Soils amended with [14C]hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) were sampled over 60 d and subjected to exhaustive Soxhlet extraction followed by HPLC analysis. RDX was the only radiolabeled compound observed in soil extracts. Emission of volatile organics and 14CO2 from soil accounted for only 0.31% of the amended radiolabel. Mass balance for RDX‐amended soil was better than 84% throughout the two‐month study. The analytical method developed for plants involved acid hydrolysis, solvent extraction, fractionation on Florisil® adsorbent and separation by HPLC. The described methodology allowed for RDX recovery of 86 ± 3% from fortified bush bean leaf tissue. Further experiments were conducted with bush bean plants maintained on RDX‐containing hydroponic solutions. Hydroponic plants did not emit detectable amounts of 14CO2 or radiolabeled volatile organics. Analysis of the plant tissue indicated bioaccumulation of RDX in the aerial tissues of hydroponic plants exposed for either 1 or 7 d. Metabolism of RDX to polar metabolites was observed in plants exposed for 7 d.

The findings of this report are not to be construed as official Department of the Army positions unless so designated by other authorized documents DISClAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes .tny wMr.Jnty, expressed or implied, or assumes .tny legal liability or responsibility for the accur.tcy, completeness, or usefulness of .1ny information, apparatus, product, or process disclosed, or represents th.tt its use would not infringe printely owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government of any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Nitrilotriacetic acid (NTA) is a synthetic chelating agent that can form strong water-soluble complexes with a wide range of radionuclide and metal ions and has been used to decontaminate nuclear reactors and in the processing of nuclear materials. The co-disposal of NTA or other synthetic chelating agents with radionuclides may result in increased dispersal of radionuclides in soil and subsurface environments. Understanding the influence of aqueous geochemistry on NTA degradation is essential to predict the mobility and fate of inorganic contaminant−NTA complexes in the subsurface. Chelatobacter heintzii (ATCC 29600) was shown to degrade 14C-labeled NTA to 14CO2 with first-order kinetics at concentrations ranging from 0.05 to 5.23 μM (0.01−1 μg of NTA mL-1). The degradation of various metal−NTA complexes was investigated under conditions in which the NTA was predominantly present as the metal−NTA complex. The order for the rates of degradation was HNTA2- > CoNTA- = FeOHNTA- = ZnNTA- > AlOHNTA- > CuNTA- > NiNTA-, which is not related to the order of metal−NTA stability constants. The metal concentration used was not inhibitory to glucose mineralization, suggesting that toxicity of the chelated metal was not responsible for the differences in the rates of NTA degradation. After degradation of CoNTA- and NiNTA-, <3% of the Co or Ni was associated with C. heintzii cells. This indicates that, after degradation of the metal−NTA complex, metal ions will be predominantly present in the aqueous phase. The degradability of the various metal−NTA complexes was not related to their thermodynamic stability constants, but was related to the lability of the various metal−NTA complexes or the relative rates of formation of HNTA2-.

No abstract