Grab a cup and scoop up water from Lake Michigan or one of the rivers that feed it. Then hold the water sample up and you’ll see tiny bits of floating particles, including bits of clay, algae and other organic matter that make the water appear cloudy.
These microscopic particles may hold important clues to understanding how a large family of human-made chemicals – called PFAS, or “forever chemicals” – move through one of the region’s most valuable natural resources, said Yin Wang, associate professor, civil & environmental engineering.
The research team of Wang; Shangping Xu, associate professor, geosciences; and Patrick Gorski, a scientist with the Wisconsin Department of Natural Resources; will look at the question in a new study funded with a $259,500 grant from Wisconsin Sea Grant.
Scientists have spent years studying per- and polyfluoroalkyl substances, or PFAS, which persist in the environment and are linked to adverse human health effects. They know the compounds can cling to soil, Wang said, but what isn’t known is whether PFAS chemicals also hitchhike on the countless suspended particles in lakes and rivers.
Attached vs. dissolved
“If PFAS are attached to these particles, they may behave very differently than if they are simply dissolved in the water,” Wang said. Understanding those differences could help researchers identify how PFAS enter the lake and where they are most likely to accumulate.
With water samples collected from the lake and several of its largest tributaries, Wang and Xu will separate the suspended particles and the water and measure the amount of PFAS in each. The results should reveal how much of the contamination is traveling with particles and how much remains dissolved.
The team believes that many PFAS compounds do attach to suspended particles, but not all in the same way, Xu said. The researchers also hypothesize that the chemical structure of different PFAS compounds influences if or how tightly they stick to floating solids.
What rivers can reveal
Comparing samples from Lake Michigan with those taken in tributaries may offer additional insights. Rivers often carry more suspended particles than the open lake, where the much larger volume of water dilutes them. Wind, waves and weather can influence where the particles go, and fish and other aquatic organisms may encounter particle-bound PFAS differently than the dissolved chemicals.
Looking at both data sets, “may allow us to determine how tributary-derived PFAS are redistributed and modified within the lake,” said Xu, whose research focuses on emerging contaminants in the environment, and the development of novel removal technologies.
Today’s environmental models often overlook the distinctions because the necessary data doesn’t exist, Wang added. He hopes this research will fill the gap, providing new information that could improve cleanup strategies.
Wang and Xu previously worked together on a Sea Grant project that investigated how PFAS compounds accumulate and move in groundwater. The pair also hold a patent on a next-generation filtration material specifically designed to target low concentrations of PFAS.