- Program Areas
- Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Climate Change
- Weapons Systems and Platforms
Fate of Plant Tissue Associated RDX in Surface Soil
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), an explosive used in a variety of munitions and currently found in soils at training ranges, is a contaminant of concern for the Department of Defense (DoD). Low-order and incomplete detonation has resulted in the surface distribution of RDX that is both heterogeneous and widely dispersed. RDX leaching from contaminated surface soils on ranges has been implicated in groundwater contamination. Due to the need for continued training and the hazard of unknown unexploded ordnance on ranges, few remediation strategies are considered safe and applicable to remediate RDX contamination. Two low-cost approaches, natural attenuation and phytoremediation, are increasingly viewed as acceptable treatment technologies; however, a critical concern is the permanence of the remediation. Dissolved RDX has been shown to undergo a series of reductive transformations under sufficiently reduced conditions in soil, yet surface soils are generally well aerated and become wet only ephemerally. As such, surface soils on ranges can serve as an RDX source from which surface and subsurface waters become contaminated. A potential treatment technology ties together phytoremediation and photodegradation in the plant tissue and humification of plant tissue-associated RDX residues that return to the soil following plant senescence.
This project will improve the understanding of RDX transformation in plant tissues and the subsequent cycling of tissue-associated RDX and daughter products among soil mineral and humic fractions following plant senescence.
This project will evaluate the following three combined approaches for the removal and degradation of RDX in contaminated soils: (1) plant uptake and removal; (2) accumulation, phyto- and photo-degradation rates; and (3) humification. For plant uptake and removal, mint and related plants (family Labiatea), with their unique metabolic pathways, will be exposed to RDX and the plants examined to determine if these pathways can be utilized to facilitate the breakdown of RDX. There is also the option of selecting plants, both from the family Labiatea and other plants such as Coleus, that have relatively large unpigmented areas. For accumulation, phyto- and photo-degradation, pigmented and non-pigmented mint tissues, as well as tissues from variegated Coleus plants, will be examined to determine if the movement of RDX to a leaf tissue that exposes the contaminant to light at much higher levels than would be present in the soil or in pigmented tissue can lead to photodegradation of RDX. Finally, tissue from plants with high uptake rates will be incorporated into ongoing humification studies that are investigating the fate of plant tissue-associated RDX as plant tissue falls to soil. This three-tiered approach will cultivate the development of natural systems for the remediation of RDX that are sufficiently robust for widespread use on impact ranges and based on well-defined processes.
Results from this research will have wide-ranging implications for developing sound management strategies for range sustainability and, ultimately, reducing the cost of treating contaminated DoD sites. This project addresses fundamental mechanisms of interactions between plants, physical properties of the contaminant of interest, and soil components to better understand the mechanisms involved in RDX removal from the environment. (Anticipated Project Completion - 2010)
Points of Contact
Dr. Charles Reynolds
U.S. Army ERDC/CRREL
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