Formation Of Perfluoroalkyl Acids Research Articles

Fate of Per- and Polyfluoroalkyl Substances from Durable Water-Repellent Clothing during Use.

To make outdoor clothing water- or dirt-repellent, durable water-repellent (DWR) coatings based on side-chain fluorinated polymers (SFPs) are used. During use of outdoor clothing, per- and polyfluoroalkyl substances (PFASs) can be emitted from the DWR to the environment. In this study, the effects of aging, washing, and tumble drying on the concentration of extractable PFASs in the DWR of perfluorohexane-based short-chain SFPs (FC-6 chemistry) and of perfluorooctane-based long-chain SFPs (FC-8 chemistry) were assessed. For this purpose, polyamide (PA) and polyester (PES) fabrics were coated with FC-6- and FC-8-based DWRs. Results show that aging of the coated fabrics causes an increase in concentration and formation of perfluoroalkyl acids (PFAAs). The effect of aging on the volatile PFASs depends on the type of fabric. Washing causes a decrease in PFAA concentrations, and in general, volatile PFASs are partly washed out of the textiles. However, washing can also increase the extractable concentration of volatile PFASs in the fabrics. This effect becomes stronger by a combination of aging and washing. Tumble drying does not affect the PFAS concentrations in textiles. In conclusion, aging and washing of fabrics coated with the DWR based on SFPs release PFASs to the environment.

Formation and fate of perfluoroalkyl acids (PFAAs) in a laboratory-scale urban wastewater system

The fate and formation of perfluoroalkyl acids (PFAAs) have been investigated during wastewater treatment processes but studies for the entire urban wastewater system comprising the sewage transport and wastewater and sludge treatment processes are scarce. This work performs an integrated assessment of the formation and fate of PFAAs in the urban wastewater system together with their behavior in separate components of the system. To achieve this, PFAAs were monitored over five weeks in a laboratory-scale urban wastewater system comprising sewer reactors, a wastewater treatment reactor, and an anaerobic sludge digester. The system was fed with real domestic wastewater. The total mass of 11 PFAAs flowing out of the laboratory wastewater system significantly (p < 0.05) increased by 112 ± 14 (mean ± standard error)% compared to that entering the system. Formation of PFAAs was observed in all three biological processes of the system. In anaerobic sewer process, perfluoropentanoic acid (PFPeA), perfluoroheptanoic acid (PFHpA), and perfluorooctane sulfonate (PFOS) exhibited significant formation (p < 0.05) with the mass flow increased by 79 ± 24%, 109 ± 31%, and 57 ± 17%, respectively. During the wastewater treatment process, perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), and perfluorododecanoic acid (PFDoDA) demonstrated significant increase (p < 0.05) in their mass flows by 176 ± 56%, 92 ± 21%, and 516 ± 184%, respectively. In contrast, only PFHxA was found to significantly (p < 0.05) increase by 130 ± 40% during anaerobic digestion process. The total mass of 11 PFAAs discharged through the effluent (201 ± 24 ng day−1) was 5 times higher than that through the digested sludge (29 ± 6 ng day−1).

Formation and partitioning behaviour of perfluoroalkyl acids (PFAAs) in waste activated sludge during anaerobic digestion

The formation and fate of perfluoroalkyl acids (PFAAs) in sludge during anaerobic digestion (AD) is of global importance since the sludge is a significant source of PFAAs to the environment. The formation of PFAAs from polyfluorinated compounds, namely PFAA precursors, is poorly understood in AD. This study aims to investigate the formation of PFAAs from precursors and their partitioning behaviour in waste activated sludge (WAS) during AD process. To achieve this, three isotope-labelled PFAAs were spiked and monitored along with indigenous PFAAs and precursors over eight weeks in a laboratory-scale anaerobic digester, fed with sludge from a local wastewater treatment plant and operated with a hydraulic retention time of 12 days under 35 ℃. In addition to isotope-labelled PFAAs, twelve native PFAAs and eight polyfluorinated compounds were detected in the feed and digested sludges. A mass-balance model, validated by the spiking experiment, was applied to predict the concentrations of PFAAs and precursors assuming no formation/degradation in AD. The measured concentrations of short-chain PFAAs (perfluoroalkyl carboxylates (PFCAs): C < 8; perfluoroalkane sulfonates (PFSAs): C < 6) in the AD sludge were significantly (p < 0.05) higher than the model-predicted concentrations, indicating the formation of these PFAAs from precursors in AD. In contrast, the formation of long-chain PFAAs (PFCAs: C ≥ 8; PFSAs: C ≥ 6) was not observed. Moreover, the degradation of two polyfluoroalkyl phosphates (PAPs) (6:2 PAP and 6:2/8:2 diPAP) occurred, evidenced by their measured concentrations that were statistically lower than the mass-balance predictions. Further, the AD process reduced the amount of PFAAs absorbed/adsorbed to sludge, particularly for the long-chain ones, due to the breakdown of solids.

Investigating sources and pathways of perfluoroalkyl acids (PFAAs) in aquifers in Tokyo using multiple tracers

We employed a multi-tracer approach to investigate sources and pathways of perfluoroalkyl acids (PFAAs) in urban groundwater, based on 53 groundwater samples taken from confined aquifers and unconfined aquifers in Tokyo. While the median concentrations of groundwater PFAAs were several ng/L, the maximum concentrations of perfluorooctane sulfonate (PFOS, 990ng/L), perfluorooctanoate (PFOA, 1800ng/L) and perfluorononanoate (PFNA, 620ng/L) in groundwater were several times higher than those of wastewater and street runoff reported in the literature. PFAAs were more frequently detected than sewage tracers (carbamazepine and crotamiton), presumably owing to the higher persistence of PFAAs, the multiple sources of PFAAs beyond sewage (e.g., surface runoff, point sources) and the formation of PFAAs from their precursors. Use of multiple methods of source apportionment including principal component analysis–multiple linear regression (PCA–MLR) and perfluoroalkyl carboxylic acid ratio analysis highlighted sewage and point sources as the primary sources of PFAAs in the most severely polluted groundwater samples, with street runoff being a minor source (44.6% sewage, 45.7% point sources and 9.7% street runoff, by PCA–MLR). Tritium analysis indicated that, while young groundwater (recharged during or after the 1970s, when PFAAs were already in commercial use) in shallow aquifers (<50m depth) was naturally highly vulnerable to PFAA pollution, PFAAs were also found in old groundwater (recharged before the 1950s, when PFAAs were not in use) in deep aquifers (50–500m depth). This study demonstrated the utility of multiple uses of tracers (pharmaceuticals and personal care products; PPCPs, tritium) and source apportionment methods in investigating sources and pathways of PFAAs in multiple aquifer systems.