Hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX), 2,4,6 Trinitrotoluene (TNT) and octahydro-l,3,5,7- tetranitro-1 ,3,5,7 tetrazocine (HMX) are explosives widely used by the U.S. military. Past handling practices at facilities manufacturing, processing and disposing of explosives have, in many cases, resulted in environmental contamination. Leaching of these energetics into soil and groundwater from disposal lagoons has occurred at many sites in the U.S. and abroad. These explosives are susceptible to biological degradation under aerobic and anaerobic conditions. Anaerobic in-situ treatment requires just the addition of an electron donor. Work completed to date suggests that RDX and TNT serve as the electron acceptor under anaerobic conditions. The rates of degradation are, therefore, closer to metabolic rather than co-metabolic. This translates to the potential for rapid and complete degradation of the RDX, TNT and HMX. The overall goal of this proposed effort is to develop an understanding of what factors significantly influence the rate and extent of anaerobic transformation of TNT, RDX and HMX in groundwater-soil systems including 1) the best electron donor sources for rapid transformation of TNT, RDX and HMX and what intermediate products are formed, 2) what microbial populations are involved and 3) what are the effects of electron acceptors (i.e., SO4=~ NO3~) typically found in groundwater.
Benefits: Our team's knowledge of the microbial populations and factors that can affect the that degradation of these compounds in the subsurface environment and how to manipulate this capability to achieve rapid and complete degradation is, however, not sufficient at this time to confidently design and operate in-situ groundwater treatment systems. This proposed effort is designed to elucidate fundamental appreciation of factors that affect the rate and extent of treatment of explosives in groundwater.
