Snow and ice can capture and store contaminants both local and global in origin. The decrease in glacier cover, snow cover and sea ice in response to climate affects cycling of airborne impurities in polar and alpine environments, accelerating and enhancing their release. In this context snow and ice act as a secondary source for numerous organic and inorganic atmospheric contaminants that were deposited on their surface during recent decades, including persistent organic pollutants, radioactive species, microplastics, pesticides, and heavy metals. The release of contaminants from snow and ice to glacier forefields, rivers and seas might pose a hazard to these ecosystems and to human health, particularly under accelerated melt conditions.

Identification and assessment of this hazard relies, for each contaminant class, on the understanding of processes that control their accumulation, release and downstream transport. The physical and chemical forms in which contaminants are removed from the atmosphere and hydrosphere may further affect their interactions with mineral substances and biota. Existing studies suggest that the contaminant release process is not linear, and that interactions between meltwater, supraglacial debris and glacial microbiology may be crucial in the accumulation and transport of contaminants in glacier catchments. For example, evidence is mounting that cryoconite can efficiently accumulate radionuclides from anthropogenic sources to potentially hazardous levels in glaciers around the world. At the same time, the high biological activity present in cryoconite could enhance the degradation of organic pollutants, with important implications for remediation. A portion of contaminants released from glaciers may also be stored in their proglacial zones as shown by the very high concentrations of radionuclides found by several recent studies. The effects of contaminant transport on the pro-glacial environment and downstream communities remain uncertain, but improved understanding of the impacts of contaminants in land ice, sea ice, and snow is clearly warranted.

The session aims to contribute to the development of this emerging and interdisciplinary field, welcoming presentations from across cryospheric, hydrological, and biogeochemical sciences, and other research areas.