Laboratory Column Evaluation of High Explosives Attenuation in Grenade Range Soils

Area of Science:

• Environmental Science
• Soil Science
• Environmental Chemistry

Background:

• High explosives (HEs) deposited on military ranges pose a risk of soil and groundwater contamination.
• Understanding the transport and fate of HEs, such as 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), is crucial for remediation.
• The impact of soil characteristics and organic amendments on HE biodegradation requires further investigation.

Purpose of the Study:

• To examine the transport and fate of TNT and RDX in laboratory soil columns from military grenade bays.
• To evaluate the effectiveness of organic amendments (crude glycerin and lignosulfonate) in enhancing HE biodegradation.
• To assess the impact of amendments on the leaching of HEs and their degradation products.

Main Methods:

• Laboratory soil columns were established using soils from two hand grenade bays (Bays C and T).
• Experimental treatments included the addition of crude glycerin and lignosulfonate, alongside control columns.
• TNT and RDX concentrations, degradation products, and leaching were monitored under varying soil conditions (aerobic/anoxic, saturated/unsaturated).

Main Results:

• Extensive TNT degradation was observed with minimal leaching in all columns.
• Significant RDX biodegradation (64-77%) occurred in untreated soil columns, even with oxygen present, suggesting micro-niche anoxia.
• Amendment addition enhanced TNT degradation and increased RDX removal to over 92% in saturated columns and over 86% in unsaturated columns, substantially reducing RDX leaching.

Conclusions:

• RDX biodegradation can occur in soils with measurable oxygen, likely facilitated by transient anoxic conditions or micro-niches.
• Organic amendment addition effectively stimulates anaerobic biodegradation of RDX, significantly reducing its leaching potential.
• These findings demonstrate a viable strategy for mitigating explosive contamination in military range soils.