Degradation of RDX, TNT, and HMX during EPA 8330B Sample Processing and Analysis of Soils under Hydrated Lime or Dithionite-Based Chemical Remediation

The remediation efficiency of soils containing energetic materials (EM) is assessed using SW-846 USEPA Method 8330B. However, the extraction, which is performed by sonicating the soil samples in acetonitrile for several hours, could lead to additional degradation of EM during sample processing, and consequently, to an overestimation of remediation efficiency. To verify this, soil samples that were spiked with controlled amounts of EM were briefly exposed to remediation reagents, such as MuniRem® (a commercial sodium dithionite-based formulation) or hydrated lime, and analyzed using SW-846 USEPA Method 8330B. The most affected EM of this study was 2,4,6-trinitrotoluene (TNT), for which complete degradation was observed after exposure to hydrated lime or pH-buffered MuniRem®. Losses of 1,3,5-trinitro-1,3,5-triazinane (RDX) reached 30 ± 20% upon treatment with full pH-buffered MuniRem® and 90 ± 10% when exposed to lime. The concentrations of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were near the method’s lower limit of quantification, and subjected to large errors, which prevented us from drawing any clear conclusions regarding its degradation under the studied experimental conditions. These results highlight the necessity of performing appropriate soil sample treatments to quench the remaining hydrated lime or sodium dithionite prior to the extraction and analysis steps with SW-846 USEPA Method 8330B. Quenching of remaining remediation reagents may possibly be also required for other remediation reagents and EM.