Understanding how toxic PFAS chemicals spread from release sites

Date:
October 15, 2020
Source:
Brown University
Summary:
New lab studies are helping researchers to better understand how
so called 'forever chemicals' behave in soil and water, which can
help in understanding how these contaminants spread.



FULL STORY ==========================================================================
A study led by Brown University researchers sheds new light on how
pollutants found in firefighting foams are distributed in water and
surface soil at release sites. The findings could help researchers to
better predict how pollutants in these foams spread from the spill or
release sites -- fire training areas or airplane crash sites, for example
-- into drinking water supplies.


========================================================================== Firefighting foams, also known as aqueous film forming foams (AFFF),
are often used to combat fires involving highly flammable liquids like
jet fuel. The foams contain a wide range of per- and polyfluoroalkyl
substances (PFAS) including PFOA, PFOS and FOSA. Many of these compounds
have been linked to cancer, developmental problems and other conditions
in adults and children.

PFAS are sometimes referred to as "forever chemicals" because they are difficult to break down in the environment and can lead to long-term contamination of soil and water supplies.

"We're interested in what's referred to as the fate and transport of
these chemicals," said Kurt Pennell, a professor in Brown's School
of Engineering and co-author of the research. "When these foams get
into the soil, we want to be able to predict how long it's going to
take to reach a water body or a drinking water well, and how long the
water will need to be treated to remove the contaminants." It had been
shown previously that PFAS compounds tend to accumulate at interfaces
between water and other substances. Near the surface, for example, PFAS
tend to collect at the air-water interface -- the moist but unsaturated
soil at the top of an aquifer. However, prior experiments showing this interface activity were conducted only with individual PFAS compounds,
not with complex mixtures of compounds like firefighting foams.

"You can't assume that PFOS or PFOA alone are going to act the same way
as a mixture with other compounds," said Pennell, who is also a fellow
at the Institute at Brown for Environment and Society. "So this was
an effort to try to tease out the differences between the individual
compounds, and to see how they behave in these more complex mixtures
like firefighting foams." Using a series of laboratory experiments
described in the journal Environmental Science and Technology, Pennell
and his colleagues showed that the firefighting foam mixture does indeed
behave much differently than individual compounds. The research showed
that the foams had a far greater affinity for the air-water interface
than individual compounds. The foams had more than twice the interface
activity of PFOS alone, for example.

Pennell says that insights like these can help researchers to model how
PFAS compounds migrate from contaminated sites.

"We want to come up with the basic equations that describe the behavior
of these compounds in the lab, then incorporate those equations into
models that can be applied in field," Pennell said. "This work is the
beginning of that process, and we'll scale it up from here." Ultimately,
the hope is that a better understanding of the fate and transport of
these compounds could help to identify wells and waterways at risk for contamination, and aid in cleaning those sites up.


========================================================================== Story Source: Materials provided by Brown_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. jed costanza, Linda M. Abriola, Kurt D Pennell. Aqueous film-forming
foams exhibit greater interfacial activity than PFOA, PFOS, or FOSA.

Environmental Science & Technology, 2020; DOI:
10.1021/acs.est.0c03117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201015111740.htm

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