Relationship between Redox Potential and pH on RDX Transformation in Soil-Water Slurries

The presence of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in surface soil, the vadose zone, and ground water can present serious environmental problems. The processes governing the release and transformation of RDX into soils and the aquatic environment are not well understood. The objective of this study was to determine the effects of differing environmental conditions as reflected by redox potential and pH on the fate of RDX in soil. Laboratory investigations consisted of testing three redox potentials and four pH levels in an 18:1 (2,600 m3 water:150 g soil) suspension spiked with 10 mg/L RDX. Results indicated that RDX was unstable under highly reducing conditions (-150 mV) and relatively stable over the short term (15 days) under oxidizing and moderately reducing conditions at all pH values. RDX in areas of intense reduction would not persist. However, RDX deposited or moving into areas under moderately reducing or oxidizing conditions would be highly mobile and persistent.