Utilizing Pine Needles to Temporally and Spatially Profile Per- and Polyfluoroalkyl Substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are a class of manmade organofluorine chemicals used in a variety of household and industrial applications. PFAS have become a global concern due to their environmental persistence, bioaccumulative nature, and associations with adverse health effects, thus monitoring both spatial and temporal PFAS presence is crucial. PFAS levels are commonly monitored in surface and groundwater, soil, and wildlife samples, however assessing atmospheric PFAS is less common due to the necessary expensive equipment which can only be placed at a limited number of sites. Recently, the passive sampling capabilities of trees have been investigated to address this challenge. For example, pine needles possess highly adsorptive wax cuticles and have been effective passive samplers for a wide variety of environmental contaminants, including legacy PFAS or PFAS compounds with long aliphatic chains. To understand PFAS contamination in North Carolina from point sources such as a fluorochemical manufacturer, military bases, and airports, we leveraged the passive sampling capabilities of pine needles. The PFAS in the needles were extracted with an optimized protocol and analyzed using a non-targeted platform coupling liquid chromatography, ion mobility spectrometry and mass spectrometry (LC-IMS-MS) separations, allowing simultaneous hydrophobicity, size, and mass evaluations. This new method resulted in the identification of over 60 PFAS compounds in the pine needles, along with the detection of more than 10 unknown PFAS species. Furthermore, the detected species covered all of the legacy compounds identified in previous studies, as well as multiple classes of emerging PFAS with shorter aliphatic chains and structural modifications such as ether linkages and branched or cyclic aliphatic chains, not previously detected in pine needles. This method was also successful in identifying multiple PFAS point sources, as well as longitudinally monitoring the levels of the diverse PFAS compounds across North Carolina to address environmental concentration changes due to introduction and remediation efforts. Additionally, archived pine needles were analyzed to assess historical PFAS levels from the 1960s-2000s.