ANALYSIS OF PFAS IN THE EDWARDS-TRINITY AQUIFER SYSTEM

Poly- and perfluoroalkyl substances (PFAS) are highly resistant to degradation and may accumulate to levels above the EPA advisory limit (70 ng/L). Drinking water may provide a primary and direct source of PFAS to humans, and it is imperative to quantify and monitor PFAS in water sources, especially easily contaminated sources such as aquifer systems. 34 water samples collected from 19 different locations in the Edwards-Trinity Aquifer System (Texas) have been analyzed for 25 PFAS (C₄-C₁₀) using liquid chromatography mass spectrometry (LC/MS). C₄-C₈ PFAS have been detected with a notable prevalence in short-chain perfluorocarboxylic acids (PFCAs). Long-chain PFAS are more hydrophobic compared to short-chain PFAS and preferentially bind to sediments and other particles, while the short-chain constituents stay mobile in water. Considering the distance of the sample locations from urban areas, the short-chain PFAS may partially be attributed to the degradation of more volatile PFAS (such as PTOHs and FASEs), while both short and long chain may also have originated from the transformation of PFAS precursors (including PTSAs and PAPs). Origins of analyzed PFAS will be pinpointed and inferred based on typical recreational usage, distance to industrial and urban areas, distance to waste water treatment plants, and other common sources.