November 27, 1998 Volume 6, Number 7

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U of S graduate develops plants with huge potential to de-toxify contaminated sites

Steven Siciliano, PhD. Cleaning up after thousands of detonated explosives.

A University of Saskatchewan graduate is helping the Canadian military clean up its act.

No, it's got nothing to do with another armed forces scandal. The dirt Steven Siciliano is cleaning up is of an entirely different kind.

A native of Thunder Bay, Siciliano, 27, recently completed his PhD in toxicology at the U of S. For the past few years, he's been studying phytoremediation, the use of plants and bacteria to clean up contaminated sites.

In joining the Montreal-based National Biotechnical Research Institute for a two-year fellowship, he'll be putting his research into practice at an abandoned military firing range just outside that city. The site is contaminated with energetics, the residual byproducts of explosives, such as TNT and RDX.

"When something explodes, only 99% of the explosive is actually used up," he explains. "When you've got thousands and thousands of explosives detonated in a concentrated area, the soil becomes contaminated. The problem is how to clean it up."

The usual answer is to take extreme measures, such as digging up the soil and incinerating it at ultra-high heat, or washing it with detergents. Either way it's an extremely expensive proposition. And sometimes the solutions create problems of their own.

A better way

Siciliano is among a growing number of scientists who feel there's a better way.

"It's pretty well known that different plants can help clean up contaminated soil," he says. "What often happens, though, is that the soil is too toxic and the plants die. Or the plants will grow in the soil, but they won't clean it up.

"What my doctorate is largely about is how can we use bacteria to stimulate the plants to degrade toxic compounds."

In his research, Siciliano found that several different types of bacteria interact with plants to enhance their ability to clean up soil.

He then set out to show how this occurs.

In a breakthrough, he discovered that some types of bacteria can stimulate a plant to produce a previously unknown enzyme, which in turn increases the plant's ability to degrade toxic matter. Another came when he discovered that the bacteria can actually alter the ecology of the soil just below the surface, where plants take root.

His efforts earned him a University of Saskatchewan graduate thesis award.

"What's important isn't that we put the plants and bacteria together and got enhanced degradation. That's interesting, but the most important thing is that the mechanisms by which they do this had never before been described."

In describing these mechanisms, Siciliano feels he's laid the groundwork for biotechnologists to create "superplants" that can degrade toxic compounds even more effectively.

He believes wide-scale use of bacteria and plants to decontaminate soil is only a year or two away. He notes that some companies are already using similar technology to clean up their sites.

Cleaning up 'brown field' sites

Although phytoremediation can be used for many types of soil contamination, Siciliano said its greatest potential is for cleaning up "brown field" sites - industrial areas with lower, but still dangerous, levels of contamination.

"If you have a factory downtown and it's closed, there's going to be a lot of residual contamination on the site. It's still quite dangerous. You can't build on it and you can't sell it because it's contaminated. And you can't remediate it properly because most schemes require intensive machinery, which poses dangers of its own."

He says it's been estimated that there are billions of dollars of real estate across North America in that condition.

"In using plants downtown, it's safer, it looks good, and in five years, the site's clean. It's cheap, too. The kind of technology that we've developed is approximately 10 to 100 times cheaper than conventional remediation methods. It's just slower."

Plants and bacteria could also be used to clean up contaminated mine sites, Siciliano says.

Another possibility is to use phytoremediation as a preventative measure, by growing the appropriate plants around areas susceptible to contamination.

In the event of a toxic spill, the plants would already be in place.

"The thing I'm most proud of about this work is that it isn't limited to a single use. We've developed a screening method so that, if you want to clean up a site, you know what to go through. You might have to use a different type of bacteria or a different type of plant, but you'll know how to find them. That's a big challenge in itself."

- Keith Solomon

On Campus News is published by the Office of Communications, University of Saskatchewan.
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