pubs.acs.org
Per- and Polyfluoroalkyl Substances and Total Organic Fluorine Ratios from Field-Collected Light Nonaqueous Phase Liquids and Groundwater
Per- and polyfluoroalkyl substances (PFAS) and light nonaqueous phase liquid (LNAPL) co-occur in the subsurface at military installations. Concentrations of PFAS in 13 paired LNAPL and groundwater samples collected from groundwater wells were used to compute LNAPL:groundwater ratios (γLNAPL-GW). Individual target PFAS were determined by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF) while total organic fluorine and fluoride were determined by 19F nuclear magnetic resonance spectroscopy (NMR). The percent aromatic content of LNAPL was determined using 13C NMR. The PFAS concentrations in LNAPL ranged from 80 ng/L to >5,000,000 ng/L. The summed molar concentration of individual PFAS accounted for up to 26.7% of total organic fluorine. Individual PFAS γLNAPL-GW values ranged from <1 to 557, while γLNAPL-GW for total organic fluorine ranged from 0.003 to 18.3. For a given LNAPL-groundwater sample pair, there was a headgroup and fluorinated chain length effect on γLNAPL-GW. Visualization of γLNAPL-GW across samples indicated that both PFAS structure and LNAPL and groundwater characteristics strongly influenced partitioning. Linear mixed-effects modeling indicated that environmental parameters accounted for 36.5% of the variance in γLNAPL-GW, increasing to 72.0% when PFAS class and chain length were included. Strong multicollinearity among variables limits the ability to identify singular dominant factors; thus, controlled laboratory studies are needed.
