Occurrence of per- and polyfluoroalkyl substances in sampled source water of public drinking-water supplies in the surficial aquifer in Delaware, 2018

Thirty water-supply drinking-water wells were sampled during fall 2018 for a set of constituents including PFAS. Groundwater samples were sent to Maxxam Laboratories (RTI Laboratory contract) to be analyzed for eighteen PFAS using USEPA 537m method. Groundwater age data were collected and analyzed as well in the USGS Reston, Va. laboratory. Quality-control samples including equipment and field blanks, sequential replicate samples, and laboratory spikes, were collected to evaluate and estimate potential contamination bias and measure variability from water-quality data-collection processes. No PFAS were detected in equipment or field blanks indicating that selected equipment, cleaning, sampling, and handling procedures are sufficient to provide data that reflect environmental conditions. More than half (16) of the sampled wells have one or more PFAS detections with up to eight detections per wells. Eight PFAS were detected in the study well network. PFAS individual compound concentrations detected ranged from E5.0 to 130 ppt. The four most frequently detected PFAS were PFOA (Perfluorooctanoic acid) with 47 percent detection, PFHxA (Perfluorohexanoic acid) with 33 percent detection, and PFOS (Perfluorooctane sulfonate) and PFHxS (Perfluorohexane sulfonate) with 27 percent detection each. Two wells exceeded the USEPAs Lifetime-Drinking Water Health-Advisory Level of 70 ppt for combined concentrations of PFOA and PFOS.