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NMSU professor studies using bacteria to detect explosives

Research by a New Mexico State University professor may contribute to the development of a way to detect land mines more safely, using remote sensing laser technology.

New Mexico State University environmental microbiologist Geoffrey Smith stands with the equipment he is using in an attempt to isolate gases produced when bacteria break down TNT. Smith is working with LaSen Inc. of Las Cruces to produce laser equipment capable of detecting land mines from a distance. (NMSU photo by Meghann Dallin)

y Smith, an environmental microbiologist at New Mexico State, is testing whether lasers can detect chemical traces left when plants, bacteria or fungi break down TNT and other explosives. If so, lasers may be able to detect anti-personnel mines left over from military conflicts throughout the world, he said.

"Authorities may know land mines have been left in an area, but the location of the mines is either unknown or has been forgotten. In some cases, it's years later and the TNT has been metabolized," he said. "If this approach proves successful, we'll have a method to remotely sense the locations without putting people on the ground," he said.

Smith said many researchers have documented the ability of plants, bacteria and fungi to break down explosives and much of that work has been done in New Mexico at New Mexico State or at Los Alamos National Laboratory. His own work goes a step farther by attempting to show a laser can detect the by-products of the break down.

The organisms can break down TNT, RDX and HMX -- the explosives most commonly used in military ordnance -- because the explosives are organic compounds, Smith explained. For example, TNT is an abbreviation for "trinitrotoluene." One group of enzymes in the bacterium Pseudomonas aeruginosa reduces the nitrogen to amino groups and another group breaks the toluene carbon ring in the compound, he said.

The byproducts of the breakdown may produce gases in the soil. Eventually, the project's developers hope to identify the byproducts by passing a laser through the rising gases. By detecting the gases, searchers would also discover the location of the explosives, he said.

But first, Smith must do a number of preliminary experiments, he added.

"We're doing a chemical analysis of the gases using a gas chromatograph linked to a mass spectrometer. Once we know which gases are produced, we can examine the potential for using the laser," he said.

"I'm actually doing this research under a subcontract with LaSen Inc. of Las Cruces, which has a contract with the U.S. Defense Threat Reduction Agency to develop a laser technology which can be mounted on helicopters or unmanned aerial vehicles," he said.

Allen Geiger, a co-owner of LaSen Inc., said his company has been using lasers to detect chemicals since 1989, when it began working with Phillips Petroleum to explore for new oil fields. In the early '90s, the laser equipment required for the search weighed approximately four tons and had to be carried on a truck. Today the equipment weighs about 90 pounds, light enough to be mounted on a helicopter or unmanned aerial vehicle, he said.

LaSen Inc. also uses the laser technology to look for leaks in natural gas pipelines, to survey the extent of underground fuel tank leaks and to look for the locations of illegal solid waste dumping, Geiger said.

"A laser produces different wave lengths of light, some of which are absorbed by one chemical and some by others. If we know an organism produces a particular chemical when it metabolizes an explosive we can tune the laser to look for that particular chemical," he said.

Geiger said it is more difficult to look for the explosives themselves, because a laser can't "see" through the ground. The explosives are usually buried; they tend not to evaporate and are usually present in low concentrations. Microorganisms and plants, on the other hand, continue to metabolize the chemicals and produce byproducts in ever greater concentrations, he explained.

Smith said he bases his research on the work of a New Mexico State master's degree student and two New Mexico State doctoral students, who studied the effectiveness of bacteria and some higher plants in breaking down explosives in the ground. During work on his 1994 master's thesis, Marc Alvarez discovered the effectiveness of Pseudomonis aeruginosa in breaking down TNT. Saeed Shojaee's 1994 doctoral dissertation dealt with the ability of higher plants to degrade explosives; while Mary Lucero's 1997 doctoral dissertation dealt with the ability of the plant Datura innoxia to degrade explosives.

Photo is available at http://kiernan.nmsu.edu/newsphoto/Smith_bio.jpg.
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