Fluorotelomer Alcohol BiodegradationDirect Evidence that Perfluorinated Carbon Chains Breakdown

Abstract

There is increasing scientific interest to understand the environmental fate of fluorotelomer alcohols (FTOHs) and fluorotelomer-based products which may break down to FTOHs. Both are expected to enter aqueous waste streams, which would be processed in a wastewater treatment plant and therein subject to microbial biodegradation. We investigated the biodegradation of 3-14C, 1H,1H,2H,2H-perfluorodecanol [CF3(CF2)6(14)CF2CH2CH2OH, 14C-8-2 FTOH] in mixed bacterial culture and activated sludge. 14CO2 and 14C-organic volatiles in the headspace of the sealed bottles and bottles with continuous air flow were analyzed up to 4 months. After sample extraction with acetonitrile, 14C-labeled biotransformation products (metabolites) were quantified by LC/ARC (on-line liquid chromatography/ accurate radioisotope counting) and identified by quadrupole time-of-flight (Q-TOF) mass spectrometry and GC/MSD (mass selective detector). Three metabolites not yet reported in the literature have been identified as CF3(CF2)6(14)CHOHCH3 (7-2 sFTOH), CF3(CF2)6(14)CH=CHCOOH (7-3 unsaturated acid or 7-3 u acid), and CF3(CF2)6(14)CH=CHCONH2 (7-3 u amide) along with five previously reported metabolites [CF3(CF2)6(14)CF2CH2CHO (8-2 FTAL), CF3(CF2)6 (14)CF2CH2COOH (8-2 acid), CF3(CF2)6(14)CF=CHCOOH (8-2 u acid), CF3(CF2)6(14)CH2CH2COOH (7-3 acid), and CF3(CF2)6(14)COOH (PFOA)]. No CF3(CF2)6(14)CF2COOH (14C-PFNA) was observed, indicating that alpha-oxidation does not take place. It was found that strong adsorption to the activated sludge and subsequent transformation, even under continuous air flow, greatly reduced partitioning of 8-2 FTOH or any transformation products to air. CF3(CF2)4COOH (PFHA; perfluorohexanoic acid) was observed and increased in mixed bacterial culture over 28 days and accounted for about 1% of the initial 14C-8-2 FTOH concentration from day 28 to day 90. 14CO2 accounted for 1% of initial 14C in activated sludge with continuous air flow at day 1 and increased over time. In closed bottles, 14CO2 in the headspace of activated sludge medium increased to 12% of the available 14C over 135 days with periodic addition of ethanol, as compared to 3% when no additional ethanol was added. These results show that replenishment of organic carbon enhanced microbial mineralization of multiple--CF2--groups in the fluorocarbon chain of 14C-8-2 FTOH. At day 90 the net increase of fluoride ion in the mixed bacterial culture was 93 microg L(-1), equivalent to 12% of total mineralization (destruction) of the 14C-8-2 FTOH. These results demonstrate that perfluorinated carbon bonds of 14C-8-2 FTOH are defluorinated and mineralized by microorganisms under conditions which may occur in a wastewater treatment plant, forming shorter fluorinated carbon metabolites.

Methodology for studying biotransformation of polyfluoroalkyl precursors in the environment

“…Wang et al [3] calculated the mass flux of PFCAs in the global transport processes and suggested that historical direct emissions from manufacture and consumer usages were the major contributors of PFCAs detected in the environment. However, the indirect contributions via the biodegradation and biotransformation of polyfluoroalkyl precursors and atmospheric oxidation have also been confirmed by model prediction [9], laboratory experiments [10,11] and environmental monitoring [12]. Laboratory systems utilizing microbialconsortium and animal models to study polyfluoroalkyl-precursor biotransformation provided insight to understand the extent of contributions of such precursors to PFCAs and PFSAs detected in the environment and biota.…”

“…DB-WAX, DB-35 and analogous stationary phases were normally used to separate FTOHs and FOSEs [40,41,44,55], whereas DB-5 and DB-624 analytical columns were options for semi-volatile and highly-volatile PFAS precursors, respectively [10,11,37,54].…”

“…Nevertheless, radio-isotopic labeling provides a means of overcoming this by measuring positron emission from radioactive decaying chemicals. Due to low natural abundance and lasting half-life, 14 C was selected to label PFAS precursors in order to trace chemical transformations in environmental and biological trials [10,11,26,42].…”

Neutral poly- and perfluoroalkyl substances in air and seawater of the North Sea

“…Indirect sources of PFOA and PFOS are photo-and microbial degradation of neutral precursors such as perfluorosulfonamides (FOSA), perfluorosulfonamidoethanols (FOSE), and FTOHs (D' Eon et al 2006;Ellis et al 2004;Wang et al 2005a;Wang et al 2005b). Because of their slow reaction process with hydroxyl radicals, atmospheric lifetimes were estimated~10−20 days for FTOH and~20−50 days for perfluoroalkane sulphonamide (FASA) in smog chamber studies (Ellis et al 2004;Martin et al 2006) and atmospheric residence time of more than 50 days for FTOHs in field studies (Piekarz et al 2007), which suggest they are subject to regional and long-range atmospheric transport, e.g., the Arctic and Antarctic (Dreyer et al 2009b;Stock et al 2007;Jahnke et al 2007b).…”

Aerobic Soil Biotransformation of 6:2 Fluorotelomer Iodide

“…However, it is not known whether increased microbial populations are positively correlated to 6:2 FTI biotransformation potential in soil. Previous work 36 showed that number 3 carbon of [3- Mass Balance. The partitioning of 6:2 FTI into the headspace (gas phase) after initial dosing to the soil compartment occurred simultaneously with the aerobic biotransformation processes in the live incubation system (Figure 2).…”