Ed Note: The National Ground Water Association held its Water Expo and Annual Meeting at the Las Vegas Convention Center Dec. 2 to 5, 2008. Here is a report from the director of NGWA from one of the sessions.

Nanotechnology, the science of matter on the atomic scale, offers promise for making water clean and safe for the world's citizens, but care also should be taken to study possible unwanted environmental side effects, says researcher Vicki Colvin, Ph.D., of Rice University.

A "nanoparticle" is 1 to 100 nanometers in diameter – a nanometer being one billionth of a meter in length. While some nanoparticles occur naturally, nanotechnology has resulted in the development of nanoparticles that have very specific properties. In the context of remediating contaminated water, two such properties are:

• Sequestration, where the nanoparticle locks up a contaminant to prevent harm, and
• Reaction, where a nanoparticle reacts with another substance to render it harmless.

"The real benefits to ground water are all related to the surface area of nanoparticles. A gram of nanoparticle material might have the surface area of a football field. Nanoparticles have huge surface areas for reaction and sequestrations," said Colvin in her presentation, Nanotechnology in the Environment: Clean Water from Small Materials.

Another advantage to nanoparticles is that they are so small they do not settle in water but are a part of the water flow, thus facilitating their ability to react with or sequester contaminants downstream. Colvin said the ability to design and produce nanoparticles to do very specific things is so good that "you can make a nano-anything these days."

Potential environmental dangers

"The field of nanotechnology is projected to be a $1 trillion business in the next five to 10 years. They are in many consumer products from deodorants to sunscreen and car tires to golf clubs, crossing many industries," said Colvin. "The question is, do they find their way into aquifers and are they going to be part of drinking water systems?"

The same qualities that make nanoparticles so useful and effective can also present dangers to the environment. "Small amounts in mass could be huge amounts in surface area so that you could moderate and change environmental processes drastically," she said.

Among the potential issues:

• Nanoparticles could facilitate the transport of contaminants
• The reactive properties of some nanoparticles could create unwanted byproducts
• At its atomic-scale size, nanoparticles could invade and affect biological organisms in ways larger particles cannot
• They could persist in the environment for a long time.

"For all those reasons, we want to be cautious with them. The science of application of nanoparticles has been around for 10 years or longer. What's newer and less evolved is the science of how to deal with the unwanted consequences," said Colvin. This evolving science is complicated by the fact that it can be difficult to differentiate between naturally occurring and manmade nanoparticles.

"My take-home message is that nanoparticles are already out there in nature. People already are dealing with them and don't know it," she said. "And, we don't want to make the same mistakes as in the past by introducing technologies that create problems." PE