The Wisconsin State Laboratory of Hygiene PFAS Research Center is one of the few groups in the country addressing the atmospheric cycling of per- and polyfluoroalkyl substances (PFAS). Our studies have contributed to the growing evidence of widespread and significant dispersal of PFAS across the globe via transport and transformation in the atmosphere, and we've documented that precipitation of PFAS can represent the major depositional pathway to many environments. Advancing our understanding of PFAS depositional pathways requires information on PFAS in vapor and aerosol phases in the atmosphere - key information that is currently lacking, especially in the US. To this end, we have conducted a novel study, pairing weekly integrated precipitation collection (and PFAS characterization) with an intensive air sampling campaign - collecting PFAS from both aerosol and vapor atmospheric pools. An important parallel goal of this study is to validate the air-sampling methods for a very large suite of PFAS - helping to promulgate a robust approach for PFAS quantification in air that can be applied by researchers world-wide.

For this study, the WSLH partnered with the Wisconsin Department of Natural Resources to collect air (and precipitation) samples at two locations in WI, one urban and one rural. We deployed triplicate co-located high-volume air samplers at each location and collected over 40 samples from each over a period of over a year. Sampling periods ranged from 24 to 96 hours at air flow rates of 130 and 230 liters per minute. Processing nearly 1000 m³ of air is required due to the low ambient concentrations of PFAS in the air (<1-20 pg/m³). The high-volume samplers were configured with glass-fiber filters to collect aerosol-associated PFAS and glass cartridges, containing polyurethane foam (PUF) and cross-linked polyvinyl styrene (XAD) resin, to collect vapor-phase PFAS. A new method was developed to extract the PFAS from the PUF/XAD, that utilizes a shaker table and significantly less organic solvent than the traditional Soxhlet method. To assess PFAS analyte recovery during field collection and laboratory processing, the cartridges are spiked with over 20 isotopically-labeled PFAS surrogates, before deployment. Our current liquid chromatography, tandem mass spectrometry (LC/MS/MS) method targets 33 PFAS compounds with the intent of eventually transitioning to the analytes in EPA method 1633 (41 PFAS compounds), supplemented with several additional air-relevant PFAS species, especially the fluorotelomer alcohols. In the presentation, we will present preliminary method performance data along with new information on PFAS levels in the atmosphere.

¹ Wisconsin State Laboratory of Hygiene, University of Wisconsin-Madison, Madison, WI

* Corresponding Author: elizabeth.marshall@slh.wisc.edu