Analysis of PFAS in Cloud Water at Sonnblick observatory

Abstract

Clouds form a main part of the water cycle. Thus, clouds are responsible for the transport and distribution of components dissolved and dispersed in the cloud water, throughout the environment. Per- and poly fluorinated alkyl substances (PFAS) are gaining increased interest due to several adverse effects on health and due to their physical, chemical properties like their stability, persistence and their properties as surfactants. Increasing literature about PFAS in aerosol (Faust, J. 2022) and precipitation is available (Coates, K. A. et al., 2024), not so for cloud water, although cloud droplets present the link between these “compartments”. Here the analysis of PFAS in cloud water is performed, starting with 20 PFAS mentioned in the EU drinking water guideline. Analysis is done using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The aim was to determine which PFAS could be found in detectable concentrations, to see if they are comparable with aerosol measurements. Sampling of cloud water was performed at Sonnblick observatory (SBO) at summit of “Hoher Sonnblick” (3106 m height), in the Austrian Alps, by an active cloud water sampler (CWS) on an impaction stage made of acrylic glas. The campaign in August 2024 included 14 days during which, whenever a cloud event occurred, sampling was carried out at intervals of approx. 20 mins to 10 hours, depending on the liquid water content (LWC) of the cloud. In total, 54 samples were collected and analyzed for selected inorganic ions, organic acids and selected carbohydrates. Additionally, 34 of these samples were analyzed for PFAS. Short chain PFAAS (C4 to C7) were already noticed to be present in detectable amounts in cloud water and connected with dust and combustion particles as tracers (Edwards, E. et al., 2023). Consistent with prior works, the most frequently found molecule PFBA, is occurring in concentrations up to 22 ng/L. Generally, PFAAS were more present than PFASS. This is consistent with other studies on atmospheric PFAS (J. Faust, 2022). More measurements are necessary to improve understanding of atmospheric transport of PFAS. This work was supported by Geosphere Austria and is granted by Forschungs- und Förderungsgesellschaft Österreich (FFG) since March 2023.