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METHYL MERCURY IN LAKE MICHIGAN SURFICIAL SEDIMENTS
Citation:
Rossmann, R., K R. Rygwelski, AND J C. Filkins. METHYL MERCURY IN LAKE MICHIGAN SURFICIAL SEDIMENTS. Presented at 2001 International Association for Great Lakes Research Annual Conference, Green Bay, WI, June 10-14, 2001.
Description:
Sediment samples were collected from Lake Michigan between 1994 and 1996. One purpose of the sampling was to define the horizontal distribution of methyl mercury in the surficial 1 cm of sediment. Samples were collected from 51 stations using a box core from which subcores for trace metal analysis were sectioned at 1 cm intervals from top to bottom. Methyl mercury samples were stored frozen. Subsamples for methyl mercury analysis were analyzed by aqueous phase ethylation, Tenax trap collection, GC separation, isothermal decomposition and atomic fluorescence detection. Methyl mercury concentrations in surficial sediment ranged between 0.16 and 1.7 ng/g with a mean and median of 0.57 and 0.45 ng/g, respectively. Regions of highest methyl mercury occurred primarily in the northern sedimentary basins of the lake where they were concordant with the bathmetry. This was not true in the southern basin. Highest methyl mercury concentrations did not always occur at the same locations as highest total mercury. Methyl mercury concentration at each station varied between 0.11 and 1.4% of the total mercury concentration. The mean and median fraction of methyl mercury were 0.42 and 0.35%, respectively.