Featured Research

from universities, journals, and other organizations

Waterborne Carbon Increases Threat Of Environmental Mercury

Date:
December 11, 2007
Source:
University of Wisconsin-Madison
Summary:
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 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.


Story Source:

The above story is based on materials provided by University of Wisconsin-Madison. Note: Materials may be edited for content and length.


Cite This Page:

University of Wisconsin-Madison. "Waterborne Carbon Increases Threat Of Environmental Mercury." ScienceDaily. ScienceDaily, 11 December 2007. <www.sciencedaily.com/releases/2007/12/071210162850.htm>.
University of Wisconsin-Madison. (2007, December 11). Waterborne Carbon Increases Threat Of Environmental Mercury. ScienceDaily. Retrieved October 2, 2014 from www.sciencedaily.com/releases/2007/12/071210162850.htm
University of Wisconsin-Madison. "Waterborne Carbon Increases Threat Of Environmental Mercury." ScienceDaily. www.sciencedaily.com/releases/2007/12/071210162850.htm (accessed October 2, 2014).

Share This



More Earth & Climate News

Thursday, October 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: 12 More Bodies Found on Japan Volcano

Raw: 12 More Bodies Found on Japan Volcano

AP (Oct. 1, 2014) — A dozen more bodies were found Wednesday as Japanese rescuers resumed efforts to find survivors and retrieve bodies of those trapped by Mount Ontake's eruption. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Cultural Learning In Wild Chimps Observed For The First Time

Cultural Learning In Wild Chimps Observed For The First Time

Newsy (Oct. 1, 2014) — Cultural transmission — the passing of knowledge from one animal to another — has been caught on camera with chimps teaching other chimps. Video provided by Newsy
Powered by NewsLook.com
Raw: Trapped Scientist Rescued from Cave in Peru

Raw: Trapped Scientist Rescued from Cave in Peru

AP (Oct. 1, 2014) — A Spanish scientist, who spent 12 days trapped about 1300 feet underground in a cave in Peru's remote Amazon region, was rescued on Tuesday. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Media, Industry Groups React To Calif. Plastic Bag Ban

Media, Industry Groups React To Calif. Plastic Bag Ban

Newsy (Sep. 30, 2014) — California is the first state in the country to ban single-use plastic bags in grocery, liquor and convenience stores. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins