Study shows three times more mercury in upper ocean since Industrial Revolution

A press release from the Woods Hole Oceanographic Institute: Although the days of odd behavior among hat makers are a thing of the past, the dangers mercury poses to humans and the environment persist today.

Mercury is a naturally occurring element as well as a by-product of such distinctly human enterprises as burning coal and making cement. Estimates of "bioavailable" mercury—forms of the element that can be taken up by animals and humans—play an important role in everything from drafting an international treaty designed to protect humans and the environment from mercu
ry emissions, to establishing public policies behind warnings about seafood consumption.

Yet surprisingly little is known about how much mercury in the environment is the result of human activity, or even how much bioavailable mercury exists in the global ocean. Until now.

A new paper by a group that includes researchers from the Woods Hole Oceanographic Institution (WHOI), Wright State University, Observatoire Midi-Pyréneés in France, and the Royal Netherlands Institute for Sea Research appears in this week's edition of the journal Nature and provides the first direct calculation of mercury in the global ocean from pollution based on data obtained from 12 sampling cruises over the past 8 years. The work, which was funded by the U.S. National Science Foundation and the European Research Council and led by WHOI marine chemist Carl Lamborg, also provides a look at the global distribution of mercury in the marine environment.

"It would seem that, if we want to regulate the mercury emissions into the environment and in the food we eat, then we should first know how much is there and how much human activity is adding every year," said Lamborg, who has been studying mercury for 24 years. "At the moment, however, there is no way to look at a water sample and tell the difference between mercury that came from pollution and mercury that came from natural sources. Now we have a way to at least separate the bulk contributions of natural and human sources over time."...

Bohr model of mercury, author unknown, Wikimedia Commons, under the Creative Commons 2.0 license

A warning of mercury's legacy in the environment

Harvard University News: Environmental researchers at Harvard University have published evidence that significant reductions in mercury emissions will be necessary just to stabilize current levels of the toxic element in the environment. So much mercury persists in surface reservoirs (soil, air, and water) from past pollution, going back thousands of years, that it will continue to persist in the ocean and accumulate in fish for decades to centuries, they report.

"It's easier said than done, but we're advocating for aggressive reductions, and sooner rather than later," says Helen Amos, a Ph.D. candidate in Earth and Planetary Sciences at the Harvard Graduate School of Arts and Sciences and lead author of the study, published in the journal Global Biogeochemical Cycles.

Amos is a member of the Atmospheric Chemistry Modeling Group at the Harvard School of Engineering and Applied Sciences (SEAS), where researchers have been collecting historical data on mercury emissions as far back as 2000 BC and building new environmental models of mercury cycling that capture the interactions between the atmosphere, oceans, and land.

Their model reveals that most of the mercury emitted to the environment ends up in the ocean within a few decades and remains there for centuries to millennia. These days, emissions are mainly from coal-fired power plants and artisanal gold mining. Thrown into the air, rained down onto lakes, absorbed into the soil, or carried by rivers, mercury eventually finds its way to the sea. In aquatic ecosystems, microbes convert it to methylmercury, the organic compound that accumulates in fish, finds its way to our dinner plates, and has been associated with neurological and cardiovascular damage.

..."Today, more than half of mercury emissions come from Asia, but historically the U.S. and Europe were major emitters," says second senior author Daniel J. Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at Harvard SEAS and Professor of Earth and Planetary Sciences. "We find that half of mercury pollution in the present surface ocean comes from emissions prior to 1950, and as a result the contribution from the U.S. and Europe is comparable to that from Asia."...

This illustration shows how quickly a drop of mercury released into the atmosphere (top row), soil (middle), or ocean (bottom) finds its way to the soil (green), ocean (blue), or atmosphere (yellow), over time (left to right). It can take hundreds of years for the mercury to be locked away in the deep ocean or minerals. (Image courtesy of Helen Amos.)

UN clinches global deal on cutting mercury emissions

Tom Miles and Emma Farge in Planet Ark: More than 140 countries have agreed on the first global treaty to cut mercury pollution through a blacklist of household items and new controls on power plants and small-scale mines, the United Nations said on Saturday. The legally-binding agreement aims to phase out many products that use the toxic liquid metal such as batteries, thermometers and some fluorescent lamps, through banning global import and exports by 2020.

The treaty will require countries with coal-fired power plants such as India and China to install filters and scrubbers on new plants and to commit to reducing emissions from existing operations to prevent mercury from coal reaching the atmosphere.

...The deal also includes measures to reduce mercury use in small-scale gold mining, although stopped short of an all-out ban. Gold prices near $1,700 a metric ton have spurred the use of mercury as a catalyst to separate gold from its ore.

...The Minamata Convention on Mercury - named after the Japanese city where people were poisoned in the mid-20th century from industrial discharges of mercury - needs ratification from 50 countries and is expected to be formalized later this year....

Thinner sea ice may lead to more mercury contamination

Laura Snider in the Boulder Daily Camera: The replacement of thicker sea ice that formed over multiple years in the Arctic with a thinner layer of ice that formed during the last winter is changing the air chemistry above the ice and likely increasing the amount of mercury contamination in the region, according to a new study led by a Boulder scientist.

Thinner sea ice -- which is riddled in the spring with cracks and fissures -- allows elements known as halogens to escape from the briny seawater onto the surface of the ice. There, the halogens, especially bromine, chemically react to scrub ozone from the atmosphere near the surface of the ice. Scientists also know that the same chemical reaction that eliminates the ozone transforms stable elemental mercury in the atmosphere into a more reactive form of mercury, which can then be deposited on snow and ice as well as directly into the ocean.

Scientists at the National Oceanic and Atmospheric Administration in Boulder have now measured the resulting drop in ozone from an observation center in Barrow, Alaska, where researchers have been making ozone measurements for nearly 40 years. The scientists also measured mercury, said Samuel Oltmans, lead author of the study published in the Journal of Geophysical Research, but because a long-term record of mercury measurements does not exist, the scientists don't have a baseline to compare the new measurements to.

Still, the researchers believe that it's likely that the amount of reactive mercury has increased as ozone has decreased.... Researchers are concerned that an increased amount of reactive mercury settling out on the snow and ice in the Arctic will lead to an increase in mercury contamination in the ocean as the snow and ice melts....

Iceberg west of Ilulissat inlet, Greenland, shot by Ute Wollf (Rodebay), Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

NASA finds sea ice driving arctic air pollutants

NASA: Drastic reductions in Arctic sea ice in the last decade may be intensifying the chemical release of bromine into the atmosphere, resulting in ground-level ozone depletion and the deposit of toxic mercury in the Arctic, according to a new NASA-led study.

The connection between changes in the Arctic Ocean's ice cover and bromine chemical processes is determined by the interaction between the salt in sea ice, frigid temperatures and sunlight. When these mix, the salty ice releases bromine into the air and starts a cascade of chemical reactions called a "bromine explosion." These reactions rapidly create more molecules of bromine monoxide in the atmosphere. Bromine then reacts with a gaseous form of mercury, turning it into a pollutant that falls to Earth's surface.

Bromine also can remove ozone from the lowest layer of the atmosphere, the troposphere. Despite ozone's beneficial role blocking harmful radiation in the stratosphere, ozone is a pollutant in the ground-level troposphere.

A team from the United States, Canada, Germany, and the United Kingdom, led by Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., produced the study, which has been accepted for publication in the Journal of Geophysical Research- Atmospheres. The team combined data from six NASA, European Space Agency and Canadian Space Agency satellites; field observations and a model of how air moves in the atmosphere to link Arctic sea ice changes to bromine explosions over the Beaufort Sea, extending to the Amundsen Gulf in the Canadian Arctic.

"Shrinking summer sea ice has drawn much attention to exploiting Arctic resources and improving maritime trading routes," Nghiem said. "But the change in sea ice composition also has impacts on the environment. Changing conditions in the Arctic might increase bromine explosions in the future."...

Bromine explosion on March 13, 2008 across the western Northwest Territories in Canada looking toward the Mackenzie Mountains at the horizon, which prevented the bromine from crossing over into Alaska. The bromine explosion is depicted in the foreground by the red-orange areas, while the green shades at high altitudes on the mountains represent areas where there was no increase in bromine. Image credit: NASA/JPL-Caltech/University of Bremen