Natural and Enhanced Attenuation of Explosives on a Hand Grenade Range

2,4,6‐Trinitrotoluene (TNT) and hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (Royal Demolition Explosive, or RDX) deposited on hand grenade training ranges can leach through the soil and impact shallow groundwater. A 27‐mo field monitoring project was conducted to evaluate the transport and attenuation of high explosives in variably saturated soils at an active grenade range located at Fort Bragg, NC. Two approaches were evaluated: (i) natural attenuation in grenade Bay C; and (ii) enhanced attenuation in Grenade Bay T. There was no evidence of TNT accumulation or leaching in surface soils or pore water in either bay, consistent with parallel laboratory studies showing aerobic and anaerobic biodegradation of TNT. In the untreated Bay C, the low saturated hydraulic conductivity (Ksat) combined with high rainfall and warm summer temperatures resulted in reducing conditions (low oxidation–reduction potential), an increase in dissolved Mn, and a rapid decline in nitrate and RDX. In Bay T, the somewhat greater Ksat and lower soil organic C level resulted in more oxidizing conditions with greater RDX leaching. A single‐spray application of glycerin and lignosulfonate to the soil surface in Bay T was effective in generating reducing conditions and stimulating RDX biodegradation for ∼1 yr.Core Ideas There was no evidence of TNT accumulation or leaching. Large spatial variations in drainage rates occurred due to grenade detonation craters. Small differences in soil properties generated important differences in redox conditions. RDX was depleted when soil Eh declined. Amendment addition generated reducing conditions, stimulating RDX biodegradation.