Sustainable Range Management of RDX and TNT
by Phytoremediation with Engineered Plants
Funding Agency: Department of Defense SERDP
Decades of military activity on live fire training ranges has resulted in severe contamination of land and groundwater by recalcitrant high explosives, in particular, TNT and RDX. TNT and its transformation products are highly toxic, but these tend to bind strongly to clay and organic matter in soil and are largely contained at the site of contamination; however, RDX is a major concern, because of its high mobility through soils and subsequent contamination of ground water. RDX contamination of firing ranges is now proving to be a significant threat to drinking water sources such as those close to the Massachusetts Military Reservation. RDX is not as toxic as TNT, but it still presents an immediate and future health problem to society. Currently, there are no cost effective processes to contain RDX or remediate large areas of contaminated vegetated land on training ranges.
We propose to engineer transgenic grasses to contain and degrade RDX in the root zone of explosives contaminated soil. To achieve this goal we will investigate the expression in plants of a novel RDX degrading cytochrome P450 gene xplA. This enzyme is known to degrade RDX to harmless metabolites. Since munitions often comprise both RDX and TNT, it will also be necessary to engineer resistance to TNT, as this explosive is highly toxic to plant systems.
This project will result in the development of a variety of grasses with unique abilities to detoxify and degrade TNT and RDX, respectively. These plants promise to provide a self-sustaining, inexpensive and environmentally friendly method of range restoration that can be used over large areas of land for the prevention of groundwater contamination from RDX dissolution arising from munitions used on training ranges. Considering the availability of many microbial and plant genes mediating detoxification systems and degradative pathways, the proposed strategy of engineering plants to remove explosives has the potential of providing an efficacious means to clean up land contaminated through military activities and to maintain low levels of RDX in training range groundwaters.
We envision transition in three stages: greenhouse studies with contaminated soil using the transgenic grasses in years three and four, controlled field trials commencing after completion of this project, full-scale implementation on an active training range with monitoring.
