New Tool Can Determine the Sources of Mercury Found in the Great Lakes

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For the first time, land and resource managers in the Great Lakes will be able to distinguish between the various sources of mercury in the environment, a toxic chemical of significant concern in the region. This is thanks to a new tool that “fingerprints” the mercury, developed by the U.S. Geological Survey and the University of Wisconsin-Madison.

For the first time, land and resource managers in the Great Lakes will be able to distinguish between the various sources of mercury in the environment, a toxic chemical of significant concern in the region. This is thanks to a new tool that “fingerprints” the mercury, developed by the U.S. Geological Survey and the University of Wisconsin-Madison. 

For Lakes Superior and Huron, atmospheric mercury is the dominant form, while in Lakes Erie and Ontario, most mercury comes from industrial activity or runoff from the watersheds of the lakes. Lake Michigan is dominated in some areas by atmospheric mercury, in other areas by industrial activity and in still others by watershed contributions.

Source Contribution of Mercury in Great Lakes Sediment
A map showing the relative concentrations of mercury sources as identified by the fingerprinting tool which include watershed, industrial, and precipitation in the locations of Lake Superior, Lake Huron, Lake Michigan, Lake Erie, and Lake Ontario.

“I’ve been involved in mercury research for nearly 28 years,” said USGS scientist Dave Krabbenhoft, the project chief. “Back in the 1980’s, when I first got into this area of research, I dreamed of a tool that could provide geochemical markers of mercury sources.  That dream has now become reality.”

Determining where the mercury comes from is important, because it informs decisions designed to minimize it.  For example, minimizing industrial sources of mercury alone will not be effective if the majority of mercury entering the Great Lakes is from atmospheric mercury.

“One of the surprising things we saw was just how much of the mercury building up in fish was due to atmospheric mercury,” said Krabbenhoft. “This shows that atmospheric mercury needs to be emphasized, even when the sediments in the Lakes show relatively little atmospheric mercury accumulation.”

Although this fingerprinting tool was pioneered for the Great Lakes, it can be applied elsewhere. A very common situation across the United States and elsewhere is the presence of large amounts of mercury that was released during industrialization, so-called legacy mercury. At these sites, resource managers often lack a tool to help them understand whether it is legacy or other sources that substantively contribute to exposures in fish, wildlife and humans today.

“We are very excited to explore the capability of this new tool to inform resource managers and decision makers responsible for managing these challenging situations,” said Krabbenhoft.

Mercury is a naturally occurring element that can have toxic effects on people’s brains, kidneys and lungs. In certain environments, it can also bind with carbon and hydrogen to become methylmercury, which is far more toxic than elemental mercury. In addition, methylmercury can build up in the tissues of fish and other aquatic organisms, resulting in higher doses when people or other animals eat them.

More information about this new tool can be found online. USGS provides information on mercury sources; mercury cycling in the atmosphere, land surface, lakes, streams and oceans; and bioaccumulation and toxicity of mercury. This information helps land and resource managers understand and reduce mercury hazards to people and wildlife.