Researchers at the University of Wisconsin-Madison have found that the presence of dissolved organic material increases the biological risk of aqueous mercury and may even serve as an environmental mercury source.
Mercury is present throughout the environment in small quantities in rocks and in watery environments, including lakes, wetlands and oceans. It accumulates in fish living in mercury-contaminated waters, posing a health risk to animals and humans who eat the tainted fish.
The greatest threat comes from a form called methylmercury, which is more easily taken up by living tissues. The methylation process, therefore, is key to understanding the potential danger posed by environmental mercury, says UW-Madison geomicrobiologist John Moreau.
He presented his research findings at the American Geophysical Union meeting in San Francisco today (Dec. 10).
Environmental mercury is predominantly methylated by naturally occurring bacteria known as sulfate-reducing bacteria. These bacteria - Moreau calls them "little methylmercury factories" - absorb inorganic mercury from the water, methylate it and spit methylmercury back out into the environment.
"The bacteria take mercury from a form that is less toxic to humans and turn it into a form that is much more toxic," Moreau says. "[Methylation] increases mercury's toxicity by essentially putting it on a fast train into your tissue - it increases its mobility."
Many previous studies have focused on the chemical interactions between mercury and sulfur, which is known to bind to inorganic mercury and may regulate how well the bacteria can absorb it. However, scientists do not understand the factors that control the methylation process itself.
"Those studies have related methylation potential to geochemical variables," Moreau says. "We would like to take a bacterium that we know methylates mercury very efficiently and let it tell us what it can methylate and what it can't, under given conditions."
Moreau and colleagues at the U.S. Geological Survey, UW-Madison, the University of Colorado and Chapman University chose to look at the role of dissolved organic carbon (DOC), a richly colored brew created as plants and other organic materials decay into a soup of proteins, acids and other compounds. DOC can tint wetlands and streams shades of yellow to dark brown.
DOC has noticeable effects on bacterial mercury processing. "They seem to methylate mercury better with DOC present," says Moreau.
In the current studies, the scientists looked at the effects of DOC samples collected from two different organic-rich environments, a section of the Suwannee River and Florida's Everglades.
"We found that different DOCs have different positive effects on methylation - they both seem to promote mercury methylation, but to different degrees," Moreau explains.
Because DOC is virtually ubiquitous in aqueous environments, its effect on mercury processing may be an important factor in determining mercury bioavailability.
Moreau and his colleagues are now working to understand how DOC promotes methylation. One possibility is that DOC acts indirectly by increasing bacterial growth, while another is that DOC may directly interact with the mercury itself to boost its ability to enter bacteria.
Although mercury already in the environment is there to stay, Moreau says an understanding of what regulates mercury toxicity is critical for developing ecosystem-level management strategies.
"Strategies to deal with methylmercury production [should] lead to hopefully more efficient ways to reduce human consumption of methylmercury and lead to less potential human health problems," he says.
John Moreau | EurekAlert!
NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center
Steep rise of the Bernese Alps
24.03.2017 | Universität Bern
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy