A preliminary study of the Hg flux from selected Ohio watersheds to Lake Erie

New measurements of riverine dissolved and particulate Hg fluxes into Lake Erie from 12 northern Ohio watersheds have been determined from samples collected in April 2002 and analyzed using ultra-clean techniques with cold-vapor atomic fluorescence spectrometry. Total Hg concentrations ranged through 2.5–18.5 ng L−1, with a mean of 10.4 ng L−1 with most Hg in particulate form. Dissolved Hg concentrations ranged through 0.8–4.3 ng L−1, with a mean of 2.5 ng L−1. Highest total Hg concentrations were observed in western rivers with primarily agricultural land use and eastern rivers with mixed land use in their watersheds. Total suspended solid concentrations ranged through 10–180 mg L−1 with particulate Hg concentrations ranging through 47–170 ng g−1, with a mean of 99 ng g−1. Particulate Hg was similar to published data for central Lake Erie bottom sediments but much lower than for bottom sediments in western Lake Erie. Total Hg concentrations were positively correlated with suspended sediment concentrations and negatively with dissolved image concentrations. The total estimated annual Hg fluxes from these rivers into Lake Erie is estimated to be 85 kg, but because only one event was sampled during high flow conditions, this may be an overestimate. This is much lower than previous published estimates of riverine Hg input into Lake Erie.