Cloud plumes from cracks of open water in the arctic sea ice cover. Image Credit: University of Hamburg
Like the swirling air around a pot of boiling water, washing machine like wind currents suck down mercury through cracks in the sea ice also known as leads. This happens when warm ocean water meets the frigid polar air. This turbulence causes a mixing up of the air allowing mercury to enter the ocean.
NASA explains:
Scientists measured increased concentrations of mercury near ground level after sea ice off the coast of Barrow, Alaska, cracked, creating open seawater channels called leads. The researchers were in the Arctic for the NASA-led Bromine, Ozone, and Mercury Experiment (BROMEX) in 2012.
“None of us had suspected that we would find this kind of process associated with leads,” said Son Nghiem, a scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. Nghiem is the BROMEX principal investigator and a coauthor of a paper reporting the discovery published in Nature on Jan. 15.
The mercury-pumping reaction takes place because open water in a lead is much warmer than the air above it, according to study lead author Chris Moore of the Desert Research Institute, Reno, Nev. Because of that temperature difference, the air above the lead churns like the air above a boiling pot. “The mixing is so strong, it actually pulls down mercury from a higher layer of the atmosphere to near the surface,” Moore said. The mixing, marked by dense clouds spewing out of the leads, extends up into the atmosphere about a quarter-mile (400 meters). Moore estimates this may be the height where the mercury pumping occurs.
Almost all of the mercury in the Arctic atmosphere is transported there in gaseous form from sources in areas farther south. Scientists have long known that mercury in the air near ground level undergoes complex chemical reactions that deposit the element on the surface. Once the mercury is completely removed from the air, these reactions stop. However, this newly discovered mixing triggered by leads in the sea ice forces down additional mercury to restart and sustain the reactions
Climate Change will make mercury pollution worse.
The toxic metal's mercurial nature makes it sensitive to changes in climate, according to a study co-authored by Krabbenhoft published today (Sept. 26) in the journal Science.
Wildfires, for example, are expected to become more prevalent in a warming world, said Brian Branfireun, a researcher at the University of Western Ontario in Canada, who wasn't involved in the study. Soils and vegetation can lock up mercury for decades, so when they burn, they can release "potentially significant" amounts of the toxic metal into the atmosphere, Branfireun told LiveScience.
Second, models of climate change generally predict more intense rainfalls and floods, which could increase soil erosion and the release of sediment-bound mercury into rivers and the ocean, according to the study. Wildfire-stricken areas are also known to have higher levels of soil erosion and runoff, the scientists wrote, another possible source of pollution.
Finally, thawing of permafrost in the Arctic as temperatures in the region rise could also lead to more soil runoff of mercury, Branfireun said. "I think undoubtedly the location of the greatest changes will be at the high latitude in the poles, since this is where climate change is increased in magnitude," Krabbenhoft said.
All of these factors could increase the amount of mercury found in the ocean. Scientists focus on oceanic mercury because this is where the element is converted into methylmercury, the toxic, carbon-containing form that accumulates in fish; eating seafood is the primary way humans are exposed to the heavy metal, studies show. Most methylmercury is produced by microbes in the lower ocean's dark conditions, according to a study published earlier this year in Nature Geoscience. [Is Sushi Safe to Eat?]
Mercury is eventually taken out of the reach of humans in deeply buried sediments and at the bottom of the seafloor, but that takes centuries to millennia, Krabbenhoft said.
The
Minamata Convention on Mercury is named after the disastrous Minamata bay disaster which caused Minamata disease. "This was caused by chemical waste dumped in Minamata bay by the Chisso company in Japan. This chemical waste contained methyl mercury which is highly dangerous. The fish in the bay ate this waste then it worked itself up the food chain until it eventually affected humans." This caused disability and death for thousands of local residents.
The Minamata Convention, once in force, will require party nations to:
•Reduce and where feasible eliminate the use and release of mercury from artisanal and small-scale gold mining.
•Control mercury air emissions from coal-fired power plants, coal-fired industrial boilers, certain non-ferrous metals production operations, waste incineration and cement production.
•Phase-out or take measures to reduce mercury use in certain products such as batteries, switches, lights, cosmetics, pesticides and measuring devices, and create initiatives to reduce the use of mercury in dental amalgam.
•Phase out or reduce the use of mercury in manufacturing processes such as chlor-alkali production, vinyl chloride monomer production, and acetaldehyde production.
•In addition, the Convention addresses the supply and trade of mercury; safer storage and disposal, and strategies to address contaminated sites.
•The Convention includes provisions for technical assistance, information exchange, public awareness, and research and monitoring. It also requires Parties to report on measures taken to implement certain provisions. The Convention will be periodically evaluated to assess its effectiveness at meeting its objective of protecting human health and the environment from mercury pollution.
The Minamata Convention will go into effect 90 days after it has been ratified by at least 50 nations, which is expected to take several years. To ratify it, the nations first must enact their own domestic laws. Currently, only 7 countries have ratified and
128 have signed. A total of 50 countries ratifying is needed for it to become international law. Only 7 have done that so far. We have a long way to go.