Technical Approach

The following hypotheses will be tested in this project:

1. Ferrous iron, as adsorbed ferrous iron or in the mineral phase magnetite, will directly reduce the nitro functional groups on DNAN and NTO.
2. Biological degradation of NTO and DNAN will proceed via a reductive pathway rather than an oxidative pathway.
3. Chemical transformation kinetics will be faster than biological transformation kinetics.
4. Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 2,4,6-trinitrotoluene (TNT) will inhibit NTO and DNAN reduction.
5. The primary reaction products of NTO and DNAN will be different based on chemical versus biological degradation pathways, with amine-group molecules (aniline) being the primary product during biological reduction and nitro-aryl-radicals being the primary product during chemical reduction.
6. Mixed biotic-abiotic reactions will degrade NTO and DNAN at rates that are at least double that of either individual mechanism alone.

To address hypotheses 1-3, researchers will quantify the kinetics and assess potential mechanisms of NTO and DNAN degradation in controlled batch systems using strictly chemical or strictly biological degradation mechanisms. Hypothesis 5 will be addressed by identifying the dominant reaction products of NTO and DNAN when degraded by biological versus chemical pathways. NTO and DNAN will first be investigated as the sole electron acceptor/contaminant; there will be no competing electron acceptors in the form of explosives or other molecules that are environmentally relevant (e.g., nitrate). To address hypothesis 4, competing electron acceptors such as RDX and HMX will be included in the batch systems. Hypothesis 6 will be addressed by identifying the influence of combined biological-abiotic reactions on NTO and DNAN degradation in the presence and absence of competing electron acceptors.