SERDP 2016 Project-of-the-Year Award for Environmental Restoration
The explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are common munitions constituents. Both compounds and their derivatives are Environmental Protection Agency (EPA) priority pollutants and are persistent in the environment. Within the contiguous 48 United States, there are approximately 41 active DoD installations located within the coastal zone. Exposure of marine/estuarine ecosystems at some sites is well documented, while other installations have a high potential for exposure but limited data on RDX or TNT concentrations in marine receptors. Coastal habitats are highly productive, nitrogen-limited, and economically valuable ecosystems. Their response to munitions compounds and their effect on munitions cycling, persistence, bioaccumulation, and mineralization are largely unknown.
Dr. Craig Tobias from the University of Connecticut and his team led a SERDP funded project that quantified the pathways and rates of RDX and TNT processing at three typical coastal ecotypes: subtidal vegetated, subtidal unvegetated, and intertidal salt marsh. The team sought to understand the uptake rates of these compounds at the organismal to ecosystem scales, and which ecosystem components are important regulators of processing. In addition, the team investigated which ecosystem components act as zones of storage for munitions compounds versus those that promote metabolism, and whether ecosystem characteristics relate to processing or accumulation of munitions compounds. Finally, the team determined the extent wihch these compounds were mineralized to inert inorganic endproducts.
Study results have shown that TNT and RDX are processed in all ecotypes, and that while TNT loss is uniform across all sediment types, RDX loss is a function of organic matter content and redox conditions. The results also demonstrated that these parent munitions compounds and primary common derivatives are unlikely to persist in marine environments. The data from this study will provide a quantitative assessment of marine habitats as bioaccumulators or natural attenuators of munitions compounds.
For this significant work, Dr. Tobias and his team received the 2016 SERDP Project-of-the-Year Award for Environmental Restoration for their project titled Tracking the Uptake, Translocation, Cycling, and Metabolism of Munitions Compounds in Coastal Marine Ecosystems Using Stable Isotopic Tracer.