Melting cryosphere enhanced pollutants release on the Qinghai-Tibet Plateau: current status and environmental impacts

The cryosphere on the Qinghai-Tibet Plateau (QTP) is undergoing continuous and rapid shrinkage due to rapid climate warming. Such retreating has resulted the massive release of toxic pollutants (e.g., mercury, microplastics, halogenated organic compounds) and pathogenic microorganisms previously “frozen” in glaciers and permafrost. The releasing pollutants play an important role on regional water security, ecosystem stability, and sustainable development. Studies have revealed toxic pollutants (e.g., mercury) and new contaminants (e.g., microplastics) in the glaciers, soils, and rivers and lakes of the QTP. The total mercury export flux from glacial runoff is approximately 50 kg·a⁻¹, with microplastic release reaching around 10¹⁴ items·a⁻¹. The mercury storage amounts to be about 86.6 Gg in the upper soil layer (0–3 m) of the plateau’s permafrost. The reserve of halogenated organic compounds is estimated to be about 176 Gg (0–3 m soil layer), over 85% of these non-extractable residual halogenated organic compounds are physically sequestered, exhibiting higher release potential compared to chemically bound forms. Permafrost thaw slumping can result in an estimated 2,900 kg of mercury release, which may also increase the risk of releasing “dormant” pathogenic microorganisms. These processes pose potential threats to the water quality security of some rivers and lakes on the plateau. In the future, the QTP will continue to warm, leading to cryosphere shrinking. Consequently, the release of toxic pollutants from the retreating cryosphere will enhance, and their transport to downstream water system will exacerbate potential risks to water resource and ecological environment. It is therefore urgent to establish a comprehensive monitoring network for cryosphere-associated pollutants across the QTP, coupled with modeling framework. This will enable to characterize the distribution, migration and environmental effects of released pollutants, further providing scientific and technological support for estimating the potential environmental risks arising from cryosphere melting.