilograms per year
- Milwaukee River 3 kilograms per year
- Grand Calumet River 6 kilograms per year
- St. Joseph River 21 kilograms per year
- Kalamazoo River 17 kilograms per year
- Grand River 16 kilograms per year
- Muskegon River 2 kilograms per year
- Pere Marquette River 3 kilograms per year
- Manistique River 4 kilograms per year
- Menominee River 14 kilograms per year
- Total mercury for monitored tributaries 188 kilograms per year
- Total mercury for unmonitored tributaries 41 kilograms per year
- The major source of mercury to the lake is from atmospheric deposition.
- Most Lake Michigan lake trout and coho salmon exceed the EPA guidelines for unrestricted consumption.
- Modeling results suggest that a significant amount of the existing mercury settling out of water is being recycled back into the system.