Emissions, Transport, and Fate of Emerging Per- and Polyfluoroalkyl Substances from One of the Major Fluoropolymer Manufacturing Facilities in China

Abstract

Fluoropolymer manufacturing is a major historical source of perfluorooctanoic acid (PFOA) on a global scale, but little is known about the emissions, transport, and fate of emerging per- and polyfluoroalkyl substances (PFASs). Here, we performed a comprehensive spatial trend and interyear comparison of surface water and sediment samples from the Xiaoqing River, which receives water discharge from one of the major fluoropolymer manufacturing facilities in China. A suspect screening identified 42 chemical formulas, including the tetramer acid of hexafluoropropylene oxide (HFPO-TeA) and numerous tentatively detected isomers of C9-C14 per- or polyfluoroalkyl ether carboxylic acids (PFECAs). As revealed by the spatial trends and peak area-based sediment-water distribution coefficients, emerging PFASs with 3-9 perfluorinated carbons were transported unimpededly with the bulk water flow having no measurable degradation. Emerging PFASs with >9 perfluorinated carbons displayed more rapidly decreasing spatial trends than shorter-chain homologues in surface water due to increasing sedimentation rates. The presence of HFPO oligomers, monoether PFECAs, monohydrogen-substituted perfluoroalkyl carboxylic acids (PFCAs) and monochlorine-substituted PFCAs could partly be explained by the active use of polymerization aids or the impurities therein. However, further research is encouraged to better characterize the emissions of low-molecular-weight PFASs from fluoropolymers throughout their life-cycle.

Analysis of hexafluoropropylene oxide-dimer acid (HFPO-DA) by liquid chromatography-mass spectrometry (LC-MS): Review of current approaches and environmental levels

“…The compounds also followed a similar spatial pattern to HFPO-DA, decreasing in concentration with distance from the manufacturing facility [54]. A similar approach was used by Song et al in which 42 emerging PFAS were tentatively identified in water near a fluorochemical plant in China [60]. Pan et al also used HRMS in a study targeting HFPO-DA and other PFAS, where the accurate mass measurement confirmed the presence of HFPO-TA, the trimer acid of HFPO, in water and biological samples [55].…”

“…In these cases, the additional MRM is used for analyte confirmation, as explicitly stated by Gebbink et al [54]. Generally, the recently introduced stable isotope labeled (SIL) standard for HFPO-DA ( 13 C 3 -HFPO-DA) was also included in the MRM schedule and used in isotope dilution quantification [6,8,54,57,60], or for recovery assessment in sample matrices [section 2.3]. Specific use of 13 C 3 -HFPO-DA in two studies from the same group was not stated, but the SIL was added prior to extraction and was likely used to correct for losses during extraction.…”

“…The establishment of limits-of-detection and quantification (LOD and LOQ) in several studies rely on signal-to-noise (S/N) values of 3 and 10 respectively, or an extrapolation thereof [8,14,[54][55][56][57][58]60]. Comparison of the instrument and method sensitivity values reported for other PFAS can be used to deduce HFPO-DA response in existing methods, described in Table 2.…”

“…The few biological matrices in which HFPO-DA levels have been assessed, carp blood, liver and muscle tissue [55], human serum [55,57] and human urine [57], and grass/leaves [8] incorporate pretreatment steps prior to extraction [55,57] such as alkaline digestion of fish and plant tissue [8,55]. Solid matrices such as grass/leaves and sediment were subjected to liquid extraction with methanol also prior to SPE [8,60]. Challenges existed in two studies with extraction blank contamination; in both cases the source of the contamination was determined to be the SPE cartridge [55,56].…”

“…However, the first study to report environmental detection of GenX/HFPO-DA, using typical LC methodology employed for legacy PFAS coupled with non-targeted MS acquisition, observed ionisation behaviour which yielded very little of the desired [M−H] − species [2,53]. Although the ionization conditions used presently require improvement, increasing interest in HFPO-DA has resulted in the incorporation of the compound in existing targeted PFAS analyses [3,8,14,[54][55][56][57][58][59][60], along with another PFECA, dodecafluoro-3H-4,8dioxanonanoate (ADONA) [55][56][57]60]. In late 2018, HFPO-DA was added to the United States Environmental Protection Agency (US EPA) Method 537.1 list of 18 PFAS to be determined in drinking water [61].…”