Trevor Schott collects dissolved organic carbon (DOC) samples on the Sheboygan River. Methylmercury, the form that bioaccumulates in the food chain, levels tend to correlate with DOC. Photo: Chris Babiarz.
Sea Grant Research
Measuring Mercury in Lake Michigan Tributaries
Carolyn Rumery Betz
It’s been 15 years since the EPA initiated the Lake Michigan Mass Balance Study to measure concentrations of mercury, PCBs and other pollutants in the air, water, sediments and food webs of Lake Michigan. Christopher Babiarz is using Sea Grant funding to monitor how mercury has changed in four Wisconsin tributaries. Babiarz is an assistant scientist in UW-Madison’s Environmental Chemistry and Technology Program.
Eleven tributaries in the Lake Michigan watershed were included in the original study. One of them, the Fox River, was the single largest contributor of mercury to Lake Michigan, supplying almost as much mercury as the other 10 tributaries combined, according to the study results published in 2004. The new research project, which includes the Fox River, focuses on the form of mercury that is found in the suspended particulate matter.
“High flow rates during the spring melt can stir up bottom sediments and transport the associated mercury to the coastal zones of Lake Michigan,” said Babiarz. “Most fish live in these relatively warmer and shallower waters, and most of the annual mercury loading occurs during the spawning season.”
A demonstration dredging project on the Fox River, reduced industrial uses and lower emission standards have been implemented since the original mass balance study was conducted. Those reductions could be reflected in today’s mercury concentrations in the tributaries.
“This project will provide an interim benchmark before caps on mercury are completely met,” said Babiarz.
Reductions are being phased in over time, and additional cleanup projects have begun on all four of Wisconsin’s tributaries through the Great Lakes Restoration Initiative.
Reduction of mercury is a worldwide goal for improving public health.