Understanding PFAS in Delaware Water

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Poly- and perfluorinated alkyl substances (PFAS) can be found in drinking water across the United States. PFAS are particularly prevalent in the East Coast, where the population is denser.

In Delaware specifically, there have been limited studies done on the presence of PFAS in drinking water – and Mi-Ling Li, assistant professor of environmental chemistry and toxicology at the University of Delaware, is trying to change that.

“With the really scarce data measured in Delaware, we got all of these really high numbers with drinking water sources in military bases and drinking water sources,” she said speaking at the Eastern Analytical Symposium in Princeton, NJ on November 13. “We know it’s there, but we have limited data and research on that.”

Very few locations in Delaware have been tested for PFAS, Li said. But it’s still a major concern in the state because of the high concentrations of manufacturing and superfund sites, airports, and military bases.

Li and her research group tested water in the St. Jones component of the Delaware National Estuarine Research Reserve (DNREC) to better understand PFAS in the area. The team sampled in the fall and spring, to see when levels of PFAS were higher. The team took samples of tidal channel surface water, groundwater, porewater, and soil samples. They tested water during both high and low tide to determine if there was a difference in the levels at those times.


“We chose these sites because they are different hydrological zones,” she said. The team used a ultrahigh-pressure liquid chromatography and tandem mass spectrometry (UHPLC–MS/MS) system to analyze the samples. The methods they used were a modified version of EPA Method 533 to test the water samples and EPA Draft Method 1633 for Sediment PFAS extraction.

Li’s team found there was a consistent distribution of PFAS during the fall and spring, and tidal influence did not play a crucial role in the level of PFAS in surface water. However, the team did see a higher concentration of next generation substances in the water during the spring compared with the fall.

“We don’t really know any specific reason for that yet,” she said.

There’s more work to be done in these locations, Li said, and her team is planning to continue their analysis in Delaware to better understand the concentration of PFAS locally and how it impacts drinking water in the state.