Fate of ‘forever chemicals’ in the global cryosphere

The cryosphere serves as a significant sink in the global circulation of organic pollutants. Among them, per- and polyfluoroalkyl substances (PFAS), known as “forever chemical”, are of great concern as their concentrations surpass the Earth's planetary safety boundary. In this review, we synthesize knowledge on the fate of PFAS in the cryosphere, focusing on their sources, accumulation, release process, and ecological effects. Long-range atmospheric transport leads to widespread of PFAS in the cryosphere, whereas local activities are primarily responsible for the regional PFAS pollution. Because of the wide replacements of the ozone-depleting chlorofluorocarbons after the Montreal Protocol, the ultra-short chain (C < 4) PFAS, particularly trifluoroacetic acid, have emerged as the predominant compounds in the cryosphere, which may become a focus of future research. Cryospheric components such as snowfall, sea ice, and permafrost are important accumulation reservoirs of PFAS, while under climate warming, air-snow exchange, sea-ice melting and permafrost thaw lead to redistribution of PFAS. During snow/ice melt, short-chain PFAS are released earlier than long-chain PFAS. The PFAS remaining in the proglacial environment exhibit a range of ecological effects on both micro- and higher trophic organisms through the food web, ultimately leading to biodiversity loss. Our analysis shed light on the fate of PFAS in the cryosphere under climate warming and highlighted the urgent need for their long-term monitoring and study of PFAS in glacial regions to protect the fragile ice world.