Effects of oxidant and catalyst on the transformation products of rocket fuel 1,1-dimethylhydrazine in water and soil

Existing methods for cleanup of wastewaters and soils polluted with the extremely toxic rocket fuel unsymmetrical dimethylhydrazine (UDMH) are mainly based on the treatment with various oxidative reagents. Until now, the assessment of their effectiveness was based on the residual content of UDMH and did not take into account the possibility of the formation of a large number of potentially dangerous nitrogen-containing transformation products (TPs). In this study, using the recently developed approach based on high-resolution Orbitrap mass spectrometry, the comprehensive characterization of UDMH TPs formed by the action of air oxygen and different oxidants (Fenton's reagent, KMnO4, HOCl, H2O2 in the presence of Cu2+ and [Fe (EDTA)]- catalysts) typically used to detoxify spill sites was performed. The range of the identified molecular formulas of TPs comprised 303 compounds of various classes. Among them, there is a number of major products not previously described in the literature. It was established that none of the investigated oxidative reagents ensures complete conversion of rocket fuel to safe compounds. The hydrogen peroxide based reagents, particularly H2O2 + Na [Fe (EDTA)] system currently used in Kazakhstan, give the greatest number of TPs, for many of which a toxicity was not characterized so far. The majority of the compounds found in model solutions was detected in extracts of soil from the crash site of the Proton carrier rocket, which was subjected to the on-site reagent treatment. During successive treatments, along with the decrease in the number of detectable UDMH TPs, their ratios change in favor of amines.