Nanotechnology Used To Study Environment

By Roland Piquepaille

Researchers from the Lawrence Berkeley Lab are using nanotechnology to learn how to clean up environmental contaminants like nuclear waste. They are also using supercomputers and state-of-the-art imaging to predict how quickly pollutants react with minerals in soils and aquifers. This article from the Daily Californian says they are studying kinetics, or rates, of reactions which occur at the earth's surface using a nanoscale approach. They started to look at the reactions that take place at the pore scale and plan to expand their scope from nanometers to meters in the months to come. This research has implications for transport of contaminants, especially of radioactive materials, but also for oil or ore recovery. Read more...

Here is the introduction of the Daily Californian article.

Nanotechnology, normally used for work with the crystal structures of silicone chips and pure oxides, is being used for something a little more dirty at the Lawrence Berkeley Lab, like learning how to clean up environmental contaminants like nuclear waste.

Researchers Glenn Waychunas and Carl Steefel are using techniques that allow them to study the environment at the nanoscale as part of the new Center for Environmental Kinetics Analysis (CEKA) program, based at Pennsylvania State University.

The goal of the program is to gain insight into the kinetics, or rates, of reactions that occur at the earth's surface using a nanoscale approach that better models what happens in the real world as opposed to in the lab.

The CEKA program uses a multidisciplinary approach and includes chemists, geochemists, biochemists, soil scientists and engineers.

[For their part,] Waychunas and Steefel are working on the reactions that take place on the pore scale, like the flow of water through the minerals in an aquifer.

"What has been left out is determining rates at the pore scale, we're measuring rates at different scales to see how biogeochemical and microbial reactions scale up," Steefel said.

Here, "Waychunas (left) and Steefel inspect a device used to grow and monitor nanocrystals of interest to environmental and earth scientists." (Credit: Berkeley Lab View).

What will be the impact of this program, which has received $6.7 million from the NSF?

This can have implications for transport of contaminants, especially of radioactive materials. Researchers seek to determine reaction rates to determine how long it would take for a plume of pollutant to spread through different mineral substrates.

The next scale is supercomputer modeling, according to Waychunas. "This will model chemical reactions and integrate fluid flow through pore structures, using more complicated fluids and soils. Then we'll apply them to real systems, like the Yucca Mountains, natural aquifers, oil recovery, ore recovery, and natural gas," Waychunas said.

For more information, you can read "Taking a Peek At Our Environmental Future," published by Berkeley Lab View, and from which I extracted the above photograph. Here are more details about Steefel's work.

Steefel, also a geochemist in the Earth Sciences Division, will also start small and then try to go big. First, he wants to gain a mechanistic understanding of the processes that control biogeochemical reaction rates in porous material by focusing on a single pore. In a common scenario, there may be a reactive mineral on one side of a pore and biofilm on the other side. How do they communicate? To answer this question, Steefel and several other scientists will conduct reactive flow experiments using single-pore microfluidic devices. They'll also monitor how fluid reacts with porous samples using imaging technology with a spatial resolution of about 30 nanometers, such as the Advanced Light Source's scanning transmission x-ray microscope (STXM). They will probably begin with a calcium carbonate mineral that has been studied extensively -- but never at the pore scale -- and observe the rate at which a slightly acidic solution reacts with the mineral as it flows through.

Next, this pore-by-pore data will be used to develop supercomputer-derived models that depict the rates of these reactions in a much larger sample of porous material.

Here is his conclusion.

"The idea of scaling kinetics is a frontier issue, but that's what this project is about," says Steefel. "If we develop a mechanistic understanding of reactive transport at several scales, then we can devise predictive models for bioremediation, chemical weathering, and carbon sequestration. And only through the convergence of modeling, supercomputers, synchrotron techniques, and advanced microfluidic reactors is this possible."

Sources: Francesca Hopkins, The Daily Californian, January 19, 2005; Dan Krotz, Berkeley Lab View, November 12, 2004; and various websites

Related stories can be found in the following categories.

• Biotechnology
  
• Chemistry
  
• Environment
  
• Nanotechnology