Svalbard: Arctic snow as an unexpected laboratory of natural chemistry

A study published in Science Advances and conducted by the Institute of Polar Sciences of the National Research Council of Italy in Venice (Cnr-Isp), in collaboration with Ca’ Foscari University of Venice, the University of Perugia and other international partners, has identified for the first time the presence and formation mechanism of bromate in the Arctic snowpack. Bromate is a bromine compound, a chemical element of particular importance in this region because it is involved in processes that characterise the Arctic atmosphere.

“Bromine plays a central role in the atmospheric chemistry of polar regions,” explains Stefano Frassati, the study’s author and a PhD student at Ca’ Foscari University of Venice. “Its reactions can trigger processes that lead to ozone depletion and influence the cycles of other atmospheric compounds. For this reason, it is essential to understand how it is stored and transformed in the snowpack.”

The international team of researchers, also thanks to collaboration with the Italian Dirigibile Italia base managed by Cnr-Isp, analysed snow and aerosol samples collected in Ny-Ålesund, in the Svalbard archipelago, during the winter and spring of 2022.

The research demonstrated the existence of a previously unknown process occurring within the snowpack that leads to the formation of bromate under natural conditions.

“With the increase in solar radiation during the polar spring, light-induced chemical reactions are activated. Bromide present in the snow, which in this environment is the main chemical form of bromine, can be oxidised to form bromate, a much more stable form that can accumulate both in the snowpack and in the surrounding environment,” notes Andrea Spolaor, a researcher at Cnr-Isp and co-author of the study.

The study used more sensitive analytical techniques than those available in the past. Moreover, by employing specific protocols for identifying oxidised bromine species, it was possible to detect bromate even at low concentrations, thereby overcoming the limitations of previous studies.

In addition, quantum-mechanical calculations defined the chemical mechanism underlying the formation of bromate in snow.

“By combining advanced experiments with sophisticated theoretical models, it was possible to clarify the dynamics of elementary chemical processes operating in a highly complex medium such as snow,” emphasises David Cappelletti, professor at the University of Perugia and co-author of the study. Although it does not directly affect current climate change, this discovery is significant because it improves our understanding of ozone chemistry in polar regions, where snow can act as a chemical reactor and a reservoir of non-reactive bromine—an aspect that had not previously been considered in atmospheric models.