HANOVER, N.H. (Aug. 29, 2017) -- Military live fire activities on training ranges can result in the contamination of land and groundwater by explosive residues, in particular explosive chemical compounds such as trinitrotoluene, commonly known as TNT, and the even more explosive cyclotrimethylenetrinitramine, or RDX, and their chemical by-products.
There are known threats of TNT residue to the environment and risks to groundwater by RDX contamination. Other contaminants, such as heavy metals, also remain in the soil long after training areas have been used. Unfortunately, no cost-effective method to contain or remediate large areas of contaminated land on military training ranges exists.
U.S. Army Cold Regions Research and Engineering Laboratory scientists are researching the use of innovative, cost effective methods to restore balance to environments exposed to contaminants resulting from the firing of munitions.
One such method is phytoremediation. Simply put, phytoremediation is using plants to clean up environmental harmful contaminants, which in this case are residues from munitions. Certain plants are effective as hyperaccumulators that concentrate and remove metals from the soil into their root zone. Other plants have been developed that metabolize and break down TNT and RDX residues into harmless components inside the plant tissue.
At CRREL, Agronomist Timothy Cary leads the phytoremediation research program where he and his team are cultivating thousands of modified switchgrass plants in the onsite greenhouse. The 4,500-square-foot greenhouse supports year-round research and allows staff members to control the environment – temperature, sunlight, moisture – while incorporating unique devices to measure growth and gas exchange.
The plants that are being grown specifically for phytoremediation are tested for their ability to extract munitions residues from soils in first the controlled greenhouse environment, then tested in exterior plots.
Currently, Cary has 2,700 switchgrass plant seedlings growing in plots on a training range that are exposed to the natural environment. These plots have known/measured residues concentration rates. Throughout the summer the soil, water and plant tissues are being routinely sampled to evaluate the plants contaminant uptake and metabolizing of residues.
"The grasses in the outdoor test plots had more rain this summer than they would have had inside the controlled greenhouse, but they seemed to have responded, so far, satisfactorily to these conditions,” said Cary. “We look forward to continuing the remediation experiments in these test plots.”
The grasses used in this experiment have been modified through partnerships with researchers from the University of York, York, England, and the University of Washington.
This technology has the potential to provide a self-sustaining, inexpensive and an environmentally friendly method of range restoration that can be used over large areas of land to prevent groundwater contamination and on newly developed munition components, as well as traditional munitions.
This research supports the Department of Defense’s mission for environmental stewardship and restoration of military training lands.