Mercury in Green Bay, Lake Michigan Surficial Sediments Collected between 1987 and 1990

Abstract

Sediments were collected by gravity core from 74 locations in Green Bay, Lake Michigan. Surficial sediments (0 to 1 cm depth) from these stations were analyzed for total mercury for the purpose of describing the horizontal variation of mercury in Green Bay sediments, estimating mercury fluxes to surficial sediments, and identifying potential sources of mercury. With concentrations ranging between 0.006 and 1.0 mg/kg, the surficial sediments had a mean mercury concentration of 0.36 mg/kg. The median concentration was 0.28 mg/kg. Surficial sediment mercury concentrations were highest along the eastern shore between the cities of Green Bay and Sturgeon Bay. Elevated concentrations were also found near Escanaba and west of Chambers Island. Lowest concentrations were found north, south, and west of Washington Island and near the Little Suamico River. Mercury fluxes ranged between 0.03 and 100 ng/cm 2/y, with a mean of 20 ng/cm 2/y. Only 14% of this flux is delivered by regional atmospheric sources. The Fox River is the dominant contributor, and the majority of the total mercury flux to the bay is delivered by the rivers that are tributary to the bay.