Total mercury has been determined in 163 samples of the topmost 3 cm of sediment taken from Lake Huron during 1969. Total mercury values range from 54 to 805 p.p.b. with a mean of 222 p.p.b. and a standard deviation of 162 p.p.b. The mercury distribution in the lake sediments shows a trend for increasing concentration from nearshore and mid-lake shallow water, coarse sediment deposits outwards into the fine-grained sediments in the deeper water basins. The application of a quartz correction to compensate for the dilution by an inert constituent reveals two major anomalies of higher mercury concentration. The Saginaw anomaly occurs in the southern basins of the lake and is believed to be due to the input of industrial mercury from Saginaw Bay; the Bruce anomaly in the northeastern part of Manitoulin basin is believed to be due to the weathering of sulfide deposits with subsequent concentration in the lake sediments being related to major water circulation patterns in the lake. From statistical analysis the mercury is believed to be bound in the sediments predominantly adsorbed or complexed by organic matter with subsidiary adsorption by the surfaces of iron sulfides and hydrated iron oxide – inorganic phosphorus complexes.

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