Article**: Oceans and Wetlands.
Methylmercury (MEHG).It is a highly toxic toxin that poses a threat to marine life and human health. The consumption of marine fish threatens the survival of people around the world and is expected to cause global economic losses of US$19 trillion by 2050. The United Nations Minamata Convention on Mercury aims to reduce human exposure to mercury by reducing anthropogenic emissions. It is believed that,Anthropogenic mercury emissions have tripled ocean surface mercury levels since pre-industrial times。However, in order to quantify the extent to which anthropogenic mercury emissions increase marine mercury levels, it is critical to estimate natural mercury levels.
Researchers from the Kilhelmholtz Centre for Oceanography have quantified the mercury released from the mid-Atlantic ridge transatlantic geotr**erse hydrothermal vents using a combination of observations of seafloor hydrothermal vent fluids, plume currents, seawater and rock samples. The study found that most of the mercury (67-95%) enriched in the effluent fluid was rapidly diluted to seawater background levels. A small fraction of mercury (26-10%) were cleared into the rocks of the transatlantic geological crossing mound . The researchers came up with an estimate of 1. per year5-64.Seven tonnes of mercury flux came from mid-ocean ridges. This hydrothermal flux is less as compared to human input. This suggests that most of the mercury present in the ocean must be man-made**, the implementation of the emission reduction measures outlined in the Minamata Convention could effectively reduce mercury levels in the global oceans and, in turn, in marine fish. The study was published in Nature Earth Sciences.
Photo: The fifth meeting of the Conference of the Parties to the Minamata Convention was held in Geneva, Switzerland, at the end of October 2023 Photo: Minamata Convention
In 2013, the United Nations adopted the Minamata Convention on Mercury, which aims to minimize mercury pollution in the environment to protect human health. One of the main human mercury intakes** is the consumption of contaminated fish, which accumulate mercury dissolved in seawater. It is estimated that anthropogenic activities have increased global marine mercury stocks by 21 per cent. However, this figure is difficult to verify, as it is not clear how much natural mercury is present in the ocean before anthropogenic emissions begin. Therefore, it is difficult to say how much these factors affect the mercury levels in fish.
To fill this knowledge gap, researchers have made the first global estimate of mercury emissions from hydrothermal sources in mid-ocean ridges, volcanically active regions of the world's oceans.
"Comprehensive observations show that most of the mercury accumulated in the thermal solution is diluted in seawater, and only a small part is precipitated locally and remains on the seafloor," the researchers said. Overall, the global hydrothermal mercury fluxes of the mid-ocean ridge are small compared to anthropogenic mercury emissions. Researchers hope that strict implementation of the emission reduction measures set out in the Minamata Convention will reduce mercury levels in fish and humans.
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References
1. natalia torres-rodriguez et al, mercury fluxes from hydrothermal venting at mid-ocean ridges constrained by measurements,nature geoscience (2023). doi: 10.1038/s41561-023-01341-w
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