Soil and water

How Forever Chemicals interacts with soil at the molecular level

This image rendering shows several different types of PFAS molecules that Spartan researchers examined to learn how the compounds interact with soil components. Credit: Wilson Research Group

Michigan State University chemists are uncovering new information to help remedy “eternal chemicals” by showing for the first time how they interact with soil at the molecular level.

The researchers, Narasimhan Loganathan and Angela Wilsonpublished their findings in Environmental sciences and technologies.

“Eternal chemicals” – more formally known as PFAS or perfluoroalkyl and polyfluoroalkyl substances – earned the label because they don’t break down naturally. When PFAS pollute soil and water, they can enter the food system through plants, livestock, and drinking water.

A 2015 Centers for Disease Control and Prevention report estimated that PFAS is in the blood of 97% of Americans. Other more recent studies have brought this figure closer to 99%.

What makes PFAS so ubiquitous is a combination of persistence and utility. Over 9,000 chemicals qualify as PFAS and are found in a wide range of applications including food packaging, non-stick cookware, fire fighting foams and many more. While time and nature can degrade certain components of these products – and the waste generated during their production – PFAS persist and accumulate in the environment.

Removing PFAS from soil and water is therefore important to reduce exposure to these chemicals and the harm they can cause, including thyroid disease and increased risk of certain cancers.

“When you start looking at mitigation strategies, you see a lot about removing PFAS from water, but there’s very little PFAS in soil,” said Loganathan, senior research associate at MSU.

“And some of the studies are ‘molecule blind,'” Wilson said. “That is, they don’t pay attention to chemistry.”

Wilson and Loganathan decided to help change that by performing the first molecular-level simulations of interactions between PFAS and a soil component, kaolinite.

For the study, the duo focused on some of the most prevalent and problematic PFAS chemicals. They chose soil-side kaolinite because it is a common soil mineral, especially in Michigan.

PFAS are a concern everywhere, but they present a challenge unique to Michigan. Michigan has an abundance of PFAS, with over 200 known sites contaminated by PFAS. Moreover, agriculture and the Great Lakes are the basis of the state’s identity. Protecting Michigan’s lands and waters is a goal shared by many communities, legislators and businesses in the state.

“Even before this job, we were going to huge meetings and talking about PFAS with people from different municipalities, farms, sewage treatment plants and more,” Wilson said. “A lot of people are looking for solutions.”

The study was inspired by a Michigan engineering company that asked Wilson how PFAS could spread through soil and how best to remediate the chemicals. She didn’t have the answers, but she knew that Loganathan could help her start to find some.

She recruited him to join this project, supported by the National Science Foundation. The duo also had access to computing resources provided by the National Energy Research Scientific Computing Center and MSU’s Institute for Cyber-Enabled Research, or iCER.

The results of the simulations provided some reasons for optimism regarding sanitation. For example, some of the PFASs studied by the team had longer carbon chains serving as skeletons assembled on kaolinite.

“Ideally, that’s what you would want. You would want all the PFAS just sitting in a clump so you could grab it and filter it,” Wilson said. The flip side is that the shorter-chain PFAS were less likely to clump together, remaining more mobile in the soil. The take-home message is that not all PFAS behave the same. And not all soils behave the same with respect to PFAS. »

“Soil components play an important role,” Loganathan said. “The composition of the soil around any contaminated site is going to be critical in knowing how far PFAS penetrate underground, where they can then reach groundwater.”

While the idea of ​​examining the myriad combinations of PFAS and soil components is daunting, the Spartans have shown that their computational approach is well suited to tackle the diversity of problems inherent in PFAS pollution.

“The beauty of computational chemistry is that you can study so many different systems,” said Wilson, whose research team also examines PFAS interactions with proteins in the body. His team is also studying PFAS in different fish species with support from the Great Lakes Fisheries Trust and the Strategic Environmental Research and Development Program, which are respectively state and federal organizations that fund environmental projects.

The goal, in soil and biology projects, is to reveal interactions that could help protect more people from exposure to PFAS.

“Such information at the molecular level is going to be extremely important for any remediation strategy,” Loganathan said.

Republished with kind permission from Michigan State University.