Determining global background soil PFAS loads and the fluorotelomer-based polymer degradation rates that can account for these loads.

In recent years, fluorotelomer-based polymers (FTPs) have been the dominant product of the fluorotelomer industry. For the last decade, whether FTPs degrade to toxic perfluorocarboxylates (PFCAs) has been vigorously contested, with early studies arguing that FTPs have half-lives >1000 years, and others concluding decadal half-lives. Given this FTP half-life discrepancy of 10- to >100-fold, here we investigate whether environmental loads of long-chain PFCAs might offer an independent approach to assess FTP half-lives. Specifically we: i) use surface soil-PFCA data to estimate terrestrial surface-soil background PFCA concentrations and loads; ii) extrapolate these data to generate global PFCA load estimates; iii) compare these estimates to published ocean-derived and industrial-emissions load estimates, finding agreement for perfluorooctanoate (C8), but an excess in longer-chain (C10,C12) PFCAs for ocean- and soil-derived loads relative to emissions; iv) model FTP degradation rates required to reconcile this discrepancy; and iv) compare our modeled estimates to existing experimental results. These findings show agreement for FTP half-lives at the decades-scale supporting existing laboratory studies that report decade-scale half-lives for FTPs. This suggests that global long-chain PFCA loads will increase for decades if legacy FTPs already manufactured are not contained upon disposal. These results suggest that FTPs comprised of novel poly- and perfluorinated alkyl substances (PFASs) now in production might constitute considerable sources to the environment of the new generation of PFASs.

A North American and global survey of perfluoroalkyl substances in surface soils: Distribution patterns and mode of occurrence.

The distribution of 32 per/polyfluoroalkyl substances (PFASs) in surface soils was determined at 62 locations representing all continents (North America n = 33, Europe n = 10, Asia n = 6, Africa n = 5, Australia n = 4, South America n = 3 and Antarctica n = 1) using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) systems. Quantifiable levels of perfluoroalkyl carboxylates (PFCAs: PFHxA-PFTeDA) were observed in all samples with total concentrations ranging from 29 to 14,300 pg/g (dry weight), while perfluoroalkane sulfonates (PFSAs: PFHxS, PFOS and PFDS) were detected in all samples but one, ranging from

Matrix normalized MALDI-TOF quantification of a fluorotelomer-based acrylate polymer.

The degradation of fluorotelomer-based acrylate polymers (FTACPs) has been hypothesized to serve as a source of the environmental contaminants, perfluoroalkyl carboxylates (PFCAs). Studies have relied on indirect measurement of presumed degradation products to evaluate the environmental fate of FTACPs; however, this approach leaves a degree of uncertainty. The present study describes the development of a quantitative matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry method as the first direct analysis method for FTACPs. The model FTACP used in this study was poly(8:2 FTAC-co-HDA), a copolymer of 8:2 fluorotelomer acrylate (8:2 FTAC) and hexadecyl acrylate (HDA). Instead of relying on an internal standard polymer, the intensities of 40 poly(8:2 FTAC-co-HDA) signals (911-4612 Da) were normalized to the signal intensity of a matrix-sodium cluster (659 Da). We termed this value the normalized polymer response (P(N)). By using the same dithranol solution for the sample preparation of poly(8:2 FTAC-co-HDA) standards, calibration curves with coefficient of determinations (R(2)) typically >0.98 were produced. When poly(8:2 FTAC-co-HDA) samples were prepared with the same dithranol solution as the poly(8:2 FTAC-co-HDA) standards, quantification to within 25% of the theoretical concentration was achieved. This approach minimized the sample-to-sample variability that typically plagues MALDI-TOF, and is the first method developed to directly quantify FTACPs.

Decades-scale degradation of commercial, side-chain, fluorotelomer-based polymers in soils and water.

Fluorotelomer-based polymers (FTPs) are the primary product of the fluorotelomer industry. Here we report on a 376-day study of the degradability of two commercial acrylate-linked FTPs in four saturated soils and in water. Using an exhaustive serial extraction, we report GC/MS and LC/MS/MS results for 50 species including fluorotelomer alcohols and acids, and perfluorocarboxylates. Modeling of seven sampling rounds, each consisting of ≥5 replicate microcosm treatments, for one commercial FTP in one soil yielded half-life estimates of 65­112 years and, when the other commercial FTP and soils were evaluated, the estimated half-lives ranged from 33 to 112 years. Experimental controls, consisting of commercial FTP in water, degraded roughly at the same rate as in soil. A follow-up experiment, with commercial FTP in pH 10 water, degraded roughly 10-fold faster than the circum-neutral control suggesting that commercial FTPs can undergo OH­-mediated hydrolysis. 8:2Fluorotelomer alcohol generated from FTP degradation in soil was more stable than without FTP present suggesting a clathrate guest­host association with the FTP. To our knowledge, these are the only degradability-test results for commercial FTPs that have been generated using exhaustive extraction procedures. They unambiguously show that commercial FTPs, the primary product of the fluorotelomer industry, are a source of fluorotelomer and perfluorinated compounds to the environment.

Investigating the biodegradability of a fluorotelomer-based acrylate polymer in a soil-plant microcosm by indirect and direct analysis.

Fluorotelomer-based acrylate polymers (FTACPs) are a class of side-chain fluorinated polymers used for a variety of commercial applications. The degradation of FTACPs through ester hydrolysis, cleavage of the polymer backbone, or both could serve as a significant source of perfluoroalkyl carboxylates (PFCAs). The biodegradation of FTACPs was evaluated in a soil-plant microcosm over 5.5 months in the absence/presence of wastewater treatment plant (WWTP) biosolids using a unique FTACP determined to be a homopolymer of 8:2 fluorotelomer acrylate (8:2 FTAC). Although structurally different from commercial FTACPs, the unique FTACP possesses 8:2 fluorotelomer side chain appendages bound to the polymer backbone via ester moieties. Liberation and subsequent biodegradation of the 8:2 fluorotelomer appendages was indirectly determined by monitoring for PFCAs of varying chain lengths (C6-C9) and known fluorotelomer intermediates by liquid chromatography tandem mass spectrometry (LC-MS/MS). A FTACP biodegradation half-life range of 8-111 years was inferred from the 8:2 fluorotelomer alcohol (8:2 FTOH) equivalent of the unique FTACP and the increase of degradation products. The progress of FTACP biodegradation was also directly monitored qualitatively using matrix-assisted laser desorption/ionization (MALDI-TOF) time-of-flight mass spectrometry. The combination of indirect and direct analysis indicated that the model FTACP biodegraded predominantly to perfluorooctanoate (PFOA) in soils and at a significantly higher rate in the presence of a plant and WWTP biosolids.

Influence of fluorination on the characterization of fluorotelomer-based acrylate polymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The relative degree of fluorotelomer-based acrylate polymers (FTACPs) fluorination was demonstrated to influence the sample preparation protocol for matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry. A homologous series of FTACPs were synthesized from fluorotelomer and hydrocarbon acrylates of different chain lengths, which varied the ratio of perfluorinated to hydrogenated carbons (RF/RH). The solubility of FTACPs in tetrahydrofuran (THF) and chloroform was observed to decrease for highly fluorinated FTACPs (RF/RH>0.5) promoting FTACP aggregation. No dependence on the degree of fluorination was observed for the solubility of FTACPs in the fluorinated solvents α,α,α-trifluorotoluene (TFT) or dichloropentafluoropropanes (HCFC-225). For FTACPs with a low degree of fluorination such as poly(8:2 FTAC-co-HDA) (RF/RH=0.375), MALDI-ToF analysis was successful using a conventional sample preparation protocol with THF, and dithranol (Dith) matrix. Conversely, the poor solubility of the highly fluorinated poly(8:2 FTAC-co-BA) (RF/RH=1.5) in THF resulted in mass discrimination. Several fluorinated sample preparation protocols were evaluated for poly(8:2 FTAC-co-BA) using TFT and HCFC-225, and decafluoroazobenzene (DFAB) or 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) matrices. The high volatility of HCFC-225 decreased FTACP pooling during solvent evaporation in comparison to the less volatile TFT, and improved the quantity of detectable signals. MALDI-ToF analysis of poly(8:2 FTAC-co-BA) in a 95:5 HCFC-225:methanol with DCTB being the best sample preparation protocol for highly fluorinated FTACPs in this study producing the highest number of observable signals. Employing a fluorinated sample preparation offers the capability of analyzing other highly fluorinated polymers that are not compatible with conventional sample preparations.

C8-heteroaryl-2'-deoxyguanosine adducts as conformational fluorescent probes in the NarI recognition sequence.

The optical, redox, and electronic properties of C(8)-heteroaryl-2'-deoxyguanosine (dG) adducts with C(8)-substituents consisting of furyl ((Fur)dG), pyrrolyl ((Pyr)dG), thienyl ((Th)dG), benzofuryl ((Bfur)dG), indolyl ((Ind)dG), and benzothienyl ((Bth)dG) are described. These adducts behave as fluorescent nucleobase probes with emission maxima from 379 to 419 nm and fluorescence quantum yields (Φ(fl)) in the 0.1-0.8 range in water at neutral pH. The probes exhibit quenched fluorescence with increased solvent viscosity and decreased solvent polarity. The (Fur)dG, (Bfur)dG, (Ind)dG, and (Bth)dG derivatives were incorporated into the G(3) position of the 12-mer oligonucleotide 5'-CTCG(1)G(2)CG(3)CCATC-3' that contains the recognition sequence of the NarI Type II restriction endonuclease. This sequence is widely used to study the biological activity (mutagenicity) of C(8)-arylamine-dG adducts with adduct conformation (anti vs syn) playing a critical role in the biological outcome. The modified NarI(X = (Fur)G, (Ind)G, (Bfur)G, or (Bth)G) oligonucleotides were hybridized to the complementary strand containing either C (NarI'(C)) or G (NarI'(G)) opposite the probe. The duplex structures were characterized by UV melting temperature analysis, fluorescence spectroscopy, collisional fluorescence quenching studies, and circular dichroism (CD). The emission of the probes showed sensitivity to the opposing base in the duplex, and suggested the utility of fluorescence spectroscopy to monitor probe conformation.