Degradation of Metal−Nitrilotriacetate Complexes by Chelatobacter heintzii

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- >...