PFAS Occurrence, Biotransformation, and Transport through Vegetation

Abstract

Contamination of per- and polyfluoroalkyl substances (PFAS) has emerged with increasing concern in New Jersey and other states across the country. In this project, we first developed sensitive and reliable PFAS analytical methods using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) and nano-electrospray ionization high-resolution mass spectrometry (Nano-ESI-HRMS). Particularly, analysis by Nano-ESI-HRMS can be complementary to the standard method using LC/MS/MS, since this new approach enables the non-target screening of new PFAS features in environmental and laboratory samples. A standard operating procedure (SOP) for PFAS analysis by this newly developed Nano-ESI-HRMS was generated and attached in the appendix. Second, we further analyzed PFAS in a multimedia environment from four sites in New Jersey. The highest PFAS concentration in surface water was found near the Ringwood Superfund site downstream a waste disposal area on a foamy stream (PFOS 445.56 ng/L). The highest sediment concentration was found near the landfill in Kearny (PFOS replicate range of 3.17-5.79 ng/g). The highest plant concentration was found in Little Pine Lake (PFOS replicate range of 22.79-24.90 ng/g). Perfluorooctane sulfonate (PFOS) was dominantly detected in both plant samples and environmental matrices where the plants were collected, supporting the occurrence of bioaccumulation. Furthermore, perfluorohexanoic acid (PFHxA) was primarily detected in shoot samples of plants, suggesting the uptake and translocation of PFAS from the environment. Using Nano-ESI-HRMS, chloroperfluoropolyether carboxylates (ClPFPECA) in soil and plant samples were screened. However, none of these samples showed significant detection of ClPFPECA, warranting further optimization of the extraction and analytical procedures for the analysis of ClPFPECA in environmental samples. Third, pairing with the observation of PFAS in the field, we characterized the biotransformation of 6:2 fluorotelomer carboxylic acid (6:2 FTCA) by Rhodococcus jostii RHA1, a model rhizospheric bacterium. This bacterium exhibited significant biodefluorination activities that can be sustained by the amendment of carbohydrate substrates, such as glucose and fructose. Coupling with the liberation of free fluoride, a 6:2 FTUCA conjugate molecule (m/z = 696.20) was identified as an important biotransformation product of 6:2 FTCA. Such process was regulated by the presence of copper and other metallic anions, though the molecular foundations remains unknown. Collectively, findings of this study underscore the needs to investigate the PFAS contamination and attenuation in the environment and natural biota (i.e., plants and aquatic animals) in the proximity of landfills. This project has contributed to two research publications to date.