Biotransformation of 8:2 Fluorotelomer Alcohol in Soil from Aqueous Film-Forming Foams (AFFFs)-Impacted Sites under Nitrate-, Sulfate-, and Iron-Reducing Conditions

Abstract

The environmental fate of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foams (AFFFs) remains largely unknown, especially under the conditions representative of natural subsurface systems. In this study, the biotransformation of 8:2 fluorotelomer alcohol (8:2 FTOH), a component of new-generation AFFF formulations and a byproduct in fluorotelomer-based AFFFs, was investigated under nitrate-, iron-, and sulfate-reducing conditions in microcosms prepared with AFFF-impacted soils. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) and high-resolution mass spectrometry (HRMS) were employed to identify biotransformation products. The biotransformation was much slower under sulfate- and iron-reducing conditions with >60 mol % of initial 8:2 FTOH remaining after ∼400 days compared to a half-life ranging from 12.5 to 36.5 days under nitrate-reducing conditions. Transformation products 8:2 fluorotelomer saturated and unsaturated carboxylic acids (8:2 FTCA and 8:2 FTUA) were detected under all redox conditions, while 7:2 secondary fluorotelomer alcohol (7:2 sFTOH) and perfluorooctanoic acid (PFOA) were only observed as transformation products under nitrate-reducing conditions. In addition, 1H-perfluoroheptane (F­(CF2)6CF2H) and 3-F-7:3 acid (F­(CF2)7CFHCH2COOH) were identified for the first time during 8:2 FTOH biotransformation. Comprehensive biotransformation pathways for 8:2 FTOH are presented, which highlight the importance of accounting for redox condition and the related microbial community in the assessment of PFAS transformations in natural environments.

Concentrations of 45 Per- and Polyfluoroalkyl Substances in North American River Otters (Lontra canadensis) from West Virginia, USA

“…The intermediates 8:2 FTUCA and 8:2 FTCA in the metabolism of 8:2 fluorotelomer alcohol (FTOH) 26 frequently occurred in all river otter tissues (DF ≥ 64%), at median concentrations in the ranges of 0.07−0.56 and 0.33−3.55 ng/g ww, respectively (Table 1), indicating widespread distribution of 8:2 FTOH in the aquatic environment. 27 PFOSA is a metabolite of Nmethyl-and N-ethyl-perfluorooctanesulfonamidoalcohols, which are used for surface treatment of textiles and specialty papers. 28 PFOSA was found in all river otter samples (DF: 100%) at hepatic concentrations (median: 6.87 ng/g ww) similar to those reported from Southern Sweden during 1972− 2011 (median: 8.6 ng/g ww).…”

Network Meta-Analysis and Systematic Review of Conditions Facilitating Microbial Biotransformation of 6:2 and 8:2 Fluorotelomer Alcohols to Perfluoroalkyl Carboxylates

“…Microbial community or activity data were mostly unavailable across the selected studies, with the exception of one report. 18 Therefore, any association between community dynamics and transformation was left unexamined in this study as a result of insufficient availability of comparisons.…”

“…One report examined FTOH transformation in brackish water under aerobic and anoxic/microoxic (∼1 mg/L dissolved oxygen) conditions further evaluated the effects of transformation when incubated at 5 °C (n = 6 experimental, n = 4 control), 10 °C (n = 6 experimental, n = 4 control), 15 °C (n = 6 experimental, n = 4 control), and 20 °C (n = 6 experimental, n = 4 control). 18 FTOH-to-PFCA transformation was evaluated across twenty-one experimental (and corresponding controls) groups in the presence of oxygen (n = 66 experimental, n = 59 control), while 13 were evaluated in the absence of oxygen or under microoxic conditions (n = 39 experimental, n = 35 control). Of those conducted anaerobically, direct comparisons of FTOH transformation under iron (n = 6 experimental, n = 6 control), nitrate (n = 6 experimental, n = 6 control), and sulfate reducing conditions (n = 6 experimental, n = 6 control) were investigated in soil microcosms.…”

“…18 The effects of lactate + diethylene glycol monobutyl ether (DGBE) or DGBE alone were assessed across 6 experimental and control groups (n = 18 experimental; n = 18 control groups). 18 Note that DGBE was a major constituent of PFAS-containing aqueous film forming foams (AFFF) used primarily for extinguishing hydrocarbon fires.…”

“…Screened full-text articles ( n = 14 titles) were chain searched to ensure that, to the greatest possible extent, all literature related to this theme were considered for the meta-analysis ( n = 2,685 titles). − Forward searching was conducted using Google Scholar to identify all literature sources that cited selected full-text articles. Reverse searching was conducted by compiling the cited literature within the selected full-text articles.…”