Summary:
Human-driven changes in the atmosphere have altered how mercury moves around the planet, according to a study published in AGU Advances. Using chemistry-climate modelling, the researchers compared preindustrial atmospheric conditions around 1850 with present-day conditions from 2010 to 2019 to test whether mercury’s chemical lifetime has stayed stable over time, as many earlier studies assumed.
They found that rising levels of ozone and hydroxyl radicals have sped up oxidation of elemental mercury by 16% in the Northern Hemisphere, while changes in bromine chemistry have slowed that process by 20% in the Southern Hemisphere. Globally, these opposing shifts partly balance each other, but they still change where mercury ends up. The study found that present-day atmospheric conditions drive 15% more mercury deposition to tropical and subtropical oceans, regions tied closely to fisheries and human exposure to toxic methylmercury.
The results also suggest the preindustrial atmosphere was more favorable to mercury reaching remote parts of the Southern Hemisphere, which could affect how scientists read historical mercury records from sediments, ice cores and other natural archives.
— Press Release —
Human Effects on Background Atmosphere have Affected Mercury Chemistry
The amount of time that mercury (Hg) spends in the atmosphere determines its global spread, and therefore the distribution of this toxic pollutant, even to remote ecosystems. Generally, previous studies have assumed the chemical lifetime of elemental mercury (Hg⁰) has been constant throughout history, mirroring the conditions of present-day (2010–2019). However, since pre-industrial times (about 1850), anthropogenic emissions have altered the concentrations of oxidants that affect the lifetime of Hg⁰, including bromine radicals (Br), hydroxyl radicals (OH), and ozone (O₃).
Feinberg et al. (2026) use a state-of-the-art chemistry-climate model to analyze the effects of the changes in background composition between 1850 and now to examine the resulting effects on mercury deposition into water around the world. The increasing concentrations of OH and O₃ lead to 16% faster Hg⁰ oxidation in today’s Northern Hemisphere, while the increased partitioning of Br to reservoir species slows Hg⁰ oxidation by 20% in the Southern Hemisphere relative to the 1850 atmosphere. These regional oxidation changes shift the pattern of where Hg deposits to the surface.
The shifts in Hg⁰ oxidation enhance deposition by 15% to tropical and subtropical oceans, which are critical regions for Hg exposure risks. The 1850 atmosphere, however, was more conducive to the spread of Hg to the remote Southern Hemisphere extratropics. This finding significantly affects the interpretation of the Hg deposition historical records from natural archives. This study reveals that the changing atmospheric composition has been a previously overlooked factor when considering human Hg exposure risk via altered Hg deposition patterns.
Journal Reference:
Feinberg, A., Sonke, J. E., Cuevas, C. A., Li, M.-L., Acuña, A. U., Fernandez, R. P., et al., ‘Shifts in atmospheric composition since the preindustrial era modified the transport and deposition of mercury’, AGU Advances 7, (1): e2025AV002158 (2026). DOI: 10.1029/2025AV002158
Article Source:
Press Release/Material by Donald Wuebbles | EOS | CC BY-NC-ND
Featured image credit: Feinberg et al. (2026) | AGU Advances | CC BY
