A continually increasing global crisis triggered by synthetic chemicals known as PFAS or polyfluoroalkyl substances in subsoil water has amassed much attention in the past years.
The announced levels could be ‘just the tip of the iceberg’ because the majority of chemicals are still moving down at a slow pace through the soil, as per Bo Guo, professor assistant of hydrology and atmospheric sciences at the University of Arizona.
The Damaging Toll of Chemicals
The PFAS group hosts almost 3,000 artificial chemicals. They have been incorporated into the soil since the 1940s from food packaging, water-resistant materials, non-stick items, pizza boxes, paints, and more, the Environmental Protection Agency stated.
The chemicals do not decompose in the environment, nor in the body, and an increasing number of researches have depicted the fact that PFAS pollution in water sources is universal in the United States and that exposure is dangerous to health.
“Because PFAS are in a lot of consumer and industrial products, they can get into wastewater. Treatment plants are not designed to treat these compounds, so these chemicals just stay in that water to get reused. It’s sprayed on soccer fields or used to recharge aquifers, for example,” said Mark Brusseau, professor of environmental science. “PFAS can also get into the biosolids, which are land-applied as fertilizer, so there are all these sources, which means they could have entered the environment at many different time periods and repeatedly.”
To learn the way chemicals travel through the soil between the land surface and groundwater, a zone known as ‘vadose,’ researchers from the University of Arizona created a new mathematical model to imitate the various intricate processes that impact the transport and retention of those chemicals.
The Mysterious Behavior Was Explained
The novel model showcased that most of PFAS chemicals gather in regions where the air touches the surface of water caught in the soil, which slows the elements’ down progress to groundwater in a big way. The team of scientists discovered the fact that the chemicals will travel at an even slower pace than expected through coarse-grain soils than fine-grain soils.
“This means that the majority of PFAS are still in the soil, and they are migrating down slowly in a way similar to a ticking time bomb,” said Guo, the study’s lead author.
Earlier studies showed that PFAS chemicals were traveling slowly through the soil before getting to the groundwater, but no one understood the reason. The model depicts the mechanisms behind the incredibly slow movement seen in the field.
“This has big implications for focusing remediation,” Guo said. “So far, groundwater has been the focus, but should we actually focus on soil, which is where most of the PFAS are and will be for a long time? Or do we wait and remediate the groundwater for decades or centuries?”
The model can function for any PFAS chemical, but the scientists simulated PFOS in particular, or perfluorooctanesulfonate, which is usually incorporated in firefighting foam and is one of the most concerning element among all the other chemicals.
“One of our objectives in the future would be to apply the model to different sites,” said, Brusseau, who co-authored the study with Guo and Jicai Zeng, a postdoctoral researcher in Guo’s group. “Then hopefully it will be useful for policymakers, regulators, environmental consultants to do assessments.”