Global models offer new insights into Great Lakes mercury pollution

Jan. 23 (UPI) -- Members of the Keweenaw Bay Indian Community living on Michigan's Upper Peninsula have a fairly simple question: when is it safe to eat the fish they catch?

To help fish-eaters better estimate their risk of exposure, researchers at Michigan Technological University have developed a model designed to measure the impact of local mitigation efforts, socioeconomic pressures, ecological systems, climate change, land use and other variables on local levels of mercury.

Mercury is an atmosphere-surface exchangeable pollutant, a group of invisible, tasteless contaminants that move efficiently throughout the natural environment.

"We're taking phenomena that act on a global scale and predicting what they will do," Judith Perlinger, professor of environmental engineering at Michigan Tech, said in a news release.

Perlinger said working with members of the Keweenaw Bay Indian Community was an integral part of the work.

"Clearly the issue matters to them, so how can we make the science relevant to them?" she said.

To find out, a team of scientists -- 36 researchers from six different institutions -- adapted a global 3D Eulerian chemical transport model to simulate the movement of mercury from the atmosphere into local marine food chains. Researchers used the model to measure how three different regulator policies would impact the flow of mercury in and around Michigan's Upper Peninsula.

In the first simulation, scientists looked at what mercury exposure would look like if all anthropogenic sources in the region were eliminated. A second simulation measured the impact of a more moderate mercury reduction through local mitigation polices. A third imagined a scenario with minimal regulatory efforts.

Unfortunately, the model failed to provide good news. The findings showed all three scenarios yield elevated mercury levels. For those living in Keweenaw Bay, mercury levels are likely to remain dangerously high for the rest of their lifetimes.

Even if man-made mercury inputs are reduced, researchers determined, the contaminants will continue to be transferred from deposits on the land to the fresh water systems where they're absorbed by fish.

"People assume that what is deposited in a forest is also deposited the same in a lake, which isn't true, so models have been miscalculating," said Noel Urban, a professor of environmental engineering.

The slow feedback between land and water means has caused scientists to previously underestimate the role land-based contaminants can play in future pollution levels.

"This is apparent in the Great Lakes, and the Upper Peninsula is a particularly sensitive landscape to mercury," Urban said.

The new research was published this week in the journal Environmental Science: Processes and Impacts.