An updated global mercury budget from a coupled atmosphere-land-ocean model: 40% more re-emissions buffer the effect of primary emission reductions

The effectiveness of reducing the environmental level of mercury (Hg) by controlling anthropogenic emis-sions depends on the magnitude of re-emissions from the land and ocean, which requires a comprehensive understanding of its global biogeochemical cycle. Recent advances in atmospheric Hg redox chemistry, vegetation uptake, seawater Hg sources, and riverine discharges greatly challenge our understanding of the global Hg cycle, but the overall effects remain understudied. Here, we develop a new coupled atmo-sphere-land-ocean model and find potentially 40% higher total atmospheric Hg emissions than previously recognized primarily because of higher re-emissions from the ocean. Our results suggest a likely smaller sensitivity of environmental Hg levels to anthropogenic emission changes, stressing that potentially more aggressive emission control is required to decrease Hg levels.

Automated summary

The effectiveness of reducing environmental mercury levels by controlling anthropogenic emissions depends on the magnitude of re-emissions from the land and ocean. Recent advances in atmospheric mercury chemistry, vegetation uptake, seawater mercury sources, and riverine discharges challenge our understanding of the global mercury cycle. A new coupled atmosphere-land-ocean model suggests potentially higher atmospheric mercury emissions and emphasizes the need for more aggressive emission control to decrease mercury levels.