Small science may clean a big problem

They're scattered all around the United States, more than 1,200 of them, waiting for cleanup. Some are old military bases or abandoned factories. Others are gas stations with leaky underground tanks. And they're only the beginning of a long, arduous task.

Over the next 30 years, the US may have to clean up as many as 350,000 Superfund sites at a cost of up to $250 billion, according to the US Environmental Protection Agency.

How will taxpayers pay for that?

One solution is to find cheaper cleanup technologies. One of the most promising innovations right now involves microscopic iron particles. At least four teams of researchers are using these "nanoparticles" to attack some of the most vexing underground pollutants, including chromium-6, the groundwater pollutant made famous in the movie "Erin Brockovich."

If these nanotechnologies prove successful, they could reduce cleanup costs at selected Superfund sites by 75 percent, researchers suggest, perhaps saving billions of dollars.

"Using iron nanoparticles is one of the hottest new technologies to emerge in recent years," says Paul Tratnyek, an environmental chemist at Oregon Health & Science University and one of several researchers working on the technology.

Iron's contaminant-removal power arises from the fact that it rusts. "When it does so in the presence of groundwater contaminants, it can convert them into less toxic or nontoxic materials," says Dr. Wei-xian Zhang, an engineering professor at Lehigh University in Bethlehem, Pa.

The nanoparticles are particularly useful because of their size - a single human hair is 500 to 5,000 times as wide. At that scale, they can move through microscopic flow channels in soil and rock, reaching and destroying groundwater pollutants that larger particles cannot.

"Developing new technologies capable of locating and effectively treating areas contaminated with subsurface pollutants is difficult," says Greg Lowry, an engineering professor at Carnegie Mellon University in Pittsburgh. "This is because it is often difficult to locate the exact site of contamination because records are poor for many old waste sites and the primary contamination sources, such as storage tanks, were removed many years ago.

"Some of these contaminants move deep underground, and predicting their movement is difficult. So there are few reliable technologies to treat these sites," Dr. Lowry adds.

Working with researchers at Pacific Northwest National Laboratory and the University of Minnesota, Dr. Tratnyek has found that iron nanoparticles can effectively destroy carbon tetrachloride, a toxic organic chemical once widely used in dry cleaning and in degreasers. Its widespread production and use have contaminated soil and groundwater at many sites.

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