Plants Perform "Green Clean" of Toxic Sites

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The site's plantings are attracting insects, birds, and other wildlife while aggressively accelerating the natural degradation process of toxins.

"If left undisturbed, it would take decades or centuries for these contaminants to naturally decompose," Rugh said. "What our research is indicating is that we can achieve at least 50 percent degradation in three to five years—and that's at the very least. Some [species] seem to be approaching 70 percent in just three growing seasons."

Other companies, including British Petroleum, Chevron, and DaimlerChrysler, have similar projects.

Explosive Cleanup

Sponsors of phytoremediation research include the U.S. Army and the U.S. Department of Defense. Programs there have tapped plants to help with the thorny problem of ordnance disposal.

Firing and training ranges are contaminated with the toxic remains of partially exploded rounds. The rounds include a chemical commonly known as RDX.

Mike Reynolds serves with the Army's Engineer Research and Development Center's Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire. He said his group has recently begun research linked to solving the problem.

"On live-fire ranges or in their bordering areas, you have unexploded ordnance, which can be dangerous," Reynolds said. "There are just not a lot of [cleanup] alternatives."

Lee Newman, a researcher at the University of South Carolina's Arnold School of Public Health, is collaborating on the project. She notes that while explosive residues like TNT have been successfully remediated in the past, RDX is proving a bit tougher.

"One of the big concerns with some of the more recalcitrant compounds [would be] if the plants start accumulating high levels of explosives but don't break them down," Newman said.

The plants would "never become explosive," Newman said. "But they could become toxic and die. And [RDX] may go right back into the ground again."

"In a sense, what we propose to do with RDX in surface soils is tie RDX molecules permanently into soil organic matter, and they won't really exist as RDX anymore," Reynolds explained.

While many phytoremediation applications show promise, the technique faces an uncertain future as an alternative and inexpensive entrant in the very profitable field of contaminant remediation.

"People love the idea of using something natural to clean the environment rather than excavating and hauling things away," Newman said. "But as a field we need to convince regulators that what we're doing is based on good science and that we can do something effective," she explained.

"Some very progressive firms are now offering phytoremediation as an option, but it's still not one of the main options," she added. "If [companies] use a new technology and it doesn't work, they are going to be in a lot of trouble and also a money-losing situation."

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