UNCW researchers: GenX builds up in river sediment, may release later into drinking water

Researchers have been conducting four main GenX studies since November 2017 using $250,000 in emergency state money.

New man-made chemicals discovered in Wilmington’s drinking water

Researchers have discovered new compounds besides GenX in Wilmington’s drinking water using an analysis called liquid chromatography and high-resolution mass spectrometry.

This includes a compound called PFMOAA, which WECT reported in December 2017.

“We have identified several new PFAS in both raw and finished drinking waters that have not been reported in the scientific literature,” according to the report.

Per- and polyfluoroalkyl substances (PFAS) is a large category of man-made chemicals that includes GenX.

The exact structure and name of these new compounds is still being worked out because the scientists need pure samples for comparison.

For the last five months, a team of seven researchers has collected and analyzed treated and untreated drinking water from CFPUA’s Sweeney Water Treatment Facility in New Hanover County.

GenX builds up in river sediment, may later release back into the water

Researchers have discovered the highest concentrations of GenX in Cape Fear River sediment at Lock and Dam 2 in Bladen County, at 21.6 nanograms per grams of dry sediment.

“We find [GenX] in all the sediments. No one knew that before,” said Bob Kieber, Ph.D.

The second-highest GenX concentration was found at a point near the Port of Wilmington at 14.1 nanograms per grams of dry sediment.

“Sediments do move. If you look at the river at a rainstorm you do see sediments moving down the river,” said G. Brooks Avery, Ph.D. “At this point, it would be really risky to interpret into the spatial variability into these sediments and their concentrations.”

Researchers also incidentally discovered seven new PFAS compounds built up in the river sediment, but they don’t know yet the specific identity of these man-made chemicals.

“Two of them… We don’t know what they are yet,” said Ralph Mead, Ph.D. “I’m not saying they’re PFAS just yet. We don’t know that.”

“An initial conclusion from this study is that sediments are acting as a repository of GenX that may be released into the overlying water column, potentially impacting sensitive estuarine ecosystems as well as drinking water utilities, even if it is no longer being released into the environment,” according to the report.

The researchers hypothesize that GenX in river sediment likely comes from dumping into the river itself and atmospheric deposition – GenX traveling through the air.

Since November, researchers have collected sediment samples from several points along the Cape Fear River, upstream and downstream from the Chemours Fayetteville Works plant, targeted for its release of GenX into the environment.

Scientists first had to develop a method for how to extract GenX from the river sediment, because there has not been any research like this before.

Their decided method involves oven-baking the river sediment, breaking into smaller pieces, shaking with a liquid, and measuring with mass spectrometry.

Starting in May 2018, UNCW researchers will place samples of GenX-tainted river sediment in dark storage for several months to see how GenX breaks down over time.

“We’re highlighting now that it’s in the sediment, it’s in the rain,” said Kieber. “The question is — once it gets in the sediments, what does it do? Does it degrade? Does it just sit there and accumulate with time. Or does it degrade into something potentially more dangerous?”

River sediment collection and analysis will continue until June 2019.

GenX in raindrops on UNCW’s campus

Scientists revealed last month that GenX was discovered in rainwater on UNCW’s campus, although at concentrations far below the state’s health goal.

“I think the levels are low, and it’s diluted a lot, but I think it’s the accumulation over time. And what else it goes into. It rains on every field. Every plant is exposed to it,” said Pam Seaton, Ph.D., who helped spearhead this finding. “But again, really low concentrations.”

In this report, researchers explain that GenX does not likely travel directly from the water to airborne forms. Rather, a chemical precursor to GenX (hexafluoropropylene dimer acid fluoride) is likely emitted into the atmosphere, and then in less than 10 minutes reacts with water to form GenX, which later falls back down to earth as rain.

“The precursor to GenX at Chemours is what’s called an acid fluoride. And when it touches water it turns into GenX. So what they emit through the stacks at Chemours is the acid fluoride. As soon as it hits any water in the atmosphere it turns into GenX. So that’s why we have GenX in rainwater,” explained Seaton.

Oysters and GenX

Only a small oyster study has been conducted so far, but more extensive oyster research is ongoing and will be completed later this year.

“An initial study of the effects of exposure to GenX on the growth, survival, and filtration rates of juvenile oysters suggests that very high concentrations may decrease filtration and increase mortality rates, yet there was little bioaccumulation of GenX in oyster tissues,” the report reads.

GenX concentrations of 100 ppb killed one in four oysters grown in this water, indicating these levels are “stressful to juvenile oysters under the experimental conditions,” according to the report.

However, this experimental level is about 100 times higher than GenX levels discovered so far in our environment.

GenX did not build up inside the oysters to a high degree, despite the high exposure levels.

“These juvenile oysters didn’t come from the wild,” Andrea Bourdelais, Ph.D., who measures GenX concentration in oyster tissue. “So we don’t exactly know if oysters in the field will take up GenX at the same rate.”

Researchers hypothesize the glass chamber might have held onto the GenX or that the compound’s polar structure impedes bioaccumulation.

“We are currently in the process of conducting further experiments involving adult oysters using environmentally realistic concentrations of GenX using non-glass exposure chambers,” researchers write.

“I don’t think we should have businesses releasing effluent in the rivers that we are then taking for our drinking water,” said Bourdelais. “A lot of communities actually have reservoirs that are pristine. They don’t allow boating, they don’t allow anything. They’re just for drinking water, and we might need to look into that.”

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