University of Wisconsin-Madison environmental engineers are tracking the myriad ways in which “forever chemicals” get into Lake Superior.
Civil and environmental engineering PhD student Ali Milani and chemistry PhD student Kaitlyn Gruber are leading projects to monitor how per- and polyfluoroalkyl (PFAS) chemicals move through the atmosphere and through river and tributary systems. Milani’s project, in partnership with the National Atmospheric Deposition Program and the Wisconsin State Laboratory of Hygiene, focuses on precipitation. Gruber, collaborating with the U.S. Geological Survey (USGS), is researching PFAS movement through river systems.
In 2022, Gruber and partner researchers from the USGS collected samples from 28 tributaries emptying into the United States side of Lake Superior across three sampling campaigns. Those samples enabled the team to focus on separate aspects of PFAS contamination—the USGS study looks at the effect on fish and potential implications for human health, while Gruber’s has focused on how PFAS physically move through the water.
“What we want to know is are we primarily seeing PFAS in sediment at the bottom of a river, or are they more suspended in the water column?” Gruber says. “If a river is choppy and there’s a lot of stuff kicked up in the water, we’re looking to see if these chemicals might be transported on that particulate matter, or if they’re in the water itself.”
Milani collected precipitation samples for two years, beginning in summer 2022, at nine sites around Lake Superior—some shoreside, others farther away. The field work yielded a tremendous amount of data, and Milani is still analyzing it.
“Even in some of our preliminary analysis, we see trends in PFAS levels depending on what side of the lake you’re on, or the season,” Milani says. “I think a lot of long-term studies with big datasets like we’ve collected through this collaborative research are going to be helpful for evaluating trends not just at Lake Superior, but around the world—because there are similar river systems and atmospheric transportation happening everywhere.”
PFAS contamination is a global challenge. They’re a class of thousands of widely used chemicals found in everything from consumer products like popcorn bags and nonstick cookware to certain firefighting foams. Some PFAS chemicals break down very slowly, which means if they get into the natural environment, they remain there for years. They’re also mobile—meaning they spread through the ground, in water or via weather patterns far from contamination sources.
Milani and Gruber are looking for PFAS at the low parts-per-trillion level. Though that’s an astonishingly low concentration (comparable to one drop of water out of 20 Olympic swimming pools), it aligns with current federal regulations for PFAS in drinking water. And with enough time, Lake Superior—the largest freshwater lake in the world by surface area and third-largest by volume—could turn into a reservoir of PFAS contamination.
“Even though these are low concentrations of sometimes less than one part per trillion, they’ll still build up in Lake Superior for a very long time,” Milani says. “It could be more than 150 years of cumulative contamination—buildup that will also move down into the rest of the Great Lakes. The more we can do now to track and identify contamination sources, the better our chances for mitigating that long-term contamination.”
Gruber and Milani are in Civil and Environmental Engineering Professor Christy Remucal‘s research group. Remucal, an expert in PFAS research, leads UW-Madison’s PFAS Center of Excellence.
Featured image caption: PhD students Ali Milani and Kaitylyn Gruber work in the lab in the Water Sciences and Engineering Laboratory. Both students are working on projects to monitor how PFAS contaminants, carried by precipitation or in tributaries, get into Lake Superior.