Farmers who work the fields of America’s breadbasket and beyond cannot see the harmful chemicals that taint the soil they till. But the chemicals, which have been linked to liver disease and certain types of cancer, are ever-present, seeping into the soil from the fertilizer they spread on their crops.
Rich in nutrients, that fertilizer is made from treated sewage sludge that a growing body of research shows contains heavy concentrations of per- and polyfluoroalkyl substances, or PFAS. Colloquially called “forever chemicals,” they linger in the environment for years and are ubiquitous, showing up in our water, soil, and food, and used in products from cookware and carpet to dental floss and firefighting foam.
Even dumpsites can’t contain PFAS, as the chemicals have been found in gases released by some landfills in Florida, one study discovered.
Now, a group of researchers is literally putting the ‘heat’ on forever chemicals. They are devising a new type of high-temperature technique that would not only destroy PFAS in soil, but prevent the chemicals from being released into the air.
“And that’s the challenge that’s really daunting,” said , dean of the College of Engineering and one of four University of Miami investigators involved in a multi-institutional study to assess the effectiveness of a novel thermal treatment method for PFAS-contaminated soil.
“As the name implies, ‘forever chemicals’ are extremely difficult to destroy,” Biswas said. “Incinerating PFAS-tainted soil is one option, but there’s the risk of the chemicals becoming aerosolized. And having them released into the air is just as harmful as their presence in soil. So, with our expertise in combustion and aerosol formation, we’re working on a new technique to overcome that challenge.”
Using soil samples provided by the University of Florida, the lead institution on the study, College of Engineering scientists are studying different thermal destruction pathways in hopes of breaking the carbon and fluorine bond that makes forever chemicals so strong.
Employing the protection of special laboratory hoods, researchers have conducted a series of high-temperature combustion experiments on contaminated soil, “but it’s still too early to say how effective our technique is,” said , chair of the Department of Chemical, Environmental, and Materials Engineering, who is the lead investigator of the University’s component of the study. “The samples are being analyzed by our colleagues at UF, and the results will be used to fine tune the next phase of our experiments.”
Wu said the U’s portion of the study is “the first to examine the desorption and decomposition kinetics in a combustion system, thus establishing a base for designing a practical incineration system for handling contaminated soil.”
The study has far-reaching implications, according to , an assistant professor of chemical, environmental, and materials engineering. “If we can find the most effective way to destroy PFAS in soil, then we can reduce the impact on our drinking water,” he said, noting that forever chemicals tend to seep into groundwater.
“That’s what makes this study unique—the incredible expertise that’s been combined from the universities that are involved,” said , an environmental engineering researcher at the University of Miami, who is also a part of the study. “Working with gas and aerosols is not easy, and it’s probably the hardest component to deal with. It’s easier to quantify what’s in soil, and it’s easier to quantify what’s in water. But to be able to capture what’s being lost to the air is really challenging, especially under very high temperatures. We have the expertise here to accomplish that.”
The analysis of PFAS-contaminated soil being conducted by UF researchers is vital to the study. “We have been working on PFAS for several years, assessing the current state of the technology, exploring regulatory hurdles, developing testing methodologies, designing experiments, and collecting soil samples at sites with PFAS,” said Timothy Townsend, the Jones Edmunds and Associates, Inc. professor in the Department of Environmental Engineering Sciences at UF. “We do all the PFAS analysis in our labs, and these are very elaborate testing methods that include both solid, liquid, and gaseous samples.”
Meanwhile, researchers at Florida Atlantic University are conducting what Wang describes as “total organic fluorine analysis” of PFAS. With the three institutions collaborating on the project, success could only be a matter of time, Wang said.
For Yiming Xi, one of four College of Engineering Ph.D. students working on the study, “the research is a great opportunity to learn how to solve real-world problems,” he said. “And it will help with my own research in the theoretical analysis of PFAS decomposition reactions in different temperature ranges.”
For Ph.D. student Chanakya Bagya Ramesh, the study represents the kind of work that inspired him to pursue an advanced degree. “The goal of my research is to understand how particles form in certain combustion systems, with the hopes of making these systems more sustainable by minimizing pollutant emissions,” he said. “However, since joining this project, I’ve realized that my research may also have applications in systems designed not only to prevent pollution but to destroy existing contaminants.”
First-year doctoral student Candido Hernandez is particularly concerned about the presence of forever chemicals in the firefighting foam called aqueous film forming foams and the risk of those chemicals making their way into the water supply. “The entire Floridian peninsula is basically a giant aquifer,” he said. “We all use this water and drink from it, so I hope this work leads the way in effectively removing these contaminants from our environment, not just here but across the country.”
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