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Bioavailability Of Mercury In The Great Lakes Basin

June 01, 2017

Many fish in the Great Lakes Basin are contaminated by the most toxic form of mercury - methylmercury - and government health agencies issue fish consumption advisories to limit public exposure to this contaminant. The concentration of methylmercury in fish is not necessarily connected to the concentration of mercury in their immediate surroundings. Much of the methylmercury that enters Lake Michigan from tributary rivers appears to come from watersheds with large wetlands, not heavily industrialized regions. In addition, the mercury that contaminates sediments in waters around one industrial area - the city of Green Bay, Wis. - appears to be bound to the sediments in a way that keeps it from undergoing processes that otherwise would transform it into a more toxic form.

The transformation of mercury into methylmercury is caused by bacteria, and this process has been documented in wetlands and in sediments of lakes. This natural process appears to be creating more methylmercury in wetlands around Lake Michigan than in heavily industrialized areas. The situation in the waters around Green Bay, Wis., might be unique to the area. The form of mercury that has entered the Fox River - possibly from industrial uses - apparently binds very tightly to sediment particles, and this has obstructed the methylation process in parts of the Fox River and in portions of Lower Green Bay.

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CONTACT: James Hurley, (608) 262-1136, hurleyaqua.wisc.edu

Source: UW-Madison research part of international mercury conference

Contact: Kathleen Schmitt
University of Wisconsin-Madison