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 82 fluorotelomer alcohol (82 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 82 FTOH remaining after ∼400 days compared to a half-life ranging from 12.5 to 36.5 days under nitrate-reducing conditions. Transformation products 82 fluorotelomer saturated and unsaturated carboxylic acids (82 FTCA and 82 FTUA) were detected under all redox conditions, while 72 secondary fluorotelomer alcohol (72 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-73 acid (F(CF2)7CFHCH2COOH) were identified for the first time during 82 FTOH biotransformation. Comprehensive biotransformation pathways for 82 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.