Analysis of Legacy and Novel Neutral Per- and Polyfluoroalkyl Substances in Soils from an Industrial Manufacturing Facility

Abstract

Per- and polyfluoroalkyl substances (PFASs) have been detected in an array of environmental media due to their ubiquitous use in industrial and consumer products as well as potential release from fluorochemical manufacturing facilities. During their manufacture, many fluorotelomer (FT) facilities rely on neutral intermediates in polymer production including the FT-alcohols (FTOHs). These PFAS are known to transform to the terminal acids (perfluoro carboxylic acids; PFCAs) at rates that vary with environmental conditions. In the current study on soils from a FT facility, we employed gas chromatography coupled with conventional- and high-resolution mass spectrometry (GC-MS and GC-HRMS) to investigate the profile of these precursor compounds, the intermediary secondary alcohols (sFTOHs), FT-acrylates (FTAcr), and FT-acetates (FTAce) in soils around the former FT-production facility. Of these precursors, the general trend in detection intensity was [FTOHs] > [sFTOHs] > [FTAcrs], while for the FTOHs, homologue intensities generally were [12:2 FTOH] > [14:2 FTOH] > [16:2 FTOH] > [10:2 FTOH] > [18:2 FTOH] > [20:2 FTOH] > [8:2 FTOH] ∼ [6:2 FTOH]. The corresponding terminal acids were also detected in all soil samples and positively correlated with the precursor concentrations. GC-HRMS confirmed the presence of industrial manufacturing byproducts such as FT-ethers and FT-esters and aided in the tentative identification of previously unreported dimers and other compounds. The application of GC-HRMS to the measurement and identification of precursor PFAS is in its infancy, but the methodologies described here will help refine its use in tentatively identifying these compounds in the environment.

Keywords: PFCA precursors; Semivolatile PFAS; contaminated soils; fluorotelomer alcohols; neutral PFAS.

Figure 1.

Concentrations (ng/g) of FTOHs (semi)quantitated in soils, correcting for matrix-internal standard systematic bias (see Supporting Information for details), and sFTOHs (not corrected) plotted by presumed source at the manufacturing facility (A: top panel). Blue, orange, gray, and yellow bars represent sites A, B, C, and D, respectively. Perfluorocarboxylate concentrations in soils (B, bottom panel). C4–C20 represent the number of fully fluorinated carbons for the neutral (A) and ionic (B) PFAS determined in the current study. Data presented are the mean values of n = 2 samples from sites A–C and n = 4 samples from site D.

Figure 2.

Ratio of sFTOH to FTOH as a function of CF₂ count (A, top panel). Ratio of alpha- and beta-oxidation PFCA product to FTOH (B: bottom panel). Blue, orange, gray, and yellow dots represent sites A, B, C, and D, respectively. Decreasing ratios as functions of chain-lengths in both panels suggests a lesser degradation rate of longer-chain FTOHs.

Figure 3.

Reconstructed plot of retention time vs nominal mass for compounds and their fragments identified by KMD analysis in MPP. Solid symbols represent M + H ions while qualifier m/z fragments are open symbols. All nonidentified compounds are displayed in light gray, closed circles. Compounds reported herein for the first time are indicated by black circles.

Figure 4.

Correlations of the n:2 FTOHs with their terminal odd (PFCA(n – 1); blue dot) and even (PFCA(n); red triangle) PFCAs resulting from alpha and beta oxidation, respectively.