🏔️ Mercury pollution: melting glaciers release this toxic metal in the Alps

While atmospheric mercury (Hg) emissions have sharply declined in Europe since the 1970s thanks to environmental policies, climate change could disrupt this trend in high mountain regions.

A study published in Environmental Science & Technology and supported by the LabEx OSUG reveals that the melting of Alpine glaciers remobilizes mercury accumulated over several decades, leading to an unexpected increase in inputs to certain lakes.


To reach this conclusion, scientists analyzed sedimentary records from two neighboring Alpine lakes: a lake fed by precipitation, a direct reflection of atmospheric deposits, and a proglacial lake fed by meltwater. Using radionuclide dating methods, they reconstructed the evolution of mercury inputs over more than a century.

Comparison of these records shows opposite trajectories: a consistent decrease in line with the decline in emissions in the first lake, but a continuous increase in the proglacial lake.

These results indicate that glacial melt releases mercury formerly trapped in the ice, masking the benefits of emission reduction policies. Across the Alps, the expected disappearance of a significant portion of glacial volume could release substantial amounts of mercury into the environment, up to 2,200 pounds (1000 kg) by the end of the century.

Once released, this mercury can be transformed into methylmercury, a toxic form that accumulates in food chains. This time lag between emission reduction and ecosystem response highlights the need to integrate climate change effects into the evaluation of environmental policies, such as the Minamata Convention.

More broadly, this study underscores the importance of environmental reservoirs, such as glaciers, in the global mercury cycle and opens new perspectives for better anticipating the combined impacts of climate and pollution.