Scientists at UW-Madison are working to better understand how toxic “forever chemicals” move through the ground, which could help communities like Madison find and clean up the manufactured compounds before they contaminate drinking water.
Used for decades in firefighting foam, non-stick cookware and stain-resistant fabrics, these synthetic compounds, known collectively as PFAS, have been linked to health problems including low birth weight, cancer and liver disease.
Sprayed on the ground in firefighter training exercises, leaked from landfills and spread on farm fields in sewage sludge, PFAS, which do not break down naturally, have contaminated communities across the nation and Wisconsin, including Marinette, Wausau, La Crosse and Madison.
But in order to clean up a spill, you have to know where it is.
A new paper published in the journal Environmental Science & Technology presents a simplified framework for understanding how the chemicals are moving through the jumble of soil, sand, rock and water that lie between the surface and deep aquifers that supply drinking water.
People are also reading…
That’s especially difficult because air, water and particles are constantly moving through this “unsaturated zone,” said Will Gnesda, a UW-Madison graduate student in geoscience professor Christopher Zahasky’s lab and lead author of the study.
It’s a problem for any contaminant, but the unique properties that attract PFAS to the boundary between air and water make it all the more challenging.
“Chemistry dictates that part of it wants to be in water and part of it wants to be in air,” Gnesda said. “The unsaturated zone is full of those boundaries.”
The synthetic chemicals, which do not break down naturally, have been linked to health problems including low birth weight, cancer, and liver disease.
Christy Remucal, an associate professor of civil and environmental engineering at UW-Madison who specializes in PFAS but was not part of Gnesda’s study, said the research is a critical first step to being able to focus cleanup efforts.
“There’s lots of places where they might stick,” Remucal said. “There are over 6,000 different PFAS and they don’t all behave the same way. It’s really challenging, just because it’s so complex.”
Predicting the movement of PFAS has traditionally involved guesswork and a lot of computer models.
Gnesda and his colleagues developed a simplified framework to reduce the time and computing power needed to model the movement.
When applied to specific sites, that framework could help environmental regulators and contractors predict where PFAS are going — and figure out where they came from.
“Ultimately what we want to do is predict where PFAS plumes are moving and where should we target remediation,” Gnesda said.
The sites both drain into Starkweather Creek, which flows into Lake Monona, where health officials have warned anglers to limit consumption of fish.
The scientists were able to piggyback on the work of another researcher to apply their model at a site near Rhinelander, where PFAS have been found in two municipal wells between the airport and an area where biosolids had been spread on fields. They found several factors can influence the movement of PFAS, such as porosity of soil and rocks, the amount and type of organic carbon in those rocks.
Gnesda said the project was ultimately shut down because of “airport politics.” He said he would like to test the model at other contaminated sites such as the Dane County Regional Airport or the town of Campbell in La Crosse County but said it’s hard to convince local officials of the benefits.
“Nobody wants to know how much PFAS is in their area,” he said.
Gnesda and his colleagues are now working to validate their framework in the laboratory, where they have constructed columns filled with soil and water which they can use to track how PFAS molecules move through different configurations.
“We’re going to see how well our theory connects to the lab,” Gnesda said.
Environmental reporter Chris Hubbuch's favorite stories of 2022
It's hard to pick just five, but these are some of the most important -- and fun -- stories from 2022.
The DNR estimates Wisconsin has more than 420 lakes with the cool, dark waters where walleye thrive. By 2089, may be just four.
Madison and Dane County have reputations as environmentally-conscious communities, but neither government is rushing to clean up toxic pollutants.
With incentives for both businesses and consumers, it's hard to overstate the significance of this historic $369 billion federal investment in…
Who hasn't fantasized about leaving it all behind and hitting the road? This couple actually did it.
Most city trees that get cut down end up in the chipper, but a network of urban wood producers works to find better uses for this carbon-trapp…