Date of Completion
Dr. Craig Tobias
Dr. Penny Vlahos
Dr. Kevin Brown
Field of Study
Doctor of Philosophy
2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5 (RDX) have been used extensively by the world’s militaries for more than a century. Millions of tons of these compounds have been released into marine environments globally. Contamination levels and biological accumulation of TNT and RDX in marine systems from both legacy and new environmental exposures are neither well documented nor understood.
TNT and RDX synthesized with a stable nitrogen isotope (15N) label were used to trace the uptake, biotransformation, and retention of, both parent compounds, their primary organic derivatives, and associated nitrogen-containing breakdown products in coastal marine biota. The experimental approach consisted of single species dose exposures, multi-species interactive steady state experiments, and cross ecosystem comparisons.
First order modeling of tissue RDX and 15N concentrations revealed high rates of uptake offset by rapid elimination and redistribution of tracer into bulk biomass. Tissue 15N levels varied by a factor of 8 between species in the same habitat, and were similar among the same species across different habitats. For all biota, the tissue 15N tracer concentrations associated with intact RDX were 10-fold lower than the total 15N measured in bulk biomass indicating that the majority of the RDX uptake was biotransformed internally. Four different biotransformation pathways were proposed to explain the observed patterns of 15N retention. Some of these pathways may indicate that some organisms could be using N released from RDX as a nutrient (e.g. macroalgae), while other pathways consist of accumulation of unknown organic N containing derivatives or adducts that may have further toxicity.
The use of the 15N tracer provided the ability to measure munitions biotransformation more completely than previously possible. It revealed that that marine biota take up more TNT and RDX than previously thought, and retain more breakdown products in largely as yet unidentified forms. This discovery raises new questions about the long term impact of post uptake biotransformation products on coastal marine biota.
Ballentine, Mark L., "Coastal Ecosystem Processing of Nitrogen Rich High Explosives" (2017). Doctoral Dissertations. 1362.