The findings of this research suggest that the methylation process occurs amidst the rocks and gravel at the bottom of streams and in the sandy landscape that underlies coniferous forests in the Upper Peninsula. However, these findings are not specific to just Lake Superior and the Upper Peninsula: they confirm the importance of groundwater as a source of methylmercury to watersheds around the Great Lakes.
CONTACT: James Hurley, (608) 262-1136, hurley@aqua.wisc.edu
Bioavailability of Mercury in the Great Lakes Basin:
Thursday, Aug. 10, 10 a.m., Grand Terrace: 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 th
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Contact: Kathleen Schmitt
media@mercury2006.org
608-262-6393
University of Wisconsin-Madison
3-Aug-2006