HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE (RDX) NATURAL ATTENUATION AND ACTIVE BIOREMEDIATION

RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is a widely–used high explosive compound which has been detected in soil and groundwater around military sites, at manufacturing and testing sites including Los Alamos National Laboratory. RDX has toxicological effects on the central nervous system, and the EPA has established a drinking water health advisory for RDX. Remediation strategies are being sought to reduce the risk of exposure to environmental receptors. In this study, we focused on identifying biotic and abiotic processes that contribute to the attenuation of RDX in groundwater at Technical Area 16 (TA-16) at Los Alamos National Laboratory, and to identify microbial signatures of RDX degradation in groundwater. We tested the potential use of OSORB® samplers available through ABS Materials Inc., (Wooster,OH) to concentrate RDX and its degradation products by deploying the samplers in monitoring wells completed in contaminated groundwater at TA-16. Our data indicate that under site-specific conditions at LANL, the OSORB® samplers multiplied RDX concentrations observed in groundwater by a factor of 10. We also observed that the ratio of MNX/RDX concentration was higher in OSORB® samplers relative to values obtained by directly analyzing the water, suggesting that the OSORB® samplers may be a more conservative approach for sampling RDX degradation products. A second series of field tests was conducted at TA-16 by deploying the OSORB® samplers in the shallow and deeper groundwater for a relatively-long period of 3 months. Data from the second deployment showed that RDX degradation is presently occurring, but at a very slow rate. Biostimulation column tests were conducted in the laboratory to identify nutrients and microorganisms that could enhance RDX degradation. The results demonstrated that vegetable oil promotes RDX degradation under anaerobic conditions. The results of this study expand our current understanding of the natural attenuation of RDX, the nutrient requirements for biodegradation, and the microbial ecology in RDX-contaminated groundwater at TA-16. The results provide valuable information regarding the importance of key nutrients and microbes in the biodegradation process.