The fate of the cyclic nitramine explosive RDX in natural soil

The sorption-desorption behavior and long-term fate of hexahydro-1,3,5-trin itro-1,3,5-triazine (RDX) was examined in sterilized and-nonsterilized tops oil. Results of this study indicate that although RDX is not extensively so rbed by;the topsoil (K-d(S) of 0.83 L/kg), sorption is nearly irreversible. Furthermore, there was no difference in the sorption behavior far sterile and nonsterile topsoil. However, over the long-term, RDX completely disappe ared within 5 weeks in nonsterile topsoil, and hexahydro-1-nitroso-3,5-dini tro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (D NX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) metabolites formed in the aqueous phase. Dyer I the same period, recovery of RDX from sterile topsoil was high (55-99%), and the nitroso metabolites were not detected. Only traces of RDX were mineralized to CO2 and N2O by the indigenous microo rganisms in nonsterile topsoil. Of the RDX that was mineralized to N2O, one N originated from the ring and the other from the nitro group substituent as determined using N-15 ring-labeled RDX. However, N2O from RDX represente d only 3% of the total N2O that formed from the process of nitrification/ d enitrification.