title: Biodegradation and mineralization of isotopically labeled TNT and RDX in anaerobic marine sediments.
abstract: The lack of knowledge on the fate of explosive compounds 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), particularly in marine ecosystems, constrains the application of bioremediation techniques in explosive-contaminated coastal sites. The authors present a comparative study on anaerobic biodegradation and mineralization of15N-nitro group isotopically labeled TNT and RDX in organic carbon-rich, fine-grained marine sediment with native microbial assemblages. Separate sediment slurry experiments were carried out for TNT and RDX at 23°C for 16 d. Dissolved and sediment-sorbed fractions of parent and transformation products, isotopic compositions of sediment, and mineralization products of the dissolved inorganic N pool (15NH4+,15NO3-,15NO2-, and15N2) were measured. The rate of TNT removal from the aqueous phase was faster (0.75 h-1) than that of RDX (0.37 h-1), and15N accumulation in sediment was higher in the TNT (13%) than the RDX (2%) microcosms. Mono-amino-dinitrotoluenes were identified as intermediate biodegradation products of TNT. Two percent of the total spiked TNT-N is mineralized to dissolved inorganic N through 2 different pathways: denitration as well as deamination and formation of NH4+, facilitated by iron and sulfate reducing bacteria in the sediments. The majority of the spiked TNT-N (85%) is in unidentified pools by day 16. Hexahydro-1,3,5-trinitro-1,3,5-triazine (10%) biodegrades to nitroso derivatives, whereas 13% of RDX-N in nitro groups is mineralized to dissolved inorganic N anaerobically by the end of the experiment. The primary identified mineralization end product of RDX (40%) is NH4+, generated through either deamination or mono-denitration, followed by ring breakdown. A reasonable production of N2gas (13%) was seen in the RDX system but not in the TNT system. Sixty-eight percent of the total spiked RDX-N is in an unidentified pool by day 16 and may include unquantified mineralization products dissolved in water. Environ Toxicol Chem 2017;36:1170-1180. © 2016 SETAC.
authors: Department of Marine Sciences, University of Connecticut, Groton, Connecticut, USA.
authors: Thivanka
authors: T
authors: Ariyarathna
authors: Department of Marine Sciences, University of Connecticut, Groton, Connecticut, USA.
authors: Penny
authors: P
authors: Vlahos
authors: Global Aquatic Research, Sodus, New York, New York, USA.
authors: Richard W
authors: RW
authors: Smith
authors: Naval Air Warfare Center Weapons Division, Chemistry Division, China Lake, California, USA.
authors: Stephen
authors: S
authors: Fallis
authors: Naval Air Warfare Center Weapons Division, Chemistry Division, China Lake, California, USA.
authors: Thomas
authors: T
authors: Groshens
authors: Department of Marine Sciences, University of Connecticut, Groton, Connecticut, USA.
authors: Craig
authors: C
authors: Tobias
mesh_terms: D001673:Biodegradation, Environmental; D053834:Explosive Agents / Q000737:chemistry / Q000378:metabolism*; D019015:Geologic Sediments / Q000737:chemistry*; D007553:Isotope Labeling; D009587:Nitrogen Isotopes / Q000737:chemistry; D025341:Principal Component Analysis; D014227:Triazines / Q000737:chemistry / Q000378:metabolism*; D014303:Trinitrotoluene / Q000737:chemistry / Q000378:metabolism*; D014867:Water / Q000737:chemistry
chemical_list: D053834:Explosive Agents; D009587:Nitrogen Isotopes; D014227:Triazines; D014867:Water; D014303:Trinitrotoluene; C009160:cyclonite
keywords: 15N isotopically labeled; 2,4,6-Trinitrotoluene; Anaerobic biodegradation; Hexahydro-1,3,5-trinitro-1,3,5-triazine; Marine sediment