New study reveals how oxidized mercury behaves in the atmosphere, enabling improved understanding of environmental and health impacts

A new international study, led by CARE-C, The Cyprus Institute, published in Nature Communications, provides the first direct molecular-level observations of oxidized mercury species in the atmosphere, challenging long-standing assumptions used in global models. Mercury is a persistent environmental pollutant with serious implications for ecosystems and human health, making its molecular study crucial for accurate environmental assessments.

In the study, researchers report direct in-situ observations of oxidized mercury compounds in polar air, including halogen-containing species such as mercury bromide, chloride, and iodide. The measurements were made using advanced atmospheric pressure chemical ionization mass spectrometry (CI-APi-TOF), combined with ambient ion composition analysis.

A key finding is that mercury dibromide (HgBr₂) dominates oxidized mercury speciation in polar regions. This contradicts widely used atmospheric models, which have assumed different dominant species and reaction pathways. The results indicate that important chemical processes are currently missing or misrepresented in these models.

In the atmosphere, mercury can exist in a stable elemental form, allowing it to travel long distances. Once oxidized, mercury becomes more reactive and highly water-soluble, leading to rapid removal from the atmosphere through wet and dry deposition. This enhanced solubility facilitates its transfer into aquatic ecosystems via precipitation. This process is particularly important in polar regions.

During spring, returning sunlight triggers photochemical reactions in saline snowpacks, releasing reactive bromine. These bromine radicals rapidly oxidize atmospheric mercury, often within hours, causing pulses of gaseous oxidized mercury deposition. This deposited mercury can then enter marine food webs, posing risks to Arctic communities that rely on seafood.

By providing real-time molecular-level measurements, the study establishes a stronger observational foundation for understanding mercury cycling in the atmosphere. This improved understanding is essential for predicting where mercury deposits and how it impacts sensitive ecosystems.

According to the study’s lead author, CARE-C Associate Professor Tuija Jokinen: “This approach opens new possibilities for studying mercury chemistry beyond polar regions. Applying these methods to urban, marine, and volcanic environments and reanalyzing existing datasets could significantly refine our understanding of global mercury transport and transformation. Ultimately, these advances support more accurate environmental assessments and strengthen efforts to protect ecosystems and human health from mercury pollution.”

The work was carried out as part of the European Research Council (ERC) under the European Union’s Starting Grant project BAE.

Reference:
Jokinen, T., Gómez Martín, J.C., Feinberg, A. et al. Direct observations of atmospheric oxidized mercury speciation in polar areas. Nat Commun 17, 3160 (2026). https://doi.org/10.1038/s41467-026-71146-z