Arctic snow as a chemical reactor, a new bromine cycle discovered

Bromine plays a central role in the balance of the polar regions. As explained by Stefano Frassati, author of the study and doctoral student at Ca’ Foscari: “Its reactions can trigger processes that lead to the destruction of ozone and also influence the cycling of other atmospheric compounds. This is why it is essential to understand how it is stored and transformed in the snowpack“.

Sampling of the snow cover during the spring period (credits: Federico Scoto / Cnr-Isp)

The mechanism of bromate formation

The analyzes were conducted on snow and aerosol samples collected in 2022 at the Italian base “Dirigibile Italia” in Ny-Ålesund. The results highlight that, with the return of light during the polar spring, solar radiation activates specific reactions. Under these conditions, the bromide present in the snow oxidises, transforming into bromatea much more stable chemical species.

Andrea Spolaor, researcher at the Cnr-Isp, clarifies the relevance of the discovery: “Bromide […] can oxidize to form bromate, a much more stable species that can accumulate both in the snowpack and in the surrounding environment“. This accumulation process represents a reservoir of non-reactive bromine that previous atmospheric models had not considered.

Front of the Confortlessbreen glacier, on the island of Spitsbergen (credits: Federico Scoto / Cnr-Isp)

Analytical innovation and theoretical models

The success of the research depended on the use of highly sensitive analytical techniques and specific protocols for the identification of oxidized species, capable of detecting the compound even at extremely low concentrations. The contribution of quantum mechanics was also fundamental to define the elementary chemical mechanism.

David Cappelletti, professor at the University of Perugia, underlines the importance of methodological integration: “By combining advanced experiments with sophisticated theoretical models it has been possible to clarify the dynamics of elementary chemical processes acting in a highly complex medium such as snow“. Although the discovery does not directly influence climate change, it improves understanding of the chemistry of ozone at the poles, providing crucial data for future climate and atmospheric models.