Mercury in Green Bay, Lake Michigan surficial sediments collected between 1987 and 1990

Sediments were collected by gravity core from 74 locations in Green Bay, La ke Michigan. Surficial sediments (0 to 1 cm depth) from these stations were analyzed for total mercury for the purpose of describing the horizontal va riation of mercury in Green Bay sediments, estimating mercury fluxes to sur ficial sediments, and identifying potential sources of mercury. With concen trations 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 0.2 8 mg/kg. Surficial sediment mercury concentrations were highest along the e astern shore between the cities of Gr-een Bay and Sturgeon Bay. Elevated co ncentrations were also found near Escanaba and west of Chambers Island. Low est concentrations were found north, south, and west of Washington Island a nd near the Little Suamico River. Mercury fluxes ranged between 0.03 and 10 0 ng/cm(2)/y, with a mean of 20 ng/cm(2)/y. Only 14% of this flux is delive red by regional atmospheric sources. The Fox River is the dominant contribu tor, and the majority of the total mercury flux to the bay is delivered by the rivers that are tributary to the bay.