Unlocking the past: Release of hazardous contaminants into water from thawing permafrost

Permafrost covers nearly 15 % of the northern hemisphere's land and is a repository of inorganic and organic chemicals and entombed microbes. The warming of the climate will likely lead to the thawing of more than two-thirds of this frozen environmental system by the end of the century and alter the permafrost terrain profoundly. Thermokarst lakes and wetlands generated will be such landforms placed at the first line of exposure of the released hazardous constituents. This perspective presents the state of knowledge on permafrost's biogeochemistry across the globe to anticipate potential release of hazardous biogeochemical materials and evaluates the overlap of temperature anomaly with the existing permafrost and thermokarst regions. The analyses presented in this perspective highlight that toxic metal(loids) [e.g., As, Cr, Ni, Co, Hg, etc.], microbes [e.g., methanogens, iron and sulfate reducers, ammonia oxidizers, H1N1, Alaskapox viruses, and psychrophilic fungi, etc.], and synthetic organics [e.g., PAHs, PFAS, etc.] have been found to have released from permafrost and such release will be exacerbated with the warming climate. This perspective further notes that release and fate of hazardous chemical and biological contaminants will be driven by the complex interplay between biogeochemistry, hydrogeology, and exacerbated thawing.