From the nonstick Teflon pans that make cooking a breeze to the stain-resistant carpet that keeps our homes looking new, per- and polyfluoroalkyl substances (PFAS) have been heralded as miracle workers in our daily lives.
However, beneath the surface of their seemingly innocuous applications is a more complex story. Studies have found PFAS to be toxic, even at very low concentrations. There are direct correlations between PFAS exposure and adverse impacts to human health, causing increased risks of certain cancers, immune system problems, and reproductive issues.
Further, because of the molecular makeup of PFAS, they are not going anwhere any time soon. They are known as “forever chemicals” and sometimes “ubiquitous chemicals” because of their exceptional lasting power, and their uncanny prevalence all over the world.
“We call them forever chemicals because of their carbon- fluorine makeup. The carbon-fluorine bond is the one of the strongest bonds in nature. They are not broken down by natural systems, resulting in accumulation in the environment. You cannot break them down easily. So once they get into the environment, PFAS can stay stable for days and years and even decades,” said Dengjun Wang, Ph.D., a UF/IFAS assistant professor of agricultural and biological engineering.
Due to their ability to be transported both by air and by rainfall, PFAS have been found in the most remote corners of the globe, even in serum samples taken from polar bears — in regions that have never seen a non-stick pan or a tube of waterproof mascara.
“The carbon backbone of the PFAS molecule is hydrophobic, and the head group of the molecule is hydrophilic. This is why they can transport through the water and through the air and are so widespread in water and soil, air and almost everywhere,” Wang said.
Wang focused his doctoral research on the transport, transformation, and remediation of PFAS in the environment, specifically the impact of PFAS on water quality and agriculture.
He has a remarkably chipper, inspired and warm personality, especially given the seemingly daunting task of tackling an enduring, omnipresent toxic chemical. Talking to him gives one the feeling that maybe everything is going to be OK. His office is tidy and full of sunshine. There’s a photo of his two cute children next to a computer monitor displaying a closeup of a complex molecule.
“My research ties to PFAS and how they move in the environment, specifically soil and water — and how these chemicals get into plants in agricultural systems. PFAS compounds
can be found in water, fertilizers, pesticides, and biosolids. They are drawn up into the plants, and then can be transferred through the food chain,” Wang said.
Through his research, Wang hopes to mitigate adverse effects from these contaminants to our soil, water and plants, eventually to achieve sustainable agriculture.
The approach to mitigating PFAS in agriculture and water safety is manifold. The U.S. EPA has taken steps to prohibit the usage of any new PFAS chemicals— but the ones that have bioaccumulated still fester.
Perhaps the most profound impact to our health is the pollution of groundwater due to PFAS contamination. The most common pathway for PFAS to our groundwater is through infiltration from aqueous film-forming foam-, — a supremely efficient firefighting foam, and landfill leachate from garbage dumps, where liquid from PFAS containing products distill and seep into our water supplies.
“In the United States, 60% of the population relies on groundwater as their drinking water source. So, it’s a big problem right now.” Wang said.
So, how to address the PFAS that have already permeated the environment? Microbes cannot break down the chemicals, water, touted “the universal solvent” cannot transform them-
Wang fights poison with fire.
“We utilize agricultural wastes to produce biochar, which is a carbonaceous material with unique physicochemical properties for PFAS remediation,” he said. “We burn agricultural wastes, otherwise they will be dumped somewhere to cause harm to the environment. So, we recycle, collect, put them into the furnace, and burn them, to produce the biochar and utilize the biochar as a sorbent to capture PFAS and purify the drinking water. It’s kind of a circular economy— we get the dirty stuff, the agricultural wastes, and then produce the good bio char materials and then remove the dirty PFAS compounds from the water.”
In addition to being used in a filter application (sorbent), biochar can be used as an amendment to soil. In his current research, Wang develops superior biochars for PFAS remediation.
“If you have the ring of water containing PFAS, you can dig a trench and fill up with biochar,” he said. Wang describes using biochar in agricultural applications, “so that runoff water can pass through the biochar barrier in the trench, and then the biochar can capture the PFAS along with other contaminants. Then you have the clean water after moving through that barrier. So Iin that case, you can stop the path of the PFAS water from the runoff water to your plants and your crops.”
The PFAS captured by the biochar can then be destroyed. using ultrasonication or other advanced destruction technology. “The beauty of biochar is that it can be recycled and used for multiple cycles to further lower the treatment costs. One of the hurdles with PFAS mitigation is cost of technologies and educating farmers on alternative products and procedures,” Wang said. It’s an uphill battle, and the fight is for global human health. “We have to tackle the problem. It is not an easy problem, it is really challenging. We have to find a solution.” Wang said.
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