Certain seaweeds can efficiently take up TNT in coastal areas, providing a new twist to phytoremediation--the practice of using plants to remove pollutants from the environment. The finding was reported last week at the American Association for the Advancement of Science annual meeting in Washington, D.C.
Some coastal training ranges may contain TNT from unexploded munitions, said Linda Chrisey, program officer for Environmental & Marine Biotechnology at the Office of Naval Research (ONR).
Seaweeds are excellent remediators, said Greg Rorrer, a chemical engineering professor at Oregon State University (OSU). He found that three types of seaweed actively remove TNT from the water in laboratory models. Red tropical algae take up 100% of 1.0 mg per L TNT in 72 hours. Red tropical, as well as green and red algae from temperate regions, take up TNT five to 10 times faster than other aquatic plants.
The seaweeds also metabolize TNT. Rorrer and graduate student Octavio Cruz-Uribe, along with Donald P. Cheney at Northeastern University, have shown that a nitroreductase within the algal cells reduces one of TNT's nitro groups to an amine. About 20% of the aminodinitrotoluene product is then released back into the water, and the rest is metabolized further, possibly to sugar conjugates, which are then sequestered in cell vacuoles.
What effect TNT might have on the coastal environment is unclear, Chrisey said. Nevertheless, ONR is keen to find ways to remove it and has funded the TNT research at OSU.
"It's very powerful to take a pollutant and convert it into something that is benign," Chrisey said.
Rorrer said he is now investigating how well seaweeds take up other marine pollutants, such as polyaromatic hydrocarbons.