Phytoextraction Of RDX-Contaminated Aqueous Media By Vetiver Grass (Chrysopogon zizanioides).

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a major component of composition B (Comp B), a commonly used military formulation composed of toxic explosive compounds. Persistence of this nitramine explosive in environment, toxicity to humans, and bioaccumulation up the food chain are the major driving forces behind on-going remediation studies. Phytoremediation is a is a cost-effective and environment-friendly clean up alternative for RDX contaminated soils as compared to more common practices like excavation followed by incineration or landfilling and burning of the surface soil. Our previous studies have established the effectiveness of vetiver, a high biomass, fast growing perennial grass, in removing other military contaminants like TNT and lead from both soil and aqueous media. The current study investigated the phytoextraction potential of vetiver grass for RDX from the contaminated aqueous media. A greenhouse hydroponic experiment was conducted over 40 days with vetiver grass and four initial concentrations of RDX (0, 0.25, 1, and 2 mg L^-1) to determine the i) removal of RDX from solution, ii) plant uptake, and iii) root to shoot translocation of RDX by vetiver grass. During the study period, vetiver grass did not exhibit any significant (p<0.05) phytotoxic effect at any of the RDX treatments. In presence of vetiver grass, RDX was completely removed from solution within 20 days. Initial RDX concentration significantly (p>0.05) influenced the uptake and root to shoot translocation of RDX in vetiver grass.  Vetiver grass was capable of translocating RDX from root to shoot (average translocation factor = 8.93) very efficiency. The current data is highly encouraging, and ongoing studies in our laboratory aim to identify the unknown plant metabolites, detected in the plant tissues, which suggest potential phytodegradation of RDX.