Several varieties of plants are being grown in an enclosed greenhouse near the test site. The plants' soil is tainted with varying levels of TNT so the researchers can study how efficiently the plants uptake the TNT.

"There is very little written in the scientific literature about plant uptake of explosive contaminants," says Sandia's Susan Bender. "We are conducting new studies to see if plants rooted in TNT-tainted soil will uptake the residues into their roots, stems, and flowers, and even incorporate them into their pollens."

If plants that readily accumulated the TNT could be identified, a suspected minefield could be seeded with those plants (by air) to maximize the bees' chances of finding the mines.

Inside the greenhouse a small colony of bumblebees has been established to measure how efficiently the bees carry TNT-tainted pollen and soil back to the hive.

"The greenhouse, plant uptake experiments, and control hives are designed to increase our chances of success when we begin testing the bees in the landmine field," says Sandia explosives chemist Phil Rodacy. "We'll compare the results we get in the controlled environments with the results we get in the field to see how well the bees are doing."

A HONEYBEE gathers food and materials for the hive. Download 300dpi JPEG image, 'BombBee.jpg', 2.1M (Media are welcome to download/publish this image with related news stories.)

The Montana team will use highly instrumented "honeybee condos," which automatically count the number of times bees fly in and out of the hive, to track the bees' flight activity.

Bromenshenk's team has shown that subtle changes in flight activity and other bee behaviors can signal that the bees are being exposed to environmental contaminants.

Pollen, dust, air, and other samples collected by the bees and brought to the hive will be analyzed for trace amounts of explosives. Sandia will examine the samples using highly sensitive chemical analysis tools to determine whether the bees can reliably indicate the presence of landmines in an area over time.

One goal of ongoing tests at Montana is to determine which explosives bees can smell and then train them to seek those chemicals. If bees can be trained to associate the odor of explosives (such as TNT) with food (sugar syrup, for instance), says Bromenshenk, the bees may spend more time near plants and surface soils contaminated with TNT, increasing the odds that they would bring back TNT residues from an area that contains buried mines.

Bromenshenk has demonstrated that by providing a new bee colony with feeders tainted with a marker chemical, then gradually moving the feeders farther from the hive and eventually removing them, bees can be trained to forage wherever they smell the chemical. If bees can be trained to seek TNT, the Montana team may attach small diodes onto the backs of several hundred TNT-trained bees. Then, using a handheld radar tracking device, they will chart where those bees go to determine whether they tend to forage near the locations of known landmines.

Countering the worst form of pollution on earth
The ultimate goal of the project, says Bender, is to determine whether buried mines are present in large areas by establishing beehives near the suspected mines, monitoring bees' flight activity, and analyzing hive samples.

"If this method works and it's reliable, you could foresee giving people the green light to re-enter or farm large areas based on bee sampling," she says.

DARPA's Controlled Biological Systems Program supports research of sentinel species (such as bees, wasps, caterpillars, and moths), biohybrids (robotic systems that make use of animal features), and robotic systems for detection of contaminants and other environmental variables.

"The beauty of this approach is that bees are indigenous to every climate on earth, and there are beekeepers everywhere," Bender says. "And you wouldn't need a million-dollar piece of equipment and extensive training to use it. The countries where landmines are a problem typically don't have those kinds of resources."