Mercury is a toxic heavy metal and a global pollutant with special physical and chemical properties, and its cycle is mainly controlled by oxidation-reduction reactions carried out by photochemical or microbial process under suitable conditions. 

The accumulation and deposition of methylmercury (MeHg) in various ecosystems, including the cryospheric components such as snow, meltwater, glaciers, and ice sheet, and subsequently in the food chain pose serious health concerns for living beings. 

However, unlike the abundance of knowledge about the processes of MeHg production over land and oceans, little is known about the sources and production/degradation rate of MeHg in cryosphere systems. 

Therefore, it is essential to study the deposition and accumulation by biological, physical, and chemical mechanisms involved in Hg methylation in the cryosphere. 

Recently, a research group from Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences focused on the variability in Hg concentation and mechanisms of Hg methylation, including physical, chemical, microbial, biological processes, and transportation in the cryosphere. 

Scientists elaborated on the mechanism of redox reactions and biotic and abiotic factors controlling Hg methylation and biogeochemistry of Hg in the cryosphere. 

Besides, they also present possible mechanisms of Hg methylation with an emphasis on microbial transformation and molecular function to understand variability in Hg concentation in the cryosphere. 

This study would help not only to understand the physicochemical mechanism of Hg and its methylation processes in the cryosphere but also to understand the genomics behind it and obtain insights into its effect on climate change. 

The study result was published in Science of the Total Environment. 

Biogeochemical cycles of Hg methylation in the cryosphere (Image by KANG Shichang)