Earth Science News  





. Waterborne Carbon Increases Threat Of Environmental Mercury

Environmental mercury is predominantly methylated by naturally occurring bacteria known as sulfate-reducing bacteria.
by Staff Writers
Madison WI (SPX) Dec 11, 2007
Mercury is a potent neurotoxin and a worrisome environmental contaminant, but the severity of its threat appears to depend on what else is in the water. 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.

Community
Email This Article
Comment On This Article

Related Links
University of Wisconsin-Madison
Our Polluted World and Cleaning It Up




Tempur-Pedic Mattress Comparison

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News
SKorea's worst oil spill spreads along coast
Taean, South Korea (AFP) Dec 10, 2007
South Korea's worst-ever oil spill spread along a pristine coastal area Monday, fouling beaches and marine farms, as the government faced accusations it acted too slowly to limit the disaster.

.
Get Our Free Newsletters Via Email
  



  • Flood damage in northwest US may run into billions: governor
  • Massive landslide threatening homes in central Austria: authorities
  • More deaths as storms exit the Philippines
  • NORTHCOM Experience Lends Lessons To Bangladesh Relief

  • World's Protected Areas Threatened By Climate Change
  • Climate change could lead to conflict, instability: UN report
  • Nitrous Oxide From Ocean Microbes
  • US, poor nations won't pledge binding cuts in Bali: UN

  • Outside View: Russia's new sats -- Part 2
  • Use Space Technology And IT For Rural Development
  • China, Brazil give Africa free satellite land images
  • Ministerial Summit On Global Earth Observation System Of Systems

  • Climate survey pooh-poohs biofuels
  • Wind turbines to power every British home by 2020: minister
  • Methane From Microbes: A Fuel For The Future
  • Al-Qaeda could spark US economic crisis: McCain

  • New China bird flu case raises human-to-human fear
  • China says no bird flu outbreak after father-son cases
  • Most Ancient Case Of Tuberculosis Found In 500,000-Year-Old Human; Points To Modern Health Issues
  • Scientists Strike Blow In Superbugs Struggle

  • Threatened Birds May Be Rarer Than Geographic Range Maps Suggest
  • Massive Dinosaur Discovered In Antarctica Sheds Light On Life, Distribution Of Sauropodomorphs
  • World's Most Endangered Gorilla Fights Back
  • Climate Change Will Significantly Increase Impending Bird Extinctions

  • Waterborne Carbon Increases Threat Of Environmental Mercury
  • SKorea's worst oil spill spreads along coast
  • A lone voice in China wins friends for environmental campaign
  • China reports progress on cutting pollution, but not enough

  • Scientists Develop New Measure Of Socioclimactic Risk
  • Like Humans, Monkey See, Monkey Plan, Monkey Do
  • Subliminal Smells Bias Perception About A Person's Likeability
  • Brain Systems Become Less Coordinated With Age, Even In The Absence Of Disease

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement