Ice Nucleation Activity of Perfluorinated Organic Acids.

Ralph Schwidetzky,Janine Fröhlich-Nowoisky,Anna T Kunert,Yuling Sun,Mischa Bonn,Konrad Meister

doi:10.1021/acs.jpclett.1c00604

Abstract

Perfluorinated acids (PFAs) are widely used synthetic chemical compounds, highly resistant to environmental degradation. The widespread PFA contamination in remote regions such as the High Arctic implies currently not understood long-range atmospheric transport pathways. Here, we report that perfluorooctanoic acid (PFOA) initiates heterogeneous ice nucleation at temperatures as high as −16 °C. In contrast, the eight-carbon octanoic acid, perfluorooctanesulfonic acid, and deprotonated PFOA showed poor ice nucleating capabilities. The ice nucleation ability of PFOA correlates with the formation of a PFOA monolayer at the air–water interface, suggesting a mechanism in which the aligned hydroxyl groups of the carboxylic acid moieties provide a lattice matching to ice. The ice nucleation capabilities of fluorinated compounds like PFOA might be relevant for cloud glaciation in the atmosphere and the removal of these persistent pollutants by wet deposition.

Highlights

Perfluorinated acids (PFAs) are widely used synthetic chemical compounds, highly resistant to environmental degradation
Perfluorinated acids (PFAs) such as perfluorooctanoic acid (PFOA) or perfluorooctanesulfonic acid (PFOS) are anthropogenically generated compounds that have emerged as significant global environmental pollutants with persistent, bioaccumulative, and toxic properties.[1,2]
The adverse environmental effects of PFAs have led to their addition to annexe A of the Stockholm Convention for persistent organic pollutants, and PFOS and related chemicals were voluntarily removed from the market.[3]

Summary

Introduction

Perfluorinated acids (PFAs) are widely used synthetic chemical compounds, highly resistant to environmental degradation. At PFOA concentrations up to 0.02 mg/L, the ice nucleation activity is negligible, with freezing occurring at T50 = ∼ −28 °C, comparable to pure water in our experimental setup.

Results

Conclusion