Iron Minerals Play Protective Role
Despite living in waters with the highest known marine concentration of naturally occurring arsenic found anywhere in the world, fish, clams and coral in waters near Papua New Guinea apparently are suffering no ill effects, according to a research report appearing this month in the journal Environmental Science & Technology. Iron minerals in the sediment appear to play a role in protecting marine life in this hostile environment.
Scientists believe the findings could eventually help in developing new methods that use natural products to treat arsenic-tainted waste generated by people. Extremely toxic, arsenic is one of the most difficult waste contaminants to remove.
The research, conducted by scientists from the University of Ottawa and the Geological Survey of Canada, appears in the May 1 issue of the peer-reviewed science journal, published by the American Chemical Society, the world's largest scientific society. The article was initially published on the journal's Web site on March 11.
Examining hydrothermal vents in the sea floor of Tutum Bay, adjacent to tiny Ambitle Island along the coast of Papua New Guinea in the Pacific Ocean just north of Australia, the researchers found boiling fluids with "extremely high arsenic concentrations" discharging from the vents into the water with the force of a fire hose.
The measured arsenic levels were more than 400 times that of the trace amounts of arsenic normally found in seawater, according to the University of Ottawa's Thomas Pichler, Ph.D., lead author of the study. Capable of causing neurological damage at such elevated levels, the arsenic in Tutum Bay is "the highest arsenic concentration reported from any marine setting, including black smoker vents from midocean ridges," he says.
In spite of the extreme concentration, "the skeletons of corals and the shells of clams do not show elevated concentrations of arsenic when compared to specimens collected from outside Tutum Bay," says Pichler.
"Two mechanisms seem to efficiently control and buffer the arsenic concentration," according to Pichler. "One is the dilution by seawater and the other is the incorporation of arsenic in iron minerals that precipitate when the hydrothermal fluids mix with ambient seawater." Iron minerals were found on the sea floor throughout the area where the research was done but they were most abundant near the vent openings, he notes.
The arsenic is captured and held by the iron minerals, preventing it from getting into the marine organisms. The minerals eventually form a bright orange layer that coats the lava and dead coral near the vents.
"Tutum Bay provides researchers with an exceptional opportunity to study a system in which natural pollution - the release of arsenic - is cleaned by a natural process," points out Pichler. "Understanding the process will provide us with invaluable information of how to treat anthropogenic systems."
A nonprofit organization with a membership of nearly 159,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio. (http://www.acs.org)
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